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.     

Prototype electrochromic device and dye sensitized solar cell using spray deposited undoped and ‘Li’ doped V2O5 thin film electrodes

Lithium (Li) (0–5 wt%) doped V₂O₅ thin films were spray deposited at 450 °C onto ITO substrates. Structural analysis using X-ray diffraction and Raman spectroscopy revealed orthorhombic phase of the films. In addition to the V₂O₅ phase, presence of VO₂ peaks due to high deposition temperature is also evident from structural and optical characterization. The non-stoichiometric nature of the films due to loss of the terminal O atom was confirmed from Raman spectroscopy. The direct band gap, indirect bandgap, and phonon energies were also calculated from optical studies. Different charge states of vanadium ions present in the film were identified from X-ray photoelectron spectroscopy study. Results from cyclic voltammetry experiments reflected significant differences between the undoped and Li doped V₂O₅ samples. Transport properties by Hall-effect measured at room temperature indicated significant increase in conductivity, carrier concentration and mobility of V₂O₅ thin films on doping with Li. A Dye Sensitized Solar Cell (DSSC) was fabricated using mobility enhanced 5 wt% Li doped V₂O₅ film as photoanode and its efficiency was found to be 2.7%. A simple electrochromic cell is fabricated using undoped V₂O₅ thin film to demonstrate the colour change.     

Comparison Study of Phenylquinoline-based Iridium(III) Complexes for Solution Processable Phosphorescent Organic Light-Emitting Diodes by PEDOT:PSS and Graphene Oxide as a Hole Transport Layer

Electroluminescent (EL) properties of Ir(III) complex, [(2,4-diphenylquinoli-ne)]₂Iridium picolinic acid N-oxide [(DPQ)₂Ir(pic-N-O)] were investigated using PEDOT:PSS and reduced graphene oxide (rGO) as a hole transport layer for solution processable phosphorescent organic light-emitting diodes (PhOLEDs). High performance solution-processable PhOLED with PEDOT:PSS and (DPQ)₂Ir(pic-N-O) (8 wt%) doped CBP:TPD:PBD (8:56:12) host emission layer were fabricated to give a high luminance efficiency (LE) of 26.9 cd/A, equivelent to an external quantum efficiency (EQE) of 14.2%. The corresponding PhOLED with rGO as a hole transport layer exhibited the maximum brightness and LE of 13540 cd/m² and 16.8 cd/A, respectively. The utilization of the solution processable rGO thin films as the hole transport layer offered the great potential to the fabrication of solution processable PhOLEDs.     

Oligosiloxane Functionalized with Pendant (1,3‐Bis(9‐carbazolyl)benzene) (mCP) for Solution‐Processed Organic Electronics

A new oligosiloxane derivative (ODCzMSi) functionalized with the well‐known 1,3‐bis(9‐carbazolyl)benzene (mCP) pendant moiety, directly linked to the silicon atom of the oligosiloxane backbone, has been synthesized and characterized. Compared to mCP, the attachment of the oligosiloxane chain significantly improves the thermal and morphological stabilities with a high decomposition temperature (T_d=540 °C) and glass transition temperature (T_g=142 °C). The silicon–oxygen linkage of ODCzMSi disrupts the backbone conjugation and maintains a high triplet energy level (E_T=3.0 eV). A phosphorescent organic light‐emitting diode (PhOLED) using iridium bis(4,6‐difluorophenyl)pyridinato‐N,C² picolinate (FIrpic) as the emitter and ODCzMSi as the host shows a relatively low turn‐on voltage of 5.0 V for solution‐processed PhOLEDs, maximum external quantum efficiency of 9.2 %, and maximum current efficiency of 17.7 cd A^?1. The overall performance of this device is competitive with the best reported solution‐processed blue PhOLEDs. Memory devices using ODCzMSi as an active layer exhibit non‐volatile write‐once read‐many‐times (WORM) characteristics with high stability in retention time up to 10⁴ s and a low switch on voltage. This switching behaviour is explained by different stable conformations of ODCzMSi with high or low conductivity states which are obtained under the action of electric field through a π–π stacking alignment of the pendant aromatic groups. These results with both PhOLEDs and memory devices demonstrate that this oligosiloxane–mCP hybrid structure is promising and versatile for high performance solution‐processed optoelectronic applications.     

内含C_(60)掺杂空穴传输层的量子点电致发光器件

聚乙烯咔唑(PVK)中掺入富勒烯(C60)的重量比从0%到10%变化,以研究在空穴传输层中掺杂C60后对量子点电致发光器件性能的影响。掺入C60后的PVK薄膜在氧化铟锡(ITO)基底上均方根粗糙度从3 nm降至1.6 nm。另外,掺入C60后有利于空穴的注入和传输,改善器件中电子和空穴的平衡,提高了器件的效率。     

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.     

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。     

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.     

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.