Surface-enhanced Raman Scattering Detection Research Articles

Partition layer-modified substrates for reversible surface-enhanced Raman scattering detection of polycyclic aromatic hydrocarbons

Herein, we present progress towards an analytical sensor for polycyclic aromatic hydrocarbons (PAHs) using surface-enhanced Raman scattering (SERS) on partition layer-modified nanostructured substrates. Specifically, a 1-decanethiol monolayer has been assembled on a silver film over nanospheres substrate to concentrate PAHs within the zone of SERS detection. Both anthracene and pyrene were detected with limits of detection at 300 and 700 pM, respectively. The measured SERS spectra allowed for easy distinction of the two PAH compounds, due to varying peak locations, and insight into the partitioning mechanism. Additionally, exposure to a common environmental interferant, Suwannee River fulvic acid, did not impede the measurement of the PAHs, and the sensor is reusable after a short exposure to 1-octanol. Finally, the utility of this sensing platform for PAH detection was compared to that achievable for other classes of organic pollutants such as polychlorinated biphenyls and polybrominated diphenyl ethers.

Surface-enhanced Raman scattering detection and discrimination of polychlorinated biphenyls

Herein we present progress towards an analytical sensor for polychlorinated biphenyl (PCB) compounds using surface-enhanced Raman scattering (SERS) from partition layer-modified nanostructured substrates. Specifically, both alkanethiol and perfluoroalkanethiol self-assembled monolayers (SAMs) have been formed on a silver film over nanospheres (AgFON) substrate to concentrate PCBs within the zone of electromagnetic enhancement that facilitates SERS detection and molecular identification. Among the five partition layers used in this work, decanethiol (DT) facilitated the most efficient PCB detection; thus, other important PCB sensor characteristics were explored using the DT-modified SERS substrate. Limit of detection studies indicate that it will be possible to detect 50 pM PCB without further substrate or instrumental optimization. A time response study demonstrated that the maximum PCB SERS signal is achieved within 1 min of substrate exposure, a promising result for future in-field PCB detection. To test the sensor's ability to distinguish one PCB compound from another, the DT-modified AgFON substrates were exposed to both PCB-47 (2,2′,4,4′-tetrachlorobiphenyl) and PCB-77 (2,2′,3,3′-tetrachlorobiphenyl). The measured SERS spectra allowed easy distinction between the two similar compounds based on the C–Cl and aromatic peak locations. Additionally, exposure of the PCB sensor substrate to a common environmental interferant, Suwannee River fulvic acid, did slightly increase the spectral fluorescence background but did not impede PCB detection or identification. An ideal environmental sensor would be reusable, and, in fact, this work demonstrates that the partitioned PCB can be removed from the DT-modified AgFON substrate simply by incubating in octanol for 5 min so that the sensor can be reused. Finally, systematic examination of the measured SERS spectra with varied PCB exposure concentration and alkanethiol partition layer chain length gave insight into the molecular interactions between the SAM and the PCB analyte, demonstrating that some monolayer ordering is necessary to promote efficient PCB partitioning but that monolayers with highly crystalline character reduce partitioning efficiency.

A portable surface-enhanced Raman scattering sensor integrated with a lab-on-a-chip for field analysis

An integrated real-time sensing system that uses a portable Raman spectrometer and a micropillar array chip has been developed for field analysis. The problem of poor detection sensitivity, caused by miniaturization in the portable Raman spectrometer, was overcome by using the surface-enhanced Raman scattering (SERS) technique. The problem of poor reproducibility in the SERS detection, caused by different particle sizes and inhomogeneous degrees of aggregation, was also overcome by using continuous flow and homogeneous mixing between the analytes and nanocolloidal silver in a micropillar array microfluidic chip. Two hazardous materials, dipicolinic acid and malachite green, were quantitatively analysed using our integrated portable Raman sensor system. The observed limit of detection was estimated to be 200 ppb and 500 ppb, respectively. Our proposed analytical method, using a micropillar array PDMS chip and a portable SERS system, offers a rapid and reproducible trace detection capability for hazardous materials in the field.

Antibody-based SERS diagnostics of fhit protein without label

Surface-enhanced Raman scattering (SERS) is a particularly promising technique that has the potential to perform highly selective and sensitive in situ measurements of antibody-antigen reactions. This work describes the use of silver (Ag) colloids for immunoassay-based SERS detection of the fragile histidine triad (Fhit) protein. Alterations in Fhit protein expression have been associated with several human cancers, and, thus, the detection of Fhit protein is important because it can potentially be used as a cancer diagnostic biomarker, for both cancer detection and therapy.

Surface-Enhanced Raman Scattering Detection of Amphetamine and Methamphetamine by Modification with 2-Mercaptonicotinic Acid

We have demonstrated the use of surface-enhanced Raman scattering (SERS) spectroscopy for the detection of the phenylalkylamines amphetamine and methamphetamine. This work can be viewed as the first phase of development toward a one-step drug detection method with a selective reactive coating on a SERS substrate. This work involves a fairly complicated coupling reaction prior to surface derivatization. Future efforts will be directed at creating a reactive coating directly on the surface. The amines were derivatized by a coupling reaction with 2-mercaptonicotinic acid (2-MNA) with the use of dicyclohexylcarbodiimide (DCC) as the coupling reagent to form the amide compounds AMNA [ N-(1-methyl-2-phenylethyl)-2-mercaptopyridine-3-carboxamide] and MMNA [ N-methyl- N-(1-methyl-2-phenylethyl)-2-mercaptopyridine-3-carboxamide]. The amides were qualitatively identified from SERS spectra. Quantification of the amides was accomplished by adding the internal standard pentachlorothiophenol (PCTP) and measuring the intensity of Raman bands of the analyte relative to a Raman band of the internal standard. Calibration curves were plotted of the relative peak intensity ratios as a function of analyte concentration. Detection limits of 19 ppm and 17 ppm were found for amphetamine/2-MNA (AMNA) amide and methamphetamine/2-MNA (MMNA) amide, respectively.

NIR SERS detection of immune reaction on gold colloid particles without bound/free antigen separation

This paper reports the near-infrared (NIR) surface-enhanced Raman scattering (SERS) detection of immune reaction on gold colloid particles without bound/free (B/F) antigen separation. A SERS spectrum was measured for anti-mouse IgG at 2.2×10-8 M adsorbed on gold colloid particles. The spectrum showed a number of Raman bands assignable to amide groups and aromatic amino acid residues of anti-mouse IgG. A SERS spectrum of the same system at 1.9×10-10 M did not yield any Raman band. However, Raman bands again appeared after the reaction of anti-mouse IgG at 10-10 M with the antigen on the gold colloid particles. The band intensity of the spectrum obtained was weak, but the spectral pattern was very similar to that of anti-mouse IgG at 10-8 M adsorbed on the gold colloid particles. Probably, the formation of the immune complex on the gold colloid particles changed the configuration of anti-mouse IgG, enhancing the SERS signals. In this way, one could detect the immune complex on the gold colloid particles by NIR SERS spectroscopy without any B/F antigen separation. © 1998 John Wiley & Sons Ltd.

Identification by Surface Enhanced Raman Speci'roscopy of Photodegradation Products in Organic Photochromes

In this paper we described a recently developed method, using surface enhanced Raman scattering (SERS) in silver colloids, to detect and identify organic photochromes and their main photodegradation products. The reported SERS data were obtained on the classical 6-nitro-8-methoxy-indolinospirobenzopyran. It was observed that SERS spectra of this photochrome arise mainly from open species (photomerocyanines), and display vibrational features typical of the indolinic moiety. From specific SERS detection of totally degradated solutions, obtained under UV irradiation, it was possible to identify 5-nitrovanillin as the main photodegradation product and to estimate the proportions of this species and that of the remaining photochrome in various solvents (acetonitrile and dioxane).

Industrial Applications of the Surface-Enhanced Raman Spectroscopy

Surface-enhanced Raman scattering (SERS) spectroscopy is now a well-established phenomenon, which has been thoroughly characterized in a variety of interfacial and colloidal environments. Although some quantitative aspects of the underlying enhancement mechanisms apparently remain unresolved, attention is now shifting towards application of SERS to explore phenomena of chemical, physical, biological and industrial significance. The goal of this review is to appreciate the industrial value of innovative SERS technique on the basis of our experience in development of new SERS-active substrates and in their biomedical and biotechnological applications. Examples of diverse SERS analytical applications as well as some very recent facilities, as SERS microprobe analysis, SERS fiber optics probes, FT-SERS spectroscopy, SERS detection for high-performance liquid chromatography, etc. , are also discussed.

Silver-coated capillary tube for surface-enhanced Raman scattering

A silver-coated capillary tube was chemically prepared at room temperature and its performance as a surface-enhanced Raman scattering (SERS) active substrate was tested using p-nitrophenol (PNP), Rhodamine 6G and p-chlorobenzoic acid (PCBA) as analytes. The optimum time for the silver deposition was determined by using PNP as the analyte. Two different methods of sample application were tested and adapted. The surface enhancement effect of the substrate was found to be comparable to that of a silver-coated plate. Other studies were carried out to test both the efficiency of the substrate resulting from pretreatment of the tube and also the reusability of the substrate. Advantages of using the capillary substrate in SERS detection are discussed.