All Solution‐Based Fabrication of Copper Oxide Thin Film/Cobalt‐Doped Zinc Oxide Nanowire Heterojunctions

Versatile and intriguing solution‐based processes are utilized to synthesize nanostructured materials for device applications to reduce material production and device fabrication costs. This study presents results on the fabrication and characterization of copper oxide (CuO) coated cobalt‐doped zinc oxide nanowires (Co‐doped ZnO NWs)‐based heterojunction diodes prepared by a two‐step synthesis route through combined hydrothermal growth and sol–gel spin coating. Highly dense, well‐ordered, undoped, and Co‐doped ZnO NWs were successfully grown by hydrothermal method. Complementary CuO thin films were synthesized by sol–gel method and subsequently coated onto both undoped and Co‐doped ZnO NWs through spin‐coating technique. Enhanced diode properties with a rectification ratio of 10³ at ±2 V and an ideality factor of n = 2.4 (in dark) were obtained for Co‐doped ZnO NWs‐based heterojunction diodes. The obtained results demonstrated that the investigated heterojunction diode structure fabricated by facile and cost‐effective solution‐based processes can be a promising candidate for the next generation optoelectronic devices.     

A Single‐Electrode,Dual‐Potential Ferrocene–PNA Biosensor for the Detection of DNA

A Fc–PNA biosensor (Fc: ferrocenyl, C₁₀H₉Fe) was designed by using two electrochemically distinguishable recognition elements with different molecular information at a single electrode. Two Fc–PNA capture probes were therefore synthesized by N‐terminal labeling different dodecamer PNA sequences with different ferrocene derivatives by click chemistry. Each of the two strands was thereby tethered with one specific ferrocene derivative. The two capture probes revealed quasi‐reversible redox processes of the Fc^0/+ redox couple with a significant difference in their electrochemical half‐wave potentials of ΔE_1/2=160 mV. A carefully designed biosensor interface, consisting of a ternary self‐assembled monolayer (SAM) of the two C‐terminal cysteine‐tethered Fc–PNA capture probes and 6‐mercaptohexanol, was electrochemically investigated by square wave (SWV) and cyclic voltammetry (CV). The biosensor properties of this interface were analyzed by studying the interaction with DNA sequences that were complementary to either of the two capture probes by SWV. Based on distinct changes in both peak current and potential, a parallel identification of these two DNA sequences was successful with one interface design. Moreover, the primary electrochemical response could be converted by a simple mathematical analysis into a clear‐cut electrochemical signal about the hybridization event. The discrimination of single‐nucleotide polymorphism (SNP) was proven with a chosen single‐mismatch DNA sequence. Furthermore, experiments with crude bacterial RNA confirm the principal suitability of this dual‐potential sensor under real‐life conditions.     

Graphitic Carbon Nitride Decorated with Iron Oxide Nanoparticles as a Novel High-Performance Biomimetic Electrochemical Sensing Platform for Paracetamol Detection

Design and development of new generation smart sensors for medical applications have gained considerable interest of research community in the recent past. In this work, we propose the fabrication of highly sensitive paracetamol sensors-based iron oxide nanoparticles intercalated with graphitic carbon nitride (g-C₃N₄) (GCN) via insitu chemical synthesis. Structural features of the composites were analyzed through SEM, EDX, XRD, FTIR, and UV-Visible spectroscopic techniques. Presence of iron oxide nanoparticles in GCN, significantly improved the conductivity bare GCN from 16 to 125 S cm^?1 due to extended π–π conjugation and large surface area in the composite system. The GCN-Iron oxide (GCN-FO) nanocomposite has been employed as an electrochemical sensing platform for non-enzymatic detection of paracetamol. The electrochemical studies and cyclic voltammetry (CV) results shows that the GCN-FO composite exhibit superior electrochemical properties due to their lower values of the oxidation and reduction potentials. Electrochemical impedance spectroscopy (EIS) studies indicate decreased charge-transfer resistance for iron oxide doped GCN composite in compare to base GCN. The improved electrochemical sensing performance of modified GCN-FO composite electrode is attributed to the formation heterojunctions between iron oxide nanoparticles and GCN. The modified GCN-FO electrodes were employed for non-enzymatic electrochemical detection of PR. The GCN-FO composite electrode shows excellent sensitivity towards PR with a LOD 0.3 μM. Furthermore, the modified GCN-FO electrodes show excellent reproducibility, selectivity, stability and anti-interference performance. Due to its low-cost fabrication, superior electrochemical sensing performance, these modified GCN-FO electrodes could be a promising material for the detection of paracetamol at low concentrations.

     

Enhanced Photocatalytic Performance of Silver Decorated Zinc Oxide Nanoparticles Grown on Silica Microparticles

Silicon - Pure and Ag-decorated ZnO nanoparticles (NPs) were synthesized using a two stage of modified sol-gel technique on microsized substrates, namely sand particles in an effort to prevent...     

Electrochemical Oxidation of Phenol on Metal‐Impregnated Zeolite Electrodes

Nanodispersed metallic clusters of platinum, silver and cobalt were incorporated into NaX zeolite cavities by impregnation with acetone solution of corresponding acetylacetonates and solvent evaporation followed by acetylacetonate thermal decomposition. The mixture of modified zeolites and 10 wt % of carbon black, in the form of a thin layer, was pasted onto a glassy carbon surface by Nafion. With such electrode materials, the phenol oxidation in neutral, alkaline and acid solution was studied by cyclovoltammetry. Deactivation of all electrodes in both neutral and alkaline medium was observed, indicating that polymerization reaction might be the main reaction pathway of phenol at higher pH values. Formation of quinine‐type structures was obtained during electro‐oxidation at lower pH values, being more significant in acidic solutions.     

Protonation of Nucleobases in Single‐ and Double‐Stranded DNA

Single‐stranded model oligodeoxyribonucleotides, each containing a single protonatable base—cytosine, adenine, guanine, or 5‐methylcytosine—centrally located in a background of non‐protonatable thymine residues, were acid‐titrated in aqueous solution, with UV monitoring. The basicity of the central base was shown to depend on the type of the central base and its nearest neighbours and to rise with increasing oligonucleotide length and decreasing ionic strength of the solution. More complex model oligonucleotides, each containing a centrally located 5‐methylcytosine base, were comparatively evaluated in single‐stranded and double‐stranded form, by UV spectroscopy and high‐field NMR. The N³ protonation of the 5‐methylcytosine moiety in the double‐stranded case occurred at much lower pH, at which the duplex was already experiencing general dissociation, than in the single‐stranded case. The central guanine:5‐methylcytosine base pair remained intact up to this point, possibly due to an unusual alternative protonation on O² of the 5‐methylcytosine moiety, already taking place at neutral or weakly basic pH, as indicated by UV spectroscopy, thus suggesting that 5‐methylcytosine sites in double‐stranded DNA might be protonated to a significant extent under physiological conditions.     

Single‐Crystalline Mesoporous Molybdenum Nitride Nanowires with Improved Electrochemical Properties

We report single‐crystalline mesoporous molybdenum nitride nanowires (meso‐Mo₃N₂‐NWs) prepared by topotactic reaction using single‐crystalline molybdenum oxide nanowires. The single‐crystalline nature of meso‐Mo₃N₂‐NWs was clearly observed by field‐emission transmission electron microscopy. The meso‐Mo₃N₂‐NWs exhibited mesoporous structure with ～45 m²/g in specific surface area and ～4.6 nm in average pore size confirmed by a nitrogen sorption measurement. Due to high specific surface area and mesoporous structure, meso‐Mo₃N₂‐NWs showed much higher specific capacitance and excellent charging–discharging performance as compared with Mo₃N₂ prepared using conventional nitridation process.     

Non‐Conventional Electrochemical Techniques for Assembly of Electrodes on Glassy Carbon‐Like PPF Materials and Their Use in a Glucose Microfluidic Fuel‐Cell

This paper addresses the electrochemical growth of PtAg and Au nanoparticles on pyrolyzed photoresist films (PPFs). The PtAg/PPF electrode was evaluated toward oxygen reduction reaction (ORR) in the absence and presence of glucose; meanwhile the electrocatalytic activity of Au/PPF was investigated for the glucose electrooxidation reaction (GOR) in 0.3 M KOH in the absence and presence of air as an oxygen source. The results obtained using the electrochemical studies showed that the PtAg/PPF electrode exhibited tolerance toward the ORR in the presence of low glucose concentrations. Moreover, Au/PPF showed good affinity toward glucose oxidation at high concentrations (50 and 100 mM) in the presence of oxygen instead further oxidations of glucose by‐products. Both electrocatalysts were evaluated as the cathode (PtAg/PPF) and the anode (Au/PPF) in a glucose microfluidic fuel cell (G‐μFC) constructed using a UV‐lithography technique and several sheets of different polymeric materials. The G‐μFC was tested using 100 mM glucose with 0.3 M KOH as electrolyte in the absence of an external source of nitrogen or oxygen as the fuel at zero flow rate; this cell reached a maximum power density of 0.085 mW cm⁻² using a low Pt loading (approximately 20% of weight percentage) mixed with non‐noble materials, such as Ag.     

Flexible Use of Single‐Screw Extruders through Multiple‐Process Optimization

Using general‐purpose screws to process different types of material offers considerable cost advantages over special‐purpose screws. Designing screws of this type is generally a difficult task, since modifications to different aspects of the geometry can run counter to each other in some cases. Optimization software is thus of particular benefit here. For this reason, a program was developed for the optimization of general‐purpose screws. A central feature of this program is an appraisal system for the computer‐aided evaluation of single‐screw simulations. The performance of the software was verified on the basis of actual extrusion experiments.

Temperature measuring cross for measuring thermal homogeneity.     

Enzymatic Polymerization on DNA Modified Gold Nanowire for Label-Free Detection of Pathogen DNA

This paper presents a label-free biosensor for the detection of single-stranded pathogen DNA through the target-enhanced gelation between gold nanowires (AuNW) and the primer DNAs branched on AuNW. The target DNA enables circularization of the linear DNA template, and the primer DNA is elongated continuously via rolling circle amplification. As a result, in the presence of the target DNA, a macroscopic hydrogel was fabricated by the entanglement of the elongated DNA with AuNWs as a scaffold fiber for effective gelation. In contrast, very small separate particles were generated in the absence of the target DNA. This label-free biosensor might be a promising tool for the detection of pathogen DNAs without any devices for further analysis. Moreover, the biosensor based on the weaving of AuNW and DNAs suggests a novel direction for the applications of AuNWs in biological engineering.     

Composite Electrodes for Electrochemical Supercapacitors

Manganese dioxide nanofibers with length ranged from 0.1 to 1 μm and a diameter of about 4–6 nm were prepared by a chemical precipitation method. Composite electrodes for electrochemical supercapacitors were fabricated by impregnation of the manganese dioxide nanofibers and multiwalled carbon nanotubes (MWCNT) into porous Ni plaque current collectors. Obtained composite electrodes, containing 85% of manganese dioxide and 15 mass% of MWCNT, as a conductive additive, with total mass loading of 7–15 mg cm⁻², showed a capacitive behavior in 0.5-M Na₂SO₄ solutions. The decrease in stirring time during precipitation of the nanofibers resulted in reduced agglomeration and higher specific capacitance (SC). The highest SC of 185 F g⁻¹ was obtained at a scan rate of 2 mV s⁻¹ for mass loading of 7 mg cm⁻². The SC decreased with increasing scan rate and increasing electrode mass.     

利用配位反应法制备多孔阳极氧化铝/氧化锌纳米线阵列

研究了一种新型的制备氧化锌(ZnO)纳米线的配位反应法.以氨水为配位剂、氨水与可溶性的锌盐反应配制的锌氨配合物溶液为前驱液,在多孔阳极氧化铝(porous anodic alumina,PAA)模板中沉积了ZnO纳米线.研究了ZnO纳米线的生长机理和配位反应条件.用X射线衍射仪、扫描电子显微镜和透射电子显微镜对PAA/...     

Single‐Molecule Unzipping Force Analysis of HU–DNA Complexes

The genome of bacteria is organized and compacted by the action of nucleoid‐associated proteins. These proteins are often present in tens of thousands of copies and bind with low specificity along the genome. DNA‐bound proteins thus potentially act as roadblocks to the progression of machinery that moves along the DNA. In this study, we have investigated the effect of histone‐like protein from strain U93 (HU), one of the key proteins involved in shaping the bacterial nucleoid, on DNA helix stability by mechanically unzipping single dsDNA molecules. Our study demonstrates that individually bound HU proteins have no observable effect on DNA helix stability, whereas HU proteins bound side‐by‐side within filaments increase DNA helix stability. As the stabilizing effect is small compared to the power of DNA‐based motor enzymes, our results suggest that HU alone does not provide substantial hindrance to the motor's progression in vivo.     

Study of a Single‐Chamber Solid Oxide Fuel Cell Microstack with V‐Shaped Congener‐Electrode‐Facing Configuration

Single‐chamber solid oxide fuel cell (SC‐SOFC) microstacks with V‐Shaped congener‐electrode‐facing configuration were fabricated and operated successfully in a box‐like stainless steel chamber. Two gas channels with small gas inlets were used to transport the fuel and oxygen to the anodes and cathodes, respectively. The temperature of an anode‐facing‐anode two‐cell stack was higher than that of a cathode‐facing‐cathode two‐cell stack during the test procedure. For a three‐cell stack, the cell in the middle region presented the highest power output. The open circuit voltage (OCV) and maximum power output of the three‐cell stack in a gas mixture of 100 sccm N₂, 120 sccm CH₄, and 80 sccm O₂ were 3.0 V and 413 mW, respectively.     

Grain Growth of Zinc Oxide During the Sintering of Zinc Oxide—Antimony Oxide Ceramics

Grain growth in a high-purity ZnO with systematic additions of Sb₂O₃ from 0.29 to 2.38 wt% was studied for sintering in air from 1106° to 1400°C. The results are discussed and compared with previous studies of pure ZnO and ZnO with Bi₂O₃ additions in terms of the kinetic grain growth expression: Gⁿ – Gⁿ ₀= K ₀ t exp(— Q/RT ). Additions of Sb₂O₃ inhibited the grain growth of ZnO and increased the grain growth exponent ( n -value) to 6 from 3 for pure ZnO and 5 for the ZnO—Bi₂O₃ ceramic. The apparent activation energy for the grain growth of ZnO also increased to about 600 kJ/mol from 220 kJ/mol for pure ZnO and 150 kJ/mol for the ZnO—Bi₂O₃ ceramics. Both the grain growth exponent and the activation energy were independent of the Sb₂O₃ content. Particles of the Zn₇Sb₂O₁₂ spinel were observed on the grain boundaries and at the grain triple point junctions. It was also observed that the Sb₂O₃ additions caused twin formation in each ZnO grain. It is concluded that both the Zn₇Sb₂O₁₂ particles and the twins are responsible for the ZnO grain growth inhibition by Sb₂O₃.     

氧化锌变阻器陶瓷

介绍了用于制作变阻器的氧化锌陶瓷,阐述了含不同掺杂添加剂材料的非欧姆性状机理,并分析了材料性状与其结构的关系。