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Surface-enhanced Raman spectroscopy (SERS) is a powerful tool for elucidating the molecular makeup of materials. It possesses the unique characteristics of single-molecule sensitivity and extremely high specificity. However, the true potential of SERS, particularly in capturing the biochemical content of particles, remains underexplored. In this study, we harnessed transformer neural networks to interpret SERS spectra, aiming to discern the amino acid profiles within proteins. By training the network on the SERS profiles of 20 amino acids of human proteins, we explore the feasibility of predicting the predominant proteins within the µL-scale detection volume of SERS. Our results highlight a consistent alignment between the models predictions and the proteins known amino acid compositions, deepening our understanding of the inherent information contained within SERS spectra. For instance, the model achieved low root mean square error (RMSE) scores and minimal deviation in the prediction of amino acid compositions for proteins such as Bovine Serum Albumin (BSA), ACE2 protein, and CD63 antigen. This novel methodology offers a robust avenue not only for protein analytics but also sets a precedent for the broader realm of spectral analyses across diverse material categories. It represents a solid step forward to establishing SERS-based proteomics.

3D surface‐enhanced Raman scattering (SERS) platforms with multi‐dimensional hotspots and better tolerance to laser misfocus show great potential for the rapid detection of trace fentanyl. However, the complex fabrication process of 3D fine structures limits the wide‐ranging application of the SERS technique. Herein, a 3D SERS‐active platform is fabricated utilizing a scalable and cost‐effective strategy that involves the electroless deposition of dense Au nanoparticles on natural butterfly wing scales (b‐wings@Au). The resultant b‐wings@Au proves to be sensitive and reliable, with a lower limit of detection of 4× 10−12 m and an enhancement factor (EFexp) of 1.74 × 108 for fentanyl. Furthermore, it exhibits excellent reproducibility, as evidenced by a relative standard deviation of less than 5%, and also demonstrates outstanding stability. The obtained high EFexp is due to the combined effects of the electromagnetic mechanism, involving the enhanced electromagnetic field generated by 3D periodic hotspots, and the chemical mechanism, involving the charge transfer from fentanyl to Au surface. Additionally, the as‐prepared 3D substrate realizes the trace detection of nine fentanyl analogs. This study provides new ideas for the controllable construction of sensitive SERS platforms for drug detection, ultimately advancing the fields of 3D substrates in booming SERS‐based technologies. [ABSTRACT FROM AUTHOR]

Since the colorimetric method has the characteristics of being simple and low cost, the fluorescence spectrum has the characteristics of a strong signal, and Surface-enhanced Raman scattering (SERS) detection has the characteristics of high sensitivity and strong specificity, people usually use these three methods for detection, but the detection of a single sample takes more time. If multiple samples can be tested at the same time, the detection efficiency and sensitivity can be improved, and the selectivity and reliability will be greatly improved. Multiplex sensing also provides a new direction for researchers. To fully understand the research of multiplex sensing based on the plasmonic optics of noble metal nanostructures, this review summarizes all the results previously reported in this field. It also discusses the principles of various detection methods and the biochemical application of multiple detections and finally summarizes the challenges and prospects. [ABSTRACT FROM AUTHOR]

Surface enhanced Raman spectroscopy (SERS) by using gold nanoparticles (AuNPs) has gained relevance for the identification of biomolecules and some cancer cells. Searching for greener NPs synthesis alternatives, we evaluated the SERS properties of AuNPs produced by using different filamentous fungi. The AuNPs were synthesized utilizing the supernatant of Botrytis cinerea, Trichoderma atroviride, Trichoderma asperellum, Alternaria sp. and Ganoderma sessile. The AuNPs were characterized by ultraviolet–visible spectroscopy (UV–Vis) to identify its characteristic surface plasmon resonance, which was located at 545 nm (B. cinerea), 550 nm (T. atroviride), 540 nm (T. asperellum), 530 nm (Alternaria sp.), and 525 nm (G. sessile). Morphology, size and crystal structure were characterized through transmission electron microscopy (TEM); colloidal stability was assessed by Z-potential measurements. We found that, under specific incubation conditions, it was possible to obtain AuNPs with spherical and quasi-spherical shapes, which mean size range depends on the fungal species supernatant with 92.9 nm (B. cinerea), 24.7 nm (T. atroviride), 16.4 nm (T. asperellum), 9.5 nm (Alternaria sp.), and 13.6 nm (G. sessile). This, as it can be expected, has an effect on Raman amplification. A micro-Raman spectroscopy system operated at a wavelength of 532 nm was used for the evaluation of the SERS features of the AuNPs. We chose methylene blue as our target molecule since it has been widely used for such a purpose in the literature. Our results show that AuNPs synthesized with the supernatant of T. atroviride, T. asperellum and Alternaria sp. produce the stronger SERS effect, with enhancement factor (EF) of 20.9, 28.8 and 35.46, respectively. These results are promising and could serve as the base line for the development of biosensors through a facile, simple, and low-cost green alternative. [ABSTRACT FROM AUTHOR]

Metal aerogels (MAs) are emerging all‐nanometal‐structured self‐standing porous materials featuring exceptional performances in diverse fields. They have recently been adopted as 3D surface‐enhanced Raman scattering (SERS) substrates, while the less utilization of the unique porous structure leads to limited performance. Here, a fascinating compression‐mediated regulation strategy is presented to largely boost the SERS performance of Au–Ag aerogels. By gently pressing, both the density of hot spots and the inter‐ligament distance can be efficiently modulated, thus enabling to flexibly manipulate the SERS properties of MAs. On this basis, a record‐high misfocus tolerance (∼8.8 mm), low detection limit (down to 0.1 nM), high stability (>1 month), reusability, and multiplex detection ability are concurrently realized. This study may point out a new direction for engineering 3D SERS substrates with tunable and exceptional performance. [ABSTRACT FROM AUTHOR]

Rapid, in situ, and real‐time molecule mapping on rough surfaces with high accuracy has long been one of the paramount challenges in many fields. Here, an effortless Ag NPs doped glycerol liquid film SERS substrate (g‐LFS) is developed to investigate the distribution of contaminants on different types of rough surfaces. After substrate optimization, the g‐LFS is characterized in terms of uniformity, reproducibility, and stability with time. The substrate showed an excellent signal stability, even after 96.5 h of usage or 19 days of storage, together with great uniformity (7.4% RSD) and reproducibility (7.1% RSD). As a proof of concept, the distribution of Rhodamine 6G(R6G) dye on rough fabric and the R6G migration in different plant types and tissues have been explored. The g‐LFS substrate demonstrated great accuracy, detecting R6G even in deep fabric grooves, recovering 82.4% of the initial concentration. Moreover, the g‐LFS SERS substrate detected significantly different concentrations in root, stem and leave tissues of bean sprouts, as well as between xylem and phloem in vascular plant branches. Overall, the g‐LFS substrate is proven to be well‐suited for in situ detection on rough surfaces with great versatility and robustness, aggregating new opportunities for contaminant investigation on food and plants using SERS. [ABSTRACT FROM AUTHOR]

Gold nanostars have shown enormous potential as the main enablers of advanced applications ranging from biomedicine to sensing or catalysis. Their unique anisotropic structure featuring sharp spikes that grow from a central core offers enhanced optical capabilities and spectral tunability. Although several synthesis methods yield NSs of different morphologies and sizes up to several hundred nanometers, obtaining small NSs, while maintaining their plasmonic properties in the near-infrared, has proven challenging and elusive. Here, we show that Cu2+ addition during NS synthesis in polyvinylpyrrolidone/dimethylformamide generates more crystallographic defects and promotes the directional growth, giving rise to NSs with a larger number of much sharper spikes. They are also formed at smaller volumes, enabling the generation of ultrasmall nanostars, with a volume as small as 421 nm3 (i.e., 9.2 nm of volume-equivalent diameter), while maintaining a plasmon resonance in the near-infrared. To this end, we systematically evaluate the influence of synthesis parameters on the nanostar size and optical characteristics and demonstrate their properties for applications in catalysis, surface-enhanced Raman spectroscopy sensing, and hyperthermia. The ultrasmall nanostars show excellent attributes in all of them, leveraging their small size to enhance properties related to a higher surface-to-volume ratio or colloidal diffusivity. [ABSTRACT FROM AUTHOR]

Zirconium nitride (ZrN) nanoparticles (NPs) can offer appealing plasmonic properties for biomedical applications, but the synthesis of nontoxic, water-dispersible nanoformulations exhibiting plasmonic features in the biotransparency window presents a great challenge. Here, we report the synthesis, by methods of laser ablation, of small ZrN-based NPs, which are unique in combining photothermal heating and near-field enhancement in the transparency window. Depending on the synthesis environment, the formed ZrN-based NPs exhibit plasmonic absorption bands with maxima around 660–670 and 610–630 nm, which are largely red-shifted compared to what is expected from pure ZrN NPs. The observed shift is explained by the inclusion of zirconium oxide ZrOx (1 < x < 2) into NP composition and NP coating by naturally formed ZrOx. We then explored biophotonic applications of ZrN NPs. While pure NPs demonstrate their nontoxicity in vitro, their conjugation with anti-HER1 affibody ZHER1:1907 and subsequent photothermal heating with NIR-I laser cause 100% cancer cell death. In addition, profiting from the field enhancement, we demonstrate bioimaging functionality using a designed surface-enhanced Raman scattering probe based on an NP-conjugated azobenzene-CN-OH molecule as a Raman reporter. Combining a strong photothermal effect and the imaging option, laser-synthesized ZrN/ZrOx NPs promise a major advancement of theranostic modalities based on plasmonic nanomaterials. [ABSTRACT FROM AUTHOR]

Recent advancements in medical science have ushered in the era of "Personalized Medicine," which tailors treatments to individual genetics, lifestyle, and environmental factors. A cornerstone of this approach is continuous monitoring and adjustment of treatment regimens to optimize effectiveness while minimizing side effects. In therapeutic drug monitoring (TDM), crucial for drugs like doxorubicin (DOX) with severe side effects, traditional methods such as spectrofluorimetry and chromatography are utilized, but they suffer from cost and complexity issues. Biosensors, especially those leveraging Localized Surface Plasmon Resonance (LSPR) and surface-enhanced Raman spectroscopy (SERS), offer a promising alternative. This study focuses on developing a cost-effective plasmonic biosensor using gold nanoislands semiembedded in a glass substrate. The LSPR platform, based on gold nanoislands (Au NIs) with an average diameter of 23 nm, offers a rapid method for ultrasensitive, label-free detection of DOX in biological fluids up to the nanomolar range, even in diluted (1:10) and undiluted blood serum samples from cancer patients receiving the drug. The method capitalizes on the extraordinary adhesion between the nanoislands and the glass matrix, preserving plasmon integrity while enhancing the electric field surrounding the nanoislands for improved sensitivity. Moreover, by exploiting nanoislands with Au/Al2O3 core/shell structures with an average diameter and gap of about 70 and 7 nm, respectively, highly efficient SERS-active platforms are created, enabling the detection of ultralow DOX concentrations down to picomolar range, where the LSPR system is insensitive. The combined use of both systems enables the detection of DOX across a broad range, from low to high nanomolar concentrations, in biological fluids. This integration of semiembedded nanoislands presents a scalable and multifunctional approach suitable for point-of-care diagnostics, offering reproducible and stable characteristics over time. [ABSTRACT FROM AUTHOR]

DNA walker nanomachines are in fast development for biosensing, medical diagnostics, and food safety monitoring. For practical application, the issues of slow dynamics and low operational efficiency hinder its widespread application. Inspired by the high efficiency of agricultural cooperative machinery, a unique cleaving‐rolling‐assembly integrated nanodevice (CRAIN) is constructed for the high‐performance detection of various biomolecules. In the design, DNA nanotubes are introduced as building loaders to engineer polyoriented walking DNA nanorollers with blocked DNAzyme‐based walking strands and thus to increase the reaction direction and local concentration. Through target‐specific recognition, the activated nanorollers can autonomously and progressively cleave and roll along directional hairpin tracks on a gold substrate, significantly accelerating the reaction rate. Moreover, using nucleic acid‐encoded urchin‐shaped multispike gold‐silver composite nanospheres (nMGSs) as SERS‐enhanced probes, the engineered assembly of nMGSs probes induced by the cleaving‐rolling process promotes the formation of high‐density hotspot domains, further improving the detection sensitivity. With rational design, the CRAIN system can be extended to perform highly sensitive analyses of various analytes, such as microRNA‐21, butyrylcholinesterase activity and organophosphorus pesticides. This integrated assembly strategy can provide new perspectives for clinical diagnosis, biomedical engineering, and environmental science. [ABSTRACT FROM AUTHOR]

Surface-enhanced Raman scattering (SERS) remains a significant area of research since it's discovery 50 years ago. The surface-based technique has been used in a wide variety of fields, most prominently in chemical detection, cellular imaging and medical diagnostics, offering high sensitivity and specificity when probing and quantifying a chosen analyte or monitoring nanoparticle uptake and accumulation. However, despite its promise, SERS is mostly confined to academic laboratories and is not recognised as a gold standard analytical technique. This is due to the variations that are observed in SERS measurements, mainly caused by poorly characterised SERS substrates, lack of universal calibration methods and uncorrelated results. To convince the wider scientific community that SERS should be a routinely used analytical technique, the field is now focusing on methods that will increase the reproducibility of the SERS signals and how to validate the results with more well-established techniques. This review explores the difficulties experienced by SERS users, the methods adopted to reduce variation and suggestions of best practices and strategies that should be adopted if one is to achieve absolute quantification. [ABSTRACT FROM AUTHOR]

This work describes our recent PCB-based plasmonic nanostructured platform patent (US 11,828,747B2) for the detection of biomarkers in breast cancer serum (BCS). A 50 nm thin gold film (TGF) was immersion-coated on PCB (i.e., PCB-TGF) and immobilized covalently with gold nanourchin (GNU) via a 1,6-Hexanedithiol (HDT) linkage to produce a plasmonic activated nanostructured thin film (PANTF) platform. A label-free SERS immunosensor was fabricated by conjugating the platform with monoclonal HER-II antibodies (mAb) in a directional orientation via adipic acid dihydrazide (ADH) to provide higher accessibility to overexpressed HER-II biomarkers (i.e., 2+ (early), 3+ (locally advanced), and positive (meta) in BCS. An enhancement factor (EF) of 0.3 × 105 was achieved for PANTF using Rhodamine (R6G), and the morphology was studied by scanning electron microscopy (SEM) and atomic force microscope (AFM). UV-vis spectroscopy showed the peaks at 222, 231, and 213 nm corresponding to ADH, mAb, and HER-II biomarkers, respectively. The functionalization and conjugation were investigated by Fourier Transform Near Infrared (FT-NIR) where the most dominant overlapped spectra of 2+, 3+, and Pos correspond to OH-combination of carbohydrate, RNH2 1st overtone, and aromatic CH 1st overtone of mAb, respectively. SERS data were filtered using the filtfilt filter from scipy.signals, baseline corrected using the Improved Asymmetric Least Squares (isals) function from the pybaselines.Whittaker library. The results showed the common peaks at 867, 1312, 2894, 3026, and 3258 cm−1 corresponding to glycine, alanine ν (C-N-C) assigned to the symmetric C-N-C stretch mode; tryptophan and α helix; C-H antisymmetric and symmetric stretching; NH3+ in amino acids; and N-H stretch primary amide, respectively, with the intensity of Pos > 3+ > 2+. This trend is justifiable considering the stage of each sample. Principal Component Analysis (PCA) and Linear Discrimination Analysis (LDA) were employed for the statistical analysis of data. [ABSTRACT FROM AUTHOR]

Colorectal cancer remains a major global health concern. Colonoscopy, the gold-standard colorectal cancer diagnostic, relies on the visual detection of lesions and necessitates invasive biopsies for confirmation. Alternative diagnostic methods, based on nanomedicine, can facilitate early detection of malignancies. Here, we examine the uptake of surface-enhanced Raman scattering nanoparticles (SERS NPs) as a marker for intestinal tumor detection and imaging using an established Drosophila melanogaster model for gut disease. Young and old Oregon-R and w1118 flies were orally administered SERS NPs and scanned without and upon gut lumen clearance to assess nanoparticle retention as a function of aging. Neither young nor old flies showed significant NP retention in their body after gut lumen clearance. Moreover, tumorigenic flies of the esg-Gal4/UAS-RasV12 genotype were tested for SERS NP retention 2, 4 and 6 days after RasV12 oncogene induction in their midgut progenitor cells. Tumorigenic flies showed a statistically significant NP retention signal at 2 days, well before midgut epithelium impairment. The signal was then visualized in scans of dissected guts revealing areas of NP uptake in the posterior midgut region of high stem cell activity. [ABSTRACT FROM AUTHOR]

Aromatic amines are important commercial chemicals, but their carcinogenicity poses a threat to humans and other organisms, making their rapid quantitative detection increasingly urgent. Here, amorphous MoO3 (a‐MoO3) monolayers with localized surface plasmon resonance (LSPR) effect in the visible region are designed for the trace detection of carcinogenic aromatic amine molecules. The hot‐electron fast decay component of a‐MoO3 decreases from 301 fs to 150 fs after absorption with methyl orange (MO) molecules, indicating the plasmon‐induced hot‐electron transfer (PIHET) process from a‐MoO3 to MO. Therefore, a‐MoO3 monolayers present high SERS performance due to the synergistic effect of electromagnetic enhancement (EM) and PIHET, proposing the EM‐PIHET synergistic mechanism in a‐MoO3. In addition, a‐MoO3 possesses higher electron delocalization and electronic state density than crystal MoO3 (c‐MoO3), which is conducive to the PIHET. The limit of detection (LOD) for o‐aminoazotoluene (o‐AAT) is 10−9 M with good uniformity, acid resistance, and thermal stability. In this work, trace detection and identification of various carcinogenic aromatic amines based on a‐MoO3 monolayers is realized, which is of great significance for reducing cancer infection rates. [ABSTRACT FROM AUTHOR]

A series of non‐spherical metallic Au and bimetallic core@shell AuAg nanoparticles (NPs) have been synthesized for SERS improvements. The bimetallic core@shell AuAg NPs were obtained through a controlled overgrowth of an Ag shell onto the surface of two types of non‐spherical Au NPs, used as seeds, Au nanooctaheda (Au NOc) and Au nanotriangles (Au NTs). This Ag overgrowth was able to produce bimetallic core@shell structures such as nanocubes and nanopyramids, respectively. Transmission electron microscopy (TEM) was used to determine the particle size and particle morphology for metallic and bimetallic NPs, and energy‐dispersive X‐ray (EDX) elemental mapping analysis confirmed the core@shell structure of the bimetallic NPs. The plasmonic absorption bands exhibited for each nanosystem were observed by UV–vis spectroscopy. The concentration of Au and Ag in the bimetallic systems was determined by inductively coupled plasma mass spectrometry (ICP‐MS). After synthesis and characterization, p‐aminothiophenol (PATP) was used as a model analyte to investigate the surface‐enhanced Raman spectroscopy (SERS) capabilities of the synthesized metallic and bimetallic nanosystems. In PATP, a dimerization reaction to 4,4′‐dimercaptoazobenzene (DMAB) is produced when it is adsorbed onto the surface of certain noble metals. This SERS analysis was performed at 10−4 M of PATP and by using two different laser wavelengths (532 and 785 nm) in all cases. In this context, we were able to detect the dimerization reaction of PATP to DMAB only for the bimetallic structures and under the 532 nm laser line. Moreover, we have found that the dimerization capacity also depends on the nanoparticle morphology. [ABSTRACT FROM AUTHOR]

In order to investigate the adsorption process of malachite green (MG) on gold nanoparticles, a simple gold nanoparticles‐assembled film was prepared as a substrate of surface‐enhanced Raman spectroscopy (SERS), and it was soaked in MG solutions of different concentrations. The kinetic adsorption process was investigated by SERS method and density functional theoretical calculations. When saturated adsorption was achieved, the relationship between the characteristic SERS band signal intensity and the logarithm of solution concentration of MG was consistent with Temkin adsorption isotherm model, where the R2 value was greater than 0.995, and the linear range was 1 × 10−3–1 × 10−7 M. Finally, a SERS quantitative analysis model of the relationship between the adsorption properties of surface species and the bulk concentration was established. According to the electrostatic interaction and co‐adsorption, we proposed the surface adsorption configurations and adsorption process of MG on the nanostructured gold films. [ABSTRACT FROM AUTHOR]

The early monitoring and inactivation of bacteria are of crucial importance in preventing the further spread of foodborne pathogens. Staphylococcus aureus (S. aureus), a prototypical foodborne pathogen, is widely present in the natural environment and has the capability to trigger a range of diseases at low concentrations. In this work, we designed Fe3O4@SiO2-Au core–shell–satellite nanocomposites (NCs) modified with aptamer for efficient capture, high-sensitivity surface-enhanced Raman scattering (SERS) detection, and photothermal therapy (PTT) against S. aureus. Fe3O4@SiO2-Au NCs with tunable Au nanocrystal nanogaps were prepared. By combining the finite-difference time-domain (FDTD) method and experimental results, we studied the electric field distribution of Fe3O4@SiO2-Au under different Au nanogaps and ultimately obtained the optimal SERS substrate FSA-60. The modification of aptamer on the surfaces of FSA-60 could be used for the specific capture and selective detection of S. aureus, achieving a detection limit of as low as 50 cfu/mL. Furthermore, Apt-FSA-60 possessed excellent photothermal properties, demonstrating the strong photothermal killing ability against S. aureus. Therefore, Apt-FSA-60 is a promising high-sensitivity SERS substrate and efficient photothermal agent and is expected to be widely applied and promoted in future disease prevention and treatment. [ABSTRACT FROM AUTHOR]

Bacteriophages are emerging as a promising alternative in combating antibiotic-resistant bacteria amidst the escalating global antimicrobial resistance crisis. Recently, there has been a notable resurgence of interest in phages, prompting extensive research into their therapeutic potential. Beyond conventional microbiology and virology techniques, such as genomics and proteomics, novel phenotypic and chemical characterization methods are being explored. Among these, there is a growing interest in vibrational spectroscopy, especially in advanced modalities such as surface-enhanced Raman spectroscopy (SERS), tip-enhanced Raman spectroscopy (TERS), and atomic force microscopy-infrared spectroscopy (AFM-IR), which offer improved sensitivity and spatial resolution. This review explores the spectrum of uses of vibrational spectroscopy for bacteriophages, including its role in diagnostics, biosensing, phage detection, assistance in phage-based therapy, and advancing basic research. [ABSTRACT FROM AUTHOR]

The presence of copper ions (Cu2+) in excessive amounts can pose significant health risks. Therefore, the development of a rapid and highly sensitive technique for detecting even trace quantities of Cu2+ is of paramount importance. The proposed detection approach leverages the core-shell design of Au@Ag NPs functioning as the sensing substrate. The substrates were coupled with Raman probe molecules, namely, 4-mercaptobenzoic acid (4-MBA) and iodine ions (I−), resulting in the formation of the Au@Ag NPs-4-MBA-I− detection system. In this system, interactions between Cu2+ and I− took place, leading to the generation of I2, which in turn initiated the etching process of the Ag shell layer. Consequently, the thickness of the Ag shell decreased gradually. This reduction in the shell layer impaired the surface-enhanced Raman scattering (SERS) enhancement effect, causing a gradual decrease in the Raman signal intensity at 1586 cm−1 which was attributed to the characteristic peak of 4-MBA. Notably, a linear correlation existed between the thickness of the Ag shell and the intensity of the Raman signal. The proposed method for Cu2+ detection exhibits robust resistance to interference and high reproducibility under optimal SERS testing conditions. It boasted a wide linear detection range from 10−9 to 10−4 M and achieves a low detection limit (LOD) of 1.108 10−9 M. Moreover, this sensor was environmentally friendly, offered rapid recognition capabilities, and incurred minimal detection costs. Its versatility extended to diverse water systems, making it suitable for detecting Cu2+ not only in tap water but also in various other water sources. [ABSTRACT FROM AUTHOR]

Phthalate plasticizers (PAEs) illegally used in food pose a great threat to human health. A new and efficient sensing platform for the sensitive detection of the PAE residues in biological fluids needs to be designed and developed. Here, we report a simple and reliable surface-enhanced Raman spectroscopy (SERS) active platform with extralong hot spots of Au nanobipyramids@Ag nanorods (Au NBPs@Ag NRs) for the rapid and sensitive detection of PAEs in biological fluids. To achieve high activity, Au NBPs@Ag NRs with different shell lengths were fabricated by controlling the synthesis conditions, and the corresponding SERS properties were investigated by using crystal violet (CryV) and butyl benzyl phthalate (BBP). The experimental results showed that a longer shell length correlated to greater Raman activity, which was confirmed by finite-difference time-domain (FDTD) electromagnetic simulation. More importantly, the extralong hot spots of the Au NBPs@Ag NR SERS-active substrate showed excellent homogeneity and reproducibility for the CryV probe molecules (6.21%), and the detection limit was 10−9 M for both BBP and diethylhexyl phthalate (DEHP). Furthermore, through the standard addition method, an extralong hot spots SERS substrate could achieve highly sensitive detection of BBP and DEHP in serum and tears fluids, and the detection limit was as low as 3.52 × 10−8 M and 2.82 × 10−8 M. Therefore, the Au NBPs@Ag NR substrate with an extraordinarily long surface is efficient and versatile, and can potentially be used for high-efficiency sensing analysis in complex biological fluids. [ABSTRACT FROM AUTHOR]

Current label-free surface-enhanced Raman spectroscopy (SERS) assay for the detection and analysis of organophosphorus pesticides has achieved initial success, but the application still faces constraints of substrate portability and specificity. To this end, this paper demonstrates a method for portable, rapid, and specific detection of low concentrations of fenthion pesticides based on a solid substrate of gold nanoparticle monolayers combined with molecularly imprinted polymers (MIPs). The nano-monolayers were transferred to the surface of mercapto-silicon wafers by interfacial self-assembly technique to form a stable connection with S–Au bonds and, at the same time, prevent nanoparticles from dropping off during the surfactant removal process. Then, the fenthion MIPs were directly generated on the surface of the monolayer film by spin-coating with a pre-polymerization solution and ultraviolet-induced polymerization. Tests showed that the molecular imprint was able to accurately bind to fenthion, but not other molecules, in a mixture of structural analogs, achieving a low concentration detection of 10–8 mol/L. The composite substrate maintained a signal uniformity of a relative standard deviation (RSD) = 7.05% and a batch-to-batch reproducibility of RSD = 10.40%, making it a potential pathway for the extended application of SERS technology. [ABSTRACT FROM AUTHOR]

In surface-enhanced Raman scattering (SERS) detection research, the shape, structure, surface modification, and material selection of nanoparticles can significantly impact the SERS intensity. Petal-like gap-enhanced Raman tags (P-GERTs) possess numerous sharp tips and edges, which generate localized electric field enhancements, further amplifying the electric field enhancement effect on neighboring molecules and enhancing the SERS signal. Additionally, the surface of P-GERTs can be modified with functional molecules, enabling their application in the detection of disease biomarkers. Using COVID-19 as an example, the performance of P-GERTs in disease biomarker detection was validated, demonstrating that the signal intensity of this probe can reach 55 times that of regular gold nanoparticles and 36.7 times that of smooth shell gap-enhanced Raman tags (S-GERTs). Furthermore, in combination with magnetically retrievable magnetic bead substrates, the N-protein antigen was specifically detected in a one-step process. N-protein was detected within 15 min using a portable Raman spectrometer. The limit of detection (LOD) for the standard sample was 4.28 pg/mL, and the LOD for the actual throat swab sample system was 25.4 pg/mL. This workflow can be extended to the detection of other biomarkers, making it widely applicable. [ABSTRACT FROM AUTHOR]

Imaging of chemical composition in microfluidic chips is addressed using Surface Enhanced Raman Spectroscopy (SERS). The Y-shaped SERS microfluidic chip used is fabricated by xurography and an electrodeposition method is employed to form a thin nanostructured silver layer over the bottom glass wall of the main microchannel. Used as an immobilized SERS substrate, this layer of silver nanocrystals exhibits an analytical enhancement factor of 5.10 4 uniformly distributed over its surface (RSD < 7%). These good performances allow the quantitative imaging of transverse diffusion profiles of Crystal Violet (CV) at low concentrations ( 10 - 8 - 10 - 6 mol/L). The SERS measurement turns out to be reversible at high laser power and this is explained by the thermal desorption of adsorbed CV (photothermal effect). However, too high heating leads to a low amount of adsorbed species and a low SERS signal. This effect is limited by using a fast enough flow inducing a cooling effect. A compromise must be found between laser power and liquid flow rate to enable a reversible and sensitive SERS measurement in the chip. These findings should contribute to the development of imaging, in microfluidic conditions, of the spatiotemporal dynamics of weakly concentrated key molecules involved in chemical, biochemical or biological processes. [ABSTRACT FROM AUTHOR]

In this study, an efficient, homogeneous, flexible and transparent Ag/Polydimethylsiloxane (PDMS) substrate with an orderly three-dimensional nanopillar structure was proposed. Ag NPs were thermally deposited on the flexible bionic PDMS support obtained by a two-step replication of cicada wings. Scanning electron microscope images reveal when the deposition time was 50 min, Ag NPs of proper size densely covered the entire PDMS nanopillar surface in the Ag-50/PDMS substrate. Both the gaps between the Ag NPs and those between the nanopillars acted as efficient electric field amplifiers. The enhancement factor (EF) of the Ag-50/PDMS substrate was calculated to be 2.89 × 107 by using crystal violet as the probe molecule. The Ag-50/PDMS substrate also exhibited good uniformity and reproducibility with a relative standard deviation of 1.46% and 11.45% respectively. The detection capability of the proposed flexible and transparent Ag-50/PDMS substrate in practical applications was demonstrated by the in-situ detection of 0.1 ppm malachite green on fish surfaces, indicating its great potential in the field of food monitoring. [ABSTRACT FROM AUTHOR]

To date, the advanced synthetic approaches for palladium nanoparticle-based catalysts involve multistep, toxic, and high-cost fabrication routes with low catalytic and sensing performance. In this work, we introduce a new one-shot approach to produce highly sensitive Pd nanocomposites using a large-area polymer self-assembly strategy. This synthesis method allowed us to control the Pd nanoparticle shape and to tailor their plasmonic band positions in a wide light spectral range from ~350 to ~800 nm. We thus determined the critical synthesis conditions that give rise to a ringlike morphology in a reproducible manner. No need for a reducing agent and preliminary functionalization of the surface supporting the nanoparticles upon synthesis. To the best of our knowledge, few works have demonstrated the good performance of PdNPs in sensing. Here, we have demonstrated a robust SERS response for 4-mercaptopyridine with an enhancement factor of 4.2 × 105. We were able to exceed this high value, which matches the current maximum found in the literature, by decreasing the gap distances between Pd nanorings due to the high density of hotspots and the exacerbation of the coupling effect between PdNPs. These tailored products provide new insights for the use of Pd nanomaterials in photocatalysis applications, according to the well-established catalytic performance of Pd materials obtained in this work. [ABSTRACT FROM AUTHOR]

Plastics, of the order of microns in size, being not visible to the naked eye, are one of the significant contributors to pollution in the environment. Thus, the detection of micron-sized plastics (microplastics (MPs)) is crucial because of its hazardous toxic effects on our surroundings. In this work, we have proposed a quick and on-site detection of MPs, such as, polyvinyl chloride (PVC), polyvinyl alcohol (PVA) and polystyrene (PS) at ultra trace level using surface-enhanced Raman spectroscopy (SERS). To detect and analyse the spectra, two different nanostructures, such as, spherical shaped Ag nanoparticles (NPs), and shape anisotropic Ag nano-dendrites (NDs) were utilised to acquire the SERS spectra. A comprehensive analysis was further performed to check and investigate the amount of enhancements due to the mentioned nanostructures. We observed the Ag NDs exhibited amplified signal intensity compared to the Ag NPs due to the shape anisotropy leading to the surface charge confinement effect to create highly dense hotspots. However, the spherical shaped polystyrene beads of micron size exhibited better enhancement in Raman signal intensity when mixed with Ag NPs due to increased surface adsorption with the NPs. Therefore, the comparative study emphasizes the ability of using solution-based nanostructure as SERS for the onsite detection of microplastics having diverge size range at low concentration. [ABSTRACT FROM AUTHOR]

Over the past three decades, plasmonic nanostructures, particularly spherical ones, have seen remarkable advancements. Recently, attention has shifted toward anisotropic nanoparticles, especially star‐shaped/branched structures such as plasmonic nanostars (PNS), due to their distinct properties. PNS offers superior electromagnetic enhancement effects, larger surface areas, and as well as non‐linear and unusual photothermal properties, setting them apart from spherical counterparts. Despite significant progress in synthetic methods and characterization of the particles, challenges remain in transitioning PNS technology into practical use. In this perspective article, the distinctive attributes of PNS in biosensing applications are discussed, beginning with an exploration of synthesis methodologies. Their optoelectronic properties are examined and discussed how these properties influence their interaction with different molecules from a biosensing perspective. With a focus on PNS, detailed insights are offered into their unique properties, current applications, and future potential. By fostering discussion and understanding of PNS development, this article aims to facilitate the translation of PNS technology into practical applications, encouraging targeted improvements and advancements. [ABSTRACT FROM AUTHOR]

Plasmonic metal nanocrystals show great potential in surface-enhanced Raman spectroscopy (SERS) detection. However, the fabrication of metal substrates with uniform and dense hotspots for sensitive and reproducible SERS remains a challenge. This study demonstrates a steerable approach to prepare a monolayer composed of Au rough nanocubes (RNCs) derived from Au nanocubes (NCs), which exhibits efficient and reproducible SERS activity for detecting organic pollutants and pesticide residues. The structure-adjustable Au RNCs are prepared by growing Au nanoparticles on Au NCs via a PbS-assisted surface modification. The as-prepared Au RNCs show better SERS activity on detecting dye molecules compared to the initial Au NCs. This improvement is attributed to the dense hotspots generated by the plasmon coupling between the Au NCs and the Au nanoparticles. Subsequently, a uniform Au RNC monolayer is fabricated using an interfacial self-assembly method, thereby exhibiting further improved SERS activity due to the electromagnetic enhancement between the adjacent nanoparticles. The Au RNC monolayer has excellent signal reproducibility with a relative standard deviation of 4.13% on detecting crystal violet owing to the large-area and uniform hotspots. Additionally, the Au RNC monolayer demonstrates excellent SERS efficiency in detecting residual thiram on fruits (10-11 M, analytical enhancement factor of 1.24 × 108 at 1371 cm-1), melamine in milk, and dye in wastewater. These capabilities demonstrate the immense potential of the Au RNC monolayer for applications in food safety and environmental monitoring. [ABSTRACT FROM AUTHOR]

Benzene, a known toxic, carcinogenic, and pervasively present environmental pollutant, necessitates effective monitoring strategies to assess human exposure. S-Phenylmercapturic acid (S-PMA) is a specific biomarker for benzene exposure. This study presents a point-of-care testing (POCT) assay for the detection of S-PMA in human urine, integrating salt-induced phase separation (SIPS) with surface-enhanced Raman spectroscopy (SERS). S-PMA in human urine was first effectively separated using SIPS and then detected using a portable Raman spectrometer employing Au colloids as the SERS substrate. The POCT assay exhibited a clear correlation between the signal intensity and logarithmic concentration of S-PMA (0-5 ppm), demonstrating satisfactory recovery and reproducibility. Moreover, high-throughput fingerprint identification and quantitative analysis of S-PMA in urine were achieved within 10 min, with a detection limit as low as 1.06 ppb, by performing SIPS-SERS on 96-well plates. This POCT method holds promise for personal exposure assessment and may potentially aid in the prevention of benzene-induced diseases. [ABSTRACT FROM AUTHOR]

Nanoporous metallic films have attracted great attention as surface-enhanced Raman scattering (SERS) substrates. The presence of nanosized protrusions in such nanoporous metallic films gives rise to remarkably improved SERS enhancement due to an additional lightning rod effect of protrusions. However, the positive contribution of protrusions was only preliminarily demonstrated by SERS measurements so far, and several important questions remain unaddressedfundamental understanding into the near-field enhancement of protrusions, qualitative link between the measured SERS enhancement and properties of protrusions, and facile strategy for nanoporous metallic films with protrusions. In this paper, plasma oxidation-reduction of Ag nanofilms was used to fabricate various nanoporous Ag films with nanosized protrusions. The fundamental protrusion size dependence of near-field enhancement was elucidated from both the electrodynamic model and FDTD simulation, with the protrusion approximately treated as a hemiprolate spheroid positioned on a semi-infinite metallic base. With the as-fabricated nanoporous Ag films as the SERS substrates, the qualitative link between the measured SERS enhancement and density/size distribution of protrusions was established. The findings reported here contribute significantly to gaining deeper insight into the SERS enhancement of nanoporous metallic films and guiding future SERS substrate design. [ABSTRACT FROM AUTHOR]

Breast cancer is the most commonly diagnosed cancer in women globally and a leading cause of cancer-related mortality. However, current detection methods, such as X-rays, ultrasound, CT scans, MRI, and mammography, have their limitations. Recently, with the advancements in precision medicine and technologies like artificial intelligence, liquid biopsy, specifically utilizing Surface-Enhanced Raman Spectroscopy (SERS), has emerged as a promising approach to detect breast cancer. Liquid biopsy, as a minimally invasive technique, can provide a temporal reflection of breast cancer occurrence and progression, along with a spatial representation of overall tumor information. SERS has been extensively employed for biomarker detection, owing to its numerous advantages such as high sensitivity, minimal sample requirements, strong multi-detection ability, and controllable background interference. This paper presents a comprehensive review of the latest research on the application of SERS in the detection of breast cancer biomarkers, including exosomes, circulating tumor cells (CTCs), miRNA, proteins and others. The aim of this review is to provide valuable insights into the potential of SERS technology for early breast cancer diagnosis. [ABSTRACT FROM AUTHOR]

The development of a cost-effective and rapid assay technique for the identification of DNA methylation is one of the most crucial issues in the field of biomedical diagnosis because DNA methylation plays key roles in human health. The plasmonic crystal-based surface-enhanced Raman spectroscopy (SERS) technique is promising for the realization of such an assay method owing to its capability of generating uniformly enhanced electric fields to achieve high reproducibility and accuracy in SERS assays. However, the time and technical costs of fabricating plasmonic crystals are high, owing to the need for nanofabrication equipment. In this study, we developed nanoimprinted plasmonic crystals for cost-effective and rapid DNA methylation assays. Our plasmonic crystals identified methylated DNA with the 40-base pair adenomatous polyposis coli (APC) gene sequence, which is correlated with cell growth and cancer cells. [ABSTRACT FROM AUTHOR]

Surface-enhanced Raman spectroscopy (SERS) has emerged as a powerful technique for the detection and analysis of biomolecules due to its high sensitivity and selectivity. In recent years, SERS-based sensors have received significant attention for the detection of deoxyribonucleic acid (DNA) molecules, offering promising applications in fields such as medical diagnostics, forensic analysis, and environmental monitoring. This paper provides a concise overview of the principles, advancements, and potential of SERS-based sensors for DNA detection. First, the fundamental principles of SERS are introduced, highlighting its ability to enhance the Raman scattering signal by several orders of magnitude through the interaction between target molecules with metallic nanostructures. Then, the fabrication technologies of SERS substrates tailored for DNA detection are reviewed. The performances of SERS substrates previously reported for DNA detection are compared and analyzed in terms of the limit of detection (LOD) and enhancement factor (EF) in detail, with respect to the technical parameters of Raman spectroscopy (e.g., laser wavelength and power). Additionally, strategies for functionalizing the sensor surfaces with DNA-specific capture probes or aptamers are outlined. The collected data can be of help in selecting and optimizing the most suitable fabrication technology considering nucleotide sensing applications with Raman spectroscopy. [ABSTRACT FROM AUTHOR]

The excessive use of pesticides has detrimental effects on the ecosystem, leading to soil contamination and the spread of pollution beyond the targeted areas. Concerns arise regarding the permissible limits of pesticides, typically around 10−8 mol/L. In this study, we employed surface‐enhanced Raman spectroscopy (SERS), a highly sensitive and selective technique, to investigate the behavior of the pesticide ametrine (AMT) on silver colloids. The Ag nanoparticles (AgNPs) exhibited an average size of (26 ± 2) nm and a zeta potential of (−30 ± 1) mV in the absence of AMT, which decreased to (−24 ± 1) mV in the presence of AMT, resulting in mild AgNPs aggregation, with the average diameter of AgNPs increasing to approximately 300 nm. This aggregation is advantageous, as they provide active sites for pesticide detection. Besides, the purification method employed ensured that AMT remained undegraded, and various conformations of AMT were simulated using Ag clusters to study the SERS effect. Comparison with the experimental spectra indicated that the SERS‐4 conformer closely resembled the experimental spectrum, suggesting simultaneous interaction between the Ag surface and the sulfur (S) and nitrogen (N) atoms of the AMT triazine ring. Notably, changes in the AMT molecule were observed with pH variations: at pH below 5, hydroxylation occurred, resulting in an Ag–Cl stretching at 241 cm−1 in the SERS spectra. Conversely, at pH above 5 (pH 6–13), the presence of bands at 230 and 219 cm−1 in the SERS spectra indicate the formation of Ag–N and Ag–S bonds, respectively, between the AMT and the AgNPs. Furthermore, the study successfully detected AMT at pH 7, establishing a limit of detection (LOD) of 1.36 × 10−8 mol/L (3 ppb) based on the SERS spectra. These findings underscore the applicability of the SERS technique in the sensitive and selective detection of AMT, offering a promising approach for monitoring the presence of this pesticide in environmental samples. [ABSTRACT FROM AUTHOR]

Surface-enhanced Raman scattering (SERS) is a highly sensitive and non-destructive analytical technique that has attracted considerable interest in the scientific community. However, the practical application of SERS substrates has been hindered by the limited presence of active hotspots. In this study, we present an approach utilizing a TiO2 thin film decorated with Au nanoparticles (NPs) as a SERS platform. The Au/TiO2 hybrid thin film provides the sensor with exceptional sensitivity and remarkable photocatalytic properties for the photodecomposition of target molecules. Consequently, the optimized Au/TiO2 substrate exhibits a detection limit of 10–10 M for crystal violet (CV) molecules along with a significant enhancement factor of 1.94 × 108 and reliable repeatability. Additionally, it demonstrates a retention rate of 90% after three photodegradation cycles, highlighting its impressive reusability. Over a period of 45 days, the SERS intensity shows only a slight decrease of approximately 10%, underscoring its robust stability. The superior performance of our hybrid sample can be attributed to two primary benefits: the plasmonic effect of the Au NPs, which significantly enhances SERS sensitivity, and the charge-transfer (CT) effect, which enables facilitating efficient self-cleaning through the photocatalytic degradation of the TiO2 thin film under ultraviolet light exposure. This study not only offers insights into the synergistic effects of the electromagnetic enhancement and CT for recyclable SERS, but also opens up new avenues for studying photocatalysis involving dye molecules and monitoring catalytic processes. [ABSTRACT FROM AUTHOR]

Highly active Fe3O4/GO/Au composite nanomaterial was fabricated as a substrate of surface-enhanced Raman spectroscopy (SERS) and applied for pesticide residue detection. The three-layer multifunctional Fe3O4/GO/Au nanoparticles (NPs) were designed by facile method, with high hotspots, and were characterized by various techniques, including ultraviolet spectrophotometry (UV), X-ray diffraction (XRD), infrared absorption spectrometer (IR), and transmission electron microscopy (TEM). The performance of Fe3O4/GO/Au was evaluated by Raman spectroscopy with R6G as a probe molecule to verify its enhancement effect. It exhibited a strong Raman signal with 10−6 M of R6G. Furthermore, the presence of Fe3O4/GO/Au nanohybrid enabled the SERS-based method to detect mancozeb and showed an excellent linear relationship in the range of 0.25–25 ppm, with a low limit of detection (0.077 ppm), satisfactory EF, stability, and repeatability. In addition, the mechanism of SERS enhancement with electromagnetic mechanism (EM) and chemical mechanism (CM) was discussed in detail. Therefore, the proposed SERS approach holds promise as an auxiliary technique for screening contaminated agricultural products, environmental sample, and food in the future. [ABSTRACT FROM AUTHOR]

Surface-enhanced Raman scattering (SERS) exploits localized surface plasmon resonances in metallic nanostructures to significantly amplify Raman signals and perform ultrasensitive analyses. A critical factor for SERS-based analysis systems is the formation of numerous electromagnetic hot spots within the nanostructures, which represent regions with highly concentrated fields emerging from excited localized surface plasmons. These intense hotspot fields can amplify the Raman signal by several orders of magnitude, facilitating analyte detection at extremely low concentrations and highly sensitive molecular identification at the single-nanoparticle level. In this study, mesoscopic star-shaped gold particles (gold mesostars) were synthesized using a three-step seed-mediated growth approach coupled with the addition of silver ions. Our study confirms the successful synthesis of gold mesostars with numerous sharp tips via the multi-directional growth effect induced by the underpotential deposition of silver adatoms (AgUPD) onto the gold surfaces. The AgUPD process affects the nanocrystal growth kinetics of the noble metal and its morphological evolution, thereby leading to intricate nanostructures with high-index facets and protruding tips or branches. Mesoscopic gold particles with a distinctive star-like morphology featuring multiple sharp projections from the central core were synthesized by exploiting this phenomenon. Sharp tips of the gold mesostars facilitate intense localized electromagnetic fields, which result in strong SERS enhancements at the single-particle level. Electromagnetic fields can be further enhanced by interparticle hot spots in addition to the intraparticle local field enhancements when arranged in multilayered arrays on substrates, rendering these arrays as highly efficient SERS-active substrates with improved sensitivity. Evaluation using Raman-tagged analytes revealed a higher SERS signal intensity compared to that of individual mesostars because of interparticle hot spots enhancements. These substrates enabled analyte detection at a concentration of 10− 9 M, demonstrating their remarkable sensitivity for trace analysis applications. [ABSTRACT FROM AUTHOR]

Small molecule metabolites depict a biological system's status and help monitor disease conditions. Surface‐enhanced Raman scattering (SERS) holds considerable promise as an instant and non‐destructive detection tool for biological diagnosis. With single‐molecular sensitivity, molecular fingerprint and water compatible, SERS provides valuable information about chemical structures and analyte compositions, especially desirable in biological diagnosis. Design and fabrication of effective, stable SERS substrates can be one of the major research priorities to provide small‐molecule tracing with high sensitivity, selectivity, and reproducibility. Significant efforts have been directed towards creating high‐performance and multifunctional SERS substrates spanning from coinage metals to semiconductor materials. However, most SERS substrates are suffering from unsatisfied sensitivity for tracing small molecules such as volatile organic compounds (VOCs) and other biomarkers. This review summarized recent advances in SERS‐active substrates and their sensing for small biomarker molecules, especially VOCs in diagnosis. [ABSTRACT FROM AUTHOR]

Fentanyl and fentanyl analogs are the main cause of recent overdose deaths in the United States. The presence of fentanyl analogs in illicit drugs makes it difficult to estimate their potencies. This makes the detection and differentiation of fentanyl analogs critically significant. Surface-enhanced Raman spectroscopy (SERS) can differentiate structurally similar fentanyl analogs by yielding spectroscopic fingerprints for the detected molecules. In previous years, five fentanyl analogs, carfentanil, furanyl fentanyl, acetyl fentanyl, 4-fluoroisobutyryl fentanyl (4-FIBF), and cyclopropyl fentanyl (CPrF), gained popularity and were found in 76.4% of the fentanyl analogs trafficked. In this study, we focused on 4-FIBF, CPrF, and structurally similar fentanyl analogs. We developed methods to differentiate these fentanyl analogs using theoretical and experimental methods. To do this, a set of fentanyl analogs were examined using density functional theory (DFT) calculations. The DFT results obtained in this project permitted the assignment of spectral bands. These results were then compared with normal Raman and SERS techniques. Structurally similar fentanyl analogs show important differences in their spectra, and they have been visually differentiated from each other both theoretically and experimentally. Additional results using principal component analysis and soft independent modeling of class analogy show they can be distinguished using this technique. The limit of detection values for FIBF and CPrF were determined to be 0.35 ng/mL and 4.4 ng/mL, respectively, using SERS. Experimental results obtained in this project can be readily implemented in field applications and smaller laboratories, where inexpensive portable Raman spectrometers are often present and used in drug analysis. [ABSTRACT FROM AUTHOR]

Surface‐enhanced Raman scattering (SERS) is an ultrasensitive spectroscopic analysis technique widely used for molecule detection. However, manufacturing uniform, stable, and ultrasensitive substrates remains a challenge for the practical application of the SERS technology. Precious metals and semiconductors have been proved to be attractive and universal for SERS detection. In this work, a facile strategy is applied to prepare uniform three‐dimensional (3D) Ag@TiO2 nanostructures as SERS sensors. The Scanning electron microscopy and X‐ray photoelectron spectroscopy results indicate that silver nanoparticles are uniformly deposited into the pores of the TiO2 nanocavity arrays. The 3D hybrid substrate presents highly sensitive SERS signals of 4‐mercaptobenzoicacid (4‐MBA) with a detection limitation as low as 10−17 M. To prevent the oxidization of Ag and keep the activity of the film, a polymer mask was deposited on the SERS substrate and brought about excellent stability after weeks of reserving in air. In a nutshell, a SERS substrate with a high sensitivity and stability as well as good uniformity has been successfully developed in this work, which has a potential application for high‐precision SERS detection. [ABSTRACT FROM AUTHOR]

There has been increasing interest in the use of squaraines with different physicochemical properties. However, their applications in nanoplasmonics are limited. For that, detailed information on the interactions of squaraines with plasmonic nanostructures is required. In this work, we have studied the adsorption of the squaraine cis‐dicyanomethylene squarate (CDSQ) on the surface of Ag nanoparticles (AgNP). We have combined normal Raman, surface‐enhanced Raman scattering (SERS), and DFT calculations to get insights into the configuration of its adsorption. DFT calculations have been carried out using simplified models of different adsorption geometries for comparison with the results of the SERS experiments. A comparison between the relative intensities of the normal Raman and SERS spectra indicates that CDSQ is adsorbed perpendicular to the AgNP surface. The predicted spectra suggest that CDSQ is chemically adsorbed on the silver surface through one of its N atoms. [ABSTRACT FROM AUTHOR]

The limitations of conventional template‐based methods for the deposition of nanoparticle assemblies into defined patterns on solid substrates call for the development of techniques that do not require templates or lithographic masks. The use of optically‐induced thermal gradients to drive the migration of colloids toward or away from a laser spot, known as opto‐thermophoresis, has shown promise for the low‐power trapping and optical manipulation of a variety of colloidal species. However, the printing of colloids using this technique has so far not been established. Herein, a method for the optically directed printing of noble metal nanoparticles, specifically gold nanospheres is reported. The thermophoresis of the polymer polyvinylpyrrolidone and gold nanospheres toward a laser spot led to the deposition of nanoparticle aggregates, capable of serving as surface‐enhanced Raman scattering substrates. The influence of heating laser power and the concentrations of polymer, salt, and surfactant on the nanoparticle deposition rate and structure of the printed pattern are studied, showing that a variety of conditions can permit printing, suggesting facile generalization to different nanoparticle compositions, sizes, and shapes. These findings will greatly benefit future efforts for directed nanoparticle assembly, and drive applications in sensing, photothermal heating, and relevant applications in biomedicine and devices. [ABSTRACT FROM AUTHOR]

The engineering of a home-made portable double-layer filtration and concentration device with the common syringe for rapid analysis of water samples is reported. The core elements of the device were two installed filtration membranes with different pore sizes for respective functions. The upper filtration membrane was used for preliminary intercepting large interfering impurities (interception membrane), while the lower filtration membrane was used for collecting multiple target pathogens (enrichment membrane) for determination. This combination can make the contaminated environmental water, exemplified by surface water, filtrated quickly through the device and just retained the target bacteria of Escherichia coli O157:H7, Staphylococcus aureus, and Listeria monocytogenes on the lower enrichment membrane. Integrating with surface-enhanced Raman spectra (SERS) platform to decode the SERS-Tags (SERS-TagCVa, SERS-TagR6G, and SERS-TagMB) already labeled on each of the enriched bacteria based the antibody-mediated immuno-recognition effect, fast separation, concentration, and detection of multiple pathogenic bacteria from the bulk of contaminated environmental water were realized. Results show that within 30 min, all target bacteria in the lake water can be simultaneously and accurately measured in the range from 101 to 106 CFU mL−1 with detection limit of 10.0 CFU mL−1 without any pre-culture procedures. This work highlights the simplicity, rapidness, cheapness, selectivity, and the robustness of the constructed method for simultaneous detecting multiple pathogens in aqueous samples. This protocol opens a new avenue for facilitating the development of versatile analytical tools for drinking water and food safety monitoring in underdeveloped or developing countries. [ABSTRACT FROM AUTHOR]

Raman spectroscopy (RS) is a nondestructive analytical method extensively utilized in the field of biomedical, and pharmaceutical applications due to their high sensitivity, noninvasive, and selective interaction with biomolecules. This method is significantly used in clinical diagnosis in both in vitro and in vivo to observe the structural and morphological changes in the biological fluids. In this review, we focused on the pharmaceutical and medical importance of surface-enhanced Raman spectroscopy (SERS). The review explores the applications of RS in drug manufacturing and process control, drug quality, and the discussion, including the capabilities of RS in cancer treatment, and in vivo applications. Finally, we discussed the modern Raman devices and future perspectives. Even though the summarized studies provide interesting and useful information about RS for pharmaceutical and biomedical field researchers, we expect that a collaborative approach between academicians and scientists from various disciplines and healthcare professionals will produce additional fundamental insights into RS-based applications shortly. [ABSTRACT FROM AUTHOR]

Sulfide organics and phenols are ubiquitous in freshwater lakes all over the world. As two taste and odor (T and O) compounds, they are harmful to the environment and human body. The existing detection methods for T and O compounds mainly include sensory analysis and gas-phase mass spectrometry, which are cumbersome and time-consuming. Herein, a method for the simultaneous and rapid detection of two T and O compounds (methyl sulfide and 2,4-di-tert-butylphenol) based on surface-enhanced Raman spectroscopy (SERS) is firstly developed. The SERS substrate was prepared by coating Ag nanoparticles (Ag NPs), layered double hydroxide (LDH), and graphene oxide (GO) on the surface of an Ag-coated Au nanoparticle (Au@Ag NP) substrate. Under optimal conditions, this SERS substrate possessed low detection limits of 1.53 ppm for methyl sulfide and 0.39 ppm for 2,4-di-tert-butylphenol. In addition, it took only 20 min to complete the detection using this method, without complex sample pretreatment. Furthermore, it was successfully applied to simultaneously detect methyl sulfide and 2,4-di-tert-butylphenol in actual water samples and had good application prospects for the rapid detection of T and O compounds in water. [ABSTRACT FROM AUTHOR]

The present study investigates the effects of input wavelength (1064, 532, and 355 nm) and surrounding liquid environment (distilled water and aqueous NaCl solution) on the picosecond laser ablation on silver (Ag), gold (Au), and Ag/Au alloy targets. The efficacy of the laser ablation technique was meticulously evaluated by analyzing the ablation rates, surface plasmon resonance peak positions, and particle size distributions of the obtained colloids. The nanoparticles (NPs) were characterized using the techniques of UV–visible absorption, transmission electron microscopy, and energy-dispersive X-ray spectroscopy. Furthermore, NPs of various sizes ranging from 6 to 35 nm were loaded onto a filter paper by a simple and effective drop-casting approach to achieve flexible surface-enhanced Raman spectroscopy (SERS) substrates/sensors. These substrates were tested using a simple, portable Raman device to identify various hazardous chemicals (malachite green, methyl salicylate, and thiram). The stability of the substrates was also systematically investigated by determining the decay percentages in the SERS signals over 60 days. The optimized SERS substrate was subsequently employed to detect chemical warfare agent (CWA) simulants such as methyl salicylate (a CWA simulant for sulfur mustard) and dimethyl methyl phosphonate (has some structural similarities to the G-series nerve agents) at different laser excitations (325, 532, and 633 nm). A notably higher SERS efficiency for CWA simulants was observed at a 325 nm Raman excitation. Our findings reveal that a higher ablation yield was observed at IR irradiation than those obtained at the other wavelengths. A size decrease of the NPs was noticed by changing the liquid environment to an electrolyte. These findings have significant implications for developing more efficient and stable SERS substrates for chemical detection applications.

Abstract Surface-enhanced Raman scattering (SERS) remains a significant area of research since it’s discovery 50 years ago. The surface-based technique has been used in a wide variety of fields, most prominently in chemical detection, cellular imaging and medical diagnostics, offering high sensitivity and specificity when probing and quantifying a chosen analyte or monitoring nanoparticle uptake and accumulation. However, despite its promise, SERS is mostly confined to academic laboratories and is not recognised as a gold standard analytical technique. This is due to the variations that are observed in SERS measurements, mainly caused by poorly characterised SERS substrates, lack of universal calibration methods and uncorrelated results. To convince the wider scientific community that SERS should be a routinely used analytical technique, the field is now focusing on methods that will increase the reproducibility of the SERS signals and how to validate the results with more well-established techniques. This review explores the difficulties experienced by SERS users, the methods adopted to reduce variation and suggestions of best practices and strategies that should be adopted if one is to achieve absolute quantification. Graphical Abstract

Abstract Surface-enhanced Raman scattering (SERS) exploits localized surface plasmon resonances in metallic nanostructures to significantly amplify Raman signals and perform ultrasensitive analyses. A critical factor for SERS-based analysis systems is the formation of numerous electromagnetic hot spots within the nanostructures, which represent regions with highly concentrated fields emerging from excited localized surface plasmons. These intense hotspot fields can amplify the Raman signal by several orders of magnitude, facilitating analyte detection at extremely low concentrations and highly sensitive molecular identification at the single-nanoparticle level. In this study, mesoscopic star-shaped gold particles (gold mesostars) were synthesized using a three-step seed-mediated growth approach coupled with the addition of silver ions. Our study confirms the successful synthesis of gold mesostars with numerous sharp tips via the multi-directional growth effect induced by the underpotential deposition of silver adatoms (AgUPD) onto the gold surfaces. The AgUPD process affects the nanocrystal growth kinetics of the noble metal and its morphological evolution, thereby leading to intricate nanostructures with high-index facets and protruding tips or branches. Mesoscopic gold particles with a distinctive star-like morphology featuring multiple sharp projections from the central core were synthesized by exploiting this phenomenon. Sharp tips of the gold mesostars facilitate intense localized electromagnetic fields, which result in strong SERS enhancements at the single-particle level. Electromagnetic fields can be further enhanced by interparticle hot spots in addition to the intraparticle local field enhancements when arranged in multilayered arrays on substrates, rendering these arrays as highly efficient SERS-active substrates with improved sensitivity. Evaluation using Raman-tagged analytes revealed a higher SERS signal intensity compared to that of individual mesostars because of interparticle hot spots enhancements. These substrates enabled analyte detection at a concentration of 10− 9 M, demonstrating their remarkable sensitivity for trace analysis applications.