Surface Enhanced Raman Optical Effect as a Function of Ag-Colloids, NaCl and Myoglobin Concentration (original) (raw)
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Journal of Physics: Condensed Matter, 2007
Using surface enhanced ROA (SEROA), novel results are achieved by combining Raman optical activity (ROA) and resonance surface enhanced Raman scattering (SERRS), applied on myoglobin. The novelty of this work is in reporting for the first time on chiral results of a study performed on a protein at single molecule level. This work, using silver nanoparticles and a laser excitation of 532 nm, only became feasible when the concentrations of nanoparticles, aggregation agent NaCl and the studied molecule were optimized in a series of systematic optimization steps. The spectral analysis has shown that the SERS effect behaves accordingly, depending on the concentration ratio of each component, i.e., myoglobin, Ag colloids and NaCl. Consequently, it is shown here that the SERS intensity has its maximum at a certain concentration of these components, whereas below or above this value the intensity decreases. The optimization results can be considered as a completion of the hitherto known phenomenon 'dilution effect', which only takes account of higher concentrations. Furthermore, the optimization of the parameters seems to be necessary for a successful SEROA measurement, which enables chiral study of a protein at the single molecule level, in which the concentration and acquisition time are no longer an impediment.
Spectroscopy of single hemoglobin molecules by surface enhanced Raman scattering
Physical review letters, 1999
We demonstrate the detection of molecular vibrations in single hemoglobin (Hb) protein molecules attached to isolated and immobilized silver nanoparticles by surface enhanced Raman scattering (SERS). A comparison between calculation and experiment indicates that electromagnetic field effects dominate the surface enhancement, and that single molecule Hb SERS is possible only for molecules situated between Ag particles. The vibrational spectra exhibit temporal fluctuations of unknown origin which appear to be characteristic of the single molecule detection limit.
Surface-Enhanced Resonance Raman Spectroscopy Signals from Single Myoglobin Molecules
Applied Spectroscopy, 2002
The extremely large cross-section available from metallic surface enhancement has been exploited to investigate the Raman spectrum of heme myoglobin adsorbed on silver colloidal nanoparticles at very low concentrations. The study has been performed on particles both in solution and immobilized onto a polymer-coated glass surface. In both the cases, we have observed striking temporal uctuations in the surface-enhanced resonance Raman spectroscopy (SERRS) spectra collected at short tim es. A statistical analysis of the temporal intensity uctuations and of the associated correlations of the Raman signals has allowed us to verify that the single molecule limit is approached. The possible connections of these uctuations with the entanglement of the biomolecule within the local minima of its rough energy landscape is discussed.
2016
Introduction Material and Methods Results and Discussion Conclusion References by 91 107 111 needed. i'2Fortunately, it was found that Raman scattering can be highly enhanced at nano-roughed metal surface, which is called surface-enhanced Raman scattering (SERS). 3-6 Due to its great enhancement of Raman signal, SERS has been used to detect a variety of biomolecules including lipids, carbohydrates, DNA, peptides and proteins with a low detection of 1imit. 3'ii A number of SERS spectra of proteins have been published.iO'22 However, quantitative study of proteins by use of SERS is lack of reporting, except for one work in our group.i5 Moreover, experimental parameters for sample preparation are poorly reported in previous studies. And also the adsorption mechanism ofprotein on Ag surface has not been well investigated by use ofsERs. iO'22 Chapter 1 describes a novel method developed for protein detection used through the studies of this thesis. A heat-induced SERS-sensing method was used to selectively enhance the peak at 1049 cm'i originating from N03-for detection of proteins. A bell shape variation in the concentration dependent study was found, which can be used for semi-quarttitative detection of proteins. The detection limit for lysozyme and insulin is 1Ony9M and 1O-8M, respectively. Chapter 2 describes effects of experimental parameters on SERS intensities ofN03' and proteins by use ofthe SERS method established in Chapter 1. The results have shown that strong SERS signal can be In the present study, we have developed a novel heat-induced SERS-sensing method that can selectively enhance the peak at 1049 cm'i originating from N03' for detection of proteins without any additional resonant effect. A bell shape variation in the concentration dependent study was found, which can be used as a semi-quantitative method for protein detection. The detection limit for lysozyme and insulin is 10-9M and 10-8M, respectively. This method is simple, rapid, reproducible and label-free. The laser power is low (6 mW) and the exposure time is short (20 s), which meets the need for routine analyses. The intensity and the sharpness of the N03-peak suggest its potential in more extended applications. The bell shape indicates the potential of this method in exploring adsorption phenomenon of a protein on a colloidal interface.
Journal of the Chilean Chemical Society
The development of new biomaterials has gained increasing attention in the last decade. One of the most important aspects in the development of these new materials is to understand the chemical cues presents in the native niche. Among all the techniques currently available for measuring those interactions, Raman spectroscopy offers a unique and non-invasive tool for exploring the behavior of the components within a given biomaterial and their surrounding microenvironment. This technique exploits the unique molecular vibrational fingerprints for pinpointing those interactions. The vibrational response can be improved to the single molecule level, in the presence of metal nanoparticles (NPs) with plasmonic properties (silver, gold and copper) in the so-called Surface-Enhanced Raman Scattering (SERS), which can be used for in-situ measurements. Another technique recently developed is the Shell-Isolated Nanoparticle-Enhanced Raman Spectroscopy (SHINERS), which overcomes signal contamination from chemical interactions between biomolecules and the metal surface; it does this by coating the metal surface with an inert layer of alumina or silica. In the present contribution, the role and the applications of Raman, SERS and related spectroscopic techniques in the study of biomolecules in biomaterials are reviewed and discussed.
Surface-enhanced Raman scattering: a new optical probe in molecular biophysics and biomedicine
Theoretical Chemistry Accounts, 2010
Sensitive and detailed molecular structural information plays an increasing role in molecular biophysics and molecular medicine. Therefore, vibrational spectroscopic techniques, such as Raman scattering, which provide high structural information content are of growing interest in biophysical and biomedical research. Raman spectroscopy can be revolutionized when the inelastic scattering process takes place in the very close vicinity of metal nanostructures. Under these conditions, strongly increased Raman signals can be obtained due to resonances between optical fields and the collective oscillations of the free electrons in the metal. This effect of surface-enhanced Raman scattering (SERS) allows us to push vibrational spectroscopy to new limits in detection sensitivity, lateral resolution, and molecular structural selectivity. This opens up exciting perspectives also in molecular biospectroscopy. This article highlights three directions where SERS can offer interesting new capabilities. This includes SERS as a technique for detecting and tracking a single molecule, a SERS-based nanosensor for probing the chemical composition and the pH value in a live cell, and the effect of socalled surface-enhanced Raman optical activity, which provides information on the chiral organization of molecules on surfaces.
Journal of Raman Spectroscopy, 1990
Surface-enhanced Raman (SER) spectra of water-soluble proteins (lysozyme and bovine serum albumin), dipeptides and amino acids were analysed. Chemisorption is a necessary condition for the appearance of SER spectra on silver electrodes and hydrosols for these compounds. The Raman cross-section enhancement per molecule may reach a factor of 10s-106, depending closely on the frequency of the vibration band considered. The mechanism of enhancement has a short-range character and is attributed to the rc-electron complexes of the aromatic amino acids sidechains and u-complexes of the molecular group containing unsbared electron pairs with the metal. The effect of induced optical activity in the visible region for aromatic amino acids adsorbed by silver hydrosols has been elucidated.
Surface enhanced Raman scattering (SERS)—a quantitative analytical tool?
Journal of Raman Spectroscopy, 2006
Raman spectroscopy is a widely used analytical tool capable of providing valuable information about the chemical structure and composition of molecules. In order to detect substances also at a very low concentration levels, Surface Enhanced Raman Scattering (SERS) was introduced. The different amplification mechanisms result in extreme sensitivity, however, a quantitative use of SERS appears to be problematic. Especially, when deploying silver sols as SERS substrates, the reproducibility of the signal intensities for a given substance concentration is questionable. Experimental results of an investigation of this problem for low concentrations of adenine are presented. Comparison with results obtained for different SERS substrates by other authors reveals clearly different dependencies. Only in a very limited concentration range reproducible and therefore quantitatively utilizable data could be obtained.
Near-Infrared Surface-Enhanced Raman Scattering (NIR SERS) on Colloidal Silver and Gold
Applied Spectroscopy, 1994
Near-infrared surface-enhanced Raman scattering (NIR SERS) was detected with high sensitivity for two model compounds, crystal violet and the DNA base adenine, adsorbed on silver and gold colloidal particles in aqueous solutions. The NIR SERS spectra were measured with a fiber-optic probe with the use of a Ti:sapphire laser at 850 nm as the excitation source and a charge-coupled device (CCD) as the detection system. In a step to achieve the optimal electromagnetic SERS-enhancement conditions, silver and gold sols were modified to shift their extinction spectra more to the NIR region. Surface enhancement factors for both crystal violet and adenine were estimated to be on the order of 106 and 108 for gold and silver, respectively. A larger enhancement factor was observed for adenine with NIR excitation than with visible excitation. The benefits of NIR SERS and its potential applications are discussed.