Weight Of Polyvinylpyrrolidone Research Articles

Synthesis, characterization and evaluation of copper nanoparticles as agrochemicals against Phytophthora spp.

By using water as a solvent, copper nanoparticles (CuNPs) have been synthesized from copper sulfate via chemical reduction method in the presence of trisodium citrate dispersant and polyvinylpyrrolidone (PVP) as capping agent. The effects of the experimental parameters such as the concentration of reducing agent (NaBH4), reaction temperature, molar ratio of citrate/Cu2+ and weight percentage ratios of Cu2+/PVP on the CuNP sizes were studied. The size of CuNPs in a range of 31 nm was obtained at NaBH4 concentration of 0.2 M, 50oC, citrate/Cu2+ molar ratio of 1.0 and Cu2+/PVP weight percentage of 5%. The colloidal CuNPs were characterized by using UV–Visible spectroscopy, transmission electron microscopy (TEM), and X-ray diffraction (XRD) techniques. The colloidal solution of CuNPs (3±1 nm) was investigated the potential against Phytophthora spp. which cause economically crop diseases. Under in vitro test conditions, the inhibition of Phytophthora spp. mycelia growth at three concentrations of CuNPs (10, 20, 30 ppm) after 48 hours are 90.18%, 91.87% and 100%, respectively. These results provided a simple and economical method to develop the CuNPs-based-fungicide.

Preparation of Ag NWs and Ag NWs@PDMS stretchable sensors based on rapid polyol method and semi-dry process

The silver nanowires (Ag NWs) prepared by improved polyol method in 30min were applied to the stretchable strain sensors. Three factors affecting the morphology of Ag NWs were discussed, including reaction temperature, molecular weight of PVP, ratio of silver nitrate (AgNO3) and polyvinyl pyrrolidone (PVP). Experimental results showed that Ag NWs with diameter of 53 ± 9 nm, length of 31 ± 7 μm and the aspect ratio is 584.9 were obtained under the optimum conditions. Thus, a new and convenient method was proposed to fabricate flexible stretchable sensors by embed Ag NWs into Polydimethylsiloxane (PDMS). The stability, hysteresis, and sensitivity of the Ag NWs@PDMS strain sensors were evaluated by cyclic stretch-release test. Our strain sensor with good stability, higher sensitivity (the gauge factor is 4.11) and good repeatability could be stretched 10% continuously for about 200 cycles. Ag NWs@PDMS flexible sensors can be used in wearable devices to monitor human movements.

Proton transport and dielectric properties of high molecular weight polyvinylpyrrolidone (PVPK90) based solid polymer electrolytes for portable electrochemical devices

A simple solution cast route was used to prepare proton conducting solid polymer electrolytes using poly(methyl methacrylate) and poly(vinylpyrrolidone) as polymer hosts and methanesulfonic acid as a proton provider. Fourier transform infrared spectra confirmed functional group interactions between polymers, blended polymers, and acid. Polymer glass transition temperature shifted with increasing acid content in the blend electrolytes provide thermal stability up to 290 °C, verified by differential scanning calorimetry and thermogravimetry analyses. Proton conductivity achieved = 1.16 × 10−4 S/cm at room temperature with an ionic transport number of 0.98. Discharge profiles verified oxidation current < 10 μA for 2 V applied potential for the highly conductive electrolyte, confirming the prepared electrolytes as prime candidates for primary proton cells.

The effect of polyvinylpyrrolidone nanowires on the metabolic activity of Lactobacillus acidophilus

The effectiveness of the use of polyvinylpyrrolidone (PVP) nanowires for increasing the metabolic activity of probiotic cultures of Lactobacillus acidophilus has been shown. PVP nanowires are obtained by electrospinning in two versions: PVPI based on a solution of high molecular weight polyvinylpyrrolidone and distilled water; PVPII based on a solution of two water zinc acetate in distilled water and a solution of high molecular weight PVP in ethanol. In the presence of PVP, there was an increase in viable lactobacillus cells up to 7.4 108 CFU/ml and accumulation of DL-lactic acid during acidification of the test solution to 3.10 and an increase in Eh to + 360.5 mV. PVPI is a more preferred carrier for lactobacilli than PVPII with ZnO. The zinc ions contained in the PVP matrix are capable of causing oxidative stress, followed by the formation of free radicals that damage membrane lipids, proteins and DNA of the prokaryotic cell. The results are aimed at developing new forms of immobilized drugs that can be used as alternative probiotic agents.

Supercritical Assisted Electrospray: An Improved Micronization Process.

A new process is proposed that can largely improve classical electrospray (ESPR) atomization, thanks to the addition of supercritical CO2 (SC-CO2) to the liquid mixture, in which a polymer is dissolved, forming an expanded liquid. The consequent reduction of surface tension and viscosity allows the production of micrometric or nanometric particles of controlled size and distribution at a production rate up to one hundred times that of the traditional process. The new process was applied to particle generation from a very high molecular weight polyvinylpyrrolidone (PVP) and tested at different polymer percentages by weight and at different pressures. Repeatable microparticle diameters and distributions were obtained, ranging between 0.55 and 2.25 µm at PVP concentrations from 1 to 5% w/w and pressures between 80 and 120 bar.

Effect of PVP on fabrication of Cu nanoparticles using an electrical wire explosion method

Cu nanoparticles have several advantages such as their high electrical and thermal conductivity and low cost. Electrical wire explosion (EWE) method is one of the methods used to fabricate metal nanoparticles. The advantages of this technique are the high purity of the nanoparticles, ability to employ this technique in large-scale manufacturing, and high energy efficiency. In previous research, polyvinylpyrrolidone (PVP) was shown to prevent the agglomeration of metal nanoparticles. However, the effect of PVP on Cu nanoparticle synthesis using the EWE method has not been investigated. This study describes the effects of PVP on the size and shape of Cu nanoparticles made by the EWE method. Experiments were carried out with Cu/PVP colloids that were exploded by a current pulse voltage within a few microseconds. The experiment was conducted with various contents and molecular weights of PVP. Fabricated Cu nanoparticles were identified with field-emission scanning electron microscopy and high-resolution transmission electron microscopy. The size of the Cu nanoparticles was measured by the direct light scattering method. The smallest nanoparticles were about 21 nm and obtained when PVP with a molecular weight of 360,000 and content of 1.0 wt% was used. The shape of the nanoparticles changed from anisotropic to isotropic with increasing content and molecular weight of PVP. The electrical resistivity of printed Cu patterns decreased as the Cu nanoparticle get smaller.

Non Monotonous Effects of Noncovalently Functionalized Graphene Addition on the Structure and Sound Absorption Properties of Polyvinylpyrrolidone (1300 kDa) Electrospun Mats.

Graphene is an attractive component for high-performance stimuli-responsive or ‘smart’ materials, shape memory materials, photomechanical actuators, piezoelectric materials and flexible strain sensors. Nanocomposite fibres were produced by electrospinning high molecular weight Polyvinylpyrrolidone (PVP-1300 kDa) in the presence of noncovalently functionalised graphene obtained through tip sonication of graphite alcoholic suspensions in the presence of PVP (10 kDa). Bending instability of electrospun jet appears to progressively increase at low graphene concentrations with the result of greater fibre stretching that leads to lower fibre diameter and possibly conformational changes of PVP. Further increase of graphene content seams having the opposite effect leading to greater fibre diameter and Raman spectra similar to the pure PVP electrospun mats. All this has been interpreted on the basis of currently accepted model for bending instability of electrospun jets. The graphene addition does not lower the very high sound absorption coefficient, α, close to unity, of the electrospun PVP mats in the frequency range 200–800 Hz. The graphene addition affects, in a non-monotonous manner, the bell shaped curves of α versus frequency curves becoming sharper and moving to higher frequency at the lower graphene addition. The opposite is observed when the graphene content is further increased.

Preparation of monodisperse fully aromatic polyimide particles via the polycondensation of diethyl hexafluoroisopropylidenediphthalate with 4,4′-diaminodiphenylether in ethylene glycol

Fully aromatic polyimide particles were obtained in a single step via the polycondensation of diethyl (hexafluoroisopropylidene)diphthalate (6FE) and 4,4′-oxydianiline (ODA) using polyvinylpyrrolidone (PVP) as a steric stabilizer in ethylene glycol. Since the monomers are soluble in ethylene glycol, but the polyimide is insoluble, the polyimide particles grew gradually during the polycondensation process. The particle size and size distribution were controlled by varying the molecular weight and amounts of PVP. The particle size decreased with both increasing concentration and increasing molecular weight of the stabilizer. Furthermore, the solvent composition affected the particle size, i.e., the particle size decreased with increasing volume of glycerol as a cosolvent. Monodisperse particles (diameter: 8.5–1.8 μm) were obtained by varying the amounts of PVP and glycerol. Fully aromatic polyimide particles were obtained in a single step via the polycondensation of diethyl (hexafluoroisopropylidene)diphthalate and 4,4’-oxydianiline using polyvinylpyrrolidone (PVP) as a steric stabilizer in ethylene glycol. Since the monomers are soluble in ethylene glycol, but the polyimide is insoluble, the polyimide particles grew gradually during the polycondensation process. The particle size and size distribution were controlled by varying the molecular weight and amounts of PVP.

The Influence of Polyvinylpyrrolidone Molecular Weight on the Structure and the Spectral and Nonlinear Optical Properties of Composite Materials with CdS/ZnS Nanoparticles

The influence of the molecular weight of polyvinylpyrrolidone on the structure and the spectral and nonlinear optical properties of composite materials (sols and coatings) containing CdS/ZnS nanoparticles is experimentally studied. Cd/ZnS nanoparticles were obtained by a liquid colloid-chemical method in the presence of polyvinylpyrrolidone. It is found that the size of polyvinylpyrrolidone molecules strongly affects the size of forming chalcogenide particles, as well as the structure and the spectral properties of mat-erials.

Controlling the drying process in vacuum foam drying under low vacuum conditions by inducing foaming by needle stimulation of the solution

Vacuum foam drying is a promising drying technique but an extremely high vacuum is needed to achieve “foaming.” The findings reported herein show that, when a solution is partially vacuum-dried to 0.05–2 g-solvent/g-dry matter (initial drying) and the solution is then punctured with a steel needle (needle stimulation), vacuum drying resumes as a result of the solution foaming, even under conditions of an insufficient vacuum (ca. 1,000 Pa) where foaming is minimal. Methanol, ethanol, and isopropanol were used as solvents, and sugar and different molecular weight polyvinylpyrrolidone were employed as solutes. The results indicate that needle puncturing introduces minute bubbles, which then triggers foaming.

Optical Anisotropicity of Core‐Shell or Yolk‐Shell‐typed Ag@Fe3O4 Nanochains

Optical anisotropicity of 1‐dimensional nanochains of yolk‐shell (YOSH) and core‐shell (COSH) Ag@Fe3O4 nanoparticles (NPs) is attractive to comprehend electromagnetic relation in different materials in nanoscale regime. To investigate its unique properties, a YOSH Ag@Fe3O4 nanoscale superstructure is prepared through a successive process using COSH‐NPs via a selective etching approach. The Ag‐core can be etched when exposed to a mixture of polyvinylpyrrolidone (PVP) and hydrogen peroxide (H2O2) solution at 25°C. It is investigated that the etching degree of Ag‐core in the COSH‐NPs is linearly correlated with the average molecular weight and amount of PVP and H2O2. In the optical investigation, one‐dimensional YOSH and COSH nanochains are compared to show the dependence of anisotropic plasmonic response on tuning polarized light angle. The YOSH nanochain shows an insensitive plasmonic shift in respect of varying refractive index of solvent, which is probably related with the void of Ag‐yolk and Fe3O4 shell. It is probable that the unique properties of the COSH and YOSH nanochain can be applied to be a potential photonic device and their ultralow quantity sensing and imaging.

Formulation, characterization and evaluation of mRNA-loaded dissolvable polymeric microneedles (RNApatch)

In this paper, we report a proof of concept study on the fabrication, characterization and therapeutic evaluation of in vitro transcribed messenger RNA (mRNA) loaded in a dissolving microneedle patch (RNApatch). We show that low molecular weight polyvinylpyrrolidone (PVP) can directly be used without further purification for RNApatch fabrication with no detectable mRNA degradation. Physical and functional integrity of mRNA stored within the RNApatch are completely preserved for at least 2 weeks under ambient conditions. While the loading of mRNA into RNApatch is limited by the solubility of mRNA in concentrated PVP solution, mechanical strength of RNApatch is not compromised by the presence of mRNA. RNApatch can mediate in vivo transgene expression of mRNA encoding luciferase for up to 72 hours and transfection efficiency and kinetics mediated by RNApatch compares favorably to subcutaneous injection. Interestingly, mRNA transfection efficiency does not correlate with contact surface area but instead increases with deeper delivery depths. In an E.G7-OVA immunotherapy model, RNApatch induces slightly higher cellular and humoral immune responses compared to subcutaneous injection. In conclusion, RNApatch is a viable delivery platform for mRNA and represents an attractive option with significant translation potential for the delivery of mRNA therapeutics.

Synthesis of Cu Nanoparticles Using Copper Carbonate as Cu Source Toward Versatile Applications.

Cu nanoparticles (NPs) coated with polyvinylpyrrolidone (PVP) were fabricated by polyol method using copper carbonate as a raw material. To increase the reaction temperature, glycol multimers such as diethylene glycol, triethylene glycol, or tetraethylene glycol were examined as a solvent. With increasing degree of multimerization, average diameter of Cu NPs decreased. The synthesis of Cu NPs was further investigated by changing reaction temperature, the amount and molecular weight of PVP in triethylene glycol as a solvent. Average diameter and standard deviation of Cu NPs were found to be highly dependent on those factors. As a result, fine Cu NPs ranging from 28 to 67 nm in average size with narrow size distribution (standard deviation: 16-28%) were obtained. The obtained Cu NPs were applied to a nanofluid, which showed higher thermal conductivity than the theoretical value. The antibacterial activity of Cu NPs was also demonstrated, and found to have strong antibacterial activity.

Electrospun polyvinylpyrrolidone (PVP)/green tea extract composite nanofiber mats and their antioxidant activities

Electrospinning was employed to make PVP (polyvinylpyrrolidone)/GTE (green tea extract) composite nanofiber mats. The electrospun PVP nanofiber mat as well as the PVP/GTE nanofiber mats were uniform. The average fiber diameter of PVP/GTE composite nanofiber mat decreased with increasing the GTE weight fraction (or decreasing the PVP weight fraction) in the PVP/GTE solution because the PVP/GTE solution concentration decreased. Then, the broad FTIR peak representing the stretching vibrations of O–H in hydroxyl groups of phenols and the stretching of N–H in amine groups of the GTE paste shifted to higher wavenumbers in the PVP/GTE composite nanofiber mats. These peak shifts implied that PVP and catechins of GTE in the PVP/GTE composite nanofiber mats had intermolecular interactions via hydrogen bonds between carbonyl groups of PVP and hydroxyl groups of catechins in GTE. Lastly, the antioxidant activity of the PVP/GTE composite nanofiber mat increased with reducing the average fiber diameter because the amount of catechins in the composite nanofiber mat increased with the increase of surface area due to the reduction of the average fiber diameter.

Porous Electrospun Fibers Embedding TiO2 for Adsorption and Photocatalytic Degradation of Water Pollutants.

Using a bipolymer system consisting of polyvinylpyrrolidone (PVP) and poly(vinylidene fluoride) (PVDF), P25-TiO2 was immobilized into thin film mats of porous electrospun fibers. Pores were introduced by dissolving sacrificial PVP to increase surface area and enhance access to TiO2. The highest photocatalytic activity was achieved using a PVDF:PVP weight ratio of 2:1. Methylene blue (MB) was used to visualize contaminant removal, assess the sorption capacity (5.93 ± 0.23 mg/g) and demonstrate stable removal kinetics ( kMB > 0.045 min-1) under UVA irradiation (3.64 × 10-9 einstein/cm2/s) over 10 cycles. Treatment was also accomplished via sequential MB sorption in the dark and subsequent photocatalytic degradation under UVA irradiation, to illustrate that these processes could be uncoupled to overcome limited light penetration. The photocatalytic mat degraded bisphenol A and 17α-ethynylestradiol in secondary wastewater effluent (17 mg TOC/L), and (relative to TiO2 slurry) immobilization of TiO2 in the mat mitigated performance inhibition by co-occurring organics that scavenge oxidation capacity. This significantly lowered the electrical energy-per-order of reaction (EEO) needed to remove such endocrine disruptors in the presence of oxidant scavenging/inhibitory organics. Thus, effective TiO2 immobilization into polymers with affinity toward specific priority pollutants could both increase the efficiency and reduce energy requirements of photocatalytic water treatment.

Effect of PVP Addition in the Preparation of Polyethersulfone (PES)–AgNO3 Antibacterial Membrane

Association of antibacterial agent into polymer–based material is an interesting, recent extension in membrane technologies research area. Asymmetric polyethersulfone–silver nitrate (PES–AgNO3) nanocomposite membranes were synthesized by wet phase inversion with polyvinylpyrrolidone (PVP) as additive. Three different molecular weights (MW) of PVP in the range of 10 K to 360 K were tested for their ability to stabilize and disperse silver in the polymer solution. Results showed that PVP 360 K plays a significant role in altering silver particle size with better dispersion compared to the membranes prepared without addition of PVP and with the addition of lower MW of PVP. Results agreed with the leaching detected by ICP–MS where silver loss during membrane fabrication for PES–Ag–P360 is only 0.4636 ppm (0.0093%). The antibacterial activity for the resultant membranes was tested using inhibition zone method. Results indicated that PES–AgNO3 and PES–AgNO3–PVP (loaded with only 0.5 wt% silver) were antibacterial to Escherichia coli and Staphylococcus aureus. The improvement of antibacterial properties of the prepared membranes could be primarily attributed to the PVP addition as well as the surface morphology and permeation properties.

Ultrasound-assisted interaction between chlorin-e6 and human serum albumin: pH dependence, singlet oxygen production, and formulation effect

The interaction between chlorin e6 (Ce6) and human serum albumin (HSA) in the presence and absence of ultrasound have been investigated by ultraviolet-visible absorption spectroscopy and fluorescence spectroscopy. Ce6 is found to bind strongly to HSA at or near physiological pH conditions, but the strength of the binding is significantly weakened at lower pHs. The intrinsic fluorescence of HSA is incrementally quenched with increasing concentration of Ce6, and the quenching is enhanced after exposure to high-frequency ultrasound. Our experimental results suggest that Ce6-induced sonodynamic oxidation of HSA is mainly mediated by singlet oxygen. The formulation of Ce6 by high molecular weight polyvinylpyrrolidone (PVP) increased its stability in aqueous solutions and its quantum yield of singlet oxygen under ultrasound irradiation.

Preparation and characterisation of melamine-urea-formaldehyde microcapsules containing linseed oil in the presence of polyvinylpyrrolidone as emulsifier

PurposeThe purpose of this work was to express a facile method to fabricate microcapsules containing linseed oil with melamine-urea-formaldehyde (MUF) shell in the presence of polyvinylpyrrolidone (PVP) as an emulsifier. These microcapsules may be used in self-healing coating formulations.Design/methodology/approachIn this work, different types of PVP (i.e., PVP with different molecular weights or K values) were used as emulsifiers and colloid protectors to encapsulate linseed oil in an MUF shell. Moreover, the effect of agitation rate on the morphology of the microcapsules was investigated. Microcapsule morphology and particle size distribution were evaluated using optical microscopy and scanning electron microscopy. Thermal studies were performed using a thermo-gravimetric analysis technique and chemical structure of materials was characterized by using Fourier transform infrared analysis.FindingsIn this work, microcapsules with a regular spherical shape and a shell thickness of about 330 nm were fabricated. The results revealed that the use of PVP in the fabrication of MUF could facilitate the synthesis process by eliminating the necessity of pH control during the reaction. In fact, the pH of the reaction media must be precisely controlled in conventional processes. The yield of microencapsulation was found to be 86.5 per cent when a high molecular weight of PVP (PVP K-90) was used. It was also found that the surface morphology of microcapsules became smoother when PVP K-90 was used. The results showed that the surface roughness and the average particle size decreased with an increase in stirring intensity. Mean diameter of the prepared microcapsules ranged from 34 to 346 μmin for various synthesis conditions.Research limitations/implicationsThis work is limited to the encapsulation of a hydrophobic liquid (such as linseed oil) by an in situ polymerisation of amino resins.Practical implicationsThe presented results can be used by researchers (in academia and industry) who are working in the field of fabrication microcapsules, in various applications such as pharmaceuticals, electrophoretic displays, textiles, carbonless copy papers, cosmetics, printing and self-healing materials.Social implicationsPVP is considered as an environmentally friendly emulsifier. Therefore, this process is less harmful to the environment. In addition, the prepared microcapsules may be used in self-healing coatings, which helps in reducing maintenance costs for buildings and steel structures.Originality/valueEthylene maleic anhydride and styrene maleic anhydride are usually used as emulsifiers in conventional methods for the preparation of amino resin microcapsules. These methods require an intensive and precise pH control to obtain favourable microcapsules, while in the present research, a facile method was used to fabricate MUF microcapsules containing linseed oil without needing any pH control during the reaction.

Novel and simple method to synthesize donut-like TiO2 with photocatalytic activity

This paper presents a novel and simple method to fabricate donut-like TiO2 with efficient photocatalytic activity. Donut-like TiO2 was successfully prepared via electrospraying technique using a low molecular weight polyvinyl pyrrolidone (PVP) polymer. X-ray diffraction measurements show that donut-like TiO2 maintains a pure anatase structure. A transmission electron microscopy image reveals hollow donut-like TiO2. The effects of applied voltage parameter on energy gap, atomic force microscopy micrographs, field emission scanning electron microscopy pictures, and photoluminescence spectra are examined. The photocatalytic properties of donut-like TiO2 were evaluated with photocatalytic degradation of methylene blue (MB) in water under UV light irradiation. Donut-like TiO2 exhibits an efficient photocatalytic activity that reaches 67% after the degradation of MB in aqueous solution for 200min.

Effect of PVP on the synthesis of high-dispersion core–shell barium-titanate–polyvinylpyrrolidone nanoparticles

Monodispersed nanoparticles consisting of barium titanate (BaTiO3, BT) as the core and polyvinylpyrrolidone (PVP) as the shell were synthesized in a PVP-assisted low-temperature process in an aqueous solution at ambient pressure. In order to clarify the mechanism of this unique BT–PVP nanoparticle growth and the origin of the dispersion, the concentration and molecular weight of PVP used in the synthesis were varied, and the size and dispersion of the resulting nanoparticles in water were investigated by field-emission scanning electron microscopy and dynamic light scattering. Monodispersed nanoparticles with an average size of 130 nm were obtained by using an intermediate PVP concentration of 100 g/L and a PVP molecular weight of 10,000 g/mol. The thickness of the PVP shell was estimated by thermogravimetric analysis. For the highly dispersed BT–PVP, the thickness of PVP adsorbed on the BT surface was around 3–5 nm. Direct SEM observation of monodispersed BT–PVP in an aqueous solution using a unique sample holder was also demonstrated for the first time.