Highly Sensitive, Uniform, and Reproducible Surface-Enhanced Raman Spectroscopy from Hollow Au-Ag Alloy Nanourchins (original) (raw)
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Nanoscale advances, 2022
The impact of variation in the interparticle gaps in dimers and trimers of gold nanoparticles (AuNPs), modified with Raman reporter (2-MOTP), on surface-enhanced Raman scattering (SERS) intensity, relative to the SERS intensity of a single AuNP, is investigated in this paper. The dimers, trimers, and single particles are investigated on the surfaces of four substrates: gold (Au), aluminium (Al), silver (Ag) film, and silicon (Si) wafer. The interparticle distance between AuNPs was tuned by selecting mercaptocarboxylic acids of various carbon chain lengths when each acid forms a mixed SAM with 2-MOTP. The SERS signal quantification was accomplished by combining maps of SERS intensity from a Raman microscope, optical microscope images (Â100), and maps/images from AFM or SEM. In total, we analysed 1224 SERS nanoantennas (533 dimers, 648 monomers, and 43 trimers). The average interparticle gaps were measured using TEM. We observed inverse exponential trends for the Raman intensity ratio and enhancement factor ratio versus gap distance on all substrates. Gold substrate, followed by silicon, showed the highest Raman intensity ratio (9) and dimer vs. monomer enhancement factor ratio (up to 4.5), in addition to the steepest inverse exponential curve. The results may help find a balance between SERS signal reproducibility and signal intensity that would be beneficial for future agglomerated NPs in SERS measurements. The developed method of 3 to 1 map combination by an increase in image transparency can be used to study structure-activity relationships on various substrates in situ, and it can be applied beyond SERS microscopy.
Physical Chemistry Chemical Physics, 2017
We used a combination of Raman microscopy, AFM and TEM to quantify the influence of dimerization on the surface enhanced Raman spectroscopy (SERS) signal for gold and silver nanoparticles (NPs) modified with Raman reporters and situated on gold, silver, and aluminum films and a silicon wafer. The overall increases in the mean SERS enhancement factor (EF) upon dimerization (up by 43% on average) and trimerisation (up by 96% on average) of AuNPs and AgNPs on the studied metal films are within a factor of two, which is moderate when compared to most theoretical models. However, the maximum ratio of EFs for some dimers to the mean EF of monomers can be as high as 5.5 for AgNPs on a gold substrate. In contrast, for dimerization and trimerization of gold and silver NPs on silicon, the mean EF increases by 1-2 orders of magnitude relative to the mean EF of single NPs. Therefore, hot spots in the interparticle gap between gold nanoparticles rather than hot spots between Au nanoparticles and the substrate dominate SERS enhancement for dimers and trimers on a silicon substrate. However, Raman labeled noble metal nanoparticles on plasmonic metal films generate on average SERS enhancement of the same order of magnitude for both types of hot spot zones (e.g. NP/NP and NP/metal film).
Nano Today, 2010
This communication refers to the design of a novel, highly efficient and uniform substrate for SERS. The method takes advantage of the block copolymer micelle nanolithography concept for making well-ordered and uniformly spaced gold nanodot assemblies, which are subsequently used as seed substrates for chemical growth, thereby yielding Ag nanoparticle arrays containing a high density of hot spots, which render these concentrated island films ideal substrates for reproducible surface enhanced Raman scattering (SERS) detection.
Nanotechnology, 2010
In this paper we highlight the accurate spectral detection of bovine serum albumin and ribonuclease-A using a Surface-Enhanced Raman Scattering (SERS) substrate based on gold nanocylinders obtained by Electron-Beam Lithography (EBL). The nanocylinders have diameter from 100 to 180 nm with a gap of 200 nm. We demonstrate that optimizing the size and the shape of the lithographied gold nanocylinders, we can obtain SERS spectra of proteins at low concentration. This SERS study enabled us to estimate high enhancement factors (10 5 for BSA and 10 7 for RNase-A) of important bands in the protein Raman spectrum measured for 1mM concentration. We demonstrate that to reach the highest enhancement it is necessary to optimize the SERS signal and that the main parameter of optimization is the LSPR position. The LSPR have to be suitably located between the laser excitation wavelength which is 632.8 nm and the position of the considered Raman band. Our study underlines the efficiency of gold nanocylinders arrays in spectral detection of proteins.
Rapid, solution-based characterization of optimized SERS nanoparticle substrates
Journal of The American Chemical Society, 2009
We demonstrate the rapid optical characterization of large numbers of individual metal nanoparticles freely diffusing in colloidal solution by confocal laser spectroscopy to guide nanoparticle engineering and optimization. We use ratios of the Rayleigh and Raman scattering response and rotational diffusion timescales of individual nanoparticles to show that hollow gold nanospheres and solid silver nanoparticle dimers linked with a bifunctional ligand, both specifically designed nanostructures, exhibit significantly higher monodispersity than randomly aggregated gold and silver nanoparticles.
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High-throughput, simple nanofabrication methods are essential keys for involving plasmonic materials with large electric fields for practical applications. We demonstrate in this paper a facile route for fabricating multifunctional metallic nanomaterials for sensing, which is particularly relevant to SERS spectroscopy. A simple deposition of a polymer dispersion doped with metallic precursor onto a conducting substrate allows a spontaneous formation of SERS-active substrates via vapor induced phase separation. The process enables the fabrication of several kinds of SERS chips with an original combination of fast throughput, low cost, reproducibility and high sensitivity. Our SERS results show significant enhancement factors exceeding 10 13 , which match the largest value (10 14 ) of metallic nanoparticle aggregates found until now. We quantify these enhancements by depositing bipyridine ethylene (BPE) on the substrate and spatially mapping their Raman intensities using confocal micro-Raman spectroscopy. Both the sensitivity threshold and reproducibility of all substrates were estimated by SERS measurements at variable concentrations of BPE. Our approach is new in fabricating high-throughput and reproducible SERS substrates over a large surface (on the whole substrate) by a one-step technique. As a result, we demonstrate a novel class of SERS substrates for which no patterning is necessary as in lithography, which provide a quick, simple and cheap way to fabricate highly sensitive SERS substrates.