Li Qing-yu, Li Shi-rong, Si Min-zhen, Zhang Peng-xiang
Department of Basic Courses, Southwest Forestry College, Kunming 650224, China.
Guang Pu Xue Yu Guang Pu Fen Xi. 2007 Feb;27(2):299-301.
Negatively charged colloidal nano-silver particles were prepared by the colloidal chemical method. A 1.7% solution of silver nitrate (2 mL) was diluted with deionized water to 100 mL. A 1% solution of tannic acid (1 mL) was added dropwise to the solution stirring, then a 1% solution of potassium carbonate anhydrous (3-4 drops) was added to the mixed solution. Finally, a red-brown silver sol was obtained. It was testified that the silver sol is a negatively charged colloid by experiment of electrophoresis. The negative silver colloids (for short, old NCS) were kept on at the room temperature two year ago in order to test its SERS and stability. The sizes of particles were determined by Hitachi H-800 transmission electron microscope. Absorption spectroscopy and SERS were used to determine the main properties. Absorption spectra were obtained with UV-2401PC. Raman spectra were recorded with RENISHAW MIK 2000 Raman micro-spectroscopy. The 514.5 nm line of an argon ion laser with about 3 mw was used. Compared with the newly prepared negative silver colloids (for short, new NCS). It was found that the mean diameter of the old NCS was larger than the new NCS; old NCS had absorption maximum at 431 nm but new NCS at 418 nm, the absorbance spectrum of old NCS had a 12 nm red shift, and the red shift rate is about 0.5 nm/month; Both strong SERS spectra were observed when cationic molecules of fuchsine basic and neutral molecules of alcidine orange adsorbed on old NCS and new NCS. For cationic molecules of methylene blue, the SERS is stronger on new NCS than old NCS; but no SERS was observed for the anionic molecule of benzoic acid both on new NCS and on old NCS.
采用胶体化学方法制备了带负电荷的胶体纳米银颗粒。将1.7%的硝酸银溶液（2 mL）用去离子水稀释至100 mL。在搅拌的溶液中逐滴加入1%的单宁酸溶液（1 mL），然后向混合溶液中加入1%的无水碳酸钾溶液（3 - 4滴）。最后，得到红棕色的银溶胶。通过电泳实验证明该银溶胶是带负电荷的胶体。两年前将负电荷银胶体（简称老NCS）在室温下保存，以测试其表面增强拉曼散射（SERS）和稳定性。用日立H - 800透射电子显微镜测定颗粒尺寸。用吸收光谱和SERS来确定主要性质。用UV - 2401PC获得吸收光谱。用雷尼绍MIK 2000拉曼显微镜光谱仪记录拉曼光谱。使用波长为514.5 nm、功率约为3 mw的氩离子激光谱线。与新制备的负电荷银胶体（简称新NCS）相比，发现老NCS的平均直径大于新NCS；老NCS在431 nm处有吸收最大值，而新NCS在418 nm处，老NCS的吸收光谱有12 nm的红移，红移速率约为0.5 nm/月；当碱性品红阳离子分子和碱性藏红中性分子吸附在老NCS和新NCS上时，都观察到了强烈的SERS光谱。对于亚甲基蓝阳离子分子，新NCS上的SERS比老NCS上的更强；但在新NCS和老NCS上均未观察到苯甲酸阴离子分子的SERS。
