Light-Induced Proton Pumping with a Semiconductor: Vision for Photoproton Lateral Separation and Robust Manipulation

Abstract

Energy-transfer reactions are the key for living open systems, biological chemical networking, and the development of life-inspired nanoscale machineries. It is a challenge to find simple reliable synthetic chemical networks providing a localization of the time-dependent flux of matter. In this paper, we look to photocatalytic reaction on TiO from different angles, focusing on proton generation and introducing a reliable, minimal-reagent-consuming, stable inorganic light-promoted proton pump. Localized illumination was applied to a TiO surface in solution for reversible spatially controlled "inorganic photoproton" isometric cycling, the lateral separation of water-splitting reactions. The proton flux is pumped during the irradiation of the surface of TiO and dynamically maintained at the irradiated surface area in the absence of any membrane or predetermined material structure. Moreover, we spatially predetermine a transient acidic pH value on the TiO surface in the irradiated area with the feedback-driven generation of a base as deactivator. Importantly we describe how to effectively monitor the spatial localization of the process by the in situ scanning ion-selective electrode technique (SIET) measurements for pH and the scanning vibrating electrode technique (SVET) for local photoelectrochemical studies without additional pH-sensitive dye markers. This work shows the great potential for time- and space-resolved water-splitting reactions for following the investigation of pH-stimulated processes in open systems with their flexible localization on a surface.

Using a chitosan nanolayer as an efficient pH buffer to protect pH-sensitive supramolecular assemblies

“…That is, water splitting on a semiconductor can cause the formation of H + and/or OH À . We recently studied, in detail, the process of water splitting on a titania surface 17 focusing on H + and OH À (not H 2 and O 2 as usual (note, that there is no obvious gas bubbling in our system)) and we observed that this process leads to a pronounced local surface acidification of the irradiated surface and subsequent pH change. The overall pH does not change, although, a pH gradient on the surface may exist.…”

“…The overall pH does not change, although, a pH gradient on the surface may exist. 17 Thus the inorganic surface and its nanostructuring may be involved in the reaction through process location (Fig. 2).…”

Surface Plasmonic‐Assisted Photocatalysis and Optoelectronic Devices with Noble Metal Nanocrystals: Design, Synthesis, and Applications

“…For instance, the light‐induced has strong influence on water‐splitting process in semiconductor materials. Maltanava et al and Ulasevich et al independently introduced the layer‐by‐layer assembly of metal NPs using inorganic TiO 2 materials. Upon UV laser irradiation, they found that the photoactivity of semiconductor materials has strong influence on pH change because of i) the photocatalytic reaction of water splitting, ii) electrochemical process, iii) chemical or biochemical reaction network, and iv) biological process.…”

Photocatalytic Regulation of an Autocatalytic Wave of Spatially Propagating Enzymatic Reactions

“…Notably, the TiO 2 /PSS/PEI film shows much lower photocurrent than TiO 2 one. We propose that the surface states responsible for photoactivation might be the surface states associated with the acidification at the titania surface . It is known that PEI has proton sponge ability .…”

“…On the contrary, having the same photoactivity center (TiO 2 ), it doesn't happen for the system of TiO 2 /PSS/PEI. It should also be noted that the presence of a proton on TiO 2 was shown by us before as well as efficient pH‐buffering of 2 nm chitosan layer …”