Shiyao Cao

Self-Powered Photoelectrochemical Biosensor Based on CdS/RGO/ZnO Nanowire Array Heterostructure.

A CdS/reduced graphene oxide (RGO)/ZnO nanowire array (NWAs) heterostructure is designed, which exhibits enhanced photoelectrochemical (PEC) activity compared to pure ZnO, RGO/ZnO, and CdS/ZnO. The enhancement can be attributed to the synergistic effect of the high electron mobility of ordered 1D ZnO NWAs, extended visible-light absorption of CdS nanocrystals, and the formed type II band alignment between them. Moreover, the incorporation of RGO further promotes the charge carrier separation and transfer process due to its excellent charge collection and shuttling characteristics. Subsequently, the CdS/RGO/ZnO heterostructure is successfully utilized for the PEC bioanalysis of glutathione at 0 V (vs Ag/AgCl). The self-powered device demonstrates satisfactory sensing performance with rapid response, a wide detection range from 0.05 mm to 1 mm, an acceptable detection limit of 10 μm, as well as certain selectivity, reproducibility, and stability. Therefore, the CdS/RGO/ZnO heterostructure has opened up a promising channel for the development of PEC biosensors.

Self-powered photoelectrochemical biosensing platform based on Au NPs@ZnO nanorods array

AbstractPhotoanodes, which are used in photoelectrochemical (PEC) water splitting, have been shown to be applicable in the construction of a PEC biosensing platform. This was realized by replacing water oxidization with oxidation of an appropriate test molecule. Here, we have demonstrated the feasibility of adopting photoanodes consisting of zinc oxide nanorods arrays decorated with plasmonic gold nanoparticles (Au NPs@ZnO NRs) for the self-powered PEC bioanalysis of glutathione (GSH) in phosphate-buffered saline (PBS) at an applied bias potential of 0 V vs. Ag/AgCl. This heterostructure exhibited enhanced PEC properties because of the introduction of the Au/ZnO interface. Under visible light illumination, hot electrons from surface-plasmon resonance (SPR) at the Au NP surface were injected into the adjacent ZnO and subsequently driven to the photocathode. Under ultraviolet (UV) light illumination, the photogenerated electrons in ZnO tended to transfer to the fluorine-doped tin oxide due to the step-wise energy band structure and the upward energy band bending at the ZnO/ electrolyte interface. These results indicate that plasmonic metal/semiconductor heterostructure photoanodes have great potential for self-powered PEC bioanalysis applications and extended field of other photovoltaic beacons.

Integrated active sensor system for real time vibration monitoring.

We report a self-powered, lightweight and cost-effective active sensor system for vibration monitoring with multiplexed operation based on contact electrification between sensor and detected objects. The as-fabricated sensor matrix is capable of monitoring and mapping the vibration state of large amounts of units. The monitoring contents include: on-off state, vibration frequency and vibration amplitude of each unit. The active sensor system delivers a detection range of 0–60 Hz, high accuracy (relative error below 0.42%), long-term stability (10000 cycles). On the time dimension, the sensor can provide the vibration process memory by recording the outputs of the sensor system in an extend period of time. Besides, the developed sensor system can realize detection under contact mode and non-contact mode. Its high performance is not sensitive to the shape or the conductivity of the detected object. With these features, the active sensor system has great potential in automatic control, remote operation, surveillance and security systems.

A facile method for the preparation of three-dimensional CNT sponge and a nanoscale engineering design for high performance fiber-shaped asymmetric supercapacitors

Fiber supercapacitors (FSCs) have great application potential in future smart textiles and portable and wearable electronics because of their flexibility, tiny volume and wearability. Their main limitation, however, is the low energy density when compared with batteries, which seriously restricts their practical application. How to enhance their energy densities while retaining their high power densities is a critical challenge for fiber-shaped supercapacitor development. Here, we first fabricated three-dimensional CNT sponge (3DCS) by a facile electrochemical activation and freeze-drying method and then synthesized 3DCS/polyaniline nanocomposite fibers by in situ electro-polymerization. Through a rational nanoscale electrode engineering design, the resultant fibers show a specific capacitance as high as 242.9 F cm−1 in 1 M H2SO4. Furthermore, a fiber-shaped asymmetric supercapacitor (FASC) was assembled using 3DCS/P as the positive electrode and 3DCS as the negative electrode. After optimization, the FASC delivers a high energy density of 30.92 μW h cm−2, which is about 2 times higher than that of the highest reported previously, and maintains a maximum power density (1.78 mW cm−2) more than two orders of magnitude higher than those of micro-batteries and an outstanding mechanical stability with 90.2% specific capacitance retained after 1000 bending cycles. In view of the excellent electrochemical characteristics and the simple manufacturing of the highly conductive and flexible 3DCS/P, it offers new opportunities for designing long-life wearable FSCs with high energy density and high power density.

3D graphene foam/ZnO nanorods array mixed-dimensional heterostructure for photoelectrochemical biosensing

We combined a 3D graphene foam network with a ZnO NRs array and further introduced this mixed-dimensional heterostructure into a PEC biosensing system. The 3D graphene served as a conductive matrix and provided an extra-large spatial surface area for more effective synthesis of ZnO NRs, while the ZnO NRs array functioned as a photoactive material to generate charge carriers and provided reaction sites at the surface for glutathione (GSH) oxidation. Therefore, an elevated photoresponse as well as an improved PEC biosensing performance in the linear range from 5 to 300 μM and an estimated detection limit of 1.53 μM through 3σ were obtained due to the vast reactive surface area and efficient electron transfer of the designed photoanode. The proposed strategy verified that such a spatial bioactive platform is promising in biosensing related fields or other photoelectric energy conversion fields.

Low-cost highly sensitive strain sensors for wearable electronics

Wearable strain sensors have attracted a great amount of attention for their plethora of potential applications, triggering ever growing interest in the search for low-cost materials and obtaining highly sensitive sensors. In this work, novel, flexible and highly sensitive strain sensors were fabricated using graphite granular films deposited on flexible substrates (PET, polyethylene terephthalate) by low-cost carbon-evaporation. The strain sensors show a fast response time of ≤140 ms, a high gauge factor (GF) of 1813, and a long durability of over 10 000 bending cycles. These low-cost, highly sensitive strain sensors have huge potential for applications in wearable electronics for health monitoring.