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.

Structural characterization, solution stability, and potential health and environmental effects of the Nano-TiO2 bioencapsulation matrix and the model product of its biodegradation TiBALDH

Abstract: Dispersions of small TiO2 nanoparticles in alcohol, stabilized by surface complexation with protonated triethanolamine ligands, are proposed as bio-encapsulation matrices. They were characterized by TEM and EXAFS spectroscopy, and DLS was used to investigate the nanoparticles stability over time in their pure form and after insertion into aqueous medium. This study reveals unusual structural features that explain the recently demonstrated facile formation of dense encapsulates on the surface of biological objects. In the view of the potentially broad application of this already industrially available material in agriculture as an encapsulation matrix for biocontrol organisms, its potential health and environmental effects were characterized by employing a number of model systems. The potential health effects of the produced stable aqueous dispersions were studied in vitro using A549 and U1810 lung carcinoma cell lines. The nanotitania in the environment is partly bio-digested with the formation of citrate and lactate complexes. The effects on the growth of tobacco pollen grains by the nanotitania and of the ammonium lactato-oxo-titanate (TiBALDH, a product already broadly used in biomineralization studies) were investigated to gain insight into the impact of these materials on the environment and specifically on plant reproduction. TiBALDH was used as a model product of the bio-digestion and its structure has been probed in this work by X-ray powder diffraction and EXAFS spectroscopy. No acute negative bio-effects could be observed for the studied materials at significantly high concentrations, such as 50 μg ml−1 for the viability of human lung cancer cells and up to about 120 μg ml−1 for the growth of pollen grains, corresponding to the conditions of proposed field applications. This observation was contrasted by the apparently high toxicity of the LaAlO3 based nanophosphor which was applied as a positive control.

Alkoxide Route to Mixed Oxides of Rhenium, Niobium, and Tantalum. Preparation and X-ray Single-Crystal Study of a Novel Rhenium−Niobium Methoxo Complex, Nb2(OMe)8(ReO4)2

Abstract: Thermal decomposition of complex oxomethoxo compounds Nb4O2(OMe)14(ReO4)2 (I) and Ta4O2(OMe)14(ReO4)2 (II) has been investigated. The decomposition of (II) at temperatures exceeding 100 °C results in the formation of MeOMe, MeOCH2OMe, MeOH, and H2O vapor and is accompanied by sublimation at temperatures over 135 °C. Plausible mechanisms of the processes studied are discussed. A new bimetallic methoxo compound, Nb2(OMe)8(ReO4)2 (III), was synthesized by interaction between Re2O7 and Nb2(OMe)10 in toluene solution and its structure was determined by means of an X-ray single-crystal study. The structure can be considered as a product of substitution for terminal methoxo groups with two perrhenate groups in dimeric Nb2(OMe)10 molecules. Decomposition of II in an inert atmosphere at 900 °C gave a Re−Ta mixed oxide phase, supposedly based on the L-Ta2O5 structure. Decomposition of I and III under similar conditions leads to the formation of rhenium−niobium oxide phases. The results obtained provide a basis for ...

Anodic oxidation of molybdenum and tungsten in alcohols: isolation and X-ray single-crystal study of side products

Abstract: The study of the side products of the anodic dissolution of molybdenum and tungsten metals in alcohols in the presence of LiCl showed them to be [LiMo2O2(OMe)7(MeOH)] 1 in the case of MeOH and [LiMo2O4(OEt)5(EtOH)] 2 in EtOH. Treatment of 2 with an excess of PriOH gave [LiMo2O4(OPri)5(PriOH)] 3, the structure of which was confirmed by a study of [{LiMo2O4(OPri)4(OC2H4OMe)}2] 4, the product of partial substitution of OR groups in 3 by 2-methoxyethoxide ligands. Reaction of 2 with an excess of MeOC2H4OH led to an equimolar mixture of [MoO2(OC2H4OMe)2] and [LiMoO2(OC2H4OMe)3] 5. In PriOH a crystalline product identified as [Mo6O10(OPri)12] 6 was isolated. Anodic oxidation of tungsten in MeOH gave a mixture of homometallic W(OMe)6 and [WO(OMe)4]. Electrosynthesis in EtOH gave as major product an amorphous glass-like mass {after separation of crystalline [WO(OEt)4] by filtration and subsequent drying of the filtrate in vacuo}. Treatment of the latter with an excess of HOC2H4OMe led to crystallization of [{LiWO2(OC2H4OMe)3}2· 2Li(HOC2H4OMe)2]2+[W6O19]2– 7. Complexes 1, 4 and 7 were characterized by X-ray single-crystal studies. A GLC-mass spectrometric study of the composition of organic side products indicated that the processes were associated with formation of ethers, alkyl halides, aldehydes or ketones and their derivatives. The nature of the possible side reactions was deduced on the basis of the data obtained.

In Situ Activation of an Indium(III) Triazenide Precursor for Epitaxial Growth of Indium Nitride by Atomic Layer Deposition

Abstract: Indium nitride (InN) is characterized by its high electron mobility making it a ground-breaking material for high frequency electronics. The difficulty of depositing high-quality crystalline InN cu...

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