Synthesis of anisotropic gold nanoparticles in a water-soluble polymer

Anisotropic gold nanoparticles have been synthesized by a UV irradiation technique through the interaction of HAuCl₄ and a stabilizing agent, poly (vinyl pyrrolidone) (PVP). The effect of irradiation time on the size and shape of gold nanoparticles was investigated by UV-visible spectroscopy and Transmission Electron Microscopy (TEM). The absorption spectra of all samples show a broad band with the characteristic surface plasmon resonance (SPR) peak visible at around 530 nm. The presence of an additional low intensity absorption peak at a longer wavelength suggests the presence of non-spherical nanoparticles. The TEM measurements show evidence of particle shapes such as spheres, hexagons, decahedrons and truncated triangles as the reaction proceeded from 5 min to 24 h. The variation in particle shape is probably due to the effect of the reduced gold to PVP ratio as the reaction proceeds.     

Electrical conduction mechanism in solution grown doped polyvinyl pyrrolidone films

A detailed study of electrical conduction mechanism in bimetallized ferrocene-doped polyvinyl pyrrolidone films was carried out. The measurements were carried out on films of about 20 μm thick, in the field range of (2.0–8.0) x 10⁴ V/cm at temperatures ranging from 363 to 423 K. An investigation of the effect of impurity such as ferrocene in the polymer matrix was undertaken. Lowering of activation energy and increase in current due to doping were observed. The results showed that the charge carriers were generated by field-assisted lowering of coulombic barriers at the traps and were conducted through the bulk of the material by a hopping process between the localized states by a Jonscher-Ansari modified Poole-Frenkel mechanism. The dependence of current and activation energy on the ferrocene concentration is explained on the basis of charge transfer type of interaction between dopant and polymeric material.     

液相还原法制取纳米银粉的研究

以硝酸银为原料,水为反应介质,聚乙烯吡咯烷酮为保护剂,甲酸铵作为还原剂,利用普通液相还原法常温一步直接制备得到平均粒径在10nm左右的纳米级银粉。采用XRD、EDS、TEM等测试手段,对所制得的纳米银粉进行了表征。并简要讨论了纳米银粉制备过程中的各类影响因素。     

Radiation synthesis of PVP/CMC hydrogels as wound dressing

Carboxymethyl cellulose (CMC) and poly(N-vinyl pyrrolidone) (PVP) were blended to synthesize hydrogels by ⁶⁰Co γ-ray irradiation. A series of hydrogels were prepared with three compositions, i.e. PVP:CMC = 5:5, 6:4 and 7:3. The properties of the hydrogels such as gel fraction, gel strength, swelling behavior and moisture retention were investigated. Compared with pure PVP and CMC hydrogels, PVP/CMC blend hydrogels possessed improved gel strength, flexibility and transparency. As the content of PVP in PVP/CMC blend hydrogels increased, the gel fraction increased while the swelling rate decreased. The hydrogels with optimal properties were obtained in a composition of PVP/CMC = 6/4 with sterilization dose (25 kGy) and further characterized by FT-IR and SEM. Properties concerning the application of wound dressing were performed by comparison with a commercial hydrogel wound dressing to find a similar moisture retention capability and improved swelling rate. The improved properties as well as the cheapness of the materials suggest that PVP/CMC blend hydrogel can be good candidate as wound dressing.     

N-甲基吡咯烷酮热管启动性能和等温性能实验研究

复现锡凝固点的中温热管固定点炉,需要选择合适工质的中温热管。研制了2根以N-甲基吡咯烷酮(NMP)为工质的重力热管(1#,2#),并在同等定温加热条件下对其启动特性和等温特性进行实验研究。结果表明:2#热管启动时间快于1#热管,且启动后稳定性优于1#热管;初步证实NMP热管在170~320℃温度范围内可运行;此外,制作工艺可影响热管的启动特性和等温特性,在相同的运行条件下,热管制作工艺越合理,热管冷凝段上部温度相对越高。     

聚乙烯吡咯烷酮对酸诱导液相沉积体系中GeO_2颗粒形貌的影响

在室温下,通过酸诱导液相沉积的方法,制备出了二氧化锗(GeO2)颗粒。制得的GeO2颗粒通过扫描电子显微镜(SEM),透射电子显微镜(TEM)和X射线衍射(XRD)进行表征。实验结果表明,向前驱液中加入酸,可以诱导锗酸根离子转化成立方体型的GeO2颗粒析出。而向反应液中再加入少量的聚乙烯吡咯烷酮(PVP)后,会析出纺锤体型的GeO2晶体颗粒。     

Preparation of sorbitol-based polyurethanes and their semiinterpenetrating polymer networks

Sorbitol is a useful agro-based substance that is inexpensive and commercially available. In the interest of adding value to bio-based raw materials, we have synthesized polyurethanes from sorbitol and toluene-2,4-diisocyanate (TDI) through both conventional heat and microwave processes. Relative to conventional heat, the microwave process achieved the same reaction at a faster rate, thereby saving time and energy. The nature of the resulting polyurethane products depended on the stoichiometry of the reaction. At increasing TDI levels, a viscous liquid, a soft gel, or a hard thermoset could be obtained. The polymers were fully characterized with ¹³C-NMR, Fourier transform infrared, size exclusion chromatography, and thermogravimetric analysis. The polyurethanes obtained near the gel point could be used to make semiinterpenetrating polymer networks (semi-IPNs) with a second polymer, thereby imparting some of the properties of the second polymer onto the sorbitol-based polyurethane. For illustration, the sorbitol-based polyurethane semi-IPNs were made in combination with poly(vinyl pyrrolidone) and poly(lactic acid). © 2019 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2019 , 136, 47602.     

PVP及其共聚物的残量NVP单体的气相色谱测定法

研究了聚乙烯吡咯烷酮 ( PVP)及其共聚物残量的乙烯基吡咯烷酮 ( NVP)单体气相色谱分析方法。使用 2 0 %聚二乙二醇丁二酸酯 /硅烷化 1 0 2白色担体填充色谱柱 ,选出了最佳的色谱分析条件。该方法有较好的精密度和准确度 ,并且分析速度快。可用于定量分析 PVP产品以及有关NVP聚合反应中的残量 NVP单体     

PVP表面修饰不同形貌金银纳米粒子研究现状

聚乙烯吡咯烷酮(PVP)是一种重要的工业化大分子表面活性剂,由于其大分子结构的特殊性及生物适应性,使得PVP在制备金属纳米粒子过程中得到了广泛应用。近年来,有大量关于以PVP为大分子表面修饰剂制备不同形貌金属纳米粒子的文献报道。文中综述了以PVP为表面修饰剂,分别以乙二醇、乙醇、N,N-二甲基甲酰胺及水为溶剂,通过溶剂和PVP自身的还原作用,在不同反应条件下制备不同形貌金、银纳米粒子的研究现状,提出了不同溶剂体系中不同形貌金属纳米粒子的形成机理研究是未来该领域要解决的主要问题。