Development of a Synthesis of Quantum-Confined, Wurtzite CuInS2 Nanoparticles
Howard, Bryson Charles
CuInS2 is a ternary semiconductor material with potential alternative energy applications in photovoltaic devices and in systems designed for photocatalytic water reduction. To date, the majority of research into CuInS2 nanoparticles has focused on those that possess the thermodynamically favored chalcopyrite crystal structure. Wurtzite, the kinetically favored crystal structure, is exclusively seen in nano-structures, and has been significantly less studied. The synthesis of “large” wurtzite CuInS2 nano-disks has already been established, but the particles show energetic imperfections. This study details the development of a synthesis that produces sub-4 nm, quantum-confined, wurtzite CuInS2 nanoparticles that show emission near the band gap, a unique observation for wurtzite CuInS2. The particles are produced using a hot-injection method using metal salts as precursors. The structure and properties of these particles were detailed via absorbance and fluorescence spectroscopy, transmission electron microscopy, powder X-Ray diffraction, and inductively coupled plasma optical emission spectroscopy. Attempts were then made to develop a modified synthesis by which the band gap and size of the particles could be controllably manipulated. These efforts culminated in the addition of oleic acid to the reaction mixture, which showed promising initial results. Continued investigation into these quantum-confined wurtzite CuInS2 particles revealed some of the inherent inconsistencies of the synthesis developed in this study. The future work of this project will focus on understanding and explaining the apparent variability in the properties of the particles produced by this synthesis.