激光诱导金纳米棒图案化光纤SERS探针

研究了激光诱导沉积制备光纤表面增强拉曼散射（SERS）探针，并对探针的SERS性能进行检测。探讨光纤探针制备过程中金纳米棒溶液的浓度对探针灵敏度的影响。结果表明，将不同浓度的金纳米棒溶液进行激光诱导，在光纤端面会形成金纳米棒团簇和分散两种纳米结构。金纳米棒溶液的浓度、激光功率、诱导时间等因素都会对诱导沉积图案产生影响。实验利用功率为5 mW的激光进行诱导，在1.5×10-9，1.0×10-9和7.5×10-10 mol·L-1的金纳米棒溶液中，经5 min沉积，制备出不同图案的光纤SERS探针。采用晶种法合成金纳米棒，用透射电子显微镜（TEM）观察金纳米棒形貌，并根据TEM图像分析计算了合成金纳米棒的长径比约为3.8。用扫描电子显微镜（SEM）观察金纳米棒的形貌以及激光诱导沉积后的纤维修饰端形貌，7.5×10-10 mol·L-1的金纳米棒溶液进行激光诱导，金纳米棒在光纤端面分布较为分散，而1.5×10-9和1.0×10-9 mol·L-1的金纳米棒溶液进行激光诱导，光纤端面都有大量的金纳米棒聚集成团。以4-氨基苯硫酚（4-ATP）为样品分子，通过拉曼光谱对光纤探针的SERS性能进行检测；为了方便比较，选取了拉曼频移1 079.972 cm-1处的拉曼强度作图，结果表明，金纳米棒浓度为7.5×10-10 mol·L-1时，经激光诱导制备出的光纤探针性能较好。采用时域有限差分法(FDTD)模拟形成的图案的热点分布，进而解释了金纳米棒浓度为7.5×10-10 mol·L-1时制备的光纤探针性能较好的原因。为了检验光纤探针的重复性，将测试SERS光谱后的光纤浸入无水乙醇中24小时，使4-ATP充分溶解在酒精中，15天后，再次检测光纤探针的SERS检测性能，得到与之前检测同样的光谱图，证明得到的光纤SERS探针具有较强的可重复利用性。激光诱导制备光纤探针具有操作简单、成本低廉、探针制备时间短等优点，能够实现高灵敏度光纤SERS探针的重复、批量制备。

Au-Nanorod Patterned Optical Fiber SERS Probes Fabricated by Laser-Induction

In this paper, the preparation of an optical fiber surface-enhanced Raman scattering (SERS) probe by laser-induced deposition was studied, and the SERS performance of the probe was tested. The effect of the concentration of gold nanorod solution on the sensitivity of the optical fiber probe was discussed. The results show that two kinds of nanostructures——gold nanorod clusters and gold nanorod dispersion can be formed on the optical fiber facet by laser induction of gold nanorods with different concentrations. The induced deposition pattern is affected by the factors such as the concentration of gold nanorod solution, laser power and induction time. Induced by a laser with a power of 5 mw, SERS probes with different patterns were prepared in 1.5×10-9, 1.0×10-9 and 7.5×10-10 mol·L-1 gold nanorods solution after 5 min deposition. Synthesized by the crystal seed method, the morphology of gold nanorods was observed by transmission electron microscope (TEM). Moreover, the length-to-diameter ratio of the synthesized gold nanorods was about 3.8 according to TEM image analysis. The morphology of gold nanorods and fiber-modified ends after laser-induced deposition was observed with a scanning electron microscope (SEM). The distribution of gold nanorods on the fiber end surface was relatively dispersed in 7.5×10-10 mol·L-1 gold nanorod solution by laser induction, while induced by laser in 1.5×10-9 and 1.0×10-9 mol·L-1 gold nanorods solution, a large number of gold nanorods clustered at the end of the optical fiber. It is taking 4-Aminothiophenol (4-ATP) as the sample molecule, and the SERS performance of the optical fiber probe was detected by Raman spectrometer. In order to facilitate comparison, the Raman intensity at the Raman shift of 1 079.972 cm-1 was selected for mapping. The results showed that the laser-induced fiber probe performs better at a gold nanorod concentration of 7.5×10-10 mol·L-1. The pattern’s hot spot distribution was simulated by the FDTD (finite-difference time-domain) method, which further explained the better performance of the laser induced fiber probe prepared at the concentration of 7.5×10-10 mol·L-1 gold nanorods. To test the repeatability of the fiber probe, after the SERS spectrum was tested, the fiber was immersed in anhydrous ethanol for 24 hours to make 4-ATP fully dissolved in alcohol. 15 days later, the SERS detection performance of optical fiber probes was detected again, and the same spectrogram was obtained as that detected before, which proved that the obtained optical fiber SERS probes had strong reusability. The laser-induced preparation of fiber probes can realize the repeated and batch preparation of SERS probes with high sensitivity with simple operation, low cost, short preparation time and so on.