树枝状银微米材料的制备及其表面增强拉曼光谱研究

为使表面增量拉曼散射(SERS)衬底的制备方法简单快速且提高的基底增强效果，采用置换反应的制备方法，用锌片和硝酸银反应制备出微米银结构SERS活性基底，其具有稳定性好，易保存，制备方法简单，过程快速等特点。用扫描电子显微镜观察得银微米材料表面形貌呈均匀对称的树枝状结构。实验中控制置换反应的时间分别为40，50，60 s时，得到的树枝状银微米材料的长度分别为3，5，10 μm左右，分支分别为700 nm，2 μm，3 μm，发现随着置换反应的时间的增长，微米银树枝及分枝的长度越长，且树枝分枝上逐渐长出纳米级“树叶”结构, 使得微米级银树枝表面具有纳米结构。并且将微米银材料置于硅片上作为SERS衬底，并以罗丹明6G为探针分子，用激发波长为1 064 nm的傅里叶变换拉曼光谱仪检测，研究其在表面增强拉曼光谱中的应用，结果表明树枝状银微米材料有很好的SERS特性，其中置换反应时间为40 s时制备的微米银树枝的增强效果最佳，其增强因子可达到103左右，并且采用用表面活性剂PVP处理硅片的方法后，保持其他条件不变，微米银衬底的SERS增强效果得到进一步加强，增强因子达到104左右。此外，将树枝状银微米材料用水可封存数月，且实验结果的重复性较好。

Preparation and SERS Study of Silver Microstructures wi th Dendri tic Shape

In the surface ehanced Raman scattering (SERS) technology, not only to improve the making process of SERS substrates, to be fast and easily, but also to enhance the SERS enhance factor, an easy replacement reaction between zinc and silver nitrate solution has been adopted to prepare silver micro-structures SERS-active substrate. The silver micro-substrates have many advantages. These substrates have good stability, well preservation, an easy making method and a fast making process. The surface profile of the silver microparticles is investigated by scanning electron microscope (SEM). The silver microstructures are dendritic shape in a symmetrical fashion with symmetrical distribution. When the time of the replace reaction is 40, 50 and 60 s, respectively, the average lengths of “trunks” in the silver dendritic microsubstractes are about 3, 5 and 10 μm, and the lengths of the “branches” are about 700 nm, 2 μm and 3 μm, respectively. The result shows that the longer time the replacement reaction takes, the longer lengths of the “trunks” and “branches” in the silver dendritic microsubstractes become. With the time of replace reaction increasing, the “trunk” and “branch” in the silver dendritic microsubstractes grow longer and a large amount of nano-level “leaves” grow out from the “branches” of the silver dendritic microsubstractes, so the silver micro size dendrates have nano level structure on surface. In order to investigate the SERS-active substrates application in SERS, a Fourier transform Raman spectrograph with a 1 064 nm laser wavelength is used to measure the SERS spectra. And good SERS spectra have been obtained by using dendritic silver microsubstrates on the silicon chip as a SERS substract, and Rhodamine 6G (R6G) as a molecule probe. It is found that the silver micro-substrates have good Raman characteristics. And comparing these SERS spectra, it gets the conclution that the spectra with best SERS enhance effect are obtained when R6G is obsorbed on the silver dendritic micro-substractes whose preparing time is 40s, and at that time, the analytical enhancement factor for SERS signals is approximately 103. And when the silicon ships are dealed with surfactants Polyvinylpyrrolidone (PVP) and keeping the other conditions the same as before, the SERS enhance effect of the spectra becomes better, and the enhancement factor turn to be approximately 104. What’s more, the silver microstructures can be preserved several monthes under deionized water and the repeatment of the expriment result is well in general.