Photosynthesis is an efficient mechanism for converting solar light energy into chemical energy. We report on a strategy for the aerobic photocyanation of tertiary amines with visible and near-infrared (NIR) light. Panchromatic sensitization was achieved by functionalizing TiO 2 with a 2methylisoquinolinium chromophore, which captures essential features of the extended π-system of 2,7-diazapyrenium (DAP 2+ ) dications or graphitic carbon nitride. Two phenolic hydroxy groups make this ligand highly redoxactive and allow for efficient surface binding and enhanced electron transfer to the TiO 2 surface. Non-innocent ligands have energetically accessible levels that allow redox reactions to change their charge state. Thus, the conduction band is sufficiently high to allow photochemical reduction of molecular oxygen, even with NIR light. The catalytic performance (up to 90% chemical yield for NIR excitation) of this panchromatic photocatalyst is superior to that of all photocatalysts known thus far, enabling oxidative cyanation reactions to the corresponding α-cyanated amines to proceed with high efficiency. The discovery that the surface-binding of redox-active ligands exhibits enhanced light-harvesting in the red and NIR region opens up the way to improve the overall yields in heterogeneous photocatalytic reactions. Thus, this class of functionalized semiconductors provides the basis for the design of new photocatalysts containing non-innocent donor ligands. This should increase the molar extinction coefficient, permitting a reduction of nanoparticle catalyst concentration and an increase of the chemical yields in photocatalytic reactions.

Localized surface plasmon resonance properties in unconventional materials like metal oxides or chalcogenide semiconductors have been studied for use in signal detection and analysis in biomedicine and photocatalysis. We devised...

Organized three-dimensional (3D) nanomaterial architectures are promising candidates for applications in optoelectronics, catalysis, or theranostics owing to their anisotropy and advanced structural features that allow tailoring their physical and chemical properties. The synthesis of such complex but well-organized nanomaterials is difficult because the interplay of interfacial strain and facet-specific reactivity must be considered. Especially the magnetic anisotropy with controlled size and morphology plays a decisive role for applications like magnetic resonance imaging (MRI) and advanced data storage. We present a solution phase seed mediated synthesis of colloidal, well dispersible iron oxide superparticles with flower- and hedgehog-like morphology starting from dispersible spherical maghemite (SPH) and nanoplate hematite (HEX) templates. In the superparticles the templates are epitaxially decorated with nanodomains and nanorods as shown by (high-resolution) transmission electron microscopy (TEM), orientation mapping, and electron diffraction (ED). While the templates determine the morphology of the superparticles, the solution chemistry determines the phase identity. Oxidation of Fe­(CO)5 during superparticle formation reaction leads to maghemite nanodomains and nanorods decorating the templates, unveiled by a combination of X-ray diffraction (XRD) and Mössbauer spectroscopy (MS). After hydrophilic surface functionalization the superparticles are well dispersible. The cytotoxicity of templates and superparticles is low. The magnetic resonance imaging R2-relaxivity of the flower-like superparticles could be increased by a factor 2.5 compared to its spherical nanoparticle template due to direct interfacial connection resulting from the unique nanoarchitecture.

Modifying the surfaces of metal oxide nanoparticles (NPs) with monolayers of ligands provides a simple and direct method to generate multifunctional coatings by altering their surface properties. This works best if the composition of the monolayers can be controlled. Mussel-inspired, noninnocent catecholates stand out from other ligands like carboxylates and amines because they are redox-active and allow for highly efficient surface binding and enhanced electron transfer to the surface. However, a comprehensive understanding of their surface chemistry, including surface coverage and displacement of the native ligand, is still lacking. Here, we unravel the displacement of oleate (OA) ligands on hydrophobic, OA-stabilized TiO2 NPs by catecholate ligands using a combination of one- and two-dimensional nuclear magnetic resonance (NMR) spectroscopy techniques. Conclusive pictures of the ligand shells before and after surface modification with catecholate were obtained by 1H and 13C NMR spectroscopy (the 13C chemical shift being more sensitive and with a broader range). The data could be explained using a Langmuir-type approach. Gradual formation of a mixed ligand shell was observed, and the surface processes of catecholate adsorption and OA desorption were quantified. Contrary to the prevailing view, catecholate displaces only a minor fraction (∼20%) of the native OA ligand shell. At the same time, the total ligand density more than doubled from 2.3 nm–2 at native oleate coverage to 4.8 nm–2 at maximum catecholate loading. We conclude that the catecholate ligand adsorbs preferably to unoccupied Ti surface sites rather than replacing native OA ligands. This unexpected behavior, reminiscent of the Vroman effect for protein corona formation, appears to be a fundamental feature in the widely used surface modification of hydrophobic metal oxide NPs with catecholate ligands. Moreover, our findings show that ligand displacement on OA-capped TiO2 NPs is not suited for a full ligand shell refunctionalization because it produces only mixed ligand shells. Therefore, our results contribute to a better understanding and performance of photocatalytic applications based on catecholate ligand-sensitized TiO2 NPs.

Solid state reactions are slow, because the diffusion of atoms or ions through reactant, interme-diate and crystalline product phases is the rate-limiting step. This requires days or even weeks of...

Selective oxidation of thioethers is an important reaction to obtain sulfoxides as synthetic intermediates for applications in chemical industry, medicinal chemistry and biology or the destruction of warfare agents. The...

Mixed-valence tungsten bronzes AxWO3 (A = alkali metal, NH4+, etc.) are a series of com-pounds with adaptive structural and compositional features that make them a hot research topic in thermoelectrics,...

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