Heterojunctions on Ta2O5@MWCNT for Ultrasensitive Ethanol Sensing at Room Temperature.

Heterojunctions of Ta2O5 and multiwalled carbon nanotubes (MWCNTs) have been successfully synthesized by a facile and cost-effective hydrothermal method, with a super thin and uniform Ta2O5 shell wrapped around the MWCNT. The combination of Ta2O5 and MWCNTs at the interface not only modifies the morphology but also forms the p-n heterojunction, which contributes to the reconstruction of band structure, as well as the low resistance of matrix and highly chemisorbed oxygen content. The Ta2O5@MWCNT p-n heterojunction exhibits ultrasensitive performance to ethanol at room temperature, with a response of 3.15 toward 0.8 ppm ethanol and a detection limit of 0.173 ppm. The sensor has a high reproducibility at various concentrations of ethanol, superior selectivity to other gases, and long-term stability. The strategy of hybriding metal oxide semiconductors with MWCNT promises to provide a feasible and further developable pathway for high-performance room-temperature gas sensors.

Optoelectronic Artificial Synaptic Device Based on Amorphous InAlZnO Films for Learning Simulations.

Neuromorphic computing, which mimics brain function, can address the shortcomings of the "von Neumann" system and is one of the critical components of next-generation computing. The use of light to stimulate artificial synapses has the advantages of low power consumption, low latency, and high stability. We demonstrate amorphous InAlZnO-based light-stimulated artificial synaptic devices with a thin-film transistor structure. The devices exhibit fundamental synaptic properties, including excitatory postsynaptic current, paired-pulse facilitation (PPF), and short-term plasticity to long-term plasticity conversion under light stimulation. The PPF index stimulated by 375 nm light is 155.9% when the time interval is 0.1 s. The energy consumption of each synaptic event is 2.3 pJ, much lower than that of ordinary MOS devices and other optical-controlled synaptic devices. The relaxation time constant reaches 277 s after only 10 light spikes, which shows the great synaptic plasticity of the device. In addition, we simulated the learning-forgetting-relearning-forgetting behavior and learning efficiency of human beings under different moods by changing the gate voltage. This work is expected to promote the development of high-performance optoelectronic synaptic devices for neuromorphic computing.

Integrated System of Solar Cells with Hierarchical NiCo2O4 Battery-Supercapacitor Hybrid Devices for Self-Driving Light-Emitting Diodes.

An integrated system has been provided with a-Si/H solar cells as energy conversion device, NiCo2O4 battery-supercapacitor hybrid (BSH) as energy storage device, and light emitting diodes (LEDs) as energy utilization device. By designing three-dimensional hierarchical NiCo2O4 arrays as faradic electrode, with capacitive electrode of active carbon (AC), BSHs were assembled with energy density of 16.6 Wh kg-1, power density of 7285 W kg-1, long-term stability with 100% retention after 15,000 cycles, and rather low self-discharge. The NiCo2O4//AC BSH was charged to 1.6 V in 1 s by solar cells and acted as reliable sources for powering LEDs. The integrated system is rational for operation, having an overall efficiency of 8.1% with storage efficiency of 74.24%. The integrated system demonstrates a stable solar power conversion, outstanding energy storage behavior, and reliable light emitting. Our study offers a precious strategy to design a self-driven integrated system for highly efficient energy utilization.