Teyeb Ould-Ely

Large-scale engineered synthesis of BaTiO3 nanoparticles using low-temperature bioinspired principles

We report here a robust, large-scale synthesis of BaTiO3 nanopowders using a bioinspired process that first was developed on a much smaller scale. The most advantageous points of this protocol are that it takes place at nearly room temperature (25 °C), overcomes many limitations encountered in other scale-up processes (such as the need for external drivers, e.g., heat, radiation or pressure), bypasses the use of surfactants and templates and does not necessitate pH adjustment. The use of a single-source, bimetallic alkoxide with the vapor diffusion of a hydrolytic catalyst (H2O) provides the necessary conditions for facile crystallization and growth of small, well-defined BaTiO3 nanoparticles at mild temperatures, yielding batches of up to 250 ± 5 g in a green process. Extension of this method to kilogram-scale production of BaTiO3 nanocrystals in semicontinuous and continuous processes is feasible.

Bio-inspired synthesis and laser processing of nanostructured barium titanate thin films: implications for uncooled IR sensor development

The Army requires passive uncooled IR sensors for use in numerous vehicle and weapons platforms, including driver vision enhancement (DVE), rifle sights, seeker munitions, and unattended ground sensors (UGSs) and unattended aerial vehicles (UAVs). Recent advances in bio-inspired/biomimetic nanomaterials synthesis, laser material processing, and sensor design and performance testing, offer the opportunity to create uncooled IR detector focal-plane arrays with improved sensitivity, low thermal mass, and fast response times, along with amenability to low-cost, rapid prototype manufacture. We are exploring the use of genotype-inspired, digitally-scripted laser direct-write techniques, in conjunction with the kinetically controlled catalytic process for the growth of nanostructured multimetallic perovskites, to develop a novel approach to the fabrication of precision patterned 2-D focal-plane arrays of pyroelectric perovskite-based materials. The bio-inspired growth of nanostructured, multimetallic perovskite thin-films corresponds to the use of kinetically controlled vapor diffusion for the slow growth of pure, highly crystalline 6-nm barium titanate (BaTiO3) nanoparticles. This unique vapor-diffusion sol-gel route enables the formation of stoichiometric cubic-phase nanoparticles at room temperature and ambient pressure in the absence of a structure-directing template. Novel laser direct-write processing and synchronized electro-optic pulse modulation techniques have been utilized to induce site-selective, patterned phase transformation of microscale aggregates of the BaTiO3 nanoparticles from the non-pyroelectric cubic polymorph to the pyroelectric tetragonal polymorph. This paper reports on our initial collaborative investigations, including comprehensive structural characterization (XRD, TEM, and SEM) of the BaTiO3 nanoparticles and thin-films, along with preliminary laser-induced phase transformation results.

Addition of thianthrene cation radical to non-conjugated dienes—Part II: Addition to two double bonds

Reaction of thianthrene cation radical tetrafluoroborate with 1,5-hexadiene, 1,7-octadiene, 1,8-nonadiene and 1,9-decadiene in the molar ratio 4:1 caused addition to occur to one and both of each diene’s double bonds. A mixture of four adducts was thus obtained, namely a bisadduct (12a–d), a monoadduct (13a–d), a di(bis)adduct (14a–d) and a di(mono)adduct (15a–d). The di(mono)adducts (15b–d) were isolated and characterized with 1H and 13C NMR spectroscopy. Under the same condition of excess of cation radical, addition occurred to only one double bond of 1,4-cyclohexadiene and 1,5-cyclooctadiene. Addition to both double bonds was not observed. The bisadduct (16) of 1,4-cyclohexadiene was characterized with 1H and 13C NMR spectroscopy and X-ray crystallography. On activated alumina, 15b–d underwent fast opening of dicationic rings to form mixtures of (E, E) – (17b–d) and (E, Z)-di(5-thianthreniumyl)diene (18b–d) in which the (E, E)-isomer was dominant and was characterized with 1H and 13C NMR spectroscopy.