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Cadmium zinc telluride (CZT) spectrometers have been considered for objectives and missions with variable ambient temperatures. Spectrometer-grade crystals of various sizes have been studied under conditions as low as-40°C for 2 × 2 × 2 and 5 × 5 × 2-mm³ crystals, and -10°C for 5 × 5 × 5-mm³ crystals for resolution improvement spanning 5.9-, 59.5-, and 122-keV photo peak energies. It is unclear from previously published data if cooling the spectrometer-grade crystals beyond -10°C results in increased resolution improvement or if the effect occurs with higher-energy photo peaks and trends among multiple crystals from the same manufacturer. Therefore, we acquired two CZT crystals from Kromek and cooled them in an insulated box to -25°C. Our measurements were performed every 5°C, and tested with 241Am or 241Am/152Eu mixed sources. The 241Am peaks were compared for both crystals, and the higher-energy resolution changes were explored using the mixed source. Overall, at 59.5 keV, both crystals yielded 3% to 4% resolution improvement for the cooling cycle and 6% improvement during the warming cycle. Resolution performance varied between the two tested crystals, and each had a different temperature where we observed optimum resolution. The 121.8-keV peak resolution improved by 1.2% for the cooling cycle and 3.6% for the warming cycle. There were no discernable resolution increases or changes for the two higher-energy peaks, 224.7 and 334.3 keV, respectively. Slight cooling of the CZT crystals can increase resolution performance by 4% in the lower-energy region. [ABSTRACT FROM AUTHOR]

In this work, the fabrication of microstencils for patterning on unconventional substrates was demonstrated. Stencil feature sizes ranging from 6 to 370 µm with aspect ratios (stencil feature height: width) in the range of 0.5:1 to 15:1 were fabricated using ICP etching of silicon. The stenciling process was demonstrated for the deposition of metals (Ti/Au) and dielectrics (silicon dioxide) onto silicon, glass, and polymer based substrates for microfiuidic system development. The results demonstrated some dependency of the deposition rate on the stencil feature size and aspect ratio. Results from adhesion studies showed excellent adhesion on all substrates with the exception of PMMA. [ABSTRACT FROM AUTHOR]

Screening of colorectal cancer is crucial for early stage diagnosis and treatment. Detection of volatile organic compounds (VOCs) of the metabolome present in exhaled breath is a promising approach to screen colorectal cancer (CRC). Various forms of volatile organic compounds (VOCs) that show the definitive signature for the different diseases including cancers are present in exhale breathe. Among all the reported CRC VOCs, cyclohexane, methylcyclohexane, 1,3-dimethyl- benzene and decanal are identified as the prominent ones that can be used as the signature for CRC screening. In the present investigation, detection of the four prominent VOCs related to CRC is explored using functionalized titania nanotubular arrays (TNAs)-based sensor. These signature biomarkers are shown to be detected using nickel-functionalized TNA as an electrochemical sensor. The sensing mechanism is based on the electrochemical interaction of nickel-functionalized nanotubes with signature biomarkers. A detailed mechanism of the sensor response is also presented. [ABSTRACT FROM AUTHOR]

Highlights: [•] Simple electrodeposition method to fabricate NiO/Co2O3 composite electrode. [•] Specific capacitance in excess of 400Fg−1 for NiO/Co2O3 composite electrode. [•] More than 50% capacitance retention after 200 cycles of continuous CV scan. [Copyright &y& Elsevier]

Abstract: A hierarchical nanoporous-TiO2 nanotube composite structure consisting of a nanoporous top layer with smooth underlying nanotubes was obtained by a single-step anodization technique. The growth of such composite structure has also been applied to Ti wire substrate for the first time. The photoelectrochemical performance was examined under AM 1.5 simulated solar irradiation in 1 M KOH electrolyte. In general, the hierarchical architecture demonstrated improved photoelectrochemical activity over plain TiO2 nanotubes. Furthermore, the composite structure on a wire substrate was also found to enhance photoelectrochemical activity over a foil substrate. Under optimized conditions, over a 40% increase in hydrogen generation for hierarchical nanotubes over plain nanotubes is observed and over 25% increase in hydrogen generation using a wire substrate over a foil substrate is observed. [Copyright &y& Elsevier]

Abstract: Fabrication of titanium dioxide nanotube (TNT)–cadmium oxide (CdO) composite array by galvanostatic deposition technique through careful optimizations of the deposition parameters has been performed. Three different morphologies, nanocrystallites, layered, and particle agglomerate, of the CdO are obtained depending on the deposition time. The TNT/CdO composite arrays, as formed, showed significant enhancement in photoelectrochemical properties compared to pure TNT. Moreover, it is demonstrated that the nanocrystallite morphology of the CdO is the best choice for this particular application. [Copyright &y& Elsevier]

Abstract: A nanotubular composite of TiO2–WO3 was synthesized via anodic oxidation of titanium in a single-step process using phosphotungstic acid as the tungsten source. The composite material was evaluated for photoelectrochemical water splitting and demonstrated a 46% increase in conversion efficiency by incorporating WO3 compared to TiO2 nanotubes prepared under similar conditions. [Copyright &y& Elsevier]

A field enhanced flow reactor using bias assisted photocatalysis was developed for bacterial disinfection in lab-synthesized and natural waters. The reactor provided complete inactivation of contaminated waters with flow rates of 50 mL/min. The device consisted of titanium dioxide nanotube arrays, with an externally applied bias of up to 6 V. Light intensity, applied voltage, background electrolytes and bacteria concentration were all found to impact the device performance. Complete inactivation of Escherichia coli W3110 (~ 8 × 10 3 CFU/mL) occurred in 15 sec in the reactor irradiated at 25 mW/cm 2 with an applied voltage of 4 V in a 100 ppm NaCl solution. Real world testing was conducted using source water from Emigration Creek in Salt Lake City, Utah. Disinfection of natural creek water proved more challenging, providing complete bacterial inactivation after 25 sec at 6 V. A reduction in bactericidal efficacy was attributed to the presence of inorganic and organic species, as well as the increase in robustness of natural bacteria. [ABSTRACT FROM AUTHOR]

Microfluidic photocatalytic reactors have advantages over conventional bulk reactors such as large surface-area-to-volume ratio and high control of fluid flow. Although titania nanotubular arrays (TNA) have shown enhanced photocatalytic degradation compared to nanoparticle films in a batch reactor configuration, their application in a microfluidic format has yet to be explored. The photocatalytic performance of a microfluidic reactor with TNA catalyst was compared with the performance of microfluidic format with TiO 2 nanoparticulate (commercial P25) catalyst. The microfluidic device was fabricated using non-cleanroom based soft lithography, making it suitable for economical large scale manufacturing. The photocatalytic performance was evaluated at different flow rates ranging from 25 to 200 μL/min. The TNA microfluidic system demonstrated enhanced photocatalytic performance over microfluidic TiO 2 nanoparticulate layers, especially at higher flow rates (50–200 μL/min). For instance, 12 μm long TNA was able to achieve 82% fractional conversion of 18 mM methylene blue in comparison to 55% conversion in case of the TiO 2 nanoparticulate layer at a flow rate of 200 μL/min. A computational model of the microfluidic format was developed to evaluate the effect of diffusion coefficient and rate constant on the photocatalytic performance. The improved performance of the TNA photocatalyst over the nanoparticle film can be attributed to higher generation of oxidizing species. [ABSTRACT FROM AUTHOR]

The use of doped luminescent nanocrystals or quantum dots have mainly been explored for imaging applications; however, recently they have gained interest in solar energy conversion applications due to long electron lifetimes, tunable band gaps and emission by compositional control. In this study, we have examined the application of Mn or Co doped CdS nanocrystals as a sensitizing layer over titania nanotubular arrays synthesized via electrochemical anodization in photoelectrochemical applications. The doped and undoped CdS nanocrystals were simultaneously synthesized and deposited onto the titania surface by adoption of a successive ion layer adsorption-reaction (SILAR) method. Various characterization methods indicate lattice incorporation of the dopant within CdS. The addition of dopants to CdS was found to improve the photoelectrochemical performance by increasing the depletion width of the CdS nanocrystals and reducing recombination losses of charge carriers. [ABSTRACT FROM AUTHOR]

Abstract: Nano-porous oxide layers on the surface of 302-type stainless steel were synthesized by galvanostatic anodization process carried out at two current densities, 7 and 15 mA cm−2 for the time periods of 15 and 30 min. A relatively thinner (∼300 nm) and compact oxide layer formed when anodization was performed at a current density of 7 mA cm−2. However, with increase in anodization current density, the oxide layer not only grew thicker but also changed in morphology. It was found to be about 0.7 and 1.2 μm after 15 and 30 minutes of anodization at 15 mA cm−2, respectively. The XRD analysis of the oxide layer suggested the formation of hematite ((Fe, Cr)2O3) and spinel ((Ni, Cr, Fe)3O4) phases. The cyclic voltammetry and galvanostatic charge-discharge studies (1 M Li2SO4) suggested that the nature of the capacitance of the anodized stainless steel electrodes were of predominantly electric double layer (EDL) type together with some pseudocapacitance like behavior. The specific capacitance obtained was higher for the sample anodized at higher current density (15 mA cm−2) than that of the sample anodized at lower current density (7 mA cm−2). The results were also complimented by electrochemical impedance spectroscopic (EIS) analysis. [Copyright &y& Elsevier]

• 3D SN Method TRIGA Reactor Core Calculation. • Criticality Problem Energy Group Collapsing and Geometry Homogenization. • Computational Verification of TRIGA Core Calculation. • Experimental Validation of 3D SN Method TRIGA Reactor Core Calculation. • High Performance Parallel Computation. We present a systematic and detailed approach to simulate the University of Utah TRIGA Reactor (UTR) in support of core criticality calculations to profile the entire reactor in detail. In performing this work, we utilized both a 3-D Cartesian S N deterministic code, PENTRAN, and a Monte Carlo code, MCNP6, to calculate complimentary, high accuracy 3-D transport derived neutron flux distributions at reactor full power. For deterministic models, our study shows that a 14-group CONTRIBUTON weighted multi-group cross-section library with up-scattering compared extremely well with continuous energy Monte Carlo results. We also modeled results to confirm the activity of an activated arsenic sample placed in the heavy water moderated thermal irradiation chamber of the UUTR (University of Utah TRIGA Reactor). A 138 pcm difference in the system eigenvalue for the full 3-D core PENTRAN discrete ordinates (S N) UUTR model utilizing 2 × 109 equations, in 14 energy groups, is compared to the reference case of a similar full core MCNP6 Monte Carlo calculation with continuous energy cross-sections. On average, deterministic and Monte Carlo core neutron group flux values differ by less than 1%, with some local maximum relative differences between 10% and 20% for the 3-D core flux distribution in some energy groups are observed. The differences of neutron fluxes from group 3/14 to group 10/14, with energies spanning from 1.11 eV to 13.8 MeV, are comparable to within 5% in the UUTR core active fuel region. For energy groups with energies greater than 13.8 MeV, MCNP6 is not able to resolve the flux distributions with reasonable statistical uncertainties due to the extremely low sampling probability for neutrons in those energies; orders of magnitude more histories would be required to do so. In contrast, the PENTRAN 3D S N calculation shows a very detailed flux distribution for energies larger than 13.8 MeV, highlighting the complimentary utility of applying both methods. Detailed approaches for the PENTRAN calculation, including energy group collapsing, homogenization of fuel + gap + cladding, and analysis are presented in the narrative. [ABSTRACT FROM AUTHOR]

Growth of TiO2 nanotubes on thin Ti film deposited on Si wafers with site-specific and patterned growth using a photolithography technique is demonstrated for the first time. Ti films were deposited via e-beam evaporation to a thickness of 350–1000 nm. The use of a fluorinated organic electrolyte at room temperature produced the growth of nanotubes with varying applied voltages of 10–60 V (DC) which remained stable after annealing at 500 °C. It was found that variation of the thickness of the deposited Ti film could be used to control the length of the nanotubes regardless of longer anodization time/voltage. Growth of the nanotubes on a SiO2 barrier layer over a Si wafer, along with site-specific and patterned growth, enables potential application of TiO2 nanotubes in NEMS/MEMS-type devices. [ABSTRACT FROM AUTHOR]