Silica nanosprings (NSs) consisting of multiple nanowires intertwined were demonstrated to reversibly store 0.85 wt% hydrogen at 20 bar and room temperature. X-ray photoelectron spectroscopy indicates a mixed 3+–4+ ionization state of the silicon atoms and partially explains the enhanced surface adsorption of H2 relative to other forms of silica. Theoretical modeling and simulation using a Lennard-Jones potential demonstrated that interstitial sites between the silica nanowires forming the NS are energetically more favorable adsorption sites relative to single nanowires. The addition of Pd nanoparticles to the surface of the silica NSs was demonstrated to increase the hydrogen storage capacity to ≈3.5 wt% at 66 bar and room temperature. Palladium-nanoparticle-induced hydrogen spillover is attributed to the enhanced storage capacity relative to bare silica NSs.

Chemiresistors (conductometric sensor) were fabricated on the basis of novel nanomaterials--silica nanosprings ALD coated with ZnO. The effects of high temperature and UV illumination on the electronic and gas sensing properties of chemiresistors are reported. For the thermally activated chemiresistors, a discrimination mechanism was developed and an integrated sensor-array for simultaneous real-time resistance scans was built. The integrated sensor response was tested using linear discriminant analysis (LDA). The distinguished electronic signatures of various chemical vapors were obtained at ppm level. It was found that the recovery rate at high temperature drastically increases upon UV illumination. The feasibility study of the activation method by UV illumination at room temperature was conducted.

Chemiresistors were constructed using 3-D silica nanospring mats coated with a contiguous film of ZnO nanocrystals. Chemiresistors with an average ZnO nanocrystal radius <3 nm, or >20 nm, were found to exhibit a relative change in conductance of a factor of 50 upon exposure to a gas flow of 20% O2 and 80% N2 with ∼500 ppm of toluene and an operational temperature of 400 °C. Samples with an average ZnO nanocrystal radius of 15 nm were found to be the most responsive with a relative conductance change of a factor of 1000. The addition of metal nanoparticles (average radius equal to 2.4 nm) onto the surface of the ZnO nanocrystals (average radius equal to 15 nm) produced a relative change in conductance of a factor of 1500. For the optimum conditions (T = 400 °C, grain size ∼15 nm) well-defined spikes in conductance to explosive vapors (TNT, TATP) were obtained for 0.1 ms exposure time at ppb levels.

Chemical sensors were fabricated on the basis of novel nanomaterials – silica nanosprings. High chemical sensitivity was achieved by coating the silica nanosprings with ZnO using atomic layer deposition (ALD), followed by decorating with metal nanoparticles. The optimum operational conditions (T=400°C, ZnO grain size ∼15nm) were obtained and investigated. The nanospring-based sensors demonstrated remarkable vapor sensing properties: well-defined spikes in conductance upon exposure to explosives (TNT, TATP) and flammable vapors (toluene, acetone, ethanol) were obtained for 0.1ms exposure times at ppb level. Based on surface doping of ZnO with various metallic nanoparticles, a discrimination mechanism was developed and an integrated sensor-array for simultaneous real-time resistance scans was built. The integrated sensor response was tested using linear discriminant analysis (LDA). The distinguished electronic signatures of various chemical vapors were obtained at ppm level.

An enzyme-based continuous flow reactor (CFR) was constructed with silica Nanosprings (TM) and beta-galactosidase from Aspergillus oryzae. Preliminary results with the model substrate o-nitrophenyL-beta-galactoside show the reactor to be functional, converting 71% of the substrate to product at a flow rate of 0.1ml/min.

Several approaches to stabilize and reduce atmospheric CO2 concentrations have been tested. While carbon capture and storage (CCS) has been hailed as the most promising approach for sequestering CO2 safely away from the atmosphere, the technology remains unproven, costly, and will likely not be commercially available for decades. An alternative to CCS is to consider CO2 as a commodity that can be converted or more specifically recycled into useful and valuable chemicals and/or clean burning fuels. This approach not only reduces or eliminates the amount of CO2 entering the atmosphere, but it creates a revenue stream to offset the cost of implementation. GoNano Technologies, Inc. has demonstrated a nanostructured titanium dioxide (T iO2) photocatalyst that can be used to selectively convert CO2 into methane, methanol, formic acid, and/or formaldehyde.

Air pollution generated from automobile emissions is an area of general concern because of the environmental impact associated with such emissions and the growth in the world vehicle fleet. Significant developments in automotive catalytic converters has occurred with three-way catalysts (TWC). However, major challenges remain, particularly because of regulatory demands for better and better performance. The approach proposed here is to engineer the cell walls of a catalytic converter monolith using Nanospringtechnology. The Nanosprings are bonded directly to the cordierite surface without the use of binders and can be coated with a wide range of metal oxides and metal nanoparticles. Due to the use of Nanosprings a significantly higher fraction of the metal nanoparticle surface is accessible to exhaust gases, thus deceasing the overall amount of precious metal required.

The use of silicon dioxide (SiO 2 ) nanosprings as supports for immobilized enzymes in a continuous microreactor is described. A nanospring mat (2.2 cm 2 × 60 μm thick) was functionalized with γ‐aminopropyltriethoxysilane, then treated with N ‐succinimidyl‐3‐(2‐pyridyldithio)‐propionate (SPDP) and dithiothreitol (DTT) to produce surface thiol (SH) groups. SPDP‐modified β‐galactosidase from Aspergillus oryzae was immobilized on the thiolated nanosprings by reversible disulfide linkages. The enzyme‐coated nanospring mat was placed into a 175‐μm high microchannel, with the mat partially occluding the channel. The kinetics and steady‐state conversion of hydrolysis of o‐ nitrophenyl β‐ D ‐galactosylpyranoside at various substrate flow rates and concentrations were measured. Substantial flow was observed through the nanosprings, for which the Darcy permeability κ ≈ 3 × 10 −6 cm 2 . A simple, one‐parameter numerical model coupling Navier‐Stokes and Darcy flow with a pseudo‐first‐order reaction was used to fit the experimental data. Simulated reactor performance was sensitive to changes in κ and the height of the nanospring mat. Permeabilities lower than 10 −8 cm 2 practically eliminated convective flow through the nanosprings, and substantially decreased conversion. Increasing the height of the mat increased conversion in simulations, but requires more enzymes and could cause sealing issues if grown above channel walls. Preliminary results indicate that in situ regeneration by reduction with DTT and incubation with SPDP‐modified β‐galactosidase is possible. Nanosprings provide high solvent‐accessible surface area with good permeability and mechanical stability, can be patterned into existing microdevices, and are amenable to immobilization of biomolecules. Nanosprings offer a novel and useful support for enzymatic microreactors, biosensors, and lab‐on‐chip devices. © 2010 American Institute of Chemical Engineers Biotechnol. Prog., 2010

In this study, the initial phase of development of a vertically aligned (silica) nanospring (VANS)-based sensor utilizing alternating current impedance spectroscopy is presented. The sensor is a capacitor consisting of two glass substrates coated with indium tin oxide, where the VANS are grown on one substrate, following a top-down approach, serving as the dielectric spacer layer. The sensitivity of the VANS sensors was evaluated using deionized water (of an effective similar or equal to 10(-3) mM monovalent ion concentration) and saline-phosphate (SP) solutions of pH 7.3 with concentrations 0.1, 1, 10 and 100 mM. Similar tests were performed with sensors without VANS or blank sensors. The modeling of the VANS impedance spectra required an equivalent circuit consisting of eight elements compared to four elements for the blank sensor. VANS sensors exhibited greater sensitivity to changes in the SP concentration relative to the blank sensors. The enhanced sensitivity is attributed to the addition of an ionic diffusion barrier at the VANS-solution interface and to ionic diffusion within the VANS.

Catalysts are central to energy conversion and play a key role in chemical synthesis and processes for the hydrogen economy. Since catalytic performance is a limiting factor for many essential elements of the hydrogen economy (including fuel cell efficiency, storage kinetics, and production capacity), the need for improved catalysts is great. One-dimensional (ID) nanomaterials are ideal for catalyst applications because of their large surface area to volume ratio, which results in orders of magnitude more reactive sites than thin films or bulk materials. They are often reusable and in some cases are more environmentally friendly than traditional catalyst materials. The ability to engineer the surface of I D nanomaterials allows catalysts to be created that have, in addition to enhanced kinetics, specificity for certain reactions. The process used to produce a range of surface engineered nanostructured catalysts is described and the resultant microstructures are related to specific reactions that can be enhanced.

Silica nanowires are one-dimensional nanomaterials that are being developed for use in biological systems. Unfortunately, little is known regarding the cytotoxic potential of this type of nanomaterial. Here, using two different human epithelial cell lines we have examined the cytotoxicity of silica nanowires over a broad concentration range. The results indicate that silica nanowires are nontoxic at concentrations below 190 mg/ml but exhibit considerable cytotoxicity at higher concentrations. Examination of the mechanisms responsible for nanowire-induced cytotoxicity indicates that apoptotic pathways are not activated. Instead, cytotoxicity appears to be primarily due to increased necrosis in cells exposed to high concentrations of nanowires. In contrast to what was seen with silica nanowires, analysis of silica nanoparticles revealed very little cytotoxicity even at the highest concentrations tested. These results indicate that structural differences between silica nanomaterials can have dramatic effects on interaction of these nanomaterials with cells.

In the structure of the title compound, C 27 H 21 P, at 89 (2) K the P atom is bound to the allylic carbon of the indenyl unit with P—C distances of ca 1.88 Å.

In the structure of the title compound, C27H21P, at 89 (2) K the P atom is bound to the allylic carbon of the indenyl unit with P-C distances of ca 1.88 angstrom.

The ansa-aluminocene compound [Me4C2(C5H4)(2)Al-mu-Cl](2) (2) was prepared by reacting [Me4C2(eta(5)-C5H4)(2)Mg] with AlCl3. Addition of THF and t-butyl isocyanide to 2 produced the corresponding monomeric Lewis base adducts [Me4C2(eta(5)-C5H4)(2)Al(L)] (L = THF (3), t-BuNC (4)). X-ray crystal structure determinations revealed (eta(1), eta(5)) (eta(1), eta(3)), and (eta(1), eta(3)) combinations of cyclopentadienyl ring hapticities for 2, 3, and 4, respectively. The solution structures and fluxional behavior of the compounds were characterized using a battery of dynamic and 2-D NMR techniques. Line shape analysis of variable temperature H-1 and C-13{H} NMR spectra of 2 in toluene-d(8) yielded an activation barrier (Ea) of 8 kcal mol(-1) for the dynamic averaging of proton and carbon environments of the bridged dicyclopentadienyl ligand framework. Circumambulatory migration of aluminum about its cyclopentadienyl rings could be ruled out as the source of this averaging. The cyclopentadienyl ring coordination modes that were identified in the solution spectra of 2 and 4 at slow exchcange (eta(1), eta(1) and eta(2), eta(3), respectively) are considerably different from the ones found in the crystal structures of the compounds. Besides rearrangements in the bonding between aluminum and its cyclopentadienyl rings, there is another dynamic process, possibly inversion at aluminum, that leads to additional signal averaging in the H-1 and C-13{H-1} NMR spectra of compound 4. (c) 2005 Elsevier Ltd. All rights reserved.

An entry from the Cambridge Structural Database, the world’s repository for small molecule crystal structures. The entry contains experimental data from a crystal diffraction study. The deposited dataset for this entry is freely available from the CCDC and typically includes 3D coordinates, cell parameters, space group, experimental conditions and quality measures.