Surface Chemistry Directs the Tunable Assembly of TiO 2 Anatase Nanocubes into Three‐Dimensional Mesocrystals

High-Performance TiO2 Nanoparticle/DOPA-Polymer Composites

Many natural materials are complex composites whose mechanical properties are often outstanding considering the weak constituents from which they are assembled. Nacre, made of inorganic (CaCO 3 ) and organic constituents, is a textbook example because of its strength and toughness, which are related to its hierarchical structure and its well-defi ned organic–inorganic interface. Emulating the construction principles of nacre using simple inorganic materials and polymers is essential for understanding how chemical composition and structure determine biomaterial functions. A hard multilayered nanocomposite is assembled based on alternating layers of TiO 2 nanoparticles and a 3-hydroxytyramine…

Thermoelectric properties of Zn-doped Ca_(3)AlSb_(3)

Polycrystalline samples of Ca_(3)Al_(1)−_(x)Zn_(x)Sb_(3), with x = 0.00, 0.01, 0.02, and 0.05 were synthesized via a combined ball milling and hot pressing technique and the influence of zinc as a dopant on the thermoelectric properties was studied and compared to the previously reported transport properties of sodium-doped Ca_(3)AlSb_(3). Consistent with the transport in the sodium-doped material, substitution of aluminum with zinc leads to p-type carrier conduction that can be sufficiently explained with a single parabolic band model. It is found that, while exhibiting higher carrier mobilities, the doping effectiveness of zinc is lower than that of sodium and the optimum carrier concentr…

Gram-scale selective synthesis of WO3−x nanorods and (NH4)xWO3 ammonium tungsten bronzes with tunable plasmonic properties

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 a selective synthesis of the tungsten oxides WO3-x and (NH4)xWO3 with tunable plasmonic properties. We selectively synthesized WO3-x nanorods with different aspect ratios and hexagonal tungsten bronzes (NH4)xWO3 as truncated nanocubes starting from ammonium metatungstate (NH4)6H2W12O40·xH2O. Both particles form from the same nuclei at temperatures >200 °C; monomer concentration and surfactant ratio are essential variables for phase selection. (NH4)xWO3 was the prefe…

Joining Two Natural Motifs: Catechol-Containing Poly(phosphoester)s.

Numerous catechol-containing polymers, including biodegradable polymers, are currently heavily discussed for modern biomaterials. However, there is no report combining poly(phosphoester)s (PPEs) with catechols. Adhesive PPEs have been prepared via acyclic diene metathesis polymerization. A novel acetal-protected catechol phosphate monomer was homo- and copolymerized with phosphoester comonomers with molecular weights up to 42000 g/mol. Quantitative release of the catechols was achieved by careful hydrolysis of the acetal groups without backbone degradation. Degradation of the PPEs under basic conditions revealed complete and statistical degradation of the phosphotri- to phosphodiesters. In …

Elastic Modulus and Thermal Conductivity of Thiolene/TiO2 Nanocomposites

Metal oxide based polymer nanocomposites find diverse applications as functional materials, and in particular thiol-ene/TiO2 nanocomposites are promising candidates for dental restorative materials. The important mechanical and thermal properties of the nanocomposites, however, are still not well understood. In this study, the elastic modulus and thermal conductivity of thiol-ene/TiO2 nanocomposite thin films with varying weight fractions of TiO2 nanoparticles are investigated by using Brillouin light scattering spectroscopy and 3ω measurements, respectively. As the TiO2 weight fraction increases from 0 to 90%, the effective elastic longitudinal modulus of the films increases from 6.2 to 37…

INFLUENCE OF THE CHEMICAL POTENTIAL ON THE CARRIER EFFECTIVE MASS IN THE THERMOELECTRIC SOLID SOLUTION Cu2Zn1-xFexGeSe4

In this paper, we describe the synthesis and characterization of the solid solution Cu 2 Zn 1-x Fe x GeSe 4. Electronic transport data have been analyzed using a single parabolic band model and have been compared to Cu 2+x Zn 1-x GeSe 4. The effective mass of these undoped, intrinsically hole conducting materials increases linearly with increasing carrier concentration, showing a non-parabolic transport behavior within the valence band.

TiO2 Nanoparticles Functionalized with Non-innocent Ligands Allow Oxidative Photocyanation of Amines with Visible/Near-Infrared Photons

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 TiO2 with a 2-methylisoquinolinium chromophore, which captures essential features of the extended π-system of 2,7-diazapyrenium (DAP2+) dications or graphitic carbon nitride. Two phenolic hydroxy groups make this ligand highly redox-active and allow for efficient surface binding and enhanced electron transfer to the TiO2 surface. Non-innocent ligands have energetically accessible levels that allow redox reactions to chang…

Mixed Ligand Shell Formation upon Catechol Ligand Adsorption on Hydrophobic TiO2 Nanoparticles

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. T...

Thermoelectric properties of Sr_3GaSb_3 – a chain-forming Zintl compound

Inspired by the promising thermoelectric properties in the Zintl compounds Ca_3AlSb_3 and Ca_5Al_2Sb_6, we investigate here the closely related compound Sr_3GaSb_3. Although the crystal structure of Sr_3GaSb_3 contains infinite chains of corner-linked tetrahedra, in common with Ca_3AlSb_3 and Ca_5Al_2Sb_6, it has twice as many atoms per unit cell (N = 56). This contributes to the exceptionally low lattice thermal conductivity (κ_L = 0.45 W m^(−1) K^(−1) at 1000 K) observed in Sr_3GaSb_3 samples synthesized for this study by ball milling followed by hot pressing. High temperature transport measurements reveal that Sr_3GaSb_3 is a nondegenerate semiconductor (consistent with Zintl charge-coun…