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Sulfamethazine (SM2) is an antibacterial drug，which has been extensively used in human and veterinary medicine, long-term consumption of which may lead to the accumulation of sulfonamides in the body. Detection of sulfonamides often uses microbiological approaches, mass spectrometry and chromatography, which are expensive and time-consuming. Surface-enhanced Raman scattering-based immunochromatographic assay (SERS-ICA) has been recently applied in the detection. Herein, a Janus-labeled Au nanoparticle with subnanosized SiO 2 -monoclonal antibody and SERS reporter (DTNB) modified simultaneously (mAbAuNpDTNB) has been developed in a SERS-based lateral flow immunosensor, which can be used for rapid, quantitative and ultrasensitive detection of sulfamethazine residue in milk. The mAbAuNpDTNB exhibits a specific array on a paper stripe, which not only identifies sulfamethazine but also straightforwardly exposes the Raman reporter between the AuNps via self-assembly. The detection sensitivity of SERS-ICA for sulfamethazine reached 0.1 pg/mL, which was far below the previously published value by ELISA and the maximum residue limit set by the European Union. The entire SERS-ICA detection for sulfamethazine was completed within 15 min. Furthermore, high accuracy for this assay was exhibited in the spiking experiment with a recovery percentage of 88.1%–112.7%. The results demonstrated that this SERS-ICA can potentially be applied in point-of-care testing as an ultrasensitive and quantitative to semi-quantitative analytical method. [Display omitted] • A Janus-labeled Au nanoparticle (mAbAuNpDTNB) by a SERS-LFIA was reported for the detecting of Sulfamethazine in milk. • The mAbAuNpDTNB exhibits specific array on paper stripe. • The mAbAuNpDTNB recognizes Sulfamethazine and can directly expose Raman reporters between AuNps through self-assembly. • The detection of the SERS-ICA for Sulfamethazine achieved a sensitivity of 0.1 pg/mL. [ABSTRACT FROM AUTHOR]

Abstract: The lateral flow immunoassay is used in commercial pregnancy detection, and is an accepted point-of-care testing technique. The most widely used format for lateral flow immunochromatographic strips uses gold nanoparticles for colorimetric detection. However, this method often suffers from poor quantitative discrimination and low analytical sensitivity. To address these limitations, lanthanide chelate-loaded silica nanoparticles have been used as fluorescent labels. The fluorescent nanoparticles can easily bind to antibodies, with dextran as a linker. The strip reader described here was based on a sandwich immunoreaction performed on a strip, using lanthanide-labeled antibodies that served as signal vehicles for the fluorescent readout. The strip reader was used as a quantitative test system. In this work, Pantoea stewartii subsp. stewartii (Pss) was used as a model analyte to demonstrate the use of the strip reader. Under optimal conditions, the detection limit was determined as 103 cfu/mL. The quantification limit was calculated to be 104 cfu/mL. The detection limit for Pss was 100 times lower than those displayed by colloidal gold-labeled strips or ELISAs. No cross-reactions were observed with the other nine strains, indicating the good specificity of the Pss strip. This strip showed good stability in repeated tests. The tests using the fluorescence immunochromatographic strip were easy to perform, rapid, and sensitive. Methods using fluorescence strips and a strip reader have the potential to be a powerful tool for the quantification of bacteria. [Copyright &y& Elsevier]

Highlights: [•] The technique enhances the detection sensitivity by inducing the clustering of gold particles on the nitrocellulose strip. [•] The operating time is very short (about 15min). Compared with commercial test strips, the method is 100-fold more sensitive. [•] The method is simple, rapid, economic, sensitive, specific, and results in detection with the naked eye. [•] The technique will be a powerful tool to carried out on-site because of its high sensitivity, specificity, and speed. [Copyright &y& Elsevier]

A bead-based competitive fluorescence immunoassay for the detection of triazophos has been developed. In this method, a conjugate of hapten and ovalbumin covalently bound to carboxylated fluorescent bead was used as a coating antigen and goat anti-mouse IgG/R-phycoerythrin conjugate was used as the fluorescent molecular probe. For standards (in 5% methanol in phosphate-buffered saline), the detection range was 0.02–50 ng/ml and the average coefficient of variation (CV) was 8.9%. This bead-assay was highly specific for triazophos, and none of other the structurally similar compounds (diazinon, malathion, parathion and fenitrothion) were recognised (<0.01% cross-reactivity). Vegetable samples (cabbage, carrot, green pepper, spinach, eggplant) were spiked with triazophos in the range of 1.0–100.0 ng/g and analysed by the bead-based immunoassay. The mean recovery and CV were 90.6 and 11.9%, respectively. The results confirmed that the bead-based fluorescence immunoassay is applicable for analysis and quantification of highly hydrophobic pesticide residues in vegetables. [ABSTRACT FROM PUBLISHER]

A portable immuno-microchip system consisting of low-cost biocompatible-polystyrene chips, a mini-vacuum pump, and a base unit for a LED light source as a miniaturized optical readout was devised. The surfaces of the micro-channels were processed with plasma to be more hydrophilic and were characterized by kinetic coating with a CCD scanning method. To demonstrate the feasibility of this novel system for the determination of a small molecule control assay, a simple, specific, and rapid method was established for drug analysis of morphine and its analogs, 6-monoacetylmorphine and morphine-3-glucuronide. Morphine-3-site antigen and a multi-target polyclonal antibody to morphine and derivatives were prepared and a competitive immunoassay was performed on the chip. The measurement can be carried out automatically and avoids time-consuming incubation steps. A detection sensitivity of below 1.0 ng/mL was achieved, which is comparable with the enzyme-linked immunosorbent assay (ELISA) technique. [ABSTRACT FROM AUTHOR]

Four ELISA formats, antigen-coated indirect, antigen-coated direct, antibody-coated, and the secondary antibody-coated, were developed using monoclonal antibody to determine cephalexin. Results showed that the secondary antibody-coated method of ELISA had a better performance in the establishment of standard curves. The optimized secondary antibody-coated ELISA was used to determine cephalexin spiked in pig muscle, pig kidney, pig liver, chicken muscle, chicken liver, and cow's milk. The limits of detection were 0.09 ng/g, 0.15 ng/g, 0.26 ng/g, 0.13 ng/g, 0.19 ng/g, and 0.08 ng/mL in pig muscle, pig kidney, pig liver, chicken muscle chicken liver, and cow's milk, respectively. A mean recovery of 77.2–128.5% and coefficient of variation of 2.6–14.7% were obtained. The results given by the ELISA method were in agreement with those of the LC-MS/MS method, which confirmed the potential of the ELISA method for the monitoring of cephalexin in milk and animal tissues. [ABSTRACT FROM AUTHOR]

Lily symptomless virus (LSV) is the most common lily virus, being detected in many species and hybrids. We established a microsphere-based fluorescent immunoassay for the determination of LSV, using a polyclonal antibody against LSV covalently bound to carboxy-modified microspheres able to capture LSV antigen. A monoclonal antibody against LSV conjugated to quantum dots (QDs) was used as a fluorescent probe, enabling LSV to be fluorescently detected by a combination of encoded beads and QDs. This method was 16 times more sensitive than ELISA in the detection of LSV, and could potentially be applied to the simultaneous detection of inhomogeneous matter. [ABSTRACT FROM AUTHOR]

An ultrasonic method to synthesize gold nanoparticles with uniform size was reported. Effects of ethanol concentration, solution pH, ultrasonic irradiation power, and time on the formation of gold nanoparticles were investigated. The obtained gold nanoparticles were characterized by ultraviolet-visible (UV-vis) absorption spectra and scanning electron microscope (SEM). The method performed in ethanol solution under ultrasonic irradiation is friendly to the environment. Furthermore, a nanogold-labeled probe was used to develop an immunochromatographic method for detection of kanamycin. [ABSTRACT FROM AUTHOR]

Abstract: Development of a microsphere-based competitive fluorescence immunoassay for the determination of hazardous low-molecular-weight compounds in food is described. In this method, antigens are covalently bound to carboxy-modified microspheres to compete monoclonal antibody with low-molecular-weight compounds in food samples; mouse IgG/fluorescein isothiocyanate conjugate is used as the fluorescent molecular probe. Thus, the hazardous low-molecular-weight compounds are quantified using a multiparameter flow cytometer. This method has been evaluated using clenbuterol as a model compound. It has a sensitivity of 0.01ng/mL with dynamic range of 0.01–100ng/mL, and the concentration of clenbuterol providing 50% inhibition (IC50) is 1.1ng/mL. The main advantages of this method are its high efficiency, biocompatibility, and selectivity, as well as ultralow trace sample consumption and low cost. [Copyright &y& Elsevier]

The global environmental concern surrounding microplastic (MP) pollution has raised alarms due to its potential health risks to animals, plants, and humans. Because of the complex structure and composition of microplastics (MPs), the detection methods are limited, resulting in restricted detection accuracy. Surface enhancement of Raman spectroscopy (SERS), a spectral technique, offers several advantages, such as high resolution and low detection limit. It has the potential to be extensively employed for sensitive detection and high-resolution imaging of microplastics. We have summarized the research conducted in recent years on the detection of microplastics using Raman and SERS. Here, we have reviewed qualitative and quantitative analyses of microplastics and their derivatives, as well as the latest progress, challenges, and potential applications. [ABSTRACT FROM AUTHOR]

In recent years, nanomaterials have attracted the research intervention of experts in the fields of catalysis, energy, biomedical testing, and biomedicine with their unrivaled optical, chemical, and biological properties. From basic metal and oxide nanoparticles to complex quantum dots and MOFs, the stable preparation of various nanomaterials has always been a struggle for researchers. Microfluidics, as a paradigm of microscale control, is a remarkable platform for online stable synthesis of nanomaterials with efficient mass and heat transfer in microreactors, flexible blending of reactants, and precise control of reaction conditions. We describe the process of microfluidic preparation of nanoparticles in the last 5 years in terms of microfluidic techniques and the methods of microfluidic manipulation of fluids. Then, the ability of microfluidics to prepare different nanomaterials, such as metals, oxides, quantum dots, and biopolymer nanoparticles, is presented. The effective synthesis of some nanomaterials with complex structures and the cases of nanomaterials prepared by microfluidics under extreme conditions (high temperature and pressure), the compatibility of microfluidics as a superior platform for the preparation of nanoparticles is demonstrated. Microfluidics has a potent integration capability to combine nanoparticle synthesis with real-time monitoring and online detection, which significantly improves the quality and production efficiency of nanoparticles, and also provides a high-quality ultra-clean platform for some bioassays. [ABSTRACT FROM AUTHOR]

Nanoscale calcium carbonate and nanoscale titanium dioxide are two kinds of very important, manufactured nanomaterials which have had applications in industry for many years. The production and application of these two kinds of nanomaterials are expected to be expanded in the future. Accordingly, there is a need for better defining their characteristics contributing to performance. ISO/TC229 WG4 is the fourth working group of ISO/TC229, which is in charge for establishing the nanomaterial specifications, and the nanoscale calcium carbonate and the naonoscale titanium dioxide are the first two selected nanomaterials in this working group; the two technical specifications, ISO/WD 11931-1 and ISO/WD 11937-1, are under development. [ABSTRACT FROM PUBLISHER]

Identification of the gasoline purity is important for quality control and detection of gasoline adulteration. Principal component analysis and Raman spectroscopy were used to authenticate gasoline adulterated with methyl tert-butyl ether (MTBE) and benzene. Gasoline could be clearly distinguished from gasoline adulterated with MTBE and benzene by a plot of the first principal component ( x-axis) against the second principal component ( y-axis). And the radial basis function neural network was used for quantitative prediction of the volume percentages of MTBE and benzene in gasoline based on Raman Spectra. The correlation coefficient ( r) and mean absolute percentage error between predictive values and spiked values were 0.9907 and 0.9934 and 15.73 and 8.19%, respectively. Moreover, the Raman spectra of the samples were obtained with a portable Raman spectrometer. Therefore, the method is simple, effective, fast, does not require sample pre-processing, and is promising for rapid gasoline detection. Copyright © 2012 John Wiley & Sons, Ltd. [ABSTRACT FROM AUTHOR]

A method of principal component analysis was employed to authenticate genuine olive oil based on Raman spectroscopy, which can reliably distinguish olive oil from other types of oils and can also accurately identify the level of adulteration in a set of olive oil samples contaminated with 5% or more of other types of oils, such as soybean oil, rapeseed oil, sunflower seed oil, and corn oil. The method is very easy, effective, time-saving, and requires minimal sample preparation. Therefore, the method is a promising technique for the rapid authentication application of olive oil. [Supplementary materials are available for this article. Go to the publisher's online edition of Analytical Letters for the following free supplemental resource(s): Additional text and table] [ABSTRACT FROM AUTHOR]

In this study, we carried out an amplified luminescent proximity homogeneous assay (AlphaLISA) to detect sulfonamides (SAs) antibiotic residues in plasma, milk, pork, chicken, and fish. The SAs AlphaLISA method can detect 13 SAs with half‐inhibitory concentration (IC50) 2.11–29.77 ng/ml. The detection level of those SAs was 0.3–41.12 ng/ml in matrices, which satisfied the maximum residue limit (MRL) of the European Union, United States, and China. Our recoveries are in the range of 88% to 116.8% with a coefficient of variation less than 9.3% for different spiked food samples. We observed a good correlation between the AlphaLISA and liquid chromatography–tandem mass spectrometry (LC‐MS/MS) with blood samples from injected rabbits. The established AlphaLISA method provided a no‐washing, rapid, high‐throughput screening tool for SAs in food quality control, which is suitable for small‐volume samples. [ABSTRACT FROM AUTHOR]

Simple and traditional hydrothermal fabrication of a novel balsam pear-shaped CuO with high SERS enhancement is presented. XRD (X-ray diffraction), SEM (scanning electronic microscopy), TEM (transmission electron microscope), HRTEM (high-resolution transmission electron microscope), UV-Vis, and Raman are adopted to ensure that this balsam pear-shaped CuO with dense nanoparticle protuberance is successfully prepared. The LOD of this CuO SERS substrate is 4.79 μg L−1 with R6G as molecular probe. By using DFT (density functional theory) calculation and FDTD (finite difference time domainmethod) simulation, both EM (electromagnetic enhancement) and CM (chemical enhancement) mechanisms are investigated, and the results show that these two-enhancement mechanisms can coexist in this balsam pear-shaped CuO. Finally, the prepared substrate has been applied for the determination of trace levels of paraquat in solution , and results show that its LOD for paraquat is 275 μg L−1 (optimum Raman band: 1646 cm−1 Raman shift), which is better than the government standard in China. A dexterous and facile way for fabrication of CuO SERS-active substrates with low cost and high performance, quite promising in detection of chemically hazardous substances and pesticide residue is provided. [ABSTRACT FROM AUTHOR]

Herein, a transparent and reproducible substrate, fabricated using polydimethylsiloxane (PDMS) laminated with self-assembled Ag nanoparticles (Ag NPs), was employed as a universal surface-enhanced Raman scattering (SERS) substrate for the detection of targets with various matrices. The Ag NPs were assembled in a two-dimensional manner via a self-assembly technique. Due to the electrostatic interaction between the Ag NPs, the reproducibility of the assembly was ensured by the fixed density of the assembled Ag NPs at saturated assembly states. The assembled pattern and plasmon resonance of the Ag NPs were well preserved during the molding and curing of PDMS. As a result, the Ag NP laminated PDMS film exhibited a SERS effect to the adsorbed p-aminothiophenol comparable to that of the assembled Ag NPs on a glass slide. Extra SERS enhancement was achieved by construction of a Ag (PDMS)/molecule/Ag (glass) configuration due to the electromagnetic coupling between the Ag NPs. The Raman scattering of 4-mercaptobenzoic acid and benzotriazole modified on the surfaces of a smooth Au electrode and copper foil, respectively, was detected with the aid of the Ag NP-laminated PDMS film. Furthermore, malachite green dispersed in a KBr solid matrix was quantitatively determined with a detection limit of 0.5 μg/g. It is suggested that the SERS enhancement and consequential SERS detection sensitivity of the target molecules may be further maximized by adjusting the distance between the target molecules and the Ag NPs laminated on the PDMS film. [ABSTRACT FROM AUTHOR]

The electrochemical splitting of water is considered to be an efficient and potential technique for producing clean hydrogen and oxygen. Although, there are lots of significant developments in composite of superior hydrogen evolution reaction (HER) or oxygen evolution reaction (OER) catalyst applied in water splitting currently, designing non-precious and low-cost bifunctional electrocatalysts with high performance is still an attractive challenging issue. In this article, we report a novel bifunctional electrocatalyst with cobalt-based nanoparticles (NPs) embedded in Zn-doped hierarchical porous three-dimension N-doped carbonization structure via an annealing process of metal organic frameworks (MOFs) connected by N-doped carbon nanotube (denoted as Co–Zn/PNC). This composite structure possesses the characteristics of more active sites, numerous mesopores and high conductivity. The resulting electrocatalyst (Co–Zn/PNC) can be used as both anode and cathode to roust the overall water splitting, getting a current density of 10 mA cm−2 at a cell voltage of 1.63 V in 1.0 M KOH electrolyte. • Co–Zn/PNC is prepared by Zn-doped ZIF-67 linked by N-doped CNT through pyrolysis. • Bifunctional electrocatalyst Co–Zn/PNC exhibits excellent HER and OER performance. • Zn doping can enhance the electrochemical performance of Co–Zn/PNC. [ABSTRACT FROM AUTHOR]

Graphical abstract The electronic structure of GeC/WS 2 heterostructures can be effectively modulated by both external electric field and strain. A significant change in the size of the band gap is due to the shift of band edges caused by the electric field induced static potential and/or the strain induced deformation potential. Abstract Van der Waals (vdW) heterostructures made by stacking two-dimensional (2D) materials, open up a wide landscape of possibilities in bandgap engineering, due to the distinct properties of the building layers and diverse stacking arrangements possible. In this work, ab initio calculations based on density functional theory were performed to systematically investigate the tuning of electronic properties of GeC/WS 2 heterostructures by applying either a vertical external electric field or a biaxial strain. GeC/WS 2 heterostructures exhibit a direct band gap and a type-II vdW heterostructure. The bandgap of GeC/WS 2 heterostructure can be dramatically modulated by applying a vertical external electric field or a biaxial strain, and semiconductor-metal transitions are observed under high electric field and large strain. The change of band gap is due to the shift of band edges of the heterostructure due to the static electric field induced potential energy and strain induced deformation potential. Differences in the pattern of change style can be assigned to changes of the bands assigned to CBM and VBM. It is interesting to note that the shift of band edge by electric field is screened by a factor of 3.54 as compared to the electrostatic calculation. The deformation potential of the CBM consisted of W 5d orbital is −1.58 eV, and that of the VBM consisted of C 2p orbital is −0.01 eV. In addition, the optical properties of the heterostructure exhibit a significant enhancement compared to the constituent layers, which indicates improved light absorption. The above results suggest that GeC/WS 2 vdW heterostructures can find applications as opto-electronic devices and efficient solar energy harvesting materials. [ABSTRACT FROM AUTHOR]

A method based on droplet spray ionization (DSI) mass spectrometry was described for rapid, direct analysis of seawater samples. By spontaneous desalting (SD) of droplet seawater on a cover slip corner, the target analytes could be separated from the salts. The separated targets are then dissolved in a spray solvent for mass spectrometric analysis. The desorption/ionization of salts is impeded due to their microsolubility or even insolubility in the spray solvent, thus greatly reducing the suppression of ionization of the analyte. It has been demonstrated that the desalting process is spontaneous and highly effective, which simplifies the operation. The dependence of signal intensity on the operation parameters was investigated as well. With this method, a wide range of antibiotics including sulfonamides, macrolides, amphenicols, quinolones, rifamycins, and mixtures in seawater have been successfully detected in either positive or negative ion modes. Limits of detection (S/N ≥ 3) were determined to be 0.52 and 0.20 pg for trimethoprim and clarithromycin, respectively. Moreover, satisfactory accuracy and precision were obtained according to the analysis of real seawater samples. Our results show that the combination of DSI and spontaneous desalting is a simple, sensitive, and rapid method for direct detection of analytes in seawater. [ABSTRACT FROM AUTHOR]

In-situ synthesized hotspot can be ascribed as uniformity and enhanced electronegativity, leading a near 103 increase of enhanced factor and large improvement of Raman signals stability compared with bare Au nanostructure. Furthermore, the hotspot precise modification approach can be identified immediately by coloration under sunlight and applied in SiO 2 substrate to avoid the Ag oxidation in ambient conditions. Thus, the simple and effective SERS enhancement method via atomic modified can be widely and potentially used in practical detection. [Display omitted] • A hierarchical structure has been firstly constructed via single-atom sites photoinduced nanosized Ag uniformly dispersed on Au nanostructure. • The single-atom site in-situ synthesized hotspots possess a 3 orders of magnitude improvement beyond that of undecorated Au substrates when applied in pesticide residue acetamiprid in practical detection. • The novel nanostructure approach also enables the testing stripe to have a strong coloration under sunlight that can be used immediately to detect analytes, avoiding the inevitable Ag oxidation in practical application. Surface-enhanced Raman scattering (SERS) is a promising technique for detecting trace analytes, but the design of hotspots with nanoscale precision remains a challenge for achieving accurate detection. Here, photoinduced-synthesized single-atom sites Ag are uniformly dispersed on an Au nanostructure to form hierarchical hotspots. The precise control of hotspots exhibits significantly improved SERS performance with an enhancement factor (EF) of more than 109 and great Raman signal quantification for pesticide residue acetamiprid and cycocel. The superiority of the precise structure of hierarchical hotspots can be ascribed to structure uniformity and enhanced electronegativity, leading to a limit of detection (LOD) of down to 0.1 ppb and notable improvement of Raman signals stability compared with bare Au nanostructure. The LOD is among the best SERS substrates in literatures. Furthermore, the precise hotspot modification approach can be identified immediately by coloration under sunlight and applied to a SiO 2 substrate to avoid the Ag oxidation in ambient conditions. Thus, the simple and effective SERS enhancement method via single-atom site decoration strategy is anticipated to shed light on practical sensing detection. [ABSTRACT FROM AUTHOR]

Schematic images of the experimental setup of obtaining polarized Raman spectrum an experimental investigation on polarized Raman spectra of 1L, 7 L, and 15 L ReS2 supported on SiO2/Si substrate with temperature ranging from 110 K to 590 K is reported. The polarization of incident laser is tuned parallel either to the a-axis or b-axis in ReS2 flakes. It is discovered that Raman modes of ReS2 show redshifts with an increase of temperature and first-order temperature coefficients are observed for ReS2 flakes along different crystal axis. The larger temperature coefficient along b-axis may be originated from the large group phonon velocity. In addition, the full-width at half maximum (FWHM) of Raman modes of ReS2 flakes with different thicknesses along different crystal axis are also quantitatively studied and it is found phonon decay is responsible for the broadening of phonon mode. This work will promote the understanding of anisotropic thermal properties of ReS2 flakes. The study of anisotropic thermal properties of ReS2 will lay a certain foundation for exploring the stability of ReS2 optoelectronic devices. [Display omitted] • This work will promote the understanding of anisotropic thermal properties of ReS2 flakes. • The study of anisotropic thermal properties of ReS2 will lay a certain foundation for exploring the stability of ReS2 optoelectronic devices. • This work will promote the study of thermal anisotropy in two-dimensional anisotropic materials. • This work will lay a solid foundation for the development of thermoelectric and optoelectronic applications in the future. With present in-plane anisotropic optical, electrical, and optoelectronic properties, atomically thin Two-dimensional (2D) rhenium disulfide (ReS 2) is of considerable interest for its wide-range intriguing applications in novel devices. However, although the research field related to ReS 2 has made growing progress, the axis-dependent thermal properties are still unknown. Herein, temperature-dependent polarized Raman spectroscopy is carried out to systematically investigate the anisotropic thermal properties of ReS 2 flakes with layers (L) of 1, 7, and 15 with temperature ranging from 110 K to 590 K. The polarization of the incident laser is tuned parallel to the crystal axis of the ReS 2 flakes. It is discovered that Raman modes of ReS 2 redshift with an increase of temperature and the first-order temperature coefficients are obtained along different crystal axes whose values are decreased with an increase in number of layers. The different temperature coefficients along different axis may be originated from the different group phonon velocities. In addition, the full width at half maximum (FWHM) of Raman modes of ReS 2 flakes along different axes are also quantitatively studied. It is found that the broadening of phonon modes is originated from phonon decay. This work will promote the study of thermal anisotropy in two-dimensional anisotropic materials. [ABSTRACT FROM AUTHOR]

[Display omitted] • New Mo1-xWxS2 two-dimensional nanosheets were prepared by the one-pot method. • Compared with MoS2, the Raman intensity of Rhodamine 6G (10−6 M) was amplified by 1.7 times with Mo1-xWxS2 nanosheets as the substrate. • With abundant edge active sites that facilitate charge transfer, Mo1-xWxS2 nanosheets could better enhance SERS signals. A new Mo 1- x W x S 2 two-dimensional nanosheets were prepared by the one-pot method. After certain Mo atoms in MoS 2 were replaced by W ones in a hydrothermal reduction procedure, Mo 1- x W x S 2 was formed on the Mo foil. Well enhanced Mo 1- x W x S 2 nanosheets were prepared when the sodium tungstate concentration got under control. Various characterizations were carried out, which indicate that Mo 1- x W x S 2 nanosheets with good crystallinity. Compared with MoS 2 , the Raman intensity of Rhodamine 6G (10−6 M) was amplified by 1.7 times with Mo 1- x W x S 2 nanosheets as the substrate. The characteristic Raman peaks could still be clearly distinguished until the concentration of Rhodamine 6G (R6G), Methylene blue (MB) and Crystal violet (CV) down to 10−8, 10−8 and 10−7 M, respectively. With abundant edge active sites that facilitate charge transfer, Mo 1- x W x S 2 nanosheets could better enhance SERS signals of target detection molecules and get a good linear relationship exists within the concentration and Raman peak strength. In addition, R6G SERS detection also shows excellent reproducibility and long-term stability of this TMDs SERS substrate. [ABSTRACT FROM AUTHOR]

[Display omitted] • Au/Fe 3 O 4 /MIL-101(Cr) SERS substrate with high SERS performance and uniformity is prepared via a simple method. • The substrate could effectively combine the excellent adsorption ability of MOF with strong surface plasmon resonance property of gold nanoparticles, improving the sensitivity and stability of SERS detection. And this magnetic material can be gathered rapidly and availably by magnetic enrichment instead of other means, avoiding the loss or even damage of the samples. • The substrate with excellent SERS detection ability of sulfapyridine provides potential for the sensitive detection of the antibiotics residue. Fabrication of a magnetic substrate based on metal–organic frameworks (MOFs) with high sensitivity and stability for surface-enhanced Raman scattering (SERS) analysis were reported in this paper. MIL-101(Cr) nanoparticle prepared via a traditional hydrothermal reaction, which was combined with Fe 3 O 4 to synthesize the Fe 3 O 4 /MIL-101(Cr) composites. Then, the concentration of chloroauric acid and the time of reduction reaction were adjusted to acquire the optimal Au/Fe 3 O 4 /MIL-101(Cr) (AF-MIL) SERS substrate. The detection ability of the substrate can down to 10-8 mol/L for Rhodamine 6G (R6G) as probe molecule, and the relative standard deviation (RSD) is only about 4.48 %, which indicates that it possesses wonderful SERS performance and uniformity. Finally, the as-synthesized substrate has been adopted to test the trace level sulfapyridine, with its desirable detection ability can down to 10-6 mol/L. Such desirable SERS substrate with facile and effective operation holds great promise in the fast sensitive detection of the antibiotic residue and some other pollutants in environment. [ABSTRACT FROM AUTHOR]

A method for surface-enhanced Raman spectroscopy (SERS) sensing of polycyclic aromatic hydrocarbons (PAHs) is reported. Gold nanoparticles (AuNPs) decorated hydrophobic porous glycidyl methacrylate–ethylene dimethacrylate (GMA–EDMA) polymer is developed as the SERS substrate. GMA–EDMA material with porosity and permeability shows rapid and efficient adsorption of PAHs through presumed hydrophobic interaction, which brings the analytes close to the substrate. Meanwhile, the three dimensional porous morphology might benefit AuNPs distribution for high SERS enhancement. Studies on the effects of AuNPs surface coverage on the substrate and time of PAHs–substrate interaction are presented. The qualitative analysis and quantitative tendency of this method for PAHs detection are investigated with anthracene, phenanthrene and pyrene as probe molecules, showing that the characteristic fingerprint vibrational peaks of each PAH can be readily identified, and the limit of detections are 0.93 × 10 −7 , 4.5 × 10 −7 and 1.1 × 10 −7 M respectively. Moreover, the substrate exhibits high reproducibility with the relative standard deviation about 16% in spot and spot SERS intensity. Using this method for rapid screening of PAHs mixture in some water samples are performed well, which might be useful for environmental pollutions monitoring. [ABSTRACT FROM AUTHOR]

We report on a facile immunoassay for porcine circovirus type 2 (PCV2) based on surface enhanced Raman scattering (SERS) using multi-branched gold nanoparticles (mb-AuNPs) as substrates. The mb-AuNPs in the immunosensor act as Raman reporters and were prepared via Tris base-induced reduction and subsequent reaction with p-mercaptobenzoic acid (pMBA). They possess good stability and high SERS activity. Subsequently, the modified mb-AuNPs were covalently conjugated to the monoclonal antibody (McAb) against the PCV2 cap protein to form SERS immuno nanoprobes. These were captured in a microtiterplate via a immunoreaction in the presence of target antigens. The effects of antibody concentration, reaction time and temperature on the sensitivity of the immunoassay were investigated. Under optimized assay conditions, the Raman signal intensity at 1,076 cm −1 increases logarithmically with the concentrations of PCV2 in the concentration ranging from 8 × 10 2 to 8 × 10 6 copies per mL. The limit of detection is 8 × 10 2 copies per mL. Compared to conventional detecting methods such as those based on PCR, the method presented here is rapid, facile and very sensitive. [Figure not available: see fulltext.] [ABSTRACT FROM AUTHOR]

A europium nanoparticle-based lateral flow immunoassay for highly sensitive detection of chloramphenicol residue was developed. The detection result could be either qualitatively resolved with naked eye or quantitatively analyzed with the assistance of a digital camera. In the qualitative mode, the limit of detection (LOD) was found to be 0.25 ng/mL. In the quantitative mode, the half-maximal inhibition concentration (IC50) was determined to be 0.45 ng/mL and the LOD can reach an ultralow level of 0.03 ng/mL, which is ~100 times lower than that of the conventional colloidal gold-based lateral flow immunoassay. Potential application of the established method was demonstrated by analyzing representative cow milk samples. [Figure not available: see fulltext.] [ABSTRACT FROM AUTHOR]

We show that tris base (TB), a widely used buffer substance, can act as a reducing agent to synthesize multi-branched gold nanoparticles (mb-AuNPs) from tetrachloroauric acid in a one-step process. The method is simple, fast, and inexpensive and produces mb-AuNPs that are virtually monodisperse, have a size of about 90 nm and typically >6 branches. Their UV-vis absorption peaks can be fine-tuned from the visible to the near-infrared (NIR) region by controlling the concentration of TB. The mb-AuNPs represent an efficient substrate for surface-enhanced Raman scattering (SERS), with an enhancement factor of 1.2 × 10. They were applied as substrates for SERS-based imaging of kidney cells. [Figure not available: see fulltext.] [ABSTRACT FROM AUTHOR]

We describe a novel surface-enhanced Raman scattering (SERS) tag that is based on Au/Ag core-shell nanostructures embedded with p-aminothiophenol. The Au/Ag core-shell sandwich nanostructures demonstrate bright and dark stripe structure and possess very strong SERS activity. Under optimum conditions, the maximum SERS signal was obtained with a 10 nm thick Ag nanoshell, and the enhancement factor is 3.4 × 10 at 1077 cm. After conjugation to the antibody of muramidase releasing protein (MRP), the Au/Ag core-shell nanostructures were successfully applied to an SERS-based detection scheme for MRP based on a sandwich type of immunoassay. [Figure not available: see fulltext.] [ABSTRACT FROM AUTHOR]

[Display omitted] • A simple method to remove PVP for high performance and reusable SERS substrate. • Cleaned AgNPs interface effectively enhanced the plasma resonance of the local surface (LSPR). • Residual PVP has basically no influence on detection of the molecular which absorbed stronger than PVP. The silver nanoparticles have been frequently used in SERS detection, for their unique optical properties and sensitive surface Raman enhancement properties. However, as the preparation of silver nanoparticles will use polyvinylpyrrolidone (PVP) to achieve the effect of reducing agent and surfactant, the surface of the prepared silver nanoparticles will be wrapped by PVP, forming an insulating layer and an ill-defined AgNPs interface, which limits the plasmonic coupling between the laminates of AgNPs. This paper reported a simple method to remove PVP for high performance and reusable SERS substrate, and the residue of PVP was studied after clean centrifugal by ethanol or water. When the number of cleaning times reached 10, there was basically no residual of PVP. The cleaned AgNPs interface effectively enhanced the plasma resonance of the local surface (LSPR) and greatly improved the SERS activity of the substrate. Moreover, probe molecules (R6G) are introduced to study the influence of single molecule PVP on subsequent detection. Through the competitive relationship between the two, it can be concluded that residual PVP has basically no influence on detection of the molecular which absorbed stronger than PVP, and the remaining PVP can be ignored. [ABSTRACT FROM AUTHOR]

• AgNPs/MIL-101(Fe) nanocomposites is used as a Raman enhanced substrate to detect R6G. The results show that the substrate has better stability and uniformity. Its R6G Raman assignment peak position RSD = 7.55%, enhancement factor EF = 2.09 × 109. • AgNPs/MIL-101(Fe) nanocomposites as a Raman enhanced substrate can detect the lowest concentration of paraquat at 10−12 mol/L, and the Raman signal is relatively stable in different acid-base environments. Recently, in the research of Surface-enhanced Raman scattering (SERS) technology, it is found that the preparation of enhanced substrate is particularly important. In this work, the most commonly used methods were used to synthesize AgNPs and MIL-101(Fe), and AgNPs/MIL-101(Fe) nanocomposite was obtained through self-assembly of the two substances. Four different probe molecules were detected with the self-assembled substrate and compared with the results of same probe molecules with AgNPs and MIL-101(Fe) as SERS substrate separately, it was found that AgNPs/ MIL-101 (Fe) nanocomposites had a strong enhancing effect as SERS substrate. The Enhancement Factor (EF) value of 10−6 mol/L Rhodamine 6G (R6G) was calculated as 2.09 × 109, and the Raman intensities of the peak relative standard deviation (RSD) of R6G Raman attribution was calculated as 7.55%. The time stability of the material was studied and it was found that the reduced Raman signal and poor reproducibility were due to the AgNPs placement time. AgNPs/ MIL-101 (Fe) nanocomposites were used as SERS substrate to detect Paraquat with a minimum concentration of 10−12 mol/L. The signal values of Paraquat Raman detected at 10−6 mol/L in different pH environments were relatively stable. [ABSTRACT FROM AUTHOR]

Abstract: The synthesis of water-soluble fluorescent carbon dots (C-dots) has received much attention recently. Here, high quality fluorescent C-dots have been synthesized through low-temperature carbonization and simple filtration using watermelon peel, a waste and reproducible raw resource, as a novel carbon resource. This facile approach allows large-scale production of aqueous C-dots dispersions without any post-treatment process. The as-prepared C-dots possess small particle sizes (~2.0nm), strong blue luminescence, acceptable fluorescence lifetime and good stability in a wide range of pH values (pH 2.0–11.0) and at a high salt concentration. Besides, the obtained C-dots have been successfully applied in live cell imaging, indicating these carbon nanoparticles can serve as high-performance optical imaging probes. [Copyright &y& Elsevier]