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AbstractCadmium 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-mm3crystals, and −10°C for 5 × 5 × 5-mm3crystals 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.

Plasmon-enhanced photocatalysis has the potential to reduce activation energies and decrease temperature requirements, which increases catalyst stability and lowers process operating costs. The near-field enhancement that occurs at junctions between plasmonic nanoparticle clusters (i.e., hot spots) has been well-studied for sensing applications (e.g., Raman scattering). However, experimental insight into the effect of nanoparticle cluster hot spots on plasmon-enhanced photocatalysis is lacking. We demonstrate that catalytic activity is increased when clusters of gold nanoparticles (AuNPs) are formed relative to isolated particles using the same catalyst loading. Through experimental controls, we conclude that this catalytic enhancement is most likely due to the formation of plasmonic hot spots. Clusters of AuNPs were formed by adding L-cysteine to an AuNP dispersion, and a 20 ± 12% enhancement in the photocatalytic dye degradation rate was observed using a Fenton process. While this report may be a modest enhancement relative to the spectacular near-field electromagnetic field enhancements predicted by simulation at the nanoparticle junction, this finding supports the recent work of Srimanta et al. that plasmonic hot spots contribute to catalytic rate enchantments. It is anticipated that further self-assembly strategies to optimize interparticle orientations and cluster size distributions will improve the enhancement due to the formation of hot spots, and careful control will be required. For example, excess L-cysteine addition revealed extensive aggregation and subsequent rate reductions.

This article explores a new, highly scalable bioreactor design for photosynthetic, lipid producing organisms. Microalgae are important to the recovery of resources from wastewater and microalgae derived oils have the potential to become an important source of transportation fuels, but current photobioreactor designs are not readily scalable. In contrast, this article evaluates the productivity of periodic designs that use repeated unit cells defined by fluid dynamically driven recirculation profiles so that scaleup may be achieved simply by increasing (massively) the number of unit cells. Photobioreactors with one, seven, and nineteen unit cells were constructed containing 13.2, 92.4, and 251 gal, respectively, to demonstrate scalability. Development of a kinetic growth model accounting for variations in photointensity versusdepth predicts approximately linear (instead of exponential) growth as observed in the first week of productivity. This design decreases the required power per volume by over 50% compared to paddlewheel designs, and material costs per unit cell decrease with increasing reactor size, because flow symmetry defines the boundaries of the unit cells in the absence of internal material walls. These results provide a more efficient path to scale up to commercially relevant acreage, bringing algal biofuels closer to energy parity.

Titania nanotubular arrays (TNA) synthesized via electrochemical anodization is a stable and versatile material, widely studied for photocatalytic and sensing applications, whereas nano-sized gold particles are a known plasmonic material. Semiconductor￢ﾀﾓmetal nanocomposites in isolated, embedded, or encapsulated form, when irradiated with proper light frequency can exhibit localized surface plasmon resonance (LSPR) effect. This effect can result in improved light adsorption and electrical properties of a material. In this study, we report the enhanced visible light photo-response of LSPR induced volatile organic biomarker vapor sensing at room temperature using a Au-embedded TNA electrochemical sensor. Two mechanisms are proposed. One based on classical physics (band theory), which explains operation under non-irradiated conditions. The second mechanism is based on the coupling of classical and quantum physics (molecular orbitals), and explains sensor operation under irradiated conditions. [ABSTRACT FROM AUTHOR]

Detection of specific breath-based volatile organic biomarkers (VOBs) directly associated with a pulmonary disease like tuberculosis presents itself as a potential non-invasive, and point-of-care (POC) medical diagnostic technique. In this work, highly ordered titania nanotubular arrays (TNA) synthesized through electrochemical anodization and functionalized with cobalt, was utilized as a robust sensing platform for electrochemical detection (amperometric mode) of four prominent tuberculosis volatile biomarker. The limit of detection of the sensor was determined to be [?]0.018 ppm VOBs, with the sensor exhibiting higher selectivity toward the VOBs over other organics commonly found in breath. The sensor response theory modeled using Butler-Volmer kinetics at high overpotentials (Tafel behavior) corroborates well with experimentally derived signal responses. Of the four VOBs examined, methyl p-anisate exhibits the maximum current response (81 uA), while methyl nicotinate demonstrates the fastest reaction kinetics, or response time (35 seconds). The development of functionalized 1D nanostructured metal oxide semiconductor based sensors demonstrates enhanced sensor response with rapid detection times appropriate for POC disease diagnosis.

Anodic titania nanotube arrays have been extensively explored for gas sensing applications due to their high chemical and thermal stability and robust synthesis method. In this study, we explore the use of functionalized titania nanotube arrays for the electrochemical detection of gaseous volatile organic biomarkers associated with tuberculosis. The synthesis method developed allows for in situ functionalization of titania nanotubes with oxygen containing metal species (i.e., Co(OH)2) during anodization. Amperometric detection of volatile organic biomarkers with concentrations of 275 [?] 360 ppm using next generation titania nanotubes functionalized with Co(OH)2 where compared with Co(OH)2 functionalized titania nanotubes via a wet incipient method. Improved sensor response and sensitivity was observed with next generation titania nanotubes, which can be attributed to homogeneous distribution of reactive sites directly in contact with the parent titania. A mechanism for sensor response and in situ functionalization is presented.

Electrochemical anodization of Ti-W nano-composite thin films deposited on a Si substrate by simultaneous magnetron sputtering of Ti and W resulted in the formation of TiO2-WO3 nanotubular -arrays. A change in the morphology of TiO2-WO3 composite nanotubes with varying percentage of W in Ti-W composite thin films was observed. The oxide film compositions were characterized by XPS and Laser Ablation ICP-MS, of which the latter demonstrated to give a good representation of the overall oxide composition. With a W density of less than or equal to 5.25 x 1018 of W atoms per cm3, the morphology of the composite nanotubes were similar to that of plain TiO2 nanotubes. Whereas with further increase in W density resulted in a nanoporous morphology.

Electrochemical anodization of a Ti-W nano-composite thin films deposited on a Si substrate by simultaneous magnetron sputtering of Ti and W resulted in the formation of TiO2-WO3 nanotubular arrays. A change in the morphology of TiO2-WO3 composite nanotubes with varying percentage of W in Ti-W composite thin films was observed. With a W density of less than or equal to 1.75 x 1019 W atoms per cm3 (after anodization), the morphology of the composite nanotubes were similar to that of plain TiO2 nanotubes. Whereas with further increase in W density resulted in a nanoporous morphology. Ti-W composite films were also deposited on Si substrates with a 100 nm thick layer of tin doped indium oxide (ITO) to examine the PEC activity of the formed oxide composites. The TiO2-WO3 composite nanotubes with 1.05 x 1019 W atoms per cm3 (3.15 x 1018 W atoms per cm3 before anodization) demonstrated to be an optimal W density for this system, giving rise to 40% increase in photocurrent at 0.5 V (vs. Ag/AgCl) compared to plain TiO2 nanotubes.

Bismuth oxide (Bi2O3) decorated titania nanotube array (T-NT) composite materials were synthesized by a simple, yet versatile electrodeposition method. The effects of deposition current density and time on morphology evolution of the bismuth oxide phase were analyzed. It was found that an optimum deposition condition in terms of current density and time could be reached to achieve uniform and equiaxed crystal morphology of the deposited oxide phase. The morphology, shape, size distribution, and crystal structure of the bismuth oxide phase were evaluated using scanning electron microscopy (SEM), X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), and Raman spectroscopic techniques. The electrochemical capacitance of the T-NT/Bi2O3composites was studied by conducting cyclic voltammetry and galvanostatic charge–discharge experiments. These studies indicated that the capacitance behavior of the composite material was dependent on the morphology and distribution of the bismuth oxide phase. The capacitance was greatly enhanced for the composite having equiaxed and uniformly distributed bismuth oxide particles. The maximum interfacial capacitance achieved in this study was approximately 430 mF cm–2. Galvanostatic charge–discharge experiments conducted on the composite materials suggested stable capacitance behavior together with excellent capacitance retention even after 500 cycles of continuous charge–discharge operation.

Self-assembled arrays of titania nanotubes are synthesized via electrochemical anodization of Ti foils under the presence of UV–vis irradiation. Compared to control samples (anodized without light), the light-assisted anodized samples exhibit larger diameters as well as thicker nanotube walls, whereas the length of the nanotubes remains the same under otherwise similar synthesis conditions. Enhanced photoelectrochemical performance with light-assisted anodized samples under simulated AM 1.5 irradiation is observed by an increase in photocurrent density of 45–73% at 1.23 V (RHE). The enhanced photoelectrochemical performance is correlated to improved charge separation analyzed by Mott–Schottky. A mechanism on the photoeffect during anodization is presented. The morphology and improved properties obtained from the synthesis methodology may also find application in other fields such as sensing and catalysis

This paper describes an approach for fabricating multi-layer microfluidic systems from a combination of glass and plastic materials. Methods and characterization results for the microfabrication technologies underlying the process flow are presented. The approach is used to fabricate and characterize multi-layer plasticglass microfluidic systems containing electrical and mechanical functionality. Hot embossing, heat staking of plastics, injection molding, microstenciling of electrodes, and stereolithography were combined with conventional MEMS fabrication techniques to realize the multi-layer systems. The approach enabled the integration of multiple plasticglass materials into a single monolithic system, provided a solution for the integration of electrical functionality throughout the system, provided a mechanism for the inclusion of microactuators such as micropumpsvalves, and provided an interconnect technology for interfacing fluids and electrical components between the micro system and the macro world.

This paper describes an approach for fabricating multi-layer microfluidic systems from a combination of glass and plastic materials. Methods and characterization results for the microfabrication technologies underlying the process flow are presented. The approach is used to fabricate and characterize multi-layer plastic/glass microfluidic systems containing electrical and mechanical functionality. Hot embossing, heat staking of plastics, injection molding, microstenciling of electrodes, and stereolithography were combined with conventional MEMS fabrication techniques to realize the multi-layer systems. The approach enabled the integration of multiple plastic/glass materials into a single monolithic system, provided a solution for the integration of electrical functionality throughout the system, provided a mechanism for the inclusion of microactuators such as micropumps/valves, and provided an interconnect technology for interfacing fluids and electrical components between the micro system and the macro world.

Anodic titania nanotube arrays have been extensively explored for gas sensing applications due to their high chemical and thermal stability and robust synthesis method. In this study, we explore the use of functionalized titania nanotube arrays for the electrochemical detection of gaseous volatile organic biomarkers associated with tuberculosis. The synthesis method developed allows for in situ functionalization of titania nanotubes with oxygen containing metal species (i.e., Co(OH)2) during anodization. Amperometric detection of volatile organic biomarkers with concentrations of 275 ∼ 360 ppm using next generation titania nanotubes functionalized with Co(OH)2where compared with Co(OH)2functionalized titania nanotubes via a wet incipient method. Improved sensor response and sensitivity was observed with next generation titania nanotubes, which can be attributed to homogeneous distribution of reactive sites directly in contact with the parent titania. A mechanism for sensor response and in situ functionalization is presented.

Detection of specific breath-based volatile organic biomarkers (VOBs) directly associated with a pulmonary disease like tuberculosis presents itself as a potential non-invasive, and point-of-care (POC) medical diagnostic technique. In this work, highly ordered titania nanotubular arrays (TNA) synthesized through electrochemical anodization and functionalized with cobalt, was utilized as a robust sensing platform for electrochemical detection (amperometric mode) of four prominent tuberculosis volatile biomarker. The limit of detection of the sensor was determined to be ∼0.018 ppm VOBs, with the sensor exhibiting higher selectivity toward the VOBs over other organics commonly found in breath. The sensor response theory modeled using Butler-Volmer kinetics at high overpotentials (Tafel behavior) corroborates well with experimentally derived signal responses. Of the four VOBs examined, methyl p-anisate exhibits the maximum current response (81 μA), while methyl nicotinate demonstrates the fastest reaction kinetics, or response time (35 seconds). The development of functionalized 1D nanostructured metal oxide semiconductor based sensors demonstrates enhanced sensor response with rapid detection times appropriate for POC disease diagnosis.

Electrochemical anodization of Ti–W nano-composite thin films deposited on a Si substrate by simultaneous magnetron sputtering of Ti and W resulted in the formation of TiO2–WO3 nanotubular -arrays. A change in the morphology of TiO2–WO3composite nanotubes with varying percentage of W in Ti–W composite thin films was observed. The oxide film compositions were characterized by XPS and Laser Ablation ICP-MS, of which the latter demonstrated to give a good representation of the overall oxide composition. With a W density of less than or equal to 5.25 x 1018 of W atoms per cm3, the morphology of the composite nanotubes were similar to that of plain TiO2 nanotubes. Whereas with further increase in W density resulted in a nanoporous morphology.

Electrochemical anodization of a Ti–W nano-composite thin films deposited on a Si substrate by simultaneous magnetron sputtering of Ti and W resulted in the formation of TiO2–WO3nanotubular arrays. A change in the morphology of TiO2–WO3composite nanotubes with varying percentage of W in Ti–W composite thin films was observed. With a W density of less than or equal to 1.75 × 1019W atoms per cm3(after anodization), the morphology of the composite nanotubes were similar to that of plain TiO2nanotubes. Whereas with further increase in W density resulted in a nanoporous morphology. Ti–W composite films were also deposited on Si substrates with a 100 nm thick layer of tin doped indium oxide (ITO) to examine the PEC activity of the formed oxide composites. The TiO2–WO3composite nanotubes with 1.05 × 1019W atoms per cm3(3.15 × 1018W atoms per cm3before anodization) demonstrated to be an optimal W density for this system, giving rise to 40% increase in photocurrent at 0.5 V (vs. Ag/AgCl) compared to plain TiO2nanotubes.