溶液pH对茶多酚纳米银生物制备及催化性能的影响

Effect of solution pH on the bio-preparation and catalytic properties of tea polyphenol nano-silver

用茶多酚提取物通过生物还原制备纳米银粒子,并讨论溶液pH对茶多酚纳米银生物还原制备的影响。纳米银溶液的紫外可见吸收光谱显示:茶多酚纳米银的SPR峰在412 nm处,提高溶液pH有利于提高茶多酚纳米银的产率。随着反应溶液pH的升高,茶多酚纳米银溶液的粒径分布向小粒径方向移动,平均粒径也有一定程度的下降。为了测定茶多酚纳米银的催化性能,以硼氢化钠为还原剂,C.I.直接橙26为目标降解物进行了催化还原降解实验。在不添加纳米银的条件下,硼氢化钠无法有效还原降解C.I.直接橙26;而在较高pH条件(pH=9.2)下制备的茶多酚纳米银粒子,由于平均粒径更小且产率更高,表现出更强的催化活性。反应27min后,C.I.直接橙26的降解率达到86%左右。

Nano-silver particles were prepared by bioreduction of tea polyphenol extract, and the effect of solution pH on the bioreduction preparation of tea polyphenol nano-silver was discussed. Ultraviolet-visible absorption spectra of nano-silver solution showed that the SPR peak of tea polyphenol nano-silver was at412 nm. Increasing the solution pH was beneficial to increase the yield of tea polyphenol nano-silver. With the increase of the pH of the reaction solution, the particle size distribution of tea polyphenol nano-silver solution moved to the direction of small particle size, and the average particle size also decreased to a certain extent. In order to determine the catalytic performance of tea polyphenols nano-silver, the catalytic reduction degradation experiments were carried out with sodium borohydride as reducing agent and C.I. direct orange26 as target degradation dye. Without adding nano-silver, sodium borohydride could not effectively degrade C.I.direct orange 26. However, silver nanoparticles of tea polyphenols prepared at higher pH(pH=9.2) showed stronger catalytic activity because of their smaller average particle size and higher yield. After 27 min of reaction, the degradation rate of C.I. direct orange 26 reached about 86%.