How do plants see the world? - UV imaging with a TiO2 nanowire array by artificial photosynthesis.

The concept of plant vision refers to the fact that plants are receptive to their visual environment, although the mechanism involved is quite distinct from the human visual system. The mechanism in plants is not well understood and has yet to be fully investigated. In this work, we have exploited the properties of TiO2 nanowires as a UV sensor to simulate the phenomenon of photosynthesis in order to come one step closer to understanding how plants see the world. To the best of our knowledge, this study is the first approach to emulate and depict plant vision. We have emulated the visual map perceived by plants with a single-pixel imaging system combined with a mechanical scanner. The image acquisition has been demonstrated for several electrolyte environments, in both transmissive and reflective configurations, in order to explore the different conditions in which plants perceive light.

Charge separation properties of Ta3N5 photoanodes synthesized via a simple metal-organic-precursor decomposition process.

Here, we successfully synthesized a Ta3N5 thin film using a simple metal-organic-precursor decomposition process followed by its conversion to nitride and studied its photoelectrochemical (PEC) properties to understand charge separation on the surface. Newly synthesized Ta3N5 photoanodes showed a significant difference in the PEC activity in relation to the annealing temperature under ammonia flow, although similar light absorption properties or electronic states were obtained. Charge separation related PEC properties were analyzed using intensity modulated photocurrent density spectroscopy (IMPS) and photocurrent measurements in the absence/presence of scavengers. The charge transfer and recombination rate constants which are related to the photogenerated charge-separation dynamics on the Ta3N5 surface were found to be more sensitively influenced by the ammonia annealing temperatures, and low temperature (700 °C) treated Ta3N5 showed a fast recombination rate constant (kr). In addition, high-efficiency charge injection into the electrolyte on the surface was critically associated with the greatly enhanced photocurrent density of Ta3N5 synthesized at a higher temperature (900 °C) of ammonia annealing.

Enhanced Photocurrents with ZnS Passivated Cu(In,Ga)(Se,S)2 Photocathodes Synthesized Using a Nonvacuum Process for Solar Water Splitting.

Chalcopyrite Cu(In,Ga)(Se,S)2 (CIGS) semiconductors are potential candidates for use in photoelectrochemical (PEC) hydrogen generation due to their excellent optical absorption properties and high conduction band edge position. In the present research, CIGS thin film was successfully prepared on a transparent substrate (F:SnO2 glass) using a solution-based process and applied for a photocathode in solar water splitting, which shows control of the surface state associated with sulfurization/selenization process significantly influences on the PEC activity. A ZnS passivation surface layer was introduced, which effectively suppresses charge recombination by surface states of CIGS. The CIGS/ZnS/Pt photocathode exhibited highly enhanced PEC activity (∼24 mA·cm-2 at -0.3 V vs RHE). The performances of our CIGS photocathode on the transparent substrate were also characterized under front/back light illumination, and the incident photon to current conversion efficiency (IPCE) drastically changed depending on the illumination directions showing decreased IPCE especially under UV region with back illumination. The slow minority carrier (electron) transportation is suggested as a limiting factor for the PEC activity of the CIGS photocathode.