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Pyrolytic kinetics of indene was studied in a flow reactor at 30 and 760 Torr. Indene and its decomposition products, as well as polycyclic aromatic hydrocarbons (PAHs), were measured with synchrotron vacuum ultraviolet photoionization mass spectrometry (SVUV-PIMS). Five literature models were selected to reproduce the experimental data and analyze the reaction kinetics of indene. The experimental and predicted results illustrate that an indenyl radical is the dominant decomposition intermediate and also the main contributor to the further growth of aromatic rings in the pyrolysis of indene. The indene consumption process needs further precise characterization, especially the subsequent dissociation reactions of indanyl and indenyl radicals. A self-recombination reaction of the indenyl radical and the combination reactions between indenyl and other radicals are found to be necessary for the efficient formation of large PAHs. The absence of these pathways leads to the underprediction of experimental measurements. In contrast, literature models adopting indenyl global reactions for PAH formation generally overestimate the system reactivity. Proper radical combination pathways proposed in a future model should consider not only the PAH formation efficiency but also its impact on system reactivity. [ABSTRACT FROM AUTHOR]

A new self-powered electronic-skin (e-skin) for real-time perspiration analysis has been fabricated from a polyaniline (PANI) triboelectric-biosensing unit matrix, which can also work as a self-powered visualization system for preventing exercise injury (dehydration). The biosensing units on the e-skin can be driven by body motion through efficiently converting mechanical energy into triboelectric current. After surface modification with enzymes and a drop-cast chitosan film, the triboelectric output of the biosensing units can be influenced by the target biomarkers, acting as a biosensing signal. This new triboelectrification/enzymatic-reaction coupling effect has been demonstrated in different biosensing units that can detect the urea, uric acid, lactate, glucose, Na+ and K+ concentration in perspiration without any external electricity power. The e-skin can be linked to a visualization panel, and the input triboelectric current can show the motion state of the human body during exercise. This work can provoke a new research direction for developing wearable healthcare diagnosis systems and self-powered visualization systems. This new technique could also reduce medical expenses and facilitate application in low-income regions. [ABSTRACT FROM AUTHOR]

The emerging electronic-skins (e-skins) are designed to mimic the comprehensive properties of human perception via flexible device techniques, and the achievement of a vision e-skin for image recognition is a highly interesting topic for applications in bionic organs and robots. In this paper, a new self-powered flexible vision e-skin has been realized from a pixel-addressable matrix of piezophototronic ZnO nanowire arrays. Under applied deformation, the e-skin can actively output piezoelectric voltage (piezoelectric effect), and the output piezoelectric voltage can be significantly influenced by UV illumination. The piezoelectric output can be regarded as both a photodetecting signal and electrical power for driving the device (no external power source is needed). The working mechanism is based on the optoelectronic/piezoelectric coupling effect (piezophototronic effect) of ZnO. The photo-generated carriers inside the ZnO nanowires can partially screen the piezoelectric field, affecting the piezoelectric output. The e-skin device has a 6 × 6 pixel-addressable matrix structure, and can map multi-point UV-stimuli through a multichannel data acquisition method, realizing image recognition. This new device structure and working mechanism may provoke a new research direction for the development of multi-functional e-skins. [ABSTRACT FROM AUTHOR]

A new self-powered, stretchable, fiber-based electronic-skin (e-skin) has been fabricated for actively detecting human motion and environmental atmosphere. Several bundles of carbon fibers (coated with polydimethylsiloxane (PDMS) or polypyrrole (Ppy)) were woven together, forming a flexible fiber-based e-skin. The triboelectric current of the e-skin was dependent on the strain deformation and the environmental atmosphere. The e-skin can actively detect various human motions, such as finger touch, joint motion, skin deformation and slight stretching. Each PDMS–Ppy crossing point can be employed as an independent unit, and these units can output triboelectric current individually, realizing the tactile perception. The e-skin can also monitor volatile organic compounds in the atmosphere with high sensitivity, recovery and selectivity, (e.g. upon exposure to 1200 ppm methanol vapor, the triboelectric current of the e-skin decreased from 41.17 (in air) to 15.12 nA). The working mechanism is based on the triboelectrification/gas-sensing coupling effect. This new device architecture and material system can promote the development of a self-powered multifunctional e-skin. [ABSTRACT FROM AUTHOR]

To replace Pt-based catalysts for the oxygen reduction reaction (ORR) in energy conversion and storage systems, it is highly desirable to explore low-cost and high-performance nonprecious metal catalysts. Herein, we report a novel Mn-based catalytic system for the ORR which consists of MnO nanoparticles encapsulated in mesoporous few-layer carbon (MnO@FLC). Using density functional theory (DFT), we disclose that the few-layer carbon could be activated by the encapsulated MnO nanoparticles and further become active sites for the ORR process. The MnO@FLC electrocatalyst exhibits outstanding ORR activity (an onset potential of −0.005 V vs. Ag/AgCl, a half-wave potential of −0.153 V and a limiting current density of −5.38 mA cm−2), which are among the best performances reported to date for Mn-based ORR electrocatalysts and highly comparable to those of state-of-the-art Pt/C catalysts in alkaline media. Our work suggests that metal oxides encapsulated in few-layer carbon could serve as efficient ORR electrocatalysts with decent performance. [ABSTRACT FROM AUTHOR]

Core–shell Co3O4/ZnCo2O4 coconut-like hollow spheres are synthesized by a facile two-step method. As the anode of lithium-ion batteries, their reversible capacity is up to 1278 mA h g−1 at 0.1C rate and remains at 1093 mA h g−1 after 50 cycles, much higher than that of pure Co3O4. Even after 300 cycles (cycling for more than 4 months), their reversible capacity can maintain at 934 mA h g−1 at 0.2C rate. Such superior electrochemical performance (high reversible capacity, excellent long-term cycling stability and good rate capability) can be ascribed to the unique core–shell hollow structure, complex synergistic effect, good electrical conductivity and interfacial charging mechanism. The present results demonstrate that the core–shell Co3O4/ZnCo2O4 hollow spheres are promising anode materials for high-performance lithium-ion batteries. [ABSTRACT FROM AUTHOR]

Highly sensitive humidity sensing has been realized from a Cd-doped ZnO nanowire (NW) nanogenerator (NG) as a self-powered/active gas sensor. The piezoelectric output of the device acts not only as a power source, but also as a response signal to the relative humidity (RH) in the environment. The response of Cd–ZnO (1 : 10) NWs reached up to 85.7 upon exposure to 70% relative humidity, much higher than that of undoped ZnO NWs. Cd dopant can increase the number of oxygen vacancies in the NWs, resulting in more adsorption sites on the surface of the NWs. Upon exposure to a humid environment, a large amount of water molecules can displace the adsorbed oxygen ions on the surface of Cd–ZnO NWs. This procedure can influence the carrier density in Cd–ZnO NWs and vary the screening effect on the piezoelectric output. Our study can stimulate a research trend on exploring composite materials for piezo-gas sensing. [ABSTRACT FROM AUTHOR]

α-MoO3–In2O3 core–shell nanorods were prepared by a facile two-step hydrothermal method. As the anode of lithium-ion batteries, their reversible capacity was up to 1304 mA h g−1 at 0.2 C rate (5 hours per half cycle) and maintains 1114 mA h g−1 after 50 cycles. At a rate of 0.3 C, 0.5 C, 1 C and 2 C, the discharge capacities after 50 cycles were maintained at 938, 791, 599 and 443 mA h g−1, respectively. The enhanced electrochemical performance can be ascribed to the synergistic effect between α-MoO3 and In2O3, one-dimensional core–shell nanostructures, short paths for lithium diffusion and interface spaces. [ABSTRACT FROM AUTHOR]

Room-temperature self-powered ethanol sensing has been realized from ZnO nanowire (NW) arrays by combining their piezoelectric, photoelectric and gas sensing characteristics. Under the assistance of UV illumination, the piezoelectric output of ZnO NWs acts not only as a power source, but also as a response signal to ethanol gas at room temperature. Upon exposure to 700 ppm ethanol at room temperature under 67.5 mW cm−2 UV illumination, the piezoelectric output voltage of ZnO NWs (under 34 N compressive forces) decreases from 0.80 V (in air) to 0.12 V and the response is up to 85. The room-temperature reaction between the UV-induced chemisorbed oxygen ions and ethanol molecules increases the carrier density in ZnO NWs, resulting in a strong piezoelectric screening effect and very low piezoelectric output. Our study can stimulate a research trend on designing new gas sensors and investigating new gas sensing mechanisms. [ABSTRACT FROM AUTHOR]

First-principles theory was used to design a potassium-doped lithium niobate single crystal. The structural, electronic, optical and ferroelectric properties of the potassium-doped LiNbO3 single crystal model have been investigated using a generalized gradient approximation within density functional theory. It was found that substitution with potassium drastically changed the optical and electronic nature of the crystal and that the band gap slightly decreases. A series of LiNbO3 single crystals doped with x mol% K (x = 0, 3, 6, 9, 12 mol%) were successfully grown using the Czochralski method. The crystals were characterized using powder X-ray diffraction, UV-vis-infrared absorption spectroscopy and a ferroelectric property test. The experimental test results were consistent with the calculated predictions. [ABSTRACT FROM AUTHOR]

Room-temperature self-powered H2S sensing with high response and selectivity has been realized from a Cu-ZnO nanowire nanogenerator. Upon exposure to 1000 ppm H2S at room temperature, the piezoelectric output voltage of the device (5 at% Cu-ZnO) under compressive force decreases from 0.552 (in dry air) to 0.049 V, and the response is up to 1045, over 8 times larger than that of undoped ZnO nanowires. The selectivity against H2S is also very high at room temperature. The enhanced room-temperature H2S sensing performance can be attributed to the coupling of the piezoelectric screening effect of ZnO nanowires and the synergistic effect of the Cu dopant. This study should stimulate research into designing a new gas sensor for detecting toxic gases at room temperature.