Applications Of Surface-enhanced Raman Scattering Substrates Research Articles

Optimization of Ag coated hydrogen silsesquioxane square array hybrid structure design for surface-enhanced Raman scattering substrate.

A computer-automated design process for a surface-enhanced Raman scattering (SERS) substrate using a particle swarm optimization algorithm is proposed. Nanostructured Ag coated hydrogen silsesquioxane nanopillar arrays of various sizes for SERS substrate applications are fabricated by direct Ag film deposition on substrates patterned by electron beam lithography and are investigated systematically. Good agreement is demonstrated between experimental and simulation results. The absorption spectra, charge distributions, and electric field distributions are calculated using finite-difference time-domain simulations to explain the field enhancement mechanism and indicate that this enhancement originates from plasmon resonance. Our work provides a guide towards optimum SERS substrate design.

Low-cost Au nanoparticle-decorated cicada wing as sensitive and recyclable substrates for surface enhanced Raman scattering

A large-scale, low-cost and three-dimensional biomimetic surface enhanced Raman scattering (SERS) substrate with vast and regular ‘hot spots’ was prepared by the deposition of gold (Au) nanoparticles on the bioscaffold arrays of cicada wings by the electron beam evaporation. Characterizations of the formed three-dimensional Au/cicada wing nanostructure proved that it owns outstanding SERS properties of highly active sensitivity, good uniformity and repeatability. The SERS limit of detection (LOD) for Rhodamine 6G reaching as low as 10−7M, and a Raman enhancement factor being as large as 105 with a relative standard deviation of 10.1% were obtained. More importantly, this substrate has a good recyclability by the simple NaBH4 washing. For the application of Au/cicada wing, thiram was also detected rapidly and quantitatively with a LOD as low as 10−7M. Our findings are beneficial in the application of SERS substrate, allowing quantitative and recyclable detection of trace organic contaminants and making it very promising in the label-free detection of biological molecules.

Surface-enhanced Raman scattering effects of gold nanorods prepared by polycarbonate membranes

Using a polycarbonate membrane (PCM) as a template, and combining with the electrochemical deposition method, we prepare gold nanorods each with about 36 nm in diameter and 1 μrm in length. We measure transmission spectra, and find that the resonant absorption peak is at around 540 nm. Subsequently, the enhancement effects of the nanorods are investigated with 514 nm and 633 nm laser excitations. Comparing the spectra under resonant condition with those under non-resonant condition, we conclude that the field enhancement effect under the resonant excitation is more prominent than under the non-resonant excitation. The enhancement factor under the resonant excitation is increased to 7 times of the factor under the non-resonant excitation. Comparing with similar researches, we achieve the following two improvements: 1) with a resonant excitation, we significantly increase the enhancement factor of gold nanorods; 2) we eliminate the fluorescence of PCM molecules, thus make the template method more feasible for transparent surface-enhanced Raman scattering substrate applications.

Surface-Enhanced Raman Scattering

The increasing applications of surface-enhanced Raman scattering (SERS) has led to the development of various SERS-active platforms (SERS substrates) for SERS measurement. This work reviews the current optimization techniques available for improving the performance of some of these SERS substrates. The work particularly identifies self-assembled-monolayer(SAM-) based substrate modification for optimum SERS activity and wider applications. An overview of SERS, SAM, and studies involving SAM-modified substrates is highlighted. The focus of the paper then shifts to the use of SAMs to improve analytical applications of SERS substrates by addressing issues including long-term stability, selectivity, reproducibility, and functionalization, and so forth. The paper elaborates on the use of SAMs to achieve optimum SERS enhancement. Specific examples are based on novel multilayered SERS substrates developed in the author’s laboratory where SAMs have been demonstrated as excellent dielectric spacers for improving SERS enhancement more than 20-fold relative to conventional single layer SERS substrates. Such substrate optimization can significantly improve the sensitivity of the SERS method for analyte detection.

Adsorption Kinetics of Au and Ag Nanoparticles on Functionalized Glass Surfaces

Well-defined two- or three-dimensional arrangements of nanosize Au and Ag particles were fabricated for surface-enhanced Raman scattering substrate applications and their unique optical properties. Two-dimensional arrays of colloidal films of Au and Ag were prepared on glass slides modified with silane compounds having bifunctional moieties that have specific affinity for gold or silver. During the formation of colloidal films of Au and Ag on glass slides, UV–vis absorption spectroscopy was used to monitor the progress of the surface immobilization reaction of colloidal particles on solid substrates. Adsorption characteristics could be accurately modeled by the well-known Michaelis–Menten kinetics. It was found that the k3/k1 values were proportional to particle size. This indicates that the rate of formation of the first monolayer with relatively small particles is faster than that of the multilayers, whereas for larger colloids the multilayer formation rate is much faster. SERS spectra of p-aminothiophenol (PATP) on a silver colloidal film were obtained with 514.5-nm excitation. SERS intensities of PATP increased significantly with morphological change of the colloidal film. This morphological alteration, parallel to water evaporation from the colloidal film, was presumably induced by the difference in dielectric constants of air and water.