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The influence of the presence of barium carbonate (BaCO3) phase on the luminescence properties of barium titanate nanocrystals (BaTiO3) powders was investigated. Structural and optical characterizations of erbium (Er3+) doped BaTiO3synthesized by the sol-emulsion-gel were performed. Using Fourier transform infrared spectroscopy and X-ray powder diffraction, we identified the presence of impurities related to BaCO3and quantified its fraction. It was observed that the presence of BaCO3phase, even at low levels, depletes significantly the infrared-to-visible upconverted luminescence efficiency of the produced nanopowders.

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Abstract. In this study the photoacoustic spectroscopy was used to investigate the interaction between colloidal suspended nanosized maghemite particles and molecules present in mamona oil (ricinus communis L.). Maghemite nanoparticles were used to produce a magnetic fluid sample dispersed in mamona oil (MF-Mamona oil). In the L-band region (600 to 900 nm) of the photoacoustic spectra we found the photoacustic signal of sample MF-Mamona oil enhanced with respect to the signal of the purified mamona oil. This finding is claimed to be the signature of the strong interaction between the mamona oil's molecules and the solid surface provided by the suspended nanosized maghemite particles.