Exchange-coupled bimagnetic cobalt/iron oxide branched nanocrystal heterostructures.

A colloidal seeded-growth strategy, relying on time-programmed delivery of selected stabilizing surfactants, has been developed to synthesize bimagnetic hybrid nanocrystals (HNCs) that consist of a single-crystal tetrapod-shaped skeleton of ferrimagnetic (FiM) iron oxide functionalized with multiple polycrystalline spherical domains of ferromagnetic (FM) Co. Due to the direct bonding interfaces formed between the two materials at the relevant junction regions, the HNCs exhibit FiM-FM exchange coupling, which transcribes into a rich scenario of significantly modified properties (not otherwise achievable with any of the single components or with their physical mixtures), including higher saturation magnetization and coercitivity values, exchange biasing, and enhanced thermal stability due to induced extra anisotropy. The availability of these new types of HNCs suggests that development of appropriate synthetic tools for arranging distinct material domains in predetermined spatial arrangements could lead to ..

Topologically controlled growth of magnetic-metal-functionalized semiconductor oxide nanorods.

Colloidal semiconductor-magnetic hybrid nanocrystals with topologically controlled composition are fabricated by heterogeneous nucleation of spherical e-Co domains onto anatase TiO2 nanorods. The latter can be selectively decorated at either their tips or at multiple locations along their longitudinal sidewalls, forming lattice-matched heterointerfaces regardless of the metal deposition sites. The possibility of switching between either heterostructure growth modes arises from the facet-dependent chemical reactivity of the oxide seeds, which is governed mainly by selective adhesion of the surfactants rather than by small differences in misfit-induced interfacial strain at the relevant junction points

Динамика насаждений сосны крымской (Pinus pallasiana L. ) в горном Крыму

За период 1938 – 2000 гг. произошло "смещение" мест произрастания сосновых древостоев в более богатые и влажные условия. Увеличилась площадь насаждений сосны крымской. Площадь сосновых культур больше чем в 3 раза превысила площадь естественных лесов. Средний запас сосновых лесов составляет 136 м³/га. Древостои ІІ и высших классов бонитета занимают лишь 12 % сосновых лесов.За період 1938 – 2000 рр. відбувся "зсув" місць виростання соснових деревостанів у багатші й вологіші умови. Збільшилася площа насаджень сосни кримської. Площа соснових культур у понад 3 рази перевершила площу природних лісів. Середній запас соснових лісів становить 136 м³/га. Деревостани ІІ і вищих класів бонітету займають лише 12 % соснових лісів.For 1938 – 2000 "displacement" of pine stands to more rich and moist sites has occurred. Area of P. pallasiana has increased. Pine plantation area has exceeded area of natural pine forests more than 3 times. Mean stock of pine forests is 136 m³/ha. Stands of the ІІ and higher growth classes take only 12 % of pine forests

Advances in the chemical fabrication of complex multimaterial nanocrystals

A review. Recent achievements of nanochem. research in the fabrication of colloidal nanoheterostructures are reviewed through revisiting relevant papers and related patents. Attention is focused on newly conceived generations of hybrid nanocrystals (HNCs) with a topol. controlled compn., in which size and shape tailored domains of different inorg. materials are permanently assembled together in a single multifunctional particle. Strategies for accessing HNCs in various configurations, such as core/shell systems, hetero-oligomers based on nearly spherical portions, and highly asym. nanostructures comprising joint sections with different shapes, are discussed. The chem.-phys. properties and technol. advantages offered by such complex nanocrystals are also highlighted

Dataset supporting the University of Southampton Doctoral Thesis 'Developing nanocomposite materials for catalytic applications'

This dataset supports the University of Southampton PhD thesis &#39;Developing Nanocomposite Materials for Catalytic Applications&#39; and contains data supporting figures in the main text. The files are organised in three zipped folders: Chapter_3.zip, Chapter_4.zip Chapter_5.zip The files in a .opju file format, to be opened in Origin software. The images are in .tif and .png formats. </span

Fabrication of Fischer-Tropsch Catalysts by Deposition of Iron Nanocrystals on Carbon Nanotubes

The fabrication of supported catalysts consisting of colloidal iron oxide nanocrystals with tunable size, geometry, and loadinghomogeneously dispersed on carbon nanotube (CNT) supportsis described herein. The catalyst synthesis is performed in a two-step approach. First, colloidal iron and iron oxide nanocrystals with a narrow size distribution are produced. Second, the nanocrystals are attached to CNT grains serving as support structure. Important features, like iron loading and nanocrystal density on the CNT support, are controlled by changing the nanocrystal concentration and ligand concentration, respectively. The Fischer-Tropsch performance reveals these new materials to be active, selective toward lower olefins (60% C of hydrocarbons produced in the absence of promoters), and remarkably stable against particle growth

Exchange-Coupled Bimagnetic Cobalt/Iron Oxide Branched Nanocrystal Heterostructures

A colloidal seeded-growth strategy, relying on time-programmed delivery of selected stabilizing surfactants, has been developed to synthesize bimagnetic hybrid nanocrystals (HNCs) that consist of a single-crystal tetrapod-shaped skeleton of ferrimagnetic (FiM) iron oxide functionalized with multiple polycrystalline spherical domains of ferromagnetic (FM) Co. Due to the direct bonding interfaces formed between the two materials at the relevant junction regions, the HNCs exhibit FiM-FM exchange coupling, which transcribes into a rich scenario of significantly modified properties (not otherwise achievable with any of the single components or with their physical mixtures), including higher saturation magnetization and coercitivity values, exchange biasing, and enhanced thermal stability due to induced extra anisotropy. The availability of these new types of HNCs suggests that development of appropriate synthetic tools for arranging distinct material domains in predetermined spatial arrangements could lead to a more rational design of nanoheterostructures potentially exploitable as active elements in future generations of magnetic recording devices

Anisotropic Cation Exchange in PbSe/CdSe Core/Shell Nanocrystals of Different Geometry

We present a study of Cd²⁺-for-Pb²⁺ exchange in PbSe nanocrystals (NCs) with cube, star, and rod shapes. Prolonged temperature-activated cation exchange results in PbSe/CdSe heterostructured nanocrystals (HNCs) that preserve their specific overall shape, whereas the PbSe core is strongly faceted with dominance of {111} facets. Hence, cation exchange proceeds while the Se anion lattice is preserved, and well-defined {111}/{111} PbSe/CdSe interfaces develop. Interestingly, by quenching the reaction at different stages of the cation exchange new structures have been isolated, such as core–shell nanorods, CdSe rods that contain one or two separated PbSe dots and fully zinc blende CdSe nanorods. The crystallographically anisotropic cation exchange has been characterized by a combined HRTEM/HAADF-STEM study of heterointerface evolution over reaction time and temperature. Strikingly, Pb and Cd are only intermixed at the PbSe/CdSe interface. We propose a plausible model for the cation exchange based on a layer-by-layer replacement of Pb²⁺ by Cd²⁺ enabled by a vacancy-assisted cation migration mechanism