Photoelectrochemical oxidation of a turn-on fluorescent probe mediated by a surface MnII catalyst covalently attached to TiO2 nanoparticles

Design of robust 2,2'-bipyridine ligand linkers for the stable immobilization of molecular catalysts on silicon(111) surfaces

The attachment of the 2,2'-bipyridine (bpy) moieties to the surface of planar silicon(111) (photo)electrodes was investigated using ab initio simulations performed on a new cluster model for methyl-terminated silicon. Density functional theory (B3LYP) with implicit solvation techniques indicated that adventitious chlorine atoms, when present in the organic linker backbone, led to instability at very negative potentials of the surface-modified electrode. In prior experimental work, chlorine atoms were present as a trace surface impurity due to required surface processing chemistry, and thus could plausibly result in the observed surface instability of the linker. Free energy calculations for the Cl-atom release process with model silyl-linker constructs revealed a modest barrier (14.9 kcal mol-1) that decreased as the electrode potential became more negative. A small library of new bpy-derived structures has additionally been explored computationally to identify strategies that could minimize chlorine-induced linker instability. Structures with fluorine substituents are predicted to be more stable than their chlorine analogues, whereas fully non-halogenated structures are predicted to exhibit the highest stability. The behavior of a hydrogen-evolving molecular catalyst Cp*Rh(bpy) (Cp* = pentamethylcyclopentadienyl) immobilized on a silicon(111) cluster was explored theoretically to evaluate differences between the homogeneous and surface-attached behavior of this species in a tautomerization reaction observed under reductive conditions for catalytic H2 evolution. The calculated free energy difference between the tautomers is small, hence the results suggest that use of reductively stable linkers can enable robust attachment of catalysts while maintaining chemical behavior on the electrode similar to that exhibited in homogeneous solution.

Aggregation induced emission (AIE) active 4-amino-1,8-naphthalimide-Tröger's base for the selective sensing of chemical explosives in competitive aqueous media

The 4-amino-1,8-naphthalimide Tröger's base based AIE-active supramolecular scaffold was synthesized and employed as a highly selective and sensitive fluorescent sensor for nitroaromatic explosives sensing in competitive aqueous media.

Water Oxidation Catalysts for Artificial Photosynthesis

Water oxidation is the primary reaction of both natural and artificial photosynthesis. Developing active and robust water oxidation catalysts (WOCs) is the key to constructing efficient artificial photosynthesis systems, but it is still facing enormous challenges in both fundamental and applied aspects. Here, the recent developments in molecular catalysts and heterogeneous nanoparticle catalysts are reviewed with special emphasis on biomimetic catalysts and the integration of WOCs into artificial photosystems. The highly efficient artificial photosynthesis depends largely on active WOCs integrated into light harvesting materials via rational interface engineering based on in-depth understanding of charge dynamics and the reaction mechanism.

Visible-light degradation of Orange II using an Fe(II)–terpyridine complex grafted onto TiO2 surface

The photo-Fenton process employs light, iron species, and H2O2 to oxidize organic pollutants. In this study, a coordination complex, Fe(II)–terpyridine, was covalently grafted onto TiO2 surfaces via a light-harvesting linkage for use in the photo-Fenton reaction. The surface Fe(II)–terpyridine complex was characterized with techniques, including microscopy and spectroscopy, and was investigated in the degradation of Orange II in the presence of H2O2. Under visible-light irradiation, slightly higher activity was obtained using the surface Fe(II)–terpyridine catalyst than using photoactivated TiO2 nanoparticles under UV light. Furthermore, the Fe(II)–terpyridine complex grafted on TiO2 showed significantly greater activity than the same complex grafted on ZrO2 in the degradation of Orange II. A possible explanation for this observation was discussed that involves the formation of high valent oxoiron species on TiO2 in the photo-Fenton process.