CHARACTERISTICS OF GLUTATHIONE-CAPPED ZNS NANOCRYSTALLITES

The titration of increasing equivalents of inorganic sulfide into pref ormed Zn-glutathione led to the appearance of UV/VIS spectral features attributable to ZnS nanocrystallites. Glutathione-ZnS complexes upon irradiation caused reduction of methylviologen confirming their semico nductor properties. Size-fractionation of glutathione-ZnS samples on a gel filtration column showed the formation of a range of complexes wh ose spectral properties were correlated with the sulfide content, The stoichiometry of Zn:glutathione increased from 1:2 to a maximum of abo ut 7:1 as the sulfide/Zn ratios increase from 0 to similar to 1.0 in Z n-glutathione complex indicating up to 14-fold increase in the Zn-bind ing capacity of glutathione upon sulfide incorporation. Spectral chara cteristics of GSH-capped ZnS nanocrystallites were significantly influ enced by pH and by the stoichiometry of Zn, sulfide and glutathione in the complex. Samples containing least glutathione and highest sulfide showed maximal luminescence at pH 6, whereas those with higher glutat hione and lower sulfide content showed maximal luminescence at pH 11. (C) 1997 Academic Press.