Template-free syntheses of hierarchical PbS microstructures using a new sulphur source and their time-dependent morphological evolution and photocatalytic properties

Abstract

Template-free lead sulphide (PbS) microstructures composed of nanocrystals exhibiting time-dependent morphological evolution from cubes to dendrites (S1-S5) were synthesised by a one-pot solvothermal route using dibenzyl disulphide (DBDS = (C7H7S)2) as a new temperature controlled in situ source of S2- ions. Use of mercaptoethanol (MCE) capping agent resulted in the formation of PbS microstructures (S6-S10) with mainly dendritic morphology as the major phase. Powder X-ray diffraction measurements unveiled the cubic structure of the PbS microstructures. FESEM analyses of the uncapped PbS microstructures (S1-S5) obtained at different time intervals revealed time-dependent morphological evolution from cubic to dendritic structures, whereas the MCE-capped PbS microstructures show the formation of mostly dendritic structures. The possible mechanism of the morphological evolution of PbS microstructures in the presence and absence of MCE capping agent has been discussed. Optical measurements of the samples show a blue-shift in the absorption maxima in comparison to that of bulk PbS and the estimated band gap values are in the range of 3.5-3.8 eV. Photocatalytic investigation of cubic and dendritic microstructures for the degradation of MO revealed a higher catalytic activity of dendrites over cubes. The relatively higher activity of dendrites has been attributed to the higher charge transfer originating due to the branched nature of dendrites. Thus the influence of capping agent on the morphological evolution and the photocatalytic activity of PbS hierarchical structures has been presented.