Infrared to visible up-conversion in biocellulose yttrium vanadate nanoparticle composite membranes. Demonstration of chloroaluminum phthalocyanine light emission under up-converted light excitation
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YVO4:(Yb3 +–Er3 +/Ho3 +) nanoparticles were incorporated in biocellulose membranes obtained from Gluconacetobacter xylinus. Materials present the property of converting near-infrared (NIR) into higher-energy visible light. Nanoparticles were prepared by optimizing towards higher emission intensity at the absorption wavelength range of chloroaluminum phthalocyanine (ClAlPc) used as a photosensitizer in the photodynamic therapy. The NIR excitation wavelength is advantageous for biological applications, as it allows deeper penetration into tissues than the UV–visible radiation commonly used for luminescence excitation. Up-conversion emission spectra obtained under excitation at 980 nm showed a preferential green emission for the Yb3 +–Er3 + system and a red emission for the Yb3 +–Ho3 + one. In the last case, by using mixtures of nanoparticles and ClAlPc the red emission (680 nm) of the phtalocyanine was observed through excitation by the up-converted emission of the nanoparticles (650 nm) which were excited in NIR (980 nm).