Effect of Growth Temperature on Chemical Synthesis of PbS quantum dots
P. K. Kalita *
Department of Physics, Nanoscience Research Laboratory, Guwahati College, Guwahati-781 021, Assam, India
B. Das
Department of Physics, Nanoscience Research Laboratory, Guwahati College, Guwahati-781 021, Assam, India
R. Devi
Department of Physics, Nanoscience Research Laboratory, Guwahati College, Guwahati-781 021, Assam, India
*Author to whom correspondence should be addressed.
Abstract
PbS quantum dots synthesized at room temperature through CBD technique show a large blue shift of absorption edge due to formation of very small particle size of the order of 2nm confirmed by HRTEM measurement. It exhibits a further blue shift when synthesized in acidic medium (pH 5.5) whereas a red shift for those synthesized in alkaline medium (pH 9.5) on rise of growth temperature up to 355K. PVA is found to play a key role in determination of quantum confinement. At high bath temperature the additional oxide phases that come into surface are also expected to influence the optoelectronic properties. Photoluminescence clearly exhibits UV emission at 360nm along with blue-green emissions at 470nm, 480nm, 490nm and 590nm owing to the doubly and singly ionized oxygen defects. The electrical conductivity in PbS nanocomposites may be attributed to the carrier tunneling process across the potential barriers created primarily between the PbS and oxide nanoparticles. The IR spectroscopy reveals the presence of oxides in PbS nanocomposites.
Keywords: PbS, lead oxides, high temperature bath, hyperbolic band structure