Vertically aligned single crystal TiO2 nanowire arrays grown directly on transparent conducting oxide coated glass: synthesis details and applications

Single-crystal one-dimensional (1D) semiconductor architectures are important in materials-based applications requiring a large surface area, morphological control, and superior charge transport. Titania has widespread utility in applications including photocatalysis, photochromism, photovoltaics, and gas sensors. While considerable efforts have focused on the preparation of 1D TiO2, no methods have been available to grow crystalline nanowire arrays directly onto transparent conducting oxide (TCO) substrates, greatly limiting the performance of TiO2 photoelectrochemical devices. Herein, we present a straightforward low temperature method to prepare single crystal rutile TiO2 nanowire arrays up to 5 microm long on TCO glass via a non-polar solvent/hydrophilic substrate interfacial reaction under mild hydrothermal conditions. The as-prepared densely packed nanowires grow vertically oriented from the TCO glass substrate along the (110) crystal plane with a preferred (001) orientation. In a dye sensitized solar cell, N719 dye, using TiO2 nanowire arrays 2-3 microm long we achieve an AM 1.5 photoconversion efficiency of 5.02%.     

RF channelizer architectures using 3-way iterative down conversion for concurrent or fast-switching spectrum analysis

A wide-band RF channelizer architecture using the concept of 3-way iterative down-conversion is introduced. An example RF channelizer implementation splits the input spectrum of 0.6–9 GHz into 7 channels each with a 1.2 GHz bandwidth. This RF channelizer implementation has the ability of concurrently down-converting 3 channels enabling multi-Gbps aggregate data reception. It further demonstrates the ability to rapidly switch from receiving one channel to another which is crucial for rapid spectrum analysis. A prototype of the RF channelizer has been fabricated in a 65 nm standard CMOS process. A 400 Mbps (BPSK) data reception has been demonstrated by down-converting two channels concurrently. Channel switching can be as fast as 8 ns and is always faster than \(1\,\upmu s\). The chip occupies an area of 2 mm \(\times\) 1 mm and consumes an average power of 435 mW while offering a dynamic range between 58 and 63 dB.     

Cystic resolution: a performance metric for ultrasound imaging systems

This paper describes a metric that can be used to characterize the resolution of arbitrary broadband coherent imaging systems. The metric is particularly suited to medical ultrasound because it characterizes scanner performance using the contrast obtained by imaging anechoic cysts of various sizes that are embedded in a speckle-generating background, accounting for the effect of electronic noise. We present the theoretical derivation of the metric and provide simulation examples that demonstrate its utility. We use the metric to compare a low-cost, handheld, C-scan system under development in our laboratory to conventional ultrasound scanners. We also present the results of simulations that were designed to evaluate and optimize various parameters in our system, including the f/# and apodization windows. We investigate the impact of electronic noise on our system and quantify the tradeoffs associated with quantization in the analog to digital converter. Results indicate that an f/1 receive aperture combined with 10-bit precision and a signal-to-noise ratio (SNR) of 0 dB per channel would result in adequate image quality.     

Vertically oriented Ti-Fe-O nanotube array films: toward a useful material architecture for solar spectrum water photoelectrolysis

In an effort to obtain a material architecture suitable for high-efficiency visible spectrum water photoelectrolysis, herein we report on the fabrication and visible spectrum (380-650 nm) photoelectrochemical properties of self-aligned, vertically oriented Ti-Fe-O nanotube array films. Ti-Fe metal films of variable composition, iron content ranging from 69% to 3.5%, co-sputtered onto FTO-coated glass are anodized in an ethylene glycol + NH4F electrolyte. The resulting amorphous samples are annealed in oxygen at 500 degrees C, resulting in nanotubes composed of a mixed Ti-Fe-O oxide. Some of the iron goes into the titanium lattice substituting titanium ions, and the rest either forms alpha-Fe2O3 crystallites or remains in the amorphous state. Depending upon the Fe content, the band gap of the resulting films ranges from about 380 to 570 nm. The Ti-Fe oxide nanotube array films are utilized in solar spectrum water photoelectrolysis, demonstrating 2 mA/cm2 under AM 1.5 illumination with a sustained, time-energy normalized hydrogen evolution rate by water splitting of 7.1 mL/W.hr in a 1 M KOH solution with a platinum counter electrode under an applied bias of 0.7 V. The surface morphology, structure, elemental analysis, optical, and photoelectrochemical properties of the Ti-Fe oxide nanotube array films are considered.     

Effect of diesel soot contaminated oil on engine wear — investigation of novel oil formulations

Exhaust Gas Re-circulation (EGR) has been found to be very effective in reducing emissions of oxides of nitrogen, for light duty diesel engines. However, EGR results in a sharp increase in particulate matter emissions in heavy-duty diesel engines.The effects of soot contaminated engine oil on wear of engine components was examined using a statistically designed experiment. The three oil properties studied were phosphorous level, dispersant level and sulfonate substrate level. The above three variables were formulated at two levels: High (1) and Low (−1). This resulted in a 2³ matrix (eight oil blends). The effect of soot was also taken into consideration, which resulted in a 2⁴ factorial experiment.A three-body wear machine was designed and developed to simulate and estimate the extent of wear. Ball-on-flat-disk tests were conducted to qualitatively study wear by comparing wear scars due to soot with wear scars due to a known abrasive (alumina). A Scanning Electron Microscope (SEM) was used to study the microstructures of the wear scars. Surface chemical analysis was performed on soot particles and wear scars using Energy–Dispersive X-ray Analysis (EDAX).Results show that diesel soot interacts with oil additives reducing the oil's anti-wear properties possibly by abrasive wear mechanism. Statistical analysis (GLM) showed that the phosphorous level plays a dominant role on oil's wear performance. The effect of dispersant level was not very significant, though on an average, higher dispersant levels reduced wear. The effect of sulfonate was not revealed within the range of these concentrations. Ball-on-flat-disk type tests also revealed the increased wear due to the presence of soot. SEM studies of Wear Scar Diameters suggest that soot is abrasive.     

Poly(amino acid)-facilitated electrochemical growth of metal nanoparticles

Poly(amino acids) are natural chelating agents for various metal ions. Zinc ions were encapsulated in situ in a conductive polypyrrole film using polyglutamic acid as a localized complexing agent within the film. The subsequent electrochemical reduction of the metal ions to zero-valent metal leads to the formation of the nanoparticles. The electrochemical approach demonstrated in this report provides facile regeneration of the particles and also prevents aggregation of nanoparticles in the conductive polymeric film. The correlation of the amount of zinc with the thickness of the film indicates that the zinc resides largely in the outer layer of the film. TEM and EDS data show that the nanoparticles formed are composed of zinc and are 18 +/- 7 nm in diameter. The nanoparticle/ polymer composite was used to reduce halogenated organics, indicating its potential usefulness in remediation applications.     

Ultrasensitive vapor detection with surface-enhanced Raman scattering-active gold nanoparticle immobilized flow-through multihole capillaries

We developed novel flow-through surface-enhanced Raman scattering (SERS) platforms using gold nanoparticle (Au-NP) immobilized multihole capillaries for rapid and sensitive vapor detection. The multihole capillaries consisting of thousands of micrometer-sized flow-through channels provide many unique characteristics for vapor detection. Most importantly, its three-dimensional SERS-active micro-/nanostructures make available multilayered assembly of Au-NPs, which greatly increase SERS-active surface area within a focal volume of excitation and collection, thus improving the detection sensitivity. In addition, the multihole capillary's inherent longitudinal channels offer rapid and convenient vapor delivery, yet its micrometer-sized holes increase the interaction between vapor molecules and SERS-active substrate. Experimentally, rapid pyridine vapor detection (within 1 s of exposure) and ultrasensitive 4-nitrophenol vapor detection (at a sub-ppb level) were successfully achieved in open air at room temperature. Such an ultrasensitive SERS platform enabled, for the first time, the investigation of both pyridine and 4-nitrophenol vapor adsorption isotherms at very low concentrations. Type I and type V behaviors of the International Union of Pure and Applied Chemistry isotherm were well observed, respectively.     

Analysis of colour strength,colour fastness and antimicrobial properties of silk fabric dyed with natural dye from red prickly pear fruit

In the present study, a natural dye is extracted from red prickly pear fruit (Opuntia ficus-indica) and is applied on the silk fabric using natural (myrobalan) and synthetic (copper sulphate) mordant. The dyeing of silk fabric is carried out using two different routes, namely, pre-mordanting and post-mordanting at different mordant concentrations and the dyed silk fabric was evaluated for its colour strength, colour fastness and antibacterial properties. The colour strength (K/S) was found to be higher in the post-mordant-processed fabric with the use of synthetic mordant compared to pre-mordanting and with the use of natural mordants and highest colour strength was observed at the mordant concentration of 6% and at a pH of 6 in all the cases. The colour fastness properties of the fabric also found to be improved in post-mordanting with use of synthetic mordants. The antimicrobial efficacy was also evaluated both in terms of zone of inhibition (qualitative analysis [SN195920]) and bacterial reduction % (quantitative analysis [AATCC 100]), against dyed silk fabric samples against on Staphylococcus aureus and Escherichia coli.     

Use of Friction Buttering for Overcoming HAZ Liquation Cracking

Multi-layer friction deposits in nickel-based superalloy Inconel 718 were investigated for their heat-affected zone liquation cracking resistance. The friction deposits, owing to their fine-grained microstructure with a large number of subgrain boundaries and fine, uniformly distributed carbide particles, were found to exhibit superior liquation cracking resistance to standard wrought-processed alloy 718. Based on these findings, a new technique involving friction deposition of the base plates prior to fusion welding was proposed for overcoming liquation cracking.     

Enhanced intestinal absorption and bioavailability of raloxifene hydrochloride via lyophilized solid lipid nanoparticles

The current oral therapy with raloxifene hydrochloride (RXH) is less effective due to its poor bioavailability (only 2%). Henceforth, an attempt was made to investigate the utility of triglyceride (trimyristin, tripalmitin and tristearin) based solid lipid nanoparticles (SLNs) for improved oral delivery of RXH. The SLN formulations prepared were evaluated for particle size, zeta potential and % entrapment and the optimized formulation was lyophilized. Solid state characterization studies unravel the transformation of RXH to amorphous or molecular state from the native crystalline form. Further the in situ perfusion studies carried out in rat intestine reveal the potential of SLN for enhanced permeation of raloxifene HCl across gastrointestinal barrier. To derive the conclusions, in vivo pharmacokinetic study was conducted in rats to assess the bioavailability of RXH from SLN formulation compared to drug suspension. Overall a twofold increase in bioavailability with SLN formulations confer their potential for improved oral delivery of RXH.