Preparation and Electrocatalytic Performance of Functionalized Copper‐Based Nanoparticles Supported on the Gold Surface

Copper nanoparticles (CuNPs) encapsulated by polymeric stabilizer of polyvinylpyrrolidone (PVP) (noted as PVP‐CuNPs) were simply prepared and used to construct an enzymeless glucose sensor on a solid substrate. Sensing and assay performance of the CuNPs‐based sensor to glucose were evaluated in detail. Cyclic voltammetry (CV), chronoamperometry (I–t) and flow injection amperometry (FIA) revealed a high sensitivity, excellent stability, and good reproducibility in the glucose determination at +0.45 V, which was 200 mV more negative than those in former reports. A detection limit as low as 1.0×10^?8 M (signal‐to‐noise=3) and a linear range of 1.0×10^?7 M to 5.0×10^?3 M were obtained in this study.     

Synthesis of sub-micro-sized solid alpha alumina fibers with smooth surfaces by sol–gel method

Alumina sol containing nano-meter sized Al₂O₃ particles were synthesized using aluminum sec-butoxide and nitric acid as precursor and peptizing agent, respectively. Polyvinylpyrrolidone (PVP) was added to prevent particle growth and adjust sol viscosity. PVP/alumina hybrid fibers were drawn from the sol with a viscosity value in the range of 2,500–3,000 mPa.s. By guided through a temperature gradient tube furnace at a rate of 4 m/min, the wet PVP/alumina hybrid fibers were sufficiently dried. Sub-micro-sized pure alpha alumina fibers were obtained by sintering the dry hybrid fibers at 1,000 °C for 3 h. The organic matters were decomposed within a wide temperature range from 150 to 800 °C allowing the nano Al₂O₃ particles to gradually get together and form solid alumina fibers with smooth surfaces.     

Simultaneous Electrochemical Determination of Hydroquinone and Bisphenol A using a Carbon Paste Electrode Modified with Silver Nanoparticles

In this paper, a rapid and sensitive modified electrode for the simultaneous determination of hydroquinone (HQ) and bisphenol A (BPA) is proposed. The simultaneous determination of these two compounds is extremely important since they can coexist in the same sample and are very harmful to plants, animals and the environment in general. A carbon paste electrode (CPE) was modified with silver nanoparticles (nAg) and polyvinylpyrrolidone (PVP). The PVP was used as a reducing and stabilizing agent of nAg from silver nitrate in aqueous media. The nAg‐PVP composite obtained was characterized by transmission electron microscopy and UV‐vis spectroscopy. The electrochemical behavior of HQ and BPA at the nAg‐PVP/CPE was investigated in 0.1 mol L⁻¹ B−R buffer (pH 6.0) using cyclic voltammetry (CV) and square wave voltammetry (SWV). The results indicate that the electrochemical responses are improved significantly with the use of the modified electrode. The calibration curves obtained by SWV, under the optimized conditions, showed linear ranges of 0.09–2.00 μmol L⁻¹ for HQ (limit of detection 0.088 μmol L⁻¹) and 0.04–1.00 μmol L⁻¹ for BPA (limit of detection 0.025 μmol L⁻¹). The modified electrode was successfully applied in the analysis of water samples and the results were comparable to those obtained using UV‐vis spectroscopy.     

Laser-induced silver nanocrystal formation in polyvinylpyrrolidone solutions

We report unusual laser-induced shape conversions of silver nanoparticles dispersed in polyvinylpyrrolidone (PVP) aqueous solutions. Silver nanocrystals such as nanoplates and nanorods were formed using laser irradiation for colloidal silver nanoparticles prepared using laser ablation in aqueous solutions of PVP. Differing from the nanocrystal formation observed in neat water and halide solutions, which were induced by weak laser or fluorescent-light irradiation, the nanocrystal formation in PVP solutions was induced by strong laser irradiation. On the other hand, nanocrystal formation was not observed in polyvinylalcohol (PVA) solutions, in which fusion of nanoparticles were prominent. It is proposed that the nanocrystals were formed from fragmented nanoparticles protected by PVP via a ripening process.     

Studies of pectin/polyvinylpyrrolidone blends exposed to ultraviolet radiation

The new biodegradable blends composed of natural pectin and synthetic polymer: polyvinylpyrrolidone were obtained by casting from aqueous solutions. The molecular interactions between components have been studied by FTIR. The blends were exposed to UV-irradiation and the changes in chemical structure were investigated using absorption spectroscopy (FTIR and UV-Vis). The morphology of sample surfaces before and after exposure to UV was observed by atomic force microscopy. Insoluble gel, formed as a result of photocrosslinking, was appointed gravimetrically. The relation between the blend composition and the efficiency of observed photoreactions has been considered.     

Synthesis and performance of Li_4Ti_5O_(12) anode materials using the PVP-assisted combustion method

Li_4Ti_5O_(12) was synthesized by a facile gel-combustion method(GCM) with polyvinylpyrrolidone(PVP) as the polymer chelating agent and fuel.The structural and electrochemical properties of the sample were compared with the one prepared by the conventional solid-state reaction(SSR) through X-ray diffraction(XRD),scanning electron microscopy(SEM),cyclic voltammetry(CV),charge-discharge measurements,and electrochemical impedance spectroscopy(EIS),respectively.The sub-microscale Li_4Ti_5O_(12) oxides,with a high phase purity and good stoichiometry,can be obtained by annealing at 800 C.The grain size is smaller than that of the samples that were power prepared by SSR.Lithium-ion batteries with a GCM Li_4Ti_5O_(12) anode exhibit excellent reversible capacities of 167.6,160.7,152.9,and 144.2 mAh/g,at the current densities of 0.5 C,1 C,3 C and 5 C,respectively.The excellent cycling and rate performance can be attributed to the smaller particle size,lower charge-transfer resistance and larger lithium ion diffusion coefficient.It is therefore concluded that GCM Li_4Ti_5O_(12) is a promising candidate for applications in highrate lithium ion batteries.     

PVP/HEC分子间缔合作用机理探讨

通过粘度、紫外光谱、红外光谱和DSC谱的测定 ,探讨了PVP/HEC分子间的缔合机理 .结果表明 ,PVP/HEC复合体系相对于单一体系产生了粘度的负协同效应 ,NaCl的加入使单一体系和复合体系的粘度均下降 ;在紫外可见吸收光谱中 ,PVP/HEC复合体系的最大吸收波长λmax相对于PVP、HEC各自的λmax都发生红移 ;PVP/HEC复合物的红外光谱在 2 370cm-1出现新的吸收峰 ;DSC谱中复合物的峰温高于简单混合物 ,而其焓变低于简单混合物 ,这一切均证明HEC与PVP之间未发生疏水缔合 ,而是HEC的羟基与PVP的羰基之间通过氢键缔合成复合物 ,复合物的分子链排列较为紧密 .     

PVP修饰脂质体的形貌及力学特性

制备了聚乙烯吡咯烷酮(Polyvinylpyrrolidone, PVP)修饰的脂质体, 采用激光粒度仪检测了脂质体的粒径分布, 采用原子力显微镜及力曲线测量技术研究了脂质体的形貌变化和纳米力学特性. 实验数据表明, 与未修饰的脂质体囊泡相比, 经PVP修饰后脂质体囊泡之间聚集的程度明显降低, 形状更为规则, 在云母表面更加稳定. 力曲线实验中针尖接近脂质体过程的弹性力和撤离过程中的黏附力数值变大, 且针尖与样品间的静电作用引起的滞留现象消除. 实验表明, PVP修饰脂质体能提高其在体内环境的稳定性, 降低被免疫系统吞噬的数量, 极大地提高脂质体的功效.     

Controlling growth of ZnO rods by polyvinylpyrrolidone (PVP) and their optical properties

ZnO rods with different morphologies were synthesized through a wet chemical method by addition of polyvinylpyrrolidone (PVP). By adjusting the concentration of the additive in the growth solution, we can control the diameter, ratio of length to diameter and density of ZnO rods. FESEM images showed that the rods in nanoscale could be obtained at the polyvinylpyrrolidone concentration of 1.0 mM. Meanwhile, the resonant Raman scattering and photoluminescence spectra showed that the crystalline quality and the optical property of ZnO rods were improved through moderate addition of polyvinylpyrrolidone (concentration of 1.0 mM) in the growth solution. In addition, the possible mechanism of the PVP effect on the growth of ZnO rods was discussed based on the FT-IR spectra.     

Encapsulation of nabumetone by means of -drug: (β-cyclodextrin)2:polyvinylpyrrolidone ternary complex formation

The aim of the present study was to investigate the effect of the presence of the water-soluble polymer polyvinylpyrrolidone (PVP) MW=24,000 g/mol, on the complexing of the anti-inflammatory drug nabumetone, with β-cyclodextrin (β-CD). The data show that the polymer interacts with the free nabumetone and with the nabumetone:β-CD inclusion complex, in both cases with a stoichiometry of 1:1. The interaction constants are 1.3×10⁴ M⁻¹ and 1.6×10⁴ M⁻¹, respectively.The presence of PVP, changes the drug:cyclodextrin interaction, a nabumetone:(β-CD)₂:PVP complex being formed.In addition, the presence of PVP, produces a strong increase in the global binding constant, β₂=(22.12±0.22)×10⁶ M⁻² at 1% PVP.In the ternary complex, the nabumetone is wrapped at both ends for the β-CD. In this complex the polymer seems to act as a bridge between both β-CD molecules that bind the nabumetone.