电解法制备纳米银溶胶及其SERS活性研究

分别用柠檬酸三钠溶液、硝酸银和聚乙烯醇混合液作为电解液,用银棒作为电极,加上7 V直流电压,通电1 h,用电解方法得到了纳米银溶胶.为测试该纳米银溶胶是否具有表面增强拉曼散射1(SERS)活性,选用了阳离子型分子碱性品红(Fucllsine basic)、亚甲基蓝(Methylene blue),阴离子型分子苯甲酸(Benzoic acid),甲基橙(Methyl orange)、中性分子吖啶橙(Acidine orange)、苏丹红(Sudan red)作为测试分子,进行SERS研究,结果发现用两种电解液制备的纳米银都具有很强的SERS活性,但用硝酸银和聚乙烯醇混合液作为电解液制备的纳米银溶胶具有更广泛的SERS活性.在该方法制备的纳米银上,得到了在常规方法制备的胶态纳米银上及用柠檬酸三钠溶液作为电解液制备的纳米银上得不到的甲基橙分子的SERS谱,对可能的原因进行了讨论.

Nano-Silver Colloids Prepared by Electrolysis and Research on Its SERS Activity

Three kinds of nano-silver colloids have been prepared by electrolysis of silver rod using sodium citrate solution and AgNO3 mixed with polyvinyl alcohol solution as electrolyte and applying 7 V direct current for one hour. Nano-silver colloids have been investigated by means of TEM, absorption spectrum, electrophoresis experiment and SERS. The particle size ranges roughly from 20 nm to 25 nm (spheroid) for sample 1, from 20 nm to 35 nm (spheroid) for sample 2, and from 30 to 80 (many-sided) for sample 3, featuring absorption maximum at 404, 421 and 434 nm, respectively. The surface charge of these three kinds of colloidal silver particles is positive. In order to test if these nano-silver colloids can be used for SERS research, the cationic molecular fuchsine basic, methylene blue, anionic molecular benzoic acid, methyl orange, neutral molecular alcidine orange, and Sudan red were used. It was found that these nano-silver colloids have strong SERS activity. Furthermore, the nano-silver colloids that used AgNO3 mixed with polyvinyl alcohol solution as electrolyte has the strongest SERS activity among all the tested molecules. The SERS of methyl orange has been obtained on the nano-silver colloids, which has not been obtaind on the colloids prepared by electrolysis of silver rod using sodium citrate solution and on the gray and yellow silver colloids prepared by traditional means. The possible reason has been explained. One major advantage of this method (using AgNO3 mixed with polyvinyl alcohol solution as electrolyte) is the absence of the spectral interference.