Yuanyuan Yao

Electrochemical recognition and trace-level detection of bactericide carbendazim using carboxylic group functionalized poly(3,4- ethylenedioxythiophene) mimic electrode

The electrochemical recognition and trace-level detection of bactericide carbendazim (MBC) in paddy water and commercial juice were realized using carboxylic group functionalized poly(3,4-ethylenedioxythiophene) (PC4-EDOT-COOH) film electrode. PC4-EDOT-COOH film was prepared by one step, low-cost, and green electrosynthesis in aqueous microemulsion system and characterized by FT-IR, cyclic voltammetry, UV-vis and SEM. In comparison with poly(3,4-ethylenedioxythiophene) (PEDOT) and poly(hydroxymethylated-3,4-ethylenedioxylthiophene) (PEDTM), PC4-EDOT-COOH exhibited the best electrochemical recognition towards MBC and the recognition mechanism was proved by quantitative calculation. Sensing parameters such as pH values, accumulation potential, accumulation time, supporting electrolyte, and scan rate on the current response of MBC were discussed. In addition, the sensor can be applied to quantification of MBC in the concentration range of 0.012-0.35 μM with a low detection limit of 3.5 nM (S/N=3). Moreover, PC4-EDOT-COOH film electrode showed good stability, high selectivity, and satisfactory anti-interference ability. Satisfactory results indicated that PC4-EDOT-COOH film is a promising sensing platform for the trace-level analysis of bactericide residue carbendazim in agricultural crops and environment.

High quality perovskite films fabricated from Lewis acid–base adduct through molecular exchange

We describe a facile method to fabricate high quality CH3NH3PbI3 films with smooth surface and without residual PbI2 through molecular exchange, rather than ionic intercalation. It forms a Lewis acid–base adduct of PbI2·xDMF when PbI2 precipitates from DMF solution. The lattice of PbI2 is expanded more than 30% due to the intercalation of DMF. With the lattice expansion, CH3NH3I (MAI) diffuses into the PbI2·xDMF lattice easily, and the PbI2·xDMF converts completely to CH3NH3PI3 by molecular exchange between DMF and MAI. The lattice volume changes little during the molecular exchange in PbI2·xDMF. Thus, it is easy to fabricate high quality perovskite films from the Lewis adduct of PbI2·xDMF. The perovskite solar cells fabricated from the Lewis adduct exhibit higher photovoltaic performance than those from the PbI2 films. This work reveals the important role of common solvent in controlling the quality of perovskite films.

Fabrication of high quality perovskite films by modulating the Pb–O bonds in Lewis acid–base adducts

High efficiency perovskite solar cells can be made through the Lewis adduct approach. The interaction between PbI2 and the Lewis base is a key factor to make high quality perovskite films. Here, we combine a two-step method with the Lewis adduct approach to fabricate high quality organometallic perovskite films by tuning the strength of the Pb–O bond in Lewis acid–base adducts via adding different Lewis base additives. By optimizing the strength of the Pb–O bond, smooth CH3NH3PbI3 films with large perovskite grains are prepared. The high quality CH3NH3PbI3 films lead to a low recombination rate, long carrier life time and highly efficient charge transfer process. As a result, the power conversion efficiency of the best perovskite solar cell increases from 12.79% to 17.26%.

Nickel clusters grown on three-dimensional graphene oxide–multi-wall carbon nanotubes as an electrochemical sensing platform for luteolin at the picomolar level

This study focuses on enhancing the catalytic activity of metallic Ni by using various nanostructured carbon materials, including 1D multi-wall carbon nanotubes (MWCNTs), 2D graphene oxide (GO) and graphene (GR), and 3D graphene oxide–multi-wall carbon nanotubes (GO–MWCNTs) as supporting matrices for the fabrication of an electrochemical sensor for detecting the flavonoid luteolin. Ni clusters were prepared by a facile electrochemical approach and the metallic Ni on various carbon supports exhibited different morphologies, which were characterized by scanning electron microscopy (SEM) and Raman spectra. The electrocatalytic performance of Ni-based materials towards luteolin oxidation was studied by cyclic voltammetry (CV) and differential pulse voltammetry (DPV). It was found that Ni clusters supported on GO–MWCNTs (Ni/GO–MWCNTs) were profoundly superior to other carbon materials, with a greatly enhanced current. This is attributed not only to the excellent electric conductivity and large surface-to-volume ratio of Ni/GO–MWCNTs, but also to the unique 3D carbon nanostructure that facilitates the easy access of the electrolyte and analyte to the modified electrode surface and promotes the reaction kinetics. Under the optimal conditions, the anodic peak current was linear to the concentration of luteolin in the range from 1 pM to 15 μM with a detection limit of 0.34 pM (S/N = 3). The good analytical performance, low cost and straightforward preparation method made this novel electrode material promising for the development of an effective luteolin sensor.

MOF-derived synthesis of mesoporous In/Ga oxides and their ultra-sensitive ethanol-sensing properties

A series of In/Ga-based MIL-68s, with batch molar ratios of In(III) to Ga(III) (In/Ga ratio) equaling 5 : 0, 4 : 1, 3 : 2, 1 : 1, 2 : 3, 1 : 4, and 0 : 5, were solvothermally prepared. Calcinating the as-prepared MOFs at 500 °C for 3 h produced a series of mesoporous In/Ga oxides (IGOs) of hexagonal morphology with a characteristic main pore radius of 3 nm to 12 nm, and a specific surface area of up to 60–135 m2 g−1. Studies on the ethanol gas-sensing properties of the as-prepared IGOs revealed that the two IGOs produced from MIL-68 with In/Ga ratios of 3 : 2 and 1 : 1 present high response values of 80–110 towards 300 ppm ethanol and a low detection limit of no more than 2 ppm. However, the response value of In2O3, produced from MIL-68 with an In/Ga ratio of 5 : 0, was 11 towards 300 ppm ethanol. At the same time, the two IGO samples exhibited a high response to ethanol, which was more than 2.6 times higher than response values towards CH3CHO, CH3COCH3, H2, CO, CH4, and NO2, at a concentration of 300 ppm. This gas-sensing performance is suggested to be attributed to their comparatively larger specific surface area, and remarkable oxygen vacancy capabilities.