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Thrombin plays an essential role in blood coagulation and some physiological and pathological processes. The convenient, rapid, sensitive, and specific detection of thrombin is of great significance in clinical research and diagnosis. Herein, surface molecularly imprinted polymer (MIP) was modified on aptamer-functionalized Fe3O4 nanoparticles (MIP–aptamer–Fe3O4 NP) for thrombin colorimetric assay by taking advantage of the peroxidase-like activity of Fe3O4 NP. With the adsorption of thrombin into imprinted cavities, the exposed surface area of Fe3O4 NP decreased, causing a decrease in its peroxidase-like activity toward 3,3′,5,5′-tetramethylbenzidine (TMB) in the presence of H2O2. On the other hand, the reductive amino acids on the thrombin surface also impeded the oxidation of TMB. Both phenomena caused the light blue color of the sensing solution. Thus, a specifically sensitive colorimetric approach for the visual detection of thrombin was proposed with a linear range and limit of detection of 108.1 pmol L−1–2.7 × 10−5 mol L−1 and 27.8 pmol L−1, respectively. Moreover, due to the double recognition elements of MIP and aptamer, the prepared MIP–aptamer–Fe3O4 NP showed higher selectivity to thrombin than that based on only one recognition element. It is worth noting that no special property (e.g. electrochemical or fluorescence activity) of the template was required in this work. Thus, more template molecules can be easily, selectively, and sensitively detected based on the proposed MIP–aptamer–mimic enzyme colorimetric sensing strategy. [ABSTRACT FROM AUTHOR]

Molybdenum carbide is a cost‐effective alternative to Pt‐group noble metal electrocatalyst for hydrogen evolution reaction (HER), developing a facile strategy to improve the HER activity of molybdenum carbide and understanding the mechanism is of great concern and challenging. Herein, a solvothermal‐assisted self‐assembly procedure of fabricating sandwiched NiO/β‐Mo2C/RGO nanocomposite catalyst was reported. Electrochemical measurements demonstrate that the catalytic activity and durability of β‐Mo2C can be significantly improved in the sandwiched NiO/β‐Mo2C/RGO. Comparative studies between various catalysts such as β‐Mo2C, NiO/β‐Mo2C, β‐Mo2C/RGO, and NiO/β‐Mo2C/RGO have been performed to explore the mechanism underpinning their different catalytic performance. Our results revealed that hybrid of β‐Mo2C and RGO resulted in significant improvement in electrical conductivity, NiO loading modified the electron density on the surface of β‐Mo2C (101) to the electron‐rich state to generate highly active catalytic site. The synergistic effect of RGO and NiO loading would be responsible for the improved electrocatalytic performance of the NiO/β‐Mo2C/RGO catalysts. The strategy developed in this work not only provides a new pathway for improving HER activity of molybdenum carbide but also deepens fundamental understandings on the structure‐reactivity of molybdenum carbide‐based nanocomposite catalysts with higher HER activity. [ABSTRACT FROM AUTHOR]

In this study, an exfoliated graphite paper (EGP) was employed as a supported electrode for prussian blue (PB) and gold nanoparticles (AuNPs) modification to fabricate a novel electrochemical sensor. The scanning electron microscopy image showed the multilayer structure of the sensor with PB and AuNPs uniform coating. Due to the high surface area and good conductivity of the multilayer structure, as well as the conductivity of AuNPs, the prepared sensor exhibited an obvious improvement for sensitive detection of nicotinamide adenine dinucleotide (NADH) with a linear range of 5.0 × 10−7 mol L−1–1.0 × 10−3 mol L−1. Moreover, the modified PB film endowed the sensor with good electrocatalytic activity for hydrogen peroxide (H2O2) sensing. Under the optimal conditions, the linear range and limit of detection for H2O2 sensitive detection were 5.0 × 10−8 mol L−1–1.0 × 10−3 mol L−1 and 4.8 × 10−9 mol L−1, respectively. The sensor can also be used for detection in real samples with satisfactory results. The advantages of low-cost, easy modification, multilayer structure, and good conductivity made the EGP an alternative candidate for supported electrode materials in the preparation and application of various electrochemical sensors. [ABSTRACT FROM AUTHOR]

We have combined the molecular imprinting and the layer-by-layer assembly techniques to obtain molecularly imprint polymers (MIPs) for the electrochemical determination of p-nitrophenol ( p-NPh). Silica microspheres functionalized with thiol groups and gold nanoparticles (Au-NPs) were assembled on a gold electrode surface layer by layer. The electrode was then immersed into a solution of pyrrole and p-NPh (the template), and electropolymerization led to the creation of a polymer-modified surface. After the removal of the silica spheres and the template, electrochemical impedance spectroscopy and differential pulse voltammetry (DPV) were employed to characterize the surface. The results demonstrated the successful fabrication of macroporous MIPs embedded with Au-NPs on the gold electrode. The effects of monomer concentration and scan rate on the performance of the electrode were optimized. Excellent recognition capacity is found for p-NPh over chemically similar species. The DPV peak current is linearly related to concentration of p-NPh in the 0.1 μM to 1.4 mM range, with a 0.1 μM limit of detection (at S/N = 3). [Figure not available: see fulltext.] [ABSTRACT FROM AUTHOR]

Abstract: A one-step precipitation polymerization synthesis was adopted for the preparation of molecularly imprinted polymers (MIPs) by using hydroquinone as a template molecule. The transmission electron microscopy (TEM) exhibited that the polymers were uniform spheres with the diameter of about 700nm. The results of adsorption experiments showed that the microspherical imprinted polymers possessed fast adsorption dynamics. Compared to the structurally similar compounds, catechol and resorcinol, the MIPs exhibited a high recognizable capacity to hydroquinone. And the electrochemical sensor fabricated by modifying the prepared MIPs microsphere on the glassy carbon electrode surface was used to detect the hydroquinone concentration. The current response was proportional to the concentration of hydroquinone in the range of 2.0×10−6 to 1.0×10−4 mol/L with the detection limit of 1.0×10−6 mol/L. [Copyright &y& Elsevier]

In this study, an exfoliated graphite paper (EGP) was employed as a supported electrode for prussian blue (PB) and gold nanoparticles (AuNPs) modification to fabricate a novel electrochemical sensor. The scanning electron microscopy image showed the multilayer structure of the sensor with PB and AuNPs uniform coating. Due to the high surface area and good conductivity of the multilayer structure, as well as the conductivity of AuNPs, the prepared sensor exhibited an obvious improvement for sensitive detection of nicotinamide adenine dinucleotide (NADH) with a linear range of 5.0 × 10-7 mol L-1-1.0 × 10-3 mol L-1. Moreover, the modified PB film endowed the sensor with good electrocatalytic activity for hydrogen peroxide (H2O2) sensing. Under the optimal conditions, the linear range and limit of detection for H2O2 sensitive detection were 5.0 × 10-8 mol L-1-1.0 × 10-3 mol L-1 and 4.8 × 10-9 mol L-1, respectively. The sensor can also be used for detection in real samples with satisfactory results. The advantages of low-cost, easy modification, multilayer structure, and good conductivity made the EGP an alternative candidate for supported electrode materials in the preparation and application of various electrochemical sensors.

Core-shell structural magnetic molecularly imprinted polymers (magnetic MIPs) with combined properties of molecular recognition and controlled release were prepared and characterized. Magnetic MIPs were synthesized by the co-polymerization of methacrylic acid (MAA) and trimethylolpropane trimethacrylate (TRIM) around aspirin (ASP) at the surface of double-bond-functionalized Fe(3)O(4) nanoparticles in chloroform. The obtained spherical magnetic MIPs with diameters of about 500 nm had obvious superparamagnetism and could be separated quickly by an external magnetic field. Binding experiments were carried out to evaluate the properties of magnetic MIPs and magnetic non-molecularly imprinted polymers (magnetic NIPs). The results demonstrated that the magnetic MIPs had high adsorption capacity and selectivity to ASP. Moreover, release profiles and release rate of ASP from the ASP-loaded magnetic MIPs indicated that the magnetic MIPs also had potential applications in drug controlled release.