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Zinc–Histidine as Nucleation Centers for Growth of ZnS Nanocrystals

2000; Elsevier BV; Volume: 272; Issue: 1 Linguagem: Inglês

10.1006/bbrc.2000.2712

1090-2104

Richard Kho, Nguyen Quang Liem, Claudia L. Torres-Martínez, Rajesh K. Mehra,

Nanocluster Synthesis and Applications

Histidine is a chelator of zinc, most notably in zinc-finger proteins (zinc coordinated by cysteine and histidine) and in hyperaccumulator plants. Sulfide incorporation into molecules containing metal–cysteinyl complexes has been shown to occur in vivo in certain yeasts, leading to enhanced metal tolerance. Demonstrated here for the first time is incorporation of sulfide into zinc–histidine, resulting in histidine–ZnS nanocrystals (NCs) having unique optical properties. Sulfide complexation occurred optimally at alkaline pH into zinc-(histidine)2 species, and UV/Vis absorption maxima were red-shifted as increasing sulfide addition occurred. Intermediate sulfide concentrations led to multiple, thermodynamically preferred NC species within a sample. Fluorescence of histidine–ZnS NCs was greater than ZnS prepared previously with cysteinyl peptides. Transmission electron microscopy and selected-area electron diffraction indicated hexagonal ZnS crystals having an average size of 4.2 nm. A photocatalytic application of histidine–ZnS NCs was shown by efficient degradation of p-nitrophenol and paraquat in the presence of UV irradiation.