Photocurrent generation in layer-by-layer assembled dendrimers with ruthenium tris-bipyridine peripheral groups and a viologen-like core

Electrochemical and Photoelectrochemical Investigation of New Self-Assembled Films Based on Prussian Blue and a Terpyridyl RuII Complex

A new hybrid multilayer film containing Prussian blue (PB) and a bis-terpyridyl RuII complex of RuII(L)2(ClO4)2 (in which L = 4′-(4-(imidazol-1-yl)phenyl)-2,2′:6′,2″-terpyridine), was fabricated though covalently and electrostatic layer-by-layer self-assembly techniques, and characterised by UV-vis absorption spectroscopy, cyclic voltammetry, and photoelectrochemical techniques. The results demonstrated that the two film-forming components were successfully transferred into the hybrid film, which exhibited three quasi-reversible redox couples centred at 0.06, 0.76, and 1.0 V. The photoelectrochemical studies showed that an 11-layer film exhibited a large cathodic photocurrent density of 7.72 μA cm–2 while irradiated with 100 mW cm–2 polychromatic light (325 < λ < 730 nm) at an applied potential of –0.2 V versus a saturated calomel electrode.

Benzylic viologen dendrimers: a review of their synthesis, properties and applications

Dendrimers containing benzylic viologen branching units, their guest complexation, photophysical and biological applications has been reviewed.

Dye-Sensitized Nanostructured Crystalline Mesoporous Tin-doped Indium Oxide Films with Tunable Thickness for Photoelectrochemical Applications

A simple route towards nanostructured mesoporous Indium-Tin Oxide (templated nano-ITO) electrodes exhibiting both high conductivities and optimized bicontinuous pore-solid network is reported. The ITO films are first produced as an X-ray-amorphous, high surface area material, by adapting recently established template-directed sol-gel methods using Sn(IV) and In(III) salts. Carefully controlled temperature/atmosphere treatments convert the as-synthesized ITO films into nano-crystalline coatings with the cubic bixbyite structure. Specially, a multi-layered synthesis was successfully undertaken for tuning the film thickness. In order to evaluate the performances of templated nano-ITO as an electrode substrate for photoelectrochemical applications, photoelectrodes were prepared by covalent grafting of a redox-active dye, the complex [Ru(bpy)₂(4,4'-(CH₂PO₃H₂)₂-bpy)]Cl₂1 (bpy=bipyridine). Surface coverage was shown to increase with the film thickness, from 0.7 × 10^-9 mol.cm^-2 (one layer, 45 nm) to 3.5 × 10^-9 mol.cm^-2 (ten layers, 470 nm), the latter value being ~ 100 times larger than that for commercially available planar ITO. In the presence of an electron mediator, photocurrents up to 50 μA.cm^-2 have been measured under visible light irradiation, demonstrating the potential of this new templated nano-ITO preparation for the construction of efficient photoelectrochemical devices.

Modeling the buildup of exponentially growing polyelectrolyte multilayer films

We develop a simplified one-dimensional model to describe the build-up of exponentially growing polyelectrolyte multilayer films. The model accounts for the migration of polycations in and out of the film, the existence of an energetic barrier at the film surface, and film dissolution. All the electrostatic interactions are modeled using a screened Coulombic potential. For appropriately chosen model parameters, the model predictions are in quantitative agreement with experimental results. The model predicts that the exponential-to-linear growth transition is set kinetically, and this transition occurs when the dipping time is not long enough for unbound polycations to uniformly distribute inside the film. Additionally, for a film to exhibit exponential growth, it is essential that very few unbound polycations move out of the film during the rinsing step that follows after dipping in a solution of polycations. The model predicts that this criterion is satisfied either when a sharply peaked energetic barrier is present at the film surface or when the film swells. Furthermore, the model predicts that when dipping time, t(d), is increased proportionally with H(2), where H is the film thickness, the film will grow exponentially as long as k(d)t(d) << 1, where k(d) is the dissolution rate. The results of this work shed light on the criteria that need to be satisfied for a film to grow exponentially, and could help in exercising better control over the thickness of polyelectrolyte multilayer films.