The surface-enhanced Raman spectroscopy (SERS) signal of a reporter on silver nanoparticles can be effectively gained by gradient electric field application. The external electric field initiates the dielectrophoresis of nanoparticles and their electrically induced dipole–dipole interaction. Owing to dielectrophoresis, the nanoparticles are concentrated in the area of high electrical field strength. The induced dipole–dipole interaction leads to additional coagulation of nanoparticles and formation of hotspots. Both dielectrophoresis and induced dipole–dipole interaction increase the number of hotspots, which leads to a SERS signal growth. These two mechanisms of SERS signal amplification are explained by the dielectrophoresis and Derjaguin–Landau–Verwey–Overbeek theories. The benefits of the surface-enhanced Raman spectroscopy in tandem with the gradient electric field are experimentally confirmed using a SERS-active reporter, 4-mercaptophenylboronic acid which has a characteristic peak at Raman shift of 1586 cm−1, conjugated to silver nanoparticles of 32, 52, 58, and 74 nm in diameter. The SERS signal gain depends on the silver nanoparticle stability, size, and electric field strength. The limit of detection for 4-mPBA in the system under study can be calculated from the concentration plot and equals to 63 nM. The enhancement factor calculated for SERS in tandem with the gradient electric field can reach 106. Graphical abstract

中文翻译：

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表面增强拉曼光谱与 4-巯基苯基硼酸在银纳米颗粒上的梯度电场串联

应用梯度电场可以有效地获得银纳米颗粒上报告分子的表面增强拉曼光谱 (SERS) 信号。外部电场引发纳米粒子的介电泳及其电诱导的偶极-偶极相互作用。由于介电泳，纳米颗粒集中在高电场强度区域。诱导的偶极-偶极相互作用导致纳米颗粒的额外凝结和热点的形成。介电泳和诱导偶极-偶极相互作用都会增加热点的数量，从而导致 SERS 信号增长。这两种 SERS 信号放大机制可以通过介电泳和 Derjaguin-Landau-Verwey-Overbeek 理论来解释。表面增强拉曼光谱与梯度电场串联的好处通过实验证实，使用 SERS 活性报告基因，4-巯基苯基硼酸在拉曼位移为 1586 cm-1 处具有特征峰，与 32 的银纳米粒子共轭、52、58 和 74 nm 的直径。SERS 信号增益取决于银纳米粒子的稳定性、大小和电场强度。所研究系统中 4-mPBA 的检测限可以从浓度图计算，等于 63 nM。与梯度电场串联计算的 SERS 增强因子可达 106。 图文摘要 与直径为 32、52、58 和 74 nm 的银纳米粒子结合。SERS 信号增益取决于银纳米粒子的稳定性、大小和电场强度。所研究系统中 4-mPBA 的检测限可以从浓度图计算，等于 63 nM。与梯度电场串联计算的 SERS 增强因子可达 106。 图文摘要 与直径为 32、52、58 和 74 nm 的银纳米粒子结合。SERS 信号增益取决于银纳米粒子的稳定性、大小和电场强度。所研究系统中 4-mPBA 的检测限可以从浓度图计算，等于 63 nM。与梯度电场串联计算的 SERS 增强因子可达 106。 图文摘要