Preparation And Characterization Of MSe₂（M=Cu, Ni） Diselenides By Polyol Based Solution Chemical Process

Transition metal dichalcogenides MX2(M=Fe, Co, Ni, Cu, Zn; X=S, Se) withcubic pyrite structure have attracted considerable attention for the fields of MaterialsScience, Physics and Chemistry Sciences due to their unique electronic, magnetic andoptical properties. In this dissertation, monodispersed, octahedral-shaped CuSe2andstar-shaped NiSe2particles were first prepared by an air pressure polyol basedsolution process using triethyleneglycol as solvent, triethylenetetramine as assistingagent, polyvinylpyrrolidone as capping agent. Influence of reaction temperature,refluxing time, precursor concentration, M/Se ratio, triethylenetetramine and PVPaddition was investigated, and the products were characterized by XRD, FESEM,HRTEM, EDS, XPS, ICP-MS, Raman, UV–Vis-NIR measurements.The synthesis process used CuCl22H2O and Se powder as reactants, triethyleneglycol (TEG) as solvent, triethylenetetramine (TETA) as basic assisting agent andpolyvinylpyrrolidone (PVP) as capping agent. Monodispersed, octahedral-shapedCuSe2particles with edge length of～450nm were obtained by hot injection process,and possible mechanism was discussed. The research results showed that (a) purepyrite CuSe2could be formed at relatively low temperature because the mixed phaseof pyrite and marcasite tended to be produced at high synthetic temperature.(b) Phasecomposition and morphology of the products were not sensitive to precursorconcentration.(c) Optimal TETA adding amount was0.005ml, and Se species couldnot be reduced adequately at below the amount while Se species was easy to bereduced to Se2-partially to form CuSe phase at above the amount.(d) PVP addedamount was not sensitive to final size and octahedral morphology of CuSe2. Also,influence of precursor atomic ratio in feeding solution, synthetic temperature on phasecomposition and growing morphology was investigated.The synthesis process used NiCl2·6H2O and Se powder as reactants, TEG assolvent and PVP as capping agent. Star-shaped NiSe2particles were obtained by hotinjection process. The research results showed that (a) the synthesis of NiSe2wasdifferent from that of CuSe2. The optimal reaction temperature was230oC. Pure pyriteNiSe2could be obtained at relatively high temperature, while the mixed phase ofpyrite and marcasite was synthesized at low reaction temperature.(b) The optimalNi/Se atomic ratio in feeding solution was1:2, and the mixed phase of pyrite andmarcasite NiSe2was easy to be formed when deviated from the stoichiometric ratio, which needed to be studied in the future.