Hybrid nanostructured supports for surface enhanced Raman scattering (original) (raw)

Single molecule surface-enhanced Raman spectroscopy in nanogap structures

2009

A general overview of the field of single-molecule (SM) surface-enhanced Raman spectroscopy (SERS) as it stands today is provided. After years of debates on the basic aspects of SM-SERS, the technique is emerging as a well-established subfield of spectroscopy and SERS. SM-SERS is allowing the observation of subtle spectroscopic phenomena that were not hitherto accessible. Examples of the latter are natural isotopic substitutions in single molecules, observation of the true homogeneous broadening of Raman peaks, Raman excitation profiles of individual molecules, and SM electrochemistry. With background examples of the contributions produced by our group, properly interleaved with results by other practitioners in the field, we present some of the latest developments and promising new leads in this new field of spectroscopy. 65 Annu. Rev. Phys. Chem. 2012.63:65-87. Downloaded from www.annualreviews.org by Victoria University of Wellington on 04/10/12. For personal use only. Click here for quick links to Annual Reviews content online, including: • Other articles in this volume • Top cited articles • Top downloaded articles • Our comprehensive search Further ANNUAL REVIEWS

A Scheme for Detecting Every Single Target Molecule with Surface-Enhanced Raman Spectroscopy

Nano Letters, 2011

Surface-enhanced Raman spectroscopy (SERS) is now a well-established technique for the detection, under appropriate conditions, of single molecules (SM) adsorbed on metallic nanostructures. However, because of the large variations of the SERS enhancement factor on the surface, only molecules located at the positions of highest enhancement, so-called hot-spots, can be detected at the single-molecule level. As a result, in all SM-SERS studies so far only a small fraction, typically less than 1%, of molecules are actually observed. This complicates the analysis of such experiments and means that trace detection via SERS can in principle still be vastly improved. Here we propose a simple scheme, based on selective adsorption of the target analyte at the SERS hot-spots only, that allows in principle detection of every single target molecule in solution. We moreover provide a general experimental methodology, based on the comparison between average and maximum (single molecule) SERS enhancement factors, to verify the efficiency of our approach. The concepts and tools introduced in this work can readily be applied to other SERS systems aiming for detection of every single target molecule.

Single-Molecule Chemistry with Surface- and Tip-Enhanced Raman Spectroscopy

Chemical Reviews, 2016

Single-molecule (SM) surface-enhanced Raman spectroscopy (SERS) and tip-enhanced Raman spectroscopy (TERS) have emerged as analytical techniques for characterizing molecular systems in nanoscale environments. SERS and TERS use plasmonically enhanced Raman scattering to characterize the chemical information on single molecules. Additionally, TERS can image single molecules with subnanometer spatial resolution. In this review, we cover the development and history of SERS and TERS, including the concept of SERS hot spots and the plasmonic nanostructures necessary for SM detection, the past and current methodologies for verifying SMSERS, and investigations into understanding the signal heterogeneities observed with SMSERS. Moving on to TERS, we cover tip fabrication and the physical origins of the subnanometer spatial resolution. Then, we highlight recent advances of SMSERS and TERS in fields such as electrochemistry, catalysis, and SM electronics, which all benefit from the vibrational characterization of single molecules. SMSERS and TERS provide new insights on molecular behavior that would otherwise be obscured in an ensembleaveraged measurement. CONTENTS 1. Introduction 7584 1.1. Background 7584 1.2. Scope of Review 7585 2. Single-Molecule SERS 7585 2.1. Hot Spots and Plasmonic Nanostructures 7585 2.1.1.

Probing Single Molecules and Single Nanoparticles by Surface-Enhanced Raman Scattering

Science, 1997

Optical detection and spectroscopy of single molecules and single nanoparticles have been achieved at room temperature with the use of surface-enhanced Raman scattering. Individual silver colloidal nanoparticles were screened from a large heterogeneous population for special size-dependent properties and were then used to amplify the spectroscopic signatures of adsorbed molecules. For single rhodamine 6G molecules adsorbed on the selected nanoparticles, the intrinsic Raman enhancement factors were on the order of 10 14 to 10 15 , much larger than the ensemble-averaged values derived from conventional measurements. This enormous enhancement leads to vibrational Raman signals that are more intense and more stable than single-molecule fluorescence.

Single-Molecule Raman Spectroscopy – Fact or Fiction?

CHIMIA

Single-molecule detection represents the ultimate sensitivity limit in chemical analysis. Spectroscopic studies may even allow identifying the chemical structure of a single molecule, offering far-reaching opportunities in basic and applied research. Recent advances have allowed detection and dynamic studies of single molecules under both cryogenic and ambient conditions [l]. Most of these studies are based on laser-induced fluorescence, a method that provides ultra-high sensitivity but is limited in the amount of molecular information. Vibrational spectroscopy, for example Raman spectroscopy, would be a preferred method for single-molecule studies because of the very high chemical information content. Raman scattering, however, is a very weak effect, with cross sections between 10-30 cm 2 and 10-25 cm 2 per molecule, the larger values occuring only under favorable resonance Raman conditions. Such small Raman cross sections require a large number of molecules to achieve adequate conversion rates from excitation laser photons to Raman photons, thereby making single-molecule Raman spectroscopy 'science fiction'. This situation is dramatically improved if surface-enhanced Raman scattering (SERS) is used. The exciting phenomenon of a strongly increased Raman signal from molecules attached to metallic nanostructures was discovered in 1977 by Van Duyne, Jeanmaire, Albrecht and Creighton [2]. Very recently, and almost simultaneously, two groups, the one of Kathrin Kneipp and the other of Shuming Nie, unexpectedly observed enhancement factors much larger than the ensemble-aver

Single Molecule Detection Using Surface-Enhanced Raman Scattering (SERS)

Physical Review Letters, 1997

By exploiting the extremely large effective cross sections ( 10 -17 –10 -16 cm 2 /molecule) available from surface-enhanced Raman scattering (SERS), we achieved the first observation of single molecule Raman scattering. Measured spectra of a single crystal violet molecule in ...

Single-Molecule Surface-Enhanced Raman Spectroscopy

Annual Review of Physical Chemistry, 2012

A general overview of the field of single-molecule (SM) surface-enhanced Raman spectroscopy (SERS) as it stands today is provided. After years of debates on the basic aspects of SM-SERS, the technique is emerging as a well-established subfield of spectroscopy and SERS. SM-SERS is allowing the observation of subtle spectroscopic phenomena that were not hitherto accessible. Examples of the latter are natural isotopic substitutions in single molecules, observation of the true homogeneous broadening of Raman peaks, Raman excitation profiles of individual molecules, and SM electrochemistry. With background examples of the contributions produced by our group, properly interleaved with results by other practitioners in the field, we present some of the latest developments and promising new leads in this new field of spectroscopy.

From Average to Single Molecule Surface Enhanced Raman Scattering

2010

In the present work, the combination of chemical immobilization with electron beam lithography enables the production of sensitive and reproducible SERS-active areas composed of stochastic arrangements of gold nanoparticles. The number of nanoparticles was varied from 2 to 500. Thereby a systematic analysis of these SERS-active areas allows us to study SERS efficiency as a function of the number of nanoparticles. We found that the experimental parameters are critical, in particular the size of the SERS-active area must be comparable to the effective area of excitation to obtained reproducible SERS measurements. The sensitivity has also been studied by deducing the number of NPs that generate the enhancement. With this approach we demonstrates that the maximum enhancement, the best sensitivity, is obtained with the smallest number of nanoparticles that is resonant at a given excitation wavelength.

Surface Enhanced Raman Spectroscopy for Single Molecule Protein Detection

Scientific Reports, 2019

A two-step process of protein detection at a single molecule level using SeRS was developed as a proofof-concept platform for medical diagnostics. First, a protein molecule was bound to a linker in the bulk solution and then this adduct was chemically reacted with the SeRS substrate. traut's Reagent (tR) was used to thiolate Bovine serum albumin (BSA) in solution followed by chemical cross linking to a gold surface through a sulfhydryl group. A Glycine-TR adduct was used as a control sample to identify the protein contribution to the SER spectra. Gold SERS substrates were manufactured by electrochemical deposition. Solutions at an ultralow concentration were used for attaching the tR adducts to the SeRS substrate. Samples showed the typical behavior of a single molecule SeRS including spectral fluctuations, blinking and Raman signal being generated from only selected points on the substrate. The fluctuating SER spectra were examined using Principle Component Analysis. This unsupervised statistics allowed for the selecting of spectral contribution from protein moiety indicating that the method was capable of detecting a single protein molecule. Thus we have demonstrated, that the developed two-step methodology has the potential as a new platform for medical diagnostics.

Observing single-molecule chemical reactions on metal nanoparticles

2001

We report on the study of the photodecomposition of single Rhodamine 6G (R6G) dye molecules adsorbed on silver nanoparticles. The nanoparticles were immobilized and spatially isolated on polylysine-derivatized glass coverslips, and confocal laser microspectroscopy was used to obtain surface-enhanced Raman scatters (SERS) spectra from individual R6G molecules. The photodecomposition of these molecules was observed with 150-ms temporal resolution. The photoproduct was identified as graphitic carbon based on the appearance of bread SERS vibrational bands at 1592 cm-1 and 1340 cm-1 observed in both bulk and averaged single-molecule photoproduct spectra. In contrast, when observed at the single-molecule level, the photoproduct yielded sharp SERS spectra. The inhomogeneous broadening of the bulk SERS spectra is due to a variety of photoproducts in different surface orientations and is a characteristic of ensemble-averaged measurement of disordered systems. These single-molecule studies indicate a photodecomposition pathway by which the R6G molecule desorbs from the metal surface, an excited-state photoreaction occurs, and the R6G photoproduct(s) readsorbs to the surface. A SERS spectrum is obtained when either the intact R6G or the R6G photoproduct(s) are adsorbed on a SERS-active site. This work further illustrates the power of single-molecule spectroscopy (SMS) to reveal unique behaviors of single molecules that are not discernable with bulk measurements.