ROBSON ROSA DA SILVA New photonic structures: I – Self assembly of 1D Te structures; II – Multifunctional biopolymers and reused plastics. Novas estruturas fotônicas: I – Auto-organização de estruturas 1D de Te; II – Biopolímeros e plásticos reutilizados multifuncionais. A thesis submitted to the Institute of Chemistry, São Paulo State University, in partial fulfillment of the requirements for the degree of Doctor in Chemistry. Supervisor: Dr. Sidney J. L. Ribeiro Co-supervisor: Dr. Pedro H. C. Camargo Araraquara 2016 CATALOGUING DATA Silva, Robson Rosa da S586n New photonic structures: I - Self assembly of 1D Te structures; II - Multifunctional biopolymers and reused plastics = Novas estruturas fotônicas: I - Auto-organização de estruturas 1D de Te; II – Biopolímeros e plásticos reutilizados multifuncionais / Robson Rosa da Silva. – Araraquara: [s.n.], 2016 259 p.: il. Tese (doutorado) – Universidade Estadual Paulista, Instituto de Química Orientador: Sidney José Lima Ribeiro Coorientador: Pedro Henrique Cury Camargo 1. Telúrio. 2. Nanoestruturas. 3. Biopolímeros. 4. Plásticos. 5. Materiais óticos. I. Título. Elaboração: Seção Técnica de Aquisição e Tratamento da Informação Biblioteca do Instituto de Química, Unesp, câmpus de Araraquara CURRICULUM VITAE IDENTIFICATION Full name: Robson Rosa da Silva Name in scientific citations: Silva, R. R.; Silva, Robson Rosa da; Silva, Robson Rosa; Da Silva, Robson R.; Da Silva, Róbson Rosa; Silva, Robson R. Birth information: December 31st,1988. Nationality: Brazilian Birth city: Itauçu-GO Marital Status: Married Filiation: Doracilda Rodrigues da Silva, Baltazar Rosa da Silva Occupation: Chemist PROFESSIONAL ADDRESS 1234 Paulino Rodella Av, APT 302 BL 04, Jardim das Flores, Araraquara-SP, ZIP 14801-788 FORMAL EDUCATION 2012: Master's degree in Chemistry. São Paulo State University, UNESP, São Paulo-Brazil Supervisor: Prof. Dr. Sidney José Lima Ribeiro 2009: Bachelor's degree in Chemistry Universidade Federal de Goiás, UFG, Goiânia-Brazil PUBLICATIONS IN SCIENTIFIC JOURNALS Published papers Silva, R.R.; Salvi, D. T. B.; Santos, M. V.; Barud, H. S.; Marques, L. F.; Santagneli, S. H. Tercjak, A.; Ribeiro, S. J. L. Multifunctional organic-inorganic hybrids based on cellulose acetate and 3-glycidoxypropyltrimethoxysilane. Journal of Sol-Gel Science and Technology. 2016, in press. doi: 10.1007/s10971-016-4089-x Silva, R. R.; Mejia, A. H. G.; Ribeiro, S.J.L.; Shrestha, L. K.; Ariga, K.; Oliveira Jr., O. N.; Camargo, V. R.; Maia, L. J. Q.; Araujo, C. B. Facile synthesis of tellurium nanowires and study of their third-order nonlinear optical properties. Journal of Brazilian Chemistry Society, 2016, in press. doi: 10.5935/0103-5053.20160145. Pinto, E. R. P.; Barud, H. S.; Silva, R. R.; Polito, W. L.; Calil, Vanessa L.; Cremona, M.; Ribeiro, S. J. L.; Messaddeq, Y. Transparent composites prepared by bacterial cellulose and castor oil based polyurethane as substrate for flexible OLEDs. Journal Materials Chemistry C, v. 3, p.11581-11588, 2015 (cover). M. Luo, H. Huang, S.-I. Choi, C. Zhang, R. R. da Silva, H.-C. Peng, Z.-Y. Li, J. Liu, Z. He and Y. Xia. Facile synthesis of Ag nanowires with no plasmon resonance peak in the visible region by using Pd decahedra of 16 nm in size as seeds. ACS Nano, v. 9, p. 10523-10532, 2015. Tireli, A. A.; Guimarães, I. R.; Terra, J. C. S.; Silva, R. R. ; Guerreiro, M. C. Fenton-like processes and adsorption using iron oxide-pillared clay with magnetic properties for organic compound mitigation. Environmental Science and Pollution Research. v. 22, p. 870-881, 2015. Nigoghossian, K.; Santos, M. V. ; Barud, H. S.; Silva, R. R. ; Rocha, L. A.; Caiut, J. M. A. ; Assunção, R. M.N. ; Spanhel, L.; Poulain, M.; Messaddeq, Y. ; Ribeiro, S. J. L. Orange pectin mediated growth and stability of aqueous gold and silver nanocolloids. Applied Surface Science, v. 341, p. 28-36, 2015. Moraes, M. L.; Lima, L. R.; Silva, R. R.; Cavicchioli, M.; Ribeiro, S. J. L. Immunosensor based on immobilization of antigenic peptide NS5A-1 from HCV and silk fibroin in nanostructured films. Langmuir, v. 29, p. 130221130155006-3834, 2013. Silva, R. R.; Dominguez, C. T.; Santos, M. V.; Barbosa-Silva, R.; Cavicchioli, M.; Christovan, L. M. ; De Melo, L. S. A. ; Gomes, A. S. L.; Araújo, C. B.; Ribeiro, S. J. L. Silk fibroin biopolymer films as efficient hosts for DFB laser operation. Journal Materials Chemistry C, v. 1, p. 7181, 2013. Marques, L. F.; Corrêa, C. C.; Silva, R. R.; Santos, M. V.; Ribeiro, S. J. L.; Machado, F. C. Structure, characterization and near-infrared emission of a novel 6-connected uninodal 3D network of Nd(III) containing 2,5-thiophenedicarboxylate anion. Inorganic Chemistry Communication, v. 37, p. 66-70, 2013. Marques, L. F.; Cantarut Jr., A. A. B. I; Correa, C. C.; Lahoud, M. G.; Silva, R. R.; Ribeiro, S. J. L.; Machado, F. C. First crystal structures of lanthanide-hydrocinnamate complexes: hydrothermal synthesis and photophysical studies. Journal Photochemistry Photobiology A., v. 252, p. 69-76, 2012. Silva, R. R., Alves, O. L.; Gomes, D. C. C. Síntese e estudo da condutividade em hexaazomacrocíclicos de cobalto (II) com ligantes aromáticos. Enciclopédia biosfera, v.6, 2010. Accepted articles for publication. Barud, H. G. O.; Barud, H. S.; Silva, R. R.; Tercjak, A.; Lustri, W. R.; Oliveira Junior, O. B.; Ribeiro, S. J. L. A multipurpose natural and renewable polymer: bacterial cellulose in medical applications. Carbohydrate Polymers. 2016 (accepted). Patents Qin, D.; Xia, Y.; Yang, Y.; Li, J.; Sun, X.; Silva, R. R.; Yang, M. Silver nanowires, methods of making silver nanowires, core-shell nanostructures, methods of making core-shell nanostructures, core-frame nanostructures, methods of making core-frame nanostructures. US20160082418 Silva, R. R.; Maturi, F. E.; Barud, H. S. Ribeiro, S. J. L. Process for obtaining transparent and flexible composites based on expanded polystyrene disposal and bacterial cellulose. Disclosure ID: 15CI045 (accepted) Amaral, T. S.; Barud, H. S.; Silva, R. R.; Ribeiro, S. J. L. Production of ZnO nanowires from bacterial cellulose. Disclosure ID: 15CI074 (accepted) Book chapters Ribeiro, S. J.L.; Santos, M. V.; Silva, R. R.; Pecoraro, E.; Gonçalves, R. R.; Caiut, J. M. A. The sol-Gel handbook: synthesis, characterization and applications. Wiley-VCH Verlag GmbH & Co. KGaA, v. 3, chap. 30, 2015. Publication of extended abstract at international events Silva, R. R.; Dominguez, C. T.; Santos, M. V.; Cavicchioli, M.; Barbosa-Silva, R.; Christovam, L. M.; Melo, L. S. A.; Ribeiro, S. J. L.; Araujo, C. B.; Gomes, A. S. L. Efficient distributed feedback dye laser in silk fibroin films. Conference on Lasers and Electro-Optics, San Jose-United States, 2012. Publication & poster presentation of extended abstract in national events Silva, R. R.; Maia, L. J. Q.; Ribeiro, S. J. L. Preparation and study of 1D multifunctional composites. In: 34th Annual Meeting of the Brazilian Chemical Society - International Year of Chemistry - 2011: Chemistry for a better world, Florianópolis-Brazil, in 2011. Silva, R. R.; Ribeiro, S. J. L. Preparation of magneto-luminescent nanomaterials based on 1D nanostructures of tellurium. In: XIX XIX Journey of Young Scientists of the Association of Grupo Montevideo Universities - Science in the bicentennial of Latin American peoples, Ciudad del Este-Paraguay, 2011. Silva, R. R.; Alves, L. O.; Cangussú, D. Synthesis and conductivity study of cobalt (III) hexaazomacrocycles with aromatic ligands. In: Scientific Initiation Seminar VII and IV Jornada Research and Graduate Studies, State University of Goiás - Scientific Initiation Seminar VII and IV Journey of Research and Graduate UEG, Anapolis-Brazil, 2009. Silva, R. R.; Foggia, M. P. S. A.; Sartoratto, P. P. C. Coating of maghemite nanoparticles with amphiphilic polymer. In: VI Congress of Research, Education and Extension (CONPEEX) - VI Congress of Research, Teaching and Extension, Federal University of Goiás, Goiânia- Brazil, 2009. p.8528-8533. Sartoratto, P. P. C.; Silva, R. R.; Foggia, M. P. S. A. Functionalisation of nanoparticles maghemite bilayers with long-chain carboxylic acids. In: VI Congress of Research, Teaching and Extension (CONPEEX) - VI Congress of Research, Teaching and Extension-Research, Goiania-Brazil, 2009. p.8452-8456. Silva, R. R.; Alves, L. O.; Gomes, D. C. C. Synthesis and conductivity study of cobalt (III) hexaazomacrocycles with aromatic ligands. In: 49th Brazilian Congress of Chemistry (CBQ) - XLIX Brazilian Congress of Chemistry: Chemistry and Sustainability, Proceedings, Porto Alegre-Brazil, 2009. Silva, R. R.; Bermudez, V. C. Z. Thermal and spectroscopic study of linear polyethyleneimine /calcium triflate system. In: 49th Brazilian Congress of Chemistry (CBQ) - XLIX Brazilian Congress of Chemistry: Chemistry and Sustainability, Proceedings, Porto Alegre-Brazil, 2009. Silva, R. R.; Sartoratto, P. P. C.; Caiado, K. L. Preparation of maghemite-silica nanocomposites. In: 15th Workshop on the Scientific Initiation - Proceedings / Abstracts of the 60th Annual Meeting of the Brazilian Society for the Advancement of Science, Campinas- Brazil, in 2008. Silva, R. R.; Sartoratto, P. P. C. Preparation and study of magneto-optical properties of nanocomposites based on silica-maghemite. In: 4th Congress of Research, Teaching and Extension - Science, Education and Social Commitment, Goiânia- Brazil, 2007. p.1175-1178. Abstract publications & poster presentation at international events Silva, R. R.; Dominguez, C. T.; Santos, M. V.; Cavicchioli, M.; Barbosa-Silva, R.; Christovam, L. M.; Melo, L. S. A.; Ribeiro, S. J. L.; Gomes, A. S. L.; Araujo, C. B. Silk fibroin biopolymer films as efficient hosts for DFB Laser and Random Laser operation. 3rd International Conference on Multifunctional, Hybrid and Nanomaterials, Sorrento-Italy, 2013. Silva, R. R.; Duarte, A.P.; Gressier, M.; Menu, M. J.; Dexpert-Ghys, J. Caiut, J. M., Franco Júnior, A. Ribeiro, S. J. L. Magneto-luminescent particles. [Eu(tta)3(Bpy-Si)] modified Fe2O3@SiO2 particles. 3rd International Conference on Multifunctional, Hybrid and Nanomaterials, Sorrento-Italy, 2013. Barud, H. S.; Santos, M. V.; Santos, D. B.; Lima , L. R.; Silva, R. R.; Júnior, A. M. A.; Leite, R.; Saska, S.; Cavicchioli , M.; Messaddeq, Y.; Ribeiro, S. J. L. Multifunctional nanomaterials based on bacterial cellulose. 7th International Symposium on Advanced Materials and Nanostructures. Sorocaba-Brazil, 2012 Silva, R. R.; Ribeiro, S. J. L. Preparation of magneto-luminescent nanomaterials based on 1D nanostructures of tellurium. In: XIX XIX Journey of Young Scientists of the Association of Grupo Montevideo Universities - Science in the bicentennial of Latin American peoples, Ciudad del Este-Paraguay, 2011. Ribeiro, S. J. L.; Silva, R. R.; Vorpagel, A. J.; Santos, M. V.; Santos, D. B.; Cavicchioli, M.; Christovam, L. M. Multifunctional organic-inorganic hybrids based on biocellulose, fibroin membranes and vegetable oils. In: XIV International Sol-Gel Conference - XIV International Sol-Gel Conference, Hangzhou-China, 2011. Abstract publications & poster presentations in national events Silva, R. R.; Barud, H. S., Maia, L. J. Q.; Ribeiro, S. J. L. Growth of one-dimensional tellurium nanostructures in bacterial cellulose. In: 34th Annual Meeting of the Brazilian Chemical Society - International Year of Chemistry - 2011: Chemistry for a better world, Florianópolis-Brazil, 2011. Silva, R. R.; Foggia, M. P. S. A.; Sartoratto, P. P. C. Preparation and characterization of colloidal suspensions of maghemite/ Pluronic. In: 33th Annual Meeting of the Brazilian Chemical Society, Águas de Lindóia-Brazil, 2010. Silva, R. R.; Sartoratto, P. P. C. Preparation of silica maghemite monoliths. In: 31st Annual Meeting of the Brazilian Chemical Society, Águas de Lindóia-Brazil, 2008. Projects in e-learning chemistry education 2011-2/ 2012-1: Use of information technology and communication in the graduate discipline of Oleochemistry. Coordinator: Prof. Dr. Sidney José Lima Ribeiro; Financial Aid: Pro-rector of Graduate Studies (PROPG)-UNESP 2013-1/2014-1: Use of information and communication tools (ICT) in the ‘special topics’ discipline: Advanced Materials for Photonic Applications and stimulus actions to internationalization of the Post-Graduate Program in Chemistry (www.sampaproject.com). Coordinator: Prof. Dr. Sidney José Lima Ribeiro; Financial Aid: PROPG-UNESP. Function: e-tutor and web designer. International experience 1) Georgia Institute of Technology Atlanta, Georgia, United States Supervision: Dr. Younan Xia Project: a) Synthesis of ultrathin silver nanowires for photonic application, b) Synthesis of photonic crystals based on Au@Ag core-shell nanospheres, c) Preparation of magnetic- plasmonic nanoparticles based on the incorporation of magnetic nanoparticles into Au nanocages for biological application Duration: 03/2014 – 03/2015 2) National Institute of Materials Science Tsukuba, Ibaraki, Japan Supervision: Dr. Lok Kumar Shrestha, Dr. Katsuhiko Ariga Project: Preparation of multifunctional nanowires and nanotubes containing lanthanide ions based on 1D Te nanostructures as sacrificial template. Duration: 09/2013 – 10/2013 3) Tras-Os-Montes e Alto Douro University, Vila Real, Portugal Supervision: Dra. Verònica Zea Bermudez Fellowship Program Luso-Brazilian Santander Universities Project: Thermal and spectroscopic Properties of solid-state batteries. Duration: 09/2008 – 02/2009 International event production Ribeiro, S. J. L., Pecoraro, E., Caiut, J. M. A., Nalin, M., Santagnelli, S. H., Manzani, D., Silva, R. R., Oliveira, T. J., Silva, M. M. 1st Advanced School on Materials for Photonic Applications: Glasses, Optical Fibers and Sol-Gel Materials, Institute of Chemistry, São Paulo State University, Araraquara-SP-Brazil. 2012 SUPERVISION Student: Vanessa Rodrigues Camargo. Curso: Licenciatura em Química. Projeto: Estruturas unidimensionais de Te como suporte para preparação de materiais multifuncionais contendo íons lantanídeos. Student: Natália Mendes Sanches. Curso: Licenciatura em Química. Projeto: Preparação de filmes híbridos orgânico-inorgânicos baseados em fibroina e íons lantanídeos para aplicações em sensoriamento de pH por monitoramento de luminescência. Student: Fernando Eduardo Maturi. Curse: Licenciatura em Química; Project: Preparação de materiais fotônicos baseados em poliestireno expandido reciclado Student: Thais Rodrigues Arroio. Curse: Licenciatura em Química. Project: Microesferas de fibroína incorporadas com nanopartículas ferromagnéticas. DEDICATION This work is dedicated to the people that I care most: words are just not expressive enough. To my lovely wife Ranyella whose love is the greatest gift of my life and whose commitment, support and patience are true model for all. ACKNOWLEDGMENTS I ought to thank those that had a direct impact on my scholastic studies. First, the most gratitude to God for the gift of life and by always putting very special people along this track. I owe my advisor Sidney Ribeiro for his constant guidance. I am greatly indebted to him for the freedom extended to me and to engage my creativity as the same time. I am grateful that him long valuable resources and pushed me to work with high quality partner researchers whenever my dedication was lagging. I am very fortunate to have him as advisor, mentor and friend. His open-mindedness has greatly influenced my perception about scientific research. I would like to thank Prof. Pedro Camargo for their insightful comments on my PhD studies who leverage me to work in an area that interest me. It has been a pleasure and honor to work with highly talented mentors outside. I have had the fortune of working with Prof. Katsuhiko Ariga and his team under mentoring of Dr. Lok Shresthra at National Institute of Materials. I'd like to thank each and every one of the members of Ariga group. Though it is impossible for me to thank everyone individually, I sincerely appreciate them all. I've learned much both technically and personally. I would like to express my sincere appreciation to Prof. Younan Xia for giving me the opportunity to join his team at Georgia Institute of Technology. I greatly appreciate your patience and guidance during this time. His dedication, untiring approach towards research, boundless energy and ability to cut complex concepts to simpler ones are inspirational. Thank you to make me a better scientist. I would also thank Prof. Dong Qin for your kindness and encouraging words. I would like to express my deepest thanks to all past and present members of Prof. Younan Xia for their endless support. I am glad to have built essential friendship in Atlanta with dear Denna Cummings, Dr. Ping Lu, Dr. Sang-ll Choi,(and whole Korean soccer team that I used to play with), Dr. Xiaohu Xia and Dr. Hsi-Chieh Peng. I am extremely grateful to have the chance to meet Ming Luo, Xuan Yang, Jessica Shang and Xiyu Li. I don’t have words to thank you for your supportive Friday’s pool car to ‘buy foods’ (the most useful pretext to have a break and share the funniest time together). I could not forget to mention Legna Figueroa for her endless encouraging support together with Madeline Vara and Aleksey Ruditskiy. Thank you so much to give me joy and funny company for almost half year, office-mates. Sincere thanks go to all of my lab-mates, past and current, of the Laboratory of Photonics at Araraquara. I specially acknowledge my coworkers Vanessa Camargo, Fernando Maturi, Natalia Mendes, Daniela Vassalo, Livia Christovam, Luana Alves, Mariana Garcia, Lais Lima, Dr. Denise Bonemer, Dr. Maurício Cavicchioli, Dr. Silvia Santagneli, Dr. Adriana Duarte (UFMS) and Dr. Lippy Marques (UERJ) for helping me with the synthesis and characterization of materials throughout the years. I would like to express my sincere gratefulness to Leandro Carneiro, Rafael Miguel and Molíria dos Santos for willingness to help, their friendship and for making each day enjoyable. I would like to single out and thank Dr. Hernane Barud, for setting the example of scientist and friendship. My deepest appreciations go to my wife Ranyella Siqueira for her loving friendship, understanding, never ending support and for embracing my struggles as their own. Words will never ever express my gratitude for your help. I gratefully mention the encouragement and unlimited support from my family throughout my graduate career. Undoubtedly, I have the biggest fans in the whole universe standing me up and holding me strong. I would like thanks the financial support of the Brazilian agencies: Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES), and Fundação de Amparo à Ciência e Tecnologia do Estado de São Paulo (FAPESP) for the Grant No. 2013/12367-6. I also thank the following publishers for their kind permission to reproduce previously published text and figures: The Royal Chemistry Society and Springer Publishing. ABSTRACT One-dimensional Te nanostructures (Te1D) in the shape of whiskers, wires and helices were prepared by a facile one-pot synthesis in the presence of aqueous Pluronic® F68 solution at low temperatures (< 100 ºC) and ambient pressure. The shape of Te1D nanostructures could be manuvered according with the reaction kinectics. We evaluate some techniques to assemble Te1D nanostructures on the pursuit for complex nanoarchitectures. Bundles of Te nanowhiskers and nanowires were achieved by self-assembly in liquid-liquid interface or by drop-cast technique in Si/SiO2 substrates. 1D hybrid structures have been conceived by using Te1D nanostructures as sacrificial template to attach metallic nanoparticles or even produce metallic 1D nanostructures. For example, 1D hybrid nanostructures were easily prepared by decorating Te nanowires with Ag nanoparticles in aqueous solution of poly(vinylpyrrolidone). Au 1D nanostructures with nodular-like shape were prepared by galvanic displacement of Au3+ ions in a mixture of Te nanohelices, ascorbic acid and an aqueous solution of poly(vinylpyrrolidone). Furthermore, Te1D nanohelices were functionalized with a layer of resorcinol-formaldehyde resin at mild synthesis conditions. The RF resin allowed us to fashion an intermediate pathway to explore the deposition of optically active compounds like Tb3+ hydroxylcarbonate or Au nanoparticles. Seeking practical applications, these nanostructures should be hosted over rigid or flexible films possessing excellent optical properties. Pure natural polymers and epoxy sol- gel hybrids films were evaluated as potential host for luminophors. The fabrication of epoxy hybrids is based on the incorporation of 3-glycidoxypropyltrimethoxysiloxane on the homogenous solution of natural polymer with subsequent casting over flat surface. Particularly, flexible silk fibroin and cellulose acetate films and their derivative hybrids displayed excellent optical properties to host optically active compounds. For instance, red emitting Eu3+ compounds and fluorescent dyes were hosted on pure natural polymer and hybrid films and the optical features of the luminescent films were investigated thoroughly. Distributed feedback dye-lasers were fabricated by doping silk fibroin diffraction gratings with Rhodamine 6G. Owing its ability to mimic patterned surfaces at nanoscale resolution, dye-doped SF gratings were fabricated using replica-casting patterning against a commercial blank digital versatile disc as template. A modified DFB Laser based on SF films with Ag or SiO2 light scattering particles randomly distributed on the grating unveiled an enhancement of laser intensity withal narrowing of emission peak linewidth. Flexible and highly transparent SF- and CA-epoxy hybrids (> 85%) containing red fluorescent Eu3+ -diketonate complex and YVO4:Eu3+ nanoparticles at low relative content (< 5 wt%) were tailored. In general, the outcome is homogeneous films with epoxy and/or unhydrolized alkoxysilane functions available for further chemical modification. Owing the limited feedstock of natural polymers for high demanding production of optical devices, it is equally important develop materials based on the reuse of synthetic polymers. Thin films of polystyrene were conceived by dissolving waste-recovered expanded-polystyrene (EPS) in D-limonene, a green solvent from citrus oil. Transparent EPS films doped with Eu3+ -diketonate complex displayed excellent transparency and light waveguiding, These assertions provide a framework that motivates the research on a) engineering of 1D hybrids nanostructures with tunable optical properties and b) flexible natural polymer/epoxy hybrid with enhanced functionality or plastic recycled as potential optical hosts sought in photonic applications. Keywords: Tellurium. Phenol-formaldehyde resin. Hybrids. Lanthanide. Silk Fibroin, Cellulose Acetate, 3-glycidoxypropyltrimethoxysilane. Expanded polystyrene. D-limonene. RESUMO Nanoestruturas unidimensionais de telúrio (Te1D) na forma de whiskers, fios e hélices foram preparados com facilidade por uma síntese em etapa única na presença de solução aquosa de Pluronic® F68 à baixas temperaturas (< 100 °C) e pressão ambiente. A forma das nanoestruturas puderam ser controladas de acordo com a cinética da reação. Estruturas empacotadas de nanowhiskers e nanofios de Te foram obtidas via auto-organização em interface líquido-líquido e pela técnica de drop-cast em substrato de Si/SiO2. Estruturas híbridas 1D foram obtidas utilizando nanoestruturas Te1D como molde de sacrifício para anexar nanopartículas metálicas ou mesmo produzir nanoestruturas 1D metálicas. Por exemplo, nanoestruturas híbridas 1D foram preparadas decorando nanofios de Te com nanopartículas de Ag em solução aquosa de poli(vinilpirrolidona). Nanoestruturas 1D de Au com forma de nódulos foram preparados por deslocamento galvânico de íons Au3+ em uma mistura de nanohélices de Te, ácido ascórbico e solução aquosa de poli(vinilpirrolidona). Além disso, nanohélices de Te foram funcionalizadas com uma camada resina resorcinol-formaldeído em condições brandas de síntese. A resina de resorcinol-formaldeído é uma via intermédia para explorar a deposição de compostos opticamente ativos tais como nanopartículas de hidroxicarbonato de Tb3+ ou nanopartículas de Au. Para aplicações práticas é essencial que estas nanoestruturas possam ser suportadas em filmes rígidos ou flexíveis de alta qualidade óptica. Filmes de polímeros naturais puros e filmes híbridos de sol-gel epóxi foram avaliados como potenciais matrizes hospedeiras para luminóforos. A fabricação de híbridos é baseada na incorporação de 3-glicidoxipropiltrimetoxissilano na solução homogênea de polímero natural com posterior secagem sobre uma superfície plana. Particularmente, filmes flexíveis de fibroína da seda e acetato de celulose e os seus híbridos derivados exibiram excelentes propriedades ópticas para hospedar compostos opticamente ativos. Por exemplo, compostos de Eu3+ emissores na região do vermelho e corantes fluorescentes foram incorporados em matriz pura de polímero e híbridos epóxi e suas propriedades ópticas foram investigadas. Laser de corantes por feedback distribuído (DFB) foram fabricados dopando grades de difração de fibroína de seda com Rodamina 6G. Devido a sua capacidade de replicar superfícies padronizadas com resolução nanométrica, grades de fibroina da seda dopadas com corante foram depositadas contra a grade de difração de uma mídia de disco compacto comercial. Lasers modificados de DFB baseados em filmes de fibroina contendo nanopartículas espalhadoras de luz de SiO2 e Ag aleatoriamente distribuídas na grade de fibroina demonstraram aumento da intensidade do laser, além de estreitamento da largura do pico de emissão. Filmes híbridos flexíveis e transparentes (> 85%) de fibroina da seda e acetato de celulose modificados com função epóxi e contendo compostos fluorescentes na região do vermelho como complexos β-dicetonato de Eu3+ e nanopartículas de YVO4:Eu3+ em baixa proporção relativa mássica (<5%) foram preparados. De maneira geral, o resultado são filmes homogêneos com funções epoxi e/ou alcoxissilano não hidrolisados disponíveis para outras modificações químicas. Devido a matéria-prima limitada de polímeros naturais para uma alta demanda de fabricação de dispositivos ópticos, é igualmente importante desenvolver materiais com base na reutilização de polímeros sintéticos. Filmes finos de poliestireno foram concebidos por dissolução de poliestireno expandido (EPS) recuperado de resíduos em D-limoneno, um solvente verde proveniente de óleos cítricos. Filmes transparentes dopados com complexos β-dicetonato de Eu3+ demonstraram excelente transparência e aptos para uso em guias de luz. Estes resultados são motivadores para a) a engenharia de nanoestruturas 1D com propriedades ópticas sintonizáveis bem como, b) desenvolvimento de híbridos flexíveis e transparentes baseados em híbridos de polímeros naturais com alta funcionalidade química ou polímeros sintéticos reciclados como potenciais matrizes hospedeiras ópticas almejadas em aplicações fotônicas. Palavras-Chave: Telúrio. Resina resorcinol-formaldeído. Híbridos. Lantanídeos. Fibroina da seda. Acetato de celulose. 3-glicidoxipropiltrimetoxisilano. Poliestireno expandido. D- limoneno. SYMBOL TABLE ��→ � Apontaneous emission coefficients of 5D0 → 7FJ ��→ � Emission curve areas of 5D0 → 7FJ transitions �� Average transition energy in cm-1 ��→ � energy baricenters AA Ascorbic acid AFM Atomic force microscopy Anrad Non-radiative decay rate Arad Radiative decay rate ATR-FTIR Attenuated total reflection - Fast Fourier Transform Infrared Au1D One-dimensional nanostructures of gold BSE Back-scattered electrons CA Cellulose acetate CA-GPTMS Cellulose acetate/3-glycidyloxypropyltrimethoxysilane hybrids CP-MAS Cross Polarization Magic Angle Spinning CT Charge-transfer CTAB Cetyltrimethylammonium bromide CTAC Cetyltrimethylammonium chloride CW continuous wave Cβ β-carbon DED electric and magnetic dipole strength DED Magnetic dipole strength DFB Distributed feedback DSC Differential Scanning Calorimetry DTA Differential thermal analysis DVD Digital versatile disc EDS Energy-dispersive spectroscopy EDX Energy-dispersive X-ray Eg Band gap energy EPS Expanded polystyrene FCC Face centered cubic FEG-SEM Field Emission Gun - Scanning Electron Microscopy FFT Fast-Fourier Transform GPTMS Glycidoxypropyltrimethoxysilane Planck's Constant is divided by 2π HRTEM High-Resolution Transmission Electron Microscopy ls thickness scattering mean free path LSP Localized surface plasmons LSPR Localized surface plasmon resonance MTT Tetrazolium 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyl tetrazolium bromide). n Refractive index NPs Nanoparticles nw Number of water molecules OD Optical density PBS Phosphate buffer PS polystyrene PVP Poly(vynilpyrrolidone) RC Replica-casting RF Resorcinol-formaldehyde resin Rh6G Rhodamine 6G. RL Random laser SAED Selected area electron diffrraction SAXS Small angle X-ray diffraction SF Silk fibroin SF Silk fibroin SFAg Silk fibroin grating samples containing Ag nanoparticles SFGPTMS Silk fibroin/3-glycidyloxypropyl trimethoxysilane hybrids SFRod Silk fibroin doped with Rhodamine 6G SFSi Silk fibroin grating containing silica nanoparticles Te@Ag One-dimensional hybrid nanostructures of tellurium and silver Te@Au One-dimensional hybrid nanostructures of tellurium and gold Te@C One-dimensional tellurium nanostructures coated carbon shell Te@RF One-dimensional Te nanostructures covered with resorcinol- formaldehyde resin. Te@RF/Au One-dimensional Te nanostructures covered with resorcinol- formaldehyde resin with attached Au nanoparticles TeA Tellurium derivative nanostructures described in 3.1.1 TeB Tellurium derivative nanostructures described in 3.1.2 TEM Transmission Electron Microscopy TG Thermogravimetry TGA Thermogravimetric analysis TMS Tetramethylsilane Tn Silicon linked with n siloxane units Tonset Degradation onset temperature TPPM Two Pulse Phase Modulation tta Thenoyltrifluoroacetonate UV-vis Ultraviolet – visible w Thickness XRD X-ray diffraction η Quantum efficiency λem Emission wavelength λexc Excitation wavelength σs Scattering cross section τ Experimental emission lifetime τrad Radiative lifetime χ Lorentz local field correction term Ω Judd-Ofelt intensity parameters radiative � Velocity of light � Electronic charge � Angular frequency of the transition TABLE OF CONTENTS 1. STATE OF THE ART ....................................................................................... 25 1.1. Tellurium ............................................................................................................ 26 1.1.1. One-dimensional Te nanostructures .................................................................... 28 1.1.2. One-dimensional Te hybrids ................................................................................ 30 1.1.3. Te@C hybrid nanostructures ............................................................................... 31 1.1.4. Assembly of 1D Te derivative nanostructures ...................................................... 34 1.2. Biopolymers as flexible transparent substrates............................................... 35 1.2.1. Natural polymers for photonics ........................................................................... 36 1.2.2. Silk Fibroin ......................................................................................................... 41 1.3. Organic-inorganic hybrid.................................................................................. 44 2. OBJECTIVES AND THESIS ORGANIZATION .......................................... 48 3. STUDY OF THE SYNTHESIS TE NANOWHISKERS, NANOWIRES AND NANOHELICES AND FABRICATION OF TE@X 1D HYBRIDS (X = AG, AU OR RESORCINOL-FORMALDEHYDE RESIN) .................................. 52 3.2. Experimental Section ......................................................................................... 54 3.1.1. Standard synthesis of Te1D nanostructures in Pluronic® F68 ........................... 54 3.1.2. Scaling up the synthesis of Te1D nanostructures by twenty times. ...................... 54 3.1.3. Synthesis of 1D Te@Ag hybrid nanostructures ................................................... 55 3.1.5. Synthesis of 1D Te@resorcinol-formaldehyde (RF) nanocables......................... 56 3.1.6. Synthesis of Te@RF/X nanocomposites, with X= YVO4:Eu3+, Au nanospheres or Ag nanocubes ....................................................................................................... 56 3.1.6.1. Synthesis of YVO4:Eu3+ nanoparticles ................................................................ 56 3.1.6.2. Synthesis of Au nanospheres ................................................................................ 57 3.1.6.3. Synthesis of Ag nanocubes ................................................................................... 57 3.1.7. Preparation of 1D Te@RF/(LaCeTb)CO3OH nanostructures ............................ 58 3.1.8. Preparation of 1D Te@RF/Au nanostructures .................................................... 58 3.2. Results and discussion ....................................................................................... 58 3.2.1. Tellurium nanowhiskers and nanowires .............................................................. 58 3.2.2. Liquid-liquid-air interface (polar/apolar solvent) ............................................... 63 3.2.3. Self-assembly by drop casting method ................................................................. 64 3.2.5. Tellurium nanohelices .......................................................................................... 70 3.2.6. Te@Au hybrids nanostructures from Te nanohelices .......................................... 72 3.2.7. Te@resorcinol-formaldehyde (RF) core-shell nanocables from Te nanohelices 74 3.2.8. Synthesis of Te@RF hybrid materials.................................................................. 78 3.3. Conclusions ......................................................................................................... 87 4. SILK FIBROIN BIOPOLYMER FILMS AS EFFICIENT FLEXIBLE HOST FOR DISTRIBUTED FEEDBACK LASER ....................................... 93 4.1. Experimental Section ......................................................................................... 95 4.1.1. Extraction of silk fibroin ...................................................................................... 95 4.1.2. Preparation of silver nanoparticles ..................................................................... 96 4.1.3. Synthesis of silica nanoparticles .......................................................................... 96 4.1.4. Fabrication of DFB silk fibroin gratings ............................................................. 96 4.1.5. Characterization .................................................................................................. 97 4.1.6. Experimental setup for the lasing measurements ................................................ 97 4.2. Results and discussion ....................................................................................... 98 4.3. Conclusions ....................................................................................................... 110 5. FUNCTIONAL AND TRANSPARENT HYBRIDS BASED ON SILK FIBROIN AND 3-GLYCIDOXYPROPYLTRIMETHOXYSILANE ........ 115 5.1. Experimental section........................................................................................ 117 5.1.1. Materials ............................................................................................................ 117 5.1.2. Preparation of aqueous SF solution .................................................................. 117 5.1.3. Preparation of free-standing silk fibroin/3-glycidoxypropryltrimethoxysilane hybrid films ........................................................................................................ 117 5.1.4. Preparation of YVO4:Eu3+ nanoparticles .......................................................... 117 5.1.5. Preparation of luminescent silk fibroin/3-glycidyloxypropyl trimethoxysilane hybrid films ........................................................................................................ 118 5.1.6. Cytotoxicity assay .............................................................................................. 118 5.1.7. Instrumentation .................................................................................................. 119 5.2. Results and discussion ..................................................................................... 120 5.3. Conclusion......................................................................................................... 139 6. MULTIFUNCTIONAL ORGANIC-INORGANIC HYBRIDS BASED ON CELLULOSE ACETATE AND 3- GLYCIDOXYPROPYLTRIMETHOXYSILANE ....................................... 146 6.1. Experimental section........................................................................................ 148 6.1.1. Materials ............................................................................................................ 148 6.1.2. Synthesis of luminescent tris(2-thenoyltrifluoroacetonato)europium(III) dihydrate complex .............................................................................................. 148 6.1.3. Preparation of cellulose acetate/3-glycidoxypropyltrimethoxysilane hybrid films .................................................................................................................... 148 6.1.4. Preparation of luminescent cellulose acetate/3-glycidoxypropyltrimethoxysilane hybrid film. ......................................................................................................... 148 6.1.5. Instrumentation .................................................................................................. 149 6.2. Results and discussion ..................................................................................... 150 6.3. Conclusion......................................................................................................... 165 7. THIN FILMS BASED ON POLYSTYRENE WASTES RECOVERY FOR OPTICAL APPLICATIONS .......................................................................... 170 7.1. Experimental procedure .................................................................................. 171 7.1.1. Materials ............................................................................................................ 171 7.1.2. Synthesis of luminescent [Eu(tta)3(H2O)2] complex .......................................... 172 7.1.3. Fabrication of PS-Eu thin films by spin-coating ............................................... 172 7.1.4. Instrumentation .................................................................................................. 172 7.2. Results and discussion ..................................................................................... 173 7.3. Conclusions ....................................................................................................... 181 8. DISCUSSION ................................................................................................... 184 9. CONCLUSION................................................................................................. 190 25 1. STATE OF THE ART The size and shape in one-dimensional nanomaterials have attracted a great deal of interest due the dependent quantum confinement effects of the atoms in low dimensionality and the employing of their structural arrangement in new potential applications like building blocks (CHATTOPADHYAY; CHEN; CHEN, 2011; FANG et al., 2010). Currently, the most successful examples of one-dimensional nanostructures on both scientific and technological perspectives are carbon nanotubes (VOLDER et al, 2013), Si (DASGUPTA et al, 2014) and Ag nanowires (DINH et al, 2013). Further, 1D nanostructures are considered ideal model system for investigating the size and morphology dependence in optical, electrical, magnetic and mechanical properties. One-dimensional semiconductor nanostructures are efficient transporters of electrons and excitons and substantial efforts have been paid attention to the emergence of anisotropic electro/optical effects for applications like ultrafast all-optical switching devices (TATSUURA et al., 2003; ZHU et al., 2006) frequency converters (HAN et al., 2012), optical limiting or light-emitting diodes (KIM et al., 2012) and lasers (HUANG et al., 2001). The assembly of 1D materials is responsible by emergence of new anisotropic properties which the manipulation into complex and ordered architectures have attracted great interest for the development of sensors and photonics applications (LIM; LIM, 2013). Likewise, the addition of optical materials into nanostructured 1D array may be interesting for optical gain studies such as stimulated emission processes in the development of field emitter devices. 1D binary compounds based in organic dyes have been explored to study the wave guiding and lasing properties to enhance the performance of optical and optoelectronic devices (ZHANG et al., 2013). Intrinsic luminescent 1D nanostructures such as binary semiconductors (i.e ZnSe, CdS , CdSe, PbTe, CdTe etc.) or oxides (ZnO) have been extensively studied as a stand-alone optical cavity and gain medium for nanolasers applications. In particular, intense research has focused in lanthanide ions. The great interest in the study of nanoparticle systems combining compounds based on lanthanide ions is due to the variety of possible applications concerning their outstanding spectroscopic properties. In fact the sharp spiked emission spectra regarding from UV to the IR spectral range, relative long lifetimes of excited states (µs, ms), large Stokes shifts ( > 150 nm), and high quantum yield (∼ 1) make the lanthanide ions interesting compounds in photonic applications as luminescent markers in biology and medicine, lasers and optical amplifiers (BINNEMANS, 2009; BÜNZLI; ELISEEVA, 2010; BÜNZLI; PIGUET, 26 2005; CARLOS et al., 2009) and thermometry (BRITES et al., 2010; CHAMBERS; CLARKE, 2009). In crystals containing lanthanide ions in uniaxial morphology, interesting spectroscopic properties are investigated. Song et al., 2004 investigated the luminescence of nanowires and nanoparticles of LaPO4:Eu3+ and observed an enhancement of quantum efficiency in nanowires. The authors found that Eu3+ occupies additional crystallographic sites in anisotropic compound. Luminescent Gd2O3: Eu and Gd2O3:Yb-Er nanorods and nanotubes have been investigated in optical imaging and uorescent labeling applications (DEBASU et al., 2011). The authors concluded that the emission lifetime was dependent to the size of 1D nanostructures. The possibility of organizing nanostructures, including nanowires and nanotubes based on lanthanide compounds energy converters of NaYF4: Yb, Er was explored in the assembly of macrostructures (super networks) (YE et al., 2010). The synthesis of nanophosphors opens very promising perspectives for applications in biology and energy. Among naturally occurring anisotropic materials, tellurium holds great promise as template for the preparation of one- dimensional luminescent nanostructures. Next section will give a state of the art of tellurium nanostructures since the first studies and current efforts from both scientific and technological perspectives. 1.1. Tellurium Tellurium is mostly obtained (90 %) from electrolytic refining of smelted copper (extracted from anode slimes). Japan is the largest producer of refined element. According with 2016 United States Geological Survey report, the world production of tellurium is estimated at 400 tons (GOLDFARB, 2015). The concentration of tellurium found in the most of rocks is below 3 ppb. To date, the abundance of tellurium is inferior to rare earth elements and eight times less abundant than gold. About 40% of high-purity tellurium is consumed for the production of CdTe solar panels as highlighted in Figure 1. In metallurgy, Te is usually used as an additive in steel, copper and lead alloys to improve machinability and resistance to vibration and fatigue. Tellurium can replace selenium or sulfur as vulcanizing agent, accelerator agent in the rubber industry, as well as a component of catalysts for synthetic fiber production. Other uses included those in photoreceptor devices and as a pigment to produce various colors in glass and ceramics. Figure 1.Global consumption estimates for the end use of tellurium are as follows: solar, 40%; thermoelectric power generation, 30%; metallurgy, 15%; rubber applications, 5%; and 10%, other. 27 Reference: Goldfarb, R. (2015) Tellurium, a metalloid belonging to group 16 of the periodic table, is a chemically stable and water insoluble element. Tellurium can exist in various redox states: telluride (-2), elemental tellurium (0), tellurite (+4), and tellurate (+6). In Figure 2, there is illustrated the standard reduction potential of tellurium. Tellurium was first recognized a distinct element by Martin Heinrich Klaproth, a German chemist, in 1798 and was carefully investigated by Berzelius in 1826 (WEEKS, 1932). In 1914-1916, the Italian P. Fenaroli published a series of articles showing that tellurium acts as a coloring agent in glass. Only under reducing conditions, Te provides blue, red, pale pink or brown glasses whose colors are approximately the same as Te would have in aqueous colloidal suspension (BANCROFT, 1918, SILVERMAN, 1932). Figure 2 - Standard reduction potential of Te in acid and alkaline media Reference: Vanysek, P. (1991). 28 The typical synthesis of tellurium glass coloring agent involved a mixture of sodium tellurate and sodium protalbinate (Albumin from egg white) with aqueous hydroxylamine hydrochloride (reducing agent). The glass color shifts from brown, red, or blue according with the increase of tellurium concentration. At this time, they estimated that the color changes were associated with the increase of size of the Te colloidal particles (BANCROFT, 1921). 1.1.1. One-dimensional Te nanostructures Te in bulk form is a p - type narrow bandgap (0.33 eV) semiconductor at room temperature. Upon downscaling, Te crystallizes into helical-chains as a result of the discrete nature of its trigonal phase. The representation of Te structures is shown in Figure 3. Figure 3 - Representation of Te trigonal structure. Te grows into NWs based on the spiral chains along the [001] direction. Reference: Adapted from Tsai et al., (2015). The first article describing richer insights about the optical properties and morphology of Te colloidal particles was reported in 1953 by Johnson, R.A (JOHNSON, 1953) with the help of electron microscopy. The aqueous colloidal suspensions of Te particles with color varying from amber to blue were prepared by reduction of Te4+ acid solutions by hypophosphorous acid/sodium hyposphosphite buffer solution in the presence of gum arabic as a stabilizer. Johnson, R. A (JOHNSON, 1953) first unveiled the one-dimensional shape of Te structures and confirmed that the color shift, previously described to occur in tellurium glasses (BANCROFT, 1921), was associated with the aspect ratio of Te structures. Almost 20 years later, the Japanese Nishida & Kimoto carried out a detailed structural analysis of Te one-dimensional particles prepared by evaporation in argon at low pressure by using 1000 KV electron microscope (KIMOTO; NISHIDA, 1967). The anisotropic behavior of the trigonal lattice of Te “building blocks” enables the growth of one-dimensional Te (Te1D) particles. The burst of publications describing the preparation and applications of Te1D particles started in 2001 by Xia group in a communication, which also featured a cover of 29 Advanced Materials (MAYERS; XIA, 2002a). Previous efforts had been undertaken to tightly control the synthesis of Se nanowires by the same group (which has a nearly similar crystal structure Te) (GATES; YIN; XIA, 2000; GATES et al., 2002). The authors also reported the synthesis of Te1D particles in the shape of triangular, filamentary and needle-like structures (MAYERS; XIA, 2002b). Single-crystal Te nanotubes were achieved by using polyol method by cold-injection of telluric acid on ethyleneglycol, which in turn acts as both solvent and reducing agent. In the literature, the bottom-up synthesis of Te1D particles was further explored with a myriad of reducing agents, stabilizers, and Te sources. Te1D nanostructures (LIN; YANG; CHANG, 2008a; LIU et al., 2003; SONG et al., 2008) have been synthesized by various approaches such as electrochemical deposition method, (SHE et al., 2009) photolysis (WEBBER; BRUTCHEY, 2009; ZHANG et al., 2007), vapor deposition (SEN et al., 2007), microwave (LIU et al., 2010a), laser-assisted synthesis (VASILEIADIS et al., 2013), and template-directed synthesis (WEI et al., 2003a; XI et al., 2006). The methodology based on hydrothermal synthetic route is one of the most studied for the preparation of Te1D nanostructures. In general, tellurium precursor is water-soluble tellurates (Na2TeO3, Na2TeO4 or H2TeO4.2H2O) in hydrothermal synthesis. Strong reducing agents such as hydrazine (N2H4) and sodium borohydride (NaBH4) are usually introduced to produce the initial Te seeds. Other reducing agents are also explored in the literature such as ethylenediamine (XI et al., 2007), formamide (HCONH2) (XI et al., 2005), sodium sulfite (Na2SO3) (LIU et al., 2004a), sodium thiosulfate (Na2S2O3) (LIANG; QIAN, 2009), sodium tungstate (ZHANG; WANG; WEN, 2009) or biomolecules like alginic acid (LU; GAO; KOMARNENI, 2004), ascorbic acid (LI; ZHANG; QIAN, 2008), glucose (CAO et al., 2009), gluconate (GAO; LU; KOMARNENI, 2006), amino-acids (HE; YU; ZHU, 2005a) and starch (LU; GAO; KOMARNENI, 2005). In many studies involving the hydrothermal method, low-soluble sources of tellurium precursors like TeO2 or bulk Te0 are mixed together with dissolution agents such as triethalonamine/fluoboric acid (HBF) (MA et al., 2011a), KOH/DMF(WEI et al., 2003a), NaBH4 (GAUTAM; RAO, 2004), N2H4 (WANG et al., 2010b) and synthetic polymers such as polyethylene glycol (PEG), polyvinyl alcohol and polyvinylpyrrolidone (PVP) (WANG; WANG; WANG, 2008).The outcome is unstable Te2- intermediates that are further oxidized to grow Te1D nanostructures under a dissolution-recrystallization method. 30 Lin and coworkers prepared Te nanorods with 250-880 nm in length and 8-20 nm in diameter by reducing TeO2 in an aqueous solution of N2H4 at room temperature for different reaction times (10-120 min) (LIN; YANG; CHANG, 2008b). In this approach, no stabilizing agent was utilized during the nucleation and growth of Te nanorods. Noteworthy, in order to stop the growth of Te nanorods, the reaction batch diluted with a suspension of an aqueous solution of sodium dodecyl sulfate. Several non-hydrothermal/solvothermal routes in solution-phase approach have been developed along the last decade for the controlled synthesis of Te1D nanostructures. Usually, the main differences among the current protocols rely on the changes of Te precursors, reducing and stabilizing agents. Besides H6TeO6, NaTeO3, Te, and TeO2 precursors, (NH4)2TeS4 (LIU et al., 2004b) and diethyldithiocarbamato tellurium (WANG et al., 2013, 2010a) have been also explored to produce Te1D nanostructures. It has to be pointing out that several studies address to the influence of stabilizing agent such as thiols (SREEPRASAD; SAMAL; PRADEEP, 2009), ionic liquids (MA et al., 2011b; THIRUMURUGAN, 2007; ZHU et al., 2004), zeolites (WEI et al., 2003b), ionic (LI; ZHANG; QIAN, 2008; PARK et al., 2015; XI et al., 2006), and nonionic (ZHU et al., 2011) surfactants. There exist fascinating pursuits for the use of Te1D nanostructures on practical applications. Pristine Te1D nanostructures have shown remarkable performance in distinct applications: photoconductivity (LI et al., 2012; LIU et al., 2012), gas sensing (SEN et al., 2009; TSAI; LIN; CHANG, 2012; WANG et al., 2010b), antibacterial agent (CHOU et al., 2016), thermoelectrical applications (GAO et al., 2015; HEYMAN et al., 2014; PARK et al., 2015), supercapacitor electrode (TSAI et al., 2015) and battery cathode (DING et al., 2015). In addition, due to its high reactivity toward a wealth of chemicals, Te can be used as sacrificial template for the synthesis of telluride and metallic 1D nanostructures. Alternatively, Te1D nanostructures can be coated with an intermediate and functional carbonaceous layer for the deposition of a wide range of compounds such as oxide and metallic nanoparticles. These Te derivative 1D nanostructures and ongoing efforts are summerized in the next section. 1.1.2. One-dimensional Te hybrids In 2005, the group of Prof. Shu-Hong Yu from University of Science and Technology of China published their first contribution of many to come on the synthesis of Te1D nanostructures and Te derivative 1D nanostructures (HE; YU; ZHU, 2005b). Shuttle-like scrolled Te nanotubes with flexible sharp ends and dendritic Te crystals were prepared under 31 hydrothermal conditions with the assistance of alginic acid, lysine, serine and histidine. In the same year, the group reported the large-scale synthesis of Te nanoribbons under mild reaction conditions by reducing NaTeO3 with tetraethylene pentamine at 80 °C and ambient pressure (HE; YU, 2005). One year later, the same group contributed with important articles on the synthesis of Te1D nanostructures: i) large-scale synthesis of ultrathin (4-9 nm in diameter), blue-violet luminescent Te nanowires and nanoribbons (QIAN et al., 2006a); ii) protocol for coating of Te nanowires with functional carbonaceous layer (; nanocables) (QIAN et al., 2006c). In this process, glucose molecules used as a carbon source were absorbed onto the dispersed ultrathin Te nanowires template in water. Under hydrothermal conditions, the adsorbed glucose molecules are polymerized, carbonized, on the surface of Te nanowires, which in turn induce the heterogeneous nucleation and growth of carbonaceous species. Therefore, Te@C nanocables are prepared instead of carbon spheres colloids, a common outcome obtained from homogeneous nucleation in the absence of any template. From the synthesis of pristine Te nanowires and Te@C nanocables, they have successfully explored the conventional chemical templating route to achieve a myriad of 1D nanostructures (LIANG et al., 2013a). In the chemical templating (or sacrificial templanting) the final material shape around the surface of the sacrificial template while the template is progressively consumed. The template once consumed can be recycled and repeatedly used as template (WANG et al., 2015). 1.1.3. Te@C hybrid nanostructures Yu and coworkers extensively explored the preparation of Te@C nanocables for multiplex synthesis (LIANG et al., 2013a). Te nanowires are readily susceptible towards oxidation (LAN et al., 2007) and the direct deposition of oxide layer is hardly achieved without an intermediate and functional coating. Te@C nanocables displaying hydroxyl or carboxyl functional groups have been used to graft metal oxides or metal nanoparticles (LIANG et al., 2013a). After removal of Te cores from Te@C nanocables by chemical etching, pure carbonaceous nanofibers with chemically active surface can be obtained (QIAN et al., 2006c). Nevertheless, distinct strategies have been explored to produce a carbonaceous layer on the surface of Te1D nanostructures (LIANG et al., 2013a): i) Te@C nanocables have been prepared by reduction of Te salt precursor in the presence of carbohydrates and ionic surfactants under hydrothermal conditions (SONG et al., 2009; WANG et al., 2009a, 2009b). So far, glucose is widely employed as both reducing and carbonizing agent. 32 However, others polysaccharides like dextran (WANG et al., 2009b) have shown to deliver uniform coating of carbon. The major drawback of this method relies on the poor control over the size of both Te core and the carbon layer as well as aggregation issues; b) Te@C nanocables have also been prepared by carbonization of glucose under hydrothermal conditions in the presence of pristine Te1D nanostructures (LIANG et al., 2013b; QIAN, et al., 2006c); Once Te@C nanocables are submitted to oxidation for tellurium withdrawing, carbonaceous nanotubes of controlled dimensions are achieved which serve as template for the synthesis of 1D oxides (e.g. Fe3O4, TiO2) or active surface to attachment of metallic nanoparticle (e.g. Au, Ag, Pt, Pd) as shown in Figure 4. For example, carbonaceous fibers were used as sacrificial template to prepare uniform carbon@silica nanocables and silica nanotubes via sol-gel method followed by heat treatment (QIAN et al., 2006b). c) Two step synthesis involving the preparation of Te1D nanostructures coated with a carbon precursor (i.e. resin) under hydrothermal conditions and subsequent carbonization of the resulting nanostructures. The carbonaceous precursor usually regards a resin derived from polycondensation between phenolic compounds and formaldehyde. To date, Qian and coworkers (QIAN, 2010) prepared Te@phenol-formaldehyde resin core- shell nanowires through one-pot synthesis under hydrothermal conditions. However, the authors did not explore subsequent carbonization step to achieve Te@C nanocables or even carbonaceous nanotubes. Besides carbonaceous hybrids, previous efforts had led to the fabrication of single-crystalline telluride and metallic one-dimensional nanostructures by using Te1D nanostructures as sacrificial template. For example, Te1D nanostructures combine with other elements to produce materials of high technological relevance such as CdTe, PbTe, and Bi2Te3 (MOON et al., 2010a, 2010b; SAMAL; PRADEEP, 2010; YANG et al., 2014) by simple mixture of the salt of desired metal/semi-metal against Te nanowires or nanorods in solution-phase. Ultrathin Te nanowires were successfully used for the fabrication of high aspect ratio PbTe (LIANG et al., 2009b), CdTe (LIANG et al., 2009b), Ag2Te (LIU et al., 2012) and PdPtTe nanowires (LI et al., 2013). Tellurium nanowires have also been used to fabricate 1D metal and alloyed/multimetal chalcogenide nanowires (YANG et al., 2015; LIANG et al., 2013). Ultrathin Pt and Pd nanowires/nanotubes were easily achieved by simple galvanic displacement (LIANG et al., 2009a) with ultrathin Te nanowires. 33 Figure 4 - The panels outlined with blue rectangle display core/shell 1D nanostructures fabricated by using Te@C nanocables as templates: (A) Pt@CNFs, (B) Pd@CNFs, and (C) Au@CNFs. The panels outlined with pink rectangle highlight ternary 1D hybrid structures: (D) core/shell Au@C nanocables obtained by using Te@C nanocables as template and further decorated with Fe3O4 nanoparticles. The panels highlighted with red outline show the 1D binary hybrid nanofibers: Carbon nanofibers decorated with (E) Fe3O4, (F) TiO2 oxide nanoparticles, or metallic nanoparticles: (G) Ag, and (H) Au. The panels outlined with green rectangles highlight the metal oxide nanotubes fabricated by templating against Carbon nanofibers: (I) TiO2, (J) SnO2, (L) ZrO2, and (M) BaTiO3. Reference: Adapted from Liang et al. (2013a) with permission. Copyright 2013 American Chemical Society Pristine ultrathin Te nanowires were also utilized as template to drive the growth of metal- organic framework (MOF) nanofibers (ZHANG et al., 2014). The active surface of Te1D nanostructures was used to induce the nucleation and growth of Zn(MeIM)2 (ZIF-8; MeIM = 2- methylimidazole) nanocrystals (zeolite-type MOF), resulting in nanofibers with high-aspect- ratio and controllable diameters. Subsequently, the authors showed that Te@ZIF-8 core-shell nanofibers are exceptional precursor for the synthesis of doped carbon nanofibers through feasible calcination. These doped carbon nanofibers displayed excellent electrocatalytic performance for oxygen reduction reaction. 34 1.1.4. Assembly of 1D Te derivative nanostructures In addition to the challenge on the control of morphology parameters, many efforts have been attempted to improve the assembly of these anisotropic crystals into well-aligned arrays. In this way, a limited number of reports describe the new properties as consequence of assembly of 1D tellurium nanostructures in applications such as optoelectronic and sensor devices. For example, Sen and coworkers describe the preparation of vertically aligned Te1D nanowires synthesized by physical vapor deposition approach (SEN et al., 2008). The Te1D array showed pronounced sensibility to N2 and H2S vapors and better selectivity for detection of chlorine gas. Similar approach has been used to study vertical Te nanowires and nanorods array as potential field emitters (CHAVAN et al., 2009; SAFDAR et al., 2013). Te1D papillae-like nanostructures prepared by self-catalyzed vapor transport and hierarchically organized in nano-and micrometer scale showed superhydrophilic surface (VELÁZQUEZ et al., 2012). This unusual property has been attributed to the rough surface resulting from parallel alignment between the Te1D nanostructures. Liu and coworkers studied the photoconductivity of macro-scale assembled Te nanowires of large aspect ratio by Langmuir Blodgett technique (LIU et al., 2010b). The photoconductivity behavior was reversibly and intensity-dependent of the number of repeating one-dimensional nanostructures arrays assembled in parallel and crossed directions and patterned into periodic mesostructures. Recently, an easy protocol for the alignment of Te nanowires in water/butanol interface has been demonstrated (MOON et al., 2011; NARAYANAN et al., 2015). The array of Te nanowires was transferred to silicon substrate and investigated to fragment analytes upon the application of low voltages (~1 V) for ion mass spectroscopy. The effect of aligned Te nanowires was strongly anisotropic on molecular ion intensity for many analytes including organic molecules and amino acids (NARAYANAN et al., 2015). Additionally, since the synthesized 1D luminescent nanostructures are placed on cambered or flat substrates, their orientation is hardly controlled under drying of suspension in ordinary conditions. The alignment of 1D luminescent nanostructures into side-by-side either head-to- head assembles is essential for the development of great and practical devices. The manipulation of 1D luminescent nanostructures in ordered arrays could be interesting for the study of optical gain medium in stimulated emission processes (lasing), field emission and wave 35 guiding devices, and component of optical sensors (EBAID et al., 2015; GUO; YING; TONG, 2014; HUANG, 2001a; PAN et al., 2005; SIRBULY et al., 2005; YANG et al., 2002). In previous studies, we investigated the preparation of stable aqueous suspensions of Te1D nanostructures in the shape of long/flexible wires, spine-like and rods by using assisted synthesis in the presence protecting colloids (PCs) molecules derived from natural polymer sources (pectin and cellulose derived) as well as ionic and non-ionic surfactants (SILVA, 2012). Herein, Te1D nanostructures will be used as template to design arrays of 1D luminescent nanostructures and hybrids nanostructures containing metallic nanoparticles. This topic will be explored in Chapter 4. Beyond that, a key requirement in constructing practical solid devices is to transfer uniformly aligned 1D luminescent nanostructures at large scale into a substrate. Usually, the alignment of 1D luminescent nanostructures on flat substrates have been achieved by using direct deposition either by vapor-liquid-solid and vapor-solid-solid processes at high temperature (> 500 ºC ) (FUKUI et al., 2010; WANG et al., 2005) or seed-assisted chemical growth at comparatively lower temperatures (ZHANG et al., 2006). However, there is a growing need to fabricate 1D luminescent arrays over flexible rather than rigid photonics devices, eliminating mechanical and geometrical design constraints imposed by rigid and brittle films. In general, flexible substrates are limited in terms of thermal stability so alternative techniques compatible with solution-phase methods have been evaluated for such purposes. Therefore, techniques for controlling the assembly and alignment of 1D nanostructures synthesized by solution-phase methods on flexible substrates include, for example, those that utilize electrical (SMITH et al., 2000) and magnetic fields (HANGARTER; MYUNG, 2005), contact printing (FAN et al., 2008), physical stretching (WU; SU; JIANG, 2012), liquid-liquid interfaces (MOON et al., 2011), Langmuir-Blodgett (TAO; HUANG; YANG, 2008), blown bubble (YU; CAO; LIEBER, 2007), and microfluid flow methods(HUANG, 2001b). 1.2. Biopolymers as flexible transparent substrates Biopolymers, both natural polymers and polymers produced from natural feedstock by synthetic routes, show great potential as flexible substrates for electronics and photonics applications. The polymer source in a renewable approach from biomass is increasingly in focus for commercial trends and government policy. The advantages include wide structural and functional diversity, lower toxicities and biodegradability. Currently, there are two fields that biopolymers have been explored: a) biotronics: an emerging field in which biopolymers are 36 used in devices for photonics and electronics applications. b) biophotonics: photonics devices are used in biological systems whose fabrication can comprise biopolymers. It is important to note that a limited number of biopolymers fulfills the optical properties required for photonic applications. Beyond that, other implications for practical application rely on mechanical strength, thermal stability and chemical resistance. Specifically, natural polymers garnered a great deal of attention in the last 10 years as optical material. 1.2.1. Natural polymers for photonics Nature itself has made exceptional use of structural natural polymers. Most natural materials are actually composites of a fibrous or crystalline polymer and an amorphous polymer binder, whose final material performs striking functions on protection, support, and structure. Examples include wood, seashells, invertebrates’ exoskeleton, spider web fibers, and cocoons. Natural polymers can be simply defined as macromolecules that occur in nature. Silk, cellulose, hemicelluloses, lignin, and starch, deoxyribonucleic acid (DNA), chitin, chitosan are examples of natural polymers. Raw polymers found in nature are usually insoluble in water and in organic solvents. Additionally, raw natural polymers are opaque and inappropriate for the fabrication of optical materials. Potential limitations on natural polymers processing have been resolved by implementing a number of creative techniques. There are different physical and chemical routes to dissolve and give them desirable properties such as film forming, transparency, and chemical stability. Therefore, optically transparent natural polymers can be processed into relevant flexible host matrix to optically active components (e.g. luminescent compounds). Materials that can be isolated from the native environment and repurposed into freestanding film may serve as useful device technologies. Important achievements have been made with regards the development of freestanding biopolymer films with exceptional optical, thermal and mechanical properties for photonic applications. Few examples will be highlighted indicating the wide range of applications of natural polymers in photonics. DNA-based biopolymer extracted through an enzyme isolation process from fish has been explored as photonic material. Prof. Y. Okahata from Tokyo Institute of Technology firstly demonstrated the feasibility to tailor transparent and water-insoluble DNA-based films derived from fish products (mostly sodium salt of DNA from salmon testes, see Figure 5B) around 20 years ago (TANAKA; OKAHATA, 1996). Natural DNA, which is an anionic polyelectrolyte, 37 is soluble in water but can be precipitated with cationic surfactants in water (PONTIUS; BERG, 1991). Okahata and coworkers found that DNA-Na+ becomes soluble in polar organic solvents by replacing Na+ ions with long single- and double chain alkyl quaternary ammonium ions (Figure 7C) (TANAKA; OKAHATA, 1996). Transparent films of DNA-alkyl quaternary ammonium were feasible upon drying of solution on a flat surface. Prof. Naoya Ogata from Chitose Institute of Science and Technology pioneered the use DNA for photonics and biotronics applications (KAWABE et al., 2000). With a collaboration between the Air Force Research Laboratory and Chitose Institute of Science and Technology, the team identified a material with potential for optoelectronic applications by extending prior strategy investigated by Okahata and coworkers to obtain transparent films through modification of native DNA with sodium hexadecyltrimethyl ammonium chloride (CTMA), a cationic surfactant (WANG et al., 2001b). The outcome is transparent films with enhanced solubility and thermal stability. DNA- CTMA films have been described for substrate of organic light emitting diodes (OLEDs), light amplification host (LEE et al., 2008), gate dielectric in organic field-effect transistors (OFET) (STADLER et al., 2007), for conductive cladding layers in waveguides (GROTE et al., 2004), host for solid-state dye lasing devices (KAWABE et al., 2000) and dyes featuring nonlinear optical properties (GROTE et al., 2004; WANG et al., 2001b). Noteworthy, the optical losses of DNA-CTMA at the communications wavelengths have been previously measured to be 0.2 dB/cm at 1300 nm and 0.7 dB/cm at 1550 nm, which are relatively low values (STECKL, 2007). A more detailed review on the optical applications and outlooks of DNA-based polymers can be found in the work of Su and coworkers (SU; BONNARD; BURLEY, 2011), Steckl and coworkers (STECKL et al., 2011), and Kwon and coworkers (KWON; HOON CHOI; JIN, 2012). Chitin is the second most abundant polysaccharide composed by linear 2-acetamido-2- deoxy-D-glucopyranose (N-acetyl-D-glucosamine) units linked by -(1,4-) linkage. Native chitin is a semicrystalline biopolymer with a microfibrillar morphology usually found many fungal cell walls, nematodes, insect exoskeletons, and crustacean shells. Chitin is insoluble in the most of the solvents. In 2012, Yano and coworkers (SHAMS et al., 2012) prepared low thermal expansion and transparent crab shells. They investigated the fabrication of fibrous chitin and resin composites to make optically transparent films appropriated for contact lenses, sensors, and optical screens for flexible or flat panel displays, e-paper devices and solar cells. 38 Figure 5 - A) Photography of an ordinary salmon B) DNA solid powder extracted from salmon (C) Aqueous solution of DNA-cetyltrimethylammonium (DNA-CTAM), (D) DNA- CTAM thin films incorporated into blue-emitting OLEDs. (E) Picture of an ordinary crab; (F) and (G) Transparent film fabricated by airbrushing a suspension of chitin nanofibers (3 nm in diameter) in in hexafluoro 2-propanol. (H) Chitin reflective optical grating replica molded from a grating with 1200 grooves/mm. Scale Bar: (F) 1 cm; (H) 0.5 cm. (I) Atomic force microscopy image of bacterial celluse pellicle; (J) Transparent freestanding bacterial cellulose sheet coated with acrylic resin. The final composite affords 60 wt% of bacterial cellulose content. (L) Transparent freestanding bacterial cellulose sheet coated with a polyurethane resin derived from castor-oil. (M) Transparent composite described in (L) being used as flexible substrate for the fabrication of OLED device. Reference: (A-D) Adapted from Steckl et al., (2011). Copyright 2011 Optical Society of America. (E-H) Adapted from Zhong et al., (2011). Copyright 2011 John Wiley & Sons, Inc. (I, J) Adapted from Yano et al., (2005). Copyright 2005 John Wiley & Sons, Inc. (L, M) Adapted from Pinto et al., (2015). Copyright 2015 Royal Chemical Society. Prof. Marco Rolandi group from Washington University has been contributing with important advances in the use of chitin nanofibers on optical applications (ZHONG et al., 2011). Although chitin is insoluble in water or common organic solvents, it is feasible to dissolve it in hexafluoro-2-propanol. The result is a suspension of ultrathin (3 nm) chitin nanofibers that can be self-assembled from micro- to nanofabrication of (patterned) transparent films by using airbrushing and soft lithography (replica molding and microcontact printing) techniques (see Figure 5, F-H). 39 The main derivative obtained from chitin is chitosan, which in turn is produced by the deacetylation of chitin. Chitosan is soluble in diluted acids. Although chitosan has film forming features, it hardly delivers the optical clarity desirable for photonic applications. Natural cellulose fibers with a diameter of 20–50 m are composed by thousands of micro- and nanofibril that can assembly into smooth films with reduced light-scattering effect. Despite the fact that cellulose is available in any plant, pure cellulose polymer can be synthetized by microorganisms. By feeding bacteria such as the specie Gluconacetobacter xylinus with glucose, they are able to extrude crystalline pure cellulose fibers with diameters bellow 100 nm into a 3D network (see Figure 5J). Since cellulose is the most abundant polymer in earth, several works have been dedicated on the pursuit for rational design of transparent cellulose films commercially comparable to the current engineered plastics. Unlike sheet of plant cellulose fibers, sheets of bacterial cellulose (BC) nanofibers display less pronounced light scattering comparing with plant cellulose fibers and exceptional mechanical and thermal properties, whose features are very attractive for the fabrication of flexible substrate for photonics. For example, Legnani and coworkers successfully prepared flexible Organic Light Emitting Diodes (OLEDs) on the pristine surface of BC nanofibers sheet (LEGNANI et al., 2008). An interesting random-lasing action have been shown in BC nanofibers doped with laser-dye molecules and light scattering particles by Santos and coworkers (SANTOS et al., 2014). By taking advantage of the 3D networks of BC nanofibers as host and gain medium, random-lasing action of dye- laser Rhodamine 6G molecules was achieved under diffuse regime in the presence of light scattering Ag or SiO2 nanoparticles. Previous efforts identifying the shortcomings to make very transparent films based on cellulose or BC fibers stimulated the development of distinct strategies. Therefore, three main approaches emerged: a) Cellulose fibers can be dissolved in solution-phase methods through chemical derivatization (e. g. viscose process, carbamate process or with solvents like DMF/N2O4, DMSO/N2O4, CF3COOH, HCOOH/H2SO4, Cl2CHCOOH and TEMPO (2,2,6,6- tetramethylpiperidine-1-oxyl radical) or direct dissolution without derivatization with the help of high hydrogen bonding capacity solvents (e.g. DMAc/LiCl and ionic liquids). The solution of cellulose is further regenerated into transparent film in the presence of an appropriated solvent. It is important to highlight the works conducted by Prof. Lina Zhang from Wuand University and Prof. Isogai Akira from University of Tokyo. Both research groups have 40 unveiled important pioneering dissolution approaches suitable to achieve transparent cellulose films (QI; CHANG; ZHANG, 2009; YAGYU et al., 2015). b) another approach to prepare transparent films based on cellulose involves the fabrication of cellulose composites. The additional components usually have similar refractive index than cellulose and fill the gap occupied by air among the fibers mat. The group of Prof. Hiroyuki Yano from Kyoto University has been contributing with several publications in the field of cellulose nanofibers by using this approach. In 2005, Yano and coworkers made a breakthrough in transparent paper technology by utilizing nanofibrillated cellulose impregnated with epoxy, acrylic (Figure 5L) and phenol- formaldehyde resins (YANO et al., 2005). The composites display high fiber content (60 wt%) with outstanding mechanical strength and low thermal expansion coefficient (NOGI et al., 2009). In addition to resins derived from synthetic monomers, an increasing number of approaches have been compelled to the fabrication of transparent composites based on BC and renewable biopolymers. Some of these composites include BC/chitosan (FERNANDES et al., 2009), BC/polyhydroxybutirate (BARUD et al., 2011), BC/polyvinyl alcohol (TANG; LIU, 2008), BC/boehmite-epoxi-siloxane (BARUD et al., 2012), BC/poly(L-lactic acid) (KIM et al., 2009), BC/ε-caprolactone (BARUD et al., 2013), BC/epoxidized soy bean oil (RETEGI et al., 2012) among others. Recently, Pinto and coworkers prepared transparent composites with high content of BC nanofibers (>70 wt%) and polyurethane resin derived from castor-oil (PINTO et al., 2015). The low surface roughness, excellent mechanical and thermal stability of the BC/PU films grasped key roles for the construction of flexible OLED devices (Figure 7, M and N). c) The chemical modification of cellulose backbone with organic groups (e.g. nitro, esters, amine, etc.) allows to tune the processing conditions of transparent films in solution-phase with the use of common solvent (e.g aqueous and organic solvents). The chemical modification of cellulose is routinely conducted on hydroxyl groups in anhydroglucose units. The properties of cellulose derivatives depend on the type of functional groups in the side chains. Therefore, a new cellulose-based polymer can be fashioned by choice of an additional moiety to be combined with hydroxyl groups. It is possible to increase the solubility of cellulose derivatives depending of the extension of chemical modification and the molecular weight. For example, carboxymethylcellulose, hydroxypropylcellulose and cellulose acetate are cellulose derivatives that easily dissolve in common solvent such as water, ethanol, and acetone or chloroform, respectively to form transparent films. 41 1.2.2. Silk Fibroin So far, silk fibroin is the most promising natural polymer for photonic applications. The silk fibers are basically composed of proteins. The silk proteins - fibroin and sericin silk - are stored in the glands of silkworm silk and spider as an aqueous solution. During the spinning process, the concentration of these proteins is gradually increased. Finally, the stretching stress is applied to produce a partially crystalline insoluble fibrous thread in which most of the polymer chains in the crystalline regions are oriented parallel to the fiber axis. Specifically, the cocoons of Bombyx mori are "structural bags" made from a single strand of silk with continuous length of 1000-1500 m. Silk fibers have a distinct hydrophobicity and notorious crystallinity. Each raw silk yarn has a longitudinal groove, with two separate fibroin filaments irregularly intertwined and stuck together by sericin. Sericin is a smaller protein that surrounds silk fibroin fibers. Figure 6 illustrates the composition of silkworm silk cocoon. The percentage of fibroin and sericin is 75% and 25% of the total weight of the pod, respectively. Sericin is a protein resistant to oxidation and ultraviolet radiation, is antibacterial, it absorbs and releases moisture easily. Figure 6 - Representation of (A) silk cocoon and (B) silk filaments. (C) Close-up photography of silk filament in an ordinary cocoon. (D) False-color scanning electron microscopy of fibroin/sericin core-shell of silk filaments with a triangular cross section. Reference: (A-C) the author, D) Adapted from Oliver Meckes, Eye of Science website (http://www.eyeofscience.de/en/) 42 Pure silk films have a combination of peculiarities including optical transparency in the visible range, ease of patterning, and the capacity to embed dopants and maintain their biochemical activity. The novelty on the use of silk fibroin in optics came with the collaborative work between biomedical researcher Prof. David Kaplan and the physicist Prof. Fiorenzo Omenetto from Tufts University, a specialist in nonlinear optics and nanostructured materials (such as photonic crystals and photonic crystal fibers). He has pioneered together with Prof. David Kaplan the use of silk as a material platform for optoelectronics and photonic applications. The first publication in 2008 described the fabrication of a functional optofluidic device based on silk fibroin diffractive gratings infused with hemoglobin whose optical properties respond to oxy- and deoxygenation in the environment (LAWRENCE et al., 2008a). The functionalization of silk films was feasible due to the simple processing involving the drying of an aqueous solution of silk fibroin over a patterned surface with grooves spaces down to 125 nm followed by lift off. It should be pointed that this was not the first time that silk fibroin was applied as diffractive element. In 2007, researches from Air Force Research Laboratory, Ohio, reported the use of films cast from silk ionic liquid solutions to produce patterned scaffolds with grooves spaces of 10 µm for cell growth of keratinocytes rather than specific use in photonic applications (GUPTA et al., 2007). Thereafter, Omenetto and Kaplan published other notorious articles in 2008, reporting the use of silk fibroin films of controllable crystallinity as diffractive element by simple casting technique against 2D and 3D nanopatterns with sub-40 nm resolution (PERRY et al., 2008, LAWRENCE et al., 2008b). Figure 9 depicts flat and patterned free-standing silk films. The application of silk in optics materials has been prompted by tremendous progress on the fabrication of flexible, stretchable and transparent silk substrates. Other techniques were later investigated to generate periodic nanopatterned silk fibroin films such as beam lithography and nanocontact imprinting (AMSDEN et al., 2010). The fabrication of periodic lattices in silk fibroin films goes far beyond aesthetic appeal. They have been conceived for colorimetric glucose (AMSDEN et al., 2009) and optofluidic oxygen sensors (DOMACHUK et al., 2009). Patterned silk films consisting of two-dimensional square lattice of air holes and doped with different fluorescent dyes displayed directional and wavelength-specific fluorescent enhancement. By evaluating the scattered light from the nanopatterned silk surface, an optical 43 sensor responsive to fluctuations of the refractive index between the air and patterned interface was demonstrated (MONDIA et al., 2010). The authors also showed that silk fibroin could be processed to fabricate optical waveguides by direct ink writing in a communication article that was also cover of the Advanced Materials journal (PARKER et al., 2009). Figure 7 - (A) Flat and (B) patterned surface. (C) and (D) show the Atomic Force Microscopy (AFM) images of topography of both surface and respective cross-sectional view of (A) and (B). Reference: Adapted from Lawrence et al. (2008b). Copyright 2008 Springer International Publishing. Tailoring transparent natural polymers for photonics often requires structural reinforcement. For these reasons, several recent studies have been reported seeking effectively to improve the physical and mechanical of natural polymers by the fabrication of inorganic-organic hybrid materials. The incorporation of organic-inorganic components has synergetic effects leading to hybrid materials with improved mechanical resistance, higher thermal and chemical stability and biocompatibility, and, in some cases, with functional properties (JUDEINSTEIN; SANCHEZ, 1996; SANCHEZ et al., 2005). 44 To this end, the sol-gel is the most studied approach to prepare transparent inorganic-organic hybrid materials with ameliorated thermal and mechanical properties. Beyond, the sol-gel methodology offers the ability to tune their chemical resistance. For example, the water solubility of films from some natural polymers is disadvantageous for long-lasting photonic applications while there exists a demand for disposable and environment-friendly optical devices with controllable degradability. Sol-gel methodology offers a set of tools and precursors to tightly manipulate the properties of the organic-inorganic hybrids based on natural polymers in solution-phase. 1.3. Organic-inorganic hybrid Sol-gel chemistry is a valuable alternative approach to produce solid-state materials rather than traditional solid-state methods since the solution-phase precursors ensures a completely homogeneous mixture of components towards mild conditions. Noteworthy, the temperature required for material processing can be remarkably lowered leading to (nano) particles, and unconventional inorganic polymers such as glass or ceramics. Basically, the chemistry of the sol-gel process concerns in the hydroxylation and condensation of molecular precursors. Early studies of the fabrication of sol-gel silica material were conducted with silicon salts. In 1846, Ebelmen first reported the fabrication of a transparent glass achieved by exposing SiCl4 to atmosphere (EBELMEN, 1846). Only eighteen year later the conception of ‘sol-gel’ was then clarified by Graham with his work on silica sols/gels with silicic acid as precursor (GRAHAM, 1864). The later years witnessed steady growth over the fabrication of advanced silica materials derived from sol-gel chemistry. It is important to note that the development of sol-gel silica chemistry has been followed by the accelerated progress on the synthesis of silicon precursors. Regardless, in 1928 Case & Reid (DEARING; REID, 1928) paved way for the high-yield synthesis (> 70%) of alkyl orthosilicates and since they are the most common silica alkoxide precursor used for sol-gel silica materials. The hydrolysis (1) and condensation (2, 3) reactions that drive the aqueous sol-gel process of alkyl orthosilicates are displayed bellow. The silica sol-gel method deals to the polymerization of alkyl orthosilicate precursors to an extended pure silicon oxide network under exclusion of water and alcohol. The experimental 45 conditions have since been extensively evaluated and can be carefully tuned, for example through acid or alkaline catalysis, which in turn affect the structure of the gel and the final material. There are several experimental advantages of sol-gel process that triggered the progress on the fabrication of silica materials: i) atomic level mixing of reagents; ii) greater control over particle morphology and size whose features allow tailoring dense or porous silica materials upon lower energy consumption; iii) enable the incorporation of low thermally stable molecules like dyes and biomolecules at room temperature in entrapping silica matrix. Earlier commercial applications of silica materials derived from sol-gel chemistry took place in Germany by Schott AG, in 1985, with the fabrication of antireflective Amiran glasses (COOK; MADER; SCHNABEL, 1985). In the same year, Schmidt disclosed basic findings emerging from a benchmark applied research in the synthesis of organically modified silicates (ORMOSILs) (SCHMIDT, 1985). ORMOSILs are hybrid molecular precursors where at least one of the ≡Si-O- linkages is replaced by a non-hydrolytic ≡Si-C≡ group. Materials containing both organic and inorganic components (i.e. silicates) are particularly advantageous, once new features can be achieved by the combination of organic and inorganic building blocks. Significantly, the organic groups introduce new properties to the silica network like flexibility, hydrophobicity, mechanical strength, and bio affinity. Organic groups can play a dual role on the silica network according with Schmidt (SCHMIDT, 1985): i) Act as network former. In this case, the organic groups are essentially polymerizable monomers that may gather a further polymeric network through polyaddition or polycondensation reactions. Examples of polymerizable groups include vinyl, methacryl, or epoxy; ii) Act as network modifier. Organic groups can also endow non-polymerizable groups since they decrease the crosslink degree of silica network by obstructing bonds at the silicon atom. In this case, alkyl groups and even functional groups like mercapto and amino functions act as network modifiers. Some examples of ORMOSILS are displayed in Figure 8. ORMOSILS are currently considered reinforcing components of transparent natural polymers films for photonic application. This interest relies upon the unique opportunity of combining the most remarkable properties of ORMOSILS and organic polymers trough sol-gel approach in a controlled fashion Flexibility, thermal stability and optical clarity are key dependent properties of the degree of component mixing at molecular level. In this case, segregation should be avoided because it leads to optical losses and lower material strength. The most 46 important guideline for intimate mixing of organic and inorganic counterparts concerns a common solvent since it provides enhanced diffusion. Figure 8 - Some examples of organically modified siloxanes Reference: the author From the basic concepts, there are many possibilities to incorporate ORMOSILS into natural polymers. For example, it is possible to combine organic natural polymers and ORMOSILS components through van der Waals interactions or bind covalently in the polymer backbone. Since the functional groupings linked to the silane are manifold, a large variety of materials can be prepared using sol-gel approach at low temperature. For example, luminescent films were prepared by combining silk fibroin and aminopropyltriethoxysilane grafted with fluorescent oligothiophene (SAGNELLA et al., 2015). Fuents and coworkers report the preparation of flexible and transparent films of chitosan with 3-amino-2-propyl- triethoxysilane (FUENTES et al., 1997) and also mercatopropysiloxane (FUENTES et al., 2010) films. Smitha and coworkers investigated the fabrication of transparent and hydrophobic inorganic-organic hybrid coatings of chitosan with methyltrimethoxysilane and vinyltrimethoxysilane (SMITHA et al., 2008). BC nanofibers and cellulose derivatives also have been modified with ORMOSILS to deliver transparent freestanding films appropriated to photonic applications. Barud and coworkers prepared transparent organic-inorganic hybrids from BC nanofibers coated with nanoparticulate boehmite and epoxy modified siloxane (BARUD et al., 2012). Organic- inorganic hybrid films based on cellulose derivatives have been investigated by the crosslink 47 of cellulose acetate with grafting precursor mixture of pentaerythrithol triacrylate and aminopropyltriethoxysilane (SILVA et al., 2011). Achoudong and coworkers also studied the fabrication of transparent cellulose acetate films modified with vinyltrimethoxysilane that also exhibited high performance on acid gas removal (ACHOUNDONG et al., 2013). Among the myriad of ORMOSILS available in the market, epoxy coupling silanes are very interesting modifiers to achieve transparent hybrids based on natural polymers films with enhanced functionality. Epoxy is a class of versatile polymer materials characterized by the presence of one or more oxirane ring or epoxy groups with their molecular structure. The epoxy function can be maintained to modify the hybrid network or polymerized in the presence of curing agents or UV light. Beyond that, epoxy ring-opening reactions with alcohols, amines, hydroxyl, and thiols offer a pathway to graft optically active compounds (i.e. luminescent nanostructures, quantum dot semiconductors or carbon dots, rare-earth complex) in the hybrid network. Additionally, owing the limited feedstock of natural polymers for high demand optical devices, it is equally important develop materials based on the reuse synthetic polymers. The current level of synthetic polymers usage is roughly nonsustainable. Recycling provides opportunities to leverage the development of sophisticated materials based on recovered synthetic polymers and reduce the impact of their disposal in the environment. Beyond the aesthetic appeal, green recycling strategies are particularly interesting and demanding nowadays. Herein, we explored the fabrication of transparent spin-casting films of polystyrene recovered from disposal of reagents’ packs made of expanded-polystyrene (EPS) for photonic applications. 48 1. OBJECTIVES AND THESIS ORGANIZATION The thesis is organized into the following Chapters Chapter 3 describes the preparation of Te nanostructures and derivative hybrids in solution- phase. The goals of this chapter comprises:  Study of the synthesis of one dimensional tellurium nanostructures through solution-phase approach by surfactant assisted method at different temperatures;  Study the preparation of aligned arrays of one-dimensional tellurium nanostructures;  Investigate the synthesis of one-dimensional Te@metallic nanoparticles or metallic derivative nanostructures by using Te as (sacrificial) template;  Evaluate the functionalization of one-dimensional tellurium nanostructures with a carbonaceus precursor layer of m-dihydroxyphenol (resorcinol)-formaldehyde (RF) resin at low temperature in order to produce Te@RF nanocables;  Study the attachment of metallic or lanthanide based nanoparticles on the surface of Te@RF nanocables as illustrated in Figure 9, A and B. Figure 9 - (A) Metallic or lanthanide based nanoparticles attached on Te@resorcinol- formaldehyde resin nanocables (B) Te1D nanostructures as template for the synthesis of lanthanide based nanotubes. Reference: the author. 49 On the pursue for practical photonic applications, the assembly of these hybrids in optically transparent host is highly desired. We will briefly lay out the current challenges and explore successes and ongoing efforts of the design of transparent host based on natural or recycled synthetic polymers for photonic applications. This work reports the preparation of optically transparent host from a) biopolymers and their epoxy sol-gel derivative hybrids; Particularly, silk fibroin and cellulose acetate biopolymers were investigated; b) recycled synthetic polymer. This study will explore recycled expanded-polystyrene to generate photonic materials. Remarkably, those polymers dissolve in solvents of distinct polarity. The design of optical materials from biopolymers and recycled synthetic polymers deals different synthetic protocols. For instance, well-known optically active compounds such as organic dyes and luminescent Eu3+ compounds will be incorporated in the host matrices in order to comparatively evaluate their optical properties. Chapter 4 and 5 give detailed information about the preparation of two optical materials based on silk fibroin host: distributed feedback laser and luminescent hybrid films rich in epoxy groups, respectively. Chapter 4 covers the preparation of lasing materials by doping silk fibroin patterned free-standing films with a dye laser and light scattering nanoparticles. The goals of Chapter 4 rely on:  Study on the synthesis of SiO2 and Ag light scattering nanoparticles;  Prepare patterned free-standing silk film by casting an aqueous solution of silk fibroin doped with different concentration of Rhodamine 6G (dye laser) on polycarbonate grating from commercial digital versatile discs (DVD);  Investigate the fabrication of distributed feedback lasers based on dye doped silk grating;  Study the effect of the addition of SiO2 nanoparticles and Ag nanoparticles in the lasing properties (threshold power pump and linewidth of laser emission) of dye doped silk films. Chapter 5 describes the study of preparation of flexible