One-step synthesis of near-infrared emitting and size tunable CuInS2 semiconductor nanocrystals by adjusting kinetic variables

This paper aims to systematically optimize the preparation process of CuInS2 (CIS) QDs by intensively manipulating kinetic variables including reaction temperature, reaction time, In/Cu ratio and surface ligand. CIS QDs were synthesized using copper iodide and indium acetate in the presence of 1-octadecene (ODE) that was used as reaction solvent, while 1-dodecanethiol (DDT) was chosen as the sulfur source and surface ligand. UV-Vis spectroscopy and fluorescence spectroscopy were applied to reveal the growth kinetics and fluorescence properties of CIS QDs. Transmission electron microscopy and X-ray diffraction were utilized to characterize the size, morphology and crystal structure of the final products. Our results reveal that the emission wavelength of CIS QDs could be found at visible light and near-infrared regions ranging from 630 to 825 nm. By scrupulous regulation of the reaction temperature, reaction time and the amount of DDT, highly dispersed and stable hydrophobic CIS QDs could be prepared directly without any further modification by one-step method. The fluorescence intensity could be enhanced by introducing Cu defects with the fluorescence quantum yield (QY%) reaching around 7%, while the particle size could be tuned from ultra-small sizes approaching 1.5 nm to 4 nm, by controlling the In/Cu ratio.