Paper NM-WeP1
Quantum Confinement Effect and Photocatalytic Properties of Cu₄SnS₄ and Cu₄SnS₄-Au Quantum Dots

Wednesday, December 14, 2016, 4:00 pm, Room Mauka

We developed an improved hydrothermal method with water-oil two-phase reaction system to synthesize size-controllable and oil-soluble Cu₄SnS₄ (CTS) quantum dots (QDs). The formation and growth mechanism of CTS QDs was proved to proceed via three steps: nucleation of C₃₁S₁₆ nanoparticles, diffusion of Sn⁴⁺ into Cu₃₁S₁₆ nanoparticles and formation of regular hexagonal nanoprisms via Ostwald ripening. The water-oil interface plays an important role in controlling nuclei process and growth speed of CTS QDs. The average size and size distribution of CTS QDs can be controlled efficiently through adjusting the solvent ratio of toluene/water. Nearly monodisperse CTS QDs can be synthesized when the toluene volume is larger than 30 mL. More importantly, this improved hydrothermal method is a general and low cost method to synthesize not only chalcogenide based QDs but also other complex compound QDs. The blue-shift of absorption edge and broadening of Raman bands were observed due to the quantum confinement effect. The exciton Bohr radius of CTS QDs was calculated to be 3.3-5.8 nm by using the first principle calculation. We further use the CTS quantum dots as seeds to produce CTS-Au heterostructured nanoparticles. Such heterostructured nanoparticles are shown to have excellent photocatalytic properties.