Materials and methods: All chemicals used are of analytical grade or of the highest purity available. All solutions were prepared with double-distilled, deionised water. Zinc acetate tetra hydrate, sodium sulfide (Na 2 S) and polyvinylpyrrolidone (PVP) and were purchased from Aldrich with high purity. Working standard solutions were prepared daily in deionised water. UV-Vis absorption spectra were acquired on a Jasco V-570 UV-Vis. spectrometer. Fluorescence spectra were recorded on a model

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... olog Horiba Jobin Yvon spectrofluorimeter at room temperature. IR spectra were measured with a Bruker Tensor-27 FT-IR spectrometer. Transmission electron micrograph (TEM) was recorded by JEOL, JEM-2100(200 kV). DLS measurements were performed using Nanotrac instrument. pH measurement were made by using model EQ-664 (Equip-tronics).