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Bacterial cellulose (BC) has attracted considerable scientific interest and can be modified, making it more widely useful in composites with guest nanoparticles. In this study, silica nanoparticles obtained from rice husks were used to prepare BC-silica composite aerogels (CAs) via a sol-gel method. Various amount of silica nanoparticles (3, 6, 9 and 12% w/v) dissolved in 2.5 M NaOH were used as a precursor for inclusion into BC. Subsequently, it was employed to form a SiO 2 gel skeleton in a BC matrix by adding 2 M H 2 SO 4, as a catalyst. Increasing levels of silica nanoparticles led progressively lower transmittance values of BC-silica CAs. SEM images revealed a surface morphology of spheroid particles with little agglomeration. The XRD diffraction peaks were gradually covered by a broad peak of silica as increasing silica content. Similarly, FTIR spectroscopy results also indicate the presence of silica in proportion to its content. Furthermore, addition of silica nanoparticles improved the thermal properties using TGA analysis, shifting the decomposition temperature of BC up to 550°C and retaining of BC weight at least 60% with the BC sample with 3% of silica. This unique characteristic implies that silica had a stabilizing effect on polymeric cellulose. These results demonstrate an economical and environmentally friendly preparation of BC-silica CAs that can benefit material applications.

Titanium dioxide (TiO 2 ) has attracted extensive attention in environmental and biomedical applications, owing to its excellent chemical and photochemical stabilities, non-toxicity, and high degradation capacity. However, the wide band gap and low quantum yield of TiO 2 limit its practical applications, and it is possible to improve the optical efficiency and sensitivity of TiO 2 in the visible spectrum. In this work, theoretical calculations based on optical absorption in core-shell structured Ag@TiO 2 nanoparticles (NPs) combined with the surface plasmon resonance property of the core and photoactivity of the shell were investigated as a function of incident light wavelengths in visible spectrum. Shifting of wavelength, at which light was absorbed and enhanced optical absorption activity of TiO 2 NPs due to localized surface plasmon resonance excitation were clearly observed at a level greatly exceeding the value calculated for pure TiO 2 NPs. The calculated results suggest that both the interparticle distance and the diameter of Ag core in the core-shell structure of Ag@TiO 2 NPs influence the tuning and the enhancement of optical absorption spectra. These findings of enhanced optical absorption could be utilized as basic knowledge to design and synthesize Ag@TiO 2 NPs for future environmental and biomedicine applications.

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