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This work reports on the preparation of materials based on Yb3+/Er3+ co-doped SiO2-Gd2O3 via sol-gel process. The 0.4mol%of Er3+ ions was fixed and the amount of Yb3+ ions changed as 1.8, 5 and 9mol%in order to evaluate the photoluminescence properties as a function of the Yb3+ ions concentration. The prepared xerogels were heat-treated at 900, 1000 and 1100?C for 8 h. X-ray diffraction analyses of the heat-treated materials confirmed the formation of the Gd2O3 cubic phase embedded in the SiO2 host, demonstrating the effective incorporation of RE3+ ions in the structure. The Scherrer?s equation verified that the sizes of Gd2O3 nanocrystallite are between 31 and 69 nm and directly dependent on the heat-treatment temperature. Under excitation at 980 nm all materials showed upconversion phenomena, and the intensities of the emissions in the green and red regions showed to be directly dependent on power pump of laser, quantity of Yb3+ ions and heat-treatment temperature. The materials also showed emission in the infrared region with the maximum around 1530 nm, assigned to the transition of 4I13/2 ? 4I15/2 of the Er3+ ions, region known as technological C-telecom band used in optical amplification.

Eu 3? -doped SiO 2 -Gd 2 O 3 materials were prepared by the sol-gel process changing the Si 4? :Gd 3? molar ratio of 100:0, 70:30, 50:50, 30:70 and 0:100 mol%. The amount of Eu 3? was fixed at 0.2 mol% in relation to the total number of moles of [Si 4? ? Gd 3? ] in the systems. The xerogels obtained from sols were heat-treated at 900, 1000 and 1100°C for 8 h. By TGA/DTA, XRD and Raman spectroscopy analysis, the formation of Gd 2 O 3 crystalline was detected. The microstrains and crystallite size were calculated by the Williamson-Hall and Scherrer's equation, respectively. The results showed the direct dependence of microstrain and crystallite size as a function of the heat-treatment temperature. By the FTIR analysis was observed the elimination of species like H 2 O, O-H and C-H groups, which can act as photoluminescence quenchers. All materials obtained in this work showed intense photoluminescence emission in the red region due to the 5 D 0 ? 7 F 2 transition of Eu 3? . The emission can be observed through the naked eye. The excited state lifetime shows to be dependent on values of refractive index and heat-treatment temperatures. The microstrain values affected the lifetime values and consequently the photoluminescence properties. In summary, the materials obtained in this work showed great absorption in the ultraviolet region promoting intense emission in the visible region, making them potential candidates for future applications in devices such as solar cells, image generator, biomarkers, among others.

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In this article an experimental work was evaluated to explore and disseminate solar energy thematic in an interdisciplinary way to different undergraduate courses. Initially the work was proposed as an activity of a post-graduation discipline for master and doctorate students. From this activity, it was applied an experiment on dye-sensitized solar cells, evaluated in different undergraduate courses in the form of short courses. Dye-sensitized solar cells were mounted by students, to better understand the construction and operation of these cells. Some adaptations were developed in the experiment for the classroom environment, for easier execution of the experiment. The knowledge obtained by students was evaluated from a questionnaire and the results are discussed. The adaptation of an experimental route involving solar cells in the undergraduate environment positively influenced the education of students.Keywords: Solar cell; chemistry education; interdisciplinarity. ResumoNesse artigo um experimento foi avaliado para explorar e difundir a temática de energia solar em um contexto interdisciplinar para diferentes cursos de graduação. Inicialmente o trabalho foi proposto como uma atividade de uma disciplina de pós-graduação para alunos de mestrado e doutorado. A partir dessa atividade, foi aplicado um experimento envolvendo células solares sensibilizadas por corante, avaliada em diferentes cursos de graduação na forma de minicursos. Células solares sensibilizadas por corante foram montadas pelos estudantes, para melhor compreensão sobre a construção e operação dessas células. Foram desenvolvidas algumas adaptações no experimento para o ambiente de sala de aula, facilitando sua execução, fora de um laboratório de pesquisa. Os conhecimentos obtidos pelos estudantes foram avaliados a partir de um questionário e seus resultados são discutidos. A adaptação de um roteiro experimental envolvendo células solares no ambiente de graduação influenciou positivamente na formação dos alunos.Palavras-chave: Célula solar; educação química; interdisciplinaridade.

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