L-cysteine-assisted Reverse-microemulsion Synthesis Of Nanosufildes

Photocatalytic water splitting into H₂using solar energy is considered to be one of the mostideal approaches to address energy and environmental problems. Many transition metalsulfides exhibit strong absorption in the visible region and have potential applications as acatalyst in photo-catalytic H₂production. As is known, L-cysteine contains-SH,-NH₂,-COOH functional groups, which has a strong affinity to metal cations to form metal-ligandcomplexes and is now attracting much attention to be a template to generate various metalsulfide nanostructures. This thesis focuses on the synthesis and assemply of sulfide/sulfidenanoheterojunction composite by an L-cysteine-assisted reverse-microemulsion route, andobtained main results as follows:1. Ag₂S nanoparticles with a diameter of10⁵0nm has been successfully synthesized in aTriton X-100/cyclohexane/hexanol/water quaternary micelle solution in the presence ofNa₂S·9H₂O as a sulfur source and L-cysteine as a chelating ligand. The influence of syntheticparameters such as sulfur source, the kinds of chelating ligands, water/oil ratio, Ag⁺/L^-cysteine molar ratio, aging time and the concentrations of reactants on the morphology, sizeand propterites of Ag₂S nanoparticles was investigated.2. L-cysteine-assisted reverse-microemulsion method was extended to the synthesis ofAg₂S/CdS nanoheterojunction. Firstly, CdS nanorods were prepared by a slovothermalmethod. Subsequently, Ag₂S/CdS nanoheterojunction was slowly assemblied via acation-exchange approach in a Triton X-100/cyclohexane/hexanol/water micelle solutionbased on the difference of Ksp value between Ag₂S and CdS. The products were characterizedby XRD, TEM, HRTEM, EDX, map of elements, XPS and Uv-Vis absorption specta. Apossible growth mechanism for the formation of and UV-vis diffuse reflectance absorptionspectra. Ag₂S/CdS nanoheterojunction was also proposed.3. Chain-like MoS₂assemblies consisting of hexagonal MoS₂nanoparticles （20–60nm）have been successfully synthesized in a Triton X-100/cyclohexane/hexanol/water W/Oreverse microemulsion in the presence of （NH₄）₂MoS₄as the molybdenum source andNH₂OH·HCl as the reducing agent. The as-prepared chain-like MoS₂nanoparticles exhibitedexcellent photocatalytic H₂activity in Ru（bpy）²⁺-MoS₂-H₂A three-component molecularsystems under visible light irradiation.4. MoS₂/MWCNT nano-composites were also synthesized via a W/O microemulsionprocess.