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A novel colorimetric sensing method for glucose was developed based on the catalytic activity of Au nanoparticles (NPs) and a synthetic cyclic peptide that specifically binds with glucose. It is the first time that a cyclic peptide was used as a recognition element for glucose sensing. In the absence of glucose, the monolayers of cyclic peptide on the Au NP surfaces interfered little with the adsorption of 4-nitrophenol, and the Au NPs catalyze the reduction of bright yellow 4-nitrophenol to colorless 4-aminophenol in the presence of NaBH4. Added glucose was preferentially bound by the cyclic peptides and impeded the adsorption of 4-nitrophenol. Therefore, the color of the solution presented varying shades of yellow depending on the concentration of glucose. The method had a short response time of 10 min and demonstrated a linear response over a range of glucose concentrations from 0.1 mM to 20 mM, with a lower limit of detection of 0.04 mM. Meanwhile, it also provided results readily observable by the naked eye. The method was successfully applied for the detection of glucose in spiked food samples (Chinese cabbage, pear, and wheat flour) and spiked rabbit blood, and a good recovery rate of 88.04–103.28% and 94.27–101.53% was obtained, respectively. [ABSTRACT FROM AUTHOR]

Saxitoxin (STX) as one of the most harmful and typical paralytic shellfish toxins, is posing a serious threat to environmental and human health, thus it is essential to develop a sensitive and reliable analytical method for STX detection. Herein, we proposed a strategy for rapid and sensitive detection of STX with surface-enhanced Raman spectroscopy (SERS), by employing cysteine modified gold nanoparticles (Cys-AuNPs) as SERS probe to capture STX molecules through electrostatic interactions and multiple hydrogen bonds between Cys and STX molecules. Moreover, the XPS and zeta potential results indicated that Cys could bond to AuNPs through Au-S bonds and the addition of STX could induce the efficient aggregation of Cys-AuNPs owing to the presence of electrostatic interactions and multiple hydrogen bonds between Cys and STX molecules. Furthermore, considering the high sensitivity and stability of the dynamic surface-enhanced Raman spectroscopy (D-SERS) strategy with the formation of a 3D hotspot matrix, the highly sensitive detection of STX was realized to a level of 1 × 10−7 M by using the D-SERS strategy. Consequently, Cys-AuNPs as high affinity substrates can provide high sensitivity for the detection of STX through the D-SERS strategy. [ABSTRACT FROM AUTHOR]

A colorimetric microplate assay for determination of Staphylococcus aureus DNA is described. Linear padlock probes were designed to recognize target sequences. After DNA binding, the linear padlock probes were circularized by ligation and then hybridize with biotin-labeled capture probes. Biotin-labeled capture probes act as primers to initiate the RCA. The biotin-labeled RCA products hybridize with digoxin-labeled signal probes fixed on streptavidin-functionalized wells of a 96-well plate. To enhance sensitivity, an AuNP-anti-digoxigenin-POx-HRP conjugate was added to the wells and then bound to digoxin-labeled signalling probes. The oxidation of tetramethylbenzidine (TMB) by H2O2 produces a color change from colorless to blue via HRP catalysis. After the reaction was terminated, absorbance is measured at 450 nm. For target sequences of Staphylococcus aureus, the detection limit is 1.2 pM. For genomic DNA, the detection limit is 7.4 pg.μL−1. The potential application of the method was verified by analyzing spiked food samples. [ABSTRACT FROM AUTHOR]

Abstract For the determination of dopamine (DA) in serum samples, a quenching-type electrochemiluminescence sensor (MIECLS) was constructed in this study. Upconversion nanoparticles (UCNPs) enhanced by covalent organic frameworks (COFs)-based hybrid and oligoaniline-crosslinked gold nanoparticles (AuNPs) imprinting recognition sites were introduced in electrochemiluminescence (ECL) system at the first time. The porous COFs-based hybrid with large specific surface area was modified on the electrode firstly to hold more UCNPs and imprinting recognition sites. AuNPs was employed in the developed sensor for two objectives: 1) AuNPs on the COFs-based hybrid enabled the hybrid to tunnel the electrons, which helped to improve the ECL intensity; 2) AuNPs-based thioaniline units (PATP@AuNPs) electropolymerized on the electrode in the presence of template to form oligoaniline-crosslinked AuNPs matrix. Then the exclusion of template from matrix yielded the molecularly three-dimensional imprinted contours with conductivity, which facilitated specific recognition and further amplified the ECL. The double recognition mode in this work involves the recognition effect of imprinted contours and quenching effect of o -benzoquinone species. The quantum chemical calculation was performed to analyze the possible recognition and the binding mechanisms of molecularly three-dimensional imprinted contours. The results showed imprinted contours could bind the targets by complementary spatial cavities and weak interactions. The proposed approach yielded a wide detection range (10–14–10−6 M), low limit of detection (LOD = 2 ×10–15 M) and acceptable recoveries (93.25–112.97%) in rat serum sample, demonstrating that the developed method holds great promise to be applied to DA detection in practical samples. Highlights • CTpBD-Au enhanced UCNPs and oligoaniline-crosslinked AuNPs imprinting recognition sites were introduced in ECL system. • The double recognition was constructed by the recognition effect of imprinted contours and quenching effect for ECL. • The proposed approach yields a wide detection range, low limit of detection and acceptable recoveries in rat serum sample. [ABSTRACT FROM AUTHOR]

• A QCM sensor based on AuNPs doped molecularly imprinted layer and COFs-AuNPs composite was developed. • The sensitive and selective detection was attributed to the employment of COFs-AuNPs and crosslinked imprinting recognition sites. • The COFs-AuNPs composite and three-dimensional structure of imprinted matrix provided more recognition sites for sensing. In this study, for the first time a quartz crystal microbalance (QCM) sensor based on gold nanoparticles (AuNPs) doped molecularly imprinted layer and covalent organic frameworks composite (COFs-AuNPs) was developed for the detection of aflatoxin B1. The AuNPs doped molecularly imprinted layer involved in the crosslinking of o- aminothiophenol functionalized AuNPs (o- ATP@AuNPs) in the present of the templates on electrode surface. The imprinting recognition sites obtained by eluting the templates from imprinted polymer of poly(o- ATP) with AuNPs formed the specific three-dimensional imprinted contours toward the targets. A kind of porous lightweight material–CTpBD COFs and AuNPs were employed jointly to yield the COFs-AuNPs composite which provided large surface area for o- ATP@AuNPs crosslinking. The introduction of COFs-AuNPs substrate and three-dimensional structure of imprinted matrix endowed the sensor with more recognition sites. The sensitive and selective detection was attributed to the loading capacity of the COFs-AuNPs composite and the specific recognition effect of molecularly imprinted polymer of poly(o- ATP) with AuNPs. Under optimal conditions, the proposed sensor showed a wide linear range from 0.05 to 75 ng mL−1, low limit of detection (LOD = 2.8 pg mL−1) and the acceptable recoveries (87.0%−101.7%) in real samples analysis. [ABSTRACT FROM AUTHOR]

[Display omitted] • AuNPs and PANI were modified to the electrode by electropolymerization. • The AuNPs acted as luminophore and also made antibodies immobilizing. • PANI with porous structure synergically amplify AuNPs luminophore signal. • The fabricated ECL sensor exhibited good selectivity and sensitivity towards 3-NT. As an appropriate biomarker for oxidative stress, 3-nitrotyrosine (3-NT) in biological samples is associated with many neurodegenerative disorders and inflammatory diseases. Herein, a novel and rapid electrochemiluminescence (ECL) immunosensor was successfully fabricated for ultrasensitive detection of 3-NT. Electrodeposited gold nanoparticles (AuNPs) being used as the luminophore and polyaniline being electropolymerized to promote the luminescence of AuNPs, a stable and efficient ECL system was obtained with an ECL intensity 28 times higher than that of bare electrodes. Taking advantage of the good biocompatibility and large specific surface area of AuNPs, the antibody was effectively immobilized on the electrode, achieving high selectivity for 3-NT detection. Under the optimal conditions, the immunosensor exhibited good analytical performance for 3-NT with a wide linear detection in the range of 1 × 10−11–1 × 10−8 mol/L and a low detection limit of 2.57 × 10−12 mol/L. Furthermore, the established sensor had a high recovery rate (85.29%–103.94%) in practical sample applications. The sensor had simple preparation method, high sensitivity and good stability, providing a promising sensing platform for the detection of 3-NT. [ABSTRACT FROM AUTHOR]

Luminescent down-shifting (LDS) is a spectral conversion method for improving the short-wavelength response of Si-based solar cell by transforming shorter wavelength (200 nm-400 nm) into longer wavelength (>400 nm). In this paper, LDS efficiency was enhanced through incorporating Ag nanoparticles into ZnSe/ZnS quantum dots (QDs), as demonstrated by photoluminescence (PL) spectra and finite-difference time-domain (FDTD) simulation results. The mixed Ag/ZnSe/ZnS QDs were spin-coated on the surface of manufactured Si-solar cell so as to efficiently utilize LDS properties. The external quantum efficiency (EQE) and short-circuit current density (Jsc) of Ag/ZnSe/ZnS QDs–Si hybrid solar cell were respectively increased by 30% and 7.5% compared to those of ZnSe/ZnS–Si hybrid solar cell. These improvements were mainly ascribed to localized surface plasmonic (LSP) enhancement effect of Ag nanoparticles. Such small but distinct improvements are expected to provide the theoretical basis and technical support for the development of photovoltaic devices in the future. [ABSTRACT FROM AUTHOR]

• Cu 2-x Se-Au with 60.78% photothermal conversion efficiency was synthesized. • A new photothermal immunosensing probe was prepared. • IC 15 of photothermal immunochromatographic sensor for aflatoxin B1was 0.00842 μg/L. • The detection ranging to analysize grain sample is from 0.16 to 160μg/kg. In the study, Cu 2-x Se-Au nanoparticles (CSA) with a photothermal conversion efficiency of 60.78 % at 808 nm were applied to the construction of thermal analysis immunochromatographic test strips for the highly sensitive quantitative detection of aflatoxin B 1 (AFB 1) in grain. The CSA was coupled with the AFB 1 antibody to form a photothermal sensor probe by physical adsorption. The constructed immunosensor exhibited high sensitivity and a wide linear range from 0.01 to 10 μg/L in PBS. The detection limits of 0.00842 μg/L based on the thermal analysis was significantly improved by 11.88-fold compared with colorimetric results. No cross-reaction with the other mycotoxins was found except for aflatoxin B 2 , aflatoxin M 1 , aflatoxin G 1 and aflatoxin G 2. Applied to analysize grain sample, the method achieved the detection of AFB 1 ranging from 0.16 to 160 μg/kg. [ABSTRACT FROM AUTHOR]

A bimodal 3D-electrochemiluminescence (ECL) analysis method was developed, which integrated simpleness, label-free, high-throughput and real time detection together. Firstly, a novel 3D copper-based nanosheet micro-material (Cu-Flo. NMs) coupled with gold nanoparticles/Cysteine (Cu-Flo.@AuNPs-Cys) was prepared to use as the versatile label for both colorimetric and ECL techniques. The 3D-Cu-Flo.@AuNPs-Cys having glucose oxidase-like activity could catalyze glucose to produce H 2 O 2 in situ, which was further found to be capable of exhibiting a 30.95-fold higher ECL-intensity for luminol than bare glassy carbon electrodes (GCE). Taking advantages of the 3D-Cu-Flo.@AuNPs-Cys above, a colorimetric and ECL-channel sensor (GCE/3D-Cu-Flo.@AuNPs-Cys) were constructed simultaneously for glucose detection. The fabricated sensor displayed a wide linear range (Glucose: 0.001–50 mmol L−1, AFP: 2.25 × 10−7–225 ng mL−1), impressive low limit of detection (Glucose: 1.27 × 10−7 mol L−1, AFP: 1.92 × 10−8 ng mL−1, S/N = 3) and acceptable recovery (Glucose: 94% ∼ 104%, AFP: 96.04% ∼ 102.29%) in practical sample. Furthermore, the biosensor showed ultrafast (0.5 min) analysis efficiency, high stability for 6 cyclic potential scans and satisfactory reproducibility for 7 repeated tests. These results demonstrated the proposed 3D dual-modal ECL-biosensor for biomarkers detection had a great potential in clinical diagnostics, promoting the application in biomedical researching and POCT. [Display omitted] 1 A novel hybrid 3D copper-based nanomaterial (Cu-Flo.) coupled with gold nanoparticles (Cu-Flo.@AuNPs) was realized excellent catalytic-ability towards glucose. 2. Colorimetric and electrochemiluminescence (ECL) bioassays were performed based on the in-situ H 2 O 2 -generation luminol-system. 3. The blocking and direct catalytic assays showed an ultra-sensitivity for AFP and glucose detection simultaneously. 4. A promising nanozyme Cu-Flo. NMs overcomed the disadvantage of low-durability and instability for natural enzyme. [ABSTRACT FROM AUTHOR]