PVP Concentration Research Articles

Unusual influence of binder composition and phosphoric acid leaching on oxygen mass transport in catalyst layers of high-temperature proton exchange membrane fuel cells

Oxygen mass transport in the cathode catalyst layer (CCL) of high-temperature proton exchange membrane fuel cells (HT-PEMFCs) plays an important role in promoting the fuel cell performance. The objective of this study is the development of suitable tools and analytical methods for quantitatively characterizing O2 mass transport coefficients in a binder used in HT-PEMFCs from a microscopic and local perspective. A microelectrode electrochemical system with high sensitivity and stability is built in-house. High-resolution cyclic voltammetry, potential-step chronoamperometry and sampled chronoamperometry at the nA scale are successfully performed in a shielding box to determine the O2 mass transport coefficients in a poly (ethersulfone)-poly (vinyl pyrrolidone) (PES-PVP) blend binder with different PVP contents. In addition, we investigate the effect of phosphoric acid (PA) leaching on O2 mass transport in the binder, which is generally used to explain the decline in membrane conductivity. Linear regression analysis reveals that the permeability of O2 in binder can be affected significantly by the PVP content and the PA doping level of the binder in CCL.

Development of a stable oral pediatric solution of hydrochlorothiazide by the combined use of cyclodextrins and hydrophilic polymers.

Hydrochlorothiazide (HCT) is widely used in pediatrics for hypertension management. Due to the lack of pediatric commercial forms, community or hospital pharmacies generally prepare HCT extemporaneous pediatric suspensions by dispersing in water a portion of a crushed tablet or the drug powder; however, any dose or stability control is usually done on these preparations. Obtaining stable HCT solutions is very challenging, due to its low water-solubility and pH-dependent degradation. The aim of this work was to develop a stable 2mg/mL-HCT oral pediatric solution without using co-solvents. Combined use of cyclodextrins (CD) and hydrophilic polymers was exploited to improve poor HCT solubility and stability. HPβCD and SBEβCD were selected, considering their safe toxicological profiles, while PVP resulted the best among the tested polymers. Low PVP concentrations (0.2-1.0%) improved the solubilizing efficiency of both CDs, allowing to reach the prefixed HCT concentration. Different CD-PVP concentrations were used to prepare several 2mg/mL-HCT solutions in pH 5.5 buffer. The best stability was shown by solutions containing the highest SBEβCD concentration (25mM), which allowed a 3-months stability at 4°C. In vivo studies on rats showed that such formulation allowed a more pronounced and more reproducible diuretic effect than the corresponding HCT suspension.

Fabrication of chitosan/polyvinylpyrrolidone hydrogel scaffolds containing PLGA microparticles loaded with dexamethasone for biomedical applications

One of the most effective approaches for treatment of chronic rhinosinusitis is the use of hydrogel scaffolds with the sustained release of a given required drug. With this in mind, first, we synthesized and characterized poly (lactide-co-glycolide) (PLGA) micro and nano particles loaded with dexamethasone (DEX). We observed a 7-day release of DEX from nanoparticles, while the microparticles showed a 22-day release profile. Due to their slower rate of release, the PLGA microparticles loaded with DEX (PLGADEX microparticles) were specifically chosen for this study. As a second step, chitosan/polyvinylpyrrolidone (PVP) based hydrogels were prepared in various weight ratios and the PLGADEX microparticles were optimized in their structure based on variable gelation times. The morphological studies showed PLGADEX microparticles homogenously dispersed in the hydrogels. Moreover, the effect of weight ratio in the presence and absence of optimum percentage of PLGADEX microparticles was studied. The resultant hydrogels demonstrated a range of advantages, including good mechanical strength, porous morphology, amorphous structure, high swelling ratio, controlled biodegradability rate, and antibacterial activity. Additionally, a cytotoxicity analysis confirmed that the hydrogel scaffolds do not have adverse effects on the cells; our release studies in the hydrogel with the highest PVP content also showed 80% release after 30 days. Based on these results we were able to predict and control some of the mechanical properties, including the microstructure of the scaffolds, as well as the drug release, by optimizing the polymers - microparticle concentration, plus their resulting interactions. This optimized hydrogel can become part of a suitable alternative for treatment of allergic rhinitis and chronic sinusitis.

Synthesis and photocatalytic performance of nano-CeO2 by a PVP-assisted microwave interface method for organic dye degradation

Ceria nanoparticles (CeO2-R, R = 2, 5, 10 g/L, where R is the PVP concentration) were successfully synthesized by using a microwave interface method and a PVP surfactant, based on microwave heating and vapor–liquid diffusion. The effect of PVP concentration on the structure, morphology, and the photocatalytic properties was investigated. With the increase of PVP concentration, the particle size of the spherical CeO2-R nanoparticles decreases, the Ce3+ concentration increased, the specific surface area and the light absorption capacity initially increased and then decreased. The CeO2-R (R = 5) sample with the strongest light absorption ability and the largest specific surface area has the highest photodegradation efficiency for methylene blue (MB) under UV irradiation, reaching 95% within 150 min. The degradation efficiency decreased slightly from 95 to 92% after five cycles. This indicates that the CeO2-R sample has excellent stability and good application prospect in organic dye degradation.

Conversion of indomethacin nanosuspensions into solid dosage forms via fluid bed granulation and compaction

Preparation of pharmaceutical nanosuspensions is a popular technique to increase the dissolution velocity of poorly water-soluble drugs. Subsequent drying into a compaction-ready powder or granule is a critical process due to possible adverse solid characteristics and the risk of growth of nanoparticles. This work evaluated the drying of nanosuspensions via fluid bed granulation with focus on the binder selection and used concentrations, as well as the parameters spray rate and atomization pressure. Design of experiments was used to identify significant parameters. Indomethacin nanosuspensions were prepared by wet media milling and dried on a carrier consisting of lactose, microcrystalline cellulose, and crospovidone with and without additional binder during granulation. Resulting granules were compacted into tablets and their in vitro dissolution performances were characterized. A higher content of binder PVP and a higher spray rate led to less growth of resuspended nanoparticles. Finally, indomethacin nanoparticle tablets showed a superior dissolution performance in contrast to raw indomethacin tablets.

Polyvinylpyrrolidone Loaded-MnZnFe2O4 Magnetic Nanocomposites Induce Apoptosis in Cancer Cells Through Mitochondrial Damage and P53 Pathway

MnZnFe2O4 ferrite was successfully synthesized using metallic chlorides and polyvinylpyrolidone, by Co-precipitate method. Deferent concentrations of PVP (0.1, 0.3, 0.5, 0.7, and 0.9) wt%, were used as capping agent to stabilize the particles and prevent them from agglomeration. The PVP content had a vital influence on enhancing the properties of the ferrite nanoparticles. From X-ray data the degree of crystallinity and the Lattice constants (a) of the nanoparticles increased from (8.92 nm) and (8.344 A) to (19.94 nm) and (8.395 A) respectively with increasing PVP concentrations. The morphology and average particle size of the MnZn ferrite nanoparticles were evaluated by scanning electron microscopy (SEM), the values were in a good agreement with the XRD results. Fourier transform infrared spectroscopy (FT-IR) confirmed the cubic structure with octahedral and tetrahedral, also indicated the formation of bond between PVP and surface of metallic hydroxide of ferrite nanoparticles. Vibrating sample magnetometer (VSM) analysis was performed for all samples at room temperature, results showed that the specimens exhibited a paramagnetic behavior in the absence of PVP while in the presence of PVP they have super paramagnetic characteristics. The values of saturation magnetization (Ms) (1.78–17.67 emu/g), remnant magnetization (Mr) (0.0022–0.0696 emu/g) also increased with increasing pvp concentration. Polyvinylpyrrolidone loaded-MnZnFe2O4 magnetic nanocomposites were used it alone or as a combination therapy with NIR laser, and alternating magnetic field (AMF) as anti-proliferative agent against breast cancer cell lines AMJ-13, MCF-7,and ovarian cancer cell line SKOV-3 as well as against normal cell line HBL. While, its capability to induce apoptosis was detected using different techniques which is acridine orange/ethidium bromide (AO/EtBr) staining and mitochondrial membrane potential (MMP), and flow cytometry assay membrane potential (MMP). q-PCR was used to investigate the changes in the expression of P53 gene. The influence of Polyvinylpyrrolidone loaded-MnZnFe2O4 magnetic nanocomposites in viability of breast and ovarian cancer cells alone or when they used as a combination therapy with laser photo-thermal therapy and alternating magnetic field (AMF) was also tested using MTT assay. Our results in the present study demonstrated that the inhibition activity of Polyvinylpyrrolidone loaded-MnZnFe2O4 magnetic nanocomposites against treated cancer cell lines increased when Polyvinylpyrrolidone loaded-MnZnFe2O4 nanocomposites used with NIR laser, while highly increased cytotoxic activities were observed after exposure of Polyvinylpyrrolidone loaded-MnZnFe2O4 nanocomposites to induction heating with AMF. Treated cancer cells with polyvinylpyrrolidone loaded-MnZnFe2O4 magnetic nanocomposites significantly increased ROS synthesis, with subsequent reduction of the MMP. The results of the current study show that tested compounds suppressed cancers cells’ proliferation and has a growth inhibitory effect on different cancer cells, resulting in apoptosis as a novel pathway that involves mitochondrial damage mechanism via activated P53. Taken together the present data suggest that the Polyvinylpyrrolidone loaded-MnZnFe2O4 magnetic nanocomposites could be promising therapy protocol for cancer cells.

Effect of Cobalt Chloride as Filler and PVP on the Optical Properties of PVA/PEG/PVP Blends

Different concentrations of PVA/PEG/PVP blends as well as different composites of cobalt chloride, as filler, embedded in apolymeric blend as a hosting matrix, were prepared by solution casting method. The samples were characterized by a powerful technique as X-ray diffraction (XRD) which shows that the value of crystallite sizes (D) was mainly depending on the content of both of PVP and cobalt chloride (CoCl2). The studying of the optical properties for the samples was investigated through understanding the obtained results of the absorption and reflection measurements. The absorption spectrum was increasing with increasing each of PVP content in PVA/PEG/PVP blends and the filler content in all the composites of CoCl2/PVA/PEG/PVP. Also, the concentrations of PVP and CoCl2 had an influence on the magnitude of the calculated values of the static dielectric constants (e∞), the static refractive index (n0), the moments of the optical spectrum (M1 and M3), the average interband oscillator wavelength (λ0) and the oscillator length strength (S0). The estimated values of both of the oscillator energy gap E0, and the dispersion energy Ed, were decreasing by increasing the content of CoCl2 in the composites CoCl2/PVA/PEG/PVP 72/5/23 wt %.

Investigation of the effects of Pt/Pd composition and PVP content on the activity of Pt/Pd core-shell catalysts

Among the various fuel cell electrocatalysts studied for the cathodic oxygen reduction reaction and anodic fuel oxidation reaction, platinum-based materials have attracted much attention over the past decade because of their high activity for both reactions. However, Pt-based catalysts suffer from several problems, such as their high cost, low abundance, and low long-term stability. Bimetallic Pt-based nanostructures with a core–shell structure have been considered as candidate cathode catalysts for polymer electrolyte fuel cells. In this study, a Pt/Pd/C catalyst was successfully synthesized by the hydrogen-sacrificial protection method to improve the performance of a membrane electrode assembly. Furthermore, on the basis of electrochemical spectroscopic findings, it was shown that control of the surface structure is an effective strategy to improve the cell performance of the Pt/Pd/C catalyst.

Fabrication of nanofiltration membrane based on non-biofouling PVP/lecithin nanofibers reinforced with microcrystalline cellulose via needle and needle-less electrospinning techniques

In this work, polyvinylpyrrolidone nanofibers were electrospun incorporated with lecithin, zero-charge natural segment, as non-biofouling nanofiltration membrane with tunable porous structures. Optimum conditions were studied to obtain nano-pore size capable of nano-scaled objects reduction using needle and needleless electrospinning apparatuses. Fiber diameters were in proportional relationship with PVP concentrations to range from 1.2 um to 34 nm at 10 to 5% wt/v PVP respectively. Microcrystalline cellulose (MCC) was added and PVP fibers were photo-crosslinked to enhance the mechanical strength. Mechanical properties of electrospun fibers were enforced up to 279% in the presence of microcrystalline cellulose while increased by 125% when exposed to photo-crosslinking for 8 h by UV-light radiation. UV-crosslinking has significantly improved the hydrophobicity of the final mat to report contact angle bigger than 90° at 16 h. Protein adhesion test was conducted to indicate the capability of the electrospun membrane to bypass the blood-plasma products. Zero protein adhesion was recorded by adding only 2% wt/v of lecithin.

Micronization of Hydrothermally Extracted Phytochemical Compounds from <i>Gracilaria</i> Sp Using Electrospraying

The hydrothermal extraction was carried out in a semi-batch extractor at a temperature of 160°C, a pressure of 7 MPa, and a water flowrate of 1 mL/min. Electrospraying was conducted at various voltages of 12, 14, and 16 kV, various distances between tip and collector of 6, 8 and 10 cm, precursor solution flow rate of 0.05 mL/h, and PVP concentrations of 6 and 8%, Particles obtained from electrospraying process were analyzed by SEM, FTIR, and spectrophotometer. The antioxidant efficiency (AE) of the particles was also examined. Based on the results, the morphology of particles was spherical with diameter less than 3 µm. The highest value of AE was 0.1058 min-1 that indicated that Gracilaria sp extract in the particles produced by electrospraying has good antioxidant activity. In the FTIR analysis, carrageenan and flavonoids were contained in the particles. The result indicated that hydrothermal extraction followed by electrospraying process could be one alternative process for obtaining the best phytochemical particles.

Control of Nd-Fe-B Morphology as Function of the PVP Concentration Using Electrospinning Process

Control of Nd-Fe-B Morphology as Function of the PVP Concentration Using Electrospinning Process

On the nature of macroradicals formed upon radiolysis of aqueous poly(N-vinylpyrrolidone) solutions

In this work we have explored the nature of macroradicals formed upon radiolysis of aqueous poly(N-vinylpyrrolidone) (PVP) solutions using pulse radiolysis, density functional theory (DFT) and literature data. On the basis of literature data on site-specific kinetics of hydrogen abstraction from simple amides and spectra corresponding to specific radical sites on the same amides we have assessed the distribution of H-atom abstraction by •OH radicals from different positions on the pyrrolidone ring and the polymer backbone. Pulse radiolysis experiments performed at different doses per pulse and different PVP concentrations demonstrate that the H-abstracting radiolysis products are not quantitatively scavenged by the polymer when the dose per pulse exceeds ≈40 Gy. The implications of this are discussed in the context of radical-initiated crosslinking reactions. At a mass fraction of 0.1% PVP and doses per pulse ranging from 7 Gy to 117 Gy, the overall radical decay observed at 390 nm follows second order kinetics with rate constants on the order of 109 dm3 mol-1 s-1.

Coaxial Electrospinning: Jet Motion, Core–Shell Fiber Morphology, and Structure as a Function of Material Parameters

Two core–shell-structured polystyrene/poly(vinyl pyrrolidone) (PS/PVP) and PVP/PS composite fibers were prepared via coaxial electrospinning in this study. Different concentrations of PVP solutions with a variety of viscosities and conductivities were adopted in the experiment. The influences of both viscosity and conductivity on the Taylor cone, jet motion, morphology, and internal structure of the resultant core–shell fiber were investigated in a comprehensive and systematic manner. As shown in the images of Taylor cone and jet motion, which were captured by a high-speed camera, different PVP concentrations in the core and shell would result in different core and shell thicknesses as well as distinct jet motion patterns including straight jet length, envelop angle, and frequency of whipping process, thus obtaining the core–shell fibers with different diameters. Not only jet motion and Taylor cone but also the polymer solution concentration and the role of PVP in core and shell have a tremendous influence on the morphology and the internal structure of the resultant core–shell fiber. Additionally, the formation mechanisms of PS/PVP and PVP/PS fibers were studied by means of Fourier transform infrared (FTIR). The experimental results provide a basis for further design and optimization of processing conditions, so as to control the nanostructure of core–shell composite fibers.

From Silver Plates to Spherical Nanoparticles: Snapshots of Microwave-Assisted Polyol Synthesis.

The fabrication of silver nanoparticles (Ag NPs) with different sizes by microwave (MW)-assisted synthesis is presented. The fast heating of the MW technique, combined with the possibility to thermally quench the reactions, enabled us to capture snapshots of nucleation and growth processes difficult to accomplish in other techniques. The Ag NPs were synthesized using poly(vinylpyrrolidone) (PVP) through a polyol approach. The effects of the reaction time, the reaction temperatures, and the silver precursor concentration were investigated. The influence of agitation, the PVP concentration, and the initial conditions of the silver precursor was also studied. It is found that at very short reaction times and at low temperatures, polyhedral plates are formed with sizes ca. 300 nm and large polydispersity. However, by increasing the time or the temperature, a size and shape refinement is observed resulting in 10 nm spherical NPs with low polydispersity. Mechanistic insights are provided based on the observations extracted from transmission electron microscopy (TEM) and ultraviolet–visible spectroscopy (UV–vis). A formation mechanism starting from kinetically favored silver polyhedral plates to thermodynamically favored spherical nanoparticles is proposed. Understanding these effects allowed us to control the particle size and the tuning of Ag NPs on-demand. Moreover, the reproducibility and scalability of the process and the long-term stability of the NPs in aqueous solutions are demonstrated. Finally, we provide a recommendation regarding the use of fresh PVP as a capping and stabilizing agent.

Silicon micro pyramidal syringe array for electrospinning spiral shape single fiber

In this study, a new method is presented to fabricate spiral shape single fiber. The micro-needle array (40 μm hole diameter, 80 μm outer diameter, and 100 μm height) is utilized instead of the needle to reduce the diameter of fibers which are electrospun from 23Wt% PVP concentration. In order to have fine and bead-free fibers, the structural parameters of the micro-needle array and space which close microneedles act as an individual one are simulated. The Wet and Dry Etching techniques are used for fabrication of micro-needles. The experimental setup consists of the stepper motor and micrometer head as the pump, distance controller, and voltage generator. The single fiber can be electrospun by applying 1–3 kV bias within 1 mm gap between micro-needle and collector. Using nonconductive collector causes the formation of spiral type single fiber instead of agglomerate fiber. Elastic and expulsion forces in charged fibers seem to be the main reasons of fiber separation and spiral shape formation. The spiral shape fiber is made without traditional lithography techniques like direct patterning or contact exposure which are more expensive and time-consuming. The alteration in the fiber pattern can be seen by changing the applied voltage and spinneret, microneedle and needle. After various experiments, spirality pattern electrospun by microneedle with 10–15 μm and 15–35 μm distribution area of first and second circles and 500–570 nm and 570–660 nm diameter of first and second circles is gained as the structure with minimum distribution area and fiber width. This structure is created when the applied voltage and distance between microneedle and collector are 1kV and 1 mm.

Effect of Supplementation of Polyvinylpyrrolidone in Extender on Buffalo Semen Parameters

The current study was planned to evaluate the supplementation of Polyvinylpyrrolidone in extender on cryopreservation of Nili-Ravi buffalo bull semen. The semen samples were collected from Nili-Ravi buffalo (Bubalus bubalis) bull kept at SPU Qadirabad, District Sahiwal, Pakistan. Qualifying semen ejaculates having motility >60%, volume >5-6ml and concentration >0.5 billion/ ml were diluted 50 × 106 motile sperm ml approximately at 37°C in Tris-citric acid extender supplemented with different concentrations of PVP (0.01, 0.05, 0.1mM). The extender without PVP was kept as control. Semen was stored at 4°C for a period of 2 h and kept at 4°C for 4h. Semen was filled in 0.5 ml French straws using suction pump at 4°C, plunged and stored in liquid nitrogen (-196°C). Semen straws were rewarmed at 37°C for 30 seconds and assessed for sperm motility, plasma membrane integrity (PMI), dead sperm percentage and the live sperm percentage. The data on the role of PVP on different parameters of semen quality were analyzed by using ANOVA and RCBD. Higher percentage (P< 0.05) of sperm motility (66.1±7.51 and 59.4±10.72) and PMI (72.9±5.39 and 75.7±6.5) was observed in extenders having 0.05 mM and 0.1mM PVP compared to extenders having 1.5mM PVP and control. The percentage acrosomal integrity was observed greater (P< 0.05) in extended semen containing 0.1mM (68.2±0.50) PVP compared to extenders having 0.01 and control.

Rheological and optical characterization of Polyvinylpyrrolidone (PVP) - Polyethylene glycol (PEG) polymer blends

Polymer blends of different concentrations for PVP-K30 and different additive weights of PEG8000 have been prepared as polymeric blends solutions. The rheological and optical properties of the blends samples have been investigated using Ostwald viscometer and Refractometer. The results showed that the density, shear, relative and specific viscosities are increases with the increasing of PVP concentration and additive weight of PEG. The optical constant values such as refractive index, reflectance, molar reflectance, coefficient of finesse and Brewster Angle are increase with the increasing of PVP concentration and additive weight of PEG while the critical angle has the revers behavior.

Evaluation of nano grain growth of TiO2 fibers fabricated via centrifugal jet spinning

Nanomaterials form the main thrust for modern day technological and industrial applications, including but not limited to, super-capacitors, membranes, batteries, filters, sensors, tissue engineering, wound dressing, protecting vesture, reinforcement in composite materials, etc. Ceramic nanofibers are at the forefront of these materials due to their high surface area and tunable nano structures and porosity. However, obtaining nanofibers with a well-developed uniform crystallinity and a perfect morphology is a challenging task. Among various techniques utilized for preparation of nanofibers centrifugal jet spinning covets merits due to its high efficiency production rate, cost adequacy and operational safety. In the present manuscript we report preparation of TiO2 nanofibers by Sol–Gel Course with Centrifugal Jet Spinning using tetrabutyl titanate as main organic titanium precursor. Herein we demonstrate that a well-developed crystallinity and a perfect morphology of TiO2, from Nano to micro-scales, can be achieved after decomposition of polymer and removal of carbon. Effect of various factors such as PVP content, speed of rotation, humidity and heat treatment on the fiber growth was investigated. Effect of variation in soaking time and different temperatures on the TiO2 nanofiber grain growth was also investigated. Phase structure of TiO2 nanofibers was characterized by X-ray diffraction (XRD). Microstructure of the nanofibers was analyzed using Scanning Electron Microscopic (SEM) studies and Transmission Electron Microscope (TEM) studies. Kinetic exponents of grain growth were likewise acquired by with the help of an image processing software. Outcomes of our investigations show that crystallinity and morphology of grains of fibers are highly sensitive to temperature and soaking time. Image analysis demonstrates that sintering temperature greatly affects the crystallinity and grain size of the nanofibers over 700 °C.

Porous carbon fibers for effective hydrogen evolution

Carbon fibers (CFs) with unique physicochemical properties have been considered as a sustainable material for use as a catalytic support for hydrogen evolution reaction (HER). Porous carbon microfibers (PCFs) were generated by utilizing the needle less electrospinning technology (NLE). The first approach involved the formation of porosity in precursor polyacrylonitrile/polyvinylpirolidone (PAN/PVP) fibers by washing out PVP and carbonization of remaining PAN. Although the sufficient porosity was achieved with increasing PVP content, the total bulk porosity was lost. The second approach was simple removal of PVP, based on different polymer degradation process at high temperatures. The most efficient way was utilization of sodium dodecyl sulphate (SDS) as an anionic surfactant. Binding SDS on PVP polymer chain caused the formation of micelles, which formed regular porous structures in the fibrous carbon matrix after carbonization. The formation of porosity and electrocatalytic activity of CFs after carbonization in Ar and H2 reduction atmosphere were studied. The electrocatalytic results have pointed out that the composition of precursor fibers PAN/PVP/SDS heat treated without previous preoxidation process, carbonized in Ar atmosphere and followed in H2 atmosphere can be efficiently used as a porous material platform for different modification and further application as a potential electrocatalysts for HER.

Chemical synthesis and optical properties of composite materials containing PbI2 nanoparticles

The aqueous sols and composite organic-inorganic coatings containing PbI2 nanoparticles (size ∼ 4 nm) have been prepared. The absorption, photoluminescence and nonlinear transmittance (at 532 nm wavelength) have been studied. The electronic absorption spectra of PbI2/PVP sols showed major peak of ground state near 406 nm, which slightly blue shift with decreasing size. Obtained materials are characterized high transparency in visible spectral range and demonstrate quantum confinement effect. PbI2/PVP composite films manifested dependence of radiation resistance with PVP content at ns-laser exposure and size dependence of nonlinear transmittance.