Charles M. Lukehart

Nanodiamond Nanofluids for Enhanced Thermal Conductivity

Deaggregation of oxidized ultradispersed diamond (UDD) in dimethylsulfoxide followed by reaction with glycidol monomer, purification via aqueous dialysis, and dispersion in ethylene glycol (EG) base fluid affords nanodiamond (ND)-poly(glycidol) polymer brush:EG nanofluids exhibiting 12% thermal conductivity enhancement at a ND loading of 0.9 vol %. Deaggregation of UDD in the presence of oleic acid/octane followed by dispersion in light mineral oil and evaporative removal of octane gives ND·oleic acid:mineral oil dispersions exhibiting 11% thermal conductivity enhancement at a ND loading of 1.9 vol %. Average particle sizes of ND additives, determined by dynamic light scattering, are, respectively, ca. 11 nm (in H2O) and 18 nm (in toluene). Observed thermal conductivity enhancements outperform enhancement effects calculated using Maxwells effective medium approximation by 2- to 4-fold. Covalent ND surface modification gives 2-fold greater thermal conductivity enhancement than ND surface modification via hydrogen-bonding interactions at similar concentrations. Stable, static ND:mineral oil dispersions are reported for the first time.

Special Issue: Applications of Green-Synthesized Nanoparticles in Pharmacology, Parasitology and Entomology

This Special Issue of Journal of Cluster Science contains the first two Commentary articles published in this journal along with a collection of 38 invited or contributed original papers reporting applications of green-synthesized nanoparticles to the fields of pharmacology, parasitology and entomology. Nanobiotechnologies have the potential to revolutionize a wide array of clinical and environmental applications, including drug delivery, diagnostics, imaging, sensing, gene delivery, artificial implants, tissue engineering, parasitology, and pest management. Nanoparticulate materials are of particular interest for many such applications due to their unusual optical, chemical and photo-electrochemical properties. Biofabrication (‘‘green’’ preparation methods) of nanoparticulate materials exploits microbial and botanical-based, single-step synthesis strategies that do not require high pressure, intensive energy consumption, elevated temperatures, or use of highly toxic chemicals more typical of chemical and physical methods. Although utilizing botanical extracts as chemical reagents in nanoparticle formation complicates identification of reactive species, in situ surface-passification usually occurs to give biocompatible nanoparticle dispersions ideally suitable for clinical, biological, or environmental testing. A Commentary (Benelli, Pavela, et al.) leads off this Special Issue on the topic of using plant products for nanoparticle syntheses relevant to pest control, an outcome closely related to human health. Because proper data analysis has general importance to quantifying effects of bionanoscience applications, the second Commentary (Benelli) provides readers with an overview of this relevant topic.

Reactions of coordinated molecules: XX. An unexpected route to the preparation of hydroxycarbenoid and formylrhenium(I) halide complexes

When BrMn(CO)5 and the rhenium complexes, XRe(CO)5 (where X is H, Cl, Br or I) are treated with one equivalent of methyllithium the correspondingcis-halo- or hydrido-acetylmetalate complexes, Li[cis-(OC)4(X)MC(O)CH3], are formed unexpectedly. The protonation of the halo-anions affords the hydroxy-carbenoid complexes. When the halopentacarbonylrhenium complexes are treated with Li[BEt3H] the corresponding formylmetalate complexes are formed. The reaction chemistry of these anions and of the analogous formyl- and acetyl-metalate anion is discussed briefly.

Capture and release of alkyne-derivatized glycerophospholipids using cobalt chemistry

Alkyne modified phospholipids can be unambiguously identified and differentiated from native species in complex mixtures by formation of dicobalthexacarbonyl complexes. This reaction is specific for alkynes and is unaffected by other glycerophospholipid related moieties. Enrichment of cells with alkyne-derivatized fatty acids or glycerophospholipids followed by solid phase sequestration and release is a promising new method for unequivocally monitoring individual glycerophospholipids following incorporation and facilitates lipidomic analysis of substrates and products.

Paramagnetic NMR Contrast Agents: Development and Evaluation

Paramagnetic ions could be theoretically used as NMR contrast agents because of their effect upon T1. However, the toxicity of these ions prevents their application. By the formation of appropriate chemical complexes with these ions, the toxicity of these agents can be substantially reduced while maintaining the paramagnetic effect. Two potential NMR contrast agents, one for oral use and one for intravenous administration, were developed and evaluated both in vitro and in vivo. The effect upon T1 in vitro of these paramagnetic compounds was determined using a JEOL FX-90Q NMR spectrometer. These agents were evaluated in vivo in dogs with a Technicare 0.3 tesla superconducting magnet system and in rabbits with the Aberdeen 0.04 tesla resistive NMR imager. Using calculated T1 NMR images, a nontoxic dose of gadolinium oxalate provided visualization of the gastrointestinal tract. Intravenous administration of chromium EDTA provided enhancement of the kidneys, ureters, and bladder, thereby potentially allowing for the evaluation of renal function with magnetic resonance imaging. Stable paramagnetic complexes can serve as effective, nontoxic, oral and intravenous NMR contrast agents.

ORGANOMETALLIC COMPOUNDS AS SINGLE-SOURCE PRECURSORS TO NANOCOMPOSITE MATERIALS : AN OVERVIEW

Abstract Molecularly doped silica xerogels are prepared by adding either main-group or transition metal organometallic compounds containing bifunctional ligands to conventional sol–gel formulations. These bifunctional ligands contain distal (alkoxy or hydroxy)silyl groups, so that the dopant molecules become covalently incorporated into the silica xerogel matrix as it is being formed. Subsequent thermal treatment under reducing or oxidizing-then-reducing conditions leads to the decomposition of molecular precursor and to the formation of a nanoparticulate material with precise stoichiometry highly dispersed throughout the xerogel matrix.

Work function reduction of graphitic nanofibers by potassium intercalation

Materials with low work functions hold great potential for improving the performance of thermionic energy converters and other thermionic emission devices. Thermionic electron energy distributions (TEEDs) of graphitic carbon nanofibers (GCNFs) with and without intercalated potassium are used to characterize performance under realistic operating conditions. TEEDs of intercalated GCNFs at temperatures of 600 and 700 °C reveal an effective work function of 2.2 eV, a reduction of 2.5 eV from the work function of the GCNF without intercalate. In addition, consistent with other published work, a narrowing of the electron energy spectrum’s width occurs with intercalation. This narrower energy distribution may indicate emission from hybridized carbon–potassium states.

Reactions of Coordinated Molecules : I. The oxidation of transition metal carbenoid complexes by iodosobenzene; a comparative study

Abstract The reaction of transition metal carbenoid complexes with oxidizing agents results in the oxidation of the carbenoid ligand forming the corresponding carboxylic acid derivative. A study of this reaction using pyridine- N -oxide, ceric ammonium nitrate and iodosobenzene as the oxidants reveals that the yield of the carboxylic acid derivative is affected significantly by the solvent medium. Oxidations using pyridine- N -oxide in tetrahydrofuran solution generally afford the organic acid derivatives in good to excellent yields. Iodosobenzene is a selective oxidant affording the greatest yield of ethylene carbonate and it is the first oxidant reported to oxidize an amino-carbenoid complex to the corresponding amide. This oxidation reaction represents a convenient and rapid chemical method for the characterization of carbenoid complexes.

Multifunctional FePt Nanoparticles for Radiation-Guided Targeting and Imaging of Cancer

A multifunctional FePt nanoparticle was developed that targets tumor microvasculature via “radiation-guided” peptides, and is detected by both near-infrared (NIR) fluorescence imaging and analytical mass spectrometry methods. Tumor specific binding was first measured by biotinylated peptide linked to fluorophore-conjugated streptavidin. This showed tumor selective binding to tumors using the HVGGSSV peptide. FePt nanoparticles were synthesized sequentially by surface modification with poly(l)lysine, poly(ethylene) glycol conjugation, and functionalized with HVGGSSV peptide and fluorescent probe Alexa fluor 750. NIR fluorescence imaging and ICP-MS analysis showed significant HVGGSSV-FePt nanoparticle binding to irradiated tumors as compared to unirradiated tumors and controls. Results indicate that multifunctional FePt nanoparticles have potential application for radiation-guided targeting and imaging of cancer.

Metalla-derivatives of β-diketones

Publisher Summary This chapter discusses metalla-β-diketones. The term “metalla-β-diketonate” refers to an anionic diacyl complex, such as LnM (RCO)(R’CO)¯, in which the two acyl ligands occupy adjacent coordination sites of the metal atom. Metalla-β-diketonate complexes are conveniently prepared by reacting acylmetal carbonyl complexes with strong bases that can also react as nucleophiles, such as organolithium, Grignard, or boron hydride reagents. These complexes are readily prepared by the protonation of metalla-β-diketonate anions. The X–ray structures of the boron bromide and boron chloride complexes confirm the tridentate coordination of the triacetylrhenato ligand to the boron atom. Both molecules have crystallographically imposed mirror symmetry. A large number of complexes have been prepared in which metalla-β-diketonate anions coordinate to either metal ions or B(X)(Y) moieties. The most interesting and unique reaction yet discovered for a metalla-β-diketonate molecule is the interligand C–C coupling of the two acyl carbon donor atoms. This very general reaction was discovered serendipitiously while attempting to explore the reaction chemistry of (ferra-β-diketonato) BF2 complexes. Because the acyl ligands in these compounds have hybrid acyl/carbene character, the methyl substituents of the ferra chelate ring should presumably be relatively acidic.