Guo Pengzhen, Sikdar Debabrata, Huang Xiqiang, Si Kae Jye, Xiong Wei, Gong Shu, Yap Lim Wei, Premaratne Malin, Cheng Wenlong
Department of Physics, Harbin Institute of Technology, Harbin, Heilongjiang Province 150080, P.R. China.
Nanoscale. 2015 Feb 21;7(7):2862-8. doi: 10.1039/c4nr06429a.
We systematically investigated the size- and shape-dependent SERS activities of plasmonic core-shell nanoparticles towards detection of the pesticide thiram. Monodisperse Au@Ag nanocubes (NCs) and Au@Ag nanocuboids (NBs) were synthesized and their Ag shell thickness was precisely adjusted from ∼1 nm to ∼16 nm. All these nanoparticles were used as SERS substrates for thiram detection, and the Raman intensities with three different lasers (514 nm, 633 nm and 782 nm) were recorded and compared. Our results clearly show that: (1) the excitation wavelength discriminated particle shapes regardless of particle sizes, and the maximized Raman enhancement was observed when the excitation wavelength approaches the SERS peak (provided there is significant local electric field confinement on the plasmonic nanostructures at that wavelength); (2) at the optimized laser wavelength, the maximum Raman enhancement was achieved at a certain threshold of particle size (or silver coating thickness). By exciting particles at their optimized sizes with the corresponding optimized laser wavelengths, we achieved a detection limit of roughly around 100 pM and 80 pM for NCs and NBs, respectively.
我们系统地研究了等离子体核壳纳米粒子的尺寸和形状依赖性表面增强拉曼散射（SERS）活性，用于检测农药福美双。合成了单分散的金@银纳米立方体（NCs）和金@银纳米长方体（NBs），并将其银壳厚度从约1nm精确调整到约16nm。所有这些纳米粒子都用作福美双检测的SERS基底，并记录和比较了三种不同激光（514nm、633nm和782nm）下的拉曼强度。我们的结果清楚地表明：（1）激发波长能区分粒子形状，而与粒子尺寸无关，当激发波长接近SERS峰时观察到最大的拉曼增强（前提是在该波长下等离子体纳米结构上存在显著的局部电场限制）；（2）在优化的激光波长下，在一定的粒子尺寸（或银涂层厚度）阈值处实现了最大的拉曼增强。通过用相应的优化激光波长激发处于优化尺寸的粒子，我们分别实现了NCs和NBs约100pM和80pM的检测限。
