Tuning the optical and photocatalytic properties of anisotropic ZnS nanostructures for the selective reduction of nitroaromatics

Hexagonal ZnS nanorods (L x W = similar to 60 nm x similar to 4 nm and surface area = 59.1 m(2) g(-1)) and cubic ZnS nanoflowers (diameter = similar to 70 nm and surface area = 65.2 m(2) g(-1)) like nanocrystals have prepared and investigated their relative optical and photocatalytic properties for the selective reduction of (m, p)-dinitrobenzene to (m, p)-nitroaniline. The band edge absorption at 325 nm (3.72 eV) of nanoflowers, 354 nm (3.52 eV) of nanorods are significantly red-shifted, and photoluminescence is notably quenched after 1 wt% Au and Pt loading due to exciton-Plasmon's interactions. It revealed for the first time that bare and Au/Pt deposited ZnS nanostructures exhibited highly improved photocatalytic activity for the selective reduction of (m, p)-dinitrobenzene to (m, p)-nitroaniline (>90 yield) formation under UV (125 W Hg arc, 10.4 mW/cm(2)) light irradiation for 8 h. This observed photoactivity is attributed to the size and shape dependent changes in band edge position relative to bulk ZnS, suitable reduction potential (-0.48 eV) of -NO2 group and favorable Fermi energy/electron accepting states of Au/Pt lying below the conduction band position of as-prepared ZnS nanoparticles. (C) 2014 Elsevier B.V. All rights reserved.