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It is known that the stark disparities between soft tissues and rigid electronics generally introduce difficulties toward seamless interfaces between the two realms. [4] Ultraflexible (opto)electronics and sensors, defined with a thickness down to 10 µm or below, have arisen as an important device configuration that presents extreme mechanical compliance and foresees remarkable application potentials toward imperceptible and wearable system. [5][6][7][8] Particularly for health monitoring applications, intimate contact between sensing components and the human skin would effectively reduce skin-contact impedance, minimize motion artifact, enhance measurement accuracy, and simplify subsequent data possessing algorithm. Despite the significant progress in reducing the device thickness and maintaining high electrical performance, documented thin-film devices have certain limitations: lack of sufficient gas permeability and relatively high Young's modulus compared to that of human tissue. Besides, commonly used flexible substrates for electronics, e.g., parylene, polyethylene terephthalate (PET), polyethylene naphthalate, polyimide, On-skin electronics that offer revolutionary capabilities in personalized diagnosis, therapeutics, and human-machine interfaces require seamless integration between the skin and electronics. A common question remains whether an ideal interface can be introduced to directly bridge thin-film electronics with the soft skin, allowing the skin to breathe freely and the skin-integrated electronics to function stably. Here, an ever-thinnest hydrogel is reported that is compliant to the glyphic lines and subtle minutiae on the skin without forming air gaps, produced by a facile cold-lamination method. The hydrogels exhibit high water-vapor permeability, allowing nearly unimpeded transepidermal water loss and free breathing of the skin underneath. Hydrogel-interfaced flexible (opto)electronics without causing skin irritation or accelerated device performance deterioration are demonstrated. The long-term applicability is recorded for over one week. With combined features of extreme mechanical compliance, high permeability, and biocompatibility, the ultrathin hydrogel interface promotes the general applicability of skin-integrated electronics.

ZnFe 2 O 4 is a promising visible-light-driven photocatalyst with high energy level CBM for hydrogen generation. However, it could only be synthesized in the bulk form and its photocatalytic activities are limited by the rapid recombination of photo-generated carriers. Here, we report the preparation of a ZnFe 2 O 4 nanostructure in ultrathin hollow sphere morphology with a 10 nm thick shell, which could shorten the diffusion distance of photo-generated carriers to minimize their interior recombination.Furthermore, ZnFe 2 O 4 /ZnO nanoheterostructures, containing 15 nm size heterojunctions, could be synthesized facilely. We have found that this unique structure endows ZnFe 2 O 4 /ZnO with a large separation of photo-generated carriers. The hydrogen generation rate of ZnFe 2 O 4 /ZnO nanoheterostructures without co-catalysts is up to 2.15 mmol h À1 g À1 under visible light irradiation (l > 420 nm), which is 45 times higher than the best yields ever reported for ZnFe 2 O 4 -based photocatalysts. These research results provide a general and effective route to synthesize other nanoheterostructures for a variety of applications.

Black TiO2 nanomaterials have attracted considerable attention since they usually exhibit excellent photocatalytic activities. Herein, we report the facile preparation of black TiO2 nanostructures with ultrathin hollow sphere morphology, high crystalline quality, small grain size (∼8 nm), and ultrahigh surface area (168.8 m2 g–1) through Al reduction. Electron paramagnetic resonance (EPR) spectra demonstrate the existence of oxygen vacancies in black TiO2 nanostructures, which could increase the donor density and effectively promote the separation and transportation of photogenerated electron–hole pairs. The black TiO2 nanostructures exhibit a high solar-driven hydrogen generation rate (56.7 mmol h–1 g–1) under the full spectrum of solar light, which is nearly 2.5 times than that of pristine TiO2 nanostructures and superior to those kinds of black TiO2 photocatalytic materials reported previously.

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In this work, g-C3N4@TiO2 nanostructures with hollow sphere morphology, small grain size, high crystalline quality, and high surface area are successfully synthesized by the annealing method using melamine and hollowsphere precursor, which could be a universal method to synthesis hollow sphere nanoheterojunction. Excellent photocatalytic property was observed from the as-prepared g-C3N4@TiO2 nanostructure with 466.43 μmol·g–1·h–1 hydrogen generation rate under visible light irradiation (>420 nm), which was 5.5 times as much as the control couple, nanoparticle nanoheterojunction g-C3N4@TiO2. No apparent deactivation was found during the follow-up cycle performance test. The special morphology and the heterojunction construction contribute to both visible light absorption and photogenerated electron–hole pair separation efficiency and finally to the photocatalytic property. The content of g-C3N4 was proved to be an important parameter for the promotion of the photocatalytic property. Overlarge content may lead to lower photogenerated electron–hole pair separation efficiency.

Cu2O/a-Ta2O5 heterostructures exhibited a quantum efficiency level of 3% for overall water splitting under visible light irradiation (400–480 nm).

A novel hierarchical heterostructures based on α-Fe2O3/NiO nanosheet-covered fibers were synthesized using a simple two-step process named the electrospinning and hydrothermal techniques. A high density of α-Fe2O3 nanosheets were uniformly and epitaxially deposited on a NiO nanofibers. The crystallinity, morphological structure and surface composition of nanostructured based on α-Fe2O3/NiO composites were investigated by XRD, SEM, TEM, EDX, XPS and BET analysis. The extremely branched α-Fe2O3/NiO nanosheet-covered fibers delivered an extremely porous atmosphere with huge specific surface area essential for superior gas sensors. Different nanostructured based on α-Fe2O3/NiO composites were also explored by adjusting the volume ratio of the precursors. The as-prepared samples based on α-Fe2O3/NiO nanocomposite sensors display apparently enhanced sensing characteristics, including higher sensing response, quick response with recovery speed and better selectivity towards acetone gas at lower operating temperature as compared to bare NiO nanofibers. The sensing response of S-2 based α-Fe2O3/NiO nanosheet-covered fibers were 18.24 to 100 ppm acetone gas at 169 °C, which was about 6.9 times higher than that of bare NiO nanofibers. The upgraded gas sensing performance of composites based on α-Fe2O3/NiO nanosheet-covered fibers might be ascribed to the exclusive morphologies with large surface area, p-n heterojunctions and the synergetic performance of α-Fe2O3 and NiO.