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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]

Structure, especially to track and monitor the phagocytosis process of nanoparticles by cells. Herein, we prepared a MoO2 hollow nanosphere with a strong surface plasmon resonance effect in the visible light region, which exhibited an excellent surface enhanced Raman scattering effect. When the 4-mercaptobenzoic acid (4-MBA) molecules are modified, it can be efficiently used as Raman probe molecules to perform clear three-dimensional cell imaging. No matter when the nanoparticles are located inside the cell, outside the cell or partly inside the cell, they all can be clearly presented by this enhanced Raman probe molecule. These results provide a rapid and accurate method for three-dimensional imaging of cells, especially for tracking the phagocytosis of nanoparticles. [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]

In this work, Raman measurements of 1–5-layer WSe2 supported on SiO2/Si in the temperature range of 133 to 533 K are reported. A physical model including both volume effect and temperature effect is used to quantitatively understand the nonlinear temperature dependence of E 2 g 1 Raman mode. It is found this nonlinear dependence of Raman mode mainly originates from thermal expansion effect and three-phonon scattering. The former effect increases with an increase in number of layers, which is inverse for the latter effect. The temperature-dependent thermal expansion coefficients of 1–5-layer WSe2 are also obtained from Raman spectra. The full width at half maximum (FWHM) of E 2 g 1 mode is also systematically studied both experimentally and theoretically in the temperature range of 133 to 413 K. It is found that the increase in FWHM of E 2 g 1 mode originates from decaying of E2g1 phonon. This work will promote the understanding of anharmonic behaviors of phonons in WSe2 flakes with different thicknesses. [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]