Magnesium-containing mesoporous silica sieve (Mg-MCM-41) provided a suitable immobilization of biomolecule matrix due to its uniform pore structure, high surface areas, fast electron-transfer rate, and good biocompatibility. Based on this, an amperometric biosensor was developed by entrapping laccase into the Mg-MCM-41/PVA composite matrix. Laccase from Trametes versicolor was assembled on a composite film of Mg-MCM-41/PVA modified Au electrode and the electrode was investigated by cyclic voltammetry, impedance spectroscopy, and chronoamperometry. The results indicated that the Mg-MCM-41/PVA/Lac modified electrode exhibited excellent catalytic activity towards catechol at room temperature in pH 4.8 acetate buffer solution. The optimum experimental conditions of biosensor for the detection of catechol were studied in detail. Under the optimal conditions, the linear range was from 0.94 to 10.23 μM with the sensitivity of 16.9227 A/M, the detection limit of 0.00531 μM, and the response time of less than 14 s. The Michaelis-Menten constant (KMapp) was estimated by Lineweaver-Burk equation and theKMappvalue was about 1.01 μM. In addition, the biosensor exhibited high reproducibility and long-time stability. This work demonstrated that Mg-MCM-41/PVA composite provides a suitable support for laccase immobilization and construction of biosensor.
A novel processing that leads to the formation of a protective compound coating upon the AZ91D Mg alloy by the combination of cold spraying of Al-Mg alloy on a die cavity surface with subsequent die casting was discussed. The microstructure and phase composition of the coating were investigated using X-ray diffraction and scanning electron microscope coupled with energy dispersive spectroscopy. Results revealed that the coating consisted mainly of b phase (Mg 17 Al 12 ) plus some Al and integrated with the substrate by mechanical interlocking and slender metallurgical bonding formed during the die casting process. A high bond strength of 82¡5 MPa for the coating was achieved. The hardness and wear resistance of the AZ91D Mg alloy were greatly improved due to the compound coating. Simultaneously, the results of immersion tests and electrochemical corrosion tests indicated that the coated AZ91D Mg alloy specimens had better corrosion resistance compared with the bare AZ91D alloy specimen.
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