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ABSTRACT Gastric cancer (GC) is a highly lethal malignancy, seriously threatening people's physical health. Accurate screening of gastric cancer could improve the survival rate of patients. Therefore, exploring noninvasive and efficient cancer screening methods for gastric cancer is of great significance. In the past few years, exosomes have received much attention for their potential in disease diagnosis and treatment. Here, the aim of this study was to explore the detection of serum exosomes via surface‐enhanced Raman spectroscopy (SERS) technique based on TiN‐Ag@Ag sol composite substrate, and its potential application in gastric cancer diagnosis is evaluated. Exosomes were extracted from the serum of 31 GC patients and 31 healthy controls (HC) using an exosome kit. This study used various machine learning algorithms such as principal component analysis linear discriminant analysis (PCA‐LDA), partial least squares discriminant analysis (PLS‐DA), support vector machine (SVM), and k‐nearest neighbor (KNN) algorithm to analyze SERS spectra, in order to distinguish between HC and GC. The results show that the k‐nearest neighbor algorithm performs the best in HC and GC classification. These results indicate that the combination of SERS and machine learning methods provides a new technological approach for gastric cancer screening. This study offers a new proposal for the universal applicability of analysis and identification with SERS of serum exosomes samples in clinical diagnosis. [ABSTRACT FROM AUTHOR]

The field of semiconductor surface‐enhanced Raman scattering (SERS) substrates has experienced significant advancements, leading to a wide range of applications in several fields. However, the quest for new ultra‐sensitive semiconductor SERS materials is still of utmost importance. In this regard, an efficient and novel substrate, F4TCNQ/MoS2 heterostructure is introduced, assisted by V‐shaped aluminum anodic oxide (AAO) nanocavities with different depths. Utilizing the efficient charge transfer of organic/inorganic semiconducting heterostructure and the photoconfinement capability of the nanocavity structure of the AAO nanotemplate, excellent stability, fast sensing, enhanced Raman, and photodegradation activities are achieved. Due to its unique 3D structure, the optimized F4TCNQ/MoS2/AAO with 1500 nm depth achieves ultra‐high sensitivity detection of 9.0×10−16 M for conventional probe molecules. Furthermore, precise detection of water contaminants is observed for the first time with a V‐shaped heterostructure due to combined organic/inorganic features that differ significantly from conventional MoS2 structures or other metal/inorganic or inorganic/inorganic semiconductors. This research presents a novel and versatile strategy for SERS and demonstrates its diverse potential performance in practical applications. [ABSTRACT FROM AUTHOR]

This study discusses the influence of the morphological characteristics of molybdenum disulfide (MoS2) substrates on the detection efficiency of Rhodamine B (RhB) via surface‐enhanced Raman scattering (SERS). Commercially available MoS2 powder and vertically aligned (VA‐MoS2) synthesized using a chemical vapor deposition (CVD) technique are compared. The MoS2 substrates are functionalized with silver nanoparticles Ag(NPs) through DC‐magnetron sputtering employing nitrogen as reactive gas. Scanning electron microscopy is employed to probe the morphology of the Ag‐ functionalized MoS2 powder and VA‐MoS2 samples. Raman spectroscopy demonstrates a significant enhancement in the SERS signal that can be attributed 1) to the MoS2 valence band alteration reinforcing the chemical mechanism and 2) to the enhanced electric field generated by the Ag(NPs). The VA‐MoS2 substrate decorated with Ag(NPs) exhibited a high enhancement factor of 3.5 × 108 and a low limit of detection of 10−12 m. The abundance of platelet edges, enhanced by the vertically aligned shape, offers a higher amount of strong and localized electromagnetic field formed between nanoparticle dimers located on the edges, leading to a pronounced enhancement of the SERS signal. [ABSTRACT FROM AUTHOR]

Au@Pt core-satellite nanoparticles (CSNPs) with dual-functionality as both catalyst and surface-enhanced Raman scattering (SERS) substrate are successfully synthesized by decorating Pt nanocrystals on plasmonic Au colloids. The coupling "hotspot" structures at the Au-Pt interface significantly promotes the catalytic decarboxylation reaction, and provides spectroscopic insights into the molecule-plasmon interface in universal plasmon-promoted catalytic reactions. [Display omitted] Plasmon-induced hot carriers are a promising "active" energy source, attracting increasing attention for their potential applications in photocatalysis and photodetection. Here, we hybridize plasmonic Au spherical nanoparticles (SNPs) with catalytically active Pt nanocrystals to form Au@Pt core-satellite nanoparticles (CSNPs), which act as both an efficient catalyst for plasmon-promoted decarboxylation reaction and a robust surface-enhanced Raman scattering (SERS) substrate for plasmon-enhanced molecular spectroscopic detection. By regulating the coverage of Pt nanocrystals on the Au SNPs, we modulated the "hotspot" structures of the Au@Pt CSNPs to optimize the SERS detecting capability and catalytic decarboxylation performance. The coupling functionalities enable us with unique opportunities to in-situ SERS monitor universal reactions catalyzed by active catalysts (e.g. Pt, Pd) in the chemical industry in real-time. The decarboxylation rate of 4-mercaptophenylacetic acid was dynamically controlled by the surface catalytic decarboxylation step, following first-order overall reaction kinetics. Moreover, the reaction rate exhibited a strong correlation with the local field enhancement |E/E 0 |4 of the hotspot structure. This work provides spectroscopic insights into the molecule-plasmon interface under the plasmon-promoted catalytic reactions, guiding the rational design of the plasmonic interface of nanocatalysts to achieve desired functionalities. [ABSTRACT FROM AUTHOR]

The applications for lateral flow assay (LFA) strips in point-of-care testing have been significantly constrained by their insufficient sensitivity and reproducibility. To address these inherent issues, we developed surface-enhanced Raman scattering (SERS)-based LFA strips, in which highly symmetric Au nanostars (Sym-AuNS) were employed as the sensing element. Due to the uniform tip-sharp nanostructure and a certain number of branches on the surface of Sym-AuNS, it generates a uniform hotspot distribution, thus producing a strong and stable SERS signal. As a proof of concept, human IgG was chosen as the target to evaluate the performance of the proposed SERS-LFA strips. In human serum spiked samples, the limit of detection for human IgG detection was achieved as low as 38 ng/mL, which exhibited a 2-fold, 3-fold, and 13-fold sensitivity improvement compared with the SERS-LFA strips using conventional gold nanostars (AuNS), enzyme-linked immunosorbent assays (ELISA), and the conventional LFA strips, respectively. Furthermore, the SERS-LFA strips demonstrated high assay reproducibility, with a relative standard deviation of 7.75% for five repeated tests, much lower than those of SERS-LFA strips using AuNS (24.6%), ELISA (12.42%), and conventional LFA strips (31.32%). These results demonstrate that the construction of sensitive and reproducible SERS-LFA strips was obtained, and this platform using Sym-AuNS as SERS nanoparticles paves the way for a promising approach in immunoassay technology. [ABSTRACT FROM AUTHOR]

A surface‐enhanced Raman scattering (SERS) filter membrane based on a Janus copper/poly(vinylidene fluoride)/zinc oxide/silver/zeolitic imidazolate framework‐8 (Cu/PVDF/ZnO/Ag/ZIF‐8, J‐CPZAZ) is designed in this work, which can extract and enrich methylmercury (MeHg) from real samples containing various sizes and types of interferents into the PVDF/ZnO/Ag/ZIF‐8 SERS enhancement unit directly within 2 min. Combined with the microcavity structure in PVDF/ZnO/Ag/ZIF‐8, J‐CPZAZ can also localize the incident light at the same position. This co‐confinement effect of “hotspot‐molecule” effectively lowers the limit of detection of MeHg to 10−10 m. Interestingly, a controllable wettability of J‐CPZAZ endows it with good oil‐water separation function for separating various kinds of MeHg extractant (>95%) from mixed aqueous solution. Based on these features, a dual‐layer J‐CPZAZ filter membrane is further successfully fabricated, enabling both‐in‐one detection and removal of MeHg from real water environments. In the experiments, real water samples are selected from six different water areas in Shandong Province, China, for relevant tests and compared the results with those obtained using traditional gas chromatography. The results demonstrate that the dual‐layer J‐CPZAZ filter membrane exhibits both high MeHg removal efficiency (≈100%) and detection accuracy (average error < 1.8%), showcasing great application potential. [ABSTRACT FROM AUTHOR]

When decorated with plasmonic nanoparticles, pulled optical nanofibers are compatible with plasmonic techniques enabling the ability to probe microenvironments with high spatial and temporal resolution. Although the nanofibers exhibit excellent compatibility for biological samples including cells and tissues, the underlying interactions between the dielectric fiber, plasmonic nanoparticles, and the incident light have been minimally explored. It is shown that the complex coupling of optical and plasmonic properties within the nanofiber strongly influences both the surface‐enhanced Raman scattering (SERS) and photothermal capabilities. Through a combination of experimental results and simulated electric field distributions and spectra it is demonstrated that, although the nanofibers may be homogeneously decorated with gold nanoparticles, the optical effects spatially differ. Specifically, the SERS performance varies periodically based on the diameter of the nanofiber, which is associated with ring resonator modes, while the photothermal effects are more homogeneous over the same diameters, highlighting differences in optoplasmonic properties at this length scale. Through understanding these effects, it may become possible to control temperatures and SERS properties to evaluate processes with micrometric spatial resolution, such as the analytes secreted during temperature‐induced death of single cells. [ABSTRACT FROM AUTHOR]

Surface‐enhanced Raman scattering (SERS) sensors typically employ nanophotonic structures that support high‐field confinement and enhancement in hotspots to increase the Raman scattering from target molecules by orders of magnitude. In general, high field and SERS enhancement can be achieved by reducing the critical dimensions and mode volumes of the hotspots to nanoscale. To this end, a multitude of SERS sensors employing photonic structures with nanometric hotspots have been demonstrated. However, delivering analyte molecules into nanometric hotspots is challenging, and the trade‐off between field confinement/enhancement and analyte delivery efficiency is a critical limiting factor for the performance of many nanophotonic SERS sensors. Here, a new type of SERS sensor employing solid‐metal nanoparticles and bulk liquid metal is demonstrated to form nanophotonic resonators with a nanoparticle‐on‐liquid‐mirror (NPoLM) architecture, which effectively resolves this trade‐off. In particular, this unconventional sensor architecture allows for the convenient formation of nanometric hotspots by introducing liquid metal after analyte molecules are efficiently delivered to the surface of gold nanoparticles. In addition, a cost‐effective and reliable process is developed to produce gold nanoparticles on a substrate suitable for forming NPoLM structures. These NPoLM structures achieve two orders of magnitude higher SERS signals than the gold nanoparticles alone. [ABSTRACT FROM AUTHOR]

Currently, empirical therapy regimens are often used in the treatment of infectious diseases that are not based on data on pathogen resistance. One of the main reasons for the unjustified prescription of antibacterial drugs is the lack of rapid and at the same time universal methods of determining the antibiotic resistance of the pathogen. The most widely used culture techniques, such as the microdilution method, require a long time to generate the necessary number of bacterial cells. Less time-consuming methods of resistance assessment (genomic or proteomic) are based on the determination of specific markers (resistance genes, overexpression of certain proteins, etc.); in this case, the specific protocol is most often applicable to a narrow number of both microorganism strains and antibiotics. Previously, we demonstrated the possibility of using Raman spectroscopy (RS) technology for quantitative determination of the product of bacterial cell activity in the MTT assay, formazan, directly in the cell suspension. The absence of the formazan isolation step simplifies the assay and increases its accuracy. The analysis time did not exceed 2 h while maintaining the versatility of the MTT assay itself. Limitations of the developed protocol for RS detection of the MTT assay results include a high sensitivity threshold of 107 CFU/mL for the bacterial cell concentration, so a preliminary stage of cultivation is necessary for samples with a low bacterial content. Here, we propose a method to increase the sensitivity of formazan determination by utilizing the effect of surface-enhanced Raman scattering (SERS) on gold nanoparticles. As a result of this study, the optimal conditions for SERS analysis of formazan in both solution and suspension of Escherichia coli cells are selected. Formazan signal amplification due to the use of SERS on gold nanoparticles instead of RS allowed us to reduce the sensitivity threshold for the number of bacterial cells in the sample by at least 30 times, up to 3 × 105 CFU/mL. This sensitivity is not the limit of the SERS technology capabilities because the introduction of other types of nanoparticles (more optimal in shape, size, concentration, etc.) into the experiment will allow one to achieve even higher signal amplification. [ABSTRACT FROM AUTHOR]

A bimetallic core–shell-shell nanorods structure with gap-embedded Raman reporter 5,5′-dithio-bis-(2-nitrobenzoic acid) (DTNB) was developed and applied as a SERS-active nanotag in surface-enhanced Raman scattering lateral flow immunoassay (SERS-LFIA) of the insecticide fipronil. Due to the strong SERS signal of the AuDTNB@AgDTNB@AgNRods, fipronil is detected with extremely low detection limit of 4.6 pg/mL. To the best of our knowledge, the proposed technique is the first SERS-LFIA of fipronil, proven to be effective in the selective determination of the target analyte and capable of detecting fipronil in a matrix of food samples (cucumber and apple juice) with recoveries of 97.0–117.0%. Moreover, the applied functionalization of the SERS nanotag with anti-species antibodies has provided a versatile immunoprobe that could improve performance of different LFIAs. [ABSTRACT FROM AUTHOR]

Hydrogen peroxide (H2O2) has an important role in living organisms, and its detection is of great importance in medical, chemical, and food safety applications. This review provides a comparison of different types of Surface-enhanced Raman scattering (SERS) sensors for H2O2 and related substances with respect to their detection limits, which are of interest due to high sensitivity compared to conventional sensors. According to the latest research report, this review focuses on the sensing mechanism of different sensors and summarizes the linear range, detection limits, and cellular applications of new SERS sensors, and discusses the limitations in vivo and future prospects of SERS technology for the detection of H2O2. [ABSTRACT FROM AUTHOR]

Surface-enhanced Raman scattering (SERS) holds significant potential across environmental monitoring, materials science, and biomedical applications. However, challenges regarding ultra-sensitive detection and repeatability are bottlenecks for practical applications, especially in terms of detection uniformity. In this study, we utilized surface acoustic waves (SAW) in conjunction with Raman spectroscopy to actively enrich 5 μL of 50 nm gold nanoparticles (AuNPs), thereby achieving innovative SERS-active sensing. This dynamic enrichment process enables the dense and uniform aggregation of AuNPs in droplets, thereby facilitating reliable ultrasensitive detection. The SAW system was further optimized through hydrophobic surface treatment. Using 4-mercaptobenzoic acid as a probe analyte, our SAW-SERS method successfully detected concentrations as low as 10−8 mol/L. The surface acoustic waves had the capability to significantly amplify Raman signal intensity up to 100 compared to conventional drying methodologies. This SAW-induced AuNP clustering technology offers a rapid, label-free SERS sensing method characterized by exceptional sensitivity and uniformity. [ABSTRACT FROM AUTHOR]

A metasurface composed of silver nanoflower arrays, which exhibit asymmetrical absorption and surface‐enhanced Raman scattering (SERS) due to hybrid plasmonic effects, is reported. The silver nanoflowers are fabricated by oblique deposition of silver on a polymer nanohole array on a glass substrate, forming petal‐like semicontinuous thin films on the inner walls of the holes. Depending on the deposition angle, three‐ or five‐petal nanoflowers are obtained. The nanoflower arrays show strong reflection from the air side and broadband and wide‐angle absorption from the glass side, as a result of transmission surface plasmon resonance and localized surface plasmon resonance, respectively. The three‐petal structure, which absorbs most of the incident light from the glass side, induces a localized enhancement of electric field in the center of each nanohole, providing a high‐sensitivity SERS substrate. The SERS performance of the metasurface by direct measurement and near‐field simulation is demonstrated. [ABSTRACT FROM AUTHOR]

Fipronil, a phenylpyrazole insecticide, is widely used but raises concerns regarding potential human health risks. This study introduces an aptasensor that utilizes Au@Ag nanoparticles (NPs) as a Raman-enhanced substrate for detecting fipronil residues in eggs. In this system, 4-mercaptobenzoic acid (4-MBA) serves as the Raman signaling molecule, anchored to Au@Ag NPs via Ag-S bonds. The presence of an aptamer initially reduces the 4-MBA Raman signal, which is subsequently restored to varying extents when different concentrations of fipronil are introduced. Thus, fipronil is indirectly quantified by measuring the intensity of the 4-MBA Raman signal. Under optimized conditions, the sensor demonstrates a linear detection range for fipronil between 50 and 400 nM with a coefficient of determination (R2) of 0.9968, and a detection limit of 15.68 nM. It also exhibits excellent selectivity and sensitivity towards fipronil. Furthermore, recovery rates for fipronil detection in egg samples ranged from 90 to 100%, with a relative standard deviation (RSD) below 5%, underscoring the method's strong potential for practical applications. [ABSTRACT FROM AUTHOR]

Nucleic acids (deoxyribonucleic acid – DNA and ribonucleic acid – RNA) are essential components of all living organisms, with DNA encoding genetic information and RNA facilitating vital biological processes. The detection of nucleic acids having a specific sequence is crucial for identifying organisms and diagnosing genetic diseases. Because surface-enhanced Raman spectroscopy (SERS) is considered as one of the most promising analytical methods that offers important benefits such as short analysis time and exceptional sensitivity compared to other techniques, many groups are trying to apply SERS for nucleic acid detection. This review discusses how SERS spectroscopy can be used for DNA/RNA detection. Beginning with an overview of SERS theory, we delve into various SERS DNA/RNA sensors, including those based on a direct analysis of the SERS spectra of nucleic acids, and many types of sensors based on a selective hybridisation of probe and target nucleic acids. We describe how various types of sensors with increased sensitivity and reliability have evolved (from the first SERS DNA/RNA sensors described in the literature to recently developed ones). Challenges and future directions in SERS sensor development for nucleic acid detection and determination are also discussed. This comprehensive review aims to help researchers understand the field's nuances, and to foster advancements in the use of SERS spectroscopy in the medical sector. [ABSTRACT FROM AUTHOR]

Tuberculosis is a highly infectious disease caused by the bacterium Mycobacterium tuberculosis, and the spread of this agent has caused serious health problems worldwide. The rapid and accurate detection of M. tuberculosis is essential for controlling the spread of infection and for preventing the emergence of multidrug-resistant strains. In this study, the powerful trans-cleavage ability of CRISPR-Cas12a for ssDNA was combined with a surface-enhanced Raman spectroscopy (SERS)–based strategy to establish a CRISPR-SERS sensor for the hypersensitive detection of M. tuberculosis DNA. We observed a linear relationship between the concentration of M. tuberculosis DNA and the output signal over the range of 5 to 100 pM. The equation describing the standard curve was y = 24.10x + 1594, with R2 = 0.9914. The limit of detection was as low as 4.42 pM for genomic DNA, and a plasmid containing an M. tuberculosis–specific sequence was detected at 5 copy/μL. A detection accuracy of 100% was achieved in the analysis of DNA isolated from the sputum of hospitalized patients with tuberculosis. The entire detection process is simple to deploy and only takes 50 min and results in the sensitive and specific detection of M. tuberculosis DNA. This study provides a new method for the detection of tuberculosis. The tool is stable and can be utilized on-site, and it thus broadens the diagnostic application of CRISPR-Cas12a-based sensor technology. [ABSTRACT FROM AUTHOR]

The flexible SERS substrate has attracted numerous interests due to its potential function of in situ detection of contaminants in various emerging applications. Here, we develop a facile and cost-effective layer-by-layer transfer strategy to fabricate a flexible SERS substrate by assembling gold nanospheres (Au NSs) onto a polystyrene microsphere (PS) array on PDMS. Importantly, this technique requires no large-scale instrument and is easy to operate with high reproducibility and tunability. Specially, the sizes of Au NSs and PS were systemically adjusted to optimize the SERS performance of the 3D flexible SERS substrate. Moreover, the layer-by-layer transfer method allows for patterned assembly, and the morphology of the nanocrystals as well as the material of the substrate can be flexibly regulated. Benefiting from the high sensitivity, good homogeneity, and time stability of the 3D transparent SERS substrate, the in situ measurement and quantitative analysis of fungicide residues on the surface of fish was successfully demonstrated without any requirement of sample extraction. As a result, this layer-by-layer transfer technology provides a route for the formation of a 3D flexible SERS sensor with promising applications for in situ and real-time detection of pollutants. [ABSTRACT FROM AUTHOR]

Surface-enhanced Raman scattering (SERS) is widely used for trace detection of substances, and the key to this technology lies in the preparation of the substrate material. In this study, a composite SERS material of Au NRs/4-MBA/PAM was constructed and characterized to better immobilize the reference molecule 4-mercaptobenzoic acid (4-MBA). Electron transmission microscopy results demonstrated that the PAM film helps Au NRs to pack closely, enhancing the stability of the material structure and reducing the interference of external environmental factors on the response of 4-MBA, thus improving the accuracy of quantitative determination. Comparative experimental results with the Au NRs/4-MBA substrate showed that the relative standard deviations (RSDs) of the detection results for MG on different batches of Au NRs/4-MBA/PAM were less than 8.0%, and the RSDs of different points on the same material were less than 10.0%, indicating that the Au NRs/4-MBA/PAM has higher uniformity, better reproducibility, and higher sensitivity in detecting malachite green (MG). Applying this material in the recovery determination of fish extract showed that the recovery rates of MG were between 75.60% and 83.24%. Therefore, the Au NRs/4-MBA/PAM substrate can accurately detect and quantify veterinary drug residue in complex matrices such as food tissue. [ABSTRACT FROM AUTHOR]

MXenes, the largest family of 2D transition metal carbides/nitrides, have emerged as promising materials for various applications due to their exceptionally fascinating properties. In this study, the potential of MXenes is investigated in plasmonic applications, particularly focusing on surface‐enhanced Raman scattering (SERS) and broadband photodetection. The study explored a broader range of light‐matter interactions based on edge plasmons that emerge at sub‐monolayer coverage of MXene, while existing studies have primarily focused on thicknesses exceeding tens of nanometers. Additionally, by incorporating MXenes onto 3D trench nanostructures, To maximize their plasmonic properties is aimed by enhancing the manifestation of edge plasmons, leading to intensified light amplification. The fabricated opto‐electronic devices exhibit remarkable sensitivity in SERS detection, achieving a detection limit as low as ≈0.1 nm for the target dye molecule, significantly surpassing typical thresholds for non‐metal‐based detection. Additionally, the enhancement factor exceeds that of commercially available Au‐based SERS substrates. Furthermore, MXene‐based photodetectors demonstrate competitive photoresponsivity and response time, particularly toward the near‐infrared (NIR) wavelength bands, which are challenging to achieve with MXene‐based photodetectors. Through a comprehensive analysis, including electric field calculations, the mechanisms driving the observed enhancements are unveiled, primarily attributing them to edge plasmons. [ABSTRACT FROM AUTHOR]

Herein, a surface-enhanced Raman scattering (SERS) substrate with good sensitivity and reproducibility is fabricated by using a "one-step" process. Patterned Au nanostructures were generated employing copolymer brushes as templates, subsequently undergoing the reduction of AgNO3. Impressively, the entire experimental procedure eschews intricate synthesis steps or the necessity for stabilizer additives. The resultant Ag shell layer evenly encapsulates the Au core, yielding densely packed Ag-coated Au (Au@Ag) nanoparticles. These patterned Au@Ag nanoparticle assemblies exhibited remarkable Raman performance, achieving a minimum concentration of detection of 100 pM and an average enhancement factor of 8.8 × 109 when using 4-mercaptobenzoic acid served as the probe molecule. Experimental outcomes and analyses pertaining to thiram, methylene blue, and rhodamine 6G (R6G) confirm the substrate's pronounced Raman effect and its broad range of potential applications. [ABSTRACT FROM AUTHOR]

A nanoplasmonic biosensor for the precise detection of severe acute respiratory syndrome coronavirus 2 (SARS‐CoV‐2) by leveraging advances in nanostructured sensing materials and highly selective monoclonal antibodies is presented. The sensor integrates plasmonic Au nanostructures optimized for surface‐enhanced Raman scattering (SERS), enhancing sensitivity through unique light interactions at the nanoscale. Coupled with exclusive antibodies that specifically target SARS‐CoV‐2 and its evolving variants, this sensor demonstrates remarkable selectivity and versatility. Validated with 270 clinical samples, it demonstrates a sensitivity of 98.9% and specificity of 100%. More importantly, the virus in nasopharyngeal swab samples collected over 3 years, marking the long‐term, large‐scale clinical validation of the nanoplasmonic biosensor for SARS‐CoV‐2 is been successfully detected. Furthermore, the integration of this sensor with face masks enables the detection of airborne SARS‐CoV‐2, highlighting its potential for routine management of coronavirus disease 2019 (COVID‐19). [ABSTRACT FROM AUTHOR]

The surface of hydroxyapatite (HA) was functionalized with silver nanoparticles by reducing silver nitrate in the presence of glucose or hydrazine hydrochloride. Two types of (HA)Ag nanocomposite were obtained presumably possessing excess negative charge ((HA)Ag-I) or positive charge ((HA)Ag-II). Plasmonic coatings of (HA)Ag-I and (HA)Ag-II nanoparticles were formed on the surface of glass substrates using the droplet deposition method and their structural and spectral properties were studied. A comparative study of the intensity of surface-enhanced Raman scattering (SERS) spectra of cationic and anionic porphyrins CuTMpyP4 and CuTPPS4 as well as rhodamine 6G adsorbed on the surface of both types of nanocomposites was carried out. Plasmonic structures (HA)Ag-I provide the greatest enhancement of the SERS signal for the cationic porphyrin CuTMpyP4, while high spectral intensity is observed for the anionic porphyrin CuTPPS4 adsorbed on films of the (HA)Ag-II composite, which is almost forty times higher than for (HA)Ag-I. For Rh6G molecules with charge +1, the efficiency of the SERS signal amplification by (HA)Ag-II nanostructures is several times higher than by plasmonic films of (HA)Ag-I. Hence, feasibility was demonstrated for obtaining various SERS-active substrates with highly-efficient SERS enhancement for both anionic and cationic analyte molecules by changing the synthesis conditions. [ABSTRACT FROM AUTHOR]

A novel technique was developed for the preparation of bilayer sandwich-type structures containing monolayers or laterally-oriented silver nanoplates electrostatically deposited onto thin polymer films. The surface-enhanced Raman scattering (SERS) signal of 4-mercaptobenzoic acid in the ligand layer of the silver nanoplates was found to depend on the surface concentration of the deposited silver nanoplates in the monolayer. A two-fold enhancement was found for the surface-enhanced Raman scattering signal of the analyte located in the gaps between the silver nanoplate monolayers compared to the signal from a single silver nanoplate monolayer with identical surface concentration of the analyte molecules. [ABSTRACT FROM AUTHOR]

Schiff base reactions are widely used in pharmacy, catalysis, and volatile aldehyde detection. However, common biomarker sensing methods struggle to monitor this reaction process precisely due to their sensitivity, their time-consuming nature, and complex substrates. Here, we introduce the Nanoparticle-on-Mirror structure for in situ monitoring this reaction process through the application of a Au nanoparticle-p-Aminothiophenol-Au thin-film platform by surface-enhanced Raman scattering (SERS). Owing to the exposure of -NH2 groups and the local ultra-strong electromagnetic field in the nanocavity, the Schiff base reactions process can be rapidly monitored within two minutes. Meanwhile, the monitoring platform can detect benzaldehyde molecules as low as 10−6 M, showing excellent SERS performance. Notably, the Au-nanoparticle-p-Aminothiophenol-Au thin-film platform exhibited anti-interference and specificity, being able to identify BA in the presence of interference. The use of the Au-nanoparticle-p-Aminothiophenol-Au thin-film platform provides a sensing method for Schiff base reactions with accuracy and simplicity of operation, achieving a balanced approach for low-cost and high-performance real-time monitoring, which is expected to be applied in various catalytic reaction process monitoring and catalyst design processes. [ABSTRACT FROM AUTHOR]

A Raman-active boronate modified surface-enhanced Raman scattering (SERS) microporous array chip based on the enzymatic reaction was constructed for reliable, sensitive, and quantitative monitoring of D-Proline (D-Pro) and D-Alanine (D-Ala) in saliva. Initially, 3-mercaptophenylboronic acid (3-MPBA) was bonded to Au-coated Si nanocrown arrays (Au/SiNCA) via Au–S bonding. Following this, H2O2 obtained from D-amino acid oxidase (DAAO)-specific catalyzed D-amino acids (D-AAs) further reduced 3-MPBA to 3-hydroxythiophenol (3-HTP) with a new Raman peak at 882 cm−1. Meanwhile, the original characteristic peak at 998 cm−1 remained unchanged. Therefore, the I882/I998 ratio increased with increasing content of D-AAs in the sample to be tested, allowing D-AAs to be quantitatively detected. The Au/SiNCA with large-area periodic crown structure prepared provided numerous, uniform "hot spots," and the microporous array chip with 16 detection units was employed as the platform for SERS analysis, realizing high-throughput, high sensitivity, high specificity and high-reliability quantitative detection of D-AAs (D-Pro and D-Ala). The limits of detection (LOD) were down to 10.1 µM and 13.7 µM throughout the linear range of 20–500 µM. The good results of the saliva detection suggested that this SERS sensor could rapidly differentiate between early-stage gastric cancer patients and healthy individuals. [ABSTRACT FROM AUTHOR]

Polymer‐based chiral materials with exceptional optical activity can dramatically impact integrated chiral photonics due to the tunability of their optical responses coupled with ease of fabrication. Realizing these applications requires increasing the absorbance dissymmetry factor. Here, in situ, the synthesis of gold nanostars is introduced in a chiral polymer medium to produce chiral polymer‐anisotropic plasmonic nanocrystal nanocomposites. The optimized nanocomposite shows a tenfold enhancement of dissymmetry factor, gabs (up to 0.64) and a corresponding 46‐fold augmented circular dichroism (CD) value upon annealing, relative to the annealed pure chiral polymer film. Moreover, the enhancement relative to the non‐annealed polymer‐gold nanostar nanocomposite is strikingly higher: a 35‐fold increase in gabs and a 4272‐fold increase in CD. Based on computational analysis, it is concluded that the local plasmon field enhancement around the crevices and tips of nanostars is mainly responsible for the observed effect which is further supported by a signal enhancement in Surface Enhanced Raman Scattering (SERS). Thus, this study underscores the significant role of close‐range plasmon interactions in altering the chiroptical response of nanocomposite materials and a practical pathway toward the realization of next‐generation integrated photonics and optoelectronic circuitry with photon spin control. [ABSTRACT FROM AUTHOR]

Preeclampsia (PE) is a serious complication that poses risks to both mothers and their children. This condition is typically asymptomatic until the second or even third trimester, which can lead to poor outcomes and can be costly. Detection is particularly challenging in low- and middle-income countries, where a lack of centralized testing facilities coincides with high rates of PE-related maternal mortality. Variations in the levels of hsa-miR-17-5p have been identified as constituting a potential early indicator for distinguishing between individuals with PE and those without PE during the first trimester. Thus, developing a screening test to measure hsa-miR-17-5p levels would not only facilitate rapid detection in the early stages of pregnancy but also help democratize testing globally. Here, we present a proof-of-principle lateral-flow assay (LFA) designed to measure hsa-miR-17-5p levels using DNA-hairpin recognition elements for enhanced specificity and nanoprobes for sensitive surface-enhanced resonance Raman scattering (SERS) signal transduction. The theoretical limit of detection for hsa-miR-17-5p was 3.84 × 10−4 pg/µL using SERS. [ABSTRACT FROM AUTHOR]

Antibiotic residues in dairy products have become an undeniable threat to human health. Surface‐enhanced Raman spectroscopy (SERS) has been widely used in efficiently detecting antibiotics because of its characteristics including fast response, high resolution, and strong resistance to moisture interference. However, as a core part of SERS technology, the design principle and detection performance of enhanced substrates used in monitoring antibiotics in dairy products have not yet received enough attention. Thus, it is necessary to give a critical review of the recent developments of SERS substrates for monitoring antibiotics in dairy products, which can be expected to provide inspiration for the efficient utilization of SERS technology. In this work, advances in various SERS substrates applied in sensing antibiotics in dairy products were comprehensively reviewed. First, the enhancement mechanisms were introduced in detail. Significantly, the types of enhanced materials (plasmonic metal particles [PMPs], PMPs/semiconductor composite materials) and biometric design strategies including immunoassay, aptamer, and molecularly imprinted polymers‐based SERS biosensors applied in dairy products were systematically summarized for the first time. Meanwhile, the performance of SERS substrates used for the detection of antibiotics in dairy products was addressed from the aspects of dynamic linear range and detection restriction strategy. Finally, the conclusions, challenges, and future prospects of SERS substrates for antibiotic monitoring in dairy products were deeply discussed, which also provide new opinions and key points for constructing SERS substrates applied in complex food matrix in the future. [ABSTRACT FROM AUTHOR]

Abstract Nanometal-based composite fibers have been widely explored in flexible sensors due to their outstanding optical and electrical properties. However, the weak binding force between metallic nanomaterial and fiber greatly limits the real application. In this work, nano silver (Ag) are strongly bonded with poly(3,4-ethylenedioxythiophene)-poly (styrene sulfonate) (PEDOT: PSS) fiber by the wet-spun process. Ag-S chemical bonds are formed by the interaction of Ag and PEDOT. The Ag/PEDOT: PSS composite fiber shows excellent surface-enhanced Raman scattering (SERS) sensitivity on Rhodamine 6G (R6G) molecules. The detection limit can reach 10–11 M and Raman enhancement factor (EF) is of 1.3 × 107. The high-sensitive SERS activity of Ag/PEDOT: PSS composite fiber mainly results from PEDOT: PSS, and the enhancement factor is 3 orders of magnitude better than that of other PEDOT: PSS based SERS substrates. Moreover, the composite fiber has metal-level conductivity of 1019 S/cm. This is 5 times higher than the conductivity of PEDOT: PSS fiber and a two-fold improvement over the reported values for nanometal/PEDOT: PSS based fabrics. The composite fiber has electric stability under bending test with bending speeds of 2 Hz indicating the composite fiber has good structural stability. In addition, the temperature of the composite fiber with 7 cm length can reach 76.5 °C at a voltage of 18 V. Additionally, the composite fiber shows anti-bacterial property and melting drop resistance, which pave the way for the integration of fiber-based optical and electrical sensors in the future multifunctional flexible devices.

Abstract Osteoporosis (OP) is a chronic disease characterized by diminished bone mass and structural deterioration, ultimately leading to compromised bone strength and an increased risk of fractures. Diagnosis primarily relies on medical imaging findings and clinical symptoms. This study aims to explore an adjunctive diagnostic technique for OP based on surface-enhanced Raman scattering (SERS). Serum SERS spectra from the normal, low bone density, and osteoporosis groups were analyzed to discern OP-related expression profiles. This study utilized partial least squares (PLS) and support vector machine (SVM) algorithms to establish an OP diagnostic model. The combination of Raman peak assignments and spectral difference analysis reflected biochemical changes associated with OP, including amino acids, carbohydrates, and collagen. Using the PLS-SVM approach, sensitivity, specificity, and accuracy for screening OP were determined to be 77.78%, 100%, and 88.24%, respectively. This study demonstrates the substantial potential of SERS as an adjunctive diagnostic technology for OP.