Radiation tolerant nano-FED biosensing for space application

A p-type polysilicon nanowire and silicon nano-channel combination based biosensor was developed, which has the potential to detect pathogens and thus protect crew safety aboard long-term manned flight programmes in high radiation space flights. This study outlines structures, which compose the biosensor, and demonstrates that the nano-device utilised herein is total dose radiation hardened. Highly doped polysilicon nanowires (30–100?nm) in nano-field-effect device (FED) were fabricated on silicon/silicon dioxide wafers and insulated with a thin polyimide layer. When the targeted gene, Escherichia coli DH5 alpha 16S rRNA, incubated on the device surface, the constant overall impedance increased or decreased depending on the electronic charge, mass and composition of the target molecule. All measurements were carried under 25 MeV S-Band linear accelerator followed by impedance measurements. Current sets of experiments show these nano-FED can form the basis of a robust, very sensitive handheld tool for pathogen detection in space application.     

热轧加热炉内步进梁及立柱耐火材料粘渣原因分析

分析了热轧加热炉内步进梁与立柱粘渣的原因,认为所用耐火材料荷重软化温度低、变形大是主要原因之一。从侵蚀结构分析看,氧化铝溶解进入炉衬的粘接渣相中,增加了渣的黏度,可能导致炉衬的严重挂渣,不利于生产的正常顺行。常规的加热炉耐火材料控制标准没有荷重软化温度等指标,不利于控制炉衬实物质量。     

Flexible rewritable organic memory devices using nitrogen-doped CNTs/PEDOT:PSS composites

Nonvolatile rewritable organic memory devices based on poly(3,4-ethylene dioxythiophene):poly(styrenesulfonate) (PEDOT:PSS) and nitrogen doped multi-walled carbon nanotube (NCNT) nanocomposites were fabricated on glass and PET substrates.Organic memory devices with bistable resistive switching were obtained using very low NCTN concentration (∼0.002 wt%) in the polymeric matrix. The memory devices exhibited a good ON/OFF ratio of approximately three orders of magnitude, a good retention time of 10⁴ s under operating voltages ≤ |4V| and a few hundredths of write-read-erase-read cycles. The bistable resistive switching is mainly attributed to the creation of oxygen vacancies. These defects are introduced into the thin native Al oxide (AlOx) layer on the bottom electrode during the first voltage sweep. The well-dispersed NCNTs immersed in PEDOT:PSS play a key role as conductive channels for the electronic transport, hindering the electron trapping at the AlOx-polymer interface and inducing a soft dielectric breakdown of the AlOx layer. These PEDOT:PSS + NCNTs memory devices are to easy to apply in flexible low-cost technology and provide the possibility of large-scale integration.     

Theoretical and experimental investigations of the thermoelectric properties of Al-, Bi- and Sn-doped ZnO

In this paper, the thermoelectric properties of ZnO doped with Al, Bi and Sn were investigated by combining experimental and theoretical methods. The average Seebeck coefficient of Bi doped ZnO over the measured temperature range is improved from −90 to −497 μV/K. However, segregation of Bi₂O₃ in ZnO:Bi sample, confirmed by FESEM, lead to enormous grain growth and low electrical conductivity, which makes Bi is not a good dopant to improve ZT value of ZnO. As a 4+ valence cation, Sn doping actually show an increase in carrier concentration to 10²⁰ cm⁻³, further enhancing the electrical conductivity. Unfortunately, the Seebeck coefficient of ZnO:Sn samples is even lower than pure ZnO sample, which lead to a low ZT value. As for ZnO:Al sample, with nearly no change in lattice thermal conductivity, electrical conductivity and Seebeck coefficient were both enhanced. Threefold enhancement in ZT value has been achieved in ZnO:Al sample at 760 °C compared with pure ZnO.     

Transition metal oxides on organic semiconductors

Transition metal oxides (TMOs) on organic semiconductors (OSs) structure has been widely used in inverted organic optoelectronic devices, including inverted organic light-emitting diodes (OLEDs) and inverted organic solar cells (OSCs), which can improve the stability of such devices as a result of improved protection of air sensitive cathode. However, most of these reports are focused on the anode modification effect of TMO and the nature of TMO-on-OS is not fully understood. Here we show that the OS on TMO forms a two-layer structure, where the interface mixing is minimized, while for TMO-on-OS, due to the obvious diffusion of TMO into the OS, a doping-layer structure is formed. This is evidenced by a series of optical and electrical studies. By studying the TMO diffusion depth in different OS, we found that this process is governed by the thermal property of the OS. The TMO tends to diffuse deeper into the OS with a lower evaporation temperature. It is shown that the TMO can diffuse more than 20 nm into the OS, depending on the thermal property of the OS. We also show that the TMO-on-OS structure can replace the commonly used OS with TMO doping structure, which is a big step toward in simplifying the fabrication process of the organic optoelectronic devices.     

ZnO nanoparticle suspensions containing citric acid as antimicrobial to control Listeria monocytogenes,Escherichia coli,Staphylococcus aureus and Bacillus cereus in mango juice

Zinc oxide (ZnO) nanoparticles have been proven to have strong antibacterial activity against food borne pathogens. The practical applications of different concentrations (0, 1, 3, 5 and 8 mM) of ZnO suspensions containing 0.3% citric acid were investigated against the pathogenic bacteria like, Listeria monocytogenes, Escherichia coli, Staphylococcus aureus and Bacillus cereus. Zinc oxide suspensions (0, 1, 3, 5 and 8 mM) containing citric acid have shown a significant inhibitory effect on the growth of all strains during 12 h of incubation. Our results have also shown that 5 and 8 mM suspensions of ZnO were the most effective on all strains. These data suggested that the antibacterial activity of ZnO was concentration dependent. Thus 5 mM and 8 mM ZnO were selected for further studies, carried out in mango juice, as they showed a significant growth inhibition in TSB. ZnO NPs were more capable of reducing initial growth counts of all the above stated strains in mango juice. Results have also exhibited that ZnO and citric acid had inhibitory effect on the growth of all strains during 24 h culture period in mango juice, as compared to the control experiment, which was further confirmed in liquid culture. This is the first report, describing the antibacterial activity of ZnO NPs in mango juices that showed the potential of these nanoparticles for use as an antibacterial agent in the food industry.     

Factors affecting aluminum depletion during cyclic oxidation of Fe-base alumina-forming alloys

Abstract

In order to develop an improved oxidation-limited lifetime model, experiments are being conducted to assess the critical factors that affect the rate of Al loss from Fe-base alumina-forming alloys during cyclic oxidation. Both wrought and dispersion strengthened ferritic and intermetallic Fe–Al±Cr alloys are being investigated at exposure temperatures from 1100–1300°C. Higher temperatures, thinner specimens and cycle frequency are used to accelerate degradation during oxidation. However, the effects of these experimental choices often have not been critically assessed in prior work. Electron probe microanalysis has been used to measure the residual Al content under various conditions and at various stages of life. For 0.5–2mm thick specimens, lifetime repeatedly showed a linear relationship to thickness. Increasing the oxidation temperature appears to be the most viable strategy to accelerate the evaluation of oxidation resistance for comparing and developing alloys.     

Size dependent ferromagnetism in dodecyl amine capped ZnO nanoparticles

We investigated the size dependent ferromagnetism in dodecyl amine capped zinc oxide nanoparticle. X-ray diffraction and X-ray photoelectron spectroscopy analysis demonstrated that density of oxygen vacancies was enhanced due to an increase in compressive strain concomitant with the decrease in particle size. Magnetic measurements showed increased ferromagnetic ordering in ZnO nanoparticles with reduced particle size. It was also found that the increase in coercive field, saturation magnetization and magnetic hysteresis loop area were invariably associated with increased oxygen defect population. The observed ferromagnetism in organic capped zinc oxide nanocrystals has therefore been assigned to defect induced phenomena. Results of sample characterization using optical absorption spectroscopy, photo luminescence spectroscopy and high resolution transmission electron microscope have also been presented.     

Fabrication of large area flexible and highly transparent film by a simple Ag nanowire alignment

This article describes the fabrication of a flexible polymer thin film incorporating a highly aligned Ag nanowire array, resulting in high transparency and polarisation that are useful for potential applications to optical filters, electronic and optical devices and negative refractive index materials.     

Electrochemical Study on the Reduction Mechanism of Uranium Oxide in a LiCl-Li2O Molten Salt

By means of a linear sweep voltammetry, a cyclic voltammetry and a chronopotentiometry, the electrolytic reduction of uranium oxide has been studied to establish the reduction mechanisms, which are based on a simultaneous uranium oxide reduction and a Li₂O electrowinning, and the formation and electrolysis of lithium uranate. From the voltammograms, the reduction potentials of the uranium oxide and Li₂O were obtained. From the chronopotentiometries based on the results of the voltammograms, the uranium oxide was reduced to uranium metal through the reduction mechanisms showing a more than 99% conversion. For a verification of the reduction mechanisms feasibility, basic data on the electrolytic reduction of the uranium oxide was obtained from the experiments and the characteristics of the closed recycle of Li₂O were discussed.