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Persistent organic pollutants (POPs) have attracted significant attention because of their bioaccumulation, persistence, and toxicity. As anthropogenic products, POPs mainly contain polychlorinated biphenyls (PCBs), organochlorine pesticides (OPs), and polycyclic aromatic hydrocarbons (PAHs), and they pose a great threat to human health and the environment. To deal with these toxic contaminants, many different kinds of strategies for sensitively detecting POPs have been developed, such as high performance liquid chromatography (HPLC), surface enhanced Raman spectroscopy (SERS), and fluorescence. This paper mainly summarized the achievements of spectroscopy technologies, which generally consist of SERS, surface plasmon resonance (SPR), and fluorescence, in the detection of low-concentration POPs in different matrices. In addition, a retrospective summary is made on several critical considerations, such as sensitivity, specificity and reproducibility of these spectroscopy technologies in practical applications. Finally, some current challenges and future outlooks for these spectroscopy technologies are provided in regards to environmental analysis. [ABSTRACT FROM AUTHOR]

The quest for detecting bacteria has gained momentum in food and beverage industry for preventing spoilage of products to maintain requisite quality. The present paper describes the development of a SERS immunosensor for the detection of model pathogen, S. typhimurium using strategically synthesized functionalized polymeric magnetic nanoparticles (FPMNPs) as effective capture probe and immunomagnetic separator. The synthesized probe contains surface diketonic functionalities which covalently link with amino groups of antibodies against Salmonella common structural antigen (CSA-1-Ab) and hence specifically captured the target bacteria. Magnetic core of nanoparticles facilitated easy separation of target bacteria from the milieu of non-specific molecules. Gold nanoparticles (GNPs) modified with CSA-1-Ab and external Raman reporter molecules (RRM) were used as signal probes. We compared the signalling attributes of 4-mercapto benzoic acid (MBA) and 5,5′-dithiobis(succinimidyl-2-nitrobenzoate) (DSNB) as RRMs. Capture and signal probes sandwich the target bacteria upon its addition, generating Raman signal from the 'hot-spots' created by signal probe. Under optimal conditions, the SERS intensities of MBA and DSNB at 1588 and 1336 cm−1 respectively were used to measure the concentration of the pathogen in the range of 101-107 cells mL−1. Limit of detection (LOD) of MBA and DSNB based immunosensor was measured as 100 cells mL−1, and 10 cells mL−1 respectively. Moreover, appreciable recovery (82–114%) was recorded for sensing method for different spiked food products. Thus, the developed magnetically assisted SERS immunosensor is sensitive, specific and has strong potential to be used for detecting contamination in food samples in field conditions. Image 1 • Successful capturing and separation of. S. typhimurium on functionalized polymeric magnetic nanoparticles. • Developed DSNB based SERS immunosensor is very sensitive as compared to conventional ELISA. • It is specific and reproducible even in presence of co-contaminant cross-reactant microbes. • Developed immunosensor shows good recovery in real food samples contaminated with S. typhimurium. [ABSTRACT FROM AUTHOR]

Highlights • We proposed a dual mode lateral flow assay for the detection of Campylobacter jejuni. • The novel assay was based on colorimetric and spectroscopic properties of AuNR@Pt. • This assay possesses low detection limit and wide linear range. Abstract Campylobacter jejuni (C. jejuni) is considered one of the most common cause of human gastroenteritis. Aiming to detect C. jejuni in food products rapidly and sensitively, a dual mode lateral flow assay, based on the peroxidase mimicking and surface enhanced Raman scattering (SERS) enhancement properties of platinum coated gold nanorods (AuNR@Pt), was developed in this study. Under color mode and SERS mode, the proposed assay showed good linear response in the range of 102–106 cfu/mL and 102–5 × 106 cfu/mL with limits of detection of 75 cfu/mL and 50 cfu/mL, respectively (S/N = 3). Furthermore, the reliability of the dual-readout lateral flow assay (LFA) was successfully demonstrated by the application on milk samples, in which the recoveries ranged from 89.33% to 107.62%. Overall, the immunochromatographic assay developed in this work is promising and has good chance to be employed for sensitive detection of C. jejuni in food products. [ABSTRACT FROM AUTHOR]

Featured Application: In this research we propose a novel method for detecting Alzheimer's disease. This method involves the use of surface enhanced Raman spectroscopy in combination with multivariate statistical analysis. Based on the results of the proof-of-concept study, we have successfully demonstrated the potential of the method to identify Alzheimer's disease through analysis of blood serum. With further work, this method could be developed into a novel clinical assay for the effective and accurate diagnosis of Alzheimer's disease. Alzheimer's disease (AD) is the most common form of dementia worldwide and is characterized by progressive cognitive decline. Along with being incurable and lethal, AD is difficult to diagnose with high levels of accuracy. Blood serum from Alzheimer's disease (AD) patients was analyzed by surface-enhanced Raman spectroscopy (SERS) coupled with multivariate statistical analysis. The obtained spectra were compared with spectra from healthy controls (HC) to develop a simple test for AD detection. Serum spectra from AD patients were further compared to spectra from patients with other neurodegenerative dementias (OD). Colloidal silver nanoparticles (AgNPs) were used as the SERS-active substrates. Classification experiments involving serum SERS spectra using artificial neural networks (ANNs) achieved a diagnostic sensitivity around 96% for differentiating AD samples from HC samples in a binary model and 98% for differentiating AD, HC, and OD samples in a tertiary model. The results from this proof-of-concept study demonstrate the great potential of SERS blood serum analysis to be developed further into a novel clinical assay for the effective and accurate diagnosis of AD. [ABSTRACT FROM AUTHOR]

In this work, the surface engineering method is used to produce Mn helical star-shaped (pine-tree-like) nanosculptured thin films with three-, four-, and fivefold symmetries on Cu substrates using an oblique angle deposition technique together with rotation of the sample holder at certain angles. Nano structure and morphologies of the produced samples were obtained by means of atomic force microscope and field emission scanning electron microscope. Raman spectroscopy of the Mn/Cu samples impregnated by 4,4′-bipyridine (C10H8N2) solution with different concentrations, zidovudine (C10H13N5O4), and L-histidine (C6H9N3O2) was performed using 532 nm laser wavelength. A high degree of enhancement is achieved on Raman spectroscopy of all of these specimens. Comparison of the surface-enhanced Raman spectroscopy (SERS) results for 4,4′ bipyridine (bipy) obtained in this work with the published literature using Ag and Au substrates in different shapes showed a significant enhancement improvement by using Mn sculptured structures. Reduction of the bipy concentration changed the enhancement factor. Enhancement factors of 107 and 105 were obtained for threefold symmetry sample using 2.885 × 10–2 and 10–3 mol L–1 bipy concentrations, respectively. Surface-enhanced Raman spectroscopy results of this work show that Mn nanostructures designed and engineered in this work can not only replace Ag and Au materials, but also provide a much higher enhancement factor. [ABSTRACT FROM AUTHOR]

Featured Application: The prepared MIHs doped with positively charged Au NPs show excellent surface-enhanced Raman scattering activity, could be used as efficient SERS substrates for the detection of synthetic colorants. A polyacrylamide-based molecularly imprinted hydrogel (MIH) doped with positively charged gold nanoparticles (Au NPs) has been synthesized via a free radical polymerization of acrylamide (AM) aqueous solution containing positively charged Au NPs as a Raman active substrate, New Red colorant as a template molecule, N,N'-methylenebis(acrylamide) as a crosslinking agent, and potassium persulfate as an initiator. The Au NPs-doped MIHs were subsequently explored as a Raman active substrate for the sensitive and selective detection of New Red colorant via surface-enhanced Raman spectroscopy (SERS). The logarithmic intensity of the characteristic peak of New Red at 1572 cm−1 was proportional to the logarithmic concentration of New Red with a detection linear range of 1.64 × 10−6 to 1.64 × 10−4 M and a limit of detection (LOD) of 1.64 × 10−7 M. The recoveries ranged from 86.3% to 100.6% with a relative standard deviation (RSD) in the range of 2.3% to 7.7%. The RSD and recovery rates for the detection of New Red spiked in a sports drink sample were 1.8% to 7.7% and 91.0% to 97.1%, respectively. These results showed that SERS combined with MIHs as Raman active substrates could provide a sensitive, selective, and effective approach for the detection of the New Red colorant in beverage matrix. [ABSTRACT FROM AUTHOR]

Copyright of Food Research & Development is the property of Food Research & Development Editorial Department and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Highlights • Proof of concept of an ultra-sensitive biosensors for analytical devices with SERS. • Nanoporous gold functionalized with a target-directed antibody (Ab anti-HSA). • Acquisition of detailed SERS maps at different HSA concentration. • Chemometric approach to data analysis and sensor calibration. • Biosensor gives quantitative analysis in ultra-low concentrations (0.1 ng/l). Abstract The development of a new generation of ultra-sensitive sensors for analytical and bio-diagnostic devices requires a strong signal in front of very small quantity of analyte, often present in complex and interfering matrix. Taking advantage of peculiar plasmonic properties of nanoporous gold (NPG), a promising sensor for selective detection of Human Serum Albumin (HSA), a proof-of-concept bioanalyte, was prepared and tested in a conventional micro-Raman spectrometer using Surface Enhanced Raman Spectroscopy (SERS). NPG was synthesized by chemical de-alloying of an amorphous precursor, Au 20 Cu 48 Ag 7 Pd 5 Si 20 , starting from melt spun ribbons. A fully de-alloyed ribbon with ligaments of about 60 nm was obtained after 4 h of de-alloying at 70 °C and 10 M HNO 3 + 0.5 M HF. This material is self-standing, mechanically resistant, and suitable for wide range of applications. At this stage, NPG is SERS-active toward several molecules, including pyridine, bi-pyridine, and rhodamine at very low concentration. In order to obtain the selective binding properties required to detect molecules in bio-diagnostic applications, immuno-functionalization of NPG was carried out by using an anti-HSA antibody (Ab-anti-HSA) covalently grafted on gold ligaments via the 4-aminothiophenol (4ATP) Raman probe, yielding the SERS-active nanohybrid NPG-4ATP-Ab. SERS signal recorded at increasing HSA concentrations was used for the acquisition of SERS maps and a chemometric regression model allowed to calibrate the sensor. In the best experimental conditions, we were able to get quantitative analysis of HSA at ultra-low concentrations (0.1 ng/l) with SERS. The methodology proposed in this paper has to be considered a major step toward a calibrated device for ultra-sensitive detection of biomolecules by SERS detection. [ABSTRACT FROM AUTHOR]

Abstract An ultrasensitive method for the kanamycin (KANA) detection in milk sample using surface-enhanced Raman spectroscopy-based aptasensor was employed in the current study. Double strand DNA binding bimetallic gold@silver nanoparticles were developed as a sensing platform. Probe DNAs were first embedded on the surface of gold nanoparticles by the end-modified thiol, and after silver shell encapsulating, KANA aptamer DNAs with the Raman reporter Cy3 were then hybridized with probe DNAs by complementary base pairing. Results showed that with increase in the KANA concentration, the Raman intensity of Cy3 decreased. Besides achieving selectivity, an ultralow detection limit of 0.90 pg/mL, a broad linear relationship ranging from 10 μg/mL to 100 ng/mL in aqueous reagent and satisfactory recoveries of 90.4–112% in liquid whole milk were obtained. The result of actual sample proved that this aptasensor was promising in trace determination of KANA residue. Graphical abstract fx1 Highlights • Au@Ag NPs-ds DNA was synthesized and characterized. • Kanamycin concentrations could be monitored by the Raman intensity of Cyanine-3. • The aptamer-sensor showed high selectivity and sensitivity for kanamycin detection. • This method was successfully applied to determine kanamycin in milk. • This method was superior in detection limits compared with existing methods. [ABSTRACT FROM AUTHOR]

Highlights • A SERS-based aptasensor was fabricated for MC-LR detection. • The problem of the conventional immunological technique was overcome. • LOD was as low as 0.002 ng/mL. Abstract We developed a novel aptasensor based on surface enhanced Raman spectroscopy (SERS) and applied it for highly sensitive detection of microcystin-LR (MC-LR). In this work, MC-LR aptamer and its corresponding complementary DNA fragments (cDNA) were conjugated to gold nanoparticles (AuNPs) and magnetic nanoparticles (MNPs), respectively. Then, MC-LR aptamer-AuNPs and cDNA-MNPs conjugates were used as signal probes and capture probes, respectively. The proposed assay exhibited a linearity range from 0.01 to 200 ng/mL with the limit of detection (LOD) of 0.002 ng/mL. In addition, the reliability of the novel approach was validated by detecting different levels of MC-LR spiked in tap water samples. Overall, the novel aptasensor paves a new way for rapid and accurate determination of MC-LR and can be referred to detect other hazardous substances in water products. [ABSTRACT FROM AUTHOR]

Highlights • MIPs synthesized for atrazine had high-selective binding capacity towards atrazine. • MIPs-SPE achieved >93% recovery of atrazine from spiked apple juice samples. • Colorimetric assay using AuNPs (size 43 nm) achieved a <0.01 mg L−1 detection limit. • SERS assay using AuNPs (size 27 nm) achieved a <0.005 mg L−1 quantification limit. • MIPs-AuNPs colorimetric/SERS sensor can determine atrazine in foods within 30 min. Abstract Rapid and reliable determination of atrazine, a common chemical contaminant, in agri-foods is highly necessary. We reported a novel dual-chemosensor coupling, a separation [molecularly imprinted polymers (MIPs)], an instrumental-free detection [gold nanoparticles (AuNPs)-based colorimetric assay] and an instrument-based quantification [surface enhanced Raman spectroscopy (SERS)] method for high-throughput and sensitive determination of atrazine in apple juice. Used as the selective sorbent for the solid phase extraction, MIPs effectively extracted atrazine from apple juice with high recoveries (∼93%). AuNPs of different sizes (large; medium; and small) performed differently in the two analytical methods. Large-AuNPs provided the highest sensitivity in colorimetric analysis (<0.01 mg L−1), while medium-AuNPs achieved the lowest limit of detection (0.0012 mg L−1) and quantification (0.0040 mg L−1) in SERS analysis. With minor modifications, protocols for both analytical methods can rapidly detect and/or quantify atrazine in different food products complying with the Health Canada regulation (0.005 mg L−1). [ABSTRACT FROM AUTHOR]

Copyright of Journal of Food Safety & Quality is the property of Journal of Food Safety & Quality Editorial Department and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Surface Enhanced on Infrared Absorption (SEIRAS) and Raman Spectroscopy (SERS) are nondestructive analytic techniques used to detect low concentrations and recognize the fingerprints of molecules. The recognition of the absorption from samples by conventional infrared spectroscopy (IR) via Attenuated Total Reflection (ATR) is difficult for molecules with a low signal strength. However, developed structures with SERS and SEIRAS effect present problems such as high cost, low stability, and low compatibility. Research into new media to obtain greater amplification is largely based on the creation of nanoscale structures with symmetrical arrangements and reproducible distances, resulting in aggregates of nanoparticles that help generate hot spots which are active for amplification. The sol-gel and electrospinning method for the obtention of ceramics provides an alternative means by which to produce said substrates. Fibers of nanometric scale provide an increase of surface area which allows more contact to occur with analytes. Consequently, in this study, a silica-titania-silver nanostructured support that amplifies signal intensity for Raman and infrared spectroscopy was developed. The silica-titania support was developed by sol-gel and electrospinning techniques, and the as spun fibers were treated at 800 °C. Then, the ceramic fibrous membrane was placed on conductive indium tin oxide plastic to be doped with silver using an electroplating technique, varying the silver nitrate concentration (5, 10 and 20 mM), as well as electrodeposition times (1, 2, 5 and 10 min), with a constant voltage (1 V). Twelve different supports were obtained that showed amplification. The enhancement of infrared signals from pyridine and crystal violet molecules adsorbed on silica-titania-silver (SiO2–TiO2–Ag) nanofibers was studied in situ by Attenuated Total Reflection-Fourier Transformed Infrared Spectroscopy (ATR-FTIR). The highest amplification was obtained by the support doped at 10 min in a 10 mM concentration, with an amplification factor of 2.74 in the band localized at 3301 cm−1. In Raman spectroscopy, the highest amplification factor was 27.03, on the support doped for 5 min at a concentration of 5 mM.

Extracellular vesicles (EVs) are membrane-enclosed structures ranging in size from about 60 to 800 nm that are released by the cells into the extracellular space; they have attracted interest as easily available biomarkers for cancer diagnostics. In this study, EVs from plasma of control and prostate cancer patients were fractionated by differential centrifugation at 5000× g, 12,000× g and 120,000× g. The remaining supernatants were purified by ultrafiltration to produce EV-depleted free-circulating (fc) fractions. Spontaneous Raman and surface-enhanced Raman spectroscopy (SERS) at 785 nm excitation using silver nanoparticles (AgNPs) were employed as label-free techniques to collect fingerprint spectra and identify the fractions that best discriminate between control and cancer patients. SERS spectra from 10 µL droplets showed an enhanced Raman signature of EV-enriched fractions that were much more intense for cancer patients than controls. The Raman spectra of dehydrated pellets of EV-enriched fractions without AgNPs were dominated by spectral contributions of proteins and showed variations in S-S stretch, tryptophan and protein secondary structure bands between control and cancer fractions. We conclude that the AgNPs-mediated SERS effect strongly enhances Raman bands in EV-enriched fractions, and the fractions, EV12 and EV120 provide the best separation of cancer and control patients by Raman and SERS spectra.

Portable devices for rapid, automated and quantitative nucleic acid detection from whole blood is highly desirable for point-of-care (POC) molecular diagnostics. Conventional sequencing and polymerase chain reaction methods usually require trained personnel to deal with the time-consuming procedures, from sample purification to target amplification. To promote POC disease diagnosis and monitoring, we herein developed a hand-powered microfluidic chip for circulating tumor DNA (ctDNA) analysis from whole blood. On the one hand, the chip allowed rapid blood cell removal through a microfluidic filter trench. On the other hand, the ultrasensitivity of surface enhanced Raman spectroscopy (SERS) technique enabled amplification-free DNA mutation screening. Meanwhile, a finger-driven vacuum system was incorporated into the system, which achieved microfluidic pumping without external pumps, tubes or power sources. The developed SERS chip achieved fast screening of EGFR E746-A750 mutation in 35 min, reaching a limit of detection down to 100 fM in blood. Due to the simplicity, fast analysis, low cost and quantitative readout, the chip is expected to expand the availability of molecular diagnosis into resource-limited and bedside settings. • A microfluidic chip is developed for circulating tumor DNA analysis from whole blood. • On-chip blood preprocessing is accomplished with a finger-driven vacuum system. • Amplification-free detection of DNA mutation is achieved using SERS technique. • DNA mutation screening in whole blood sample is accomplished in 35 min. [ABSTRACT FROM AUTHOR]

Rapid and accurate detection of rare circulating tumor cells (CTCs) in human blood still remains a challenge. We present a surface enhanced Raman spectroscopy (SERS) method based on aptamer-SERS bio-probe recognition coupled with micropore membrane filtration capture for the detection of CTCs at single cell level. The parylene micropore membrane with optimized micropore size installed on a filtration holder could capture bio-probe labeled CTCs by gravity in less than 10 s, and only with very less white blood cells (WBCs) residual. In order to facilitate the synthesis of the aptamer-SERS bio-probe, ethyl acetate dehydration method was established. The bio-probe can be rapidly synthesized within 2 h by binding SH-aptamer to 4- mercaptobenzoic acid (4-MBA) modified AuNPs with the help of ethyl acetate. The SERS bio-probe with selected specific aptamer could distinguish single human non-small cell lung cancer A549 cells from residual WBCs on membrane efficiently and reliably based on their Raman signal intensity difference at 1075 cm−1. Through the filter membrane coupled with aptamer-SERS bio-probe system, even 20 A549 cells in blood solution simulating CTCs sample can be detected, which the recovery rate and recognition rate are more than 90%. This method is rapid, reliable and cost-effective, which indicates a good prospect in clinical application for CTCs detection. An aptamer-SERS bio-probe was fabricated by binding specific aptamer of A549 tumor cell to Raman reporter 4-MBA modified AuNPs. CTCs sample labeled by the bio-probes can be captured on micropore parylene membrane with optimized micropore size by quick filtration. Single CTC on filter membrane was identified by SERS mapping method. [Display omitted] • Parylene membrane with suitable pore size capture CTCs rapidly and remove most WBCs. • Bioprobe synthesis with ethyl acetate dehydration in 2 h and keep Raman signal. • Selected aptamer ensure specificity for A549 cells compared to other cell and WBCs. • Low cost, time-saving, high capture efficiency and detection specificity for CTCs. [ABSTRACT FROM AUTHOR]

Genomic biomarkers of cancer are based on changes in nucleic acids, which include abnormal expression levels of some miRNAs, point mutations in DNA sequences, and altered levels of DNA methylation. The presence of tumor-related nucleic acids in body fluids (blood, saliva, or urine) makes it possible to achieve a non-invasive early-stage cancer diagnosis. Currently existing techniques for the discovery of nucleic acids require complex, time-consuming, costly assays and have limited multiplexing abilities. Surface-enhanced Raman spectroscopy (SERS) is a vibrational spectroscopy technique that is able to provide molecular specificity combined with trace sensitivity. SERS has gained research attention as a tool for the detection of nucleic acids because of its promising potential: label-free SERS can decrease the complexity of assays currently used with fluorescence-based detection due to the absence of the label, while labeled SERS may outperform the gold standard in terms of the multiplexing ability. The first papers about SERS-based methods for the measurement of genomic biomarkers were written in 2008, and since then, more than 150 papers have been published. The aim of this paper is to review and evaluate the proposed SERS-based methods in terms of their level of development and their potential for liquid biopsy application, as well as to contribute to their further evolution by attracting research attention to the field. This goal will be reached by grouping, on the basis of their experimental protocol, all the published manuscripts on the topic and evaluating each group in terms of its limit of detection and applicability to real body fluids. Thus, the methods are classified according to their working principles into five main groups, including capture-based, displacement-based, sandwich-based, enzyme-assisted, and specialized protocols. [Display omitted] • SERS-based detection of miRNA level changes, DNA point mutations, and DNA methylation level alterations in body fluids have good potential for early-stage cancer diagnosis. • Biological protocols designed for the selective detection of the target DNAs/miRNAs have been reviewed and grouped into the following categories: capture, displacement, sandwich, cleavage, and specific protocols. • The protocols have been arranged according to the increasing complexity of the assays and evaluated in terms of their performance for liquid biopsy application. As a result, one-to-step protocols have shown good LODs, applicability in body fluids, and multiplexing abilities, especially for miRNA detection. • In general, labeled protocols outperform label-free assays by reaching the LODs as low as 10 − 16 M and detecting the target miRNA/DNA in the complex matrices, such as total RNAs/DNAs and real body fluids. However, the performance of the label-free protocols can be improved by developing highly sensitive SERS substrates. • Thus, there is a potential to develop relatively simple SERS-based protocols for liquid biopsy applications with promising LODs and multiplexing abilities, but more work should be conducted in this direction. [ABSTRACT FROM AUTHOR]

[Display omitted] • Developed a SERS chip for ultrasensitive detection of cadmium. • The LOD of the sensor was 1.33 pM with distilled water. • The sensor could detect cadmium ions in the real environmental samples. • This method can shed light on the development of SERS-based sensors. Cadmium is a representative carcinogenic heavy metal. Because of the long biological half-life of cadmium, it is critical to prevent and detect cadmium inflow into the body. In this study, we developed the biomimetic magneto-gold nano-urchin (MGNU)-based surface-enhanced Raman scattering (SERS) chip for ultrasensitive detection of cadmium. The MGNU SERS chip was facilely fabricated using three-dimensional (3D) printed magnetic molds. The 3D printed magnetic molds were designed for contributing to (1) making hydrophobic/hydrophilic areas and (2) magnetic SERS enhancement by attracting the MGNUs. To validate the performance of the MGNU SERS chip, we conducted electromagnetic simulations and measurements of SERS efficiencies. Consequently, we detected cadmium ions up to 1.33 pM in distilled water. Moreover, we succeeded to detect cadmium ions in the real environmental samples up to 2.76 pM in the tap water and 14.21 pM in the human blood plasma, respectively. The MGNU SERS chip is a powerful SERS substrate that can be used in various spectrometer-based sensing platforms. [ABSTRACT FROM AUTHOR]

[Display omitted] • Semi-quantitative analysis of limited pollutants was conducted according to Raman intensity. • The Raman intensity at 709 cm−1 is greater than 2.7 × 103, the concentration of melamine is determined to be greater than the MRL. • The LOD of the semi-quantitative method is 2.5 mg/kg, which is 10 times lower than that of the existing method (25 mg/kg). Melamine is one of the common limited contaminations in dairy products. The traditional detection method has a long period and complicated pretreatment process. The rapid detection method is the better method to solve the screening of limited contaminations. In this paper, taking melamine as the research object, the surface enhanced Raman spectrum of melamine in liquid milk were collected by portable Raman spectrometer, and melamine was qualitatively identified and semi-quantitatively analyzed by Raman characteristic peak and Raman intensity, and a simple and efficient rapid screening method for limited contaminations was developed. The limit of detection is 0.25 mg/kg. The probability of detection is 100% at 2.5 mg/kg, which is the same between the two laboratories, indicating that the semi-quantitative method has good repeatability. The method of melamine proposed in this study can meet the rapid screening requirements of limited contaminations at the maximum residue limit, and has a good application prospect. [ABSTRACT FROM AUTHOR]

[Display omitted] • GNPs-based fast and colorimetric biosensor for CR detection has been reported. • A nanocomposite was prepared between GNPs and Zn2+ ions. • The biosensor exhibited good selectivity to CR over interfering biochemicals. • The biosensor was able to selectively detect CR in artificial urine and clinical samples. • The LOD for CR detection was determined to be 2 µg·mL−1. This research reports the fabrication of Zn2+/gold nanoparticles (GNPs) nanocomposite for colorimetric detection of creatinine (CR) in diverse media (e.g., water, artificial urine, and urine samples) between healthy subjects and chronic kidney disease (CKD) patients. The color of GNPs in suspension changed from characteristic wine-red (λ absorption = 545 ± 5 nm) to colorless or black upon the formation of nanocomposite with Zn2+ ions. However, upon addition of CR to Zn2+/GNPs nanocomposite suspension, the characteristic wine-red color of GNPs was restored. Our experimental analysis evidently validated the hypothesis on Zn2+ induced agglomeration of GNPs and their subsequent anti-agglomeration upon the addition of CR to the Zn2+/GNPs. Overall, our approach offered highly sensitive recognition of CR with a limit of detection of 2 µg·mL−1 (R2 = 0.95) along with excellent stability (>three months), selectivity (in the presence of interfering biochemicals (e.g., urea, ascorbic acid, and glucose, glutathione, Na+, K+, Ca2+, Mg2+, PO 4 3−, and SO 4 2−)), and reproducibility (relative standard deviation ∼ 9 %). Finally, the great potential of our method for CR recognition was also confirmed by good agreement (R2 = 0.95) with the gold standard 'Jaffe' method along with the Bland-Altman analysis for urine samples between health subjects (n = 15) and CKD patients (n = 11). In near future, a quantitative lateral flow biosensor is expected to be developed for non-invasive detection of CR through the integration of the proposed approach with the machine learning tools. [ABSTRACT FROM AUTHOR]

Surface Enhanced Raman Spectroscopy is increasingly used as a sensitive bioanalytical tool for detection of variety of analytes ranging from viruses and bacteria to cancer biomarkers and toxins, etc. This comprehensive review describes principles of operation and compares the performance of immunoassays and aptamer assays with Surface Enhanced Raman scattering (SERS) detection to each other and to some other bioassay methods, including ELISA and fluorescence assays. Both immuno- and aptamer-based assays are categorized into assay on solid substrates, assays with magnetic nanoparticles and assays in laminar flow or/and strip assays. The best performing and recent examples of assays in each category are described in the text and illustrated in the figures. The average performance, particularly, limit of detection (LOD) for each of those methods reflected in 9 tables of the manuscript and average LODs are calculated and compared. We found out that, on average, there is some advantage in terms of LOD for SERS immunoassays (0.5 pM median LOD of 88 papers) vs SERS aptamer-based assays (1.7 pM median LOD of 51 papers). We also tabulated and analyzed the clinical performance of SERS immune and aptamer assays, where selectivity, specificity, and accuracy are reported, we summarized the best examples. We also reviewed challenges to SERS bioassay performance and real-life application, including non-specific protein binding, nanoparticle aggregation, limited nanotag stability, sometimes, relatively long time to results, etc. The proposed solutions to those challenges are also discussed in the review. Overall, this review may be interesting not only to bioanalytical chemist, but to medical and life science researchers who are interested in improvement of bioanalyte detection and diagnostics. [Display omitted] • SERS immunoassays and SERS aptamer-based assays can achieve high sensitivity in detection of various bioanalytes. • The calculated median LOD for SERS immuno vs SERS aptamer assays is 0.5 pM vs 1.7 pM, from 88 & 51 references, respectively • The challenges to SERS bioassays include non-specific protein binding, NP agglomeration, , extended assay time, etc. • Ways to overcome the challenges: SAMs to minimize non-specific protein binding, rotating substrates, magnetic NPs, etc. [ABSTRACT FROM AUTHOR]

[Display omitted] Spray solution combustion synthesis is proposed as a onestep method for preparation of nanostructured iron oxide–silver patchy particles for polyfunctional applications. [ABSTRACT FROM AUTHOR]

A sensitive and recyclable plasmonic nickel foam sensor has been developed for surface-enhanced Raman spectroscopy (SERS). A simple electrochemical method was used to deposit flower-shaped gold nanostructures onto nickel foam substrate. The high packing of the gold nanoflowers onto the nickel foam led to a high enhancement factor (EF) of 1.6 × 1011. The new SERS sensor was utilized for the direct determination of the broad-spectrum β-lactam carbapenem antibiotic meropenem in human blood plasma down to one pM. The sensor was also used in High Performance Liquid Chromatography (HPLC)-SERS assembly to provide fingerprint identification of meropenem in human blood plasma. Moreover, the SERS measurements were reproducible in aqueous solution and human blood plasma (RSD = 5.5%) and (RSD = 2.86%), respectively at 200 µg/mL (n = 3), and successfully recycled using a simple method, and hence, used for the repeated determination of the drug by SERS. Therefore, the new sensor has a strong potential to be applied for the therapeutic drug monitoring of meropenem at points of care and intensive care units.

The interaction of graphene with metals initiates charge-transfer interaction-induced chemical enhancements, which critically depend on the doping effect from deposited metallic configurations. In this paper, we have explored the gold nanoparticle-decorated monolayer graphene nanosheets for the large graphene-induced Raman enhancement of adsorbed analytes, indicating the surface-enhanced Raman spectroscopy (SERS) capabilities of metal-doped graphene (G-SERS). Here, the systematically sputtered Au thickness optimization procedure revealed noticeable modifications in the graphene Raman spectra and photoluminescence (PL) background quenching, which indicated favorable charge transfer through n-type doping of chemical vapor deposition-grown graphene nanosheets. The highly consistent, individually distributed morphology of the gold nanoislands over graphene nanosheets depicted a reproducibly uniform G-SERS signal with excellent relative standard deviation values (<5%), resulting in the strongest Raman intensity enhancement factors of ∼10 8 (MB) (methylene blue) and 10 7 (DPA) (2,6-pyridinedicarboxylic acid) composed of the weakest PL background. The combined charge-transfer-induced chemical enhancement and electromagnetic enhancement from individual Au nanoislands result in a lowering of detectability down to 10 -16 M (MB) and 10 -11 M (DPA) concentrations with efficient time-dependent signal stability. Additionally, the GAu demonstrated its effective (∼94.4%) photocatalytic degradation capabilities by decomposing MB dye molecules from a concentration of 1 μM to 2.52 fM within 60 min. Therefore, the prominent charge-transfer contribution through controlled Au decoration over graphene nanosheets provides a potential strategy for fabricating superior SERS sensors and photocatalysts exhibiting adequate signal consistency, stability, and photodegradation efficiency through overcoming the limitations of the traditional sensing platforms.

Abstract Pancreatic cancer is a highly lethal malignancy. Lack of early diagnostic markers makes timely detection of pancreatic cancer a highly challenging endeavor. Exosomes have emerged as information-rich cancer specific biomarkers. However, characterization of tumor-specific exosomes has been challenging. This study investigated the proof of principle that exosomes could be used for the detection of pancreatic cancer. Label-free analysis of exosomes purified from normal and pancreatic cancer cell lines was performed using surface enhanced Raman Spectroscopy (SERS) and principal component differential function analysis (PC-DFA), to identify tumor-specific spectral signatures. This method differentiated exosomes originating from pancreatic cancer or normal pancreatic epithelial cell lines with 90% accuracy. The cell line trained PC-DFA algorithm was next applied to SERS spectra of serum-purified exosomes. This method exhibited up to 87% and 90% predictive accuracy for HC and EPC individual samples, respectively. Overall, our study identified utility of SERS spectral signature for deciphering exosomal surface signature. Graphical Abstract The present study utilizes exosomes purified from pancreatic cancer and pancreatic epithelial cell lines and surface enhanced Raman spectroscopy (SERS) spectra to train an algorithm by Principle Component-Differential Functional Analysis (PC-DFA). This trained PC-DFA algorithm was subsequently applied to SERS spectra to characterize exosomes as originating from pancreatic patient or healthy patient serum with up to 90% accuracy. Unlabelled Image [ABSTRACT FROM AUTHOR]

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Graphical abstract Abstract This work shows the capability of surface-enhanced Raman spectroscopy (SERS) to detect ultratraces of cocaine (COC) in oral fluid (OF). It proposes a new solid substrate made of gold nanorods (Au NRs) to perform sensitive analyses of this complex matrix without any sample pretreatment. The Au NRs were synthetized optimizing the synthesis conditions, and then characterized and tested as SERS substrate. The presented results demonstrated that the SERS methodology was able to detect COC in OF with a limit of detection (LOD) as low as 10 ng/mL. This value was five orders of magnitude smaller than the one obtained with Raman spectroscopy (RS) and in the order of the cut-off value (8 ng/mL) established for confirmatory test of COC in OF. Besides, a multivariate analysis (OPLS-DA) applied on the samples analysed by SERS evidenced that it was possible to discriminate among various COC concentrations. These are quite positive results because even the 1 ng/mL COC concentration sample could be identified as different from the OF sample. In addition, the absence of sample pretreatment and the ease of the proposed method, allowed performing rapid and non-destructive analyses, making the method suitable for in situ forensic analyses. [ABSTRACT FROM AUTHOR]

Organophosphate compounds that are used as pesticides affect the nervous system by binding irreversibly to the active site of the enzyme acetylcholine esterase (AChE) and disrupting neuro-signaling nerve cells. In this study we characterized adsorption of paraoxon to a set of designed peptides that present different arrangements of the three amino acids of the AChE catalytic site: histidine, glutamic-acid and serine. The peptides set included two β-strands with no net charge and three β-hairpins that differ in their net charge. Circular dichroism, Thioflavin T assays and TEM images provided only qualitative insights on paraoxon binding to the different peptides. Paraoxon binding to the different peptides was measured with dialysis membrane tubes filled with the peptide solutions and suspended in a reservoir of paraoxon solution. Among all the tested peptides, the single strand peptide, denoted ssESH exhibited at 100 μM in random conformation prefibrillar state, the maximum paraoxon adsorption, with a binding mol ratio of one paraoxon per two peptides and an estimated equilibrium binding constant 5 ∗ 10 4  M −1 . The three β-hairpin peptides demonstrated that a net negative charge is unfavorable for paraoxon adsorption. Surface enhanced Raman spectroscopy measurements with ssESH enabled the detection of nanomolar adsorbed concentrations of paraoxon. [ABSTRACT FROM AUTHOR]

Surface-enhanced Raman spectroscopy (SERS) is a promising analytical tool due to its label-free detection ability and superior sensitivity, which enable the detection of single molecules. Since its sensitivity is highly dependent on localized surface plasmon resonance, various methods have been applied for electric field-enhanced metal nanostructures. Despite the intensive research on practical applications of SERS, fabricating a sensitive and reproducible SERS sensor using a simple and low-cost process remains a challenge. Here, we report a simple strategy to produce a large-scale gold nanoparticle array based on laser interference lithography and the electrophoretic deposition of gold nanoparticles, generated through a pulsed laser ablation in liquid process. The fabricated gold nanoparticle array produced a sensitive, reproducible SERS signal, which allowed Rhodamine 6G to be detected at a concentration as low as 10–8 M, with an enhancement factor of 1.25 × 105. This advantageous fabrication strategy is expected to enable practical SERS applications. [ABSTRACT FROM AUTHOR]

Objective: To establish a method for rapid determination of sufentanil concentration in rat plasma by thin layer chromatography-surface enhanced Raman spectroscopy（TLC-SERS） method. Methods: The plasma samples were separated by TLC with dichloromethane-methanol（9:1.2） as a developing agent，and then SERS was applied for qualitative and quantitative analysis of sufentanil.Linear regression was performed between the concentration of sufentanil and the intensity of the Raman characteristic peak at 1004 cm-1. The standard curve，detection limit and recovery rate were all investigated. Results: The concentration of sufentanil within the range of 0.85-85.00 μg/ml and the peak intensity of SERS at 1004 cm-1 were in good linearity. The detection limit was 0.85 μg/ml，and the recovery rates of low （4.25 μg/ml） and high concentrations （42.50 μg/ml ） were （86.00±8.15）% and （103.45±3.59）%（n=3），respectively. Conclusion: The study established a simple，rapid and practical method for the determination of sufentanil plasma concentration. [ABSTRACT FROM AUTHOR]

Surface enhanced Raman spectroscopy (SERS) substrate aimed at providing robust and reproducible enhancements is discussed. The periodic sinusoidal SiO 2 grating followed by silver evaporation is proposed for the creation of reproducible and effective SERS substrate based on surface plasmon polaritons (SPPs). Detailed optical properties theoretical and simulation studies with finite difference time domain (FDTD) are performed to achieve intense excitation SPPs. Substrate parameters such as period, amplitude of sinusoidal grating and thickness of silver layer, detailed excitation light parameters such as wavelength, polarization state and polarization angle are explored. It’s found that the enhancement factor (EF) of SERS is proportional to the efficiency of excitation SPPs. Optimal SERS response can be realized by assembling the substrate and excitation light parameters appropriately. The substrates are fabricated and an extra SERS effect of the optimal Ag/SiO 2 sinusoidal nanograting is demonstrated by the experiments. [ABSTRACT FROM AUTHOR]

In this work, a facile method coupling solid phase microextraction (SPME) with surface enhanced Raman spectroscopy (SERS) was developed for the detection of trace bisphenol A (BPA). Monolayer graphene-coated Ag nanoparticles (Ag NPs) were fabricated on the Si fiber, which made the Si fiber retain functions of both as a SERS-active substrate and SPME fiber to realize in situ rapid determination of BPA. The SERS-active SPME fiber was immersed in water to extract BPA prior to its detection by SERS. The relative standard deviation (RSD) values of the uniformity and the reproducibility of the SERS-active SPME fiber are 14% and 13%, respectively. The characteristic SERS intensity versus BPA concentration showed a linear relationship (R 2 = 0.958). Due to the combination of the SERS method with SPME, this method exhibits extremely high sensitivity and excellent stability for the detection of BPA, with a limit of detection as low as 1 μg L −1 . The method was successfully used for the determination of BPA in water samples with spiked recoveries ranging from 97% to 110%. Compared to the conventional SERS methods used for the detection of BPA, the present method not only retains the advantages of SERS but also provides several unique advantages including preconcentration of analytes, separation of analyte from sample matrices and improvement of sensitivity, thus making its promising application in environmental analysis of BPA. [ABSTRACT FROM AUTHOR]

Abstract: Plasmon‐driven catalysis on a single particle has attracted great attention in recent years, while the relationship between reaction efficiency and substrate remains to be deeply studied. Here, we demonstrate the fabrication of a novel Ag@MoS2 core‐shell single particle SERS substrate by coating MoS2 film on Ag microspheres through the pulsed laser deposition (PLD) technique, where the thickness and crystallinity of MoS2 can be effectively controlled by the PLD time and temperature. It is revealed that both the thickness and crystallinity of MoS2 can greatly influence the hot electron transfer process, and thus the plasmon‐driven reaction (4‐NTP into DMAB) efficiency and Raman enhancement of dye molecules on Ag@MoS2 substrates. Generally, high crystallinity and thin thickness of MoS2 can lead to accelerated plasmon‐driven reaction efficiency and greatly enhanced Raman signals of target molecules. This study opens up a new avenue for broadening the research area of the plasmon‐driven catalysis and Raman enhancement on the hybrid system of two‐dimensional materials and metal nanostructures. [ABSTRACT FROM AUTHOR]

Abstract: Plasmon‐driven catalysis on a single particle has attracted great attention in recent years, while the relationship between reaction efficiency and substrate remains to be deeply studied. Here, we demonstrate the fabrication of a novel Ag@MoS2 core‐shell single particle SERS substrate by coating MoS2 film on Ag microspheres through the pulsed laser deposition (PLD) technique, where the thickness and crystallinity of MoS2 can be effectively controlled by the PLD time and temperature. It is revealed that both the thickness and crystallinity of MoS2 can greatly influence the hot electron transfer process, and thus the plasmon‐driven reaction (4‐NTP into DMAB) efficiency and Raman enhancement of dye molecules on Ag@MoS2 substrates. Generally, high crystallinity and thin thickness of MoS2 can lead to accelerated plasmon‐driven reaction efficiency and greatly enhanced Raman signals of target molecules. This study opens up a new avenue for broadening the research area of the plasmon‐driven catalysis and Raman enhancement on the hybrid system of two‐dimensional materials and metal nanostructures. [ABSTRACT FROM AUTHOR]

Abstract: In this work, we developed a precise approach to analyze local proton concentration at the solid/liquid interface of electrodes, i.e. “surface pH”, during electrochemical reactions. For this, surface enhanced Raman spectroscopy (SERS) was applied to analyze pH-dependent structural changes of the -COOH group of p-mercaptobenzoic acid (p-MBA) modified onto Au nanoparticles (NPs) on the substrate close to a working electrode. Measurements using this system identified deprotonation of -COOH of p-MBA. Since preliminary experiments and density functional theory calculations suggest that the pKa of p-MBA attached to Au NPs is close to that in bulk solution, the SERS results indicate pH increase due to proton consumption by the cathodic overpotential of the working electrode. As an example, we applied this system to surface pH monitoring in electrodeposition process of Ni in an acidic bath, which indicated the validity of our method for precise detection of pH changes at electrode interfaces in situ.Graphical Abstract: [ABSTRACT FROM AUTHOR]

We fabricated a microRNA biosensor using the combination of surface enhanced Raman spectroscopy (SERS) and electrochemical (EC) techniques. For the first time, the weaknesses of each techniques for microRNA detection was compensated by the other ones to give rise to the specific and wide-range detection of miR-155. A single stranded 3′ methylene blue (MB) and 5′ thiol-modified RNA (MB-ssRNA-SH) was designed to detect the target miR-155 and immobilized onto the gold nanoparticle-modified ITO (ITO/GNP). Upon the invasion of target strand, the double-stranded RNA transformed rapidly to an upright structure resulting in a notable decrease in SERS and redox signals of the MB. For the first time, by combination of SERS and EC techniques in a single platform we extended the dynamic range of both techniques from 10 pM to 450 nM (SERS: 10 pM–5 nM and EC: 5 nM–450 nM). As well, the SERS technique improved the detection limit of the EC method from 100 pM to 100 fM, while the EC method covered single-mismatch detection which was the SERS deficiency. The fabricated single-step biosensor possessing a good capability of miRNA detection in human serum, could be employed throughout the broad ranges of biomedical and bioelectronics applications. [ABSTRACT FROM AUTHOR]

Different nano-structures of noble metals have been the conventional substrates for carrying out Surface Enhanced Raman Spectroscopy (SERS). In this paper we examine electrodeposited copper (Cu) nano-structures on pencil graphite as novel substrate to carry out SERS measurements by considering l -cystine (Cys-Cys) (dimer of the amino acid cysteine) as the probe. The formation of monolayer of the probe molecule on the substrates was confirmed using cyclic voltammetric measurements. Mode of adsorption of Cys-Cys was observed to be different on bulk Cu (taken in the wire form) and nano-structured Cu on pencil graphite. Whereas in the former the disulphide bond of Cys-Cys remained intact, it got cleaved when Cys-Cys was adsorbed on electrodeposited copper indicating the activated nature of the nano-structure compared to bulk copper. C S stretching mode of vibration underwent blue shift in Cys-Cys adsorbed on Cu on pencil graphite vis-à-vis Cys-Cys adsorbed on Cu wire. Further evidence on the cleavage of the C S bond on an activated substrate was obtained by considering a bimetallic substrate comprising of silver on copper which was electrodeposited on pencil graphite. Our studies have demonstrated that nano‑copper surface is an excellent substrate for SERS giving 200 μM as lower detection limit for Cys-Cys. [ABSTRACT FROM AUTHOR]

The Art Institute of Chicago holds an extensive collection of works on paper by Paul Gauguin, including 39 unique woodblock prints from the artist's famed Noa Noa Suite that he produced following his first visit to Tahiti. Although Gauguin's graphic works are among his most innovative and experimental, they have been less studied from a technical perspective than his works in other media. This paper presents results from an in-depth, multi-analytical investigation of the Noa Noa prints that employed non-invasive techniques hand-in-hand with selective analysis of microsamples of the printing inks and pigments to provide a detailed characterization of Gauguin's materials and insights into his working methods. The study reveals Gauguin's creativity in the manipulation of his materials to produce distinctive visual effects in his woodblock prints: this included the formulation of oleoresinous media to produce textural effects, and the selective use of hand- and stencil-applied colors for various impressions. The analytical findings also confirm visual evidence of fading and other alterations in pigments that help to inform our interpretation of the imagery. Overall, this research has aided understanding of Gauguin's pictorial narratives and enhanced our appreciation of the artistic significance and technical ingenuity involved in the production of this understudied part of his oeuvre. [ABSTRACT FROM AUTHOR]

In this study, a sandwich immunoassay method utilizing enzymatic activity of alkaline phosphatase (ALP) on 5-bromo-4-chloro-3-indolyl phosphate (BCIP) for Escherichia coli ( E . coli ) detection was developed using surface enhanced Raman spectroscopy (SERS). For this purpose, spherical magnetic gold coated core-shell nanoparticles (MNPs-Au) and rod shape gold nanoparticles (Au-NRs) were synthesized and modified for immunomagnetic separation (IMS) of E . coli from the solution. In order to specify the developed method to ALP activity, Au-NRs were labeled with this enzyme. After successful construction of the immunoassay, BCIP substrate was added to produce the SERS-active product; 5-bromo-4-chloro-3-indole (BCI). A good linearity (R 2 = 0.992) was established between the specific SERS intensity of BCI at 600 cm − 1 and logarithmic E . coli concentration in the range of 1.7 × 10 1 –1.7 × 10 6 cfu mL − 1 . LOD and LOQ values were also calculated and found to be 10 cfu mL − 1 and 30 cfu mL − 1 , respectively. [ABSTRACT FROM AUTHOR]

Furfural concentration is an important indicator for the aging diagnosis of internal paper insulation in power transformers. Surface-enhanced Raman scattering (SERS) could directly perform rapid in-situ detection without complex preprocessing steps, which makes SERS suitable for online monitoring. The application of SERS in the detection of furfural concentration in transformer oil was investigated. First, sliver nano-bulks (AgNBs) were synthesized successfully on the copper foil surface by the galvanic displacement. The electric field distributions of AgNBs were analyzed theoretically using the COMSOL software, which indicated that the AgNBs were suitable for SERS application. Then, AgNBs were used as the SERS substrate to detect standard transformer oil samples with different furfural concentrations. As a result, the Raman spectral peak at 1571 cm?1 was selected as the characteristic SERS spectral peak of furfural dissolved in transformer oil for qualitative and quantitative analyses. Subsequently, the Raman spectral peak ratio I1571/I1597 was used as the furfural function in oil to construct the quantitative analysis model using the least squares method. Results showed that SERS method could be used to analyze the furfural dissolved in transformer oil quantitatively and effectively. With further improvements of the detection limit, the SERS method will provide a useful approach to achieving rapid in-situ analysis for furfural dissolved in transformer oil. [ABSTRACT FROM PUBLISHER]

Although glancing angle deposited silver substrates offer an excellent figures for surface enhanced Raman scattering (SERS) sensing, the chemical instability issues of silver substrates upon exposure to the aqueous solutions is still challenging and limits their application in SERS-based biosensors. In this context, we applied and compared two different strategies including sodium citrate as a self-assembled monolayer (SAM), and thermal deposition of gold at different thicknesses to stabilize the silver chevron arrays deposited by the glancing angle deposition method. Although optical characterization confirms good stabilization in both strategies, intact morphological features can only be detected after gold coating compared to sodium citrate coating which makes a homogenous monolayer on the surface. Furthermore, the SERS intensity of Rhodamine B increases after these coating processes, which might be due to the less oxidation and deformation of the nanostructures on the substrate or improved attachment of the analyte to the substrates. This research can extend our knowledge for the development of stable and reproducible SERS substrates in the field of biological sensing. [ABSTRACT FROM AUTHOR]

Coupling microchip capillary electrophoresis to surface enhanced Raman spectroscopy (MCE-SERS) combines the high separation power of capillary electrophoresis with the capability to obtain vibrational fingerprint spectra for compound identification. Raman spectroscopy is a structurally descriptive and label-free detection method which is particularly suited for chemical analysis because it is non-destructive and allows the identification of analytes. However, it suffers from poor sensitivity and sometimes even requires acquisition times far longer than the typical peak width of electrophoretic separations. The Raman intensity can be drastically improved if the analyte is brought into close proximity to nanostructured metal surfaces or colloids due to the surface enhancement effect. This paper presents a novel approach in the field of MCE-SERS on-line coupling. The key element of the developed glass microfluidic device is a dosing structure which consists of two side channels joining the MCE channel symmetrically after the electrophoretic separation of the analytes. The dosing channel supplies silver nanoparticles (Ag-NPs), to the separated electrophoretic zones which facilitates an on-the-fly recording of SERS-spectra of the separated compounds. The functionality of the MCE-SERS chip was evaluated by the analysis of a rhodamine model mixture within 90 s achieving RSD of migration times below 1.5%. The approach was successfully applied for the analysis of the food additive riboflavin in a barbecue sauce. [ABSTRACT FROM AUTHOR]

Abstract: Plasmon‐driven catalysis has attracted great attention in recent years, but the reaction efficiency remains to be improved. Photothermal Fe5C2@Au core–shell nanostructures are fabricated through a self‐assembly process of Fe5C2 and Au nanoparticles (NPs) with the assistance of hexanethiol, which can be highly efficient surface enhanced Raman spectroscopy (SERS) platforms for the study of plasmon‐driven dimerization of 4‐aminothiophenol (4‐ATP) and 4‐nitrothiophenol (4‐NTP). As compared to bare Au NPs, much accelerated reaction kinetics can be achieved on the Fe5C2@Au core–shell nanostructures by quantitatively determining the Raman intensity of the ν(N=N) band in the generated 4,4′‐dimercaptobenzene (DMAB). The photothermal effect from the Fe5C2 NPs may lower the energy barrier and generate more hot electrons for the plasmon‐driven catalysis. This photothermal route may open up new avenues for enhancing the reaction rate and broadening the research area of the plasmon‐driven catalysis. [ABSTRACT FROM AUTHOR]

Abstract: Accurate determination of the gutter oil represents a major food safety challenge. Here, we propose to use the surface enhanced Raman spectroscopy (SERS) with silver nanorod array substrates to detect the capsaicin, a marker of the gutter oil that is difficult to remove. The capsaicin has several characteristic SERS peaks at Δv = 807 cm−1, Δv = 1, 264 cm−1, and so forth, which correspond to the C39‐C37‐C43 stretching vibrational mode at the alkyl chain, the ring stretching vibrational mode, and so forth, confirmed by our density functional theory calculation. This SERS‐based method enabled the rapid and highly sensitive detection of the gutter oil with minimum pretreatment. The concentration dependent SERS investigation shows that the SERS intensity of these characteristic peaks has a linear relationship with the capsaicin concentration when 1 mg/L < C < 60 mg/L. By combining a liquid phase extraction method and the SERS detection strategy, the capsaicin concentration as low as 30 mg/L can be detected from inoculated corn oil samples. [ABSTRACT FROM AUTHOR]

Abstract: We have designed a new surface‐enhanced Raman scattering (SERS) sensor composed of β‐cyclodextrin (β‐CD) containing poly(glycidyl methacrylate) (PGMA) brush coated silicon substrate and per‐6‐deoxy‐(6‐thio)‐β‐cyclodextrin (β‐CD‐SH) modified gold nanoparticles for detection of polyaromatic hydrocarbons (PAHs; pyrene and anthracene). The β‐CD containing PGMA brushes were synthesized by the interface‐mediated Reversible addition‐fragmentation chain transfer (RAFT) polymerization of glycidyl methacrylate and followed an epoxide ring‐opening reaction to attach β‐CD molecules. Some PAHs, such as pyrene and anthracene, can be introduced into the hydrophobic space of β‐CD, which allows them to detect the SERS of PAHs. After separating pyrene or anthracene from the solution by the β‐CD containing PGMA brush coated silicon substrate, they were sandwiched with the SERS substrate consisting of per‐6‐deoxy‐(6‐thio)‐β‐cyclodextrin and rhodamine 6G (Raman reporter) on gold nanoparticles. The correlation between PAH concentrations and SERS signal was found to be linear in the range of 2.5 to 10 nM for anthracene and 10 and 25 nM for anthracene. The limit of detection values for pyrene and anthracene are 0.8 and 2.4 nM, respectively. Furthermore, the SERS sensor was also evaluated for the investigation of pyrene or anthracene specificity on different organic molecules and polyaromatic hydrocarbons. [ABSTRACT FROM AUTHOR]

The aim of this study was to obtain in vivo and ex vivo reproducible surface enhanced Raman signal from mouse skin and to use it for the differentiation of skin pathologies. We induced skin carcinoma in mice models using a chemical treatment and tested the chemopreventive activity of a new formulation based on natural compound betulin extracted from the bark of birch trees. Using surface enhanced Raman spectroscopy (SERS) we identified in vivo and ex vivo the spectral signatures characteristic to the healthy skin, melanoma skin induced in mouse models, and to the pathology evolution when the betulin nanoemulsion formulation was topically applied on the cancerous skin of mice. SERS markers associated to each pathology were identified and the signal was distinguished from the classical Raman signal of skin based on several biomarkers, such as the disappearance of the amide I band of proteins, the amplification of the 1574 cm −1 band assigned to nucleic acid bases, and the appearance of the highly amplified band at 230 cm −1 characteristic to the metal-biomolecules complex. The various skin pathologies were differentiated using principal components analysis and K-means clustering. The effectiveness of the betulin nanoemulsion treatment was validated by the histological examination and the chemometrics methods, which successfully confirmed the direct SERS differentiation between the cancerous and the betulin nanoemulsion treated skin. [ABSTRACT FROM AUTHOR]

The integration of sample pretreatment remains one of the hurdles towards a rapid, automated micro total analytical system (µ-TAS) for real samples. In this paper, a modular design, which was used for sample preparation, has been developed as the polydimethylsiloxane (PDMS) millifluidic chips with channels at a millimeter level. Multiple functional units, including extraction, filtration, mixing and solid phase extraction (SPE), for sample pretreatment were integrated in one chip. In this chip, each functional unit was connected by pump tubings and one-way valves in series to form a fully automated system. Based on the modular design, multiple functional units have been combined in different sequences according to practical needs. In addition, the proposed system has characteristics of miniaturization, portability, and real-time application. Herein, spiked benzoyl peroxide (BPO) in flour samples was used as a model compound to study the system's performances. With a portable integrated Raman spectrometer for detection, the detection limit of BPO was 0.017 g kg −1 , with a linear relationship from 0.025 to 0.5 g kg −1 . This modular design was demonstrated to be effective and it can be expanded for pretreatment of other food samples. [ABSTRACT FROM AUTHOR]