Fluctuation in surface enhanced Raman scattering intensity due to plasmon related heating effect
TL;DR: In this article, the authors investigated the effect of surface enhanced Raman scattering (SERS) on the signal intensity and found that the reduction in the spectral intensity is irreversible but never completely lost and a major part of it can be attributed to the plasmon induced heating.
Abstract: Temporal changes in signal intensity of Surface Enhanced Raman Scattering (SERS) upon laser excitation is an
interesting phenomenon in plasmonics. In-depth understanding of the phenomena is highly important especially when
developing a SERS sensor based on the intensity variation of particular Raman peak/band. One of the main challenges in
such a technique is the intensity reduction at a given location upon consecutive measurements. Previously, signal loss in
SERS measurement was attributed to the electric-field induced roughness relaxations in the SERS active surface. In such
cases, as the surface is smoothened out, signals are completely lost. In our observation, the reduction in the spectral
intensity is irreversible but never completely lost and a major part of it can be attributed to the plasmon induced heating
effect. Here, we experimentally demonstrate this effect by studying the SERS signal from four different Raman active
molecules adsorbed onto substrates that contain uniform nano-roughened bi-metallic silver/gold coating. Possible
mechanism that leads to irreversible signal loss is explained. Moreover, solutions for minimising such plasmonic heating
when developing a biosensor are also discussed.
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TL;DR: Coherent anti-Stokes Raman (CARS) microscopy and stimulated Raman loss (SRL) microscopeopy are orders of magnitude more efficient than Raman spectroscopy, and are able to acquire high quality chemically-specific images in seconds.
Abstract: In this review we describe label-free optical spectroscopy techniques which are able to non-invasively measure the (bio)chemistry in biological systems. Raman spectroscopy uses visible or near-infrared light to measure a spectrum of vibrational bonds in seconds. Coherent anti-Stokes Raman (CARS) microscopy and stimulated Raman loss (SRL) microscopy are orders of magnitude more efficient than Raman spectroscopy, and are able to acquire high quality chemically-specific images in seconds. We discuss the benefits and limitations of all techniques, with particular emphasis on applications in biomedicine—both in vivo (using fiber endoscopes) and in vitro (in optical microscopes).
168 citations
TL;DR: In this article, gold nanoparticles were selectively placed on the corners of rectangular origami and subsequently enlarged via solution-based metal deposition, and the resulting assembly exhibited hot spots of enhanced electromagnetic field between the nanoparticles.
Abstract: DNA origami is a novel self-assembly technique allowing one to form various two-dimensional shapes and position matter with nanometer accuracy. We use DNA origami templates to engineer surface-enhanced Raman scattering substrates. Specifically, gold nanoparticles were selectively placed on the corners of rectangular origami and subsequently enlarged via solution-based metal deposition. The resulting assemblies exhibit “hot spots” of enhanced electromagnetic field between the nanoparticles. We observed a significant Raman signal enhancement from molecules covalently attached to the assemblies, as compared to control nanoparticle samples that lack interparticle hot spots. Furthermore, Raman molecules are used to map out the hot spots’ distribution, as they are burned when experiencing a threshold electric field. Our method opens up the prospects of using DNA origami to rationally engineer and assemble plasmonic structures for molecular spectroscopy.
113 citations
TL;DR: This work uses DNA origami templates to engineer surface-enhanced Raman scattering substrates and observes a significant Raman signal enhancement from molecules covalently attached to the assemblies, as compared to control nanoparticle samples that lack interparticle hot spots.
Abstract: DNA origami is a novel self-assembly technique allowing one to form various 2D shapes and position matter with nanometer accuracy. It has been used to coordinate placement of nanoscale objects, both organic and inorganic; to make molecular motors and walkers; and to create optically active nanostructures. Here we use DNA origami templates to engineer Surfaced Enhanced Raman Scattering (SERS) substrates. Specifically, gold nanoparticles were selectively attached to the corners of rectangular origami and subsequently enlarged via solution-based metal deposition. The resulting assemblies were designed to form "hot spots" of enhanced electromagnetic field between the nanoparticles. We observed a significant enhancement of the Raman signal from molecules covalently attached to the assemblies, as compared to control nanoparticle samples which lack inter-particle hot spots. Our method opens up the prospects of using DNA origami to rationally engineer and assemble plasmonic structures for molecular spectroscopy.
104 citations
TL;DR: A systematic observation of the time evolution of the characteristic peak at 1365 cm-1 showed that the addition of the oxidized graphene layer over the analyte results in ∼2 times slower decay of the Raman intensity, indicating that the graphene coating can be used to enhance the stability of the SERS-signal from the CuTMpyP4 molecules.
Abstract: A method for fabricating surface-enhanced Raman scattering (SERS)-active substrates by immersion deposition of silver on a macroporous silicon (macro-PS) template with pore diameters and depth ranging from 500-1000 nm is developed. The procedure for the formation of nanostructured silver films in the layers of macro-PS was optimized. Silver particles of dimensions in the nano- and submicron-scale were formed on the external surface of the macro-PS immersed in the water-ethanol solution of AgNO3, while the inner pore walls were covered by smaller, 10-30 nm diameter, silver nanoparticles. Upon introducing the hydrofluoric acid to the reaction mixture, the size of nanoparticles grown on the pore walls increased up to 100-150 nm. Such nanostructures were found to yield SERS-signal intensities from CuTMpyP4 analyte molecules of the same order to those obtained from silvered mesoporous silicon reported previously. The tested storage stability for the silvered macro-PS-based samples reached up to 8 months. However, degradation of the SERS intensity under illumination by the laser beam during spectral measurements was observed. To improve the stability of the SERS-signal a hybrid structure involving graphene oxide deposited on the top of analyte molecules adsorbed on the Ag/macro-PS was formed. A systematic observation of the time evolution of the characteristic peak at 1365 cm-1 showed that the addition of the oxidized graphene layer over the analyte results in ∼2 times slower decay of the Raman intensity, indicating that the graphene coating can be used to enhance the stability of the SERS-signal from the CuTMpyP4 molecules.
6 citations
Dissertation•
01 Jan 2014
TL;DR: Metallic Nanostructures based on Self-Assembling DNA Templates for Studying Optical Phenomena as discussed by the authors have been shown to be useful in the field of optical physics.
Abstract: Metallic Nanostructures Based on Self-Assembling DNA Templates for Studying Optical Phenomena