Surface-enhanced Raman Scattering Research Articles

Controlled Fabrication of Wafer-Scale, Flexible Ag-TiO2 Nanoparticle-Film Hybrid Surface-Enhanced Raman Scattering Substrates for Sub-Micrometer Plastics Detection.

As an important trace molecular detection technique, surface-enhanced Raman scattering (SERS) has been extensively investigated, while the realization of simple, low-cost, and controllable fabrication of wafer-scale, flexible SERS-active substrates remains challenging. Here, we report a facile, low-cost strategy for fabricating wafer-scale SERS substrates based on Ag-TiO2 nanoparticle-film hybrids by combining dip-coating and UV light array photo-deposition. The results show that a centimeter-scale Ag nanoparticle (AgNP) film (~20 cm × 20 cm) could be uniformly photo-deposited on both non-flexible and flexible TiO2 substrates, with a relative standard deviation in particle size of only 5.63%. The large-scale AgNP/TiO2 hybrids working as SERS substrates show high sensitivity and good uniformity at both the micron and wafer levels, as evidenced by scanning electron microscopy and Raman measurements. In situ bending and tensile experiments demonstrate that the as-prepared flexible AgNP/TiO2 SERS substrate is mechanically robust, exhibiting stable SERS activity even in a large bending state as well as after more than 200 tensile cycles. Moreover, the flexible AgNP/TiO2 SERS substrates show excellent performance in detecting sub-micrometer-sized plastics (≤1 μm) and low-concentration organic pollutants on complex surfaces. Overall, this study provides a simple path toward wafer-scale, flexible SERS substrate fabrication, which is a big step for practical applications of the SERS technique.

The Evolution of Illicit-Drug Detection: From Conventional Approaches to Cutting-Edge Immunosensors-A Comprehensive Review.

The increasing use of illicit drugs has become a major global concern. Illicit drugs interact with the brain and the body altering an individual's mood and behavior. As the substance-of-abuse (SOA) crisis continues to spread across the world, in order to reduce trafficking and unlawful activity, it is important to use point-of-care devices like biosensors. Currently, there are certain conventional detection methods, which include gas chromatography (GC), mass spectrometry (MS), surface ionization, surface-enhanced Raman spectroscopy (SERS), surface plasmon resonance (SPR), electrochemiluminescence (ECL), high-performance liquid chromatography (HPLC), etc., for the detection of abused drugs. These methods have the advantage of high accuracy and sensitivity but are generally laborious, expensive, and require trained operators, along with high sample requirements, and they are not suitable for on-site drug detection scenarios. As a result, there is an urgent need for point-of-care technologies for a variety of drugs that can replace conventional techniques, such as a biosensor, specifically an immunosensor. An immunosensor is an analytical device that integrates an antibody-based recognition element with a transducer to detect specific molecules (antigens). In an immunosensor, the highly selective antigen-antibody interaction is used to identify and quantify the target analyte. The binding event between the antibody and antigen is converted by the transducer into a measurable signal, such as electrical, optical, or electrochemical, which corresponds to the presence and concentration of the analyte in the sample. This paper provides a comprehensive overview of various illicit drugs, the conventional methods employed for their detection, and the advantages of immunosensors over conventional techniques. It highlights the critical need for on-site detection and explores emerging point-of-care testing methods. The paper also outlines future research goals in this field, emphasizing the potential of advanced technologies to enhance the accuracy, efficiency, and convenience of drug detection.

Lithium-doped ZrO2 nanoparticles for SERS-based norfloxacin drug detection

Surface-enhanced Raman scattering (SERS) spectroscopy is a highly specific and ultrasensitive analytical technique; thus, it is an ideal candidate for therapeutic drug monitoring. However, SERS measurements of drugs in a sample are inevitably affected by the environment. In this study, we synthesized ZrO2 nanoparticles (NPs) doped with the first group of elements (Li, Na, and K) in the main block and evaluated their SERS performance. The results showed that Li-ion doping could significantly enhance the SERS effect, and the degree of enhancement depended on the type and concentration of the doped ions. Compared with the highly stable ZrO2, Li ion-doped ZrO2 (Li-ZrO2) exhibited a significant increase in SERS activity. In particular, 1 % Li-ZrO2 NPs exhibited excellent SERS enhancement with an enhancement factor (EF) of 2.60 × 104, which was attributed to the decreased band gap and improved the charge transfer (CT) process after Li ion doping. The adsorption capacity of the Li-ZrO2 NPs for norfloxacin (NOR) molecules was gradually saturated with time. In addition, both acidic and alkaline conditions were unfavorable for NOR detection by the substrate. The SERS intensity exhibited a linear relationship within the NOR concentration range of 10−3–10–6 mol/L, and approximately 97.51 % of the active ingredients were detected, with a competitive detection limit of 10−6 mol/L. Furthermore, NOR detection is cost-effective and time-efficient, and the results of our study can aid in the research process and support practical applications. The proposed study provides a guidance for improving the SERS activity of semiconductors for sensing.

Effects of Cosolvent on the Intermolecular Interactions between an Analyte and a Gold Nanostar Surface Studied Using SERS.

For surface-enhanced Raman scattering (SERS), reproducible solution-phase results are typically obtained using nanoparticles functionalized with surface-stabilizing molecules that can prevent the adsorption of analyte molecules with surface affinities lower than those of the stabilizing agent. Herein, we investigate the effects of intermolecular interactions between a nonthiolated analyte and cosolvent to facilitate and modulate analyte adsorption to gold nanostars. SERS, extinction spectroscopy, transmission electron microscopy (TEM), and density functional theory (DFT) calculations are employed in this regard. Tetrahydrofuran (THF) is utilized as a cosolvent in water to facilitate the detection of acetylsalicylic acid (aspirin) on anisotropic gold nanoparticles. Intermolecular interactions between the analyte, solvent, and surface are modulated by changing the solution composition to understand how THF facilitates the SERS detection of aspirin in THF-water cosolvents. SERS signals for 5 mM aspirin arise only in the presence of THF at and above 60 mM, while no signal with or without THF below 60 mM is observed. SERS detection of aspirin is hypothesized to depend on THF forming a hydrogen-bonded complex with aspirin that reduces aspirin hydrophobicity, thus stabilizing the acid form of the molecule and allowing it to weakly interact with the gold nanoparticles. The aspirin-THF complex adsorbs to the gold surface through π-orbital overlap between the aromatic ring and gold, where additional THF weakens orbital overlap. Understanding the mechanism by which organic cosolvents facilitate the SERS detection of nonthiolated analytes such as aspirin, in aqueous media, allows other cosolvents, nonthiolated analytes, and other surfaces to obtain a SERS signal in a variety of systems.

Surfactant-Free Method to Prevent Gold Nanoparticle Aggregation and Its Surface-Enhanced Raman Scattering Applications.

The introduction of surfactants to stabilize colloidal citrate-reduced gold nanoparticles (prevent aggregation) is usually used in surface-enhanced Raman scattering (SERS) applications. However, the surfactants have many drawbacks for SERS applications, such as increasing the SERS background and blocking surface active sites. Here, we develop a surfactant-free method to stabilize colloidal cit-AuNPs based on alkali regulation, and this method can prevent gold nanoparticle aggregation under different harsh treatments, including ligand modification, centrifugation-based washing/enrichment, and salt addition. The SERS spectra, density functional theory simulation, and ζ potentials of cit-AuNPs indicate that the stability of enhanced cit-AuNPs under alkaline conditions is attributed to both the increased negative charge density (by ∼6 times from pH 7 to 12) and the molecular configuration on the metal surface. Compared with surfactant-based methods, this method can well maintain the inherent optical and interface properties of nanoparticles, avoid the SERS background, and avoid blocking of the surface active site due to the presence of surfactants. This method will enable AuNPs to have a wide range of applications in areas such as highly sensitive SERS sensors.

Study on the influence of material properties in femtosecond laser ablation of 6H-SiC in water and SERS-based applications

We report on the formation of SiC nanoparticles coated with graphene oxide layers by femtosecond (fs) laser ablation of 6H-SiC (n-type and semi-insulating V-doped) in deionized water. Distinct structural features were observed in the surrounding matrix of colloidal spherical nanoparticles. This corresponds to the formation of micro-nanostructures of silicene sheets in the colloidal suspension. Further, the formation of subwavelength (∼λ/8) high spatial frequency laser-induced periodic surface structures (HSFL) is noticed on the ablated SiC surface. The variation in the size and periodicity of LIPSS is noted among two SiC targets with different resistivities. The study continued to investigate the morphology of furnace annealed (FA) and rapid thermal annealed (RTA) Au-deposited LIPSS towards sensing applications based on the surface-enhanced Raman scattering (SERS) technique. The formation of fine spherical Au nanoparticles is observed in the case of RTA samples, which exhibited predominant SERS enhancement in trace detection of the explosive analyte, Tetryl. This study on SiC using fs laser pulses unveils the uniqueness of SiC material in the ablation process, especially in producing the LIPSS and silicon-carbon-based nanoparticles/nanostructures that can be tailored for diverse applications.

Raman-enhanced sensor based on CRISPR-SERS technology for the rapid and hypersensitive detection of Mycobacterium tuberculosis.

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 100pM. The equation describing the standard curve was y = 24.10x + 1594, with R2 = 0.9914. The limit of detection was as low as 4.42pM 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 50min 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.

Surface-Enhanced Raman Scattering Spectroscopy: An Effective Tool for the Detection of Environmental Pollutants

Surface-Enhanced Raman Scattering Spectroscopy: An Effective Tool for the Detection of Environmental Pollutants

B-117 Rapid Classification of Cleanliness Grades of Vaginal Discharge through Computational Analysis of SERS Spectra via Variational Auto-Encoder Model And Long Short-Term Memory Networks

Abstract Background Classification of cleanliness grades of vaginal discharge plays a pivotal role in clinical laboratories, serving as indicators for the presence of various vaginal infections such as bacterial vaginosis and candidal vulvovaginitis, etc. The conventional method for assessing vaginal discharge cleanliness involves manual microscopy, a technique susceptible to variations based on the examiner's expertise and subjective judgment, hindering the attainment of swift and accurate diagnoses. Methods This study introduces a novel approach by integrating Surface-Enhanced Raman Spectroscopy (SERS) with a deep learning algorithm for the rapid classification of vaginal discharge cleanliness grades. The proposed classification method combines the Variational Auto-Encoder (VAE) and Long Short-Term Memory (LSTM) to process SERS spectra. The quality of the training data is assessed using the signal-to-noise ratio (SNR) as a standard indicator. Results The application of the VAE-LSTM algorithm significantly enhances classification performance, providing swift and accurate results while reducing the required time. Comparative analyses with various classical machine learning algorithms and evaluation metrics reveal the superior predictive capability and time efficiency of the VAE-LSTM algorithm, demonstrating 100% accuracy and a fitting time of 2 seconds. Blind testing of SERS spectra collected from unknown patients further validates the reliability of the proposed method. Conclusions This study presents a promising and practical approach for the rapid classification of vaginal discharge cleanliness grades. The integration of the SERS technique with the VAE-LSTM algorithm not only ensures accuracy and efficiency in clinical diagnosis but also lays the foundation for advancements in non-invasive diagnostic technologies in gynecological healthcare.

Highly sensitive, reproducible, and stable core–shell MoN SERS substrate synthesized via sacrificial template method

Molybdenum nitride is a promising candidate for surface-enhanced Raman scattering (SERS) substrates due to its high conductivity, surface plasmon resonance, and chemical stability. Core-shell structures possess unique physical and chemical properties, such as high-volume ratio, low density, short diffusion length, and high load-bearing capacity, making them favorable for SERS applications. In this research, core–shell MoO3 is first synthesized as a precursor oxide using a sacrificial template method, and core–shell MoN microspheres are successfully prepared via subsequent nitriding. As a representative transition metal nitride, the obtained core–shell MoN nanospheres show strong localized surface plasmon resonance and SERS effects. Using these MoN microspheres as Raman substrates allows a range of highly targeted compounds to be accurately detected, and the detection limits for this non-precious-metal substrate morphology are exceptionally high, reaching 10−10 M. In addition, MoN nanospheres exhibit excellent resistance to acid–base corrosion, oxidation, and radiation, thus rendering them suitable for use as substrates in harsh environments.

Enhanced SERS detection of the colorectal cancer biomarker utilizing a two-dimensional silver substrate

To improve the sensitivity, accuracy and specificity of the assay, a two-dimensional silver substrate with EF=5.85×108 was first synthesized as a SERS substrate, on the surface of which DSP molecules were modified to form a DSP-antibody coupling through the activation of two N-hydroxy succinimide (NHS) esters to capture TNF-α. Subsequently, aptamerized silver-coated gold nanospheres (Au@TFMBA@Ag) were synthesized as Surface-Enhanced Raman Scattering (SERS) recognition probes. These probes were employed to create a sandwich structure for the quantitative detection of Tumor Necrosis Factor-alpha (TNF-α), utilizing the SERS signal intensity at 1374 cm−1. Quantitative detection of TNF-α was successfully accomplished within the concentration range of 10−4 to 10−10 mg·mL−1. Clinical serum samples were collected and subjected to testing. Significance analysis, conducted through the T-test (p < 0.0001), unequivocally showed the method's ability to differentiate between sera from normal individuals and those diagnosed with colon cancer.

Facile preparation of three-dimensional copper foam incorporated with Au/CuO nanorods as a durable, reusable and efficient SERS substrate

An exceptionally durable and recyclable three-dimensional copper foam (CF) modified CuO nanorods with Au nanostructures on its surface is noticeable for the application in surface-enhanced Raman scattering (SERS). The utilization of CF as a 3D frame substrate allowed for the advancement of its beneficial characteristics, such as an increased surface-active area resulting from its high porosity and superior chemical/physical stability. By thermally oxidizing CF at a temperature of 500 °C, CuO nanorods were fabricated directly onto CF to exploit its advantageous properties, such as its high surface-active area and photodegradation effect. Following that, Au nanostructures were deposited onto the surfaces of CuO nanorods via photoreduction. The purpose of incorporating Au nanostructures was to optimize the SERS phenomenon, since Au exhibits high SERS efficiency and excellent surface stability. The Au/CuO@CF SERS substrate demonstrated the capability to measure MB at a concentration of 0.1 nM. Meanwhile, the recyclability of the Au/CuO@CF was evaluated by subjecting it to UV irradiation three times while utilizing MB samples. Subsequently, the Au/CuO@CF substrate's physical durability was evaluated via sandpaper abrasion test. In addition to confirming the long-term usability, the Au/CuO@CF demonstrated its resilience by maintaining good measurement performance even after being subjected to ambient air for up to 25 days.

Versatile self-assembled near-infrared SERS nanoprobes for multidrug-resistant bacterial infection-specific surveillance and therapy

The rise of multidrug-resistant bacteria (MDRB) has made bacterial infection one of the biggest health threats, causing numerous antibiotics to fail. Real-time monitoring of bacterial disease treatment efficacy at the infection site is required. Herein, we report a versatile Raman tag 3,3′-diethylthiatricarbocyanine iodide (DTTC)-conjugated star-shaped Au-MoS2@hyaluronic acid (AMD@HA) nanocomposite as a surface-enhanced Raman scattering (SERS) nanoprobe for quick bacterial identification and in-situ eradication. Localized surface plasmon resonance (LSPR) from the hybrid metallic nanostructure makes AMD@HA highly responsive to the near-infrared laser, enabling it to demonstrate a photothermal (PTT) effect, increased SERS activity, and peroxidase-like catalytic reaction to release reactive oxygen species. The tail vein injection of AMD@HA nanoprobes is invasive, however SERS imaging for bacterial identification is non-invasive and sensitive, making it an efficient residual bacteria monitoring method. The detection limit for methicillin-resistant Staphylococcus aureus (MRSA) is as low as 102 CFU·mL-1, and the substrates allow for taking 120 s to acquire a Raman image of 1600 (40 × 40) pixels. In mouse models of MRSA-induced wound infection and skin abscess, the combination of AMD@HA-mediated PTT and catalytic therapy demonstrates a synergistic effect in promoting wound healing through rapid sterilization. This SERS-guided therapeutic approach exhibits little toxicity and does not cause considerable collateral damage, offering a highly promising intervention for treating diseases caused by MDRB. Statement of significanceThis research introduces a SERS nanoprobe, AMD@HA, for the rapid identification and eradication of multidrug-resistant bacteria (MDRB), a critical health threat. The nanoprobe leverages localized surface plasmon resonance for photothermal therapy and enhanced Raman signals, offering a sensitive, non-invasive diagnostic tool. With a low detection limit for MRSA and a synergistic therapeutic effect in mouse models, our approach holds significant promise for treating MDRB-driven infections with minimal toxicity, advancing the field of antimicrobial strategies.

Gold nanoparticles decorated crystalline carbon nitride nano-walls as a SERS chip for rapid and sensitive detection of benzidine

Risk level of benzidine residue to the environment and food safety urges surface enhanced Raman scattering (SERS) substrates to develop with high sensitivity and rapid enrichment. Herein, a hybrid of Au NPs decorated crystalline carbon nitride nano-walls (Au/CCN NWs) is fabricated on Al sheet and employed as a SERS substrate for the first time. An electro-enhanced adsorption strategy is employed to endow as-prepared Au/CCN NWs/Al chip with rapid assay capability. Crystalline phase transition and nano-wall morphology respectively bestows high charge transfer efficiency and favorable enrichment activity upon Au/CCN NWs/Al chip, and the hybrid substrate owns a considerable enhancement factor of 1.76×106 under static adsorption mode. Moreover, Au/CCN NWs/Al substrate can achieve the saturation enrichment of benzidine in 120 s with the help of electro-enhanced adsorption, and gains a significantly enhanced signal response compared to static adsorption. Likewise, the highly sensitive response (1 μg L-1), superior reproducibility (RSD=9.11 %, n=100) and reliable accuracy (recovery rate of 95.55%-109.46%) jointly demonstrate that Au/CCN NWs/Al substrate may be applicable for detecting benzidine residue in actual application. This work offers an integrated solution to both enhance charge transfer efficiency and enrichment activity based on collaborative crystalline phase transition and electro-enhanced adsorption, and may inspire the design of novel noble metal/semiconductor hybrid SERS substrates.

Effect of surface charge on laser-produced silver nanoparticles for dye reduction and surface-enhanced Raman spectroscopy

Silver nanoparticles (Ag NPs) are widely used in biological, chemical, and physical fields due to their distinct properties. However, the effect of surfactants with different polarities on the catalytic and surface-enhanced Raman spectroscopy (SERS) performance of Ag NPs has not been thoroughly studied. Here, we tailor the surface charge of laser-synthesized Ag NP without changing their morphology and investigate their catalytic and SERS capabilities. The surfactant-free silver nanoparticles (NPBare), synthesized via pulsed laser ablation in liquid (PLAL), are subsequently coated with ionic surfactants sodium dodecyl sulfate (NPSDS) and cetyltrimethylammonium bromide (NPCTAB). The synthesis and morphology of Ag NPs are confirmed using UV-Vis absorption spectroscopy and scanning electron microscopy. The surface charge of fabricated NPs is determined using zeta potential (ZP) measurements. The ZP values of NPBare, NPSDS, and NPCTAB are determined to be -17 mV, 28.7 mV, and 5.58 mV, respectively. The catalytic activity of bare and coated Ag NPs was tested against the cationic and anionic dyes, Methylene blue (MB) and Methyl orange (MO) respectively. The reduction rate of both dyes was highest when using NPBare. However, in the case of coated nanoparticles, the rate of MB and MO reduction depends on the difference between the ZP of the dye and nanoparticles: the rate of reduction increases with the difference between the zeta potentials of the dye and coated nanoparticles increases. The SERS capability of bare and coated NPs was evaluated for anionic (MO) and cationic (MB, Rhodamine B, and Crystal Violet) dyes. The SERS intensity of dyes strongly enhanced with the increase in ZP difference between the dye molecules and NPs. Surface charge modified NPs shown excellent SERS sensitivity with detection limit up to nanomolar for dye molecules as well as the homogeneity of NPs demonstrated in Raman mapping results with relative standard deviation of 17%. The results suggest that the electrostatic interaction between the nanoparticles and dye molecules plays a dominant role in SERS enhancement. These findings highlight the significance of surface charge in improving the catalytic and sensing properties of noble metal nanoparticles.

Rapid identification of milk powder adulteration based on surface-enhanced Raman spectroscopy

In recent years, milk powder adulteration has emerged as a matter of great concern. In this study, a rapid, accurate, and efficient detection method based on surface-enhanced Raman spectroscopy (SERS) combined with principal component analysis (PCA) was established to detect milk powder adulteration. The “coffee ring” effect-based gold nanoparticles (Au NPs) as the SERS-enhancing substrate were coupled with a portable Raman spectrometer, which enabled the differentiation of various brands of milk powder and the detection of melamine in milk powder. The substrate exhibited good SERS enhancement ability with an enhancement factor of 104. Furthermore, a strong linear correlation with a correlation coefficient (R2) of 0.9903 was observed between the melamine Raman intensity and concentration from 0.5 to 5.0 mg/kg. The calculated limit of detection of melamine (LOD) was 0.15 mg/kg, while the limit of quantitation (LOQ) was 0.5 mg/kg. In addition, when the method was applied to the detection of melamine in milk powder samples, this method achieved the recovery rates of melamine in milk powder samples ranged from 92.83% to 98.86% with relative standard deviations between 0.84% and 1.14%. In summary, the established method offers the advantages of cost-effectiveness, less sample requirement, and shorter detection time, meeting the needs for milk powder classification and rapid melamine detection.

Ball-in-hole 3D nanoarchitectonics based on nanoporous Au film: Ultrasensitive, highly reliable, and reusable plasmonic platform

Hotspots have a locally enhanced electromagnetic field, effectively created by nanogaps in plasmonic metal nanostructures. The formation of uniform nanogaps, smaller than a few nanometers, allows for the detection of analytes at low concentrations and ensures reliable measurements across entire surface-enhanced Raman scattering (SERS) substrates. Despite the demand for SERS substrates in recent optical sensing applications, challenges remain in developing new techniques to maximize the number and optimize the size of nanogaps on large-area substrates. To address this issue, this study introduces a new ball-in-hole technique based on metal nanoarchitecture utilizing 3D nanoporous gold film (NPGF) and 0D gold nanoparticles (AuNPs). Using the ball-in-hole technique, 23 nm AuNPs are placed within the ∼ 28 nm mesopores of the metal film, creating uniform nanogaps of just a few nanometers that ensure consistent SERS signals across a large substrate area due to effective hotspots. The 23nmNP@NPGF substrate exhibited an enhancement factor (EF) of 1014 for 4-aminophenol (4-ATP), enabling detection at the attomole level. Moreover, the substrate retained its performance after five washing and reuse cycles, demonstrating excellent recyclability Finally, the substrate successfully detected femtomolar concentrations of key neurotransmitters like dopamine and glutamate, without requiring Raman reporters. This study presents a promising strategy for constructing metal nanoarchitectures with numerous hotspots, offering new possibilities for developing more efficient SERS substrates.

Application of stealth nanobeacon for traceability assurance in pharmaceutical tablets via surface-enhanced Raman scattering during the tablet coating process

Microtaggant technologies for on-dose authentication have garnered significant interest for use in the anti-counterfeit activities and traceability of pharmaceutical dosage forms. Previously, we proposed a stealth nanobeacon (NB) comprising self-assembled colloidal gold nanoparticles with reporter molecules that demonstrated characteristic surface-enhanced Raman scattering (SERS) activity. However, the integration of such microtaggants into standard production lines remains underexplored. In this study, we demonstrate the incorporation of NB into tablet coatings using a simple mixing method with conventional coating solutions. Rapid and discernible SERS responses from the NB-coated tablets were observed in response to laser excitation at 785 nm for 0.1s, implying that it is an advanced and efficient method for counterfeit detection. In addition, the SERS intensity of NB increased with coating time, suggesting that NB can be used as a tracer for the real-time monitoring of coating thickness. Furthermore, NB-coated tablets were indistinguishable from NB-free tablets, even during colorimetric analysis. These results suggest that the NB possesses stealth properties and can be easily incorporated into counterfeit detection products.

Mid-level data fusion strategy based on urinary nucleosides SERS spectra and blood CEA levels for enhanced preoperative detection of lymph node metastasis in colorectal cancer

BackgroundPreoperative prediction of lymph node metastasis (LNM) plays a crucial role in the treatment and prognosis of colorectal cancer (CRC). The traditional histopathological examination is invasive and time-consuming, providing pathological features only postoperatively. Preoperative serum carcinoembryonic antigen (CEA) is strongly correlated with postoperative LN status. However, the detection accuracy of LNM based on a single preoperative CEA level is low. Therefore, developing a more powerful and sensitive diagnostic tool would be of great clinical value for improving the accurate preoperative prediction of LNM in CRC patients. ResultsThis study aimed to develop a mid-level fusion approach using urinary nucleosides Raman spectra and blood CEA data to enhance the preoperative discrimination of CRC patients with and without LNM. Surface-enhanced Raman scattering (SERS) spectra of urinary modified nucleosides, isolated by affinity chromatography, were first acquired from 48 patients with LNM and 49 patients without LNM. The principal component analysis (PCA) scores obtained from the SERS spectra were then combined with preoperative blood CEA values to create a fused data array. The discriminant accuracy based on either dataset alone or the fused data was evaluated using three machine learning algorithms: linear discriminant analysis, k-nearest neighbors, and support vector machine. Results showed that the fused data could discriminate between the two groups with an accuracy of up to 91 %, outperforming SERS alone (86 %) and CEA alone (69 %). SignificanceTo our knowledge, this is the first report of mid-level data fusion of urinary nucleosides SERS spectra with blood CEA levels for the preoperative prediction of LNM in CRC. This work demonstrates that the mid-level data fusion strategy aided by SVM algorithm can greatly improve the preoperative prediction accuracy of LNM. This is crucial for therapeutic decision-making and prognostic assessment in CRC.

Plasmonic image reproduction with solid-state superionic stamping (S4)

Traditional top-down approaches for producing metallic nanostructures, despite being capable of producing arbitrary 2-D shapes, often use vacuum-based deep sub-micron lithographic fabrication technologies. This makes their use for single-use devices like chemical and bio-sensing substrates difficult to economically justify. Here, the authors demonstrate a manufacturing pathway that only uses such techniques to produce a master. This reusable master, coupled with a unique and facile electrochemical imprinting process, Solid-State Superionic Stamping (S4), is used to produce several replicated metallic nanostructures, thus demonstrating an economically feasible manufacturing pathway for single-use, nano-enabled devices.This paper uses plasmonic image reproduction as an easy-to-visualize proxy for single-use devices such as plasmonic sensors and Surface Enhanced Raman Spectroscopy (SERS) substrates that require nanopatterned metallic structures. It demonstrates a process for replicating a picture by a set of metallic structures that plasmonically produce the desired colors locally. It uses a digitizing computational tool, direct-write Two-Photon Lithography (TPL) and a dry-etch process to rapidly produce a silicon master. This master is used to hot emboss nano-patterns in superionic glass blanks that, in turn, are used for electrochemical imprinting with S4 to reproduce the patterns on Ag substrates. The different steps in this process flow are described along with their role and effectiveness in contributing to a high-fidelity plasmonic image reproduction.