This work reports the first preparation and characterization of a hybrid PbS quantum dot (QD)/nanoporous NiO film nanostructure as well as its application for novel self-powered cathodic photoelectrochemical (PEC) sensing. Specifically, we synthesized the thioglycolic acid-capped PbS QDs and then assembled them onto the hydrothermally fabricated three-dimensional (3D) NiO nanostructured films on the transparent indium tin oxide-coated glass substrates, followed by the subsequent conjugation with the glucose oxidase as a model biocatalyst. Favorable alignment existed between the NiO and PbS QDs, and the as-obtained p-type heterostructure was characterized by various techniques and found to have good PEC activities. In the self-powered PEC biosensing of glucose, the system exhibited high sensitivity toward the presence of dissolved oxygen in the electrolyte, and thereby, a novel PEC enzymatic sensor was developed. With a PbS QD/3D NiO nanofilm, this work manifested the great promise of a heterostructure photocathode for a self-powered PEC biosensor that to the best of our knowledge has not been reported. We believe that it could inspire more interest in the design and development of numerous other p-type heterostructures for advanced self-powered PEC biosensors.

The reaction between MO and NaBH4 catalyzed by Ag NPs has been studied. Ag NPs catalyzed the reduction of MO rapidly, while adding CTAB into the solution caused the regeneration of MO. Thus, reversible catalysis for the reaction between MO and NaBH4 by Ag NPs was discovered for the first time.

•Enhancing the fluorescence intensity of copper nanoclusters by melamine has been illustrated.•New method for melamine detection by copper nanoclusters as fluorescence probe was developed.•Melamine in milk samples was determined with excellent recoveries using this method.In this work, poly-thymine stabilized copper nanoclusters have been used as a fluorescence probe for melamine sensing for the first time. Melamine can bind to thymine through hydrogen bond, which could dramatically enhance the fluorescence intensity of poly-thymine stabilized copper nanoclusters. The enhancement factors (I−I0)/I0 increase linearly with the lgCmelamine over the melamine concentration range of 0.1 µM to 6 µM. The detection limit of melamine is 95 nM, which is 200 times lower than the US Food and Drug Administration estimate melamine safety limit 20 µM. Melamine in milk was detected with good recovery, which suggested that this novel fluorescence probe has great potential in practical application.A novel melamine sensing method based on the fluorescence enhancement of poly-thymine stabilized copper nanoclusters.

A rapid and low-cost colorimetric method for detection of quaternary ammonium surfactants using citrate-stabilized AuNPs based on the hydrophobic effect was developed. The LODs of different surfactants ranged from 0.5 μM to 5 μM.

•A rapid, sensitive and low-cost colorimetric method for detection of quaternary ammonium surfactants using citrate-capped Ag NPs was developed.•The Ag nanoparticles' aggregation is induced by the hydrophobic interaction.•The response of Ag NPs upon the addition of different cationic surfactants with different lengths of the alkyl chain is different.•This method was successfully utilized to analyze the disinfectant residual sample.In this work, a rapid, sensitive and low-cost colorimetric method for detection of quaternary ammonium surfactants using citrate-capped silver nanoparticles (Ag NPs) was developed. The quaternary ammonium surfactants induce the aggregation of Ag NPs through the hydrophobic effect, which is a novel aggregation mechanism of Ag NPs. The addition of cationic surfactant results in color change of Ag NPs solution from yellow to red and finally to colorless, which is due to the broadening of the surface plasmon band. The color change was monitored using a UV–vis spectrophotometer. The LOD of different cationic surfactants was in the range of 0.5–5 µM. More importantly, this detection method was successfully utilized to the disinfectant residual sample.

Photolithography was used to pattern hydrophobic design on common quantitative filter paper, and then the paper-based micro-zone plates were successfully fabricated. In order to improve its protein-adsorbing capacity for further signal magnification, modified silicon dioxide (SiO2) micro-beads were deposited onto the surface of paper. Indirect-ELISA for goat anti-rabbit IgG was realized on the 36-zone plates. Taking enzyme-linked goat anti-rabbit IgG as an example, loading SiO2 beads could remarkably increase the quantity of the adsorbed protein by 20%–700%. When this method was used for goat anti-rabbit IgG detection, signals were magnified by 20%–150%, and the linear range of detection was from 3 × 10−12 mmol to 3 × 10−8 mmol per zone. In this manner, bio-reagent consumption was reduced to 3–5 μL per zone, test time dropped to 25 min per plate and the cost of fabrication was reduced to $1.1 per plate. This work suggests a new way for development of new diagnosis devices.Filter paper was impregnated with SU-8 photoresist, and then was baked in oven after spanning off redundant photoresist. The paper plate was exposed to UV light through a transparent PVC mask and baked another time. After that, it was developed, washed and allowed to dry to form desired pattern.

Mesoporous SBA-15 silica particles were prepared in 1.6 M HCl with triblock copolymer Pluronic P123 (poly(ethyleneglycol)-block-poly(propyleneglycol)-block-poly(ethyleneglycol)) as the templating agent. Characterization shows that it has a highly ordered hexagonal mesoporous structure running along the same direction, extremely narrow pore size distribution (5.8 nm) and high surface areas (799 m2 g−1). The SBA-15 particles were successfully employed for the normal-phase chromatography separation of six Vitamin E isomers (mobile phase: n-hexane/ether (97/3, V/V); flow-rate: 2.0 mL min−1). The results show that α-, β-, γ-, δ- tocotrierols and α-, β- tocotrienols are base-line separated.

Microfluidic enzyme-based reactor could be used to detect biomolecules with high sensitivity and selectivity. Based on the electrophoretic-mediated microanalysis (EMMA) method, a novel free enzyme-based microchip was developed to detect glucose. Online catalysis reaction of glucose by glucose oxidase was carried out on the chip. The product H2O2 was detected using amperometric method. The working electrode, single carbon fibre cylindrical electrode, was held at a constant potential of +1.4 V versus Ag/AgCl electrode. The results indicated that the peak current had a good linear relationship with glucose concentration in the range of 0.1–20 mM (R = 0.997) with good reproducibility (RSD = 2.02%, n = 10). The detection limit of glucose was 19.8 μM (S/N = 3). This free enzyme-based reactor was easy to fabricate and operate, which showed great potential application in bioanalysis.

A rapid and low-cost colorimetric method for detection of quaternary ammonium surfactants using citrate-stabilized AuNPs based on the hydrophobic effect was developed. The LODs of different surfactants ranged from 0.5 μM to 5 μM.

The reaction between MO and NaBH4 catalyzed by Ag NPs has been studied. Ag NPs catalyzed the reduction of MO rapidly, while adding CTAB into the solution caused the regeneration of MO. Thus, reversible catalysis for the reaction between MO and NaBH4 by Ag NPs was discovered for the first time.