Effects of heat treatment on physical, microstructural and optical characteristics of PbS luminescent nanocrystals

The oxidation of lead sulfide (PbS) luminescent nanocrystals (NCs) considerably changes their luminescence characteristics. Hence, an understanding of the oxidation mechanism, the structure and properties of oxidized moieties is important. In this research, well-defined spherical PbS NCs were synthesized via a simple, effective and surfactant-free method and characterized. Then, the effects of heat treatment (at 250, 350, 450 and 550 °C) on the PbS NCs were investigated. The transmission electron microscope (TEM) micrographs of the synthesized PbS NCs revealed that they had a well-defined spherical morphology. In addition, the average crystallite size using Scherrer's formula was about 13 nm and the calculated lattice constant using Bragg's equation was 0.5950 nm, which was very close to the value in the standard card (JCPDS No. 5-592). Furthermore, the X-ray diffraction (XRD) revealed that the heat treatment of samples at temperatures of 250, 350,450 and 550 °C in air results in the formation of oxide sulfate phase of the compositions PbSO4 and PbO·PbSO4. The lattice parameter, crystallite size, average internal stress, micro-strain and optical properties of PbS NCs were calculated and correlated with the heat-treatment temperature.

The heat treatment of PbS nanoparticles results in the formation of oxide sulfate phase of the compositions PbSO4 and PbO·PbSO4, which considerably changed their luminescence and sensor characteristics. Figure optionsDownload as PowerPoint slideHighlights
► A simple, effective and surfactant-free procedure for synthesis of PbS NCs is used.
► Lattice constant was calculated 0.5950 nm, which is very close to the standard card.
► Oxidation of NCs considerably changes their semiconducting and sensor characteristics.
► The heat-treatment results in the formation of compositions PbSO4 and PbO·PbSO4.