In this study, we design a FRET system consisting of gold nanorod (AuNR) and quantum dots (QDs) for turn-on fluorescent sensing of 2,4,6-trinitrotoluene (TNT) in near-infrared region. The amine-terminated AuNR and carboxyl-terminated QDs first form a compact hybrid assembly through amine-carboxyl attractive interaction, which leads to a high-efficiency (>92%) FRET from QDs to AuNRs and an almost complete emission quenching. Next, added TNT molecules break the preformed assembly because they can replace the QDs around AuNRs, based on the specific reaction of forming Meisenheimer complexes between TNT and primary amines. Thus, the FRET is switched off, and a more than 10 times fluorescent enhancement is obtained. The fluorescence turn-on is immediate, and the limit of detection for TNT is as low as 0.1 nM. Importantly, TNT can be well distinguished from its analogues due to their electron deficiency difference. The developed method is successfully applied to TNT sensing in real environmental samples.

The incorporation of oxygen vacancies in hematite has been investigated as a promising route to improve oxygen evolution reaction activity of hematite photoanodes used in photoelectrochemical water oxidation. However, introducing oxygen vacancies intentionally in α-Fe2O3 for active solar water splitting through facile and effective methods remains a challenge. Herein, air plasma treatment is shown to produce oxygen vacancies in α-Fe2O3, and ultrathin α-Fe2O3 nanoflakes are used to investigate the effect of oxygen vacancies on the performance of photoelectrochemical oxygen oxidation. Increasing the plasma treatment duration and power is found to increase the density of oxygen vacancies and leads to a significant enhancement of the photocurrent response. The nanoflake photoanode with the optimized plasma treatment yields an incident photo-to-current conversion efficiency of 35.4% at 350 nm under 1.6 V vs RHE without resorting to any other cocatalysts, an efficiency far exceeding that of the pristine α-Fe2O3 nanoflakes (∼2.2%). Evidence for the presence of high density of oxygen vacancies confined in nanoflakes is clarified by X-ray photoelectron spectroscopy. The increased number of oxygen vacancies after plasma treatment resulting in an increased carrier density is interpreted as the main cause for the enhanced oxygen evolution reaction activity.

In this study, a novel Au nanocluster (NC)-based fluorescent sensor has been designed for near-infrared (NIR) and turn-on sensing of glutathione (GSH) in both living cells and human blood samples. The large Stokes-shifted (140 nm) fluorescent Au NCs with NIR emission and long-wavelength excitation have been rapidly synthesized for 2 h by means of a microwave-assisted method in aqueous solution. The addition of Hg(II) leads to an almost complete emission quenching (98%) of Au NCs because of the interaction of Hg(II) and Au(I) on the surface of Au NCs. After introducing GSH to the Au NC-Hg(II) system, a more than 20 times fluorescent enhancement is obtained because of the preferable affinity of GSH with Hg(II). Under optimum conditions, the fluorescence recovery is linearly proportional to the concentration of GSH between 0.04 and 16.0 μM and the detection limit is as low as 7.0 nM. This Au NC-based sensor with high sensitivity and low spectral interference has been proven to facilitate biosensing applications.

Campylobacter jejuni is a leading human food-borne pathogen. The rapid and sensitive detection of C. jejuni is necessary for the maintenance of a safe food/water supply. In this article, we present a real-time polymerase chain reaction (PCR) assay for quantitative detection of C. jejuni in naturally contaminated poultry, milk and environmental samples without an enrichment step. The whole assay can be completed in 60 min with a detection limit of approximately 1 CFU. The standard curve correlation coefficient for the threshold cycle versus the copy number of initial C. jejuni cells was 0.988. To test the PCR system, a set of 300 frozen chicken meat samples, 300 milk samples and 300 water samples were screened for the presence of C. jejuni. 30.6% (92/300) of chicken meat samples, 27.3% (82/300) of milk samples, and 13.6% (41/300) of water samples tested positive for C. jejuni. This result indicated that the real-time PCR assay provides a specific, sensitive and rapid method for quantitative detection of C. jejuni. Moreover, it is concluded that retail chicken meat, raw milk and environmental water are commonly contaminated with C. jejuni and could serve as a potential risk for consumers in eastern China, especially if proper hygienic and cooking conditions are not maintained.