Dual-monomer molecularly imprinted electrochemical sensor based on amino-functionalized MOFs and graphene for trace determination of taurine.

A molecularly imprinted electrochemical sensor (MIECS) for trace determination of taurine was developed. The sensor was constructed by electropolymerizing dopamine and o-phenylenediamine as dual monomers on the surface of amino-functionalized iron-based MOFs and graphene composite-modified electrode. The porous structure and large specific surface area of amino-functionalized iron-based MOFs not only increase the number of imprinted sites, but also facilitate the binding of molecularly imprinted films. The presence of dual monomers can increase the binding sites during the formation of imprinted films. The linear range of this sensor for taurine detection is 1.00 × 10-14-1.00 × 10-8 mol L-1 with a determination limit of 3.20 × 10-15 mol L-1. The proposed MIECS was successfully applied to quantify the amount of taurine in human serum sample with good recovery values from 97.3 to 113%.

An electrochemical sensor based on electrospun MoS2 @SnO2 modified carbon nanofiber composite materials for simultaneously detection of phenacetin and indomethacin.

SnO2 -CNF was prepared by coaxial blending technology, and MoS2 was grown uniformly on SnO2 -CNF composite by adding a hydrothermal post-treatment step. The uniform distribution of MoS2 on one-dimensional SnO2 -CNF can effectively establish a layered three-dimensional structure. Accordingly, the prepared MoS2 -coated SnO2 -CNF composite material has higher surface area and more active sites to obtain better electrochemical performance. We constructed an electrochemical sensor within the composite material with enhanced performance to realize the simultaneous and highly sensitive detection of phenacetin and indomethacin. The sensor has linear ranges of 0.050-7200 µM and 0.05-500 µM, respectively, and the detection limits were 0.016 µM and 0.013 µM. Furthermore, the sensor has good anti-interference ability and stability, which also achieves good recovery rate in the actual sample detection.

A novel molecularly imprinted electrochemical sensor based on a nitrogen-doped graphene oxide quantum dot and molybdenum carbide nanocomposite for indometacin determination.

In this work, nitrogen-doped graphene oxide quantum dots (N-GOQDs) were embedded into Mo2C to prepare a nanocomposite with great electrical conductivity and a large specific surface area. We manufactured an innovative electrochemical sensor based on N-GOQDs-Mo2C and a molecularly imprinted polymer (MIP) for the highly sensitive detection of indometacin (IDMC). The MIP was synthesized by electropolymerization using acrylamide as the functional monomer and IDMC as the template molecule. N-GOQDs-Mo2C was organized by an elementary hydrothermal approach and characterized by SEM, TEM, XRD and FT-IR. In the first-rank experimental conditions, the MIP electrochemical sensor shows a wide linear range from 10-15 M to 10-5 M for IDMC detection and the detection limit is as low as 9.508 × 10-16 M. Additionally, the manufactured sensor shows great selectivity for indometacin, excellent repeatability and stableness. The sensor can be applied to the detection of indometacin in tablets and water samples with fulfilling consequence.

Fabrication of poly-sulfosalicylic acid film decorated pure carbon fiber as electrochemical sensing platform for detection of theophylline.

In this work, we integrated the superiority of good conductivity, large surface area of carbon fibers and the catalytic property, good biocompatibility of polymer sulfosalicylic acid to construct a novel electrochemical sensor to detect theophylline in drug analysis. The morphology of nanocomposite was characterized by scanning electron microscopy (SEM). The polymerization between monomers was observed by Fourier transform infrared spectroscopy (FTIR). The composite between carbon material and polymer was verified by Raman spectrum. Under the optimal experimental conditions, the concentration of theophylline (0.6∼137 µM) and the peak current value revealed a good linear relationship and the limit of detection as low as 0.2 µM. In addition, the proposed sensor exhibits repeatability, stability and ease of selectivity.

Spatio-temporal analysis of irrigation water use coefficients in China.

Water shortage is a major problem for agriculture in many countries. Agricultural water accounts for more than 60% of total water consumption in China. Improving agricultural strategies in using irrigation water more effectively and efficiently is important to alleviate water shortages and associated environmental problems. In this study, the spatiotemporal distribution differences of irrigation water use coefficient in large, medium and small-scale irrigation districts and pure well irrigation districts in the 31 provinces of China (excluding Hong Kong, Macao and Taiwan) were analyzed by means such as the Zipf's law and spatial autocorrelation. The results showed that the national irrigation water use coefficient had increased from 0.501 in 2010 to 0.542 in 2016. By size of irrigation area, the irrigation water use coefficient in small irrigation areas was higher than that of large- and medium-scale irrigation districts. Regionally, the irrigation water use coefficient in the eastern region was significantly higher than that in the western region, and the coefficient in northern region was higher than that in the southern region. The spatial spillover effect of the national irrigation water use coefficient gradually weakened, and the spatial spillover effect of large and medium-scale irrigation districts was not obvious. The spatial spillover effect of pure well irrigation districts varied greatly over time. All these results give a spatiotemporal overview of agricultural water use in China, which provides a direction for improving irrigation water coefficient in China.

A novel molecularly imprinted electrochemical sensor based on double sensitization by MOF/CNTs and Prussian blue for detection of 17ß-estradiol.

In this paper, we constructed MIL-53 (AlOHbdc, bdc = benzene-1,4-dicarboxylate) /CNTs and Prussian blue (PB) as the double sensitization material of the sensing platform, in which the MIL-53/CNTs hybrid can not only increase the specific surface area but also increase the conductivity of the sensor and PB can play a role in amplifying electrical signals and accelerating electron transmission. Pyrrole was used as monomer and E2 was used as template for electropolymerization to form conductive film. Moreover, the overoxidation/dedoping elution method were used to simplify the experimental process. Under optimal conditions, the MIECS exhibited an excellent sensitivity and high selectivity with a wide linear response range between 10-14 to 10-9 mol L-1 and an estimated detection limit of 6.19 × 10-15 mol L-1.

A novel electrochemical enzyme biosensor for detection of 17ß-estradiol by mediated electron-transfer system.

An extremely sensitive enzyme sensor for detection of 17ß-estradiol based on electropolymerized L-lysine molecules on a glassy carbon electrode (GCE) modified with critic acid@graphene (CA-GR) and cross-linked with laccase enzyme has been developed in this work. As the laccase immobilization, glutaraldehyde was chosen as cross-linker through the groups reactions. The novel enzyme sensor could recognize and determinate 17ß-estradiol effectively. The morphology of the enzyme modified electrode was characterized by transmission electron microscopy (TEM) and electron microscopy (SEM). The amino interaction between cross-linker and enzyme was characterized by Fourier transform infrared spectroscopy (FTIR). Under the optimal experimental conditions, good linear relationships were achieved in the range of 4 × 10-13 - 5.7 × 10-11 M and a limit of detection as low as 1.3 × 10-13 M. Moreover, the enzyme sensor exhibited good reproducibility, stability and high selectivity to 17ß-estradiol. Excellent performance was showed in the human urine samples analysis, thus confirming great prospect for further application in clinic diagnosis and biological research.