The enzymatic biofuel cell (EBFC) has been considered as a promising implantable energy generator because it can extract energy from a living body without any harm to the host. However, an unprotected enzyme will be destabilized and even eventually be deactivated in human blood. Thus, the performance of implantable EBFC has received barely any improvement. It is therefore a breakthrough in realizing a superior efficient EBFC that can work stably in human blood which relies in protecting the enzyme to defend it from the attack of biological molecules in human blood. Herein, we innovatively created a single-walled carbon nanotube (SWCNT) and cascaded enzyme-glucose oxidase (GOx)/horseradish peroxidase (HRP) coembedded hydrophilic MAF-7 biocatalyst (SWCNT-MAF-7-GOx/HRP). The SWCNT-MAF-7-GOx/HRP is highly stable in electrocatalytic activity even when it is exposed to high temperature and some molecular inhibitors. In addition, we were pleasantly surprised to find that the electrocatalytic activity of GOx/HRP in hydrophilic SWCNT-MAF-7 far surpasses that of the GOx/HRP in hydrophobic SWCNT-ZIF-8. In human whole blood, the SWCNT-MAF-7-GOx/HRP catalytic EBFC exhibits an eightfold increase in power density (119 μW cm −2 vs 14 μW cm −2 ) and 13-fold increase in stability in comparison with the EBFC based on an unprotected enzyme. In this study, the application of metal−organic framework-based encapsulation techniques in the field of biofuel cells is successfully realized, breaking a new path for creating implantable bioelectrical-generating devices.
An electric resistance measurement was used to study the crystallization process of Ge 2 Sb 2 Te 5 ͑GST͒ and N-doped Ge 2 Sb 2 Te 5 ͑N-GST͒ films. The relation between conductivity and annealing time was investigated and the crystallization parameters were determined directly by resistance measurement during isothermal crystallization process in the amorphous GST and the N-GST films. The results show that the crystallization processes in both GST and N-GST films are layer by layer. Their conductivities satisfy the equation = c − ͑ c − a ͒exp͑−kt n ͒, at t Ͼ , where is a temperature-dependent time in the process of crystallization. The activation energy for crystallization of amorphous GST films was 2.11± 0.18 eV and the Avrami coefficient was between 2 to 4, in close agreement with previous studies using different techniques. After N doping the Avrami coefficient decreased, while the activation energy increased. The formation of a strain induced by the distortion of unit cell after N doping was used to explain the observed results.
High quality SrTiO3 thin film on (1 1 0) DyScO3 substrate is grown by laser molecular beam epitaxy. The lattice strain resulting from the lattice mismatch between the substrate and the film relaxes gradually with depth. A critical thickness of about 30 nm for sharp strain relaxation is observed. The dislocation density, which forms to relax the lattice strain, is estimated to be about 108 cm−2 according to the high resolution x-ray diffraction. The edge dislocation density is slightly larger than that of the screw ones.
A highly compact and self-sustained in vitro “diagnosis-therapy-evaluation” platform is developed by integrating a glucose/O2 fuel cell-based biosensor with a drug delivery system.
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