Artigos - Química Inorgânica - IQ

URI Permanente para esta coleçãohttps://hdl.handle.net/11449/25985

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Interaction of Aspergillus niger in Double-Coated Urea Granules Reduces Greenhouse Gas Emissions from N Fertilization
(2023-01-01) Majaron, Vinícius F. ; da Silva, Marisa G. ; Pfeifer, Marcela ; Bortoletto-Santos, Ricardo ; Velloso, Camila C. V. ; Klaic, Rodrigo ; Polito, Wagner L. ; Ribeiro, Sidney J. L. ; Bernardi, Alberto C. C. ; Farinas, Cristiane S. ; Ribeiro, Caue ; Universidade Federal de São Carlos (UFSCar) ; Universidade de Ribeirão Preto (UNAERP) ; Universidade Estadual Paulista (UNESP) ; Empresa Brasileira de Pesquisa Agropecuária (EMBRAPA) ; Universidade de São Paulo (USP)
Urea is the main nitrogen source applied in agriculture and directly impacts agricultural productivity. However, it presents significant losses that reduce plants’ nitrogen use efficiency (NUE) and promote greenhouse gas emissions, such as N2O. The coating technology allows for an increase in the NUE, making the nutrient available gradually and uniformly, and combining with microorganisms’ action. This work developed and evaluated a double-coating system based on castor oil–polyurethane and maize starch activated by Aspergillus niger for urea granules. We tested the coated urea granules in Palisade grass (Brachiaria brizantha) and measured losses of N2O and NH3. The results showed that the combination between controlled release and Aspergillus niger action reduced the N2O and NH3 emissions, suggesting a local buffering pH effect. The urea loss reduction significantly impacted plant development, increasing N use efficiency, dry mass production, and N uptake. The results support the suitability of a coating system combining controlled release and microorganisms, aiming to better synchronize the nutrient with the plant and reduce environmental impacts. Graphical Abstract: [Figure not available: see fulltext.]
Designing Highly Photoactive Hybrid Aerogels for In-Flow Photocatalytic Contaminant Removal Using Silica-Coated Bacterial Nanocellulose Supports
(2023-05-17) Almeida da Silva, Thaís Caroline ; Marchiori, Leonardo ; Oliveira Mattos, Bianca ; Ullah, Sajjad ; Barud, Hernane da Silva ; Romano Domeneguetti, Rafael ; Rojas-Mantilla, Hernán Dario ; Boldrin Zanoni, Maria Valnice ; Rodrigues-Filho, Ubirajara Pereira ; Ferreira-Neto, Elias Paiva ; Ribeiro, Sidney José Lima ; Universidade Estadual Paulista (UNESP) ; Universidade de São Paulo (USP) ; University of Peshawar─UOP ; University of Araraquara─UNIARA ; Universidade Federal de Santa Catarina (UFSC)
This study explores the use of silica-coated bacterial nanocellulose (BC) scaffolds with bulk macroscopic yet nanometric internal pores/structures as functional supports for high surface area titania aerogel photocatalysts to design flexible, self-standing, porous, and recyclable BC@SiO2-TiO2 hybrid organic-inorganic aerogel membranes for effective in-flow photo-assisted removal of organic pollutants. The hybrid aerogels were prepared by sequential sol-gel deposition of the SiO2 layer over BC, followed by coating of the resulting BC@SiO2 membranes with a porous titania aerogel overlayer of high surface area using epoxide-driven gelation, hydrothermal crystallization, and subsequent supercritical drying. The silica interlayer between the nanocellulose biopolymer scaffold and the titania photocatalyst was found to greatly influence the structure and composition, particularly the TiO2 loading, of the prepared hybrid aerogel membranes, allowing the development of photochemically stable aerogel materials with increased surface area/pore volume and higher photocatalytic activity. The optimized BC@SiO2-TiO2 hybrid aerogel showed up to 12 times faster in-flow photocatalytic removal of methylene blue dye from aqueous solution in comparison with bare BC/TiO2 aerogels and outperformed most of the supported-titania materials reported earlier. Moreover, the developed hybrid aerogels were successfully employed to remove sertraline drug, a model emergent contaminant, from aqueous solution, thus further demonstrating their potential for water purification.
Hydrotalcite loading boosts the potentially toxic element's retention in hydrogel nanocomposites for environmental treatment
(2023-08-01) Pfeifer, Marcela ; Bortoletto-Santos, Ricardo ; Andrade, Flávio A.C. ; Ribeiro, Sidney J.L. ; Aouada, Fauze A. ; Ribeiro, Caue ; Universidade Federal de São Carlos (UFSCar) ; Programa de pós-graduação em Tecnologia Ambiental ; Universidade Estadual Paulista (UNESP) ; Empresa Brasileira de Pesquisa Agropecuária (EMBRAPA)
The improper disposal of potentially dangerous metal-containing wastes is detrimental to the environment and human health, requiring the development of easy methods for removing these cations, particularly in water bodies. The influence of different surface-charged lamellar materials on the sorption and desorption of Cr6+, Cu2+, and Mn2+ in aqueous solutions was investigated by modifying polyacrylamide/methylcellulose (PAc-MC) hydrogels with bentonite or hydrotalcite. In disk or powder form, the adsorption and desorption capabilities were examined. Regardless of their shape, the bentonite-hydrogel and unmodified hydrogel revealed lower contaminant retention capacities on polymeric structures. In contrast, the hydrotalcite-hydrogel demonstrated a stronger affinity for holding ions in the nanocomposite polymeric structure. The nanocomposite produced by calcining hydrotalcite at 550 °C displayed the best retention properties. Shapes of disks or powders did not affect sorption capacity, but disks were considerably more practical for recovering processed materials. These findings contribute to comprehending the retention capacity of modified hydrogels (or modified nanocomposites).
Green host urethanesil based on castor oil doped with Eu3+ complex
(2023-04-01) de Freitas, Beatriz Damasio ; Onishi, Bruno Seiki Domingos ; Caixeta, Fabio Jose ; Bortoletto-Santos, Ricardo ; Garcia, Francis Dayan Rivas ; Messaddeq, Younes ; Ribeiro, Sidney Jose Lima ; Universidade Estadual Paulista (UNESP) ; University of Ribeirão Preto (UNAERP) ; Universidade de São Paulo (USP) ; Université Laval
Polymers based on vegetable oils can be suitable candidates for the replacement of fossil polymers, for instance, polyurethanes (PU) based on castor oil. However, the synthesis PU materials are normally carried out using organic solvents, metals, and high temperatures. To overcome these problems, the sol-gel route is an alternative approach based on mild conditions to produce organic-inorganic hybrid urethanesil (Ut) environmentally friendly. Therefore, in this study, we proposed an organic-inorganic hybrid (OIH) synthesis based on castor oil (CO)-derived Ut, as well as the incorporation and interaction of europium β-diketone [Eu(tta)3(H2O)2] in organic-inorganic hybrid matrix. The Ut self-supporting hybrid was synthesized from the reaction of 3-(triethoxysilyl)propyl isocyanate (ICPTES) and CO in a 3:1 M ratio. The films were obtained using the sol-gel process, following the casting method. The CO-based OIH-Ut films showed high transmittance in the visible and infrared spectrum (90%), and urethanesil showed photoluminescence (PL) with emission at 416.0 nm when excited at 319.0 nm. The results also revealed an increase in the intrinsic quantum yield of PL (QLEu) for [Eu(tta)3(H2O)2]. It has been verified a QLEu value of 27% for the isolated complex, whereas when it is incorporated into OIH-Ut a value of 49% was observed.
UV-protective compound-containing smart textiles: A brief overview
(2023-01-01) Barcha Lupino, João Henrique ; Saito, Gustavo Pereira ; Cebim, Marco Aurélio ; Davolos, Marian Rosaly ; Universidade Estadual Paulista (UNESP)
Excessive exposure to solar ultraviolet (UV) radiation causes human health damages, such as sunburns and skin cancer. Thus, the use of sun-protective clothing is a simple, easy, and practical method for UV protection of the human organism. In this perspective, incorporation, coating, and anchorage of UV-protective compounds in textile fibers have been employed to enhance the UV-blocking ability and/or promote functional finishings to smart fabrics. This review describes recent research efforts on the development of UV-protective compound-containing smart fabrics highlighting the UV-blocking properties and multifunctional activities. Different compound class examples and discussions are presented in order to contribute to new insights into sun-protective clothing and future applications of multifunctional textiles.
Synthesis and Spectroscopic Characterization of a Novel Coordination Polymer of Palladium(II) with Pyrazole and Azido Ligands
(2002-01-01) De Godoy Netto, Adelino Vieira ; Frem, Regina Célia Galvão ; Mauro, Antonio Eduardo ; Universidade Estadual Paulista (UNESP)
The one-dimensional coordination polymer of palladium(II) with pyrazolato (Pz −) and azide (N 3 −) as bridging ligands, of formula [Pd 3 (µ-N 3)(µ-Pz) 5] n, has been prepared. From IR and Raman studies it was evidenced the exobidentate nature of pyrazole ligands as well the µ-1, 1-bridging coordination of azido groups. NMR experiments showed two sets of broadened signals with different intensities indicating the presence of pyrazolato groups in distinct chemical environments. The proposed structure of [Pd 3 (µ-N 3)(µ-Pz) 5] n consisting of a zigzag ribbon in which each (Pz) 2 Pd(Pz) 2 entity is bound to two stacked planar units [Pd(µ-Pz)(µ-N 3)Pd core] with very weak Pd-Pd interaction, based on UV-Vis spectroscopy.
Understanding the Microstructure Connectivity in Photopolymerizable Aluminum-Phosphate-Silicate Sol-Gel Hybrid Materials for Additive Manufacturing
(2023-02-09) Tayama, Gabriel Toshiaki ; Santagneli, Silvia Helena ; de Oliveira Junior, Marcos ; Messaddeq, Younes ; Universidade Estadual Paulista (UNESP) ; Photonique et Laser─COPL─Universite Laval ; Universidade de São Paulo (USP)
In this paper, we report the synthesis and structural characterization of transparent and photopolymerizable aluminum-phosphate-silicate hybrid materials obtained via the sol-gel route, with different aluminum/phosphate (Al/P) ratios. We explored the system Si(1-x)-(Al/P) (x) with x varying from 0.3 to 1, and atomic ratios of Al/P are 1:3, 1:1, and 3:1. All compositions contain high inorganic mass content (up to 40 wt %). Furthermore, they are compatible with vat-photopolymerization platforms. The structural evolution of the hybrid materials with the silicon concentration was investigated by SEM, phase-contrast AFM, and solid-state NMR techniques, using single- and double-resonance experiments. The structure follows the build-up principle using aluminum-phosphate species and alkoxysilane chains as fundamental building blocks. These aluminum-phosphate species were identified as monomeric and dimeric chain structures by comparing different parameters obtained from NMR data to compound models. Monomeric and dimeric aluminum-phosphate chain structures were predominant in 3:1 and 1:3 Al/P ratio samples, respectively, promoting and hindering the heterocondensation with the alkoxysilane precursor, respectively. The photopolymerization mechanism leads to the percolation of the inorganic networks through a parallel polymethylmethacrylate network, resulting in a material with structural heterogeneities in the range of 5 nm, evidenced by phase-contrast AFM.
Publisher Correction: Near-infrared quantum cutting luminescence in Pr3+/Yb3+ doped lead bismuth borate glass
(2023-12-01) Seshadri, Meruva ; Santos, Ilza T. C. ; Bell, Maria Jose V. ; Lapointe, Jerome ; Messaddeq, Younes ; Anjos, Virgilio ; Universidade Federal de Juiz de Fora ; KG Reddy College of Engineering and Technology ; Université Laval ; Universidade Estadual Paulista (UNESP)
In the original version of this Article Jerome Lapointe and Virgilio Anjos were incorrectly affiliated with ‘Department of Physics, KG Reddy College of Engineering and Technology, Hyderabad, TS 501504, India’. The correct affiliations are listed below. Jerome Lapointe: Centre d’Optique, Photonique et Laser, 2375 Rue de la Terrasse, Université Laval, Québec, QC G1V 0A6, Canada. Virgilio Anjos: Grupo de Engenharia e Espectroscopia de Materiais, Departamento de Física‑ICE, Universidade Federal de Juiz de Fora, Juiz de Fora, MG 36036‑900, Brazil. Centre d’Optique, Photonique et Laser, 2375 Rue de la Terrasse, Université Laval, Québec, QC G1V 0A6, Canada. The original Article has been corrected.
Quartzite Nanoparticles as Scatterers for Random Laser Systems
(2022-01-01) Machado, Yan D.R. ; Germano, Gleice C.M. ; Costa, Antonio Mario L.M. ; Pecoraro, Edison ; Carvalho, Isabel C.S. ; Pontifical Catholic University of Rio de Janeiro ; Universidade Estadual Paulista (UNESP)
In this work, we developed and investigated a random laser (RL) based on Rhodamine6G (Rh6G) in ethanol solution with quartzite nanoparticles as scatters in the lasing media.
Anti-counterfeiting strategy based on rare earths and biopolymers
(2022-01-01) Pereira, Daniela Vassalo ; Mello, Yan Gorski ; da Silva Barud, Hernane ; Cavicchioli, Maurício ; Ribeiro, Sidney José Lima ; Universidade Estadual Paulista (UNESP) ; University Center of Araraquara (UNIARA)
Commodity counterfeiting can be resolved by attaching labels made from biopolymers and down- and up-converting particles. Measurements of luminescence spectrum and SEM were made, proving the formation of particles and luminescence.
Hyperspectral scanning of single-microparticle upconverting thermometers
(2022-01-01) Pessoa, Allison R. ; Galindo, Jefferson A.O. ; Serge-Correales, York E. ; Amaral, Anderson M. ; Ribeiro, Sidney J.L. ; de Menezes, Leonardo S. ; Universidade Federal de Pernambuco (UFPE) ; Universidade Estadual Paulista (UNESP) ; Ludwig-Maximilians-Universität München (LMU)
We employed hyperspectral imaging with nanometric spatial resolution in single NaYF4: Yb3+/Er3+ microcrystals to resolve spatially the luminescence spectrum and to study the temperature distribution at the diffraction limit.
Method for separating spectrally overlapping multiphoton upconverted emission bands through spectral power dependence analysis
(2023-05-01) Galindo, Jefferson A.O. ; Pessoa, Allison R. ; Serge-Correales, York E. ; Ribeiro, Sidney J.L. ; de S. Menezes, Leonardo ; Amaral, Anderson M. ; Universidade Federal de Pernambuco (UFPE) ; Universidade Estadual Paulista (UNESP) ; Ludwig-Maximilians-Universität München
The high quantum efficiency and long lifetimes of upconverting rare-earth-doped systems make luminescence band spectral overlap a particularly common phenomenon, frequently associated with various excitation and relaxation pathways. While it is often considered challenging to experimentally distinguish such overlapping luminescent bands, herein it is proposed a new method based on the different spectral responses of those luminescent lines to the excitation power at a single pumping wavelength laser. A model for the population of the overlapping bands in terms of the pump laser power is considered and fitted for each measured wavelength, resulting in separated spectra for each pathway. The results obtained with the proposed method are considered with direct excitation measurements, showing the effectiveness and simplicity of the method in comparison with more traditional approaches.
Size Control and Improved Aqueous Colloidal Stability of Surface-Functionalized ZnGa2O4:Cr3+ Bright Persistent Luminescent Nanoparticles
(2023-01-31) Serge-Correales, York E. ; Neumeyer, David ; Ullah, Sajjad ; Mauricot, Robert ; Zou, Qilin ; Ribeiro, Sidney J. L. ; Verelst, Marc ; Universidade Estadual Paulista (UNESP) ; Centre d’Élaboration de Matériaux et d’Études Structurales (CEMES-CNRs) ; University of Peshawar
Near-infrared (NIR)-emitting ZnGa2O4:Cr3+ (ZGO) persistent luminescent nanoparticles (PLNPs) have recently attracted considerable attention for diverse optical applications. The widespread use and promising potential of ZGO material in different applications arise from its prolonged post-excitation emission (several minutes to hours) that eliminates the need for continuous in situ excitation and the possibility of its excitation in different spectral regions (X-rays and UV-vis). However, the lack of precise control over particle size/distribution and its poor water dispersibility and/or limited colloidal stability required for certain biological applications are the major bottlenecks that limit its practical applications. To address these fundamental limitations, herein, we have prepared oleic acid (OA)-stabilized ZGO PLNPs with controlled size (7-12 nm, depending on the type of alcohol used in synthesis) and monodispersity. A further increase in size (8-21 nm), with a concomitant increase in persistent luminescence, could be achieved using a seed-mediated approach, employing the as-prepared ZGO PLNPs from the first synthesis as the seed and growing layers of the same material by adding fresh precursors. To remove their surface oleate groups and make the nanoparticles hydrophilic, two surface modification strategies were evaluated: modification with only poly(acrylic acid) (PAA) as the hydrophilic capping agent and modification with either PAA or cysteamine (Cys) as the hydrophilic capping agent in conjunction with BF4- as the intermediate surface modifier. The latter surface modifications involving BF4- conferred long-term (60 days and longer) colloidal stability to the nanoparticles in aqueous media, which is related to their favorable ζ potential values. The proposed generalized strategy could be used to prepare different kinds of surface-functionalized PLNPs with control of size, hydrophilicity, and colloidal stability and enhanced/prolonged persistent luminescence for diverse potential applications.
Direct femtosecond laser printing of silk fibroin periodic structure with lower mid-infrared reflectivity
(2023-01-01) Couto, Filipe A. ; Paula, Kelly T. ; Santos, Moliria V. ; Ribeiro, Sidney J.L. ; Mendonça, Cleber R. ; Universidade de São Paulo (USP) ; Universidade Estadual Paulista (UNESP)
Periodic dielectric structures offer an efficient way to control light propagation at micro- and nanoscale, also presenting low losses. Among many techniques that can produce such structures, femtosecond Laser-Induced Forward Transfer (fs-LIFT) is a promising one due to its relatively simple implementation and ability to process broad classes of materials, preserving their integrity. In particular, Silk fibroin (SF), a natural biopolymer, can be processed by fs-LIFT to print well-ordered periodic arrays of microstructures. Due to its high transparency, biocompatibility, and high possibilities of functionalization, SF is a suitable material for photonics. In this work, a 2D lattice of hemi-elliptical SF microdroplets was fabricated via fs-LIFT, and finite-element (FEM) simulations were carried out to study their response to electromagnetic radiation in the near to mid-infrared spectral region, considering the influence of the substrate. The simulation results indicated a decrease in reflectivity which was corroborated with experimental results. In addition, coating the fabricated structures with a higher index dielectric material was shown to enhance the decrease in reflectivity in the mid-infrared spectral region. These results demonstrate a straightforward way to print ordered arrays of SF microstructures in a relatively large area, with potential application as controllable reflectivity coating for the near to mid-infrared spectral region.
Enhanced Photoredox Activity of BiVO4/Prussian Blue Nanocomposites for Efficient Pollutant Removal from Aqueous Media under Low-Cost LEDs Illumination
(2022-12-01) Khan, Abrar Ali ; Marchiori, Leonardo ; Ferreira-Neto, Elias Paiva ; Wender, Heberton ; Parveen, Rashida ; Muneeb, Mohammad ; Mattos, Bianca Oliveira ; Rodrigues-Filho, Ubirajara Pereira ; Ribeiro, Sidney José Lima ; Ullah, Sajjad ; University of Peshawar ; Universidade Estadual Paulista (UNESP) ; Universidade Federal de Santa Catarina (UFSC) ; Federal University of Mato Grosso do Sul ; Government Girls Degree College Dabgari ; Universidade de São Paulo (USP)
Bismuth vanadate (BiVO4, BV) is a widely explored photocatalyst for photo(electro)chemical applications, but its full photocatalytic potential is hindered by the fast recombination and low mobility of photogenerated charge carriers. Herein, we propose the photodeposition of different amounts of Prussian blue (PB) cocatalysts on the surface of monoclinic BV to obtain BV-PB composite photocatalysts with increased photoactivity. The as-prepared BV and BV-PB composites were characterized by an array of analytic techniques such scanning eletron microscopy (SEM), transmission eletron microscopy (TEM), X-day diffraction (XRD), and spectroscopic techniques including Fourier-transform infrared spectroscopy (FTIR), diffuse reflectance spectroscopy (DRS), electrochemical impedance spectroscopy (EIS), photoluminescence (PL), and Raman spectroscopy. The addition of PB not only increases the absorption of visible light, as indicated by DRS, but also improves the charge carriers’ transfer across the photocatalysts/solution interface and hence reduces electron-hole (e−-h+) recombination, as confirmed by EIS and PL measurements. Resultantly, the BV-PB composite photocatalysts with optimum PB loading exhibited enhanced Cr(VI) photoreduction efficiency as compared to pristine BV under visible light illumination from low-power blue light-emitting diodes (LEDs), thanks to the cocatalyst role of PB which mediates the transfer of photoexcited conduction band (CB) electrons from BV to Cr(VI) species in solution. Moreover, as compared to pristine BV and BV + H2O2, a drastic increase in the methylene blue (MB) photo-oxidation efficiency was observed for BV-PB in the presence of a minute quantity of H2O2 due to a synergic effect between the photocatalytic and Fenton-like processes. While pure BV photodegraded around 70% of MB dye within 120 min, the BV-PB/H2O2 and BV/H2O2 system could degrade almost 100% of the dye within 20 min (kobs. = 0.375 min−1) and 40 min (kobs. = 0.055 min−1), respectively. The practical approach employed in this work may pioneer new prospects for synthesizing new BV-based photocatalytic systems with low production costs and high photoredox efficiencies.
PVA-silk fibroin bio-based triboelectric nanogenerator
(2023-01-01) Candido, Iuri C.M. ; Oliveira, Giovanni da S. ; Ribeiro, Sidney J.L. ; Cavicchioli, Mauricio ; Barud, Hernane S. ; Silva, Luygui G. ; de Oliveira, Helinando P. ; Federal University of São Francisco Valley ; Universidade Estadual Paulista (UNESP) ; University of Araraquara - UNIARA
Despite being very promising technology for several devices, triboelectric nanogenerators (TENGs) tend to explore expensive and complex microstructures. This study reports a novel and simple TENG based on the incorporation of silk fibroin in poly (vinyl alcohol) as a simple, low-cost, and easily integrated component for transparent and flexible devices, with output performance of voltage, current, and power density of 172 V, 8.5 μA and 1.304 W.m−2, respectively, and charging capacity of 320 nC per cycle of operation, making possible the light up 56 commercial LEDs and small electronic devices. Adequate control in the polarization degree and morphology of the device are some of the critical factors that improve the performance of the proposed TENG.
Near-infrared quantum cutting luminescence in Pr3+/Yb3+ doped lead bismuth borate glass
(2022-12-01) Seshadri, Meruva ; Santos, Ilza T. C. ; Bell, Maria Jose V. ; Lapointe, Jerome ; Messaddeq, Younes ; Anjos, Virgilio ; Universidade Federal de Juiz de Fora ; KG Reddy College of Engineering and Technology ; Université Laval ; Universidade Estadual Paulista (UNESP)
In this paper, thermally stable lead-bismuth-borate glasses were doped with 0.5 mol% of Pr3+ ions at several concentration levels of Yb3+ ions. Structural characterizations were performed via Raman, differential scanning calorimetry, optical absorption and fluorescence spectra. The Judd–Ofelt intensity parameter, Ω 2, of Pr3+ doped glass was comparatively higher than those from reported ones, which reflects the increase of co-valency and asymmetry of chemical bonds in the local environment of Pr3+. Near-infrared emission in 900–2200 nm wavelength range was recorded through 443 nm blue laser pumping. Visible to near-IR quantum cutting and concentration quenching mechanisms were discussed to understand the luminescent behaviour. Intense IR emission (∼1.0μm) features generated by absorbing one visible photon leads to quantum efficiencies close to 128% in Pr3+/Yb3+ co-doped samples which may improve the solar spectrum absorption and accordingly, increase the efficiency of c-Si solar cells. Emission cross-section, lifetime, figure of merit and gain bandwidth corresponding to Pr3+: 3F2→ 3H4 (∼2.0μm) were comparatively reported suggesting that the glass with molar composition 0.5Pr3+/0.1Yb3+ might be a potential candidate for ∼2.0μm laser operation with low pump threshold.
Optical materials for flexible and stretchable random lasers
(2022-10-01) Gomes, Anderson S.L. ; Valente, Denise ; de Oliveira, Helinando P. ; Ribeiro, Sidney J.L. ; de Araújo, Cid B. ; Universidade Federal de Pernambuco (UFPE) ; Universidade Federal do Vale do São Francisco ; Universidade Estadual Paulista (UNESP)
The development of photonic devices has been largely benefitted by the offer of new flexible and stretchable materials. Many innovative components and devices have been developed for light-based applications. Presently it is recognized that integration of active and passive elements on flexible substrates will simplify many proposed photonic applications. For example, extensive variety of optical sensors integrated on biological tissues, optical waveguides based on polymer films, flexible organic interconnects, and imaging devices, are receiving large attention nowadays. Especially, the search for optical sources such as organic light emitting diodes and lasers are two booming areas. Flexible Random Lasers (FRLs) based on stretchable materials, in particular, have been object of intense research in the past few years. In this paper we present an overview of the FRLs literature, with emphasis in 2D and 3D materials, and the achievements and availability of new flexible organic and inorganic materials for FRLs. In Section 2 we present some basic ideas of Random Lasers (fundamentals, operation, and physical characteristics). Section 3 contains a detailed assessment of various types of FRLs based on biopolymers, electrospinning and natural fibers, silicones, semiconductor nanowires, perovskites, chiral molecules, polyethylene and polystyrene substrates. In Section 4 we present our perspective on new opportunities and emerging applications in this field.
Bone-bioglass graft – An alternative to improve the osseointegration
(2022-01-01) Lopes, Rauany Cristina ; Furlan, Roberto Gustavo ; Correr, Wagner Raphael ; Novo, Lísias Pereira ; Montrezor, Luís Henrique ; Pecoraro, Édison ; Trovatti, Eliane ; University of Araraquara - UNIARA ; Photonique et Laser. Université Laval ; Federal University of the West of Bahia ; Universidade Estadual Paulista (UNESP)
Homologues and xenogenous bones are currently the most used grafts in dentistry because of their performance. However, some inherent disadvantages of these materials have not yet been overcome, such as the lack of biological properties to improve the new bone formation in situ and the long remodeling time. The main aim of this work was to improve the performance of the commercial bone-based grafts and study its properties in vitro. For this purpose, rat bone was combined with bioglass, a synthetic biomaterial that displays high degradation kinetics and bioactivity properties, endowed with biological properties. The sol-gel method was used for 45S5 bioglass (45S5) synthesis, using TEOS and water soluble salts as starting materials. 45S5 was then associated with the rat bone, generating the new graft. FTIR results indicated the hydroxyapatite formation after the bioactivity tests. SEM and bioactivity results were used to assess the evolution of the graft. The bioactivity tests showed that after 30 days the mass gain of about 30 wt.% was due to the deposition of hydroxyapatite crystals at the surface of the grafts, suggesting the potential properties of this new graft for application in implantology.
Process modeling of laser scanning vat-photopolymerization operating under intermittent exposure conditions
(2022-12-01) Posternak, Mykola ; Tayama, Gabriel Toshiaki ; Messaddeq, Sandra Helena ; Messaddeq, Younes ; Laval University ; Universidade Estadual Paulista (UNESP)
Process modeling is an important tool in additive manufacturing (AM) because it elucidates the relationship between processing parameters and material properties. Ultraviolet laser scanning vat-photopolymerization (VPP-UVL) is a common additive manufacturing technique, with a strong physical modeling based on the Jacobs work curve framework. The work curve model was developed for continuous UV exposure (CE) systems, however most VPP-UVL systems to date operate under intermittent exposure (IE) conditions due to the wide adoption of solid-state pulsed-laser sources. Despite their fundamental differences, the Jacobs work curve model is still successfully employed in IE systems under high overlap conditions between pulses, however there are few investigations regarding the limiting conditions for the applicability of the Jacobs work curve model to describe the total exposure profile in intermittent exposure (IE) setups. To address this issue, a model describing a VPP-UVL-IE process was developed. The VPP-UVL-IE model presented here has the same logarithmic dependence as the Jacobs work curve model, but with the addition of a multiplying factor carrying information on the spatial distribution of energy, that is, the overlap of individual pulses. The model is adaptable for non-gaussian beam profiles and can be solved for bidimensional analysis representing layer fabrication. To test the model, a custom-built VPP-UVL-IE additive manufacturing system was used, and structures were printed and characterized using SEM and stylus profilometry. The model`s reliability was investigated under constant overlap and exposure conditions. The model is very robust under constant overlap conditions, with good agreement between experimental data and simulation. For constant exposure, there is good qualitative agreement, but discrepancies occur due to insufficient modeling of the spatial distribution of energy. The 3D printing of complex structures is demonstrated, and the model indicates that VPP-UVL-IE can offer, theoretically, faster printing compared to VPP-UVL-CE for large beam radius (>275 µm), under the assumption of Gaussian beam profile, constant irradiance during the pulses, and dwell time longer than beam travel time. Conversely, same levels of exposure can be achieved at higher scan speed using CW laser sources instead of pulsed sources for small beam radius (<275 µm).

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