No abstract

Trapped nanobubbles are gas domains trapped at nanopits on the solid−liquid interface. This is different from surface nanobubbles that usually form at the smooth surface. Herein, both trapped nanobubbles and surface nanobubbles formed on the nanopitted polystyrene film were studied by a spontaneous formation method and a temperature difference method. Trapped nanobubbles behave more flexibly than surface nanobubbles under different scanning loads. The nanopits under trapped nanobubbles appear after being subjected to large force scanning, and both trapped nanobubbles and surface nanobubbles can recover after reducing the scan load. The contact angles of the two kinds of nanobubbles were calculated and were found to be approximately constant. Configurations of trapped nanobubbles including under the pit mouth, protruding out but pinning at the pit mouth, and protruding out and extending around the pit mouth were experimentally observed. Gas oversaturation in the liquid after replacing the low-temperature water with high-temperature water was evaluated and was found to be a key factor for nanobubble formation and led to trapped nanobubbles protruding out and extending. Our study should be helpful in understanding the formation mechanism and properties of trapped nanobubbles and surface nanobubbles, and it will also be useful for further research on the control of nanobubble distribution.

A novel signal-amplified electrochemical assay for the determination of fenitrothion was developed, based on the redox behaviour of organophosphorus pesticides on a glassy carbon working electrode. The electrode was modified using graphene oxide dispersion. The electrochemical response of fenitrothion at the modified electrode was investigated using cyclic voltammetry, current-time curves, and square-wave voltammetry. Experimental parameters, namely the accumulation conditions, pH value, and volume of dispersed material, were optimised. Under the optimum conditions, a good linear relationship was obtained between the oxidation peak current and the fenitrothion concentration. The linear range was 1–400 ng·mL−1, with a detection limit of 0.1 ng·mL−1 (signal-to-nose ratio = 3). The high sensitivity of the sensor was demonstrated by determining fenitrothion in pakchoi samples.

The stable core–shell imprinted Ag-POPD/CoFe2O4 photocatalyst not only possessed high photocatalytic activity, but also exhibited the superior specific recognition capability for selective photodegradation of CIP.

We use the multiple antibiotic resistance regulator (MarR), as a highly selective biorecognition elements in a multipath colourimetric sensing strategy for the fast detection of Cu2+ in water samples. The colourimetric assay is based on the aggregation of MarR-coated gold nanoparticles in the presence of Cu2+ ions, which induces a red-to-purple colour change of the solution. The colour variation in the gold nanoparticle aggregation process can be used for qualitative and quantitative detection of Cu2+ by the naked eye, and with UV–vis and smartphone-based approaches. The three analysis techniques used in the multipath colourimetric assay complement each other and provide greater flexibility for differing requirements and conditions, making the assay highly applicable for Cu2+ detection. Under optimal conditions, the Cu2+ concentration was quantified in less than 5 min with limits of detection for the naked eye, UV–vis and smartphone-based approaches of 1 μM, 405 nM and 61 nM, respectively. Moreover, the sensing system exhibited excellent selectivity and practical application for Cu2+ detection in real water samples. Thus, our strategy has great potential for application in on-site monitoring of Cu2+, and the unique response of MarR towards copper ions may provide a new approach to Cu2+ sensing.