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Surface-enhanced Raman spectroscopy (SERS) has gained increasing attention for sensing chemicals and molecules at low concentrations. Localized surface plasmons (LSPs) that occur on metal nanostructures can be used to enhance small Raman signals while maintaining the non-destructivity of Raman spectroscopy. SERS can be used to detect consumer chemical products that effect on the human body through the ecosystem. In addition, there is increasing demand for its use in personal disease-monitoring systems. SERS materials can be made in various forms using metal nanoparticles (NPs) that can produce LSPs. Recently, nanotechnology has been used to fabricate SERS materials with high selectivity for target materials by finely controlling the structure. Since the structure affects the enhancement of Raman signals, research into various nanostructures is important for next-generation SERS sensors. Herein, we first discuss various fabrication of SERS dispersions and substrates using plasmonic metal NPs. Afterward, we summarize the enhancement factor (EF) and limit of detection (LOD) values of SERS materials prepared via various fabrication methods. [ABSTRACT FROM AUTHOR]

A composite comprising a silver nanoparticles‐loaded poly(amidoamine) (PAMAM) dendrimer crosslinked with glutaraldehyde (PAMAM/AgNPs) is synthesized using a one‐step method under vortex at room temperature. The structure of glutaraldehyde‐crosslinked PAMAM dendrimer is characterized using FTIR and high‐resolution magic angle spinning–carbon 13 nuclear magnetic resonance (HRMAS 13C NMR) spectroscopy. The crosslinking structure ensures the uniformity and stability of the Ag nanoparticles, and the flexibility of the PAMAM/AgNPs composite. X‐ray diffraction (XRD) analysis and energy dispersive spectroscopy (EDS) confirm the formation of Ag nanoparticles in the PAMAM/AgNPs composite. Scanning electron microscopy (SEM) and three‐dimensional (3D) micro‐Raman images reveal the coarsely porous 3D micro‐structure of the PAMAM/AgNPs composite. This unique micro‐3D architecture provides the PAMAM/AgNPs composite with spongy flexibility and a swab‐like nature, which is advantageous for the rapid and effective absorption of liquid samples on the surfaces of objects. Surface enhanced Raman spectroscopy (SERS) indicates that the detection limits of both rhodamine 6G (R6G) and thiram are 1.0 × 10−5 mol L−1, and the SERS enhancement factor of R6G is determined to be 1.35 × 104. The spongy flexible PAMAM/AgNPs SERS substrate therefore has potential for use in Raman active compound detection. [ABSTRACT FROM AUTHOR]

Plant pathogens, including viruses, bacteria, and fungi, cause massive crop losses around the world. Abiotic stresses, such as drought, salinity and nutritional deficiencies are even more detrimental. Timely diagnostics of plant diseases and abiotic stresses can be used to provide site- and doze-specific treatment of plants. In addition to the direct economic impact, this "smart agriculture" can help minimizing the effect of farming on the environment. Mounting evidence demonstrates that vibrational spectroscopy, which includes Raman (RS) and infrared spectroscopies (IR), can be used to detect and identify biotic and abiotic stresses in plants. These findings indicate that RS and IR can be used for in-field surveillance of the plant health. Surface-enhanced RS (SERS) has also been used for direct detection of plant stressors, offering advantages over traditional spectroscopies. Finally, all three of these technologies have applications in phenotyping and studying composition of crops. Such noninvasive, non-destructive, and chemical-free diagnostics is set to revolutionize crop agriculture globally. This review critically discusses the most recent findings of RS-based sensing of biotic and abiotic stresses, as well as the use of RS for nutritional analysis of foods. [ABSTRACT FROM AUTHOR]

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While extensive research has focused on understanding the degradation mechanisms of Poly(vinyl acetate) (PVAC) paint under different environmental conditions, limited attention has been paid to the long-term stability of PVAC-based white glues, especially when used in artworks. This study investigates the accelerated degradation, under simulated photoaging, and isothermal treatment of a commercial PVAC-based white glue considered representative of this class of materials used in contemporary artworks to predict its durability and assess its behavior in art objects. Through accelerated aging experiments and comparison with natural aging observed in artworks, the study reveals the formation of chromophores and the release of plasticizers as key processes; in particular, the progressive darkening was considered an early indicator of degradation processes, before structural changes could be detected by FTIR or NMR spectroscopies. The plasticizer loss induces an increase in glass transition temperature, from 7 °C to temperatures higher than room temperature, affecting the adhesive's cohesive strength and contributing to the detachment of materials in artworks. The findings underscore the importance of preventive conservation measures to mitigate degradation issues in PVAC-based artworks. [ABSTRACT FROM AUTHOR]

Recent progress of surface-enhanced Raman spectroscopy (SERS) in malignant tumors is reviewed. Firstly, the development status of SERS detection technology was briefly introduced, and the advantages of SERS detection technology were put forward. Secondly, the development status of SERS technology in multi-system malignant tumor species was reviewed. Finally, the application of SERS in the diagnosis of multi-system malignant tumors was summarized and analyzed, and the prospect was put forward. [ABSTRACT FROM AUTHOR]

Surface enhanced resonance Raman (SERS) is a powerful optical technique, which can help enhance the sensitivity of Raman spectroscopy aided by noble metal nanoparticles (NPs). However, current SERS‐NPs are often suboptimal, which can aggregate under physiological conditions with much reduced SERS enhancement. Herein, a robust one‐pot method has been developed to synthesize SERS‐NPs with more uniform core diameters of 50 nm, which is applicable to both non‐resonant and resonant Raman dyes. The resulting SERS‐NPs are colloidally stable and bright, enabling NP detection with low‐femtomolar sensitivity. An algorithm has been established, which can accurately unmix multiple types of SERS‐NPs enabling potential multiplex detection. Furthermore, a new liposome‐based approach has been developed to install a targeting carbohydrate ligand, i.e., hyaluronan, onto the SERS‐NPs bestowing significantly enhanced binding affinity to its biological receptor CD44 overexpressed on tumor cell surface. The liposomal hyaluronan (HA)‐SERS‐NPs enabled visualization of spontaneously developed breast cancer in mice in real time guiding complete surgical removal of the tumor, highlighting the translational potential of these new glyco‐SERS‐NPs. [ABSTRACT FROM AUTHOR]

Acetone is a reliable index to evaluate the aging state of oil paper insulation. It is of great significance to study a fast, highly sensitive and accurate method of detecting acetone in oil to ensure the safe and stable operation of oil-immersed transformers. In this paper, a method based on surface enhanced Raman spectroscopy for the detection of acetone in oil is investigated. Based on the mechanism of surface-enhanced Raman spectroscopy (SERS), a simulation model of surface-enhanced substrate was constructed using COMSOL software, and it was determined that the enhancement effect was better when silver nanowires/zinc oxide nanorods (Ag/ZnO) composite structure was selected. Ag/ZnO substrates were prepared by solvothermal method and experimentally tuned and characterized to obtain SERS substrates with high enhancement properties. The substrate coupled partial least square (PLS) model was used to establish a method for the detection of acetone in insulating oils, and its limit of quantification for acetone was 0.003 mg/g, which meets the requirements for engineering testing. [ABSTRACT FROM AUTHOR]

A robust and competitive technology to synthesize arranged high‐density gold nanoparticles on highly uniform Al nanoconcavities substrates is presented. The nanoparticles are formed through sputtering and thermal annealing treatment on Al templates, which are synthesized through particular removal of nanoporous anodic alumina structure with controlled anodization conditions and with phosphoric acid as electrolyte. This scalable fabrication mechanism regulates the particle size, arrangement, shape and interparticle separation across large surface areas, which empowers the optimization of their surface enhanced Raman scattering (SERS) activities. 4‐mercaptopyridine is selected as a probe molecule. Analysis reveals that Au‐decorated Al nanoconcavities substrates are highly competitive for the enhancement of Raman signals and could be employed as self‐sustaining nanosensors. By using these templates, a concentration as low as 10−7 M of 4‐mercaptopyridine is easily detected. Finally, the calculated EF factor of 1.1 × 107 confirms the suitability for effective and sensitive SERS detection of the developed substrates. [ABSTRACT FROM AUTHOR]

Mycotoxin contamination on food and feed can have deleterious effect on human and animal health. Agricultural crops may contain one or more mycotoxin compounds; therefore, a good multiplex detection method is desirable to ensure food safety. In this study, we developed a rapid method using label-free surface-enhanced Raman spectroscopy (SERS) to simultaneously detect three common types of mycotoxins found on corn, namely aflatoxin B1 (AFB1), zearalenone (ZEN), and ochratoxin A (OTA). The intrinsic chemical fingerprint from each mycotoxin was characterized by their unique Raman spectra, enabling clear discrimination between them. The limit of detection (LOD) of AFB1, ZEN, and OTA on corn were 10 ppb (32 nM), 20 ppb (64 nM), and 100 ppb (248 nM), respectively. Multivariate statistical analysis was used to predict concentrations of AFB1, ZEN, and OTA up to 1.5 ppm (4.8 µM) based on the SERS spectra of known concentrations, resulting in a correlation coefficient of 0.74, 0.89, and 0.72, respectively. The sampling time was less than 30 min per sample. The application of label-free SERS and multivariate analysis is a promising method for rapid and simultaneous detection of mycotoxins in corn and may be extended to other types of mycotoxins and crops. [ABSTRACT FROM AUTHOR]

The SERS intensity of analytes is primarily influenced by the density and distribution of hotspots, which are often difficult to manipulate or regulate. In this study, cucurbit[8]uril (CB[8]), a kind of rigid macrocyclic molecule, was introduced to achieve ~ 1-nm nanogap between gold nanoparticles to increase the density of SERS hotspots. Three kinds of estrogens (estrone (E1), bisphenol A (BPA), and hexestrol (DES)) which are molecules with weak SERS signals were targeted in the hotspots by CB[8] to further improve the sensitivity and selectivity of SERS. It was demonstrated that CB[8] can link gold nanoparticles together through carbonyl groups. In addition, the host–guest interaction of CB[8] and estrogens was proved from the nuclear magnetic resonance hydrogen and infrared spectra. In the presence of CB[8], the SERS intensities of E1, BPA, and DES were increased to 19-fold, 74-fold, and 4-fold, respectively, and the LOD is 3.75 µM, 1.19 µM, and 8.26 µM, respectively. Furthermore, the proposed SERS method was applied to actual milk sample analysis with recoveries of E1 (85.0 ~ 112.8%), BPA (83.0 ~ 103.7%), and DES (62.6 ~ 132.0%). It is expected that the proposed signal enlarging strategy can be applied to other analytes after further development. [ABSTRACT FROM AUTHOR]

Polycyclic aromatic hydrocarbons (PAHs) as a kind of persistent organic pollutants have high teratogenic, carcinogenic, mutagenic properties, as well as high octanol/water partition coefficient and sediment/water partition coefficient, causing serious threat to human health and water environment. In this study, the feasibility of Surface-enhanced Raman spectroscopy (SERS) technology combined with chemometrics for quantitative analysis and carcinogenic risk estimation of PAHs in water with complex matrix was explored. Firstly, 36 water samples from lake, tap, and distilled water were prepared, and then nano-silver particles (Ag NPs) were mixed with samples. The integrated strategy of spectral preprocessing was adopted to remove spectral interference, and variable selection algorithm was used to extract the information effectively, thus improving the prediction performance of the random forest (RF) calibration model for PAHs quantitative analysis and carcinogenic risk. The final results indicated that RF combined with spectral preprocessing integration strategy and variable selection had better predictive performance compared with the Raw-RF model. For phenanthrene (Phe) and benzo[ a ]anthracene (BaA) analysis, the optimal calibration model was WT-SG-SiPLS-VIM-RF (Phe: mean relative error of prediction (MRE p) = 0.0646, coefficient of determination of prediction (R2 p) = 0.9658; BaA: MRE p = 0.0949, R2 p = 0.9537). SG-WT-SiPLS-VIM-RF model (MRE p = 0.0992, R2 p = 0.9551) showed a better predictive performance for fluoranthene (Flu). WT-SG-VIM-RF model (MRE p = 0.0902, R2 p = 0.9409) showed excellent performance for assessing the carcinogenic risk of PAHs. Therefore, the combination of SERS technology and chemometrics provides a new approach for analyzing PAHs. • The carcinogenic risk assessment of PAHs in water using SERS combined with chemometrics was discussed for the first time. • The optimal RF-based spectral preprocessing strategy was obtained from the spectral characteristics of different components. • The SiPLS-VIM-RF calibration model showed a better predictive performance for the quantitative analysis of PAHs in water. [ABSTRACT FROM AUTHOR]

Simultaneous assessment of agrochemical residues in agricultural entities is crucial for ensuring food safety and protecting consumer health. A highly sensitive and stable thioglycolic acid (TGA) based surface modified coreshell nanorod (Au@Ag@TGANR) arrays were developed for simultaneous fungicide detection in peach samples. The developed Au@Ag@TGANRs exhibited superior surface enhance Raman scattering (SERS) performance, enabling the simultaneous examination of ziram (ZIR) and thiabendazole (TBZ) residues in peach samples with detection limits as low as 0.003 and 0.028 ppm and high R2 values of 0.996 and 0.995, for ZIR and TBZ, respectively. Good recoveries of 86.2 to 108.6 % and 80.2 to 105.7 % were also achieved for peach samples, highlighting the effectiveness of the established protocol for accurate and reliable detection of pesticides in fruits. These results suggest that the proposed method could be a valuable addition to current food safety protocols, with potential application in investigating toxic residues in agricultural entities. • Developed a thiol-based surface modified SERS sensor for rapid fungicides detection • Enhanced Au@AgNRs stability and sensitivity with thioglycolic acid • Thiol modification significantly improved SERS performance and substrate stability • Highly dense hotspot arrays provided excellent SERS detection efficiency • Effectively detected ZIR and TBZ residues simultaneously in peach fruit samples [ABSTRACT FROM AUTHOR]

As the extensive use of antibiotics has led to the rapid spread of antibiotic resistance, there is an urgent need for quantitative assessment of antibiotic residues in the environment. Surface-enhanced Raman spectroscopy (SERS) has emerged as a rapid and cost-effective detection method, but it suffers from the high variability in signal intensities, its quantitative detection remains challenging. Herein, we have developed a SERS calibration substrate with a silent region internal standard, enabling simultaneous and reliable quantitative detection of three commonly antibiotics of penicillin potassium (PP), tetracycline hydrochloride (TCH) and levofloxacin (LEV). The calibration substrate is made by assembling Au @ 4-mercaptobenzonitrile (4-MBN) @ SiO 2 on silicon wafer. The chemically-inert silica shell allows the substrate to remain SERS active for more than 24 weeks in the air. The v C ≡ N of 4-MBN in the silent region of 1800–2800 cm−1 provides an effective reference for correcting Raman signal fluctuations. The relative SERS intensity by normalizing to the internal standard (IS) of v C ≡ N shows a linear response against to the logarithmic concentration with a correlation coefficient of 0.997, 0.976, 0.998 and a limit of detection (LOD) of 26.9, 28.2, 2.4 nM for PP, TCH and LEV, respectively. Furthermore, simultaneous detection and principal component analysis (PCA) of these antibiotics in lake water with a concentration range of 1–100 mg/L can achieve a sensitivity and specificity of 100 %. This novel quantitative technique of using this SERS calibration substrate shows promises as a high-throughput platform for multiple trace antibiotics analysis. [Display omitted] • A stable SERS calibration substrate with a silent region internal standard has been developed. • The substrate can provide a stable of internal standard for more than 24 weeks. • A simple and reliable quantitative detection is achieved for three commonly antibiotics. • Simultaneous detection and principal component analysis show a specificity of 100 %. [ABSTRACT FROM AUTHOR]

Polyelectrolytes (PEs) serve as the critical medium for electrochemical reactions in membrane-based electrochemical devices, such as fuel cells and membrane electrolyzers. To optimize membrane-based electrochemical device performance and elucidate reaction mechanisms, there is a pressing need for detailed microscopic molecular information at gas diffusion electrode/PE interfaces. In this work, we designed a novel membrane-based-electrochemical-device-like gas diffusion electrode/polyelectrolyte electrochemical in-situ Raman cell. The cell's configuration and gas transfer characteristics closely mimic those of membrane-based electrochemical devices under working conditions. We created a Pt/Nafion(s) interface by hot-pressing satellite Au@SiO 2 -Pt loaded carbon cloth with a Nafion membrane, and used this interface for electrochemical in-situ surface enhanced Raman spectroscopy (SERS) observation, including oxygen adsorption/desorption processes, structure of interfacial water and functional groups of Nafion under Ar. The cell enables negatively polarize the potential down to -1.6 V vs. RHE without stripping of the solid/solid interface, despite vigorous H 2 generation. The stability of the interface under extreme conditions demonstrates rapid gas transfer at the interface. This observation underscores the potential of our in-situ Raman cell for studying various gas-involved reactions under conditions that closely resemble those in operational membrane-based electrochemical devices. [ABSTRACT FROM AUTHOR]

The residue of pesticide fenthion is a common issue in food safety, and how to conveniently detect it is a challenge in the food industry. Therefore, combined with a portable Raman spectrometer, a surface enhanced Raman spectroscopy (SERS) method based on a high-performance substrate Au@AgNPs had been designed for the rapid and sensitive detection of fenthion. Au@AgNPs can be induced to generate more hot spots to improve SERS signals because of their core-shell structure. The quantitative detection of fenthion was achieved under the optimal conditions: pH 7.0, 10−3 M CaCl 2 , 70 % Au@AgNPs concentration, and 4 min of incubation time. The results showed that the method had a wider detection range of 0.1–100 mg/L, a low detection limit (LOD) of 0.036 mg/L, excellent anti-interference ability, and reproducibility. In addition, the method was successfully validated with the actual sample rice. Therefore, the method had the advantages of being fast, on-site, and easy to use, which is useful for promoting its application. [Display omitted] • Fast and on-site detection of fenthion with a portable Raman spectrometer. • Construction of SERS substrate "bimetallic Au@Ag core-shell nanoparticles". • The fenthion detection system were optimized, obtaining a high performance. • The fenthion detection method has a high sensitivity and wide detection range. • The method was successfully validated with the real sample rice. [ABSTRACT FROM AUTHOR]

17β-E 2 is used in animal growth regulation and agricultural fertilizer, and even ng L−1 mass concentration levels can show biological effects. In this work, Ag NPs was used as surface-enhanced Raman spectroscopy (SERS) source and WS 2 was synthesized by a simple method to provide a uniform distribution platform for Ag NPs. The MIP was the shell, which can selectively enrich the target molecule, pull the distance between the target molecule and SERS source, and protect Ag NPs. A cyclable SERS substrate with high sensitivity for detecting 17β-E 2 in food was constructed. The optimized WS 2 /Ag@MIP as SERS substrate has the advantages of high Enhanced Factor (EF = 2.78 × 109), low detection limit (LOD = 0. 0958 pM), strong anti-interference ability, and good recycling performance. Moreover, the detection of 17β-E 2 in real samples still has good accuracy. This work provides a new possibility for the trace detection of 17β-E 2 in food. • Sandwich WS 2 /Ag@MIP composite material was prepared for the first time and used as SERS base to achieve sensitive detection of 17β-E 2. • Ag NPs was used as SERS source and WS 2 provided a platform for uniform distribution of Ag NPs. The outermost layer was coated with MIP layer, which realized selective adsorption of 17β-E 2 , shortened the distance between 17β-E 2 and Ag NPs and protected the deterioration of Ag NPs. • WS 2 /Ag@MIP as SERS substrate realized sensitivity detect of 17β-E 2 , EF value was 2.78 × 109, the LOD value was 9.58 × 10−13 M. By elution of target molecules in MIP, the SERS substrate can be recycled. • WS 2 /Ag@MIP as SERS substrate realized the detection of 17β-E 2 in real samples. In the actual spiked sample detection, the recovery of 17β-E 2 in milk samples were 97.38% - 105.46%, and RSDs were 3.96% - 5.04%. [ABSTRACT FROM AUTHOR]

[Display omitted] • A novel aptamer-based SERS sandwich method for detecting E. coli was developed. • The fabrication of SH-apt@Au-Ag@Si TP was simple and rapid, which needed 20.5 h. • The detection process of E. coli took approximate 3 h by using SH-apt@Au-Ag@Si TP. • The SERS sandwich method could detect E. coli with the LOD of 2.8 CFU/mL. • The method was successfully used to detect E. coli in spiked Xinhuang tablet sample. Escherichia coli contamination in food and pharmaceutical preparations needs to be strictly controlled according to the regulations in many countries. However, rapid and sensitive E. coli detection is still a challenge. In this study, an aptamer-based surface-enhanced Raman spectroscopy (SERS) sandwich method was developed for the rapid and sensitive detection of E. coli using an aptamer-functionalized Au-Ag@Si triangular pyramid (TP) substrate. The Au-Ag@Si TP substrate was functionalized with E. coli aptamer to work as both the capture probe and SERS tag by integrating with Raman reporter (6-carboxy-X-rhodamine). The fabrication of the capture probe, SH-apt@Au-Ag@Si TP, was simple and rapid (20.5 h). This method could selectively and rapidly detect E. coli with a limit of detection of 2.8 CFU/mL within approximately 3 h. It was successfully applied to a traditional Chinese medicine preparation, Xinhuang tablets, with recoveries ranging from 90.19 % to 104.17 %. The results indicated that the developed method was simple and rapid, and it could be a promising alternative for the on-site detection of E. coli in pharmaceutical and food samples. [ABSTRACT FROM AUTHOR]

[Display omitted] • CPS is insufficient to classify cancer patients' responsiveness to immunotherapy. • Au-shelled/Ag-core/Si nanocone arrays enhance SERS sensitivity and reliability. • SERS accurately evaluates the sensitivity of HNSCC patients to NAIT via serum. • SERS can monitor NAIT's efficacy faster and more conveniently than imaging. Head and neck squamous cell carcinoma poses a formidable treatment challenge owing to its complex anatomy and essential functions of the organs involved. Neoadjuvant immunotherapies, particularly PD-1 inhibitors, have shown promise in improving patient outcomes. Nevertheless, the ability to accurately predict which patients will benefit from neoadjuvant immunotherapy continues to be a significant hurdle. We investigated 46 patients diagnosed with head and neck squamous cell carcinoma. Combined positive score was assessed before treatment. Serum samples were collected both before and after neoadjuvant immunotherapy, and subsequently analyzed utilizing surface-enhanced Raman spectroscopy. Significant differences in Raman spectral peaks were observed between the partial response and stable disease groups before treatment, particularly in the regions of 516–525 cm−1, 1240–1400 cm−1, 1600–1636 cm−1, and 1647–1680 cm−1. These peaks represent different cancer-related biochemical components, including protein and nucleic acid vibrations, disulfide bonds, amide III bands, CH2/CH3 deformations, and amide I bands. Principal Component Analysis-Linear Discriminant Analysis and Receiver Operating Characteristic analysis demonstrated that surface-enhanced Raman spectroscopy exhibited remarkable sensitivity and specificity, surpassing the combined positive score in assessing patient responses to neoadjuvant immunotherapy. Surface-enhanced Raman spectroscopy offers significant potential to surpass the conventional combined positive score in predicting responses to neoadjuvant immunotherapy. [ABSTRACT FROM AUTHOR]

[Display omitted] • Trace tryptophan was determined by SERS method combined with diazo-coupling reactions and silver dendritic substrate. • The SERS method exhibited excellent SERS activity to tryptophan. • Two different derivatization reagents were used for diazo-coupling reactions to detect tryptophan. • The SERS detection of tryptophan in calf serum was successfully realized with LOD of 10−11 mol/L. In this study, a simple, rapid and sensitive tryptophan (Trp) detection method was proposed, which combined surface enhanced Raman spectroscopy (SERS) with diazo coupling reaction and silver dendritic substrate. Two derivatization reagents, 4-mercaptoaniline (PATP) and 2-fluoro-4-mercaptoaniline (2-F-PATP) were used for derivatization reaction with Trp, which can be controlled by experimental parameters such as derivatization reagent concentration and sodium nitrite concentration. The partial least squares quantitative (PLS) detection model is applied in determining the concentration of Trp. The determination coefficient (R2) of PLS model was 0.9617 based on PATP and 0.9950 on 2-F-PATP. The LOD of the two derivatization methods were as low as 10−11 mol/L. This combined technique has the characteristics of simple operation, high sensitivity and good selectivity, and shows great potential in the detection of Trp in biological media. [ABSTRACT FROM AUTHOR]

[Display omitted] • SERS aptasensor has benefits of low cost and strong specificity which can play as potential tool for diagnosis of cancer. Incipient screening for cervical cancer is crucial for treatment and improving prognosis. In this work, SERS based aptamer sensor (aptasensor) has been developed and applied to high-sensitivity detection of cervical cancer tumor marker (Carbohydrate antigen19-9 (CA19-9)) with a microporous chip, which was used as surface enhanced Raman scattering (SERS) analysis platform. The aptamer of CA19-9 was immobilized on the gold nanodumbbell as a capture probe and the gold nanobipyramid containing complementary aptamer chains of the signal molecule Cy5 was modified as a signal probe. SERS aptasensor was constructed by combining signal probes and capture probes. It caused signal molecule Cy5 were sandwiched between the signal probes and capture probes; the constructed SERS aptasensor generated a strong SERS signal of Cy5. Based on the strong specificity of the aptamer, the CA19-9 aptamer binds specifically to CA19-9 when CA19-9 exist in the detection environment. The signal probe was released, resulting in a decrease in the SERS signal of the detection environment. Under the optimal detection conditions, the detection limit of the aptasensor was calculated to be 1.16 × 10−3 U/mL and limit of quantification is equal to 3.87 × 10−3 U/mL. In addition, a standard cervical cancer bearing mouse model was constructed and the SERS spectra of the serum of mice at different stages were measured. The CA19-9 content in the serum of mice at different stages was calculated. Compared with the results of enzyme-linked immunosorbent assay (ELISA), relative error (RE) values (2.54 %, −6.093 %, −4.922 %, and 3.04 %) of the CA19-9 concentrations detected by the two methods on the day of 0, 7, 14 and 28. The proposed SERS aptasensor provides a new and reliable platform for early cervical cancer screening, and its low RE value proves that it will be a promising CA19-9 detection method. [ABSTRACT FROM AUTHOR]

Fenton technology is one of advanced oxidation process (AOP) methods to treat wastewater through chemical oxidation. Due to the limitations of classical iron-based catalysts, it is still challenging to find suitable catalysts for Fenton-like reactions. Here, MoS2/Au heterojunctions were successfully synthesized by reduction of chloroauric acid in the solution of layered MoS2 prepared by hydrothermal method. As a model molecule, methylene blue (MB) was used as the species to be degraded to evaluate the performance of the catalyst. It was determined by UV–visible spectra that the optimal catalyst can be obtained when MoS2 (mg): HAuCl4 (wt. % mL) is 2:2. The Fenton-like reaction process was monitored by introducing highly sensitive surface enhanced Raman spectroscopy (SERS). The results show that MB can be degraded by 83% in the first 10 min of the reaction, indicating that MoS2/Au has good catalytic performance. In addition, as a fingerprint spectrum, SERS was used to preliminarily analyze the molecular structure changes during the degradation process. The result showed that C-N-C bond was easier to break than the C-S-C bond. NH2 group and the fused ring were destroyed at the comparable speed at the first 30 min. In terms of application applicability, it was showed that MB degradation had exceeded 95% at all the three pH values of 1.4, 5.0, and 11.1 after the reaction was carried out for 20 min. The test and analysis of the light environment showed that the catalytic efficiency was significantly improved in the natural light of the laboratory compared to dark conditions. The possible mechanism based on ·OH and ·O2− from ESR data was proposed. In addition, it was demonstrated to be a first-order reaction from the perspective of kinetics. This study made a positive contribution to broaden of the applicable conditions and scope of Fenton-like reaction catalysts. It is expected to be used as a non-iron catalyst in practical industrial applications. From the perspective of detection method, we expect to develop SERS as a powerful tool for the in situ monitoring of Fenton-like reactions, and to further deepen our understanding of the mechanism. [ABSTRACT FROM AUTHOR]

Melanoma, a kind of fatal skin cancer, originates in melanin secreting cells of the dermis. Disease identification in the early stages assures a high survival rate for the patient. Most of the existing techniques retard the cancer detection phase. Surface-Enhanced Raman Spectroscopy (SERS) can capture fine details from the specimens that machine learning models can utilize to discriminate between healthy and diseased individuals rapidly. Our research work proposes a deep autoencoder based hybrid dimensionality reduction approach with a machine learning model on SERS spectrums of human skin fibroblast for melanoma cancer diagnostics. SERS measurements of 307 samples in total, belonging to two different classes, such as normal (157 samples) and malignant melanoma (150 samples), are used in this study. The SERS spectra measurements for both the samples lie between 100cm-1 and 4278cm-1. The variations in the intensity of Raman bands between both classes are intrinsically subtle. Neighborhood Component Analysis (NCA) technique has been exerted to transform 2090 dimensional spectral features into 2090 dimensional vectors and then the Deep Autoencoder (DAE) model is used to handle the nonlinearity in the data and produce the latent space, while Linear Discriminant Analysis (LDA) classifier have been employed for discriminating the normal and cancer cells. The k-fold cross-validation technique with a k value of 10 is implemented to assess the metrics of the model. The stated hybrid (NCA and DAE) model with 10-dimension latent space achieves an accuracy of 98%, the sensitivity of 99% and specificity of 97%, respectively. Due to the high-intensity nature of the SERS spectrum, the existing linear dimensionality reduction based discriminating model fails if the class label (Normal or Cancer) gets distributed on the low variance side. The proposed methodology captures both linear and nonlinear underlying structures present in the spectrums, resulting in better classification compared to the standard dimensionality reduction techniques. [ABSTRACT FROM AUTHOR]

Tyrosine phosphorylation is an important post‐translational modification of proteins, and its accurate analysis is of vital importance. However, due to limited abundance of tyrosine phosphorylation as well as severe interference of serine/threonine phosphorylation and other phosphate‐containing species, approaches that can directly analyse tyrosine phosphorylation on the cell membrane still remain limited. Herein, we report the rational development of molecularly imprinted and cladded Raman nanotags and their successful application in surface enhanced Raman spectroscopy (SERS) imaging of tyrosine phosphorylation on cancerous cells and tissues. The prepared molecularly imprinted and cladded SERS nanotags could specifically recognize phosphotyrosine and thereby allowed for distinguishing phosphotyrosine from other phosphate‐containing species on cancerous cells and tissues by SERS imaging. Therefore, the molecularly imprinted and cladded nanotags‐based SERS imaging can be a promising tool for tyrosine phosphorylation analysis and tyrosine phosphorylation‐related studies, showing great potential for biomedical applications. [ABSTRACT FROM AUTHOR]

A novel method of fabricating large‐area, low‐cost surface‐enhanced Raman spectroscopy (SERS) substrates is introduced which yields densely nanostructured surfaces utilizing laser‐induced periodic surface structuring (LIPSS) of crystalline silicon (Si). Two different interaction regimes yield low spatial frequency (LSFL) and high spatial frequency (HSFL) LIPSS patterns. Nanostructuring of Si surface is followed by deposition of a thin noble metal layer to complete the fabrication procedure. A 50–70 nm thick Ag layer is shown to maximize the SERS performance. The SERS effect is attributed to the electromagnetic field enhancement originating from the nanoscale surface roughness of Si that can be controlled by LSFL and HSFL nature of the structure. The SERS substrates are found to be capable of detecting a Raman analyte down to 10−11 m. SERS performance of the Ag deposited substrates at 532, 660, and 785 nm excitation wavelengths is compared. Both LSFL and HSFL Si surfaces with 70 nm thick Ag are found to exhibit the strongest SERS under 660 nm excitation exhibiting Raman enhancement factors (EFs) as high as 109. The Raman EFs are calculated both by SERS spectra experimentally, and using finite‐elements method simulation of the electric field enhancement where a good agreement is found. [ABSTRACT FROM AUTHOR]

Surface enhanced Raman spectroscopy (SERS) has evolved into a powerful analytical method in food and environmental analytical sciences due to its high sensitivity. Pesticide analysis is a major discipline therein. Using sustainable materials has become increasingly important to adhere to Green Chemistry principles. Hence, the green textiles poly-(L -lactic acid) (PLA) and the mixed fabric polyethylene terephthalate polyamide (PET/PA) were investigated for their applicability as solid supports for gold nanoparticles to yield SERS substrates. Gold nanoparticle solutions and green textile supports were prepared after preparation optimization. Particle size, dispersity, and particle distribution over the textiles were characterized by absorption spectroscopy and transmission electron imaging. The performance of the SERS substrates was tested using the three pesticides imidacloprid, paraquat, and thiram and a handheld Raman spectrometer with a laser wavelength of 785 nm. The resulting SERS spectra possessed an intra-substrate variation of 7–8% in terms of the residual standard deviation. The inter-substrate variations amounted to 15% for PET/PA and to 27% for PLA. Substrate background signals were smaller with PLA but more enhanced through PET/PA. The pesticides could be detected at 1 pg on PET/PA and at 3 ng on PLA. Hence, PET/PA woven textile soaked with gold nanoparticle solution provides green SERS substrates and might prove, in combination with fieldable Raman spectrometers, suitable for in-field analytics for pesticide identification. Graphical Abstract [ABSTRACT FROM AUTHOR]

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Surface-enhanced Raman scattering (SERS) shows great promise for early diagnosis due to its high specificity and rapid detection capabilities. However, its application is often hindered by substrate instability and insufficient interaction between the substrate and incident light. To address these challenges, a photonic-plasmonic strategy is often employed to enhance sensing performance but it is generally limited by the low efficiency of plasmonic metal and optical cavity resonances. In this study, we significantly improved resonance efficiency by optimizing the photonic crystal configuration and designing Au-semicoated polystyrene nanospheres. These modifications maximized light capture and resonance efficiency, resulting in a 790-fold enhancement of the Raman signal with a relative standard deviation of only 4.58%. This approach was further developed into microfluidic biosensors for melanoma diagnosis, achieving a 2-3 order-of-magnitude improvement over comparable SERS biosensors. We believe this technology has the potential to significantly improve the efficiency of early diagnosis and clinical medical analysis. • New Biosensing Nanospheres: Designed to absorb Au plasmons, reaching a wavelength of 700 nm that matches the Raman excitation wavelength. • Guided Experimental Design: Simulations were used to create photonic crystals with specific sizes and arrangements for optimal Bragg reflection of light around 785 nm. • Enhanced Raman Signal: Achieved a 790-fold enhancement in the Raman signal, with a relative standard deviation of only 4.58%. • Validation of Detection: Successfully validated for the specific detection of melanoma biomarkers, demonstrating potential for early melanoma diagnosis. • Broader Clinical Applications: This new approach also shows considerable potential for the clinical analysis of other major diseases. [ABSTRACT FROM AUTHOR]

Surface Enhanced Raman Spectroscopy (SERS) technique is an effective analytical technique in which fingerprint information about analytes can be obtained, can provide detection limit performance at the single molecule level, and analyzes are performed in a single step without any intermediate steps. SERS technique offers additional benefits rather than other analytical techniques including high selectivity, ultrasensitive detection, uncomplicated protocols, in situ sampling, on-set capability and cost-effectiveness. As a result of the combination of developments in materials and nanotechnology science with the SERS analysis technique, this technique strengthens its use advantage day by day. The most important factor that limited the use of this technique was the fact that the solution containing the desired analyte(s) was dropped onto the SERS substrate and the same substrate could not be reused in subsequent analyses. To solve this problem, scientists have focused on developing reusable SERS substrates in recent years. In these studies, scientists basically used three SERS substrate cleaning applications (1) washing the SERS substrate with a suitable solvent that can elute the analyte from SERS surface after analysis, (2) cleaning the SERS substrate with catalytic degradation of analytes after analysis by modifying them with catalytic active materials and (3) Applying plasma cleaning procedure to SERS substrate after analysis and (4) applying adsorption and desorption procedure prior to SERS analysis. Herein, the aim of this review article is to evaluate the reusable SERS substrates-based methods based on their level of development and their potential to recycle. This review offers a coherent discussion on a wide range of sensing schemes employed in fabricating the SERS substrates. We utilized a critical approach in which elaborative examples were selected to highlight key shortcomings of various experimental configurations. In the same vein, there is a discussion of the advantages and limitations concerning the key instrumental advances and the expansion of the recent methods developed in this area. [Display omitted] • Recent knowledges about the recyclable SERS concept in determination of inorganic/organic species were outlined. • A detailed summary of conventional and reusable SERS methods is presented. • The synthesis, important features and advantages of reusable substrates on the application of SERS detection were reviewed. • The detection mechanism of organic and inorganic trace contaminants by reusable SERS techniques were discussed. [ABSTRACT FROM AUTHOR]

Long-stranded non-coding RNAs (lncRNA) have important roles in disease as transcriptional regulators, mRNA processing regulators and protein synthesis factors. However, traditional methods for detecting lncRNA are time-consuming and labor-intensive, and the functions of lncRNA are still being explored. Here, we present a surface enhanced Raman spectroscopy (SERS) based biosensor for the detection of lncRNA associated with liver cancer (LC) as well as in situ cellular imaging. Using the dual SERS probes, quantitative detection of lncRNA (DAPK1-215) can be achieved with an ultra-low detection limit of 952 aM by the target-triggered assembly of core–satellite nanostructures. And the reliability of this assay can be further improved with the R2 value of 0.9923 by an internal standard probe that enables the signal dynamic calibration. Meanwhile, the high expression of DAPK1-215 mainly distributed in the cytoplasm was observed in LC cells compared with the normal ones using the SERS imaging method. Moreover, results of cellular function assays showed that DAPK1-215 promoted the migration and invasion of LC by significantly reducing the expression of the structural domain of death associated protein kinase. The development of this biosensor based on SERS can provide a sensitive and specific method for exploring the expression of lncRNA that would be a potential biomarker for the screening of LC. [ABSTRACT FROM AUTHOR]

[Display omitted] • Global water safety concerns drive advanced heavy metal detection methods. • Innovative sensor development addresses limitations of AAS, TXRF in Heavy metal detection. • LIBS: Non-destructive method for trace element detection in water. • Fluorescent quantum dots provide highly sensitive sensors for heavy metal ion detection. • Nanozymes serve as versatile tools for compact and efficient on-site detection of heavy metal ions. Presence of contaminants, one Heavy metals and the other, radioactive substances has been a significant matter of concern throughout the world especially in some developing countries like India, Indonesia, Serbia, China, Uganda and Kenya. Even a minute concentration of these metals tends to cause toxicity in living organisms. Metallic ions like Cr (VI), As (V and III), Cd (II), Pb (II), Hg (II) and Cu (II) is accountable for several health disorders in personage such as hepatic dysfunction, impaired renal function, gastric carcinoma and cutaneous melanoma, presenile dementia et cetera. Consequently, the assessment of concentration of these ions is a requisite and further shape the structure of this review paper. Hence, the primary aim of this review literature is to assess and discuss the technologies used for the detection and quantification of heavy metals and also endeavours to shed light on the current state of detection methodologies. In this regard, consistent detection techniques and sensory devices have been developed and concurrently improved to synchronize with the presence of newer emerging substances resulting from modernization in industrialization. The scope of this analysis extends to a comprehensive exploration of both conventional and cutting-edge detection techniques and sensory apparatuses, aiming to provide insights into their effectiveness and potential for improvement. Additionally, the review will assess the applicability of these methods in various settings, considering factors such as LOD, accessibility, and accuracy. While traditional lab-based spectroscopic methods like Atomic Absorption Spectroscopy, Laser-Induced Breakdown Spectroscopy, and SARS are commonly used for heavy metal ion sensing and quantification, innovative sensor devices such as quantum dots sensors, bio-chemical sensors, and nanotechnology-based identification probes are increasingly being developed to improve detection capabilities. [ABSTRACT FROM AUTHOR]

In this work, a novel method of fabricating large‐area, low‐cost surface‐enhanced Raman spectroscopy (SERS) substrates is explained which yields nanostructured surface utilizing laser‐induced chemical etching of crystalline silicon (Si) in an hydrofluoric acid solution. Nanostructuring of Si surface is followed by deposition of a thin noble metal layer to complete the fabrication procedure. A 50 nm thick silver (Ag) layer is shown to maximize the SERS performance. The SERS effect is attributed to the electromagnetic field enhancement originating from the nanoscale surface roughness of Si that can be controlled by the illumination power, etch duration, and the spot size of the laser beam. The SERS substrates are found to be capable of detecting a Raman analyte dye molecule down to 10−11m. SERS performance of the Ag deposited substrates are compared to gold (Au) deposited substrates at 660 and 532 nm excitation. Nanostructured Si surface with Ag exhibits stronger SERS than with Au under 532 nm excitation exhibiting an enhancement factor as high as 109. Raman enhancement factor is calculated both by SERS spectra experimentally, and using finite‐elements simulation of the electric field enhancement. The applicability of the fabricated substrates is examined by adsorbing different analytes. [ABSTRACT FROM AUTHOR]

Surface-enhanced Raman spectroscopy (SERS) is an emerging technology that combines Raman spectroscopy and nanotechnology with great potential. This technology can accurately characterize molecular adsorption behavior and molecular structure. Moreover, it can provide rapid and sensitive detection of molecules and trace substances. In practical application, SERS has the advantages of portability, no need for sample pretreatment, rapid analysis, high sensitivity, and 'fingerprint' recognition. Thus, it has great potential in food safety detection. Alcoholic beverages have a long history of production in the world. Currently, a variety of popular products have been developed. With the continuous development of the alcoholic beverage industry, simple, on-site, and sensitive detection methods are necessary. In this paper, the basic principle, development history, and research progress of SERS are summarized. In view of the chemical composition, the beneficial and toxic components of alcoholic beverages and the practical application of SERS in alcoholic beverage analysis are reviewed. The feasibility and future development of SERS are also summarized and prospected. This review provides data and reference for the future development of SERS technology and its application in food analysis. [ABSTRACT FROM AUTHOR]

The design and fabrication of novel and robust surface enhanced Raman spectroscopy (SERS) substrate are crucial for the widespread application of SERS technique in the fields of chemistry, biology, and environmental science. Recently, metal organic framework (MOF) material has emerged as attractive material with many unique properties such as high porosity, tunable structure, and rich functionalities. With the help of MOF material, MOF-based SERS substrate can show high sensitivity, excellent selectivity and outstanding stability. Herein, we have reviewed the latest research progress of MOF-based SERS substrate. We mainly focus on the design principles for MOF-based SERS substrates according to the roles of MOF material. Then the recent applications of MOF-based SERS substrates have been summarized. Finally, the future challenges and potential opportunities in the development of MOF-based SERS substrates are discussed. [ABSTRACT FROM AUTHOR]

We report a simple preparation of surface enhanced Raman spectroscopy (SERS) substrates with gold concave nanocubes of different sizes, deposited onto aluminum slides. The SERS substrates were characterized using 4-Aminothiophenol. Resulting in that the substrate prepared with 55 nm nanocubes exhibits the higher analytical enhancement factor (AEF), 1.5 × 106. Moreover, the SERS substrates' performance was also evaluated for thiram detection using a series of water and tomato juice samples spiked with the pesticide. Our results show that the excellent performance of the substrate allows the detection of thiram with high sensitivity. The substrates were able to detect thiram with a limit of detection of 7 ppm and 14 ppm, respectively, in water and tomato juice. Our preliminary results open the possibility of using our methodology to detect diverse pollutants of interest. [ABSTRACT FROM AUTHOR]

A photonic nanojet (PNJ) from a microcavity is a narrow and intense beam of light used to enhance the emerging electric field. Metal nanoparticles (NPs), on the other hand, confine a strong field in their vicinity due to the resonance of the free electrons with the incident field. A hybrid combination of a microcavity with a NP can drastically enhance the output field. In this work, a systematic numerical study of the microcavity-NP system has been carried out to investigate the effect of the shape of the metal NPs on the output field strength. The single and their dimer NPs with different dimer nanogaps with PNJ producing microcavity have been investigated. Splitting of the broad dipole mode of the NP has also been observed. As an application of this study, the surface enhanced Raman spectroscopy factor of the order of 107 has been estimated for nano-cube dimer NP-microcavity hybrid system. [ABSTRACT FROM AUTHOR]

Edoxaban is a direct oral anticoagulant (DOAC) that has been recently indicated for the treatment of pulmonary embolism (PE) in SARS-CoV-2 infections. Due to its pharmacokinetic variability and a narrow therapeutic index, the safe administration of the drug requires its therapeutic drug monitoring (TDM) in patients receiving the treatment. In this work, we present a label-free method for the TDM of edoxaban by surface enhanced Raman spectroscopy (SERS). The new method utilises the thiol chemistry of the drug to chemisorb its molecules onto a highly sensitive SERS substrate. This leads to the formation of efficient hotspots and a strong signal enhancement of the drug Raman bands, thus negating the need for a Raman reporter for its SERS quantification. The standard samples were run with a concentration range of 1.4 × 10−4 M to 10−12 M using a mobile phase comprising of methanol/acetonitrile (85:15 v/v) at 291 nm followed by the good linearity of R2 = 0.997. The lowest limit of quantification (LOQ) by the SERS method was experimentally determined to be 10−12 M, whereas LOQ for HPLC-UV was 4.5 × 10−7 M, respectively. The new method was used directly and in a simple HPLC-SERS assembly to detect the drug in aqueous solutions and in spiked human blood plasma down to 1 pM. Therefore, the SERS method has strong potential for the rapid screening of the drug at pathology labs and points of care. [ABSTRACT FROM AUTHOR]

Surgeons face challenges in intraoperatively defining margin of brain tumors due to its infiltrative nature. Extracellular acidosis caused by metabolic reprogramming of cancer cells is a reliable marker for tumor infiltrative regions. Although the acidic margin‐guided surgery shows promise in improving surgical prognosis, its clinical transition is delayed by having the exogenous probes approved by the drug supervision authority. Here, an intelligent surface‐enhanced Raman scattering (SERS) navigation system delineating glioma acidic margins without administration of exogenous probes is reported. With assistance of this system, the metabolites at the tumor cutting edges can be nondestructively transferred within a water droplet to a SERS chip with pH sensitivity. Homemade deep learning model automatically processes the Raman spectra collected from the SERS chip and delineates the pH map of tumor resection bed with increased speed. Acidity correlated cancer cell density and proliferation level are demonstrated in tumor cutting edges of animal models and excised tissues from glioma patients. The overall survival of animal models post the SERS system guided surgery is significantly increased in comparison to the conventional strategy used in clinical practice. This SERS system holds the promise in accelerating clinical transition of acidic margin‐guided surgery for solid tumors with infiltrative nature. [ABSTRACT FROM AUTHOR]

Single-layer carbon dots (CDs) are used as capping agents to synthesize silver nanoparticles (AgNPs). The obtained nanohybrids (AgNPs/CDs) can be self-assembled into nanostructures like nanochains (1D-AgNPs/CDs), nanoflats (2D-AgNPs/CDs) or nanobodys (3D-AgNPs/CDs) by simply tuning the amount of added CDs. It is found that CDs play a key role in controlling the aggregation AgNPs/CDs. The formation mechanisms of the AgNPs/CDs aggregates have been discussed. On the basis, the effects of aggregation dimension on the surface plasmon absorption and surface enhanced Raman spectroscopy (SERS) activity of AgNPs/CDs are investigated and discussed. It is found that the aggregation of AgNPs/CDs creates strong localized surface plasmon resonance. Furthermore, the aggregated AgNPs/CDs of different dimension have similar absorption intensity in the range from 500 to 800 nm, which is most commonly used in the surface enhanced Raman spectroscopy (SERS) measurement. The outstanding local electromagnetic field of the aggregated AgNPs and the enrichment effect of the CDs towards the analytes make all the obtained materials to be SERS substrates. In particular, 2D-AgNPs/CDs exhibit an ultrahigh enhancement factor of 4.02 × 1014 and a good reproducibility during the SERS test, using crystal violet as the model target molecule. The applicability of 2D-AgNPs/CDs in SERS detection is further confirmed by the measurement of trace thiram residual in apple. The obtained CDs shelled AgNPs (AgNPs/CDs) can be self-assembled into 1D-, 2D- or 3D-CDs/AgNPs depending on the amount of CDs, and all the CDs/AgNPs aggregations have strong surface enhanced Raman spectroscopy (SERS) activities. [Display omitted] [ABSTRACT FROM AUTHOR]

Dopamine (DA) is an important catecholamine neurotransmitter involved in neural and hormonal functions. Neural diseases, as Parkinson's, are connected to a significant lowering of DA concentration to picomolar levels in cerebrospinal fluid. So, in this contribution, a hybrid active layer based on a perylene bisimide (PBI) derivative and multishaped Au nanostructures is proposed for the development of surface plasmon resonance (SPR) dopamine detection system. PBI molecules, transferred as thin film by the dip coating approach, are demonstrated to be able to detect dopamine down to 10–12m by SPR method. The presence of Au nanostructures promotes an important surface enhanced Raman scattering effect of Raman PBI signals highlighting a strong energetic communication between the two species. In this way, when PBI/Au nanostructures (AuNS) films are deposited by the layer‐by‐layer method and used for DA SPR detection, the sensitivity toward dopamine 10−12m is doubled. The PBI/AuNS hybrid layer is able to detect picomolar concentration of dopamine, due to the coupling of localized (AuNS) and propagating surface plasmons on SPR slide. In particular, an interfacial coupling among localized surface plasmon resonance on AuNS and the propagating plasmon on Au thin film (of SPR slide) can be promoted. [ABSTRACT FROM AUTHOR]

Tuning optical properties of plasmonic nanostructures, including their absorption, scattering, and local‐field distribution is of great interest for various applications that rely on optical energy regulated by plasmonic effects. Conventional plasmonic nanostructures enhance light scattering and absorption simultaneously, leading to compromise for either surface‐enhanced spectroscopy or thermoplasmonic applications. In this paper, a dual functional platform based on a hyperbolic meta particles (HMP) substrate that exhibits separate and tuneable wavelengths of absorption and scattering resonances for both thermoplasmonics and surface enhanced Raman spectroscopy (SERS), is demonstrated. Significantly, either light‐to‐heat conversion efficiency at the absorption resonance band or SERS performance at the scattering resonance band of the HMP substrate is improved in comparison to those of plasmonic gold nanoparticles. Taking advantage of the flexible control of the separate scattering and absorption channels, the influence of the absorption resonance band position on the SERS signal is also investigated. The platform shows unique potential for in vitro biosensing in thermal modulation and in situ monitoring. [ABSTRACT FROM AUTHOR]

A capillary-based SERS sensor was fabricated for ultrasensitive and selective detection of Hg2+ in water. Au@Ag core–shell NPs embedded with 4-mercaptobenzoic acid (4-MBA) (Au@4-MBA@Ag) were prepared by a seed growth method and fixed on the inner wall of the glass capillary to obtain the sensor. Owing to the amalgamation between Ag and Hg, the capillary-based SERS sensor can specifically recognize the reduced Hg2+ without any recognition element, and the resulted Ag/Hg amalgam can weaken the SERS activity of Ag shell; thus, the SERS intensity of the embedded 4-MBA at 1075 cm−1 gradually decreased with the increase of Hg2+ concentration. Under the optimum condition, the fabricated sensor can sensitively determine Hg2+ in water with a limit of detection (LOD) as low as 0.03 nM. The capillary-based SERS sensor offers the advantages of simple preparation, superior stability, and high selectivity, which is promising for rapid and on-site detection of Hg2+ in water combined with a portable Raman device. [ABSTRACT FROM AUTHOR]

In this work, an Au/g-C 3 N 4 /GO/Au hybrid nanofilm for surface-enhanced Raman scattering (SERS) substrate application was prepared by a facile layer-by-layer assembly technique using nanosheet-structured graphitic carbon nitride (g-C 3 N 4), graphene oxide (GO) and 40 nm-gold nanoparticles (Au NPs). The effects of composition, assembly sequence and assembly cycles on the SERS performance were optimized to achieve the SERS-active substrate. The detection limit of Au/g-C 3 N 4 /GO/Au substrate for crystal violet and rhodamine 6 G probe molecules reached as high as 10−8 M, with good stability and uniformity. Its further application in food colorants detection (erythrosine, carmine and temptation red) had successfully met the national food safety standards and the quantitative detection for erythrosine and temptation red had also been established. Based on finite-difference time-domain element simulation and density functional theory quantum chemical calculation, the mechanism of the SERS effect of the substrate was unveiled, which is attributed to the combination of electromagnetic enhancement effect of Au nanoparticle aggregates and chemical enhancement effect of GO and g-C 3 N 4. Notably, water droplet evaporation induced Raman enhancement was observed on the Au/g-C 3 N 4 /GO/Au substrate. This can be ascribed to the inhomogeneous evaporation of the droplet that promotes the enrichment of the probe molecules into the center of the droplet. This novel enhancement strategy provides a new idea for further improving detection sensitivity of SERS substrate materials. [Display omitted] [ABSTRACT FROM AUTHOR]

Nasopharyngeal cancer (NPC) is a malignant tumor with high prevalence in Southeast Asia and highly invasive and metastatic characteristics. Radiotherapy is the primary strategy for NPC treatment, however there is still lack of effect method for predicting the radioresistance that is the main reason for treatment failure. Herein, the molecular profiles of patient plasma from NPC with radiotherapy sensitivity and resistance groups as well as healthy group, respectively, were explored by label-free surface enhanced Raman spectroscopy (SERS) based on surface plasmon resonance for the first time. Especially, the components with different molecular weight sizes were analyzed via the separation process, helping to avoid the possible missing of diagnostic information due to the competitive adsorption. Following that, robust machine learning algorithm based on principal component analysis and linear discriminant analysis (PCA-LDA) was employed to extract the feature of blood-SERS data and establish an effective predictive model with the accuracy of 96.7% for identifying the radiotherapy resistance subjects from sensitivity ones, and 100% for identifying the NPC subjects from healthy ones. This work demonstrates the potential of molecular separation-assisted label-free SERS combined with machine learning for NPC screening and treatment strategy guidance in clinical scenario. [Display omitted] • The molecular profile of blood from nasopharyngeal cancer patients with radiotherapy resistance was explored by SERS for the first time. • Components in blood with different molecular weight were separated and analyzed to overcome the problem of informational lost. • This work would provide a non-invasive, convenient and easy-to-operation method for NPC screening and treatment strategy guidance. [ABSTRACT FROM AUTHOR]

Raman spectroscopy (RS) is a widely used analytical technique based on the detection of molecular vibrations in a defined system, which generates Raman spectra that contain unique and highly resolved fingerprints of the system. However, the low intensity of normal Raman scattering effect greatly hinders its application. Recently, the newly emerged surface enhanced Raman spectroscopy (SERS) technique overcomes the problem by mixing metal nanoparticles such as gold and silver with samples, which greatly enhances signal intensity of Raman effects by orders of magnitudes when compared with regular RS. In clinical and research laboratories, SERS provides a great potential for fast, sensitive, label-free, and non-destructive microbial detection and identification with the assistance of appropriate machine learning (ML) algorithms. However, choosing an appropriate algorithm for a specific group of bacterial species remains challenging, because with the large volumes of data generated during SERS analysis not all algorithms could achieve a relatively high accuracy. In this study, we compared three unsupervised machine learning methods and 10 supervised machine learning methods, respectively, on 2,752 SERS spectra from 117 Staphylococcus strains belonging to nine clinically important Staphylococcus species in order to test the capacity of different machine learning methods for bacterial rapid differentiation and accurate prediction. According to the results, density-based spatial clustering of applications with noise (DBSCAN) showed the best clustering capacity (Rand index 0.9733) while convolutional neural network (CNN) topped all other supervised machine learning methods as the best model for predicting Staphylococcus species via SERS spectra (ACC 98.21%, AUC 99.93%). Taken together, this study shows that machine learning methods are capable of distinguishing closely related Staphylococcus species and therefore have great application potentials for bacterial pathogen diagnosis in clinical settings. [ABSTRACT FROM AUTHOR]

[Display omitted] Stoichiometry and stability of electron donor–acceptor complexes formed by dibenzothiophene and its alkylated derivatives with DDQ and TCNE in nonpolar organic solvents has been investigated. 4,6-Dimethyldibenzothiophene produces the most stable 1: 1 complex with DDQ in agreement with energy levels of the π-donors HOMOs and π-acceptors LUMOs calculated by DFT. The results make possible an employment of the complexes for multiplex determination of polycyclic aromatic pollutants using surface enhanced Raman spectroscopy. [ABSTRACT FROM AUTHOR]

Determining the concentration of polycyclic aromatic hydrocarbons (PAHs) in water is vital for reducing negative effects on human health, such as cancer and malformation. This study proposed an alternative analytical method based on surface enhanced Raman spectroscopy and kernel principal components analysis combined with support vector regression (SVR) for the determination of PAH concentration in water. For this, a dataset containing 300 Raman spectra of polycyclic aromatic hydrocarbon mixtures was made using naphthalene (NAP), pyrene (PYR), and phenanthrene (PHE) with concentrations ranging from 0 to 1000 ppb. In order to improve the effect of the model detection, different pre-processed methods were applied: normalization, multiplicative scatter correction, detrending, standart normal variate transformation, and Savitzky–Golay smoothing. For comparison, partial least squares (PLS) and SVR with the polynomial-kernel were also used. The pre-processing method with the best prediction effect was SNV for all the three substances. For NAP, the optimal correlation coefficient of cross-validation (Rcv), correlation coefficient of prediction (Rpred), RMSECV, RMSEP, and RPD are 0.90, 0.937, 138.9, 117.4, and 2.9 ppb, respectively, while for PYR the optimal Rcv, Rpred, RMSECV, RMSEP, and RPD are respectively 0.881, 0.897, 152.3, 142.8, and 2.3 ppb. For PHE, the optimal Rcv, Rpred, RMSECV, RMSEP, and RPD are 0.980, 0.982, 64.5, 62.9, and 5.3 ppb, respectively. This study provides a new method with a better prediction effect for quantitative analysis of low concentrations of polycyclic aromatic hydrocarbons in water by using surface enhanced Raman spectroscopy. [ABSTRACT FROM AUTHOR]

Cancer has become a major killer threatening human health in today's society, and surface enhanced Raman spectroscopy (SERS) may provide a competitive choice for the sensitive detection of cancer‐related miRNAs. In this work, a synergistic calibrated SERS strategy based on MXene/molybdenum disulfide (MoS2)@Au nanoparticles (AuNPs) with controllable morphology is suggested for the ultrasensitive detection of miRNA‐182 by selecting the average intensity of its three own characteristic Raman peaks (at 382 cm−1 and 402 cm−1 corresponding to MoS2 and at 611 cm−1 corresponding to MXene) as a benchmark instead of additional beacon molecules. The linear goodness of fit (the determination coefficient R2) for this strategy is available in amounts up to 0.9995, which is significantly higher than that of single or double peak calibrated case, and thus improves the detection accuracy dramatically. Meanwhile, vertical MoS2 nanosheets anchored on layered MXene can provide uniformly ordered sites for accommodating suitably sized AuNPs as "hot spots" with controllable particle gap of 2.2 nm, resulting in the maximum amplified SERS signal at 1362 cm−1 generated by hairpin probe DNA with Cy5. A linear detection window from 10 am to 1 nm with an ultralow detection limit of 6.61 am for miRNA‐182 is achieved. [ABSTRACT FROM AUTHOR]

Carbon based dots capped tin oxide nanosheets (SnO 2 /CDs) were synthesized by liquid exfoliation of tin oxide (SnO 2) nanoparticles in the presence of single-layer carbon based (CDs). The obtained SnO 2 /CDs have lateral sizes of about 20–50 nm and heights of about 3–4 nm. A thin layer of CDs of about 1–2 nm in thickness are presence on the surface of the SnO 2 nanosheets. The SnO 2 /CDs present excellent surface enhanced Raman spectroscopy (SERS) activity due to the chemical enhancement (CM) led by the charge transfer between SnO 2 /CDs and the target molecules. The enhancement factor (EF) of the SnO 2 /CDs is 1.42 × 105, taking rhodamine 6G as a model target molecule. The SnO 2 /CDs are further hybridized with silver nanoparticles (AgNPs) using an in situ synthesis method. The obtained homogeneous nano-hybrids (SnO 2 /CDs@AgNPs) have a lot of nanogaps. The nanogaps among the AgNPs/CDs create strong electromagnetic enhancement (EM) due to the "hot spots" effect. The nanogaps among the SnO 2 /CDs and AgNPs/CDs allow the target molecules to be embedded, and thus gained both the CM effect of SnO 2 /CDs and the EM effect of AgNPs/CDs. As a result, the as-prepared SnO 2 /CDs@AgNPs exhibits excellent SERS activities, with an ultrahigh enhancement factor of 3.27 × 1011. Tin oxide nanosheets covered with carbon based dots are synthesized and further hybridized with silver nanoparticles (AgNPs) to prepare a novel surface enhanced Raman spectroscopy (SERS) substrate with an excellent SERS activity. Image 1 [ABSTRACT FROM AUTHOR]

The past two decades have witnessed the explosion of activities in the field of surface enhanced Raman spectroscopy (SERS). SERS platforms employ nano-structures that excite plasmonic modes with large local electromagnetic fields localized within small gap spaces between each constituting feature. Although the research-oriented SERS platforms yield significant signal enhancements to identify even single molecules, practical SERS-based sensors have not been fully introduced yet. The main reason behind this absence is the need for a cost-effective and reliable manufacturing method for controllable fabrication of plasmonic nano-gaps over large areas. In this article, we introduced a novel manufacturing process that enables fast and scalable fabrication of highly uniform sub-10-nm gaps that could yield large SERS signals. In this process, a conventional electroplating technique is used to produce unique nano-mushroom antenna arrays on a conducting substrate, resulting in controllable gap spaces between mushroom heads. By understanding the nature of mushroom shape antenna formation, we demonstrated the control of inter-metallic gaps down to 5 nm. We showed that the manufactured nano-structures yield Raman enhancements more than 108. Providing such large SERS signals that are uniform over large areas, our cost-effective fabrication technique could be very critical to realize practical SERS devices. [ABSTRACT FROM AUTHOR]