All-printed and highly stable organic resistive switching device based on graphene quantum dots and polyvinylpyrrolidone composite

We propose all printed and highly stable organic resistive switching device (ORSD) based on graphene quantum dots (G-QDs) and polyvinylpyrrolidone (PVP) composite for non-volatile memory applications. It is fabricated by sandwiching G-QDs/PVP composite between top and bottom silver (Ag) electrodes on a flexible substrate polyethylene terephthalate (PET) at ambient conditions through a cost effective and eco-friendly electro-hydrodynamic (EHD) technique. Thickness of the active layer is measured around 97 nm. The proposed ORSD is fabricated in a 3 × 3 crossbar array. It operates switching between high resistance state (HRS) and low resistance state (LRS) with OFF/ON ratio ∼14 for more than 500 endurance cycles, and retention time for more than 30 days. The switching voltage for set/reset of the devices is ±1.8 V and the bendability down to 8 mm diameter for 1000 cycles are tested. The elemental composition and surface morphology are characterized by XPS, FE-SEM, and microscope.     

Photo-Fenton removal of water-soluble polymers

This paper presents the results of experiments carried out in a laboratory-scale photochemical reactor on the photodegradation of different polymers in aqueous solutions by the photo-Fenton process. Solutions of three polymers, polyethyleneglicol (PEG), polyacrylamide (PAM), and polyvinylpyrrolidone (PVP), were tested under different conditions. The reaction progress was evaluated by sampling and analyzing the total organic carbon concentration in solution (TOC) along the reaction time. The behavior of the different polymers is discussed, based on the evolution of the TOC–time curves. Under specific reaction conditions, the formation and coalescence of solid particles was visually observed. Solids formation occurred simultaneously to a sharp decrease in the TOC of the liquid phase. This may be favorable for the treatment of industrial wastewater containing polymers, since the photodegradation process can be coupled with solid separation systems, which may reduce the treatment cost.     

Novel (Phenothiazinyl)Vinyl-Pyridinium Dyes and Their Potential Applications as Cellular Staining Agents

We report here the synthesis and structural characterization of novel cationic (phenothiazinyl)vinyl-pyridinium (PVP) dyes, together with optical (absorption/emission) properties and their potential applicability as fluorescent labels. Convective heating, ultrasound irradiation and mechanochemical synthesis were considered as alternative synthetic methodologies proficient for overcoming drawbacks such as long reaction time, nonsatisfactory yields or solvent requirements in the synthesis of novel dye (E)-1-(3-chloropropyl)-4-(2-(10-methyl-10H-phenothiazin-3-yl)vinyl)pyridin-1-ium bromide 3d and its N-alkyl-2-methylpyridinium precursor 1c. The trans geometry of the newly synthesized (E)-4-(2-(7-bromo-10-ethyl-10H-phenothiazin-3-yl)vinyl)-1-methylpyridin-1-ium iodide 3b and (E)-1-methyl-4-(2-(10-methyl-10H-phenothiazin-3-yl)vinyl)pyridin-1-ium tetrafluoroborate 3a′ was confirmed by single crystal X-ray diffraction. A negative solvatochromism of the dyes in polar solvents was highlighted by UV-Vis spectroscopy and explanatory insights were supported by molecular modeling which suggested a better stabilization of the lowest unoccupied molecular orbitals (LUMO). The photostability of the dye 3b was investigated by irradiation at 365 nm in different solvents, while the steady-state and time-resolved fluorescence properties of dye 3b and 3a′ in solid state were evaluated under one-photon excitation at 485 nm. The in vitro cytotoxicity of the new PVP dyes on B16-F10 melanoma cells was evaluated by WST-1 assay, while their intracellular localization was assessed by epi-fluorescence conventional microscopy imaging as well as one- and two-photon excited confocal fluorescence lifetime imaging microscopy (FLIM). PVP dyes displayed low cytotoxicity, good internalization inside melanoma cells and intense fluorescence emission inside the B16-F10 murine melanoma cells, making them suitable staining agents for imaging applications.     

Development of high‐definition aqueous polyvinylpyrrolidone photoresists for cathode ray tubes

Aqueous photoresists that are capable of higher resolutions than are currently employed by the cathode ray tube (CRT) industry were developed by combining photoactivators, which activate at shorter UV wavelengths with polyvinylpyrrolidone (PVP). Two photoactivators were synthesized: 4,4′‐diazido‐2,2′‐biphenyl disodium disulfonate (DABP), which has a maximum absorbance at 264 nm, and 4,4′‐diazido‐2,2′‐biphenylethane disodium disulfonate (DABPE), which has a maximum absorbance at 258 nm. The PVP/DABP and PVP/DABPE photoresists successfully imaged a pattern with resolution as small as 4.4 μm with photoactivator concentrations greater than 20% of the PVP concentration. Addition of silane and emulgen greatly improved the performance of the photoresists with more uniform coatings of thicknesses of up to 1.4 μm. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 102: 1637–1644, 2006     

聚乙烯吡咯烷酮在天然气水合物生成中的作用

研究了聚乙烯吡咯烷酮(PVP)在天然气水合物生成中的促进和抑制作用,结果表明PVP作为促进剂时,在确定的反应温度和压力下有一个最佳的浓度,在确定的使用浓度和温度时则有一个最佳反应压力,否则PVP的加入将抑制水合物的生成。认为PVP在低浓度时作为高分子表面活性剂,降低了溶液的表面张力,加速了水合物生成。在高浓度时,其长链上的五元环吸附水合物表面未完成的孔穴,阻止了水合物晶核的增长。     

氯化N-苄基-4-乙烯基吡啶聚合物的抗菌活性

氯化N-烷基-4-乙烯基吡啶聚合物,简称可溶性PVP,是一类具有高活性、低毒性和诸多潜在的特殊用途的季铵盐抗菌材料.本研究对聚-N-苄基乙烯基吡啶进行了合成与提纯,并对其在不同物理化学条件下抗菌性能差异进行了研究,结果表明温度、溶液条件等因素的变化对于样品的抗菌性能有重大影响.     

温度敏感性PVP/CHI共混水凝胶的制备与溶胀性能

制备了戊二醛交联的PVP/CHI共混水凝胶,讨论了CHI∶PVP(质量比)、引发剂用量、交联剂用量、反应温度等主要条件对凝胶溶胀性能的影响.温度敏感性实验表明,凝胶分别在33℃、37℃出现最大平衡溶胀率,即具有多重温度敏感性.随着PVP含量的升高,凝胶在33℃时对温度的敏感程度升高、37℃时对温度的敏感程度降低,交联度增加使凝胶的温度敏感程度降低.另外,PVP含量升高使CHI结晶度降低,进而使PVP/CHI凝胶的玻璃化转变温度Tg降低.     

TiO2/NiO复合纳米纤维制备及光催化性能研究

通过溶胶一凝胶过程,采用静电纺丝技术,以聚乙烯吡略烷酮(PVP,Mn=900 000)和钛酸正丁酯为前驱物,制备了PVP/Ti(OPr)./Ni(CH3COO)2复合一维纳米纤维材料.经控温缓慢氧化分解,在600℃的条件下成功制备了直径50～100 nmTiO2/NiO纳米纤维.采用扫描电镜、红外光谱、X射线粉末衍射、拉曼等分析手段对样品进行了表征,系统地介绍了TiO2光催化作用机理并在紫外灯下使用样品对罗丹明B溶液进行降解实验.结果显示,0.5%TiO2/NiO复合纳米纤维具有良好的光催化活性.     

生物降解型交联PVP材料的制备和性能

合成了一种具有双烯丙基的聚乙二醇和聚乳酸三嵌段共聚物(PLA-b-PEG-b-PLA)的生物可降解交联剂,并以偶氮二异丁氰(AIBN)为引发剂与N-乙烯基吡咯烷酮(NVP)交联制备了一种新型可降解交联膜材料.研究了丙交酯和PEG的投料比对交联剂粘度的影响和交联剂含量和分子量对膜材料的吸水率、接触角和力学强度的影响,初步研究了交联膜材料的降解性能.结果表明:随着丙交酯含量的增加,交联剂的特性粘度增加;随着交联剂含量的增加,膜材料的吸水率减小,接触角增大,拉伸模量增加,断裂伸长率先增加后减小;随着交联剂分子量的增加,膜材料的吸水率和接触角均有增加;对降解性能的研究表明,在降解初期膜材料的质量损失率线性地增加,在降解后期剧烈增加.     

Simultaneous extraction of source and drain resistances in top contact organic thin film transistors from a single test structure

A method of extraction of source and drain resistances in linear mode of operation from a single transistor is described. The proposed method can also be used to measure source resistance over the entire operating range from linear to saturation mode of operation. The method uses two floating probes outside the channel, one adjacent to the source and the other to the drain to sense the voltage under these contacts. Using transmission line analysis, the source and drain resistances are directly extracted from these measurements. 2D numerical simulation results confirm the validity of the proposed technique and sensitivity analysis shows that the method is more accurate than the conventional gated four probe technique, especially, when the source resistance is much smaller than the channel resistance. Experimental results obtained with Pentacene top-contact transistors are used to illustrate the proposed technique. Analysis of two devices with very different source resistance is carried out to highlight the ability of the proposed technique to offer insight into the different contributing factors. Current crowding under the source contact and accurate estimation of mobility without the distorting effects of source resistance are also described.