Vadim G. Kessler

Bio: Vadim G. Kessler is an academic researcher from Swedish University of Agricultural Sciences. The author has contributed to research in topics: Alkoxide & Nanoparticle. The author has an hindex of 39, co-authored 284 publications receiving 5262 citations. Previous affiliations of Vadim G. Kessler include Bar-Ilan University & Center for Advanced Materials.

Phase Control in Hafnia: New Synthesis Approach and Convergence of Average and Local Structure Properties.

Abstract: Technologically relevant tetragonal/cubic phases of HfO2 can be stabilized at room temperature by doping with trivalent rare earths using various approaches denoted generically as bulk coprecipitation. Using in situ/ex situ X-ray diffraction (XRD), Raman spectroscopy, high-resolution transmission electron microscopy, and in situ/ex situ site-selective, time-gated luminescence spectroscopy, we show that wet impregnation of hafnia nanoparticles with 10% Eu oxide followed by mild calcination in air at 500 °C produces an efficient stabilization of the cubic phase, comparable to that obtained by bulk precipitation. The physical reasons behind the apparently conflictual data concerning the actual crystallographic phase and the local symmetry around the Eu stabilizer and how these can be mediated by luminescence analysis are also discussed. Apparently, the cubic crystal structure symmetry determined by XRD results in a pseudocubic/tetragonal local structure around Eu determined by luminescence. Considering the recent findings on wet impregnated CeO2 and ZrO2, it is concluded that CeO2, ZrO2, and HfO2 represent a unique case of a family of oxides that is extremely tolerant to heavy doping by wet impregnation. In this way, the same batch of preformed nanoparticles can be doped with different lanthanide concentrations or with various lanthanides at a fixed concentration, allowing a systematic and reliable investigation of the effect of doping, lanthanide type, and lanthanide concentration on the various functionalities of these technologically relevant oxides.

Oxoethoxide Chlorides – Representatives of Oligonuclear Alkoxide Complexes of Gallium: Penta- and Dodecanuclear Molecules

Abstract: Metathesis of solid GaCl 3 with NaOEt/EtOH (1:3) provided, after separation of the NaCl precipitate, a solution containing oxoalkoxide chloride complexes of gallium. Residues from evacuation of the latter were redissolved in either toluene/ MeCN (solution 1) or toluene/pyridine (solution 2). Storage of the first solution provided crystals of Ga 5 (μ 5 -O)(μ-OEt) 8 Cl 5 (1), and of the second solution - [Ga 12 (μ 4 -O)2(μ 3 -O) 5 (μ-OEt) 10 -Cl 12 Py 4 ]Py (2), both at room temperature and in relatively high yields. Compound 1 crystallizes as a vertically contracted tetragonal pyramid with the μ 5 -O ligand situated in the center of the equatorial plane defined by four trigonal bipyramidal coordinated gallium atoms. The axial Ga atom has octahedral coordination. All eight edges of the pyramid are capped by μ-OEt groups, and all the chloride ligands are situated in terminal positions. Crystals of [Ga 12 (μ 4 -O) 2 (μ 3 -O) 5 (μ-OEt) 10 Cl 12 Py 4 ]Py (2) contain two [Ga 5 (μ 4 -O) (μ 3 -O) 2 (μ-OEt) 5 -Cl 5 Py] fragments connected through a cyclic [Ga 4 (μ 3 -O) 5 -Cl 2 Py 2 ) unit with a μ 3 -O ligand in its center. Of the metal atoms, three possess tetrahedral, seven trigonal bipyramidal, and two octahedral coordination. The mass spectrum of 1 contains penta- and tetranuclear fragments. The spectrum of 2 contains heptameric fragments in addition to the pentanuclear fragments that are analogous to those in the spectrum of 1. The factors leading to formation of polymeric M(OR) n and related oligonuclear oxocomplexes are discussed.

Solution interaction of O-donor ligand metal complexes with thiocarbonyl compounds—a new general route to metal sulfide materials

Abstract: Molybdenum and tungsten oxoalkoxides {[MO(OMe)4]; M = Mo, W} and rhenium heptaoxide (Re2O7) reacted at room temperature with thiocarbonyl compounds such as N,N-dimethylthioformamide (DMTF), producing the crystalline metal sulfides MoS2, WS3 and Re2S7, respectively. The reaction mechanism involves, as the first step, the coordination of DMTF to a metal via the sulfur donor atom, followed by the subsequent metathesis of the latter with the doubly bonded oxygen atom. The final product is, depending on reaction conditions, a colloidal metal sulfide or up to 0.1 mm large metal sulfide crystals. By carrying out the reaction within a mesoporous alumina matrix, supported metal sulfide catalysts were obtained in one step. These catalysts were tested for catalytic hydrodesulfurization and their activity compared with catalysts prepared by traditional methods. Reaction of nickel and zinc acetylacetonates and aminoalkoxides with DMTF in hydrocarbon media was found to provide colloids and, on aging, fine powder precipitates of NiS and ZnS.

Atomically Precise Colloidal Metal Nanoclusters and Nanoparticles: Fundamentals and Opportunities

Abstract: Colloidal nanoparticles are being intensely pursued in current nanoscience research. Nanochemists are often frustrated by the well-known fact that no two nanoparticles are the same, which precludes the deep understanding of many fundamental properties of colloidal nanoparticles in which the total structures (core plus surface) must be known. Therefore, controlling nanoparticles with atomic precision and solving their total structures have long been major dreams for nanochemists. Recently, these goals are partially fulfilled in the case of gold nanoparticles, at least in the ultrasmall size regime (1–3 nm in diameter, often called nanoclusters). This review summarizes the major progress in the field, including the principles that permit atomically precise synthesis, new types of atomic structures, and unique physical and chemical properties of atomically precise nanoparticles, as well as exciting opportunities for nanochemists to understand very fundamental science of colloidal nanoparticles (such as the s...

Controlled ring-opening polymerization of lactide and glycolide.

Abstract: 23 Stereocontrol of Lactide ROP 6164 231 Isotactic Polylactides 6164 232 Syndiotactic Polylactides 6166 233 Heterotactic Polylactides 6166 3 Anionic Polymerization 6166 4 Nucleophilic Polymerization 6168 41 Mechanistic Considerations 6168 42 Catalysts 6169 421 Enzymes 6169 422 Organocatalysts 6169 43 Stereocontrol of Lactide ROP 6170 44 Depolymerization 6170 5 Cationic Polymerization 6170 6 Conclusion and Perspectives 6171 7 Acknowledgments 6173 8 References and Notes 6173

Multiphoton Absorbing Materials : Molecular Designs, Characterizations, and Applications

Abstract: 4. Survey of Novel Multiphoton Active Materials 1257 4.1. Multiphoton Absorbing Systems 1257 4.2. Organic Molecules 1257 4.3. Organic Liquids and Liquid Crystals 1259 4.4. Conjugated Polymers 1259 4.4.1. Polydiacetylenes 1261 4.4.2. Polyphenylenevinylenes (PPVs) 1261 4.4.3. Polythiophenes 1263 4.4.4. Other Conjugated Polymers 1265 4.4.5. Dendrimers 1265 4.4.6. Hyperbranched Polymers 1267 4.5. Fullerenes 1267 4.6. Coordination and Organometallic Compounds 1271 4.6.1. Metal Dithiolenes 1271 4.6.2. Pyridine-Based Multidentate Ligands 1272 4.6.3. Other Transition-Metal Complexes 1273 4.6.4. Lanthanide Complexes 1275 4.6.5. Ferrocene Derivatives 1275 4.6.6. Alkynylruthenium Complexes 1279 4.6.7. Platinum Acetylides 1279 4.7. Porphyrins and Metallophophyrins 1279 4.8. Nanoparticles 1281 4.9. Biomolecules and Derivatives 1282 5. Nonlinear Optical Characterizations of Multiphoton Active Materials 1282

Functionalizing nanoparticles with biological molecules: developing chemistries that facilitate nanotechnology.

Abstract: Chemistries that Facilitate Nanotechnology Kim E. Sapsford,† W. Russ Algar, Lorenzo Berti, Kelly Boeneman Gemmill,‡ Brendan J. Casey,† Eunkeu Oh, Michael H. Stewart, and Igor L. Medintz*,‡ †Division of Biology, Department of Chemistry and Materials Science, Office of Science and Engineering Laboratories, U.S. Food and Drug Administration, Silver Spring, Maryland 20993, United States ‡Center for Bio/Molecular Science and Engineering Code 6900 and Division of Optical Sciences Code 5611, U.S. Naval Research Laboratory, Washington, D.C. 20375, United States College of Science, George Mason University, 4400 University Drive, Fairfax, Virginia 22030, United States Department of Biochemistry and Molecular Medicine, University of California, Davis, School of Medicine, Sacramento, California 95817, United States Sotera Defense Solutions, Crofton, Maryland 21114, United States