Polyvinyl Alcohol Molecules Research Articles

Investigating the Langevin behaviour of Faraday rotation in soft ferrimagnetic CoFe2O4 nanoparticles dispersed in PVA-water medium

Soft ferrimagnetic (FM) cobalt ferrite, CoFe2O4 (CoF) nanoparticles (NP) were synthesized using chemical co-precipitation technique. The constraint related to forming stable dispersion of the synthesized NP was successfully overcome by using an efficient dispersing medium namely, a 2 Wt% Polyvinyl Alcohol (PVA) - water solution, the PVA molecules of which played an important role in offering excellent stability by preventing the agglomeration of the NP considerably. Magneto-optic Faraday Rotation (MOFR) studies performed on the prepared stable dispersions at 532 nm laser wavelength for applied magnetic fields upto 2400 Oe indicated a Langevin behaviour consistent with the chain/cluster formation in them. The studies were carried out at two different concentrations, where the saturated value of MOFR, Bs , was higher for the more concentrated sample, while the saturation magnetic field, HS , followed the reverse trend. It was interesting to see that HS , was as large as 1800 Oe for the concentrated sample, and still higher for the less concentrated one, which may be due to an obstruction effect due to PVA molecules, which delay the formation and saturation of NP chains. The MOFR studies in soft FM NP dispersions open up an interesting domain, both for fundamental understanding of physical phenomena as well as for applications.

Polarization improvement of perovskite nanowire composite films by mechanical stretching method

Perovskite nanowires (NWs) have attracted considerable interest because of their excellent polarization properties. In this work, we first synthesized colloidal lead halide CsPbBr3 NWs with suitable lengths and excellent polarization performance by the method of the thermal injection. By embedding the NWs in polyvinyl alcohol (PVA) to prepare practical a polymer composite and combining it with the mechanical stretching method, we achieved films with higher polarizing properties. The optimized stretched composite film achieved a polarization degree of 0.4992, which is superior to that of the unstretched one. The stretched PVA molecules are arranged in a straight line, which absorbs the polarized light parallel to the alignment direction, and only allows the polarized light in the vertical direction to pass through. Therefore, the arrangement of the spin-coated NWs combined with the arrangement direction of the PVA molecules led to an improvement in the polarization performance of the composite film. The NWs-PVA-stretched composite films will show important application value in the manufacture of next-generation polarization-sensitive optoelectronic devices and other fields.

The mechanism of influence of polyvinyl alcohol (9 kDa) on the formation of ice crystals in aqueous solutions

Preventing crystallization of the liquid phase during freeze-thawing of cells is one of the main problems that need to be solved for the successful preservation of biomaterial at low temperatures. One highly effective recrystallization inhibitor is polyvinyl alcohol (PVA). However, the mechanisms of its cryoprotective effect have not been finally elucidated. In particular, it is not clear which structural features contribute to the realization of the antirecrystallization properties of PVA in the region of its cryoprotective concentrations. The influence of PVA on solvent crystallization and structural rearrangements of associations of PVA molecules in phosphate-buffered saline (PBS) was experimentally investigated. Solutions of PVA (molecular weight 9 kDa) in PBS were studied by cryomicroscopy and fluorescence spectroscopy methods. It was shown that molecular associations of PVA in PBS undergo a rearrangement of about 0.5−1 wt%, which is accompanied by a change in their size and hydrophilic-hydrophobic properties. PVA also changes the morphological structure of ice upon cooling and prevents crystallization upon heating. It is suggested that the mechanism of the antirecrystallization activity of PVA may be due to the formation of its complexes with the surface of ice crystals.

Roll-to-roll processable MXene-rGO-PVA composite films with enhanced mechanical properties and environmental stability for electromagnetic interference shielding

MXene films promise potential electromagnetic interference (EMI) shielding materials, but poor scalable processability, environmental instability, and weak mechanical properties severely restrict their applications. Herein, we engineer the large-area, high-performance, and compact nacre-like MXene-based composite films through cooperative co-assembly of Ti 3 C 2 T X MXene and reduced graphene oxide (rGO) in the presence of polyvinyl alcohol (PVA). The resulting MXene-rGO-PVA composite films benefit from enhanced bonding strength and extra chain bridging effect of linear PVA molecules enriched with hydroxyl groups. Therefore, the composite film achieves high tensile strength (∼238 MPa) and toughness (∼1.72 MJ m −3 ) while having high conductivity of ∼32 S cm −1 . A significant EMI shielding effectiveness (41.35 dB) is also demonstrated, with an excellent absolute shielding effectiveness of ∼20,200 dB cm 2 g −1 at only 12-μm thickness. Moreover, due to the synergistic effect of multiple components, the composite films maintain a stable EMI shielding performance in harsh environments (sonication, hot/cold annealing, and acid solution) with mechanical properties that fluctuate only within 10% compared to the original film. More importantly, commercial polyethylene terephthalate release liner can be applied for the film coating, facilitating continuous roll-to-roll production of large-area films and future applications.

A High-Voltage Gel Electrolyte with a Low Salt Concentration for Quasi-Solid-State Flexible Supercapacitors

Safe and eco-friendly aqueous electrolytes with wide electrochemical stability windows (ESWs) and wide temperature operating windows play a vital role in the development of high-energy and sustainable energy storage devices. In this study, we demonstrate a gel-type aqueous lithium bis-trifluoromethanesulfonimide (LiTFSI) electrolyte using glycerol as a cosolvent and polyvinyl alcohol (PVA) as a gel-forming agent. Adding water-miscible glycerol and PVA greatly decreases the number of “free” water molecules due to the H-bond interactions between water–glycerol and water–PVA molecules and suppresses the water splitting reaction. Thus, the ESW of aqueous electrolytes with low LiTFSI concentrations is significantly extended. Gel-type electrolytes with a low LiTFSI concentration of only 2m can achieve an ESW of 3.0 V, which is equivalent to an ESW value of 21m for LiTFSI aqueous solution without glycerol and PVA (superconcentrated or “water-in-salt” LiTFSI electrolyte). In addition, the temperature operating window is from −20 to +60 °C, which is much wider compared to that of the liquid 21m LiTFSI electrolyte. We assemble quasi-solid-state flexible supercapacitors using carbon nanotube sponge as the electrode and a gel-type LiTFSI electrolyte. The quasi-solid-state supercapacitors exhibit an actual operational voltage of 2.4 V, excellent flexibility, thermal stability, and good electrochemical performance at a low LiTFSI concentration in electrolytes.

Using polyvinyl alcohol-ionic hydrogels containing a wound healing agent to manage wounds in different environments.

To explore the effects of pH on properties of polyvinyl alcohol (PVA)-ionic hydrogels containing wound healing promoters. PVA was combined with a natural wound healing promoter (silk sericin (SS)), and an anionic agent (eosin (ES)) or cationic agent (methylene blue (MB)), and made into hydrogels. Properties of the hydrogels and behaviour at different pHs were investigated. The density and gel fraction of PVA/SS-ES hydrogel and PVA/SS-MB hydrogel were considerably lower compared with hydrogel without SS. The swelling ratio and degradation of the hydrogels increased with increasing SS concentration in all pH solutions. The influence of SS in interrupting long-chain PVA molecules was confirmed based on changes in Fourier-transform infrared spectroscopy (FTIR). The SS released from the gels was found to interact with the ionic agent and influenced the release profile of the ionic agent. Surprisingly, the anionic agent in PVA/SS-ES hydrogel showed 70% release in high pH solution whereas the cationic agent in PVA/SS-MB hydrogel showed 86% release in low pH solution. Moreover, the active agent could accumulate on the skin layer and had a positive effect on a specific wound area. Based on the results obtained in this study, it is suggested to use anionic hydrogels containing wound healing promoter for wounds at high pH and cationic hydrogels containing wound healing promoter for wounds with low pH. Ability to improve wound healing using a natural healing agent combined with ionic agents and controlling the pH of hydrogels will help in developing quick and low-cost treatment for wounds.

A Water-Soluble Epoxy-Based Green Crosslinking System for Stabilizing PVA Nanofibers.

With the ever-growing concern about environmental conservation, green production and water-based nanofibers have attracted more and more interest from both academic and industrial fields; nevertheless, the stabilization process of water-based nanofibers is primarily relying on the application of organic solvent-based crosslinking agents. In this work, we develop a green approach to fabricate water-resistant polyvinyl alcohol (PVA) nanofibers by using a water-based epoxy compound, N1, N6-bis(oxiran-2-ylmethyl) hexane-1,6-diamine (EH), as the crosslinker. This EH/sodium carbonate/sodium bicarbonate (CBS) solution system can break down large aggregates of PVA molecules into small ones and promote the uniform distribution of EH in the solution, resulting in the improved stability of crosslinked PVA nanofibers. We firstly report that the uniform dispersion of crosslinking agents in the electrospinning solution plays a vital role in improving the stability of spinning solutions and the water resistance of crosslinked PVA nanofibers by comparing crosslinking performances between water-based epoxy and conventional water-based blocked isocyanate (BI). This work could open up a novel strategy and green approach for the stabilization of water-based nanofibers.

Influence of ultraviolet radiation on structural and uniaxial tensile characteristics of tannic acid/poly (vinyl alcohol) composite films

AbstractThis study investigated the influence of UV‐radiation on structural and uniaxial tensile properties of tannic acid (TA)/polyvinyl alcohol (PVA) composite films. All the samples were exposed to UV light. It was observed that TA reinforced the structure of PVA and its uniaxial tensile properties, as TA concentration increased thanks to the formation of crosslinking between TA and PVA molecules. From X‐ray diffraction (XRD) measurements, it was seen that TA had a better protective effect on ordered structures such as crystallites against UV irradiation than that of PVA films, because the crystallinity of TA/PVA films did not change much. Major degradation effect of UV‐radiation was seen on the amorphous flexible PVA chains and structure. As a result of photodegradation process leading to possibly breakage in the polymer chains in especially amorphous structure, the extensibility or strain at break values of both pure PVA and TA/PVA composite films was decreased dramatically. However, because decrease in the strain at break values for 5% and 10% TA content is less than that for 15% and 20% TA content, the 5% and 10% TA content can be regarded as optimum values, when the protective role of TA against UV irradiation was considered in the studied films.

Preparation and characterization of silk fibroin-polyvinyl alcohol (PVA) blend films for food packaging materials

The present research work deals with the characterization of blend films obtained by mixing silk fibroin (SF) [Bombyx mori CSR4] and Poly Vinyl Alcohol (PVA) in various proportions, considering its potential applicability in the food-packaging industry. The structural, chemical, mechanical and thermal property as well as surface morphologies of blend films were investigated by X-ray diffraction (XRD), Fourier transform InfraRed spectroscopy, universal testing machine, thermogravimetric analysis, differential scanning calorimetry and scanning electron microscope. The SEM results clearly show the proper miscibility of SF and PVA molecules to give a uniform nice surface to the blend films. The physical and thermal properties of the blend films are enhanced significantly compared to the pure silk fibroin films, with more than 100 percentage elongation at break for few blend films. The SF-PVA blend films are more flexible and thermally stable, and hence a good candidate for food packaging material.

DEWATERING HYDROCARBON BASED ON SMART HYDROPHILIC SPONGE AND HYDROPHILIC GEL

Sponge based on polydimethylsiloxane (PDMS) with a high-capacity, ZnCl2, Polyvinyl alcohol (PVA), and Polyethylene Glycol (PEG) for the dewatering application of hydrocarbon fuel sorbents has been prepared in one-step preparation. The synthesized hydrophilic sponges were named V1 (PDMS: ZnCl2), V2 (PDMS: ZnCl2: PVA), V3 (PDMS: ZnCl2: PEG), V4 (PDMS: ZnCl2: PVA: PEG), V5 (PDMS: 2ZnCl2: PVA: PEG) and V6 (PDMS: 3ZnCl2: PVA: PEG), respectively. The characteristics of the sponges under the optical microscope and contact angle measurements show the formation of hydrophilic sponge and gel. ATR-FTIR characterization showed peaks at 3100- 3500 cm-1 and 1750-1735 cm-1 identified with the OH stretching vibration and C=O strain vibration, which can be ascribed to the acetate group of the PVA molecule which is responsible for increasing the hydrophilicity. On the addition of PEG, there is an absorption band from the C-H vibration at 941 cm-1, and absorption at 1459, 1351, 1299, and 1256 cm-1 is CH, CH2, and CH3 bending vibrations. The contact angle measurements showed that the solid hydrophilic sponge V4 has a hydrophilic character (contact angle of 45.5º). And also, the increase in ZnCl2 was proportional to the decrease in contact angle. However, in the composition of V5 and V6, the super hydrophilic character (V5 =38.8º, V6 =14.3º) did not produce a good solid hydrophilic sponge. Characteristics of optical properties show high transmittance of more than 80%.

Impacts of polyols and temperature on the micellization, interaction and thermodynamics behavior of the mixture of tetradecyltrimethylammonium bromide and polyvinyl alcohol

Abstract Herein, the aggregation manner of the mixture of polyvinyl alcohol (PVA) and tetradecyltrimethylammonium bromide (TTAB) was performed in polyols (glucose, maltose and galactose) media over 300.55–320.55 K temperatures range with 5 K interval through conductivity measurement method. The micelle formation of TTAB + PVA mixture was identified by the assessment of critical micelle concentration (CMC) from the plots of specific conductivity (κ) versus TTAB concentration. The degree of micelle ionization (α), the extent of bound counter ions (β) as well as thermodynamic properties ( Δ G m 0 ${\Delta}{G}_{m}^{0}$ , Δ H m 0 ${\Delta}{H}_{m}^{0}$ and Δ S m 0 ${\Delta}{S}_{m}^{0}$ ) of TTAB + PVA systems have been estimated. The CMC values reveal that the micelle formation of TTAB + PVA mixture experience an enhancement in the manifestation of polyols. The values of free energy of micellization ( Δ G m 0 ${\Delta}{G}_{m}^{0}$ ) are negative for the TTAB + PVA system in aqueous polyols media, suggesting a spontaneous aggregation phenomenon. The Δ H m 0 ${\Delta}{H}_{m}^{0}$ and Δ S m 0 ${\Delta}{S}_{m}^{0}$ values of TTAB + PVA systems direct that the PVA molecule interacts with TTAB through the exothermic, ion-dipole, and hydrophobic interactions. The thermodynamic properties of transfer were also determined for the move of TTAB + PVA mixture from H2O to water + polyols mixed solvents. The values of compensation temperature (T c) and intrinsic enthalpy gain ( Δ H m 0 , ∗ ${\Delta}{H}_{m}^{0,\ast }$ ) were evaluated and discussed for the studied system.

Highly Reversible Zn Plating/Stripping Enabled by Polyvinyl Alcohol Coating Layers for Stable Aqueous Rechargeable Zinc Batteries

Given their intrinsic safety, low cost, and high energy density, aqueous zinc (Zn) batteries hold substantial promise in large-scale energy storage applications. However, Zn dendrite formation and serious side reactions in metallic Zn anodes significantly compromise the reversibility of electrochemical Zn plating/stripping, restricting their lifespan and practical applications. Herein, we demonstrate that the polyvinyl alcohol (PVA) coated Zn anode can alleviate those issues. The PVA molecules at the Zn anode/electrolyte interface enable homogeneous Zn plating/stripping behavior by regulating the nucleation and ion diffusion barriers and effectively suppress the corrosion and hydrogen evolution reaction in mildly acidic electrolytes. As a result, a highly reversible and dendrite-free Zn anode can be obtained. The content of PVA plays a critical role in governing the cycling lifetime and stability. With the optimized content of PVA, stable Zn plating/stripping with a cycling capacity of 1 mAh cm-2 over 1500 hours has been achieved at 1 mA cm-2. In contrast, the bare Zn anode showed an unstable plating/stripping behavior with obvious polarization and limited cycling lifetime. Even at a high current density of 5 mA cm-2, the PVA-coated Zn anode remained stable for 1000 cycles. The present work provides a promising strategy to stabilize Zn anodes towards long-lifespan, cost-effective, and scalable aqueous rechargeable zinc-based batteries.

Interfacial thermal conductance enhancement of BN/PVA composites via plasma activations of fillers

Polymeric composite materials for heat management play a key role in electronic packaging, yet they usually suffer from the interfacial thermal resistance when using ceramic fillers. The interfacial incompatibility and debonding between fillers and matrices are identified as the culprit. Boron nitride (BN) is an advanced thermal conductive filler, whereas it also suffers from the interfacial problem owing to its chemical inertia and hydrophobicity. Herein, some plasma activations are introduced to well functionalize BN, which significantly changes BN from hydrophobicity to hydrophilicity. The interfacial bonding is thus achieved between the plasma-treated BN fillers and the polyvinyl alcohol molecules. The BN/polyvinyl alcohol composite material shows a high through-plane thermal conductivity of 2.4 W m−1 K−1 for a filling fraction of 50 wt% BN treated by N2 plasma, which is much better than the raw BN case. It is thus envisaged as a promising approach for the high-efficiency and low-cost fabrication of BN-based composite materials.

Iron Oxide Nanoparticles Assisted Arsenic, Mercury, And Cadmium Removal From Aqueous Solution

يمكن أن تلعب الجسيمات النانوية لأكسيد الحديد (IONPs) دورا مهما في إزالة المعادن الثقيلة من المحلول الملوث. كما (ثالثا) من المياه الملوثة بالزرنيخ. في هذا العمل ، قمنا بتصنيع IONPs باستخدام طريقة كيميائية تتضمن تشتت Fe 3+ أكدت الأيونات من خلال جزيئات بوليمر من كحول بولي فينيل (PVA) في تحليل حيود الأشعة السينية (XRD) المائي تشكيل بنية بلورية أحادية الطور ، وكان حجم الجسيمات النانوية 50-100 نانومتر. الصور المجهرية الإلكترونية للإرسال تتكون من نتيجة IONPs (50-100 نانومتر). تمت دراسة امتزاز As (III) و Hg (II) و Cd (II) On (IONPs) باستخدام أربع معلمات لوقت التلامس والتركيز وجرعة IONPs وتم تحقيق توازن امتصاص الأس الهيدروجيني في 100 دقيقة والحد الأقصى لإزالة As (III). ) عند درجة الحموضة (6-6.5). أشار تحليل متساوي الحرارة إلى أن بيانات الامتصاص يتم ترشيحها بشكل أفضل لنموذج متساوي الحرارة Langmuir. كانت قدرات امتصاص أقصى 101.2، 73.10 و 60.05 ملغ ز _1 لو(III) والزئبق (II) والكادميوم (II)، على التوالي. Abstract – Iron oxide nanoparticles (IONPs) can play a significant role in the removal of heavy metal from contaminated solution .Aresnite ,As(III) highly toxic,mobile and predominant species in arsenic contaminated water IONPs have been synthesized, characterized and tested for the removal of As(III) from arsenic contaminated water. In this work , we synthesized IONPs using a chemical method involving dispersion of Fe 3+ ions through polymer molecules of poly vinyl alcohol (PVA) in aqueous medium X-ray diffraction (XRD) analysis confirmed the formation of a single phase rhomobohrdral crystal structure, the size of nanoparticles was 50-100 nm. Transmission electron microscopic images corborate the result of IONPs (50-100 nm) . The adsorption of As(III),Hg(II) and Cd(II) On (IONPs) was studied using four parameters contact time, concentration, dose of IONPs and pH Adsorption equilibrium was achieved in 100 min and maximum removal of As(III) was obtained at pH (6-6.5) . The isotherm analysis indicated that the adsorption data better filted to the Langmuir isotherm model. The maximum adsorption capacities were 101.2, 73.10 and 60.05 mg g _1 for As(III), Hg(II) and Cd(II), respectively. Keywords – Iron Oxide, Nanoparticles, Arsenic, Mercury, Cadmium.

Electrohydrodynamic‐Printed Polyvinyl Alcohol‐Based Gate Insulators for Organic Integrated Devices

Organic printable dielectric layers are required for next‐generation electronic circuits, particularly those used as gate insulators (GIs) in organic field‐effect transistors (OFETs). Herein, optimized electrohydrodynamic (EHD) jet printing with an electrostatic force‐assisted mode is suggested for the fabrication of polyvinyl alcohol (PVA)‐based dielectric patterns after careful consideration of the ink system. The PVA molecules maintain good solubility in polar solvents, even when a crosslinking agent is added, which enables a continuous PVA jet stream with a width smaller than the diameter of the nozzle to be stably obtained. Subsequent EHD printing produces uniform PVA patterns with a smooth surface morphology suitable for the crystal growth of overlying organic semiconductors. The addition of a crosslinking agent in PVA results in direct GI patterns that exhibit superior insulating properties with high dielectric strength as compared with PVA without crosslinking agents. The OFETs with PVA‐based GIs prepared with EHD printing show stable operation with low gate leakage currents. In addition, the feasibility of EHD‐printed PVA layers is demonstrated for application as GIs in organic complementary logic gates.

Preparation and properties of PVA/SS/AgNPs composite nanofibres

Polyvinyl alcohol (PVA), PVA/silk sericin (SS) and PVA/SS/AgNPs (nano-silver) solutions have been prepared, and the nanofibres are produced by electrospinning technology. The nanofibres are then tested using scanning electron microscopy (SEM), Fourier transform infrared spectroscopy (FTIR) and X-ray diffraction (XRD). The results show that the morphology of 7-11 wt% PVA nanofibres is fine and smooth. With the increase in SS and AgNPs contents, the average diameter of PVA/SS and PVA/SS/AgNPs composite nanofibres is increased. The FTIR spectra and XRD patterns of PVA/SS/AgNPs composite nanofibres with different mass ratios have the similar regular curves. The intensity of the infrared peak of PVA/SS/AgNPs composite nanofibres weakens at 837, 1087, 1648 and 2914 cm -1 with the increase in AgNPs; the intensity of the diffraction peak gradually increases at 13.1 o and weakens at 19.09 °. This may be due to the reason that Ag interacts with PVA and SS molecules. The findings are of great significance for the development of nano-scale antibacterial fibres.

Effect of composition of mono/di-hydroxy organic compounds and temperature on the aggregation behavior and physico-chemical properties of polyvinyl alcohol + TTAB mixture

Herein, the aggregation manners of polyvinyl alcohol (PVA) with tetradecyltrimethylammonium bromide (TTAB) in alcohols/diols media containing various concentrations and at several temperatures were performed using the conductivity measurement technique. Different physico-chemical parameters, such as critical micelle concentration (CMC), fraction of bound counter ions (β) and thermodynamic properties (ΔGo m, ΔHo m, ΔSo m, and ΔCo m) for the TTAB + PVA mixture in aqueous solutions of EtOH (EtOH), 1-propanol (1-PrOH), ethylene glycol (EG), and propylene glycol (PrG), have been determined. The CMC values were found to undergo a decrease in 1-PrOH in comparison to the values obtained in aqueous media, but in EtOH, the CMC value firstly decreases, touches the lowest point, and then exhibits an upsurge with further increase of the percentage of EtOH. The observed greater CMC values in diols media disclose that the micelle formation of TTAB + PVA mixture is delayed in the manifestation of diols. The CMC values of TTAB + PVA mixture have also been observed to vary with the change of study temperature. The negative values of ΔG0 m were obtained for all circumstances suggesting a spontaneous aggregation phenomenon of TTAB + PVA system. The values of ΔH 0 m and ΔS0 m dictate that the PVA molecule interacts exclusively with TTAB through the formation of hydrogen bonding, ion-dipole, and hydrophobic interaction. Furthermore, the standard molar heat capacity (ΔC 0 m), compensation temperature (T c), intrinsic enthalpy gain (ΔH 0,* m), and the thermodynamic properties of transfer (ΔG 0 m.tr, ΔH 0 m.tr. and ΔS 0 m.tr.) for the studied system were assessed and demonstrated with appropriate explanations.

Ultralight graphene oxide/polyvinyl alcohol aerogel for broadband and tuneable acoustic properties

An ultralight graphene oxide (GO)/polyvinyl alcohol (PVA) aerogel (GPA) is proposed as a new class of acoustic materials with tuneable and broadband sound absorption and sound transmission losses. The interaction between GO sheets and PVA molecules is exploited in our environmentally friendly manufacturing process to fabricate aerogels with hierarchical and tuneable porosity embedded in a honeycomb scaffold. The aerogels possess an enhanced ability to dissipate sound energy, with an extremely low density of 2.10 kg m−3, one of the lowest values ever reported for acoustic materials. We have first experimentally evaluated and optimised the effects of composition and thickness on the acoustic properties, namely sound absorption and sound transmission losses. Subsequently, we have employed a semi-analytical approach to evaluate the effect of different processing times on acoustic properties and assessed the relationships between the acoustic and non-acoustic properties of the materials. Over the 400–2500 Hz range, the reported average sound absorption coefficients are as high as 0.79, while the average sound transmission losses can reach 15.8 dB. We envisage that our subwavelength thin and light aerogel-based materials will possess other functional properties such as fire resistance and EMI shielding, and will prove to be novel acoustic materials for advanced engineering applications.

Molecular dynamics and experimental study on the adhesion mechanism of polyvinyl alcohol (PVA) fiber in alkali-activated slag/fly ash

This paper aims to study the adhesion mechanism of polyvinyl alcohol (PVA) fiber within alkali-activated slag/fly ash (AASF) matrix using molecular dynamics (MD) simulation in combination with systematic experimental characterization. The adhesion of PVA to C-(N-)A-S-H gel with different Ca/(Si+Al) and Al/Si ratios was modeled using MD simulation, with the related adsorption enthalpy calculated and the adhesion mechanism explored. The experimentally attained chemical bonding energy of PVA fiber in AASF coincides well with the simulation results. In both cases, the adhesion enhances primarily with increasing Ca/(Si+Al) ratio of C-(N-)A-S-H gel. Additionally, MD simulation indicates preferential element distributions of Ca around PVA molecule, which was confirmed experimentally by the detection of the Ca-rich C-(N-)A-S-H gel in the interfacial transition zone (ITZ).This study provides further insights into the adhesion mechanism of PVA fiber to C-(N-)A-S-H gel formed in AASF, which is particularly valuable for the future development of PVA-based high-performance alkali-activated composites.

Concentration of Capping Agent Controls Size Selection, Agglomeration and Antimicrobial Action of Silver Nanoparticles

Polyvinyl Alcohol (PVA) capped Ag nanoparticles (AgNPs) formed through reduction of Silver Nitrate (AgNO3) by Sodium Borohydride (NaBH4) were studied for different PVA concentrations (C, %w/w of solution) in the bulk. Diameter (DAg) of Ag metallic core, obtained from plasmon resonance in Ultraviolet-Visible spectra, had a peak (≈12.8 nm) at C~0.24, which almost exactly matched the gyration sphere diameter of PVA molecule (∼13 nm). Cluster diameter (Dcl), measured after a month through Dynamic Light Scattering (DLS) study, gave the number of NPs per cluster showing a dip at C∼0.24. Minimum inhibitory concentration (MIC) of AgNPs on Escherichia coli (E. coli), assayed from standard broth dilution method (CLSI M07-A8), showed MIC of 0.66 μg/ml at the PVA concentration of 0.24%. Scanning Electron Microscopy (SEM) showed NP clusters accumulating over E. coli to have Dcl ∼ DAg whereas those lying outside the bacteria to have Dcl ∼ 3DAg, consistent with a strong size selectivity of antimicrobial efficacy.