Filmes de Langmuir com potencial para preparação de filmes de Langmuir Blodgett de polioxometalatos de európio (lll) precursores e encapsulados: organização e luminescência
Carregando...
Data
2023-03-03
Autores
Eburneo, Matheus Felipe Spadotto
Título da Revista
ISSN da Revista
Título de Volume
Editor
Universidade Estadual Paulista (Unesp)
Resumo
O fenômeno da luminescência se dá pela emissão de radiação em forma de luz, nas regiões de infravermelho, visível ou ultravioleta, a partir da excitação de átomos, íons, moléculas ou materiais. Atualmente, materiais luminescentes encontram aplicações em diversas áreas, como por exemplo, em iluminação artificial, optoeletrônica, sensoriamento, segurança, comunicação, medicina, dentre outras e são utilizados em uma variedade de dispositivos, como lâmpadas, telas (displays), lasers, sensores, marcadores e inúmeros outros. A busca por novos materiais ou novas conformações tem sido objeto de estudo de diversos trabalhos científicos na área. Nesse cenário, destacam-se os polioxometalatos contendo íons lantanídeos, pois apresentam uma variedade de estruturas e propriedades e podem ser estruturados em diferentes conformações, tais como filmes finos organizados. Neste trabalho, foram preparados os polioxometalatos precursores Na9[Eu(W5O18)2] e K11[Eu(PW11O39)2] e encapsulados (DODA)9[Eu(W5O18)2] e (DODA)11[Eu(PW11O39)2] e foram estudadas as propriedades luminescentes e a organização em filmes de Langmuir desses compostos Medidas de espectroscopia vibracional na região do infravermelho, reflectância difusa e testes de solubilidade evidenciaram que os sólidos foram preparados com sucesso. A avaliação das propriedades luminescentes mostrou que o encapsulamento dos polioxometalatos com o surfactante catiônico dimetildioctadecilamônio (DODA) resulta em processos de desativação não-radiativa dos níveis excitados, diminuindo a intensidade de emissão dos compostos encapsulados. Filmes de Langmuir estáveis dos polioxometalatos precursores e encapsulados foram preparados com sucesso pelos métodos semi-anfifílico e de encapsulamento, respectivamente. As isotermas de pressão de superfície em função da área disponível por molécula evidenciaram que o método semi-anfifílico permite a preparação de filmes mais compactos e com maior estabilidade, em relação aos filmes preparados pelo método de encapsulamento. Todos os filmes de Langmuir preparados possuem potencial para a preparação de filmes de Langmuir-Blodgett.
The phenomenon of luminescence occurs through the emission of radiation in the form of light, in the infrared, visible or ultraviolet regions, from the excitation of atoms, ions, molecules or materials. Currently, luminescent materials find applications in several areas, such as artificial lighting, optoelectronics, sensing, security, communication, medicine, among others, and are used in a variety of devices, such as lamps, screens (displays), lasers, sensors, markers and countless others. The search for new materials or new conformations has been the object of study of several scientific works in the area. In this scenario, the polyoxometalates containing lanthanide ions stands out, as they have a variety of structures and properties and can be structured in different conformations, such as organized thin films. In this work, precursor polyoxometalates Na9[Eu(W5O18)2] and K11[Eu(PW11O39)2] and encapsulated (DODA)9[Eu(W5O18)2] and (DODA)11[Eu(PW11O39)2] were synthetized. Luminescent properties and organization in Langmuir films of these compounds were studied. Vibrational spectroscopy measurements in the infrared region, diffuse reflectance and solubility tests showed that the solids were successfully prepared. The evaluation of the luminescent properties showed that the encapsulation of the polyoxometalates with the cationic surfactant dimethyldioctadecylammonium (DODA) results in non-radiative deactivation processes of the excited levels, decreasing the emission intensity of the encapsulated compounds. Stable Langmuir films of precursor and encapsulated polyoxometalates were successfully prepared by semi-amphiphilic and encapsulation methods, respectively. The surface pressure isotherms as a function of the available area per molecule showed that the semi-amphiphilic method allows the preparation of more compact films with greater stability, in relation to the films prepared by the encapsulation method. All prepared Langmuir films have potential for preparing Langmuir-Blodgett films.
The phenomenon of luminescence occurs through the emission of radiation in the form of light, in the infrared, visible or ultraviolet regions, from the excitation of atoms, ions, molecules or materials. Currently, luminescent materials find applications in several areas, such as artificial lighting, optoelectronics, sensing, security, communication, medicine, among others, and are used in a variety of devices, such as lamps, screens (displays), lasers, sensors, markers and countless others. The search for new materials or new conformations has been the object of study of several scientific works in the area. In this scenario, the polyoxometalates containing lanthanide ions stands out, as they have a variety of structures and properties and can be structured in different conformations, such as organized thin films. In this work, precursor polyoxometalates Na9[Eu(W5O18)2] and K11[Eu(PW11O39)2] and encapsulated (DODA)9[Eu(W5O18)2] and (DODA)11[Eu(PW11O39)2] were synthetized. Luminescent properties and organization in Langmuir films of these compounds were studied. Vibrational spectroscopy measurements in the infrared region, diffuse reflectance and solubility tests showed that the solids were successfully prepared. The evaluation of the luminescent properties showed that the encapsulation of the polyoxometalates with the cationic surfactant dimethyldioctadecylammonium (DODA) results in non-radiative deactivation processes of the excited levels, decreasing the emission intensity of the encapsulated compounds. Stable Langmuir films of precursor and encapsulated polyoxometalates were successfully prepared by semi-amphiphilic and encapsulation methods, respectively. The surface pressure isotherms as a function of the available area per molecule showed that the semi-amphiphilic method allows the preparation of more compact films with greater stability, in relation to the films prepared by the encapsulation method. All prepared Langmuir films have potential for preparing Langmuir-Blodgett films.
Descrição
Palavras-chave
Química inorgânica, Európio, Filmes finos, Luminescência, Metais de terras raras