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Electrochemical CO2 reduction (CO2RR) to produce high value-added chemicals or fuels is a promising technology to address the greenhouse effect and energy challenges. Formate is a desirable product of CO2RR with great economic value. Here, nitrogen-doped bismuth nanosheets (N-BiNSs) were prepared by a facile one-step method. The N-BiNSs were used as efficient electrocatalysts for CO2RR with selective formate production. The N-BiNSs exhibited a high formate Faradic efficiency (FEformate) of 95.25% at −0.95 V (vs. RHE) with a stable current density of 33.63 mA cm−2 in 0.5 M KHCO3. Moreover, the N-BiNSs for CO2RR yielded a large current density (300 mA cm−2) for formate production in a flow-cell measurement, achieving the commercial requirement. The FEformate of 90% can maintain stability for 14 h of electrolysis. Nitrogen doping could induce charge transfer from the N atom to the Bi atom, thus modulating the electronic structure of N-Bi nanosheets. DFT results demonstrated the N-BiNSs reduced the adsorption energy of the *OCHO intermediate and promoted the mass transfer of charges, thereby improving the CO2RR with high FEformate. This study provides a valuable strategy to enhance the catalytic performance of bismuth-based catalysts for CO2RR by using a nitrogen-doping strategy. [ABSTRACT FROM AUTHOR]

Molybdenum disulfide quantum dots (MoS2 QDs) are used in a fluorometric method for the determination of folic acid (FA) based on fluorescence quenching. The MoS2 QDs synthesized by a hydrothermal method possess bright blue fluorescence (with excitation/emission maxima of 325/415 nm), quantum yield of 3.7%, and excellent storage stability in solution (30 days in the refrigerator). Their fluorescence is quenched by FA, and intensity decreases linearly in the 0.1 to 125 μM FA concentration range. The detection limit is 0.1 μM (at S/N = 3), and the relative standard deviation (for n = 5) is 2.8% for 25 μM concentrations of FA. Studies on the quenching mechanism suggest that the effect is due to static quenching. The FA in commercial FA tablets was successfully determined. [ABSTRACT FROM AUTHOR]

Abstract: A novel electrogenerated chemiluminescence (ECL) aptamer-based biosensing method for the determination of thrombin was developed on basis of a structure-switching ECL-dequenching mechanism. A thiolated ss-DNA capture probe, composing of a ss-DNA sequence to adopt two distinct structures-a DNA double strand with a complementary DNA sequence tagged with a ECL signal producer tris(2,2′-bipyridyl)ruthenium derivative and a DNA duplex with a thrombin-binding aptamer tagged with a ECL-quencher ferrocene (FcDNA), was self-assembled onto surface of a gold electrode. In the presence of thrombin, the aptamer sequence prefers to form the aptamer-thrombin complex and the switch of the binding partners occurs in conjunction with the generation of a strong ECL signal owing to the dissociation of FcDNA. The integrated ECL intensity versus the concentration of thrombin was linear in the range from 2.0×10−10 M to 2.0×10−7 M. The detection limit was 6×10−11 M. The relative standard derivation for 2.0×10−9 M was 5.7% (n =7). This work demonstrates that the sensitivity and specificity of ECL aptamer-based method for proteins can be greatly improved using quenching ECL signal producer by a chemical quencher such as ferrocene. [Copyright &y& Elsevier]

In this work, a H-type hydroquinone/O 2 fuel cell was assembled and shows high energy density in neutral phosphate buffer solution at moderate temperature. The anodic material, Ni(OH) 2 /MWCNTs, was synthesized by a one-step hydrothermal synthesis method to oxidize hydroquinone. The cathode material, Pt/MWCNTs, was obtained by an electrodeposition method, and shows great oxygen reduction reaction (ORR) activity. The properties and the morphology of Ni(OH) 2 /MWCNT nanocomposites were characterized by TEM, XPS, EDS-mapping and electrochemical methods, like cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS). The results show that Ni(OH) 2 /MWCNTs can effectively oxidize hydroquinone and play a dominant role in enhancing the fuel cell performance. The nonenzymatic fuel cell possesses a high power density of 0.24 mW cm -2 at a cell potential of 0.49 V., Competing Interests: There are no conflicts of interest to declare., (This journal is © The Royal Society of Chemistry.)

Iron can enter the electron-rich cavities of graphitic carbon nitride (g-C 3 N 4 ). On account of this phenomenon, Fe-doped g-C 3 N 4 (Fe-g-C 3 N 4 ) was prepared as a peroxidase mimetic by using one-step pyrolysis of urea and FeCl 3 ·6H 2 O. Compared to g-C 3 N 4 , Fe-g-C 3 N 4 has a large specific surface area due to the presence of mesopores and cracks, a smaller band gap, and a high loading of Fe in its structure. Thus, Fe-g-C 3 N 4 exhibits greater peroxidase activity with a more obvious color change when using 3,3',5,5'-tetramethylbenzidine (TMB) as a substrate in the presence of hydrogen peroxide (H 2 O 2 ). The color of a mixture of TMB and Fe-g-C 3 N 4 gradually deepens with increasing concentrations of H 2 O 2 . Accordingly, a rapid, sensitive, and low-cost colorimetric assay for the detection of H 2 O 2 was developed. After optimization, this method boasts a wide linear dynamic range for H 2 O 2 detection from 0.005 to 400 μM ( r 2 = 0.9971) with a detection limit of 0.005 μM. Because H 2 O 2 is a main product of glucose oxidation by glucose oxidase (GOx), a colorimetric assay for glucose detection was also realized, with a linear dynamic range of 1-1000 μM ( r 2 = 0.9996) and a detection limit of 0.5 μM. These assays were applied to the quantitative detection of H 2 O 2 in milk and glucose in human serum, respectively.