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The tradeoff between sensitivity and detection range (maximum and minimum stretchability) is a key limitation in strain sensors; to resolve this, we develop an efficient and novel strategy herein to fabricate a highly sensitive and stretchable strain sensor inspired by the membrane–shell structure of poultry eggs. The developed sensor comprises a soft and stretchable surface-grafting polypyrrole (s-PPy) film (acting as the membrane) and a brittle Au film (acting as the shell), wherein both films complement each other at the electrical and mechanical levels. Au forms cracks under strain contributing to its high sensitivity and low detection limit, and s-PPy can bridge Au cracks and increase stretchability which has not been used in strain sensors before. The surface-grafting strategy not only enhances interface adhesion but also tunes the brittle property of native PPy to render it stretchable. Utilizing the synergetic effect of the membrane–shell complementary structure, the strain sensors achieve ultrahigh sensitivity (>107), large stretchability (100%), and an ultralow detection limit (0.1%), demonstrating significant progress in the field of strain sensors. The membrane–shell (Au/s-PPy)-structured strain sensor can successfully detect finger motion, wrist rotation, airflow fluctuation, and voice vibration; these movements produce strain in the range of subtle to marked deformations. Results evidence the ultrahigh performance and bright application prospects of the developed strain sensors.

Internal asymmetric tandem supercapacitors with wide working voltage have drawn an increasing attention to develop high-energy-density supercapacitors. However, the small specific capacitance and low working voltage of single-supercapacitor restrict further improvement of their energy density. A rational solution to this restriction would be to synthesize high-performance electrode materials. Accordingly, this work specifies a simple and cost-effective method to directly grow manganese dioxide and vanadium nitrogen nanosheets on zeolitic imidazolate framework-67 derived N-doped carbon conductive skeletons. These well-designed core-shell pseudocapacitive materials integrate the features of large specific surface area, rich reaction sites, high mass loading, short electron/ion diffusion paths and remarkable conductivity, affording prominent electrochemical performance. Furthermore, a flexible all-solid-state internal asymmetric tandem 6.6 V all-in-one supercapacitor was successfully assembled by matching as-fabricated cathode and anode materials as well as using carbon nanotube film as a lightweight current collector. The resulting all-in-one devices exhibited a high specific capacitance of 336.7 mF/cm2 (19.6 F/cm3) and an exceptional energy density of 2032.8 μWh/cm2 (118.2 mWh/cm3) and thus substantially outperform most previously reported state-of-the-art asymmetric supercapacitors. Our work provides a promising strategy for the rational construction of high-performance, inexpensive and safe all-in-one supercapacitors for next-generation portable and wearable electronic devices. This work was supported by the National Natural Science Foundation of China (No. 51703241), the Fundamental Research Funds for the Central Universities (No. 020514380183), the Key Research Program of Frontier Science of Chinese Academy of Sciences (No. QYZDB-SSWSLH031), the Thousand Youth Talents Plan, and the Science and Technology Project of Nanchang (2017-SJSYS-008).

Organic semiconductors (OSC) are generally considered intrinsic (undoped), an assumption which underpins our understanding of the charge transport in this promising class of materials. However, this premise conflicts with a variety of experimental observations, that suggest the presence of excess holes carriers in OSCs at room temperature. Here, using a low-power plasma de-doping method, we report that trace amounts (~1015 cm-3) of oxygen-induced organic radical cations (OIORCs) are inherent in the lattice of OSCs as innate hole carriers, and that this is the origin of the p-type characteristics exhibited by the majority of these materials. This finding clarifies previously unexplained organic electronics phenomena and provides a foundation upon which to re-understand charge transport in OSCs. Furthermore, the de-doping method can eliminate the trace OIORCs, resulting in the complete disappearance of p-type behavior, while re-doping (under light irradiation in O2), reverses the process. These methods can precisely modulate key electronic characteristics (e.g., conductivity, polarity, and threshold voltage) in a nondestructive way, expanding the explorable charge transport property space for all known OSC materials. Accordingly, we conclude that our tailorable OIORC doping strategy, requiring only off-the-shelf equipment and a glovebox, will become a core technology in the burgeoning organic electronics industry.

Conductive polymers are considered promising electrode materials for organic transistors, but the reported devices with conductive polymer electrodes generally suffer from considerable contact resistance. Currently, it is still highly challenging to pattern conductive polymer electrodes on organic semiconductor surfaces with good structure and interface quality. Herein, we develop an in situ polymerization strategy to directly pattern the top-contacted polypyrrole (PPy) electrodes on hydrophobic surfaces of organic semiconductors by microchannel templates, which is also applicable on diverse hydrophobic and hydrophilic surfaces. Remarkably, a width-normalized contact resistance as low as 1.01 kΩ·cm is achieved in the PPy-contacted transistors. Both p-type and n-type organic field-effect transistors (OFETs) exhibit ideal electrical characteristics, including almost hysteresis-free, low threshold voltage, and good stability under long-term test. The facile patterning method and high device performance indicate that the in situ polymerization strategy in confined microchannels has application prospects in all-organic, transparent, and flexible electronics.

A catalyst of ruthenium supported on CoFe layered double oxide (CoFe-LDO) allows selective hydrogenation of biomass-based 5-hydroxymethylfurfural (HMF) to the high-quality liquid fuel 2, 5-dimethylfuran (DMF) in the presence of tetrahydrofuran (THF). Under the optimal conditions, Ru/CoFe-LDO was exhibited higher catalytic performance, yielding 98.2% DMF with 100% HMF conversion at a relatively mild reaction temperature of 180 °C for 6 h. The structure and composition of the support and catalyst were investigated through a series of characterized methods Influence of various reaction parameters, such as reaction temperature, solvent Ru content of the catalyst and calcinations temperature of carrier etc., were explored with respect to HMF conversion and DMF yield. Although Ru/CoFe-LDO had a little loss in the catalytic activity after three successive reaction runs, the activity could be easily recovered by heating and reducing with hydrazine hydrate. Moreover our results also showed the cooperation between the metallic Ru site and the CoFe-LDO further facilitates the process of HMF hydrogenation to DMF.