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This study aimed to establish a detection platform for ochratoxin A (OTA), a common mycotoxin contaminant of various food products. The detection platform is based on signal amplification by Exonuclease III (Exo III) and fluorescence quenching by gold nanoparticles (AuNPs). The aptamer recognizes and binds to OTA, thus leading to the formation of duplex DNA between the complimentary DNA (cDNA) strand and the signal probe. Exo III then digests the duplex DNA from the 3′ blunt terminus of the signal probe to liberate the fluorophore and release cDNA. The released cDNA then hybridizes with other signal probes to initiate a new cleavage reaction. Through this cyclic hybridization–hydrolysis process, an OTA molecule can trigger the cleavage of a large quantity of signal probes. Upon the addition of AuNPs, the fluorophore cannot be adsorbed and quenched, thus notably amplifying fluorescence. The designed aptasensor is highly selective for OTA with a low limit of detection (4.82 nM). The feasibility of the detection procedure and the applicability of the aptasensor were validated through the detection of OTA in spiked red wine without interference from the sample matrix. Results indicated that the aptasensor could be used to verify the effectiveness of mycotoxin-control strategies. [ABSTRACT FROM AUTHOR]

Reduced graphene oxide (rGO) decorated TiO 2 microspheres are prepared by using the hydrothermal method. The as-synthesized sample shows that TiO 2 particles are connected by the rGO nanosheets while some TiO 2 particles are found to be partly covered by rGO sheets. The rGO-decorated TiO 2 based chemoresistive-type sensor shows good sensitivity and excellent selectivity to different concentrations of ammonia from 5 ppm to 50 ppm at room temperature. However, the response and recovery speeds of the sensor to ammonia are sluggish and need further optimization. [ABSTRACT FROM AUTHOR]

• Ag 2-x Cu x S nanoparticles exhibit tandem enzyme-like activity (glucose oxidase-like activity and peroxidase-like activity). • Photothermal effect enhances the tandem enzyme-like activity to ∼10 times. • A one-step enzyme-free colorimetric glucose detection in unprocessed human urine is achieved. It is greatly significant and difficult to realize the purpose of natural enzyme free and "one-step" for traditional colorimetric urine glucose detection. Here, ultra-small Ag 2-x Cu x S nanoparticles (NPs) with tandem enzyme-like activity, i.e. they simultaneously exhibit glucose oxidase (GOx)- and peroxidase-like activities, are developed for tandem glucose oxidation and colorimetric H 2 O 2 detection. Cu doping content has a great influence on the enzyme-like activity. Ag 1.8 Cu 0.2 S NPs (i.e. Ag 2-x Cu x S NPs with 10 % Cu) exhibit the best catalytic performance. The tandem enzyme-like activity can be further enhanced to ∼10 times under laser irradiation due to photothermal effect. Furthermore, accurate glucose detection has been realized in unprocessed human urine based on the photothermal-enhanced tandem enzyme-like activity of Ag 1.8 Cu 0.2 S NPs. This natural enzyme free and "one-step" colorimetric glucose detection strategy exhibits the potential application of the new generation of tandem enzyme-like nanomaterials. [ABSTRACT FROM AUTHOR]

SnS 2 nanosheets decorated with SnO 2 nanocomposites have been successfully prepared by in-situ high-temperature oxidizing pristine SnS 2 in air at 300 °C. The formed SnO 2 /SnS 2 heterojunction based chemiresistive gas sensor exhibits an excellent sensitivity and selectivity to different concentrations of NO 2 from 1 ppm to 8 ppm at 80 °C. The higher response of the as-fabricated SnO 2 /SnS 2 heterojunction based sensor to NO 2 compared with that of the pure SnS 2 based one could be attributed to the extra charge transfer between SnO 2 /SnS 2 interfaces. [ABSTRACT FROM AUTHOR]

Increasing the aspect ratio of the microchannels of microfabricated gas chromatographic columns (μGCCs) can allow analytes to quickly reach equilibrium between the stationary phase and mobile phase, which helps improve their separation performance. In this paper, an all-silicon microfabricated gas chromatographic column (AS-μGCC) with a high aspect ratio was proposed and fabricated using deep reactive-ion etching (DRIE) and silicon direct bonding. Two AS-μGCCs with the lengths of 2 m and the aspect ratios of 6.6 (100 µm-width × 660 µm-depth) and 25 (30 µm-width × 750 µm-depth) were successfully fabricated. The effects of different aspect ratios on the column efficiency of AS-μGCCs were studied. A separation experiment showed that the column efficiency of the AS-μGCC with an aspect ratio of 25 (AS-μGCC-25) was 12 times higher than that of the AS-μGCC with an aspect ratio of 6.6 (AS-μGCC-6.6). The column efficiency of the AS-μGCC-25 was 1961 plates/m, and a heavy hydrocarbon mixture (C8–C20) could be separated using AS-μGCC-25 within 4.5 min [Display omitted] • Two all-silicon microfabricated gas chromatographic columns with aspect ratios of 25 and 6.6 were fabricated. • The AS-μGCC-25 showed a 12-fold improvement in the column efficiency as compared to the AS-μGCC-6.6. • By optimizing the conditions of the temperature programming, C8–C20 could be separated using AS-μGCC-25 within 4.5 min. [ABSTRACT FROM AUTHOR]

Highlights • Au/Cu NRs exhibit high peroxidase-like properties when Cu2+ ions were chosen to induce Au NRs to form high-index {200} facet. • The catalytic activity of Au/Cu NRs was confirmed by the oxidation of colorless 3,3',5,5'-tetramethylbenzidine (TMB) to blue oxidized TMB by H 2 O 2. • The colorimetric method for detecting AA has been developed based on the peroxidase-like activity of Au/Cu NRs. Abstract Creating high-index facet gold nanorods (Au NRs) is important for catalytic application. The high-index facet exhibits tremendously catalytic activity comparing with low-index facet. Herein, Cu2+ ions were chosen to induce Au NRs to form high-index {200} facet. Firstly, Au/Cu NRs with high-index facets induce high-density charge distribution at local position, which led to the surface enhanced Raman scattering enhancement. Furthermore, the active electrons transfer from Au/Cu NRs to H 2 O 2 make them show peroxidase-like properties. The catalytic activity of Au/Cu NRs was confirmed by the oxidation of colorless 3,3′,5,5′-tetramethylbenzidine (TMB) to blue oxidized TMB (oxTMB) by H 2 O 2. According to Michaelis-Menten equation, the catalytic activity of Au/Cu was higher than Au NRs by 4.5 times. Meanwhile, the oxTMB molecules may be deoxidized to TMB molecules by the antioxidant of ascorbic acids. On the basis of this phenomenon, the colorimetric determination of ascorbic acid in real samples (vitamin drink) was developed with a detection limit of 25 μM. [ABSTRACT FROM AUTHOR]