State Key Laboratory of Physical Chemistry of Solid Surfaces and College of Chemistry and Chemical Engineering, Xiamen University, Xiamen, 361005, China.
Langmuir. 2012 Jun 19;28(24):9140-6. doi: 10.1021/la3005536. Epub 2012 May 11.
Au-seed Ag-growth nanoparticles of controllable diameter (50-100 nm), and having an ultrathin SiO(2) shell of controllable thickness (2-3 nm), were prepared for shell-isolated nanoparticle-enhanced Raman spectroscopy (SHINERS). Their morphological, optical, and material properties were characterized; and their potential for use as a versatile Raman signal amplifier was investigated experimentally using pyridine as a probe molecule and theoretically by the three-dimensional finite-difference time-domain (3D-FDTD) method. We show that a SiO(2) shell as thin as 2 nm can be synthesized pinhole-free on the Ag surface of a nanoparticle, which then becomes the core. The dielectric SiO(2) shell serves to isolate the Raman-signal enhancing core and prevent it from interfering with the system under study. The SiO(2) shell also hinders oxidation of the Ag surface and nanoparticle aggregation. It significantly improves the stability and reproducibility of surface-enhanced Raman scattering (SERS) signal intensity, which is essential for SERS applications. Our 3D-FDTD simulations show that Ag-core SHINERS nanoparticles yield at least 2 orders of magnitude greater enhancement than Au-core ones when excited with green light on a smooth Ag surface, and thus add to the versatility of our SHINERS method.
我们制备了具有可控直径（50-100nm）的 Au 种子 Ag 生长纳米颗粒，并具有可控厚度（2-3nm）的超薄 SiO2 壳，用于壳层隔离纳米粒子增强拉曼光谱（SHINERS）。对其形态、光学和材料性能进行了表征；并通过吡啶作为探针分子进行了实验研究，通过三维有限差分时域（3D-FDTD）方法进行了理论研究，研究了它们作为多功能拉曼信号放大器的潜在应用。我们表明，可以在纳米颗粒的 Ag 表面上无针孔地合成厚度仅为 2nm 的 SiO2 壳，然后将其用作核。介电 SiO2 壳用于隔离增强拉曼信号的核，并防止其与被研究的系统相互干扰。SiO2 壳还可以阻止 Ag 表面的氧化和纳米颗粒的聚集。它显著提高了表面增强拉曼散射（SERS）信号强度的稳定性和重现性，这对于 SERS 应用至关重要。我们的 3D-FDTD 模拟表明，在光滑 Ag 表面上用绿光激发时，Ag 核 SHINERS 纳米颗粒的增强至少比 Au 核大两个数量级，从而增加了我们的 SHINERS 方法的多功能性。
