Surface enhanced Raman spectroscopy of self-assembled monolayers of 2-mercaptopyridine on a gold electrode (original) (raw)
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Journal of Molecular Structure, 2010
A feasibility study has been undertaken to assess the suitability of a commercially available SERS substrate for monitoring of self-assembling deposition process. Monolayer self-assembly of 4-mercaptobenzoic acid on SERS active substrate Klarite™ from absolute and acidified ethanol was studied and compared with deposition on SPR substrate from absolute ethanol. Changes in integral intensity of the phenyl bands at 1587 and 1076 cm À1 and ethanol band at 1451 cm À1 allow to follow structural changes in the monolayer. Stability of the monolayer assembled from acidified ethanol in contrast to the pure ethanol was demonstrated.
Physical chemistry chemical physics : PCCP, 2015
Confeito-like gold nanoparticles (AuNPs; average diameter = 80 nm) exhibiting a plasmon absorption band at 590 nm were adsorbed through immersion-adsorption on two self-assembled monolayers (SAMs) of 3-aminopropyltriethoxysilane (APTES-SAM) and polystyrene spheres coated with amine-terminated poly(amido amine) dendrimers (DEN/PS-SAM). The surface enhanced Raman scattering (SERS) effect on the SAM substrates was examined using the molecules of a probe dye, rhodamine 6G (R6G). The Raman scattering was strongly intensified on both substrates, but the enhancement factor (>10 000) of the AuNP/DEN/PS-SAM hierarchy substrate was 5-10 times higher than that of the AuNP/APTES-SAM substrate. This strong enhancement is attributed to the large surface area of the substrate and the presence of hot spots. Furthermore, analyzing the R6G concentration dependence of SERS suggested that the enhancement mechanism effectively excited the R6G molecules in the first layer on the hot spots and invoked ...
Chinese Journal of Analytical Chemistry, 2011
Surface-enhanced Raman scattering (SERS) was used for the detection of 2,6-pyridinedicarboxylic acid (DPA), a biomarker for bacterial spores. By immobilizing gold nanoparticles of diameter 60 nm on a polished Au electrode using PVP as an adhesive layer, the steady and highly sensitive SERS substrates were fabricated. By using strong acid and alkali to adjust the pH value of DPA molecules, the molecular adsorption configuration of DPA via the SERS characteristics under various pH values were studied and the changes of SERS intensity were compared when HCl, H 2 SO 4 and HNO 3 were separately added to the DPA solution to get a pH value of 1.3. The changes of the adsorption form were also analyzed when NaCl, MgSO 4 and NaNO 3 were separately added to the DPA solution. The results showed that the anion of acids could play a role as a bridge when DPA molecules were protonated by the addition of acids, which could greatly enhance the SERS signal; however, when the pH value is greater than the second dissociation constant of DPA, because of steric effect and the disappearance of the bridge, the SERS signal decreases gradually. Compared with NO 3 and SO 4 2-, Clhas a much stronger binding force with protonated N on DPA; consequently, the addition of HCl can get the maximum SERS signal enhancement.
Analytical Chemistry, 2005
We apply well-characterized silver nanowire grating (Ag-NWG) plasmonic surfaces as a Raman surface spectroscopy tool, which is based on surfaceenhanced Raman scattering (SERS), to study the surface conformation characteristics of amine terminated alkanethiol self-assembled monolayers (SAMs). The surface conformation has implications for amine group availability, which is important when SAMs are used as linking layers for the binding of secondary molecules. Two different alkanethiols with different alkane chain lengths, namely 2-aminoethanethiol (cysteamine, CEA) and 11-aminoundecanethiol (AUT), are investigated. It is shown that both alkanethiols bind to Ag surfaces forming corresponding Ag-thiolates, however surface conformations, which are related to the ordering of the SAM, are different for these two SAM systems. The degree of SAM ordering is assessed by quantifying the integrated intensity ratio of the trans to gauche ν(C−S) vibrational bands from single spectra measurements and from spatially averaged spectra. These vibrational modes occur at different vibrational frequencies depending on the conformation (trans versus gauche) of the neighboring carbon atom. We demonstrate that the CEA SAMs are less ordered than AUT SAMs; thus, the amine terminal group availability differs between both systems.
Surface-enhanced Raman scattering-active gold nanoparticles modified with a monolayer of silver film
The Analyst, 2012
Gold nanoparticles were produced by photochemical reaction of synchrotron radiation. The gold nanoparticles grew and aggregated into the higher-order nanostructure. The behavior is qualitatively explained by analytical estimation. The surface-enhanced Raman spectroscopy of 4,4 0-bipyridine (4bpy) was demonstrated. The substrate fabricated in a suitable condition provides in situ SERS for 1 nM 4bpy.
Surface enhanced Raman spectroscopy of organic molecules deposited on gold sputtered substrates
Nanotechnology, 2009
Black silicon (bSi) refers to an etched silicon surface comprising arrays of microcones that effectively suppress reflection from UV to near-infrared (NIR) while simultaneously enhancing the scattering and absorption of light. This makes bSi covered with a nmthin layer of plasmonic metal, i.e., gold, an attractive substrate material for sensing of bio-macromolecules and living cells using surfaceenhanced Raman spectroscopy (SERS). The performed Raman measurements accompanied with finite element numerical simulation and density functional theory analysis revealed that at the 785 nm excitation wavelength, the SERS enhancement factor of the bSi/Au substrate is as high as 10 8 due to a combination of electromagnetic and chemical mechanisms. This finding makes the SERS-active bSi/Au substrate suitable for detecting trace amounts of organic molecules. We demonstrate the outstanding performance of this substrate by highly sensitive and specific detection of a small organic molecule of 4-mercaptobenzoic acid and living C6 rat glioma cell nucleic acids/proteins/lipids. Specifically, the bSi/Au SERS-active substrate offers a unique opportunity to investigate the living cells' malignant transformation using characteristic protein disulfide Raman bands as a marker. Our findings evidence that bSi/Au provides a pathway to the highly sensitive and selective, scalable, and low-cost substrate for lab-on-a-chip SERS biosensors that can be integrated into silicon-based photonics devices.
Nanomaterials, 2021
Hyperbolic metamaterials (HMMs), supporting surface plasmon polaritons (SPPs), and highly confined bulk plasmon polaritons (BPPs) possess promising potential for application as surface-enhanced Raman scattering (SERS) substrates. In the present study, a composite SERS substrate based on a multilayer HMM and gold-nanoparticle (Au-NP) layer was fabricated. A strong electromagnetic field was generated at the nanogaps of the Au NPs under the coupling between localized surface plasmon resonance (LSPR) and a BPP. Additionally, a simulation of the composite structure was assessed using COMSOL; the results complied with those achieved through experiments: the SERS performance was enhanced, while the enhancing rate was downregulated, with the extension of the HMM periods. Furthermore, this structure exhibited high detection performance. During the experiments, rhodamine 6G (R6G) and malachite green (MG) acted as the probe molecules, and the limits of detection of the SERS substrate reached 1...
Gold bulletin, 2013
Surface-enhanced Raman spectroscopy (SERS) has enormous potential for a range of applications where high sensitivity needs to be combined with good discrimination between molecular targets. However, the SERS technique has trouble finding its industrial development, as was the case with the surface plasmon resonance technology. The main reason is the difficulty to produce stable, reproducible, and highly efficient substrates for quantitative measurements. In this paper, we report a method to obtain two-dimensional regular nanopatterns of gold nanoparticles (AuNPs). The resulting patterns were evaluated by SERS. Our bottom-up strategy was divided into two steps: (a) nanopatterning of the substrate by e-beam lithography and (b) electrostatic adsorption of AuNPs on functionalized substrates. This approach enabled us to highlight the optimal conditions to obtain monolayer, rows, or ring of AuNPs, with homogeneous distribution and high density (800 AuNPs/μm 2). The nanostructure distributions on the substrates were displayed by scanning electron microscopy and atomic force microscopy images. Optical properties of our nanostructures were characterized by visible extinction spectra and by the measured enhancements of Raman scattering. Finally, we tried to demonstrate experimentally that, to observe a significant enhancement of SERS, the gold diffusers must be extremely closer. If electron beam lithography is a very attractive technique to perform reproducible SERS substrates, the realization of pattern needs a very high resolution, with distances between nanostructures probably of less than 20 nm.
The Journal of Physical Chemistry Letters, 2010
Raman signals from molecules adsorbed on a noble metal surface are enhanced by many orders of magnitude due to the plasmon resonances of the substrate. Additionally, the enhanced spectra are modified compared to the spectra of neat molecules: many vibrational frequencies are shifted and relative intensities undergo significant changes upon attachment to the metal. With the goal of devising an effective scheme for separating the electromagnetic and chemical effects, we explore the origin of the Raman spectra modification of benzenethiol adsorbed on nanostructured gold surfaces. The spectral modifications are attributed to the frequency dependence of the electromagnetic enhancement and to the effect of chemical binding. The latter contribution can be reproduced computationally using moleculemetal cluster models. We present evidence that the effect of chemical binding is mostly due to changes in the electronic structure of the molecule rather than to the fixed orientation of molecules relative to the substrate.