Glucose oxidase (GOD) is immobilized, for the first time, on a hierarchical nanoporous carbon (HNC) with rich functional groups by carbonizing a biomass derivation extracted from green tree leaves on a nanostructured CaCO₃ template at high temperature, which exhibits fast electrooxidation for glucose and direct electron transfer (DET) when using the GOD catalyst on the new carbon support, delivering 6 and 12 times higher kinetic currents for electrochemical glucose sensing without additional electron mediators compared to commercial activated carbon and conventional hierarchical nanoporous carbon, respectively. The appearance of multiple surface heteroatom functional groups, such as amines, amides and thiols, which remain when the biomass is carbonized, rather than surface hydrophilicity, is associated with the appearance of facile direct electrochemistry processes, thus offering a new insight into DET for inexpensive and highly sensitive enzymatic sensors.

A flexible memory device with an ITO/BiFeO₃/Ti/Polyimide structure is prepared for light-controlled simultaneous resistive and ferroelectricity switching effects, achieving a multistate high-storage memory capacity. The mechanism for superior storage performance is discussed in detail. This work holds a great promise for a flexible and wearable light-controlled non-volatile multistate memory device with a high capacity and low cost.

It is important to detect reactive oxygen species (ROS) in situ for investigation of various critical biological processes, and this is however very challenging because of the limited sensitivity or/and selectivity of existing methods that are mainly based on sensing ROS released by cells with short lifetimes and low concentrations in a culture medium. Here, a new approach is reported to directly grow living cells on DNA/Mn₃(PO₄)₂-immobilized and vertically aligned carbon nanotube (VACNT) array nanostructure as a smart free-standing hybrid film, of which the DNA/Mn₃(PO₄)₂ and VACNT provide high electroactivity and excellent electron transport, respectively, while the directly grown cell on the nanostructure offers short diffusion distance to reaction sites, thus constructing a highly sensitive in situ method for detection of cancer-cell-released ROS under drug stimulations. Compared to the measured ROS released by cells in a culture medium, the detection sensitivity with this constructed hybrid film increases by more than six times, which implies that ROS molecules (superoxide anions) secreted from living cells are immediately captured by this smart structure without diffusion process or with extremely short diffusion distance. This design considerably reduces the time from release to detection of the target molecules, minimizing the potential molecular decay due to the short lifetime or high reactivity.

Hydrogen production from water splitting using solar energy based on photoelectrochemical (PEC) cells has attracted increasing attention because it leaves less of a carbon footprint and has economic superiority of solar and hydrogen energy. Oxide semiconductors such as ZnO possessing high stability against photocorrosion in hole scavenger systems have been widely used to build photoanodes of PEC cells but under visible light their conversion efficiencies with respect to incident-photon-to-current conversion efficiency (IPCE) measured without external bias are still not satisfied. An innovative way is presented here to significantly improve the conversion efficiency of PEC cells by constructing a core–shell structure-based photoanode comprising Au@CdS core–shell nanoparticles on ZnO nanowires (Au@CdS-ZnO). The Au core offers strong electronic interactions with both CdS and ZnO resulting in a unique nanojunction to facilitate charge transfer. The Au@CdS-ZnO PEC cell under 400 nm light irradiation without any applied bias provides an IPCE of 14.8%. Under AM1.5 light illumination with a bias of 0.4 V, the Au@CdS-ZnO PEC cell produces H2 at a constant rate of 11.5 μmol h⁻¹ as long as 10 h. This work provides a fundamental insight to improve the conversion efficiency for visible light in water splitting.

Superoxide anion (O₂⁻) is implicated in a wide variety of biological phenomena and oxidative stress-related diseases. The electrochemical detection of O₂⁻ is very attractive but relies on superoxide dismutase enzymes, thus suffering from high cost and low durability. The advances of nanoscience allows architecting while functionalizing a biomimetic sensing platform in nanoscales for high sensitivity and specificity. In this work, manganous phosphate (Mn₃(PO₄)₂) nanosheets, a biomimetic enzyme, are template-synthesized with DNA and further assembled on carbon nanotubes (CNTs) to form unique DNA-Mn₃(PO₄)₂-CNT nanocomposite sheets, of which the Mn₃(PO₄)₂ sheets efficiently catalyze the dismutation of O₂⁻ while CNTs enable fast electron transfer, thus achieving highly sensitive and specific detection of O₂⁻ with long-term stability. The biomimetic O₂⁻ sensor is further used to monitor O₂⁻in situ released from mouse cancer cell and normal skin cell under drug stimulation, showing excellent real time quantitative detection capability. This work demonstrates a nanoscale approach to not only synthesize but also design a biomimetic enzyme for comparable performance with the natural enzyme-based biosensor while rendering much higher durability than the natural one and thus holding a great promise for broad applications in fundamental research, clinic diagnostics and screening for drug therapy effects.

A potassium tungstate (K_0.33WO₃) nanosheet film grown directly on a conductive tungsten (W) substrate by a hotplate-heating approach effects direct electron transfer between the W electrode and a biocatalytic protein or microbe, a long-sought effect of both fundamental and practical importance. The K_0.33WO₃ forms into a 5–20 nm thick multilayered nanosheet with a number of steps along the surface. A single nanosheet of K_0.33WO₃ is hydrophilic and highly electron conducting (resistivity ∼8.3×10⁻³ Ω cm), characteristic of metallic behaviour. Glucose oxidase (GOD) immobilized on a K_0.33WO₃-nanosheet-coated electrode demonstrates facile direct electron transfer. The electron transfer rate constant (k_s) is ∼9.5 s⁻¹. This electrode has been used to construct a direct electrochemistry-based glucose sensor, which exhibits good sensitivity (as high as ∼66.4 μA mM⁻¹ cm⁻²), fast sensing response time (∼4 s), a low detection limit (0.5 μM), high selectivity and good reliability in practical uses. Growing K_0.33WO₃ nanosheet on electrodes offers a promising general approach for effecting direct bioelectrochemistry for widespread uses in bioelectronic and bioenergy applications.