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We report ultraviolet phototransistors (UVPTs) based on p-GaN/AlGaN/GaN high-electron-mobility transistors (HEMTs). Thanks to the effective depletion of the two-dimensional electron gas by the p-GaN layer, a dark current as low as 5.2 × 10−10A mm−1 was achieved. Moreover, a unique sub-saturated region can be formed in the transfer curve of the UVPTs due to the special photogenerated electric field in the heterostructure, which endows the device with a large photo-to-dark current ratio over 105. In particular, responsivity up to 1.3 × 108 and 6.1 × 103 A W−1 was demonstrated at gate voltage of 5 and 0.68 V, respectively. The minimum rise time and fall time of the device transient response were measured to be around 1.8 ms and 8.8 ms, respectively. This work shows great UV detection potential of the p-GaN/AlGaN/GaN HEMTs, which opens up possibilities of realizing multifunctional enhancement HEMTs for future III–V photonic integrated devices and systems.

Based on Quartz Crystal Microbalance (QCM) sensing platform, modifying functional groups was usually used to improve the performance of sensing materials. In this work, we reported a novel sensing material, carboxyl functionalized carbon nanocoil by acidification treatment. It was found that carboxyl functionalized carbon nanocoil had excellent reversible response to ammonia (NH3), and the response to 50 ppm NH3 was as high as 8.1 Hz. As a contrast, pristine carbon nanocoil had only 2 Hz response to 50 ppm NH3. The enhanced response should be ascribed to the hydrogen bond adsorption between carboxyl gropus and NH3 molecules. These results demonstrated that carboxyl functionalization could improve the NH3 sensing performance of carbon nanocoil, which has potential in monitoring NH3 in the future.

Stem cell-based tissue engineering shows enormous potential for regenerative medicine. Three-dimensional (3D) stem cell culture is the most basic aspect of tissue engineering. However, achievement of a perfect scaffold for highly efficient 3D cell culture is currently still limited. Herein, a new hyaluronic acid hydrogel dual-enzymatically crosslinked by horseradish peroxidase and choline oxidase is developed as a 3D stem cell culture system. This hydrogel possesses superior stability over two months, controllable biodegradability with hyaluronidases, a high swelling ratio exceeding 6000%, and excellent cytocompatibility in vitro and biocompatibility in vivo. More importantly, a long-time and highly cellular activity 3D culture of bone marrow-derived mesenchymal stem cells was achieved in vitro over 20 days. All these encouraging results highlight the great potential of this new hydrogel for 3D culture and tissue engineering.

Shield tunneling is one of the most important technologies for building of underground engineering. Many grouting holes were prefabricated for the requirement of backfill grouting, which is easy to induce local damages and potential disasters, such as leakage and cracking. Accordingly, an integrated workflow for damage detection and stability evaluation was performed based on nondestructive testing (NDT) and numerical simulation. As a case study, this method was applied to an underwater shield tunnel. Firstly, Ground Penetrating Radar (GPR) was used to detect the conditions in grouting holes. Then, the infrared camera was used to determine the damaged positions induced by grouting holes. According to NDT results, the numerical models were developed to analyze the mechanical behaviors of structure. It indicated the geophysical inversion results are consistent with field conditions. The influence area increases with a significant value of water pressure, and stress magnitude would increase to 45KPa if the increment of water pressure reaches to 10KPa. As a promising application, structure stability was evaluated in the light of analytical results.

The lattice parameters, formation enthalpy, and electronic structures of β-Ti doping with trace transition metal element X (X=Cr, In, Mo, Nb, Pd, Rh, Ru, Sc, Tc, and Y) were systematically calculated by first-principles simulations to explore the effect of these metal elements on the stability of β-Ti at 0 K. Based on our calculations, a satisfactory linear function is found between atomic radius of dopant X and corresponding volume difference. The formation enthalpy results show that the addition of trace transition metal X plays a positive role in the thermodynamical stability of β-Ti at 0 K. This intriguing behavior is well explained by the density of state (DOS).