Presence Of PVP Research Articles

Graft copolymerization of N-vinyl-2-pyrrolidone onto pre-irradiated poly(vinylidene fluoride) powder

Graft copolymerization of N-vinyl-2-pyrrolidone (NVP) onto 60Co γ-ray pre-irradiated poly (vinylidene fluoride) (PVDF) powder was investigated to find out the relationship between the degree of grafting (DG) and various factors, including monomer concentration, irradiation dose, reaction time, catalyst and so on. The DG can be calculated by comparing the amount of nitrogen element in the resulting copolymer (PVDF-g-PVP) powder with that in PVP on the basis of element analysis. The presence of PVP in the resulting PVDF powder was confirmed by the comparative studies of pristine PVDF and grafted PVDF powder through Fourier transform infrared (FTIR) spectroscopy, nuclear magnetic resonance (NMR), X-ray photoelectron spectroscopy (XPS), thermo gravimetric analyzer (TGA) and differential scanning calorimetry (DSC), respectively. When the reaction was performed at the monomer concentration of 20% (vol.) and the absorbed dose of 40kGy for 3h in water, the max. DG of 17.7% was obtained.

Microwave-assisted synthesis of silver nanoprisms/nanoplates using a “modified polyol process”

In this paper, we report a novel, efficient and versatile process to produce high concentrations of silver nanoprisms, while controlling their size (prism height) and size dispersity, using a “modified polyol process” (microwave-assisted process). If the formation of silver spherical particles, nanocubes or nanowires has already been reported using the classical polyol process (reduction of AgNO 3 by ethylene glycol and in presence of PVP), here we show that the production of silver nanoprisms/nanoplates is possible by a careful choice in the process parameters and in particular in the reducing agent (ethylene glycol should be replaced by a reducing agent containing only one hydroxyl reducing group such as ethylene glycol monoalkyl ethers). The synthesis, characterization, the influence of parameters and the mechanism of formation are discussed in order to correlate the operational conditions with the shape and the dimension of the nanoparticles.

SHAPE-CONTROLLED SYNTHESIS OF RUTHENIUM NANOPARTICLES

Uniform pompon-like Ru nanoparticles with an average diameter of 148 nm were readily synthesized by reducing RuCl 3 with triethylene glycol (TG) as both a reducing agent and a solvent in the presence of PVP by oil-bath heating at 170°C for 6 h. The as-prepared Ru nano-pompons were characterized by TEM, XRD, XPS and UV-vis absorption spectroscopy. The effects of some parameters such as the average molecular weight and the concentration of PVP on the synthesis of Ru nano-pompons were investigated.

PVP Addition during Hydroxyapatite Synthesis: Effect on Albumin Adsorption

Hydroxyapatite nanoparticles were synthesized by preparing an aqueous solution comprising 0.5M Ca(OH)2, 0.3M H3PO4 and 1M CH3CHCO2HOH (lactic acid) at pH of 3.7. KOH was added to the solution until pH=12 was reached, to precipitate hydroxyapatite. The incubation time ranged from 24 to 88 hours and the precipitates were then filtered on filter paper with the aid of a vacuum pump. The powders were synthesized with and without PVP addition. The powders were then sintered at 1100°C. Sintered and non sintered powders were characterized by scanning electron microscopy with field emission gun (FEG-SEM) and transmission electron microscopy (TEM) in order to assess particles morphology. Structural characterization was performed by X-ray diffractometry with Rietveld refinement. Albumin adsorption experiments were carried out on the powders with the aid of UV-VIS spectrometry. The results showed that the samples produced in the presence of PVP showed smaller particles when compared to non-dispersed samples. Albumin adsorption was more effective on the powders synthesized with dispersant.

Application of silver nanoparticles and principal component-artificial neural network models for simultaneous determination of levodopa and benserazide hydrochloride by a kinetic spectrophotometric method

A multicomponent analysis method based on principal component analysis-artificial neural network model (PC-ANN) is proposed for the simultaneous determination of levodopa (LD) and benserazide hydrochloride (BH). The method is based on the reaction of levodopa and benserazide hydrochloride with silver nitrate as an oxidizing agent in the presence of PVP and formation of silver nanoparticles. The reaction monitored at analytical wavelength 440 nm related to surface plasmon resonance band of silver nanoparticles. Differences in the kinetic behavior of the levodopa and benserazide hydrochloride were exploited by using principal component analysis, an artificial neural network (PC-ANN) to resolve concentration of analytes in their mixture. After reducing the number of kinetic data using principal component analysis, an artificial neural network consisting of three layers of nodes was trained by applying a back-propagation learning rule. The optimized ANN allows the simultaneous determination of analytes in mixtures with relative standard errors of prediction in the region of 4.5 and 6.3 for levodopa and benserazide hydrochloride respectively. The results show that this method is an efficient method for prediction of these analytes.

Template Preparation of Poly(Vinylpyrrolidone-Itaconic Acid) and Their Application in Removal of Copper Ions

Poly(vinyl pyrrolidone-itaconic acid) P(VP-IA) was prepared by the template polymerization of itaconic acid (IA) in the presence of PVP as a template polymer using gamma rays. Fourier transform infrared results showed that the interpolymer complexes were formed by hydrogen bonds between the carboxyl groups of PIA and the carbonyl groups of PVP. P(VP-IA) resin could be employed as a potential adsorbent for the removal of heavy metals such as Cu(II). The capacity of the prepared polymer containing different amounts of PVP, N,N′-methylene-bis-acrylamide (NMBA) and IA concentration was investigated. It is obvious that the adsorption capacity increased with increasing itaconic acid content. Although it decreased with increasing the concentration of PVP and NMBA. P(VP-IA) was found to be a potential adsorbent for removal of copper from aqueous medium. Detail adsorption study of Cu(II) on P(VP-IA) was investigated. Batch adsorption study was carried out as a function of contact time, adsorbent dose, and pH. Adsorption isotherms of Cu(II) on adsorbents were determined and correlated with common isotherm equations such as Langmuir, Freundlich and Tempkin adsorption isotherm models. The maximum adsorption capacities for Cu(II) on P(VP-IA) were found to be 131 mg g−1.

Preparation of nanoparticles with a semi-batch gas–liquid membrane contactor

Nanosized calcium carbonate particles were prepared with a semi-batch gas–liquid membrane contactor. A mathematical model of the semi-batch operated contactor was given, and the effects of Ca(OH) 2 concentration, CO 2 partial pressure and additives on the absorption rate were estimated theoretically. The predicted data were consistent with the experimental results. The Ca(OH) 2 concentration and CO 2 pressure have no apparent effects on the particles. In the presence of PVP and PEG, the particles are well-dispersed and the size is effectively reduced. After reaction, the membranes were washed with dilute hydrochloric acid and the membranes can be reused for at least 9 times without apparent performance deterioration.

Poly(vinyl pyrrolidone)-enhanced crossflow filtration of Fe(III), Cu(II) and Cd(II) ions using alginic acid/cellulose composite membranes

Removal of Fe(III), Cu(II) and Cd(II) ions from aqueous solutions was studied by polymer-enhanced crossflow filtration. Poly(vinyl pyrrolidone) (PVP) was used as complexing agent to enhance the retention. Alginic acid (AA)/cellulose composite membranes were used in the separation. The effects of AA content of the membranes and pH of the solution on the retention efficiency and the permeate flux were examined. Maximum retention efficiency was found as 93% for 1×10–4 M Fe(III) solutions at a flow velocity of 100 mL/min, pH of 3.0, pressure of 10 kPa in the presence of PVP by using 0.50 (w/v)% AA/cellulose composite membranes whereas for 1×10–4 M Cu(II) and Cd(II) solutions the maximum retention efficiencies were found as 98% and 81% respectively at pH 7.0.

The influence of polyvinylpyrrolidone on the solution and bioavailability of hydrochlorothiazide.

The dissolution properties of hydrochlorothiazide-PVP 10 000 mechanical mix and coprecipitate systems were qualitatively similar to those previously reported using hydroflumethiazide. Quantitative differences were dependent on the proportion of PVP present, its molecular weight and method of incorporation. Cumulative urinary excretion data from test capsule preparations showed that bioavailability was enhanced by the presence of PVP. However, the degree of enhancement was less than that expected from constant surface area disc rate studies. Dissolution tests on the capsule formulations, using the U.S.P. basket stirrer assembly, did not correlate with in vivo results. Using the Levy beaker method and a stirring speed of 40 rev min-1, good correlation between amount dissolved in 30 min and amount excreted in urine after 24 h was obtained. The dissolution tests revealed that PVP retards the initial dissolution from capsule dosage forms, probably by retarding deaggregation and dispersion of drug particles.

A Facile Route to Synthesize Gold Prisms Up to Micrometer Scale Based on Slow Reduction Methods

Gold prisms with edge length ranges from nanometer to micrometer scale were prepared in large quantities through facile liquid-liquid interfacial reaction and solution-phase reactions. The technological keys to synthesis of gold microprisms are (i) selecting poly(N-vinylpyrrolidone) (PVP) as the shape-directing agent to induce the preferential growth of nanoprism seeds and (ii) using weak reducing agents to lower the reduction rate of gold ions so that gold ions were reduced slowly onto the surface of the growing nanoprisms. Thus, the reduction of ions in the presence of PVP by some weak reducing agents generated a large number of gold microprisms (as defined by edge length of prisms). On the contrary, the relatively fast reduction of ions could only lead to formation of spherical gold particles.

Polymer-assisted preparation of metal nanoparticles with controlled size and morphology

We describe here a one-step synthesis of hybrid metal nanoparticles (MNPs) and polymer composites on glass substrates using poly(vinyl pyrrolidone) (PVP) as both the reducing agent and polymer matrix. With this method, it takes only one minute to produce a nanocomposite thin film that contains MNPs with controlled size and morphology. The size and morphology of gold nanoparticles can be manipulated by simply modulating the ratio between the PVP and the Au precursor, while the nearly monodispersed spherical silver nanoparticles are insensitive to the reaction conditions, which is believed to result from a better control over the crystal structure of the Ag seeds than that of the Au seeds in the presence of PVP. Moreover, the resulting MNP–polymer composites are high-quality thin films with tunable optical properties—the λmax of absorption spectra changes from 480 nm to greater than 580 nm (from blue to red color). This environmentally friendly synthetic technique may open up a new avenue for facile nanomaterial synthesis that is not accessible by conventional solution chemistry.

Monodispersed platinum nanocubes for enhanced electrocatalytic properties in alcohol electrooxidation

We report Pt nanocubes of ∼4.5 nm in size synthesized by thermal decomposition in the presence of PVP. The Pt cubic electrocatalysts with dominantly exposed {100} facets show much improved electrocatalytic activities in methanol, ethanol and formic acid electrooxidation.

Crystallization of aragonite CaCO 3 with complex structures

In this work, aragonite CaCO 3 with complex morphologies was synthesized through homogeneous precipitation, in which calcium acetate and urea precipitated at 90 °C in the presence of PVP. The effect of the concentration of urea and PVP on the CaCO 3 crystalline was investigated. The morphology and structure of the CaCO 3 particles were characterized by SEM, XRD, and FT-IR. It was found that the concentrations of urea and PVP in the mixed aqueous solution were turned out to be important parameters for the morphology of CaCO 3 particles. All CaCO 3 particles were mainly aragonite with morphology from bundles of rods, bouquet-like and dumbbell-like. And there was no phase transition under the research conditions. Moreover, the possible process for the formation of the morphology of aragonite was discussed.

Role of poly(N-vinyl-2-pyrrolidone) as stabilizer for dispersion of graphene via hydrophobic interaction

Stable aqueous dispersion of chemically reduced graphene is simply obtained by reducing GO solution in the presence of PVP. Prepared aqueous graphene dispersion was optically clear and stable for several months without any aggregation or precipitation. Graphene/PVP assembly shows decreased optical transmittance (47% at 600 nm) and quenching of photoluminescence of parent GO (8.5% at 375 nm) after reduction. Raman analysis confirms that reduction of GO to graphene is efficient in the presence of PVP. Both DLS and AFM analysis confirm that there is efficient and overall interaction between chemically reduced graphene plates and PVP chains. Hydrophobic interaction between graphene and PVP might be responsible for this solubilization of chemically reduced graphene in solution.

Hydrogen generation from the methanolysis of ammonia borane catalyzed by in situ generated, polymer stabilized ruthenium(0) nanoclusters

Addressed herein is the detailed study on in situ generation of poly(N-vinyl-2-pyrrolidone) (PVP) stabilized ruthenium(0) nanoclusters and their catalysis in the methanolysis of ammonia borane (AB). PVP-stabilized ruthenium(0) nanoclusters with an average particle size of 2.4 ± 1.2 nm were generated in situ from the reduction of ruthenium(III) chloride during the methanolysis of AB in the presence of PVP at room temperature. The nanoclusters were characterized by UV–vis spectroscopy, TEM, XRD, XPS and FT-IR techniques. PVP stabilized ruthenium(0) nanoclusters are highly active and stable catalyst in hydrogen generation from the methanolysis of AB with a turnover frequency (TOF) value of 4017 h −1 and 71,500 turnovers over 25 h. Mercury poisoning experiments showed that the PVP-stabilized ruthenium(0) nanoclusters are the true heterogeneous catalyst in the methanolysis of AB. The report also includes the results of a detailed kinetic study on the hydrogen generation from the methanolysis of AB catalyzed by PVP stabilized ruthenium(0) nanoclusters investigating the effect of the catalyst concentration, substrate concentration, and temperature as well as the activation parameters of catalytic methanolysis of AB calculated from the kinetic data.

One Step Synthesis of the Smallest Photoluminescent and Paramagnetic PVP-Protected Gold Atomic Clusters

Gold atomic clusters of only two and three atoms were prepared by a simple electrochemical technique based on the anodic dissolution of a gold electrode in the presence of PVP, and subsequent electroreduction of the Au-PVP complexes. These clusters show stable photoluminescent and magnetic properties, which make them the smallest and most elemental gold (0) building blocks in nature (after atoms) bringing new possibilities to construct novel nano/microstructures with large potential interest in biomedicine, catalysis, and so forth.

Facile synthesis of hollow nano-spheres and hemispheres of cobalt by polyol reduction

The hydrophilic hollow nano-spheres and hemispheres of Co are synthesized via ethyleneglycol reduction of cobalt acetate in the presence of PVP and Pd nano-particle seeds. Thedimensions of the hollow core can be tuned from 100 to 300 nm by controllingthe amount of Pd nano-particle seeds. The morphology of the hollow materialsstrongly depends on the molar ratio of the amide unit in PVP over Co and theMw of PVP. The hollow structure is formed when the ratio falls in the range 1–1.5 and theMw is over 40 000. Based on the experimental data, a possible formation mechanism of Cohollow spheres is proposed.

Preparation of silver nanoparticles using tryptophan and its formation mechanism

A non-toxic route was used for the preparation of silver nanoparticles using tryptophan (Trp) as reducing/stabilizing agent in the presence of cetyltrimethyl ammonium bromide (CTAB). Role of water soluble neutral polymer poly(vinylpyrrolidone) (PVP) has been studied on the growth of yellow colour silver nanoparticle formation. The synthesized nanostructures were characterized by UV–Visible absorption spectroscopy, transmission electron microscopy (TEM) by observing the size and distribution of silver nanoparticles. As the reaction proceeded, particles grew up to about 10 and 20 nm in the presence and absence of PVP, respectively, as determined by TEM. The formed nanoparticles showed the highest absorption plasmon band at 425 nm. Rate of silver sol formation increases with the [Trp], [CTAB] and [PVP], reaching a limiting value and then decreases with the increase in concentrations of these reagents. It was observed that nanoparticles are spherical, aggregated and poly dispersed in the absence and presence of PVP, respectively. On the basis of kinetic data, a suitable mechanism is proposed and discussed for the silver sol formation.

Use of xanthan and its binary blends with synthetic polymers to design controlled release formulations of buccoadhesive nystatin tablets

Various buccoadhesive nystatin tablets formulations containing xanthan, carbopols (934P, 971P, 974P), PVP K30 or PEG 6000 or their binary blends were prepared. The powders were compressed into tablets at a constant compression pressure. Drug release behaviour, swelling and erosion indices and strength of bioadhesion in vitro to a biological membrane were investigated. The interaction between nystatin and polymers was investigated by DSC and FT-IR. Tablets containing the different types of carbopol alone consistently showed an initial burst release of drug, whereas this was not observed for matrices containing xanthan or xanthan-carbopol. The presence of PEG in xanthan-containing formulations induced an increase in dissolution rate; however, in the absence of xanthan the amount of drug release from a PEG matrix was reduced to < 15% over 8 h dissolution. The presence of PVP increased the dissolution rate of nystatin due to the relative hydrophilicity of PVP. The presence of calcium ions induced a more rigid gel in the xanthan matrix as a result of interaction between the polymer and calcium ions. Xanthan can be used in potential mucoadhesive formulations containing nystatin to produce a controlled release of the drug and the outcomes of this work may provide a suitable strategy for matrix selection to provide more efficacious treatment alternatives for candidiasis and other disease processes for significant patient populations.

Growth Factors for Silver Nanoplates Formed in a Simple Solvothermal Process

We synthesized both big and ultra-small silver nanoplates through a simple solvothermal process in a common autoclave. Using this approach, we achieved the reduction of silver nitrate in DMF or ethanol in the presence of PVP as a capping agent. The reduction capacity of PVP was also investigated. Growth factors such as the concentration of silver precursor, quantity of capping agent, reaction time, and temperature have been shown to play important roles in the formation of different sizes and shapes of silver nanoplates. The big plates, over 100 nm in edge length, were found mainly in the shape of a connected triangular. Single triangle plates, truncated triangular plates, and hexangular plates were also found under different reaction conditions. The ultra-small silver nanoplates, 20-100 nm in edge length, were successfully extracted from the solution under different centrifugation conditions. The UV-vis spectrum exhibited intense in-plane dipole absorption peaks varying from 470-630 nm, as reflected by the gradual color change of the solution from orange to red, and finally to blue.