Opto-stimulation of semiconductor-biointerfaces provides efficient pathways towards eliciting neural activity through selective spectral excitation. In visual prosthesis, tri-colour stimulation capability is the key to restoring full-colour vision. Here we report on investigation of organic photoactive π-conjugated donor–acceptor small molecules based on triphenylamine whose absorption spectra are similar to those of the photoreceptors of the human eye. Photoactive device fabrication and characterisation towards full colour, pixelated retinal prosthesis based on inkjet printing of these molecules is demonstrated, with round pixels reaching 25 microns in diameter. Photo-response is studied via interfacing with biological electrolyte solution and using long-pulse, narrow-band excitation. Both photo-voltage and photo-current responses in the devices with a ZnO hole-blocking interlayer show clear signatures of capacitive charging at the electrolyte/device interface, also demonstrating spectral selectivity comparable to that of human eye’ cones and rods.
Overall water splitting using a photocatalyst absorbing a wide range of visible light is an ideal means of producing renewable hydrogen, and Nb-based oxynitrides are potential candidates for this purpose due to their narrow band gaps. However, it is challenging to prepare such materials as efficient photocatalysts because Nb⁵⁺ species are readily reduced during synthesis, and the energy offsets between the band edges of such materials and the water redox potentials are small. In this study, a series of LaMgₓNb₁₋ₓO₁₊₃ₓN₂₋₃ₓ solid solutions (0.0 ≤ x ≤ 0.5) was synthesized in an attempt to modify the band structures and improve the water splitting activity of these compounds. The substitution of Mg²⁺ enlarged the band gap of LaNbON₂, shifting the conduction and valence band edges negatively and positively, respectively, while retaining visible light absorption up to 600 nm and beyond. Moreover, the concentrations of reduced Nb species at the oxynitride surfaces generated during nitridation were significantly decreased with increasing Mg²⁺ content. As a result, increasing the amount of Mg²⁺ in these materials enhanced their photocatalytic H₂ evolution activity. Moreover, the co-loading of RhCrOy and CoOz as cocatalysts for water reduction and oxidation, respectively, allowed LaMgₓNb₁₋ₓO₁₊₃ₓN₂₋₃ₓ (0.2 ≤ x ≤ 0.5) to simultaneously evolve gaseous H₂ and O₂ from water under visible light (λ > 420 nm). These observations demonstrate the effectiveness of this band engineering technique and the necessity for further refinements of material properties and surface modifications to realize visible-light-driven overall water splitting over Nb-based oxynitrides.
A shape-memory monolith has been used as a new emerging class of foldable nitrogen-fixing electrocatalysts, which shows remarkable activities both with and without electrode deformations.
PDI-TTMSS exhibits peculiar monotropic phase transition behaviors originated from flexible siloxane substituents.
NaNbO3-based (NN) energy storage ceramics exhibit high breakdown electric field strength (Eb) with large recoverable energy storage density (Wrec).
