Tungsten oxide (WO 3 ) and bismuth vanadate (BiVO 4 ) are one of the most attractive combinations to construct an efficient heterojunction for photoelectrochemical (PEC) applications. Here, we report an all-solution-processed WO 3 /BiVO 4 heteronanostructure photoanode with highly enhanced photoactivity and stability for sustainable energy production. The vertically aligned WO 3 nanorods were synthesized on a fluorine-doped tin oxide/glass substrate by the hydrothermal method without a seed layer and BiVO 4 was deposited by pulsed electrodeposition for conformal coating. Owing to the long diffusion lengths of charge carriers in the WO 3 nanorods, the ability to absorb the wider range of wavelengths, and appropriate band-edge positions of the WO 3 /BiVO 4 heterojunction for spontaneous PEC reaction, the optimum WO 3 /BiVO 4 photoanode has a photocurrent density of 4.15 mA/cm 2 at 1.23 V versus RHE and an incident-photonto-current efficiency of 75.9% at 430 nm under front illumination, which are a double and quadruple those of pristine WO 3 nanorod arrays, respectively. Our work suggests an environment-friendly and low-cost all-solution process route to synthesize high-quality photoelectrodes.

The detection of ions and molecules in liquids has been receiving considerable attention for the realization of the electronic tongue. Solution-gated field-effect transistors (SFETs) with high sensitivity are useful for detecting ions and molecules by reading electrical transconductance. However, to date, ionic and molecular sensors that employ SFETs have limitations, such as the lack of a dynamic on–off function and low selectivity. In this study, we evaluate rationally designed graphene SFETs as pH and glucose-selective sensors. The integration of the microfluidic channel to the graphene SFET exhibits dynamic on–off functions by controlling injection and withdrawal of solutions. The graphene SFET device exhibits high pH and glucose selectivity when coated with Nafion as a molecular sieve and Au-decorated nanoparticles as receptors, respectively. The dynamic on–off functions and high selectivity of SFETs with tailored graphene channels have a high potential for advancing as a platform for electronic tongues by integrating the separate SFETs as an array for simultaneous sensing of multiple targets.

As the interest in sustainable energy production increases, water splitting through semiconductor materials to convert solar energy directly to hydrogen energy has been extensively reported to date. Recently, the III-VI group chalcogenide semiconductors have received great attention for narrow-gap photoelectrochemical (PEC) water splitting electrodes. Among the metal sulfides, beta indium sulfide (β-In 2 S 3 ) shows remarkable properties for photoelectrodes such as high photoelectric sensitivity, high photoconductivity, large photoelectric conversion yield, low toxicity, high absorption coefficient, efficient charge separation, moderate charge transport, appropriate band position, and narrow band gap. Most of its unique properties come from the defective spinel crystal structure. Despite the superior advantages, there is a serious problem of photocorrosion induced by accumulated holes on the surface of the electrodes during the photocatalytic reaction under illumination which reduces the PEC properties. Herein, we review overall physicochemical and optoelectronic properties of β-In 2 S 3 , regardless of pros and cons, followed by the discussion of assorted strategies to further improve the PEC activities.

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