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Previous issue date: 2013-03-01 / Universidade Federal de Minas Gerais / MnWO4 and FeWO4 compounds were synthesized, employing AOT, SDS, CTAB, EG, and PEG 200 as surfactants agents, which was proved by X ray diffraction. Furthermore, these compounds were also characterized by vibrational spectroscopy in the infrared, Raman spectroscopy, scanning electron microscopy (SEM) and transmission electron microscopy (TEM). The SEM images showed that the morphology of the compounds of MnWO4, were changed to plates (AOT and SDS) and particles (CTAB, PEG and EG 200) when the surfactants were employed in the reaction, while the compound achieved without the use of surfactants, showed morphology of rods. The band gap values of band gap found for the compounds of MnWO4 ranged from 2.1 to 2.9 eV, while the values of "band gap" for compounds of FeWO4 were much smaller, ranging between 1.6 to 2.2 eV, and these values were lower than the values of band gap of the compounds obtained without the use of surfactants. These behaviors can be attributed to the presence of defects. The data photoluminescence in general all compounds obtained with surfactants, both of MnWO4, as those of FeWO4, showed photoluminescence intensity far greater than the reference compounds (MnWO4 and FeWO4) which can be assigned to different types of surface defects and interactions between different clusters. The photodegradation of the dyes rhodamine B and rhodamine 6G by nanocrystals MnWO4 proves ineffective, while, FeWO4 compounds were more effective, giving greater emphasis to the compounds obtained with EG and PEG 200. / Foram sintetizados compostos de MnWO4 e FeWO4, com emprego de AOT, SDS, CTAB, EG e PEG 200 como agentes surfactantes, o que foi comprovado pelos difratogramas de raios X. Ademais, esses compostos foram também caracterizados por espectroscopia vibracional na região do infravermelho, espectroscopia Raman, microscopia eletrônica de varredura (MEV), e microscopia eletrônica de transmissão (MET). As imagens de MEV revelaram que a morfologia para os compostos de MnWO4, foram mudadas para placas (AOT e SDS) e partículas (CTAB, EG e PEG 200) quando os surfactantes foram empregados no meio reacional, enquanto o compostos obtido sem o emprego de surfactantes, apresentaram morfologia de bastões. Os valores de band gap encontrados para os compostos de MnWO4 variaram de 2,1 a 2,9 eV, enquanto que os valores de band gap para os compostos de FeWO4 foram bem menores, variando entre 1,6 a 2,2 eV, sendo que estes valores foram menores que os valores de band gap dos compostos obtidos sem o emprego de surfactantes. Estes comportamento podem ser atribuídos à presença de defeitos. Os dados de fotoluminescência, em geral todos os compostos obtidos com surfactantes, tanto os de MnWO4, quanto os de FeWO4, apresentaram intensidade de fotoluminescência bem maior do que os compostos referência (MnWO4 e FeWO4), o que pode ser atribuído aos diferentes tipos de defeitos de superfície e diferentes interações entre os clusters. A fotodegradação dos corantes rodamina B e rodamina 6G pelos nanocristais de MnWO4 mostra-se pouco eficiente, enquanto, os compostos de FeWO4 mostraram-se mais eficientes, dando grande destaque para os compostos obtidos com EG e PEG 200.
| Identifer | oai:union.ndltd.org:IBICT/oai:repositorio.ufscar.br:ufscar/6258 |
| Date | 01 March 2013 |
| Creators | Almeida, Marcio Aurélio Pinheiro |
| Contributors | Silva, Elson Longo da |
| Publisher | Universidade Federal de São Carlos, Programa de Pós-graduação em Química, UFSCar, BR |
| Source Sets | IBICT Brazilian ETDs |
| Language | Portuguese |
| Detected Language | English |
| Type | info:eu-repo/semantics/publishedVersion, info:eu-repo/semantics/doctoralThesis |
| Format | application/pdf |
| Source | reponame:Repositório Institucional da UFSCAR, instname:Universidade Federal de São Carlos, instacron:UFSCAR |
| Rights | info:eu-repo/semantics/openAccess |
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