Optical and photocatalytic properties of ZnS:Mn nanocrystals

Abstract

The colloidal ZnS:Mn nanoparticles were obtained by using thermochemical method with the reaction duration varied from 1 h to 7 h. The bandgap of the ZnS:Mn nanocrystals increases from 3.75 eV to 4.06 eV with decreasing particle size from 5.8 nm to 2.4 nm, respectively. At room temperature, the ZnS:Mn nanoparticles exhibit orangered emission due to the 4T 1(4G) → 6A1(6S) transition within the 3d5 configuration of Mn2+ ions inside the ZnS host. The orange-red photoluminescence can be excited at energies corresponding to the Mn2+ ion own excited states. The 6A1(6S)→ 4E2( 4P); 6A1(6S)→ 4T2(4P); 6A1( 6S)→ 4E(4G), 4A 1(4G); 6A1(6S)→ 4T2(4G), and 6A1( 6S)→ 4T1(4G) absorption transitions have been observed in the photoluminescence excitation spectra. Photocatalytic properties of the samples have been investigated via absorption spectra of methyl orange (MO) in present of ZnS:Mn nanoparticles. The photo-degradation of MO obeys the pseudo-first-order kinetics law. The reaction rate constant k for MO degradation was 0.0065 min-1. © 2011 The Surface Science Society of Japan.