Microwave dielectric properties and thermally stimulated depolarization currents (TSDC) of (1−x)Ba0.6Sr0.4La4Ti4O15–xTiO2 (x = 0, 0.01, 0.02, 0.05, and 0.1) ceramics were studied. X‐ray diffraction analysis indicates that the specimens show a hexagonal perovskite structure; however, with an increase of x to 0.1, TiO2−δ as a secondary phase can be detected in the ceramics. The variation of TiO2 content has a significant effect on the dielectric properties of (1−x)Ba0.6Sr0.4La4Ti4O15–xTiO2 at microwave frequency. The dielectric permittivity of ceramics increases from 44 to 49 with the increase of TiO2 content. The Qf value is in the range of 39 300–53 400 GHz. However, the temperature coefficient of resonant frequency (τf) changes from −7.5 to–9.4 ppm/°C, and then turns to +3.9 ppm/°C. A near zero τf value can be obtained by tuning the content of TiO2 addition. TSDC was also employed to analysis the extrinsic loss mechanism. Utilizing a fixed polarization condition, the TSDC relaxation peaks are present, which are generated by oxygen vacancies. And the concentration of oxygen vacancies increases with the increase of TiO2 content. It can be concluded that the extrinsic dielectric loss is dominated by microstructure and oxygen vacancy defects.
The periosteum plays an important role in bone formation and reconstruction. One of the reasons for the high failure rate of bone transplantation is the absence of the periosteum. Silk fibroin (SF) and silk sericin (SS) have excellent biocompatibility and physicochemical properties, which have amazing application prospects in bone tissue engineering, but lacked mechanical properties. We developed a series of SF/SS composite films with improved mechanical properties using boiling water degumming, which caused little damage to SF molecular chains to retain larger molecules. The Fourier transform infrared spectroscopy and X-ray diffraction results showed that there were more β-sheets in SF/SS films than in Na2CO3 degummed SF film, resulting in significantly improved breaking strength and toughness of the composite films, which were increased by approximately 1.3 and 1.7 times, respectively. The mineralization results showed that the hydroxyapatite (HAp) deposition rate on SF/SS composite films was faster than that on SF film. The SF/SS composite films effectively regulated the nucleation, growth and aggregation of HAp-like minerals, and the presence of SS accelerated the early mineralization of SF-based materials. These composite films may be promising biomaterials in the repair and regeneration of periosteum.
In this work, bismerthiazol was firstly assayed by a fast and portable method employing protein-capping gold nanoculsters as probes. The luminescent intensity of the nanoclusters showed a correlative response towards bismerthiazol from 5 to 4000 μg/mL with a linear relation in the range of 5 - 100 μg/mL. As little as 5 μg/mL of bismerthiazol could be quantified. The high affinity of bismerthiazol to interact with the soybean protein-capped gold nanoclusters contributed to the excellent selectivity of this method over other common pesticides. The recoveries in several cabbage samples were 101 - 135%, indicating good performance in practical applications. By comparison to previous reported approaches, this method bears advantages including simple operation, fast response, visual readout and good selectivity.
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