Photoelectrochemical activity of colloidal TiO 2 nanostructures assembled at polarisable liquid/liquid interfaces

Abstract

Photoelectrochemical responses arising from the heterogeneous hole-transfer from colloidal TiO 2 nanoparticles to ferrocene species across the polarizable water/1,2-dichloroethane (DCE) interface are investigated as a function of the formal redox potential of the electron donor. The interfacial assembly of electrostatically stabilized 5 nm TiO 2 colloids was monitored by impedance measurements at various Galvani potential difference across the liquid/liquid interface. The onset potential of the photocurrent responses is close to the potential at which the excess interfacial charge increases due to the assembly of the TiO 2 nanoparticles. However, a closer examination of the potential dependence of these two parameters show that the interfacial excess charge is not solely dependent on the adsorption of charged nanoparticles at the interface.We also provide strong evidence that the photoelectrochemical responses are determined by the relationship between rate of electron capture at the nanoparticle surface and surface A C C E P T E D M A N U S C R I P T ACCEPTED MANUSCRIPT2 recombination processes, rather than the interfacial oxidation of the ferrocene derivatives.Second order surface recombination constants of the order of 10 -3 cm 2 s -1 were estimated, which are consistent with a ~0.6 quantum yield for the heterogenous hole-transfer. Highlights Photoelectrochemical study of colloidal TiO 2 at polarisable liquid/liquid interfaces. Kinetic study of hole-transfer and electron capture involving titania at the ITIES. Incident-photon-to-current efficiency independent of hole-acceptor redox potential. Electron removal (oxygen reduction) is the rate determining step.

Integrating TiO2 Nanoparticles within a Catecholic Polymeric Network Enhances the Photoelectrochemical Response of Biosensors

“…As the concentration of P25-TiO 2 is increased, photocurrent density is enhanced until the P25-TiO 2 concentration is tripled. This observed increase in photocurrent is attributed to the presence of a larger population of P25-TiO 2 nanoparticles within the same geometric area, resulting in the increased absorption and generation of charge carriers . The photocurrent density decrease observed beyond a threefold increase in P25-TiO 2 concentration is attributed to the unavailability of the sufficient amount of DHB–CHIT ligands to obtain films with optimal electronic property, uniformity, surface coverage, and reduced agglomeration.…”

Interfacial Deposition of Titanium Dioxide at the Polarized Liquid–Liquid Interface

“…The placement of TiO 2 -based objects at the ITIES is limited to a few examples. In two elegant works, Jensen et al [ 7 ] and later Plana and Fermin [ 8 ] showed that preformed TiO 2 nanoparticles self-assembled at the electrified water—1,2-dichloroethane (1,2-DCE) interface could be used to generate photocurrent responses when illuminated with laser light. Another report describes coumarin 343 dye TiO 2 nanoparticles complex interfacial adsorption studied with surface second harmonic generation technique [ 9 ].…”

In Situ Microtitration of Intermediates of Water Oxidation Reaction at Nanoparticles Assembled at Water/Oil Interfaces

“…An interface between two immiscible electrolyte solutions (ITIES) is a defect-free (down to the molecular level), self-healing, renewable, and conductive substrate for the preferential and controlled formation of molecular assemblies and nano-object layers that can be polarized. − Similar to solid electrodes, the modifier layer(s) can be formed and/or characterized by charge [using either ion or electron-transfer (ET) processes across the interface]. − The potential drop across the interface can be controlled by the application of a potential difference across the interface either externally using a potentiostat or chemically by dissolving a common salt in both phases . In this regard, interfacial polarization could also effectively drive the interfacial photoinduced e – /h + transfer reactions in a controlled way to produce molecular H 2 in the presence of a molecular photosensitizer − and O 2 in the presence of semiconductor nanomaterials assembled at the ITIES. , The overall process may include heterogeneous reactions of adsorbed species (dyes as sensitizers or reaction intermediates) with dissolved redox species. − The electric field at the interface of ITIES facilitates the spatial separation of photoinduced charge carriers and results in reaction products on either side of the interface, which partially restrict recombination processes …”