Enhanced visible-light photocatalytic decomposition of malachite green over squaraines sensitized SnIn_4S_8 composites and effect of dye structure on photocatalytic behaviors

摘要

A series of indole squaraines (SQs) sensitized SnIn~(4)S~(8)particles with the mass ratio of 1:10 were fabricated by a facile ultrasonic method. The obtained samples have been characterized by X-ray diffraction, scanning electron microscopy, transmission electron microscopy, diffuse reflection spectroscopy, Fourier transforms infrared spectroscopy and Raman spectroscopy. The as-prepared squaraines/SnIn~(4)S~(8)composites exhibited the excellent thermal stability. The efficient charge-transfer ability of squaraines was calculated by Gaussian 98 at the B3YP/6-311 + G(d,p) level. The highest occupied molecular orbital and the lowest unoccupied molecular orbital states had been obtained to match the band gap of pure SnIn~(4)S~(8). The malachite green (MG) was used as the degradation dye to measure the photocatalytic performance of different SQs sensitized SnIn~(4)S~(8)composites. The results showed that the sensitized composites exhibited significantly enhanced photocatalytic activities. Among them, The BSQ/SnIn~(4)S~(8)composites showed the best photocatalytic performance whose degradation rate reached 97.91% under 40 min visible-light irradiation. The k~(app)value of BSQ/SnIn~(4)S~(8)composites (0.0962 min_(−1)) was 4.20 times larger than that of bare SnIn~(4)S~(8)(0.0229 min_(−1)). The k~(app)value of ISQ/SnIn~(4)S~(8), MSQ/SnIn~(4)S~(8), FSQ/SnIn~(4)S~(8)and CSQ/SnIn~(4)S~(8)was evaluated to be 0.0328, 0.0358, 0.0526 and 0.0192 min_(−1), respectively. According to the fluorescence spectra, BSQ/SnIn~(4)S~(8)possessed the highest fluorescence quantum yield of 0.4621 within all nanocomposites. Furthermore, the photocatalytic mechanism of squaraines/SnIn~(4)S~(8)composites was also proposed.