Solvothermal synthesis of InP quantum dots and their enhanced luminescent efficiency by post-synthetic treatments

Abstract

InP quantum dots (QDs) were solvothermally synthesized by using a greener phosphorus source of P(N(CH 3) 2) 3 instead of highly toxic P(TMS) 3 widely used, and subsequently subjected to a size-sorting processing. While as-grown QDs showed an undetectably low emission intensity, post-synthetic treatments such as photo-etching, photo-radiation, and photo-assisted ZnS shell coating gave rise to a substantial increase in emission efficiency due to the effective removal and passivation of surface states. The emission efficiency of the photo-etched QDs was further enhanced by a consecutive UV photo-radiation, attributable to the photo-oxidation at QD surface. Furthermore, a relatively thick ZnS shell on the surface of InP QDs that were surface-modified with hydrophilic ligands beforehand was photochemically generated in an aqueous solution at room temperature. The resulting InP/ZnS core/shell QDs, emitting from blue to red wavelengths, were more efficient than the above photo-treated InP QDs, and their luminescent properties (emission bandwidth and quantum yield) were comparable to those of InP QDs synthesized with P(TMS) 3. Structural, size, and compositional analyses on InP/ZnS QDs were also conducted to elucidate their core/shell structure.