Observation of an Orientation Change in Highly Oriented Layer-by-Layer Films of a Ruthenium Complex upon Oxidation Reaction

Extraction of Au(III) by Microbially Reduced Metal-Organic Frameworks

Gold is a critical resource in the jewelry and electronics industries and is facing increased consumer demand. Accordingly, methods for its extraction from waste effluents and environmental water sources have been sought to supplement existing mining infrastructure. Redox-mediated treatments, such as Fe(II)-based platforms, offer promise for precipitating soluble Au(III). We hypothesized that microbial generation of Fe(II) in the presence of sorbent metal-organic frameworks could capitalize on the advantages of both biological- and chemical-driven extraction approaches. Toward this aim, we tested Au(III) removal by Shewanella oneidensis cultured with Fe(III)-based materials (ferrihydrite, Fe-BTC, MIL-100, or MIL-127). Across all tested materials, S. oneidensis generated the highest levels of redox-active Fe(II) (1.99 ± 0.27 mM) when cultured with MIL-127 as a respiratory substrate in a bicarbonate-buffered medium. This translated into superior Au(III) removal performance in terms of both removal rate and capacity (k = 2.55 ± 0.60 h^-1; Q = 183 mg g^-1). Unlike other materials tested, MIL-127 also maintained cell viability following repeated Au(III) challenges, enabling the regeneration of Fe(II) in the framework. Together, these effects facilitated the treatment of multiple cycles of Au(III) by S. oneidensis-reduced MIL-127. Overall, this work demonstrates that microbial generation of Fe(II) can facilitate the removal of Au(III), augmenting purely adsorptive platforms. Given the biological and chemical modularity of our system, our results suggest that future optimizations to microbial Fe(II) generation may offer promise for improving Au(III) extraction processes.

Construction of Ultrathin Layer-by-Layer Films of Oligothiophene Derivatives on an Electrode

Oligothiophene derivatives, which are known as p-type materials, have been synthesized, and their ultrathin layer-by-layer films have been constructed on an electrode using a simple and convenient dipping method. The stepwise deposition behavior of quaterthiophene and sexithiophene derivatives on the electrode via hydrogen bonding was monitored by electronic spectra measurement, and the constructed films were evaluated by X-ray photoelectron spectroscopy, grazing-incidence small-angle X-ray scattering, and cyclic voltammetry. It has been clarified that the constructed layer-by-layer films were electroactive and photoelectroactive.

Effects of Fe cations in ruthenium-complex multilayers fabricated by a layer-by-layer method

Molecular multilayers were fabricated using a Ru complex containing Fe cations on an indium tin oxide surface to control the properties of the Ru-complex multilayers such as the multilayer orientation and the electron transport.