A Self-Assembled Organic/Metal Junction for Water Photo-Oxidation.

We report the in situ self-assembly of TTF, TTF•+, and BF4- or PF6- into p-type semiconductors on the surface of Pt microparticles dispersed in water/acetonitrile mixtures. The visible light photoactivation of these self-assemblies leads to water oxidation forming O2 and H+, with an efficiency of 100% with respect to the initial concentration of TTF•+. TTF•+ is then completely reduced to TTF upon photoreduction with water. The Pt microparticles act as floating microelectrodes whose Fermi level is imposed by the different redox species in solution; here predominantly TTF, TTF•+, and HTTF+, which furthermore showed no signs of decomposition in solution.

The effect of the functionalization and molecular weight of cationic dextran polyelectrolytes on their electrochemical behavior at the water/1,2-dichloroethane interface.

The electrochemical behaviour of several cationic dextran polyelectrolytes, aminodextran (AD), cationic dextran (CD) and diethylaminoethyl dextran (DEAE-D), at the polarized water/1,2-dichloroethane interface was studied. An investigation into the influence of the scan rate, concentration, pH, the nature and the concentration of the anion present in the organic electrolyte and the effect of the polymer molecular weight is presented. Different responses were obtained and explained considering the structural difference between these species, mainly the position of the positive charge in the macromolecule. The AD polymer is not transferred to the organic phase, regardless of molecular weight, while CD and DEAE-D are transferred from the aqueous to the organic phase at E = 0.650 V, independent of the polymer concentration and of the molecular weight. The shape of the voltammograms corresponding to DEAE-D transfer as well as the magnitude of the peak currents and the peak potential values were all dependent on the pH of the aqueous phase solution and on the nature and concentration of the anion present in the organic electrolyte. Based on this dependence, we postulated a mixed mechanism, which involves the transfer of dissolved and adsorbed DEAE-D molecules.

Magnetically controlled insertion of magnetic nanoparticles into membrane model.

Polysaccharide-coated magnetic nanoparticles (MNPs) have been reported to show potential applications in many biomedical fields. In this report, we have studied the interactions between magnetite (Fe3O4) MNPs functionalized with polysaccharides (diethylamino-ethyl dextran, DEAE-D or chitosan, CHI) with different membranes models by Langmuir isotherms, incorporation experiments, and brewster angle microscopy (BAM). In this report, zwitterionic 1,2-distearoyl-sn-glycerol-3-phosphoethanolamine (DSPE) and anionic 1,2-distearoyl-sn-glycerol-3-phosphate (DSPA) phospholipid, were used to form membrane models. Incorporation experiments (π-t) as well as the compression isotherms demonstrate positive interactions between MNPs and DSPE or DSPA monolayers. The study assessed the impact of varying initial surface pressure on a preformed phospholipid monolayer to determine the maximum insertion pressure (MIP) and synergy. Our findings indicate that the primary driving force of the coated MNPs incorporation into the monolayer predominantly stems from electrostatic interaction. The drop in the subphase pH from 6.0 to 4.0 led to an enhancement of the MIP value for DSPA phospholipid monolayer. On the other hand, for DSPE, the drop in the pH does not affect the MIP values. Besides, the presence of a magnetic field induces an enhancement of the insertion process of the MNPs into DSPA preformed monolayer, demonstrating that a previous interaction between MNPs and phospholipid preformed monolayer needs to take place to enhance the incorporation process. This work opens novel perspectives for the research of the influence of magnetic fields on the incorporation of MNPs into model membranes.

Visible-light driven water oxidation and oxygen production at soft interfaces.

The visible light driven water oxidation reaction (WOR) by the organic electron acceptor 2,3,5,6-tetrafluoro-7,7,8,8-tetracyano-quinodimethane (TCNQF4) was studied at the water|butyronitrile interface. The WOR was performed at neutral pH, and without any metal or organometallic catalysts. The oxygen generated was measured by GC-MS and cyclic voltammetry, and the protons produced were monitored by measuring the aqueous pH. This work opens novel perspectives for water photo-oxidation in liquids and artificial photosynthesis.

Visible-Light-Driven Water Oxidation on Self-Assembled Metal-Free Organic@Carbon Junctions at Neutral pH.

Sustainable water oxidation requires low-cost, stable, and efficient redox couples, photosensitizers, and catalysts. Here, we introduce the in situ self-assembly of metal-atom-free organic-based semiconductive structures on the surface of carbon supports. The resulting TTF/TTF•+@carbon junction (TTF = tetrathiafulvalene) acts as an all-in-one highly stable redox-shuttle/photosensitizer/molecular-catalyst triad for the visible-light-driven water oxidation reaction (WOR) at neutral pH, eliminating the need for metallic or organometallic catalysts and sacrificial electron acceptors. A water/butyronitrile emulsion was used to physically separate the photoproducts of the WOR, H+ and TTF, allowing the extraction and subsequent reduction of protons in water, and the in situ electrochemical oxidation of TTF to TTF•+ on carbon in butyronitrile by constant anode potential electrolysis. During 100 h, no decomposition of TTF was observed and O2 was generated from the emulsion while H2 was constantly produced in the aqueous phase. This work opens new perspectives for a new generation of metal-atom-free, low-cost, redox-driven water-splitting strategies.