Electrochemical synthesis and optical properties of ultra-fine CdSe nanoparticles

Colloidal solutions (similar to 0.3 mol/L) of CdSe nanoparticles in xylene have been synthesized by the electrochemical method from an acid electrolyte based on HNO3 + HCl (2:1) mixture using extraction into xylene. It has been found that CdSe nanoparticles of small size (2-5 nm) synthesized on the cathode are readily extractable in xylene, whereas nanoparticles of larger size (20-100 nm) remain in the aqueous electrolyte and dissolve in the nitric-hydrochloric acids mixture. An X-ray phase analysis of powders of 2-5 nm CdSe nanoparticles showed them have a mixed cubic/hexagonal crystal structure. It has been found from measurements of absorption and photoluminescence spectra that the CdSe nanoparticles of this structure have a broad photoluminescence band (lambda (max) = 500 nm) at a narrow absorption peak (lambda (max) = 420 nm), which may be due to stacking fault formation in nanoparticles of mixed cubic/hexagonal structure. Using this electrolyte with a xylene surface layer under continuous electrolysis conditions and extraction of 2-5 nm CdSe nanoparticles with a content of up to 0.05 g in 1 cm(3) xylene (similar to 0.3 mol/L) was obtained. Such colloidal solution can be used to obtain optical nanocomposites by incorporation CdSe nanoparticles into a liquid-crystalline cadmium caprylate matrix. The spectral characteristics such of composites have been studied by adsorption spectroscopy and fluorescence.