Synthesis, Characterization, and 3D-FDTD Simulation of Ag@SiO₂ Nanoparticles for Shell-Isolated Nanoparticle-Enhanced Raman Spectroscopy

Abstract

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.

Shell‐Isolated Nanoparticle‐Enhanced Raman Spectroscopy (SHINERS)

“…The SPR absorption band maximum can be tuned to the near-infrared by adjusting the nanorod aspect ratio, which is essential for biosensor applications. SHINs with a mostly Ag core instead of an Au core were synthesized (Figure 8.6e) [62] because of the greater surface plasmon efficiency on Ag rather than on Au, and the SPR of Ag nanostructures can be forced to any wavelength in the visible region of the spectrum. We take 55 nm Au@SiO 2 SHINs as a typical example to describe the detailed experimental procedure of making the core-shell NPs.…”

“…We call this new technique "shell-isolated nanoparticle-enhanced Raman spectroscopy" (SHINERS) [45][46][47], which very recently has been applied successfully to several systems. [45][46][47][52][53][54][55][56][57][58][59][60][61][62][63].…”

Electrospray surface-enhanced Raman spectroscopy (ES-SERS) for probing surface chemical compositions of atmospherically relevant particles

“…Figure 1 shows a comparison of approaches using an SERS substrate with pre-deposited metal nanoparticles and our proposed method of depositing metal nanoparticle aerosols on collected analyte particles. Deposition of metal nanoparticle aerosols on an analyte particle creates SERS-active spots on the surface of the analyte particle facing the microscope, similar to the TERS configuration (Uzayisenga et al, 2012;Yang et al, 2009) and therefore the photons from the enhancement can be directly transferred to a detector without passing through the analyte particle.…”

Silver Nanoparticles-Loaded Exfoliated Graphite and Its Anti-Bacterial Performance

“…An effective way to prevent AgNPs from aggregation is to deposit AgNPs on some supports to fabricate AgNPs-loaded materials. Silica nanowires [7][8][9][10], zeolite clay [6], titanium dioxide nanoparticles [11], and montmorillonite have been investigated for antibacterial support materials. However, unfavorable biocompatibility, large size, and low dispersity of these composites limit their practical applications.…”