Observation of room temperature negative differential resistance in solution synthesized ZnO nanorod

We report the observation of negative differential resistance (NDR) in solution synthesized ZnO nanorod. The ZnO nanorod was fabricated as a two terminal planar device using lithographically patterned Au electrodes. The measured current–voltage response of the device has shown a negative differential resistance behavior. The peak-to-valley current ratio of the NDR is found to be greater than 4. The mechanism of this observed NDR effect has been explained based on charge trapping and de-trapping at the nanoscale contacts. It is the first observation of negative differential resistance effect in solution synthesized ZnO nanorod.     

Polycaprolactone solution–based ink for designing microfluidic channels on paper via 3D printing platform for biosensing application

This work reports a novel fabrication technique for development of channels on paper‐based microfluidic devices using the syringe module of a 3D printing syringe–based system. In this study, printing using polycaprolactone (PCL)‐based ink (Mw 70 000‐90 000) was employed for the generation of functional hydrophobic barriers on Whatman qualitative filter paper grade 1 (approximate thickness of 180 μm and pore diameter of 11 μm), which would effectively channelize fluid flow to multiple assay zones dedicated for different analyte detection on a microfluidic paper‐based analytical device (μPAD). The standardization studies reveal that a functional hydrophilic channel for sample conduction fabricated using the reported technique can be as narrow as 460.7 ± 20 μm and a functional hydrophobic barrier can be of any width with a lower limit of about 982.2 ± 142.75 μm when a minimum number of two layers of the ink is extruded onto paper. A comparison with the hydrodynamic model established for writing with ink is used to explain the width of the line printed by this system. A fluid flow analysis through a single channel system was also carried out to establish its conformity with the Washburn model, which governs the fluid flow in two‐dimensional μPAD. The presented fabrication technique proves to be a robust strategy that effectively taps the advantages of this 3D printing technique in the production of μPADs with enhanced speed and reproducibility.     

A Microelectronic Sensor Device Powered by a Small Implantable Biofuel Cell

Biocatalytic buckypaper electrodes modified with pyrroloquinoline quinone (PQQ)-dependent glucose dehydrogenase and bilirubin oxidase for glucose oxidation and oxygen reduction, respectively, were prepared for their use in a biofuel cell. A small (millimeter-scale; 2×3×2 mm³) enzyme-based biofuel cell was tested in a model glucose-containing aqueous solution, in human serum, and as an implanted device in a living gray garden slug (Deroceras reticulatum), producing electrical power in the range of 2–10 μW (depending on the glucose source). A microelectronic temperature-sensing device equipped with a rechargeable supercapacitor, internal data memory and wireless data downloading capability was specifically designed for activation by the biofuel cell. The power management circuit in the device allowed the optimized use of the power provided by the biofuel cell dependent on the sensor operation activity. The whole system (power-producing biofuel cell and power-consuming sensor) operated autonomously by extracting electrical energy from the available environmental source, as exemplified by extracting power from the glucose-containing hemolymph (blood substituting biofluid) in the slug to power the complete temperature sensor system and read out data wirelessly. Other sensor systems operating autonomously in remote locations based on the concept illustrated here are envisaged for monitoring different environmental conditions or can be specially designed for homeland security applications, particularly in detecting bioterrorism threats.     

Remote Actuation of a Light-Emitting Device Based on Magnetic Stirring and Wireless Electrochemistry

We propose a straightforward access to a rotating light-emitting device powered by wireless electrochemistry. A magnetic stirrer is used to rotate a light-emitting diode (LED) due to the intrinsic magnetic properties of the tips that contain iron. At the same time, the LED is submitted to an electric field and acts as a bipolar electrode. The electrochemical processes that are coupled on both extremities of the LED drive an electron flow across the device, resulting in light emission. The variation of the LED alignment in time enables an alternating light emission that is directly controlled by the rotation rate. The stirring also enables a continuous mixing of the electrolyte that improves the stability of the output signal. Finally, the LED brightness can readily reveal a change of chemical composition in the electrolyte solution.     

Photo-driven water splitting photoelectrochemical cells by tandem organic dye sensitized solar cells with I−/I3− as redox mediator

Dye-sensitized photoelectrochemical tandem cells have shown the promise for light driven hydrogen production from water owing to the low cost,wide absorption spectra in the visible region and ease to process of their constitutive photoelectrode materials.However,most photo-driven water splitting photoelectrochemical cells driven by organic dye sensitized solar cells exhibit unsatisfactory hydrogen evolution rate,primarily attributed to their poor light capturing ability and low photocurrent performance.Here we present the construction of a tandem system consisting of an organic blue-colored S5 sensitizer-based dyesensitized photoelectrochemical cell(DSPEC) wired in series with three spectral-complemental dyes BTA-2,APP-3 and APP-1 sensitizers-based dye-sensitized solar cell(DSC),respectively.The two spectral-complemental chromophores were used in DSC and DSPEC to ensure that the full solar spectrum could be absorbed as much as possible.The results showed that the photocurrent of tandem device was closely related to the open-circuit voltage(Voc) of sensitized DSC,in which the tandem configuration consisting of S5 based DSPEC and BTA-2 based DSC gave the best photocurrent.On this basis,tandem device with the only light energy and no external applied electrical bias was further constructed of BTA-2 based 2-junction DSC and S5 based DSPEC and obtained a photocurrent of 500 μA cm-2 for hydrogen generation.Furthermore,I-/I3-was used as a redox couple between dye regeneration and O2 production on the surface of Pt-IrO2/WO3.The strategy opens up the application of pure organic dyes in DSC/DSPEC tandem device.     

可拉伸超韧水凝胶的制备和应用

综述了可拉伸超韧水凝胶的设计原理及其在组织工程和柔性电子器件领域的应用. 通过将网络结构层次、 化学结构、 增韧机制与宏观力学性能相结合, 重点讨论了单网络水凝胶、 双网络水凝胶、 纳米复合水凝胶及其它水凝胶等可拉伸超韧水凝胶的研究进展, 并总结和展望了新思路和新方向.     

云蒸霞蔚——多色双喷泉实验

本实验在氨气和氯化氢气体的单喷泉实验基础上设计了集两种气体的制备、收集、验满、尾气处理、气体反应、喷泉实验与试剂回收利用于一体的连续性实验,喷泉部分涉及到的实验原理有氨气与硫酸铜溶液的配位反应、氨气与氯化钴溶液的沉淀反应、无色酚酞溶液和酸性对硝基苯酚溶液在碱性环境下的变色反应,以及氯化铁和硫氰化钾在弱酸性条件下的反应等。本实验的主要仪器装置由团队自行设计、定制,操作简便,玻璃活塞还可控制喷发顺序,实现多色多样喷泉,伴随氯化铵生成时的袅袅白烟,云蒸霞蔚,煞是壮观。另外,我们设计了多角度的互动方案,针对不同程度知识背景的受众传授知识,让参观者真切感受到化学的魅力。     

The electronic band structure analysis of OLED device by means of in situ LEIPS and UPS combined with GCIB

Low-energy inverse photoelectron spectroscopy (LEIPS) and ultraviolet photoelectron spectroscopy (UPS) incorporated into the multitechnique XPS system were used to probe the ionization potential and the electron affinity of organic materials, respectively. By utilizing gas cluster ion beam (GCIB), in situ analyses and depth profiling of LEIPS and UPS were also demonstrated. The band structures of the 10-nm-thick buckminsterfullerene (C₆₀) thin film on Au (100 nm)/indium tin oxide (100 nm)/glass substrate were successfully evaluated in depth direction.     

体外预应力加固的技术研究

通过ANSYS有限元模型, 以体外预应力筋为研究对象, 对体外预应力加固的关键技术 进行了研究, 得出体外预应力的作用位置, 尽可能拟合原结构的受力状况, 保证 加固工程的安全性; 体外预应力的补强力筋, 应采用等效面积的置换原则, 使施工的过程 趋于合理; 体外力筋的连接装置, 应该``适、薄、强'; 在加固工程中, 体外预应力筋 纵向交错布筋的设置, 能提升结构的整体延性.     

Highly alkoxylated PPV copolymers for PLEDs: Syntheses, optical properties and enhancement of device lifetimes

A series of solution processible light-emitting copolymers composed of tetraalkoxy-phenylenevinylene (TALK-PPV) and dialkoxy-phenylenevinylene (DALK-PPV) has been synthesized using the Gilch polymerization route. Thermal, optical and electrochemical properties of the synthesized copolymers [poly(TALKPV-co-DALKPV)s] have been investigated and compared with those of each homopolymers, poly[2-(3,7-dimethyloctyloxy)-3,5,6-trimethoxy]-1,4-phenylenevinylene] (TALK-PPV) and poly[2-(3′,7′-dimethyloctyloxy)-5-methoxy-1,4-phenylenevinylene] (DALK-PPV). The synthesized copolymers showed a high molecular weight (Mn=∼2-3.0×10⁵) and narrow polydispersity indices (∼3). Electroluminescent devices using the copolymers as the emissive layer have been fabricated with a configuration of ITO/PEDOT:PSS/polymers/Ca/Al. Interestingly the copolymer devices resulted in a more than 4-fold increase in device lifetime than the homopolymers, which might be due to the highly reduced steric hindrance of the polymer backbone by introducing DALKPV units between the adjacent highly alkoxylated TALKPV repeating units in the polymer backbone.