High-pressure solvothermal route to synthesize II–VI sulfide compounds

We report a new solvothermal synthesis process for CdS and ZnS nanostructures involving dissociation of a known oxygen scavenger sodium sulfite (Na2SO3) into hydrogen sulphide under high pressure. Hydrogen sulphide subsequently provides the necessary S2− ions for the formation of the sulfide compounds in a mixed solvent consisting of ammonia, hydrazine hydrate and de-ionized water along with the precursor salt for Cd/Zn ions in the respective synthesis. X-ray diffraction (XRD) measurements show characteristic peaks with large full-width at half maxima (FWHM) corresponding to the wurtzite phase in the case of CdS nanoparticles and the zinc blende phase in the case of ZnS nanoparticles. Raman spectra for the two samples show a strong characteristic LO phonon modes of CdS and ZnS in the respective samples. Elemental compositional analysis with energy dispersive X-ray analysis (EDX) also indicates formation of the compounds. Field emission scanning electron microscope (FESEM) and Transmission electron microscope (TEM) images show nanorods formation in the case of CdS and nanospheres in ZnS. High resolution transmission electron microscope (HRTEM) images show crystal diffraction planes corresponding to (100) plane in CdS and (111) plane in ZnS nanoparticles.