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KCa 2 Ta 3-x Nb x O 10 samples were synthesized by solid-state reaction and evaluated on the hydroxylation of terephthalic acid under UVC irradiation. Computational simulations via DFT were carried out in order to study their structural and electronic properties. Theoretical results show good agreement with experimental data, regarding lattice parameters and band-gap energy values and indicated that the photocatalytic performance for hydroxyl radicals production is directly related to the degree of octahedral distortions in these materials.

This paper presents a low-cost reflectometer for selective detection of Cu 2+ . The reflectometer is based on an emission light source using five light-emitting diodes at different wavelengths and a detector using a webcam. The samples were prepared using a filter paper-based colorimetric sensor with ascorbic acid-based quinoxaline derivative. Video analysis using gray color intensity was used to perform both copper ion screening ( ) and quantification of Cu 2+ in spiked samples. In addition, a multivariate validation was performed. The system proved to be selective to Cu 2+ among the screened ions, and its quantification was performed using partial least square regressions. Good linearity (R 2 = 0.979, coefficient of determination), low root-mean-square error of prediction (RMSEP = 5.20 × 10 -3 mol L -1 ) and high recovery (93.39-128.64%) were achieved. This method has potential to be employed for rapid and selective determination of Cu 2+ in water using low-cost instrumentation.