Adsorption Of Polyvinylpyrrolidone Research Articles

The influence of ultra-probe sonication and polyvinylpyrrolidone on dispersion stability and photocatalytic activity of Ag-TiO2 nanoparticles

The growing use of silver-modified titanium dioxide nanoparticles (Ag-TiO2 NPs) raises environmental concerns. In industrial applications, ultrasonication and surfactant addition are widely employed to improve the efficiency of small amounts of Ag-TiO2 for better dispersion stability. Understanding the stability and dispersion of Ag-TiO2 NPs is crucial. The dispersion stability of Ag-TiO2 NPs is greatly influenced by ultra-probe sonication and polyvinylpyrrolidone (PVP). Ag-TiO2 NP concentrations from 0.1% to 10.0% m/v and PVP concentrations from 0.006% to 0.400% m/v were both used in this study. The effect of ultra-probe sonication presented a high sedimentation height ratio and turbidity below the settling time of 90 min for 0.1%Ag-TiO2 without PVP. A sonication amplitude of 35% and a sonication time of 15 and 30 min showed optimal conditions for good dispersion for 0.1% and 1.0% Ag-TiO2 whereas a sonication amplitude of 20% for 70 s and 140 s was suited for 5.0% and 10.0% Ag-TiO2, respectively. The concentration of PVP was found to be 0.04 times the concentration of Ag-TiO2 for good dispersion. Coordination bonds on the surface of Ag-TiO2 with the carbonyl group served as proof of the chemical adsorption of PVP and Ag-TiO2 NPs. The PVP-coated Ag-TiO2 NPs showed smaller particle sizes and a narrower size distribution than Ag-TiO2. The PVP-coated 1.0% Ag-TiO2 NPs provided lower methylene blue degradation ((5.06 ± 0.76) × 10−3 min−1) under visible light than those without PVP ((9.90 ± 0.74) × 10−3 min−1). These findings advance our understanding about how PVP affects dispersion and photocatalytic activity on Ag-TiO2 and suggest the potential applications as a water pollution coating material.

Crystal engineering of quercetin via combined adsorption of polyvinylpyrrolidone and tannin

Crystal engineering of quercetin via combined adsorption of polyvinylpyrrolidone and tannin

Fabrication of micro/nano spherulitic hierarchical energetic materials via noncrystallographic branching induced by polymer additives: A case study of 2,2′,4,4′,6,6′-hexanitrostilbene (HNS)

In this work, the micro/nano spherulitic hierarchical 2,2′,4,4′,6,6′-hexanitrostilbene (HNS) with the excellent specific surface area was prepared for the first time, which was expected to overcome the agglomeration problems of nanoscale HNS. In detail, poly(N-isopropyl acrylamide) (PNIPAM), polysuccinimide (PSI), and polyvinylpyrrolidone (PVP) were selected as additives to induce forming spherulitic HNS. Leaflike crystals were obtained in the presence of PNIPAM, while spherulitic HNS could be fabricated in the presence of PSI or PVP. And the prepared spherulitic HNS owned nearly 6 times the specific surface area of the raw HNS, with decreased impact sensitivity and advanced melting and decomposition temperatures, demonstrating a good desensitization effect, and a favorable energy release of the hierarchical structure. Moreover, morphological changes under the effect of the molecular weight and concentration of PVP were explored. The approximated morphological evolution of spherulitic HNS was consistent with the classical spherulitic growth by noncrystallographic branching. Furthermore, it was verified that preferential adsorption of PVP and PSI on the HNS inhibits the growth steps of the (200) face and introduces stress to generate crystal defects, which triggers noncrystallographic branching and further spherulitic growth. Overall, the strategy of fabricating micro/nano spherulitic hierarchical energetic materials via polymer-additive induced noncrystallographic branching is promising to solve the problems of nanoscale energetic materials in agglomeration and microscale bulk crystals in low activity.

Efficient Separation of Ultrafine Coal Assisted by Selective Adsorption of Polyvinylpyrrolidone

The efficient separation of ultrafine coal is a challenging process due to the ultrafine particle size and gangue entrainment. In this study, a polymer, polyvinylpyrrolidone (PVP), was introduced as a regulator for ultrafine coal beneficiation. The addition of PVP improved the combustible recovery of clean coal and decreased the ash content. This effect was also presented by the selectivity index. The regulation mechanism of PVP was investigated using diverse methods. The adsorption tests performed demonstrated the adsorption amount of PVP on coal, kaolinite, and quartz, which were related to the increase in the separation efficiency. A zeta potential analyzer was employed to elucidate the effect of PVP on the electrical properties of ultrafine particles. The results revealed that the electrokinetic potential of mineral was sensitive to the varying PVP concentration. The particle size distribution was observed to value the influence of PVP on the particle behavior, which was tested by a laser particle size analyzer. X-ray photoelectron spectroscopy was used to investigate the surface elemental compositions of coal, kaolinite, and quartz, which were regulated by the adsorption of PVP. This research is beneficial to understanding the role of PVP as regulators and provides a basis for the efficient separation of ultrafine coal.

Understanding the Role of Polyvinylpyrrolidone on Ultrafine Low-Rank Coal Flotation.

Effective regulation reagents are essential in low-rank coal flotation for improving the floatability of ultrafine particles. Polymer regulators have great potential in the surface modification of ultrafine coal particles. A novel nonionic polymer, polyvinylpyrrolidone (PVP), is evaluated in this study to determine its effectiveness as a regulator in floating ultrafine low-rank coal. Laser particle size analysis is used to discern both the size distribution of coal particles and the change in size distribution. Contact angle tests are carried out to evaluate the wettability of low-rank coal. Surface functional groups of low-rank coal are analyzed by Fourier transform infrared spectroscopy, and the surface interaction energy is tested by X-ray photoelectron spectroscopy. The results show effective adsorption of PVP and demonstrate the effects of PVP at the coal surface. The adsorption of PVP changes the proportion of exposed carbon and oxygen-containing functional groups on the surface of low-rank coal, regulating the size distribution of low-rank coal particles in suspension. The success of polyvinylpyrrolidone as a regulator in low-rank coal flotation is demonstrated, and the mechanisms by which PVP can affect ultrafine low-rank coal flotation are elucidated.

Modulation of Cerium Carbonate Crystal Growth by Polyvinylpyrrolidone using Density Functional Theory.

Cerium carbonate crystal morphology is predicted using density functional theory (DFT) simulations in this paper. In the nucleation phase, the ketone group in polyvinylpyrrolidone (PVP) will preferentially bind to Ce3+ to form complexes and provide heterogeneous nucleation sites for the system, prompting the nucleation of cerium carbonate crystals. In the growth stage, due to the adsorption of PVP, the probability of (120) crystal plane appearing in the equilibrium state is the greatest, resulting in the formation of hexagonal flake cerium carbonate crystals with (120) crystal plane as the oblique edge. Experimentally, hexagonal sheet cerium carbonate crystals were successfully prepared using PVP as a template agent. Therefore, DFT can be used to predict the morphology of cerium carbonate crystals, which not only elucidates the growth mechanism of cerium carbonate crystals, but also greatly reduces the experimental cost.

Corrosion Inhibition and Adsorption Mechanism of PVP for Mild Steel in 1.0 M H2SO4: Experimental and Theoretical Approach

Aim:Corrosion of mild steel pipe line when exposed to dilute sulphuric acid is a very serious problem for people in the industry and they are in constant search of highly efficient corrosion inhibitors for acidic medium. For designing new corrosion inhibitors, a through knowledge of corrosion and adsorption mechanism is required.Background:Pitting, cracking and uniform types of corrosion are very common forms of corrosion in dilute sulphuric acid medium. A highly efficient acid corrosion inhibitor is required to minimize all these three forms of corrosion.Objective:The objective was to provide a solution for pitting, cracking, and uniform types of corrosion and to study corrosion and inhibition mechanisms so that highly efficient corrosion inhibitors can be designed.Methods:Polyvinyl pyrrolidone (PVP) was explored as a corrosion inhibitor for mild steel in 1.0 M H2SO4 by experimental and theoretical techniques. Experimental techniques used were impedance, weight loss, metallurgical microscopy, and polarization. Theoretical techniques used were DFT, MD simulation, Frontier molecular orbital, Langmuir, and Frumkin adsorption. Theoretical parameters like interaction energy, adsorption energy, Fukui function, chemical potential, electron density distribution, HOMO/LUMO eigenvalue, etc., help in understanding the mechanism of adsorption of PVP on the Fe (110) surface.Results:Experimental results were supported by theoretical studies. A linear relation was observed between PVP concentration and inhibition efficiency. A maximum of 85.92% inhibition efficiency was observed with a regression coefficient of 0.998. The pore length, the number of pits, and cracks intensity decrease with the concentration of PVP. The waste dilute H2SO4 after the weight loss study was investigated for its biocompatibility and was found to be within the acceptable limit.Conclusion:PVP was proved to be a highly efficient acid corrosion inhibitor for mild steel in 1.0 M H2SO4 medium.

Anisotropic growth of gold nanocrystals induced by concerted adsorption using a photochemical approach

Photochemical reduction of noble metal ions in the presence of stabilizers that selectively adsorb on different crystal planes is a fascinating method for synthesizing shape-controlled metal nanocrystals (NCs). In this study, we demonstrate the photoreduction of Au3+ ions in the presence of polyvinylpyrrolidone (PVP) and Br− ions, that are classified into different categories of protective agents. Au nanoplates with atomically flat surfaces are obtained by the photoirradiation of an aqueous solution containing Au3+, PVP and Br−. Notably, PVP preferentially adsorbs along the perimeter, while Br− ions tend to adsorb on the flat top and bottom (111) faces. The selective adsorption of these structurally distinct stabilizers promotes two-dimensional growth of the Au nanoplates. PVP serves not only as a protective agent but also as a reduction agent in the photoreduction process. At high concentrations of Br− ions, the adsorption of the Br− ions also occurs at the perimeter, which kinetically traps the side growth of the nanoplates and leads to the formation of polygonal Au nanoplates. In other words, competitive adsorption of PVP and Br− at the facets and their density kinetically affect the shape of the formed Au NCs. This concept was successfully applied to control the photoreduction of Au3+ ions into icosahedral Au nanoparticles.

PVP-Oxime-SiO2- Adenine, Antibacterial and Anticorrosive Behavior

As nanotechnology developed, the chemical architecture of materials was modified. Our study aims to develop nanohybrid sol-gel processes comprising silica particles and a polymer resin, including functionalized carboxylic groups (typically epoxy or phenolic resins). A film of ceramic glass is formed when the metallic plate is coated. It is possible to obtain corrosion-resistant properties by incorporating these particles into polymeric matrixes. Researchers studied infrared spectroscopy and scanning electron microscopy to determine the structure of RF refers to phenolic resin, RFF refers to resin functionalized, and RF-SIO2 and RFF-SIO2 refers to their respective hybrids.
 As a result of polarization, Polyvinylpyrrolidone (PVP) appears to act like a mixed-type inhibitor. The charge transfer process is largely responsible for preventing corrosion of the C-steel. Using weight loss as a measure of inhibitory efficacy ranged from 56 to 83% while using electrochemical methods, it was 60 to 90%. PVP adheres to steel and prevents corrosion, according to different tests. The Langmuir adsorption isotherm is found to govern PVP adsorption on the C-steel surface. An explanation for PVP's inhibitory action is suggested. A thermodynamic parameter Eapp is determined by the adsorbed PVP on the C-steel surface, *H, and *S decrease. As inhibitor concentration and temperature increase, so does PVP's inhibition efficiency.

The role of polyvinylpyrrolidone in the selective separation of coal from quartz and kaolinite minerals

High-effective flotation of valuable coal resource from gangue is more challenging due to the increase of ultra-fine minerals in coal slime. Despite the use of novel flotation equipment and process strengthening regulation, the method of flocculation of coal or gangue particles to enhance selective separation draws increasing attention recently. The great potential in selective flocculation of particles makes the development of novel polymer flocculants a research hotspot in this field. Particularly, as a kind of polymeric reagent, polyvinylpyrrolidone (PVP) has great significance in clay aggregation/dispersion whereas there are few related researches in coal flotation. Thus, the effect of PVP on coal flotation was systematically investigated in this study by flotation tests and the measurements of zeta potential, turbidity, FBRM, and X-ray photoelectron spectroscopy. The results proved that PVP would be preferentially adsorbed on quartz and kaolinite surfaces rather than coal. The adsorption of PVP with low dosage induced the aggregation of quartz and kaolinite, as indicated by turbidity and FBRM results, while it basically made no difference on coal. It was discovered that the selective flocculation of quartz and kaolinite by PVP promoted the selectivity of flotation. This study furnishes a novel and feasible polymer flocculant to improve coal flotation efficiency. • PVP as a flotation regulator could reduce the ash content of clean coal. • PVP could improve flotation selectivity by flocculation of gangue particles. • PVP could adsorb preferentially on quartz and kaolinite than coal.

Interactions in solvent–polycaprolactone–cellulose nanocrystals–polyvinyl pyrrolidone system: Experiment and molecular dynamics simulation

In this paper, physical adsorption of polyvinylpyrrolidone (PVP) was used as the method of surface modification of cellulose nanocrystals (CNCs). The work also considers the PVP molecular weight effect on dispersion of the surface-modified CNC in dichloromethane (DCM). The authors analyze the physicochemical properties of the composite with polycaprolactone (PCL) - CNC/PVP/PCL - prepared from a solution of PVP-modified CNCs in DCM, and conduct a molecular dynamics simulation of the interactions between the system (CNC, PVP, PCL) components in vacuum and in a solvent medium (water, DCM). According to the simulation results, the CNC/PVP/PCL composite has the following structure: PCL macromolecules have practically no direct contacts with the CNC surface but are located between the PVP macromolecules that, in their turn, are predominantly located near the CNC particle surface.

PVP-assisted laser ablation growth of Ag nanocubes anchored on reduced graphene oxide (rGO) for efficient photocatalytic CO2 reduction

Metallic nanoparticles loaded graphene nanocomposites have been widely studied for various scientific and technological applications. In this study, a facile method was reported to realize a straightforward growth of shape and size-controllable of metallic nanoparticles, and the subsequent hybridization with graphene in solution by strategically coupling wet-chemical route and laser ablation. By mixing graphene oxide (GO) with a tunable concentration level of polyvinylpyrrolidone (PVP) in aqueous solution, Ag nanocubes with a face-centered cubic crystal structure were generated by pulsed laser ablation and then mounted on GO nanosheets with the assistance of PVP. The preferential adsorption of PVP to Ag (100) crystal face led to the production of Ag nanocubes with exposed (100) facet. The result showed that the morphological yield of spherical particles decreased with the increase in PVP concentration. X-ray diffraction (XRD) and UV–visible spectroscopy analyses confirmed that GO was partially reduced. In the reduction of CO2 gas, the photocatalytic conversion rate could achieve 133.1 μmol g−1 h−1 in 6 hrs for cubic Ag-loaded reduced GO composites.

Direct recovery of copper nanoparticles from leach pad drainage by surfactant-assisted cementation with iron powder

Copper nanoparticles were directly recovered from a leach pad drainage by surfactant-assisted cementation with iron powder. Factorial experimental designs were implemented to assess the influence of polyvinylpyrrolidone (PVP), sodium dodecyl sulfate (SDS) and temperature on cementation kinetics and copper particle size. Analysis of variance (ANOVA) was performed to quantify the effect of the investigated factors. Copper(II) was selectively reduced to metal copper by Fe powder, while Mn, Fe, Cd and Zn ions were left in solution. The cementation proceeded under enthalpic driving force and could be described by a pseudo-second-order kinetic model. Without the surfactants, the activation energy of cementation was 22.7 kJ/mol and the cemented product aggregated into micro-clusters ranging from 1 to 15 μm in size, depending on the temperature. The cementation with PVP at above 311 K was controlled by physical adsorption of PVP on Fe powder and exhibited an activation energy of about 10 kJ/mol. The average size of copper particles obtained using 4 mM PVP at 348 K was 280 nm. Adding SDS was associated with a dramatic increase in the activation energy to about 45 kJ/mol, and with the formation of nanoparticles. Using 0.2 M SDS at 348 K enabled the recovery of Cu of about 99% purity with an average particle size less than 100 nm. All results suggested that capping by SDS and PVP inhibited the cementation kinetics but provided the templating ability required to form nanoparticles.

Polymeric Stabilization of Nano‐Scale HMX Suspensions During Wet Milling

AbstractThe focus of this paper is to investigate the polymeric stabilization of cyclotetramethylene tetranitramine (HMX) suspensions using polyvinylpyrrolidone (PVP). The PVP adsorption on HMX surface was studied using zeta potential measurements, which revealed that the shorter PVP polymer chain (lesser molecular weight) adsorbed better than the longer one (greater molecular weight). This study also showed that the solvent dramatically affects the PVP adsorption. A turbidity test was conducted, showing that lower molecular weight PVP offers better stability. This stability is enhanced by increasing the ethanol concentration. The depletion mechanism was responsible for HMX stabilization with ethanol. Finally, a milling study was conducted to compare the HMX with and without a stabilization mechanism. This study indicated that PVP in 50 % water/50 % ethanol was able to stabilize HMX by depletion and reduce the size to 180 nm within 10 minutes of milling. Strong aggregation was observed for HMX milled in the absence of the stabilization mechanism. The stabilization techniques discussed in this study appeared to lead to a shorter processing time and a more efficient milling process when utilized. Under comparable milling conditions, a particle size of 180 nm could be achieved with stabilization compared to 500 nm without. Such a dramatic improvement of the milling process bodes well for future nanoHMX production, as well as that of similar materials.

Tuning crystallization and morphology of zinc oxide with polyvinylpyrrolidone: Formation mechanisms and antimicrobial activity

Zinc oxide (ZnO) particles with different shapes and sizes have been previously reported to possess unique optical, electrical, photocatalytic, and antimicrobial properties. Capping agents are routinely used to control particle morphologies; however, few studies have evaluated the influence of capping agents on the growth kinetics of ZnO particles of different shapes. Herein, we report a simple water-based chemical precipitation method to produce unique bowtie-, flower-, and nest-shaped ZnO particles using zinc nitrate and urea in the presence of polyvinylpyrrolidone (PVP). Three distinct particle morphologies are obtained by adjusting polymer concentration during synthesis. This approach is simple and could enable large-scale production of ZnO particles with diverse shapes. We monitor the morphological evolution of ZnO particles and, at different polymer concentrations, uncover the preferable PVP adsorption onto different ZnO facets that controls the growth directions of ZnO. Previous reports have demonstrated the influence of particle shape on ZnO antibacterial activity. In this study, we show that ZnO particles with these three morphologies exhibit similar bacterial killing efficacy towards Escherichia coli and Staphylococcus aureus. Our detailed mechanistic studies suggest that the antibacterial mechanism of ZnO particles can be attributed to both Zn2+ release and oxidative stress, whereas shape plays only a minor role in the antibacterial activity of ZnO particles.

Nanoporous Polymer Networks of N-Vinylpyrrolidone with Triethylene Glycol Dimethacrylate and Sorption of Macromolecules

Nanoporous polymer networks with different composition are obtained by the 3D radical copolymerization of N-vinylpyrrolidone and triethylene glycol dimethacrylate in the presence of a branched copolymer that acts as a macromolecular template and a pore-forming agent. The processes of adsorption of polyvinylpyrrolidone, poly(methyl methacrylate), and polystyrene from their mixtures in chloroform by the N‑vinylpyrrolidone-based nanoporous polymer network and their desorption are studied. The molecular-weight distribution and composition of PVP–PMMA and PVP–PS mixtures (before and after adsorption) and macroobjects (after desorption) are studied by GPC and IR spectroscopy. A high selectivity of the nanoporous polymer network for the adsorption of polyvinylpyrrolidone from its mixture with nonpolar polystyrene is shown.

Anisotropic Growth of Silver Nanoparticles Is Kinetically Controlled by Polyvinylpyrrolidone Binding.

Polyvinylpyrrolidone (PVP) is used in the synthesis of Ag nanoparticles (NPs) with controlled shape, most commonly producing cubes. The mechanism for shape control is unclear but believed by many to be caused by preferential binding of PVP to Ag(100) facets compared to Ag(111) facets and assumed by most to be the result of thermodynamic control, whereby facets with lower interfacial free energy predominate. To investigate this mechanism, we measured adsorption isotherms of PVP on different-shaped Ag NPs, to determine the thermodynamics of PVP adsorption to Ag(100) and Ag(111) facets. The equilibrium adsorption constant is independent of PVP molecular weight and depends only weakly on NP shape (and thus Ag facet). The equilibrium adsorption constant for PVP on Ag(111) (2.8 M-1) is about half that on Ag(100) (5 M-1). From a Wulff construction, this difference is not nearly enough to produce cubes via thermodynamic control. This result indicates the importance of kinetic control of the Ag nanoparticle shape by PVP, as has recently been proposed.

Competitive Adsorption between a Polymer and Its Monomeric Analog Enables Precise Modulation of Nanowire Synthesis

Summary Capping ligand adsorption and desorption on crystal facets crucially affects the final crystal size and shape. Herein, based on the competitive adsorption of polyvinyl pyrrolidone (PVP) and its monomeric analog, cyclopentanone (CPK), we precisely modulate the synthesis of two different elemental nanowires; i.e., single-crystalline Te nanowires and multiple-twinned Pd nanowires. We discover that the similarity between the molecular structure of CPK and the repeating unit of PVP makes the competitive adsorption between them accessible, and the different desorption rates of PVP and CPK result in different crystal growth inhibition effects (strong for PVP and weak for CPK). Thus, the competitive adsorption between PVP and CPK leads to the precise modulation of the growth of these nanowires, which can be further illustrated by density functional theory. This work presents new opportunities to modulate the synthesis of nanocrystals by competitive adsorption between polymer ligands and their monomeric analogs.

Surface‐enhanced Raman scattering study of PP/Ag nanocomposite developed to prevent postsurgery infection

AbstractWide varieties of antibacterial medical materials coated with silver nanoparticles (AgNPs) are developed. However, studies about coating surgical are scare. Stable coated polypropylene (PP) surgical suture with spherical AgNPs (PP/Ag nanocomposite) was prepared using an optimized aqueous dipping method. Homogenous and linear distribution of AgNPs on the PP surface was verified by scanning electron microscope and atomic force microscopy combined to the bright field image. Quantitative analyses of the silver content were measured by inductively coupled plasma atomic emission spectroscopy and showed a grafting rate of 8 × 10−4%. Surface‐enhanced Raman scattering investigations confirmed the grafting of AgNPs on the surface of surgical suture and highlighted the regioselective adsorption of polyvinylpyrrolidone on the AgNPs via the AgO interactions. Finally, PP/Ag nanocomposite has shown a good stability in biological medium (saline solution NaCl 0.9%) and prominent biocompatibility against human umbilical vein endothelial cells. Antibacterial performances of PP/Ag nanocomposite against gram‐positive and gram‐negative colonies of bacteria were also investigated.

Facile fabrication of Ag nanowires for capacitive flexible pressure sensors by liquid polyol reduction method

The Ag nanowires (AgNWs) were prepared by improved liquid polyol reduction method, and the AgNWs were successfully applied to the capacitive flexible pressure sensors. Firstly, the one-dimensional radial growth conditions of AgNWs were optimized from four aspects of the molecular weight of the protective agent polyvinyl pyrrolidone (PVP), the molar ratio of AgNO3 and PVP, the anion concentration of the metal salt and the reaction temperature. The effect of polymerization degree of protective agent on one-dimensional radial growth of AgNWs was investigated by using three kinds of protective agents PVP-K-30, PVP-K-60 and PVP-K-90. Three different AgNO3 and PVP molar ratios of 1:1, 1:3 and 1:9 were designed, and the effects of PVP adsorption capacity on one-dimensional radial growth of AgNWs were investigated. Three concentrations of 0 mM NaCl, 16 mM NaCl and 32 mM NaCl were designed to study the effects of anion concentration of the metal salt on the nucleation and etching of silver nanoparticles. The effects of reaction temperature on the growth of AgNWs were studied at three different temperatures of 140 °C, 160 °C and 180 °C, and appropriate temperature design was proposed. In this experiment, the products of AgNWs prepared under various conditions were analyzed by UV–vis Spectrum and SEM, and the experimental conditions were optimized from the synthesis mechanism and reaction conditions.