Solid-state Chemistry (solid-state + chemistry)

Distribution by Scientific Domains

Selected Abstracts

Solid-State Chemistry at an Isolated Copper(I) Center with O2,

Grégory Thiabaud
Solider Auftritt: Eine chemo- und regioselektive Oxygenierung mit O2 im Festkörper ergibt den CuI -Komplex des Vierelektronenoxidationsprodukts eines organischen Liganden (siehe Schema). Dabei vermittelt ein einzelnes CuI -Zentrum ohne Redox-Cofaktor die Übertragung einer geraden Zahl von Elektronen auf O2. Das Resultat bestätigt die Rolle von [CuO2]+ -Einheiten als reaktive Spezies in der C-H-Bindungsspaltung. [source]

A Facile Route to Synthesize the Ti5NbO14 Nanosheets by Mechanical Cleavage Process

Na Zhang
Layered and rod-like K3Ti5NbO14 was synthesized via the solid-state chemistry, and it was exfoliated into nanosheets through a novel mechanical cleavage technology. X-ray diffraction was utilized to determine the phase changes of all the specimen during the total process, and the microstructure of the samples was analyzed by scanning electron microscope and transmission electron microscope. The formation mechanism was also discussed in detail, the results indicated that the compression and shearing should play a main function in the crack and the cleavage of the aggregated layered compound. UV,vis absorption spectroscopy was used to monitor the consecutive buildup of the (PEI/Ti5NbO14)n film. The resulting quasi-linear increase at the top absorbance as a function of the sequential assembly number for the multilayer film indicated that the nanosheet had deposited uniformly in each dipping cycle. The photocatalytic activity of K3Ti5NbO14 -related products was examined. Compared with original layered compound, nanosheet precipitate had good property under irradiation of ultraviolet light. [source]

Addressing chemical diversity by employing the energy landscape concept

Martin Jansen
Exploring the structural diversity of a chemical system rests on three pillars. First, there is the global exploration of its energy landscape that allows one to predict which crystalline modifications can exist in a chemical system at a given temperature and pressure. Next, there is the development of new synthesis methods in solid-state chemistry, which require only very low activation energies such that even metastable modifications corresponding, for example, to minima on the landscape surrounded by low barriers can be realized. Finally, there is the theoretical design of optimal synthesis routes, again based on the study of the system's energy landscape. In this paper the energy landscape approach to the prediction of stable and metastable compounds as a function of temperature and pressure is presented, with a particular focus on possible phase transitions. Furthermore, several examples are presented, where such predicted compounds were subsequently successfully synthesized, often employing a newly developed synthesis method, low-temperature atom-beam deposition. [source]

Solid,Solid Phase Transitions: Interface Controlled Reactivity and Formation of Intermediate Structures

Stefano Leoni Dr.
Abstract Finding new pathways to novel materials is an open challenge in modern solid-state chemistry. Among the reasons that still prevent a rational planning of synthetic routes is the lack of an atomistic understanding at the moment of phase formation. Metastable phases are, in this respect, powerful points of access to new materials. For the synthetic efforts to fully take advantage of such peculiar intermediates, a precise atomistic understanding of critical processes in the solid state in its many facets, that is, nucleation patterns, formation and propagation of interfaces, intermediate structures, and phase growth, is mandatory. Recently we have started a systematic theoretical study of phase transitions, especially of processes with first-order thermodynamics, to reach a firm understanding of the atomistic mechanisms governing polymorphism in the solid state. A clear picture is emerging of the interplay between nucleation patterns, the evolution of domain interfaces and final material morphology. Therein intermediate metastable structural motifs with distinct atomic patterns are identified, which become exciting targets for chemical synthesis. Accordingly, a new way of implementing simulation strategies as a powerful support to the chemical intuition is emerging. Simulations of real materials under conditions corresponding to the experiments are shedding light onto yet elusive aspects of solid,solid transformations. Particularly, sharp insights into local nucleation and growth events allow the formulation of new concepts for rationalizing interfaces formed during phase nucleation and growth. Structurally different and confined in space, metastable interfaces occurring during polymorph transformations bring about distinct diffusion behavior of the chemical species involved. More generally, stable structures emerge as a result of the concurrence of the transformation mechanism and of chemical reactions within the phase-growth fronts. [source]