Extraordinary Enhancement of Raman Scattering from Pyridine on Single Crystal Au and Pt Electrodes by Shell-Isolated Au Nanoparticles

Abstract

We used shell-isolated nanoparticle-enhanced Raman spectroscopy (SHINERS) to systematically study the adsorption of pyridine on low-index Au(hkl) and Pt(hkl) single crystal electrodes. Our gold-core silica-shell nanoparticles (Au@SiO(2) NPs) boost the intensity of Raman scattering from molecules adsorbed on atomically flat surfaces. The average enhancement factor reaches 10(6) for Au(110) and 10(5) for Pt(110), which is comparable to or even greater than that obtained for bare gold NPs (a widely adopted SERS substrate). 3D-FDTD simulations reveal that this large enhancement is due to the transfer of the "hotspots" from NP-NP gaps to NP-surface gaps. We also found that the SHINERS intensity strongly depends on the surface crystallographic orientation, with differences up to a factor of 30. Periodic DFT calculations and theoretical analysis of dielectric functions indicate that this facet-dependence is predominantly governed by the dielectric property of the surface. The results presented in this work may open up new approaches for the characterization of adsorbates and reaction pathways on a wide range of smooth surfaces.

Shell‐Isolated Nanoparticle‐Enhanced Raman Spectroscopy (SHINERS)

“…Comparative experiments of Py adsorbed on the three low-index Au(hkl) single-crystal surfaces show that SHINERS intensity is strongly dependent on the surface crystallographic orientation [52]. Figure 8.11c illustrates the trend at a substrate potential of 0.0 V. The Raman signal from Au(110) is about 8 times stronger than that obtained from Au (100), and about 30 times stronger than that obtained from Au(111).…”

“…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].…”

Advances in surface-enhanced vibrational spectroscopy at electrochemical interfaces

“…Procedures to synthesise SHINs are now well-documented [85], typical particles comprising a 55-120 nm spherical gold or silver core [82,86,87] [92], graphene [93,94] and other carbon materials [95,96]. Example core-shell particles are depicted in Figure 5 The substrate generality of SHINERS has greatly benefitted electrochemical Raman spectroscopy and an impressive range of native electrode substrates have been investigated including Ag [97,98], Au [99][100][101][102][103][104], Pt [99,102], Pd [102], Rh [105], Ni alloys [106,107], Cu [108] and glassy carbon (GC) [102]. Moreover, SHINERS enables the detailed investigation of single crystal electrodes, which are of tremendous interest as model systems from a surface science perspective, allowing the effect of surface atomic structure on behaviour and reactivity to be systematically investigated [109].…”

Insights into the heterogeneous distribution of SERS effect in plasmonic hot spots between Au@SiO2monolayer film and gold single crystal plates

“…As the GSCPs can be served as a free electron reservoir, it will further induce the charge gathering in the holes underneath the NPs due to the electrostatic effect, causing the redistribution of hot spots on the surfaces to reach a steady and proper state matching with the selected wavelength. 30,45 Besides that as the silica shell prevents the spread and transfer of free electrons in the "particle-surface" gap, it is easier to induce the enrichment of charges just in this gap area aer the encapsulation of silica shells. 28 So one can assume that the laser of 785 nm which matches better with "particle-surface" gap mode is more benecial to inducing the oscillation of free electrons and thus gathering of charges in the gaps to form electron holes underneath the NPs.…”

“…Tian and his coworkers performed a series of investigations on the coupling effect between the SHINs and single crystal metallic surface, conrming the transfer of hot spots from the "particle-particle" to "particle-surface" gap mode. [28][29][30] Therefore, the observed stronger SERS signal on the GSCPs surface is mainly contributed by the latter mode.…”