The application of TiO₂ nanoparticles in the photocatalytic treatment of chemically or biologically contaminated water is an attractive, albeit unoptimized, method for environmental remediation. Here, TiO₂ nanoparticles with mixed brookite/rutile phases were synthesized and calcined at 300–1100 °C to investigate trends in photocatalytic performance. The crystallinity, crystallite size, and particle size of the calcined materials increased with calcination temperature, while the specific surface area declined significantly. The TiO₂ phase composition varied: at 300 °C, mixed brookite/rutile phases were observed, whereas a brookite-to-anatase phase transformation occurred above 500 °C, reaching complete conversion at 700 °C. Above 700 °C, the anatase-to-rutile phase transformation began, with pure rutile attained at 1100 °C. The optical band gaps of the calcined TiO₂ nanoparticles decreased with rising calcination temperature. The mixed anatase/rutile phase TiO₂ nanoparticles calcined at 700 °C performed best in the photocatalytic degradation of methylene blue owing to the synergistic effect of the crystallinity and phase structure. The photocatalytic virus inactivation test demonstrated excellent performance against the MS2 bacteriophage, murine norovirus, and influenza virus. Therefore, the mixed anatase/rutile phase TiO₂ nanoparticles calcined at 700 °C may be considered as potential candidates for environmental applications, such as water purification and virus inactivation.

Boron-doped graphene quantum dots (BGQDs) have been synthesized by a one-step, facile and low temperature method through the hydrothermal treatment of glucose as the precursor in the presence of boric acid. The as-obtained BGQDs possess a high B-doping content up to 4.25% of uniform nm-size. Interestingly, the effect of different types of B–C bond species on the ORR catalytic activity has been investigated to clarify the origin of the electrochemical reduction of O₂. Further, the composite of the reduced graphene oxide (rGO) and BGQD (G-BGQDs) was also prepared as a metal-free electrocatalyst for the oxygen reduction reaction (ORR). The G-BGQD composites exhibit a significantly enhanced electrocatalytic activity, including a positive onset potential and a high current density with a one step, four-electron pathway toward the ORR, comparable to the commercial Pt/C catalyst. Among various B–C bond structures in BGQDs, the graphite-like BC₃ structure is considered to be an important site for the ORR by improving the electric conductivity and electrocatalytic activity of BGQDs, which is also confirmed by a DFT study. In addition, the G-BGQD composites show an outstanding long-term operational stability and high tolerance to the methanol crossover effect, which are comparable to the commercial Pt/C catalyst. These results demonstrate that the synthesized BGQD, as metal-free catalyst materials, may be inexpensive and efficient electrocatalysts for the replacement of Pt-based catalysts toward the ORR and other electrochemical applications.

1T exfoliated MoS₂@CNT-based bifunctional separators in a tandem configuration delivered excellent electrochemical performance, and rational guidelines for preparing bifunctional separators for lithium sulfur batteries were suggested.

Electronic retinal prostheses for stimulating retinal neurons are promising for vision restoration. However, the rigid electrodes of conventional retinal implants can inflict damage on the soft retina tissue. They also have limited selectivity due to their poor proximity to target cells in the degenerative retina. Here we present a soft artificial retina (thickness, 10 μm) where flexible ultrathin photosensitive transistors are integrated with three-dimensional stimulation electrodes of eutectic gallium–indium alloy. Platinum nanoclusters locally coated only on the tip of these three-dimensional liquid-metal electrodes show advantages in reducing the impedance of the stimulation electrodes. These microelectrodes can enhance the proximity to the target retinal ganglion cells and provide effective charge injections (72.84 mC cm⁻²) to elicit neural responses in the retina. Their low Young’s modulus (234 kPa), owing to their liquid form, can minimize damage to the retina. Furthermore, we used an unsupervised machine learning approach to effectively identify the evoked spikes to grade neural activities within the retinal ganglion cells. Results from in vivo experiments on a retinal degeneration mouse model reveal that the spatiotemporal distribution of neural responses on their retina can be mapped under selective localized illumination areas of light, suggesting the restoration of their vision.