Detection of explosive vapour using surface-enhanced Raman spectroscopy

A commercially available nano-structured gold substrate was used for activating surface-enhanced Raman scattering (SERS). Raman spectra of the vapour of explosive material, triacetonetriperoxide (TATP), at trace concentrations produced from adsorbed molecules on such surfaces have been studied. Prominent Raman lines of the explosive molecular species were recorded at a sample temperature of ∼35°C, which is near to human body temperature. For this study, the concentration of the adsorbed TATP molecules on the nano-structured surface was varied by heating the sample to different temperatures and exposing the substrate to the sample vapour for different lengths of time. The intensities of the Raman lines have been found to increase with the increase in temperature and also with the increase in the duration of exposure for a fixed temperature. However, as expected, the Raman intensities have been found to saturate at higher temperatures and longer exposures. These saturation effects of the strengths of the Raman lines in the SERS of TATP vapour have been investigated in this paper. The results indicate that the optimisation for vapour deposition on the surface could be a crucial factor for any quantitative estimate of the concentration of the molecular species adsorbed on the nano-structured substrates.     

Nasopharyngeal carcinoma detection by tissue smears using surface-enhanced Raman spectroscopy

Nasopharyngeal carcinoma is one of the most common malignant neoplasms in head and neck. In this work, surface-enhanced Raman spectroscopy technique was used to study the molecular differences between cancerous and noncancerous smear samples which were obtained after clinical biopsy by smearing the tissue on the slides. Principal component analysis combined with linear discriminant analysis provided a sensitivity of 79.4% and a specificity of 81.8% for differentiation between cancerous and noncancerous nasopharyngeal tissue smears. This work provides a good basis for the methodology of nasopharyngeal tissue smear based on surface-enhanced Raman spectroscopy technique and is worth further studying.     

Microbiological identification by surface-enhanced Raman spectroscopy

New methods for pathogens identification are of growing interest in clinical and food sectors. The challenge remains to develop rapid methods that are more simple, reliable, and specific. Surface-enhanced Raman spectroscopy (SERS) appears to be a promising tool to compete with current untargeted identification methods. This article presents the intensive research devoted to the use of SERS for bacterial identification, from the first to the very recent published results. Compared to normal Raman spectroscopy, the introduction of nanoparticles for SERS acquisition introduces a new degree of complexity. Bacterial Raman fingerprints, which are already subject to high spectral variability for a given strain, become then very dependent on numerous experimental parameters. To overcome these limitations, several approaches have been proposed to prepare the sample, from the microbiological culture conditions to the analysis of the spectrum including the coupling of nanoparticles on the bacterial membrane. Main strategies proposed over the last 20 years are examined here and discussed in the perspective of a protocol transfer towards industry.     

Single-site surface-enhanced Raman scattering beyond spectroscopy

Recent progress in the observation of surface-enhanced Raman scattering (SERS) is reviewed to examine the possibility of finding a novel route for the effective photoexcitation of materials. The importance of well-controlled SERS experiments on a single molecule at a single site is discussed based on the difference in the information obtained from ensemble SERS measurements using multiple active sites with an uncontrolled number of molecules. A single-molecule SERS observation performed at a mechanically controllable breaking junction with a simultaneous conductivity measurement provides clear evidence of the drastic changes both in the intensity and in the Raman mode selectivity of the electromagnetic field generated by localized surface plasmon resonance. Careful control of the field at a few-nanometer-wide gap of a metal nanodimer results in the modification of the selection rule of electronic excitation of an isolated single-walled carbon nanotube. The examples shown in this review suggest that a single-site SERS observation could be used as a novel tool to find, develop, and implement applications of plasmon-induced photoexcitation of materials.     

Raman and surface-enhanced Raman spectroscopy evidence for oxidation-induced decomposition of graphite

It has been proposed that reduction of exfoliated graphite oxide could be a potential method for producing large quantities of graphene. Raman and surface-enhanced Raman spectroscopy are used to show that oxidation of graphite and exfoliated graphite significantly increases the defect structure of both materials. This would likely lead to a heavily defected graphene structure when oxygen is removed. To insure the observed decomposition is not due to the laser light, the effect of laser intensity on the materials was investigated. It was found that at the highest laser intensity (1.4 × 10⁸ W/M²) there was a significant increase in defects. However, lower laser intensity was found which did not produce defects and was used in the studies of the effect of oxidation on the spectra.     

A durable plastic substrate for surface-enhanced Raman spectroscopy

A novel durable substrate has been prepared for surface-enhanced Raman spectroscopy (SERS). The substrate is fabricated by reduction of silver nitrate using poly(vinyl pyrrolidone) (PVP) polymer as stabilizers. The SERS-active particles are based on poly(methylmethacrylate) (PMMA) materials, producing stable and optically translucent substrates. The stability of silver particles on the substrate was demonstrated by characterizing the localized surface plasmon resonance (LSPR) band of the elemental silver particles. The SERS activity was evaluated by detecting the signal from Raman probe molecules, Rhodamine 6G (R6G). This plastic substrate material is easy to prepare, inexpensive, and sturdy for SERS applications.     

Disease-related proteins determination based on surface-enhanced Raman spectroscopy

Abstract

Surface-enhanced Raman spectroscopy (SERS) is a promising platform for simple, rapid, and economical protein quantitation and analysis and can achieve much lower detection limits for the ultrasensitive detection of proteins and a much wider linear concentration range for quantitative analysis than other methods can. In addition, SERS can provide a large amount of fingerprint information for the individual components of a mixture through SERS effects, which are sensitive and selective for different types of proteins and protein mixtures. In general, the occurrence and development of diseases are accompanied by changes in the content or structure of biomarkers (disease-related proteins). Here, we provide an overview of the SERS technique and its applications to disease-related protein determination. Different diseases, such as Alzheimer’s disease (AD), cardiac muscle tissue injury, and multicancer, are discussed and exhibit potential utility in biomarker detection and diagnosis. SERS opens a new path to the early diagnosis of critical diseases, which will effectively reduce human suffering and mortality.     

Fabrication of nanostructured silver substrates for surface-enhanced Raman spectroscopy

Four nanostructured Ag substrates have been fabricated with different surface morphologies and tested with surface-enhanced Raman scattering (SERS) experiments by adsorption of adenine. Their SERS efficiency has been compared and related to the surface roughness resulting from atomic force microscopy measurements. Chemical etching of silver by thiourea/Fe(III)nitrate produces homogeneously roughened plates, exhibiting the largest three-dimensional surface and the best SERS enhancement. They mostly exhibit surface protrusions with sizes around 200 nm, thus matching the best condition for obtaining SERS enhancement by laser excitation at 785 nm. This is quite important in the case of biomolecules, whose samples often present strong fluorescence bands, which usually are not observed with red-shifted exciting lines. Moreover, these Ag platforms, owing to their uniform nanostructured surfaces, are suitable for obtaining reproducible results from microRaman investigation. In conclusion, the present nanofabrication of Ag surfaces allows obtaining SERS-active substrates, which combine high reproducibility and sensitivity and can be successfully employed in the molecular recognition of different organic ligands or biomolecules like nucleic acids and proteins.     

Discrimination of NPC cell lines associated with malignant types using Raman spectroscopy

Nasopharyngeal carcinoma (NPC) is subdivided into four categories according to both the characterization of the NPC cell and their radiotherapy reaction. To discriminate these kinds of NPC, the representative cultured cell types (CNE1, CNE2, 5-8F, and 6-10B) are explored by single-cell micro-Raman spectroscopy (RS). The collected spectra are analyzed and compared by principal component analysis (PCA) and linear discriminate analysis (LDA). The algorithm is shown to have the lowest specificity and sensitivity of 89 and 92% for NPC division. These results demonstrate that it is a potentially clinical application for Raman spectroscopy to diagnosis NPC tissue types.     

Gold nanoparticle-coated silicon cone array for surface-enhanced Raman spectroscopy

ABSTRACT

We demonstrate a silicon cone array substrate coated with gold nanoparticles and which was highly sensitive, homogeneous, and provided a large area for surface-enhanced Raman spectroscopy (SERS). A deep reactive ion-etching process was used to fabricate the high-density silicon cone array, and gold nanoparticles were formed on the silicon cone surface by magnetron sputtering. The substrate was tested with 10^?6 M rhodamine 6 G solution. Enhancement of the substrate was about 60-fold greater than that of flat substrate. Moreover, SERS signals obtained from 24 random areas on the substrate showed good homogeneity with an average standard deviation of 3.9%.     

Near-infrared surface-enhanced Raman spectroscopy of chemisorbed compounds on gold colloids

Near-infrared surface-enhanced Raman scattering (SERS) spectra have been measured for strongly chemisorbed compounds, such as 4-mercaptopyridine and thiophenol, on gold colloids in mixed solvents of ethanol and water using a diode laser as an excitation source. From UV-vis spectroscopy, the aggregated gold colloids show a broad absorbance band through the visible to the near-infrared after adding chemisorbing compounds. The absorption maximum is located in the range 750–850 nm, permitting the use of a near-IR source (826 nm) for the first time in SERS of gold colloid systems. The estimated enhancement is on the order of 10⁵. Transmission electron microscopy of aggregated gold particles revealed a cluster morphology. The aggregated mixed-solvent colloids were more stable than those prepared in water, and were useful in dissolving compounds with poor water solubility.     

Determination of dimethoate and phosmet pesticides with surface-enhanced Raman spectroscopy

ABSTRACT

Surface-enhanced Raman spectroscopy spectra of dimethoate and phosmet pesticides were recorded using a Klarite substrate. Significant enhancements were achieved with dimethoate over a concentration range of 0.5–10 µg mL^?1 and phosmet over a concentration range of 0.1–10 µg mL^?1. The best prediction model for dimethoate pesticide was achieved with a correlation coefficient of 0.940 and a root mean square error of prediction of 0.864 µg mL^?1, with the first derivative and standard normalized variate data preprocessing, and the best prediction model of phosmet pesticide was achieved with a correlation coefficient of 0.949 and a root mean square error of prediction of 0.741 µg mL^?1 with the first derivative data preprocessing. Our study shows that pesticides, including dimethoate and phosmet, could be quantitatively measured at as low as 0.5 µg mL^?1 level using surface-enhanced Raman technology coupled with a Klarite substrate and the results indicated that surface-enhanced Raman spectroscopy with a Klarite substrate has potential for the analysis of dimethoate and phosmet residues.     

Quantitative analysis of chromate (CrVI) by normal Raman spectroscopy and surface-enhanced Raman spectroscopy using poly(diallyldimethylammonium) chloride-capped gold nanoparticles

Chromate (Cr^VI) has emerged as a widespread environmental contaminant found in groundwater and surface water, and there is a great need for rapid detection and monitoring of this contaminant. Normal Raman scattering (NRS) spectroscopy with a detection limit of Cr^VI at concentrations of 0.2 g/L was attached. And surface-enhanced Raman scattering (SERS) spectroscopy technique was found to be capable of detecting Cr^VI at concentrations as low as 2.5 mg/L using poly(diallyldimethylammonium) chloride modified gold nanoparticles (PDDA-AuNPs) as a substrate. The SERS substrate was successfully fabricated by combining the selfassembly technique with a heat-treatment-based strategy using poly(diallyldimethylammonium) chloride (PDDA) as the reducing and stabilizing agents. With the 520 cm^?1 band of silicon as internal standard, band intensity ratios of Cr^VI to silicon, that is I ₉₀₂/I ₅₂₀, were found to have a quantitative relationship with a large concentration range of Cr^VI from 0.2 to 20.0 g/L for NRS (R ² = 0.994) and from 2.5 to 25.0 mg/L for SERS (R ² = 0.980), respectively. Besides, the SERS methodology was reproducible, and susceptible to the interference of pH value. The optimum pH for Cr^VI detection by SERS was 3.38. The application of NRS and SERS showed high practical potential for rapid screening and routine analysis of Cr^VI in environmental samples.     

Self-assembly 2D plasmonic nanorice film for surface-enhanced Raman spectroscopy

As an ultrasensitive sensing technology, the application of surface enhanced Raman spectroscopy (SERS) is one interesting topic of nano-optics, which has huge application prospectives in plenty of research fields. In recent years, the bottleneck in SERS application could be the fabrication of SERS substrate with excellent enhancement. In this work, a two-dimensional (2D) Ag nanorice film is fabricated by self-assembly method as a SERS substrate. The collected SERS spectra of various molecules on this 2D plasmonic film demonstrate quantitative detection could be performed on this SERS substrate. The experiment data also demonstrate this 2D plasmonic film consisted of anisotropic nanostructures has no obvious SERS polarization dependence. The simulated electric field distribution points out the SERS enhancement comes from the surface plasmon coupling between nanorices. And the SERS signals is dominated by molecules adsorbed at different regions of nanorice surface at various wavelengths, which could be a good near IR SERS substrate for bioanalysis. Our work not only enlarges the surface plasmon properties of metal nanostructure, but also exhibits the good application prospect in SERS related fields.     

Silver-coated Si nanograss as highly sensitive surface-enhanced Raman spectroscopy substrates

We created novel surface-enhanced Raman spectroscopy (SERS) substrates by metalization (Ag) of Si nanograss prepared by a Bosch process which involves deep reactive ion etching of single crystalline silicon. No template or lithography was needed for making the Si nanograss, thus providing a simple and inexpensive method to achieve highly sensitive large-area SERS substrates. The dependence of the SERS effect on the thickness of the metal deposition and on the surface morphology and topology of the substrate prior to metal deposition was studied in order to optimize the SERS signals. We observed that the Ag-coated Si nanograss can achieve uniform SERS enhancement over large area (∼1 cm ×1 cm) with an average EF (enhancement factor) of 4.2×10⁸ for 4-mercaptophenol probe molecules. Electronic Supplementary Material  The online version of this article () contains supplementary material, which is available to authorized users.     

表面增强拉曼光谱生物成像技术及其应用

基于表面增强拉曼光谱的成像分析方法具有频带窄,水溶液背景弱,稳定性好,高特异性等优势已成为生物成像领域的优良选择。拉曼成像技术拓展了拉曼光谱的应用范围,使其不再只是检测单点化学成分的手段,而进一步用于对评价区域内化学物质成分、分布及变化进行整体统计和描述。本文探讨了表面增强拉曼散射的原理及增强机制,介绍了基于表面增强拉曼光谱的拉曼成像技术,并对其在无标记成像及带标记成像中的细胞成像、活体成像,特别是其在生物医学方面的应用进行了详细论述,最后讨论了表面增强拉曼光谱生物成像技术存在的问题,展望了该项技术的研究和应用前景。     

表面增强拉曼光谱技术在多环芳烃检测中的应用

多环芳烃(polycyclic aromatic hydrocarbons,PAHs)是一类致癌性很强的环境污染物.由于PAHs分子不含有能与金属配位或键合的官能团,因此很难利用SERS技术对其进行直接检测.本文综述了近年来表面增强拉曼散射(surface-enhanced Raman scattering,SERS)...     

Application of monitoring methodology in carbon complex contained solution using surface-enhanced Raman spectroscopy (SERS)

Raman spectroscopy is employed to obtain information that cannot be obtained using other technologies, using inelastic scattering. The development of laser technology enables Raman spectroscopy to overcome its limits and succeed in various fields. For example, compared with other analysis methods that use light, it does not require a sample preparation or long measuring time—thus, it is a great breakthrough for in situ process applications. Also, it is difficult to analyze functional groups that are combined and the influence on the reaction is analyzed during the reaction in chemical solutions. Therefore, Raman spectroscopy provides an analytic method and assists in every step to increase the accuracy of the chemical process. Lately, developed surface-enhanced Raman spectroscopy (SERS) are used in precise analyzing methods. High-resolution SERS needs a specific substrate to satisfy each purpose. Raman spectroscopy is now advanced to be more a powerful analytic tool, combined with surface-enhancing technology, atomic force microscopy (AFM), and other technology.     

Application of surface-enhanced Raman in skin cancer by plasma

We have developed a mouse squamous cell carcinomas (SCC) model by diniethylbenzanthracene (DMBA) and ultraviolet (UVB). A silver colloid as SERS-active substrates is used for detecting the blood plasma of mouse. The relative intensity of the band at 942 and 1499 cm⁻¹ is higher in SCC model than in healthy one. Therefore, it can be used as an important “fingerprint” in order to diagnose these diseases. Results show us how to get high signal-to-noise ratio of biological macromolecules surface-enhanced Raman scattering spectra in blood plasma. And also offer useful help for understanding the rich molecular structure information in biological tissues. It provides a molecular spectroscopy way for early detection of disease in blood plasma.