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Surface enhanced Raman scattering (SERS) is a rapid and nondestructive technique that is capable of detecting and identifying chemical or biological compounds. Sensitive SERS quantification is vital for practical applications, particularly for portable detection of biomolecules such as amino acids and nucleotides. However, few approaches can achieve sensitive and quantitative Raman detection of these most fundamental components in biology. Herein, a noble-metal-free single-atom site on a chip strategy was applied to modify single tungsten atom oxide on a lead halide perovskite, which provides sensitive SERS quantification for various analytes, including rhodamine, tyrosine and cytosine. The single-atom site on a chip can enable quantitative linear SERS responses of rhodamine (10Supplementary material is available for this article at 10.1007/s40843-022-1968-5 and is accessible for authorized users.表面增强拉曼散射(SERS)是一种快速且无损的化学和生物分子检测技术. 高灵敏且定量化的SERS检测技术对其在实际中的应用至关重要, 尤其是对生物分子如氨基酸和碱基的便携化检测. 但是鲜有技术手段能够实现对这些最基本的生物分子进行高灵敏且定量化的拉曼检测. 我们提出了一种无需贵金属的单原子位点修饰芯片策略, 用钨单原子氧化物修饰铅卤钙钛矿芯片, 实现了多种检测物的高灵敏定量化识别, 包括罗丹明、 酪氨酸和胞嘧啶. 芯片上单原子位点技术能够实现对罗丹明、 酪氨酸和胞嘧啶的线性检测, 相应的定量化区间分别为: 10

A dual-wavelength rapid excitation Raman difference spectroscopy (DWRERDS) system for separation of Raman signals from background interference was developed. In the DWRERDS system, a dual-wavelength diode laser at 784.59 and 785.22 nm with volume Bragg gratings was used as the excitation light source. For each laser line, optical power could reach as high as 550 mW. Under dual-wavelength excitation mode, the DWRERDS system could switch each laser instantaneously and the excitation time of each laser was as short as 1 s. Two Raman spectra were measured with slightly shifted excitation wavelengths and subtracted from each other, resulting in a background-free difference spectrum. The DWRERDS system was applied to complex matrix background suppression, which could improve a very good signal-to-noise ratio (SNR) for Raman spectra. Although ethanol in Coca-Cola could not be detected by conventional Raman spectroscopy, the DWRERDS system could be used for the direct detection of ethanol in illegal alcoholic beverages. The experimental results showed that the limit of detection (LOD) of ethanol in Coca-Cola was volume percentage of 4.76% and the correlation coefficient for the linear regression was as high as 0.984. The DWRERDS system could be used to determine the concentration of ethanol in illegal alcoholic beverages within 1 min without any sample pretreatment.

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.

Surface-enhanced Raman scattering (SERS), owing to its high sensitivity and rapid response, has been widely used in various fields. However, it is still a challenge to prepare SERS substrates with ...

A new Mo

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 $$\rm{E}_{2g}^1$$ 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 $$\rm{E}_{2g}^1$$ 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 $$\rm{E}_{2g}^1$$ mode originates from decaying of E2g1 phonon. This work will promote the understanding of anharmonic behaviors of phonons in WSe2 flakes with different thicknesses.

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.

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.

This work reports an electrofluorochromic strategy on the basis of electric field control of fluorescent signal generation on bipolar electrodes (BPEs) for visualizing cancer cell surface glycoprotein (mucin 1). The device included two separate cells: anodic sensing cell and cathodic reporting cell, which were connected by a screen-printing electrode patterned on poly(ethylene terephthalate) (PET) membrane. In the sensing cell, anti-MUC1 antibody immobilized on a chitosan-multiwalled carbon nanotube (CS-MWCNT)-modified anodic BPE channel was used for capturing mucin-1 (MUC1) or MCF-7 cancer cells. Then ferrocene (Fc)-labeled mucin 1 aptamers were introduced through hybridization. Under an applied voltage, the ferrocene was oxidized and the electroactive molecules of 1,4-benzoquinone (BQ) in the cathodic reporting cell were reduced according to electroneutrality. This produced a strongly basic 1,4-benzoquinone anion radical (BQ•–), which turned on the fluorescence of pH-responsive fluorescent molecules of ...

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/WS2 heterostructures by applying either a vertical external electric field or a biaxial strain. GeC/WS2 heterostructures exhibit a direct band gap and a type-II vdW heterostructure. The bandgap of GeC/WS2 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/WS2 vdW heterostructures can find applications as opto-electronic devices and efficient solar energy harvesting materials.

The development of low-cost, biocompatible, and durable high-performance substrates is an urgent issue in the field of surface-enhanced Raman scattering (SERS). Herein, by reducing and exfoliating the TiO2-layered nanoplates in the gas phase, nitrogen-doped titanium monoxide (N-TiO) ultrathin nanosheets composed of 2-3 single layers with a thickness of only ∼1.2 nm are synthesized. Compared with pure TiO, the oxidation resistance of N-TiO is greatly improved, in which the oxidation threshold is significantly increased from 187.5 to 415.6 °C. The N-TiO ultrathin nanosheets are found to have strong surface plasmon resonance in the visible region. These ultrathin N-TiO nanosheets can be easily assembled into a large-scale flexible membrane and exhibit remarkable SERS effects. Moreover, this low-cost flexible SERS substrate combines the high durability of noble-metal substrates and the high biocompatibility of semiconductor substrates.

The synthesis of metallic transition metal nitrides (TMNs) has traditionally been performed under harsh conditions, which makes it difficult to prepare TMNs with high surface area and porosity due to the grain sintering. Herein, we report a general and rapid (30 s) microwave synthesis method for preparing TMNs with high specific surface area (122.6-141.7 m2 g-1) and porosity (0.29-0.34 cm3 g-1). Novel single-crystal porous WN, Mo2N, and V2N are first prepared by this method, which exhibits strong surface plasmon resonance, photothermal conversion, and surface-enhanced Raman scattering effects. Different from the conventional low-temperature microwave absorbing media such as water and polymers, as new concept absorbing media, hydrated metal oxides and metallic metal oxides are found to have a remarkable high-temperature microwave heating effect and play key roles in the formation of TMNs. The current research results provide a new-concept microwave method for preparing high lattice energy compounds with high specific surface.

Facing the complex environment of on-site detection, the development of active substrates with wide-spectrum surface-enhanced Raman scattering (SERS) activity is essential. Herein, we report on the low temperature and reproducible synthesis of plasmonic δ-MoN yolk microspheres by in situ-nitriding amorphous MoO2 microspheres at 500 °C and 1 atm. The yolk-structured δ-MoN exhibits strong and wide-spectrum surface plasmon resonance and SERS effects and can perform highly selective detection for probes with different absorption wavelengths under excitation of 532, 633, and 785 nm lasers, with a limitation of 10-11 M and an enhanced factor of 3.6 × 107. Moreover, the plasmonic δ-MoN yolk microspheres have high environmental durability, which can maintain high sensitivity in strong acid and alkaline solutions.

Remote Raman instruments have become powerful analytical tools in some special environments. However, ambient daylight is the main limitation in the data acquisition process. To suppress daylight background interference and obtain a high signal-to-background ratio (SBR), we develop a dual-wavelength wide area illumination Raman difference spectroscopy (WAIRDS) system for daytime remote detection. In the WAIRDS system, a wide area illumination scheme and shifted-excitation Raman difference spectroscopy method are used to improve the reliability of collected Raman spectra. Measurements of polystyrene indicate that the WAIRDS system can be operated to obtain background-free Raman spectra under different levels of daylight background interference. The remote results show that the improvement in SBR is about three- to fivefold, and the system can work at distances of up to 9.2 m on a sunny afternoon. Moreover, to be close to the actual detection, the system is used for mineral and explosive raw material detection during daytime measurement. Measurements show that the WAIRDS system will be a useful tool for many remote applications in the future.

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., An amplified luminescent proximity homogeneous assay (AlphaLISA) was carried out in the detection of 13 SAs antibiotic residues in foods with the half‐inhibitory concentration (IC50) values from 2.11 to 29.77 ng/ml. Good correlations were observed between the AlphaLISA and liquid chromatography–tandem mass spectrometry (LC‐MS/MS) results for blood samples from injected rabbits.

Controllable synthesis of novel metal nanoparticles and effective capture of hotspots are of great significance for SERS (surface-enhanced Raman spectroscopy) detection. Therefore, in this paper, a green controllable synthesis method of gold nanoparticle was achieved via epigallocatechin gallate reduction. Different morphologies of gold nanoparticles were synthesized just by changing the solution pH values, and the growth kinetics of AuNPs (gold nanoparticles) were systematically studied. The synthetic AuNPs were put in a droplet to study dynamic variations of self-assembly SERS hotspots from the liquid sol state to the solid dry state. The addition of halogen ions in the droplet can controllably regulate the self-assembly three-dimensional hotspot model of gold nanoparticles in the evaporation process of a droplet, during which the most enhancement effect can be easily captured. The dynamically changing images of nanoparticles in the process were graphically described based on the internal interaction forces of a droplet. Two stronger areas in the changes of SERS intensity were achieved with a high concentration of halogen ions, while only one maximum intensity area was obtained with a low concentration of halogen ions added. This method can effectively avoid complex and unpredictable microenvironments of SERS substrates in the liquid drop, further improving the reproducibility of SERS detection as well as broadening it to biological applications.

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.

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.

Lithium-ion batteries (LIBs) are widely adopted power sources for portable digital products and electrical vehicles (EV). However, the high cost associated with raw materials and manufacturing and ...

As fluorescence is the major limitation in Raman scattering, near-infrared excitation wavelength ( > 780 n m ) is preferred for fluorescence suppression in Raman spectroscopy. To reduce the risk of fluorescence interference, we developed a dual-wavelength excitation combined Raman spectroscopy (DWECRS) system at 785 and 830 nm. By a common optical path, each laser beam was focused on the same region of the sample by a single objective lens, and the dual-wavelength excitation Raman spectra were detected by a single CCD detector; in addition, 785 and 830 nm excitation Raman spectra can be directly constructed as combined Raman spectrum in the DWECRS system. The results of pure peanut oil and glycerol indicate that the combined Raman spectrum cannot only reduce fluorescence interference but also keep a high signal-to-noise ratio in the high-wavenumber region. The results of dye-ethanol solutions with different concentrations show that the handheld DWECRS system can be used as a smart method to dodge strong fluorescence. Furthermore, we developed a peak intensity ratio method with the DWECRS system to distinguish different types of edible oils. The peak intensity ratio distribution chart of edible oils showed each oil normalized center was relatively independent and nonoverlapped, which can be used as the basis of edible oil classification analysis. In the future, the DWECRS system has potential to be used as a tool for more complex applications.

In recognition of the misuse risks of fentanyl, there is an urgent need to develop a useful and rapid analytical method to detect and monitor the opioid drug. The surface-enhanced shifted excitation Raman difference spectroscopy (SE-SERDS) method has been demonstrated to suppress background interference and enhance Raman signals. In this study, the SE-SERDS method was used for trace detection of fentanyl in beverages. To prepare the simulated illegal drug–beverages, fentanyls were dissolved into distilled water or Mizone as a series of test samples. Based on our previous work, the surface-enhanced Raman spectroscopy detection was performed on the beverages containing fentanyl by the prepared AgNPs and the SE-SERDS spectra of test samples were collected by the dual-wavelength rapid excitation Raman difference spectroscopy system. In addition, the quantitative relationship between fentanyl concentrations and the Raman peaks was constructed by the Langmuir equation. The experimental results show that the limits of quantitation for fentanyl in distilled water and Mizone were 10 ng/mL and 200 ng/mL, respectively; the correlation coefficients for the nonlinear regression were as high as 0.9802 and 0.9794, respectively; and the relative standard deviation was less than 15%. Hence, the SE-SERDS method will be a promising method for the trace analyses of food safety and forensics.

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.

To elucidate the relationship between the structure of ionic liquid (IL) and its enrichment ability to trace pesticides from an environmental water sample, a series of imidazole-based ILs were synthesized to extract four fungicides (boscalid, cyprodinil, fluazinam, and pyrimethanil) through an in situ ionic liquid dispersive liquid–liquid microextraction method. The results showed that aromatic heterocyclic monocation ionic liquids (MILs) had better extraction ability to fungicides than other three alicyclic heterocyclic MILs. Dication ionic liquids (DILs) with the four carbons at the side chain had better ability to extract fungicides than MILs, and DILs with a long bridge carbon chain had better recoveries of fungicides with low Kow values. The proposed method showed high mean enrichment factors and high recoveries of the fungicides from real water samples. The rules of the relationship between the structure of IL and enrichment ability are instructive to the application of ILs in pretreatment of comple...

In this study, a facile, ultrasensitive and interference-free method to detect cefalexin (CEX) was developed for the first time. This assay was carried out by covalently immobilizing cefalexin–ovalbumin (CEX–OVA) on high specific surface area amorphous nanoparticles of superparamagnetic iron oxide (SPIO). Here, the SPIO–CEX–OVA structure was rich in antibody domains for competitive immunological recognition to anti-CEX antibody and to AlexaFluor 488 labeled goat anti-mouse IgG. Compared with traditional laser induced fluorescence detection, the introduction of SPIO can preconcentrate analytes to reduce the detection limit and greatly shorten the assay time. A pulsed laser with higher peak energy was chosen as the excitation source for generating strong fluorescence signals and to improve sensitivity. The detection limit was 0.34 ng mL−1 with linearity in the range of 0.5 ng mL−1 to 50 ng mL−1, and the IC50 was 1.7 ng mL−1. The accuracy and reproducibility were determined by using spiked milk samples with three different concentrations of CEX (5, 20 and 50 ng mL−1). The recoveries of 85.2–111.4% were obtained with relative standard deviations of 5.3–9.1%, respectively. These results indicate that the method provides a pragmatic platform for convenient detection of small molecular residues due to its high sensitivity, selectivity and short assay time.

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 10(3)cfu/mL. The quantification limit was calculated to be 10(4)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.

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 × 102 to 8 × 106 copies per mL. The limit of detection is 8 × 102 copies per mL. Compared to conventional detecting methods such as those based on PCR, the method presented here is rapid, facile and very sensitive.

Clavibacter michiganensis subsp. nebraskensis (Cmn) and Pantoea stewartii subsp. stewartii (Pss) are two plant pathogens that can cause tremendous agricultural economic losses. This novel method based on microsphere immunoreaction was developed for the simultaneous detection of Cmn and Pss in maize. This multiplex method was constructed based on microsphere immunodetection with fluorescent labels such as quantum dots (QDs) and R-phycoerythrin (R-PE) for the detection of Cmn and Pss. Captured QDs and R-PE serve as signal reporters for fluorescent readout. The principle of this method is based on a sandwich immunoreaction. Cmn and Pss captured by the microspheres were detected using flow cytometry. The limit of detection of this method was 10 times lower than the enzyme-linked immunosorbent assay (ELISA), and its analysis time (1 h) was much shorter compared with ELISA (6-8 h). The method, which has been proven to be an effective approach to multiplex detection of plant bacteria (Cmn and Pss as models), not only increased the varieties but also improved the sensitivity. The microsphere immunoreaction provides a universal method for the multiplex determination of microbes because of its high sensitivity, specificity, and speed. In the future, the method will be more fully validated in vivo to detect diversiform bacteria.

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 (

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.

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.

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.

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.

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 a...

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 × 105. They were applied as substrates for SERS-based imaging of kidney cells.

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 × 104 at 1077 cm−1. 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.

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.

The authentication of olive oil and its adulteration with lower priced oils are still serious problems in the olive oil industry. In this study, a method based on the intensity ratio of the Raman spectroscopy vibration bands, especially on the intensity ratio of the cis ( ==C-H) and cis (C=C) bonds normalized by the band at 1441 cm(-1) (CH(2)), was established to authenticate genuine/fake olive oil. These intensity ratios of the vibration bands given in the form of a two-dimensional chart allow first the discrimination between the various grades of olive oil and the seed oils and then the detection of olive oil fraud by the line of y = 0.7, which is observed under most experiments and dot charts. This method can reliably distinguish the genuine olive oils from the olive oils containing 5% (volume percentage) or more of other edible oils, such as soybean oil, rapeseed oil, sunflower seed oil, or corn oil. Compared to the traditional principal component analysis method, this method is more intuitive, more precise, and easier to use. Moreover, this method also has the advantages of simplicity efficiency and has no need for sample preprocessing, being especially suitable for on-site testing in field applications.

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 0.01 ng/mL with dynamic range of 0.01–100 ng/mL, and the concentration of clenbuterol providing 50% inhibition (IC 50 ) is 1.1 ng/mL. The main advantages of this method are its high efficiency, biocompatibility, and selectivity, as well as ultralow trace sample consumption and low cost.