†School of Chemical and Biomedical Engineering, Nanyang Technological University, Singapore 637457, Singapore.
‡School of Energy and Chemical Engineering, Ulsan National Institute of Science and Technology (UNIST), 50 UNIST-gil, Ulsan 689-798, South Korea.
ACS Appl Mater Interfaces. 2015 Jul 15;7(27):14793-800. doi: 10.1021/acsami.5b03109. Epub 2015 Jul 2.
We developed a route for synthesizing Ag nanostructures with tunable morphologies for ultrasensitive surface-enhanced Raman spectroscopy. Through the consecutive addition of three reducing agents (i.e., 4-mercaptobenzoic acid, trisodium citrate, and ascorbic acid) to an aqueous solution of silver nitrate, hierarchical flower-like Ag nanostructures were produced. The nanostructures had Ag petals in which nanosized gaps were generated, and small Ag nanoparticles were incorporated within the gaps. Theoretically, the nanostructures exhibited highly enhanced electric fields in the outer-shell regions where the small Ag nanoparticles were densely located. Combining the enhanced field effect with resonance effect of a Raman-active molecule (methylene blue) at a specific wavelength, measurable Raman signals were obtained at concentrations as low as 100 attomolar (10(-16) M; corresponding to 10(-21) mol). Key factors were discussed for the synthesis of the Ag nanostructures while finely controlling the morphologies of hierarchical Ag nanostructures, thereby modulating the intensity of surface-enhanced resonance Raman spectroscopy (SERRS) signals. Therefore, this synthetic method produces highly promising nanostructures for SERRS-based applications.
我们开发了一种合成具有可调形态的银纳米结构的路线，用于超灵敏的表面增强拉曼光谱。通过连续向硝酸银水溶液中添加三种还原剂（即 4-巯基苯甲酸、柠檬酸钠三钠和抗坏血酸），制备出具有分层花状形貌的银纳米结构。这些纳米结构的银花瓣中产生了纳米级间隙，并且在间隙内嵌入了小的银纳米颗粒。从理论上讲，这些纳米结构在外壳区域表现出高度增强的电场，其中小的银纳米颗粒密集分布。将小的银纳米颗粒的局域表面等离子体共振效应与特定波长的拉曼活性分子（亚甲基蓝）的共振效应相结合，在低至 100 飞摩尔（10^(-16) M；相当于 10^(-21) mol）的浓度下即可获得可测量的拉曼信号。我们讨论了影响银纳米结构合成的关键因素，同时精细控制了分级银纳米结构的形态，从而调节了表面增强共振拉曼光谱（SERRS）信号的强度。因此，这种合成方法为基于 SERRS 的应用提供了极具前景的纳米结构。
