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 TiO2 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 TiO2 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 TiO2 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 TiO2 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.
Highlights
Energy transfer reactions are the key for living open systems, biological chemical networking and development of life inspired nanoscale machineries
We question if a semiconductor, e.g. TiO2, surface has a potential as effective photoactive surface to design light controllable networks of chemical reactions with the lateral separation of the two reactions of water splitting
We provide evidence of the possibility of spatial and temporal localization of proton pumping on semiconducting TiO2 with light induced water splitting, and some potential opportunities for designing an open system with localization of both H+ and OH
Summary
Energy transfer reactions are the key for living open systems, biological chemical networking and development of life inspired nanoscale machineries. Today increased interest is focused on dynamic, non-equilibrium material properties varying with time: a life inspired nanoscale machinery [1,2,3,4] It involves needs for effective energy conversion with the focus on oscillation reactions [5], chemical networking [6], autocatalytic [7] and autoamplification [8] reactions, mimicking living systems [9], using cell metabolic biomolecules [10] and ions, e.g. proton gradients [11]. Localization of chemical species may lead to a life inspired proton pump machinery for localization of chemical networks on the surface of TiO2 in an open system, providing further prospects for designing far-from-equilibrium,(26) dynamic [27], oscillation gel materials [28], stimuli-responsive drug delivery systems [29], metastable nanoparticle assemblies [30], reactors to proliferate acidic and basic molecules [7]. We provide evidence of the possibility of spatial and temporal localization of proton pumping on semiconducting TiO2 with light induced water splitting, and some potential opportunities for designing an open system with localization of both H+ and OH–
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