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In this study, we propose a novel surface-enhanced Raman scattering (SERS) method for quantifying aflatoxin B1 (AFB1). This method relies on the target-triggered release of a SERS reporter from aptamer-sealed aminated mesoporous silica nanoparticles (MSNs). These MSNs were synthesized to accommodate 4-mercaptophenylboronic acid (4-MPBA) within their well-defined micropores, which were subsequently sealed with AFB1 aptamers. Upon specific binding of AFB1 to its aptamer, the conformational change in the aptamer is regulated by the presence of the target. Consequently, a positive linear relationship between the AFB1 concentration and the 4-MPBA SERS signal was observed. Under optimal conditions, the method exhibited a good linear relationship over the range of 0.1 to 5 ng/mL AFB1, with a limit of detection (LOD) of 0.03 ng/mL. This strategy was validated using wheat samples, yielding results comparable to high performance liquid chromatography-fluorescence detector (P > 0.05), confirming its reliability for detecting AFB1 in complex food matrices. • A target-triggered release of reporter from mesoporous silica nanoparticles (MSNs) strategy was proposed. • MSNs were synthesized to accommodate the reporter within well-defined micropores. • Under optimized conditions, a limit of detection (LOD) of 0.03 ng/mL was achieved. • The platform offered precise detection of AFB1 in food and environmental settings. [ABSTRACT FROM AUTHOR]

The overuse of pesticides results in excessive pesticide residues, posing a potential threat to human health. Herein, this work proposes a SERS substrate for the quantitative analysis of pesticide residues on food surfaces. Au cores are assembled on PS microspheres, followed by the modification of Raman internal standards (1,4-BDT) on the gold core surface and the growth of the Au shell. After incubating the analytes with PS@Au@1,4-BDT@Au particles, the mixture is dropped on the hydrophobic gold film for drying before detection. The SERS substrates exhibited high sensitivity and stability, with a detection limit of 10−12 M and an RSD of less than 7 %. Combined with a portable Raman spectrometer, the SERS detection of pesticide residues on three kinds of food surfaces is carried out, with a sensitivity of 10−11 M, meeting the US MRLs regulations. Therefore, this strategy may possess significant potential for future food safety. • PS@Core-shell particle fabricates 3D hot spots on the hydrophobic interface. • Raman Internal standard provides a reference for quantitative SERS detection. • The hydrophobic film attenuates the "coffee ring" effect of solvent evaporation. [ABSTRACT FROM AUTHOR]

[Display omitted] • A sensitive and rapid detection of maleic hydrazide (MH) based on a self-constructed hydrogel SERS platform is proposed for the first time. • The high sensitivity, fast response, and high selectivity are realized by the electromagnetic enhancement effect and hydrogel structure. • The strategy shows satisfactory results for quantitative detection of MH in tea and potato. Maleic hydrazide (MH) is a commonly used plant growth regulator and herbicide. However, due to its potential mutagenicity, carcinogenicity, genotoxicity, and cytotoxicity, sensitive and rapid detection of MH residues in foods is crucial. Herein, a sensitive and reliable surface-enhanced Raman scattering (SERS) sensor for MH based on a self-constructed hydrogel SERS platform is proposed for the first time. The used hydrogel SERS chips contain aggregated Ag nanoparticles (a-AgNPs). Under the irradiation of 785 nm laser, the a-AgNPs provide a large quantity of plasmonic hots to produce strong electromagnetic enhancement. Thus, strong SERS signal of MH can be gained on the hydrogel SERS platform. In addition, the unique network structure of hydrogel greatly improves the anti-interference ability to the complex sample matrix. As a result, the developed SERS sensor for MH shows the advantages of high sensitivity (a low detection limit of 50 ppb), fast response (10 min), and high selectivity. The reliability of the sensor is supported by the satisfactory recoveries of 92.80 – 105.6 % in actual samples (tea and potato). The constructed SERS sensor provides a promising approach for rapid on-site testing of MH residues. [ABSTRACT FROM AUTHOR]

• Developing a batch fabrication scheme of tapered fiber SERS probes with excellent interchangeability. • Proposing and demonstrating a spectral data assimilated method. • Obtaining a high-precision calibrated SERS quantitative relationship curve. • Achieving excellent test recovery rate in SERS quantitative detection. The tapered fiber Surface-enhanced Raman scattering (SERS) probe is a highly sensitive SERS substrate for on-site detection. However, fiber probes prepared by the current technology lack interchangeability and are difficult to meet the practical quantitative detection demands. In this paper, we develop a batch preparation technology of tapered fiber SERS probes, with good interchangeability between each of the 20 tapered fiber SERS probes prepared in batches. Furthermore, we propose and demonstrate a spectral data assimilation method, through which the differences in interchangeability between different batches can be eliminated. Using 10 batches of spectral data assimilated with this method, we obtain a high-precision calibrated quantitative relationship curve with a fitting degree of 0.99464, with recovery rates of the two thiram spiked samples 106.88% and 95.75%, respectively. The batch preparation technology and the spectral data processing method provide a new option for practical quantitative detection. [ABSTRACT FROM AUTHOR]

Nanoplastics present a significant hazard to both the environment and human health. However, the development of rapid and sensitive analysis techniques for nanoplastics is limited by their small size, lack of specificity, and low concentrations. In this study, a surface-enhanced Raman scattering (SERS) chessboard substrate was introduced as a multi-channel platform for the pre-concentration and detection of nanoplastics, achieved by polydomain aggregating silver nanoparticles (PASN) on a hydrophilic and a punched hydrophobic PVDF combined filter membrane. Through a straightforward suction filtration process, nanoplastics were captured by the PASN gap in a single step for subsequent SERS detection, while excess moisture was promptly eliminated from the filter membrane. The PASN-based SERS chessboard substrate, benefiting from the enhanced electromagnetic (EM) field, effectively discriminated polystyrene (PS) nanoplastics ranging in size from 30 nm to 1000 nm. Furthermore, this substrate demonstrated favorable repeatability (RSD of 8.6 %), high sensitivity with a detection limit of 0.001 mg/mL for 100 nm of PS nanoplastics, and broad linear detection ranges spanning from 0.001 to 0.5 mg/mL (R2 = 0.9916). Additionally, the SERS chessboard substrate enabled quantitative analysis of nanoplastics spiked in tap and lake water samples. Notably, the entire pre-concentration and detection procedure required only 3 μL of sample and could be completed within 1 min. With the accessibility of portable detection instruments and the ability to prepare substrates on demand, the PASN-based SERS chessboard substrate is anticipated to facilitate the establishment of a comprehensive global nanoplastics map. [Display omitted] • A portable SERS chessboard substrate with pre-concentration and detection capability for analysis of nanoplastics. • Utilization of various sizes of Ag nanoparticles to expand hotspot areas. • High sensitivity detection at concentrations as low as 0.001 mg/mL with 3 μL of sample within 1 min for 100 nm PS nanoplastics. • Efficient and quick production of this SERS substrate as needed, requiring only 10 μL of Ag NPs. [ABSTRACT FROM AUTHOR]

[Display omitted] • Plasmonic nanoparticles show significant potential as photocatalysts. • Ag nanorods exhibit prominent photoconversion under 633 nm laser compared to Au nanorods. • FDTD simulations reveal stronger electromagnetic fields in Ag nanorods. • Ag nanorod dimers with specific configurations achieve high SERS enhancement factors. Plasmonic nanoparticles (NPs) hold considerable potential as photocatalysts owing to their robust light–matter interactions across diverse electromagnetic wavelengths, which significantly influence the photophysical characteristics of the adjacent molecular entities. Despite the widespread use of noble-metal NPs in surface-enhanced Raman scattering (SERS) applications, little is known about the kinetics of nanoparticle aggregation and how it affects their configurations. This study investigates the plasmon-driven photochemical conversion of 4-nitrobenzenethiol (NBT) to 4,4′-dimercaptoazobenzene (DMAB) on Au and Ag nanorods (NRs) through SERS. Significantly, photoconversion phenomena were observed on Ag NRs but not on Au NRs upon laser excitation at 633 nm. Finite-difference time-domain simulations revealed the presence of stronger electromagnetic fields on Ag NRs than on Au NRs. The aspect ratios and gaps between individual NPs in dimer configurations were determined to elucidate their effects on electromagnetic fields. The Ag NR dimer with an end-to-end configuration, an aspect ratio of 3.3, and a 1-nm gap exhibited the highest enhancement factor of 1.05 × 1012. Our results demonstrate that the primary contribution from diverse configurations in NR aggregates is the end-to-end configuration. The proposed NP design with adjustable parameters is expected to advance research in plasmonics, sensing, and wireless communications. These findings also contribute to the understanding of plasmon-driven photochemical processes in metallic nanostructures. [ABSTRACT FROM AUTHOR]

Microorganisms assigned as Cronobacter are Gram-negative, facultatively anaerobic, bacteria widely distributed in nature, home environments, and hospitals. They can also be detected in foods, milk powder, and powdered infant formula (PIF). Additionally, as an opportunistic pathogen, Cronobacter may cause serious infections, sometimes leading to the death of neonates and infants. Thus, it is essential to test food products for the presence of Cronobacter spp. The currently used standard described in ISO 22964:2017 is a laborious method that could be easily replaced by surface-enhanced Raman scattering (SERS). Here, we demonstrate that SERS allows the identification of food-borne bacteria belonging to Cronobacter spp. based on their SERS spectra. For this purpose, twenty-six Cronobacter strains from different food samples were analyzed. Additionally, it was shown that it is possible to differentiate them from other closely related pathogens such as Salmonella enterica subsp. enterica , Escherichia coli , or Enterobacter spp. The SERS results were supported by principal component analysis (PCA), as well as and sequencing of 16S rRNA , rpoB and fusA genes. Last but not least, it was demonstrated that the cells of Cronobacter sakazakii may be easily separated from PIF using an appropriate filter, microfluidic chip, and dielectrophoresis (DEP) technique. • The sensitive, non-invasive, rapid, and cost-effective practical prototype applicable in food analysis. • The SERS studies of 52 strains belonging to four genera (Cronobacter, Enterobacter, Salmonella, Escherichia). • SERS-DEP in microfluidic system-based technique for identification of bacterial species at genus and species levels. • PCA enabled the separation of SERS spectra with an accuracy of up to 98 %. • The low concentration detecting and identifying C. sakazakii in real food samples. [ABSTRACT FROM AUTHOR]

Rapid and selective separation, enrichment and detection of trace residue all-in-one in complex samples is a major challenge. Hydrogels with molecular sieve properties can selectively separate and enrich target analytes, and the combination with high sensitivity detection of surface-enhanced Raman scattering (SERS) is expected to achieve the above all-in-one detection. Herein, the core-shell structured Au@poly(N-isopropylacrylamide)-phenylboronic acid hydrogel (Au@PNIP-VBA) with boronic acid ester groups was prepared by thermally initiated polymerization. The boronic acid ester groups in hydrogel are selectively hydrolyzed by hydrogen peroxide (H 2 O 2) to hydroxyl structures, leading to a reduction in SERS signals. The Au@PNIP-VBA hydrogel has molecular sieve properties and high SERS activity, making it suitable for separation, enrichment, hydrolysis and detection of H 2 O 2 all-in-one. A rapid SERS method was developed for analysis of H 2 O 2 based on the Au@PNIP-VBA hydrogel with the linear range of 8.5 × 10−2-6.8 mg L−1 and the detection limit of 33 μg L−1. The method was successfully applied to the determination of H 2 O 2 residue in fresh milk, pure milk, yogurt and camel milk, with the recoveries were in the range of 82.2%–109.3% and the relative standard deviations were 2.8%–8.3%. This efficient all-in-one strategy has the advantages of simple sample pre-treatment, rapid analysis (30 min) and high sensitivity, making it highly promising for food quality and safety analysis. The core-shell structured Au@PNIP-VBA hydrogel with boronic acid ester group was prepared with high SERS activity and molecular sieves properties, which was used effective separation, enrichment, selective hydrolysis and rapid detection of hydrogen peroxide residue in dairy products all-in-one. [Display omitted] • A novel core-shell structured hydrogel SERS substrate (Au@PNIP-VBA) fabricated. • The hydrogel for separation, enrichment, hydrolysis and detection of H 2 O 2 all-in-one. • A SERS method for analysis of H 2 O 2 by Au@PNIP-VBA hydrogel developed. • The SERS method applied for rapid detection of H 2 O 2 residue in dairy products. [ABSTRACT FROM AUTHOR]

• A bottom-up "sandwich" configuration substrate was designed via electrostatic self-assembly. Ag microplate (AgMP) is as a stable structural substrate, followed by wet transferred Graphene and liquid-liquid three-phase self-assembly is used to transfer the Au@Ag nanocubes (Au@Ag NCs) group on the upper layer, forming a core-shell structured Au@AgNCs/G/AgMP substrate. • The electromagnetic enhancement generated by noble metal nanoparticles and the chemical enhancement brought by graphene work together on the detected molecules, resulting in excellent Raman activity of the fabricated substate. The results showed that the substrate could detect the Rhodamine 6G (R6G, 10–12 M) and the Crystal violet (CV, 10–9 M) at a low concentration. • It is also found that the substrate can also detect low concentration of Aspartame (APM, 0.0625 g/L), and the detection limit is much lower than the daily intake of human body. It proves that the substrate has good SERS performance and broad application prospects. This paper presents the design of a bottom-up "sandwich" configuration substrate via electrostatic self-assembly. A silver microplate (AgMP) serves as the stable structural base, onto which monolayer graphene is wet-transferred. Au@Ag nanocubes (Au@Ag NCs) are then assembled on the upper layer through liquid-liquid three-phase self-assembly, forming a Au@AgNCs/G/AgMP "sandwich" substrate. The combination of electromagnetic enhancement from noble metal nanoparticles and chemical enhancement from graphene synergistically amplifies the signal of detected molecules, leading to significant Surface-Enhanced Raman Scattering (SERS) enhancement. Experimental results demonstrate that this substrate can detect Rhodamine 6 G (R6G) at concentrations as low as 10–12 M and Crystal Violet (CV) at 10–9 M. Moreover, the substrate can detect Aspartame (APM) at concentrations as low as 0.0625 g/L, well below the typical daily intake levels for humans. These findings indicate that the substrate exhibits excellent SERS performance and holds significant potential for broad applications. In this study, a bottom-up "sandwich" configuration substrate was designed via electrostatic self-assembly. Ag microplate (AgMP) is as a stable structural substrate, followed by wet transferred Graphene and liquid-liquid three-phase self-assembly is used to transfer the Au@Ag nanocubes(Au@Ag NCs) group on the upper layer, forming a core-shell structured Au@AgNCs/G/AgMP substrate. Experimental results showed that the substrate could detect the Rhodamine 6G (R6G, 10–12 M) and the Crystal violet (CV, 10–9 M) at a low concentration. In addition, the substrate can also detect low concentration of Aspartame (APM, 0.0625 g/L), and the detection limit is much lower than the daily intake of human body. It proves that the substrate has good SERS performance and broad application prospects. [Display omitted] [ABSTRACT FROM AUTHOR]

Metallic oxide can induce localized surface plasmon resonance (LSPR) through creating vacancies, which effectively achieve high carrier concentrations and offer advantages such as versatility and tunability. However, vacancies are typically created by altering the stoichiometric ratio of elements through doping, and it is challenging to achieve LSPR enhancement in the visible spectral range. Here, we have assembled Cu 2 O 1- x -superlattices to induce a high concentration of oxygen vacancies, resulting in LSPR within the visible spectrum. Combining this technique with theoretical models, we have elucidated the mechanism behind the origin of LSPR. We also provide evidence of strong and uniform LSPR exhibited by this structure under visible light. This significantly enhances the electromagnetic field in semiconductor-based surface-enhanced Raman scattering (SERS), with a detection limit concentration reaching 10 -9 M compared to conventional gold nanoparticles (55 nm). Our strategy provides a new perspective and potential for controlling carrier concentration and generating LSPR in metal oxide nanoparticles.