Presence Of Polyvinyl Alcohol Research Articles

Spectrophotometric determination of magnesium in the presence of polyvinyl alcohol

Spectrophotometric determination of magnesium in the presence of polyvinyl alcohol

Current-Transport Mechanisms of the Al/(Bi2S3-PVA Nanocomposite)/p-Si Schottky Diodes in the Temperature Range Between 220 K and 380 K

In this research, bismuth sulfide nanostructures were prepared in the presence of polyvinyl alcohol (PVA) as a capping agent by an ultrasound-assisted method. The x-ray diffraction results show the crystalline phase of the sample and the mean crystalline size estimated by Debye–Scherer’s equation. The UV–Vis absorption spectrum show that the optical absorbance edge of Bi2S3 nanostructure was blue-shifted. The Fourier transform infrared spectra confirm the presence of PVA in the sample and transmission electron microscopy imaging shows that the structures are in nanoscale. The semi-logarithmic forward bias I–V plots have two distinct linear regimes for each temperature which are called low- and moderate-bias regions (LBR and MBR). In order to effectively interpret possible current-conduction/transport mechanisms, the reverse saturation current (Io), ideality factor (n) and zero-bias barrier height (ΦBO) were obtained from the slope and intercept of these plots and they were found to be a strong function of temperature and voltage. The high value of n even at high temperature and the increase of ΦBO with increasing temperature for the two regions is clear evidence of the deviation from thermionic emission (TE) theory. Therefore, ΦBO versus n and q/2kT plots were drawn to get evidence of the Gaussian distribution (GD) of the barrier height (BH) and they show a linear behavior. The mean values of BH ( $$ \bar{\Phi }_{\rm{BO}} $$ ) and standard deviation (σs) were also obtained from the intercepts and slopes of the ΦBO versus q/2kT plots as 1.44 eV and 0.19 V for the LBR and 1.32 eV and 0.18 V for the MBR, respectively. After that, the values $$ \bar{\Phi }_{\rm{BO}} $$ and effective Richardson constant (A*) were obtained as 1.29 eV and 267.6 A/(cm K)2 for the LBR and 1.27 eV and 281.7 A/(cm K)2 for the MBR, respectively. Such non-ideal I–V–T characteristics for the Al/(PVA-Bi2S3)/p-Si structure can be successfully explained by the single GD of BH for the LBR and MBR.

Facile tool for green synthesis of graphene sheets and their smart free-standing UV protective film

Green, cost-effective and scalable method was developed for synthesis of graphene sheets from sugar beet leaves. Considerable graphene sheets were synthesized through drying, and carbonization of sugar beet leaves then, exfoliation from the obtained graphite flakes using ultrasonication in presence of polyvinyl alcohol (PVA). High quality less defected and large dimensions graphene sheets of 50% yield were obtained. The mass ratios of PVA and their effect on exfoliation were studied. Free-standing transparent graphene sheets thin film was developed of an average thickness of 136 µm. The transparent free-standing graphene sheets thin film transparent to visible rays and blocked harmful UV rays by ∼70% which is among the highest reported value for UV protective thin film. To the best of our knowledge this the first time of free-standing transparent graphene sheets film prepared from renewable source and used as UV filter. This work will open new avenues for using renewable and cost-effective UV protective materials and filters.

Determining electrical and dielectric parameters of Al/ZnS-PVA/p-Si (MPS) structures in wide range of temperature and voltage

In this study zinc sulphide (ZnS) nanostructures have been prepared by microwave-assisted method in presence of polyvinyl alcohol (PVA) as a capping agent. The structural and morphological properties of prepared sample have been investigated by X-ray diffraction (XRD) and scanning electron microscopy (SEM). These analyses confirm that the sample has nano structure. They have been used this sample to fabrication of Al/ZnS-PVA/p-Si structure. The effect of temperature and voltage on the electrical and dielectric parameters of the Al/ZnS-PVA/p-Si (MPS) structures has been investigated in the wide range of temperature (140–340 K) and voltage (− 2 V to + 4 V) using capacitance/conductance-voltage (C/G–V) measurements at 500 kHz. Experimental measurements revealed that the values of C/G–V increase with increasing temperature but the values of series resistance (Rs) increase with decreasing temperature. As well as the dielectric parameters such as the values of real and imaginary parts of the dielectric constants (e′ and e″) and electric modules (M′ and M″), loss tangent (tanδ), and ac electrical conductivity (σac) were obtained using C and G/ω data. These parameters are found out as strong functions of temperature and voltage. While the values of e′, e″ and tanδ increase with increasing temperature, the values of σac, M′ and M″ decrease. The Arrhenius plot (ln(σac) vs q/kT) shows two distinct linear ranges with different slopes or activation energies (Ea) at low (140–230 K) and high (260–340 K) temperatures. Both values of Rs and (ZnS-PVA) interfacial layers are also very effective parameters on the electric and dielectric properties.

Influence of ultrasound and template on the properties of nickel hydroxide as an active substance of supercapacitors

Nickel hydroxide is widely used as an active material s of supercapacitors. The most active are Ni(OH) 2 (α+β) samples with layered structure synthesized in a slit-diaphragm electrolyzer. The study on the influence of template synthesis and ultrasound treatment on the characteristics of the samples was conducted. The synthesis of nickel hydroxide samples in the presence of polyvinyl alcohol as a template and the use of ultrasound treatment of the Ni(OH) 2 suspension directly after formation was carried out. The synthesized samples of nickel hydroxide were studied by means X-ray diffraction analysis, scanning electron microscopy, and BET nitrogen adsorption-desorption. Electrochemical characteristics were evaluated by means of galvanostatic charge-discharge cycling in the supercapacitor regime. Comparative analysis of the Ni(OH) 2 sample has revealed both negative and positive effect of the template and ultrasound. The use of PVA as a template and ultrasound treatment resulted in a significant decrease in specific surface area (to 6 m 2 /g) and an increase of the average pore diameter (to 1181 Ǻ). Application of the template and ultrasound decreases crystallinity and increases the content of α-form, which results in the increased capacity of the samples. The maximum value of 233 F/g is achieved at a current density of 40 mA/cm 2 obtained from the combined effect of the template and ultrasound. Under these conditions, the specific capacity of the sample prepared without the template and ultrasound is 76 F/g. However, with an increase of current density to 120 mA/cm 2 , the capacity of this sample increases to 303 F/g. At the same time, for samples synthesized with the template and ultrasound, a decrease of capacity is observed at higher current densities, which is related to difficulties in the breakdown of agglomerated particles. In case of the introduced template, this is explained by the binding effect of the remaining PVA and in case of ultrasound treatment – particle condensation. Based on the results of the comparative analysis, it is recommended to replace the template with a more easily removable one and also conduct an electrochemical synthesis of Ni(OH) 2 in SDE directly in the ultrasound field and increase the power of the emitter.

Preparation of Lead Oxide Nanostructures in Presence of Polyvinyl Alcohol (PVA) as Capping Agent and Investigation of Their Structural and Optical Properties

Preparation of Lead Oxide Nanostructures in Presence of Polyvinyl Alcohol (PVA) as Capping Agent and Investigation of Their Structural and Optical Properties

Novel Magnetic Zinc Oxide Nanotubes for Phenol Adsorption: Mechanism Modeling.

Considering the great impact of a material’s surface area on adsorption processes, hollow nanotube magnetic zinc oxide with a favorable surface area of 78.39 m2/g was fabricated with the assistance of microwave technology in the presence of poly vinyl alcohol (PVA) as a stabilizing agent followed by sonic precipitation of magnetite nano-particles. Scanning electron microscopy (SEM) and transmission electron microscopy (TEM) micrographs identified the nanotubes’ morphology in the synthesized material with an average aspect ratio of 3. X-ray diffraction (XRD) analysis verified the combination of magnetite material with the hexagonal wurtzite structure of ZnO in the prepared material. The immobilization of magnetite nanoparticles on to ZnO was confirmed using vibrating sample magnetometry (VSM). The sorption affinity of the synthesized magnetic ZnO nanotube for phenolic compounds from aqueous solutions was examined as a function of various processing factors. The degree of acidity of the phenolic solution has great influence on the phenol sorption process on to magnetic ZnO. The calculated value of ΔH0 designated the endothermic nature of the phenol uptake process on to the magnetic ZnO nanotubes. Mathematical modeling indicated a combination of physical and chemical adsorption mechanisms of phenolic compounds on to the fabricated magnetic ZnO nanotubes. The kinetic process correlated better with the second-order rate model compared to the first-order rate model. This result indicates the predominance of the chemical adsorption process of phenol on to magnetic ZnO nanotubes.

New derivatives of (E,E)-azomethines: Design, quantum chemical modeling, spectroscopic (FT-IR, UV/Vis, polarization) studies, synthesis and their applications: Experimental and theoretical investigations

In present work, Polarization, Excited States, FT-IR, 1H, 13C NMR, Trans–Cis (E → Z) Isomerization Properties and Anisotropy of Thermal and Electrical Conductivity of the three new Azomethines dyes such as: 4-((E)-((4-((E)-phenyldiazenyl)phenyl)imino)methyl)benzoic acid (I), 5-phenyl-N-(pyrimidin-2-yl)isoxazole-3-carboxamide (II) and (Z)-1-(4-((E)-((4-phenylcyclopenta-1,4-dien-1-yl)methylene)amino)phenyl)ethanone oxime (III) in the presence of polyvinyl alcohol (PVA) matrix were studied. The absorption spectrum of the I, II and III in dimethylformamide (DMF) solution was calculated. The nature of absorption peaks of the dyes in the UV/Vis spectral regions was interpreted. The molecular HOMO-LUMO, excitation energies and oscillator strengths for E and Z isomers of the I, II and III have also been calculated and presented. Optical Properties of the PVA-films containing these new synthesized dyes have investigated. Polarizing Efficiency (PE) of obtained PVA-film is 97–98% at Stretching Degree (Rs) 3.5. Anisotropy of thermal and electrical conductivity of the PVA-films containing the title compounds was also measured and discussed.

Kinetic parameters of anodic oxidation of methanol in alkali: Effect of diameter of Pd nano-catalyst, composition of electrode and solution and mechanism of the reaction

Palladium nanoparticles with varying particle diameter (6.9–25.1 nm) have been synthesized by single-pot wet chemical technique in presence of poly vinyl alcohol by controlling the duration of reflux. The resulting nanoparticles have been dip-coated on Ni-foil, followed by determination of kinetic parameters of the anode-catalysts in reference to alkaline oxidation of methanol (AOM) by electrochemical and IR-spectroscopic techniques. The morphology and surface characteristics of the Pd nano-catalyst have been investigated by electron microscopy in conjugation with energy dispersion spectroscopy. The results show the formation of formate and carbonate with no change in selectivity but improved kinetic parameters on decreasing the diameter of constituting Pd nanoparticles. The studies of cyclic voltammetry of methanol, formaldehyde and formate reveal that the electrode constituted with Pd nanoparticles having average diameter of 6.9 nm obtained by applying the lowest time (0.33 h) of reflux, is the best for all the fuels. The studies also help understanding the stability of the electrodes, proposition of the intermediates and plausible mechanism of the reaction.

Effects of synthetic polymers on in vitro maturation of sheep oocytes and subsequent developmental capacity after parthenogenetic activation or fertilization

There are few studies considering functional roles of synthetic polymers on small ruminant oocytes matured in vitro. In this study, the effects of polyvinyl alcohol (PVA) and polyvinylpyrrolidone (PVP) on in vitro maturation of sheep oocytes were evaluated and compared in order to determine whether synthetic polymers can replace serum and be used for in vitro maturation of sheep oocytes. Simultaneously, the effects of synthetic polymers presented in the maturation medium on subsequent embryonic development were also assessed. Sheep cumulus−oocyte complexes were cultured in the maturation medium supplemented with 10% fetal bovine serum (FBS), 3mg/ml PVP, or 1mg/ml PVA, respectively. The rates of oocyte maturation and embryonic development after parthenogenetic activation (PA) or in vitro fertilization (IVF) were recorded. The data indicated that the presence of PVP in the maturation medium does not have any negative effects on sheep oocytes matured in vitro when compared to FBS, as concern oocyte maturation and subsequent embryonic developmental capacity. Additionally, after PA, the embryonic developmental capability of in vitro matured sheep oocytes in the presence of PVA was not significantly different from that of oocytes matured in the presence of FBS or PVP. By contrast, when PVA was added to the maturation medium, the blastocyst formation rate after IVF (28.05%±5.42%) was significantly lower than that of oocytes matured in the presence of FBS (36.33±4.37%, P<0.05) or PVP (38.94±5.19%, P<0.05). However, there were no significant differences in the oocyte cleavage rate among the three groups. Additionally, the embryonic developmental capacity in the PVP group were similar to those in the FBS group (P>0.05). In conclusion, synthetic polymer as a serum replacement can efficiently maintain the procedure of oocyte maturation and subsequent embryonic developmental capacity in sheep. The PVP is more beneficial to in vitro maturation of sheep oocytes compared to PVA.

Exfoliation and Decoration of Graphene Sheets with Silver Nanoparticles and Their Antibacterial Properties

High quality graphene sheets (GRP) have been exfoliated using facile one pot method through direct ultrasonication of graphite in the presence of polyvinyl alcohol. The GRP were decorated with silver nanoparticles (AgNPs) producing graphene–silver nanoparticle composites. The effect of variation of graphite and silver salt mass ratios on the morphology and performance of produced composites was studied. The size of AgNPs decorated on GRP has been tuned with synthesis method optimization. The average size of AgNPs was found to be in the range of 8.6–15.6 nm. Cotton–polyester blend textile fabrics were treated with the new smart developed composite as antibacterial agent producing new composites. A significant inhibition of bacterial growth has been observed for graphene–silver nanoparticle composite and the antibacterial efficiency was optimized. The clear inhibition zone for textiles treated with new developed composite and AgNPs alone was recorded as 12 and 1.75 mm respectively, achieving more than six fold improvement.

Selection and optimization of nano-formulation of P-glycoprotein inhibitor for reversal of doxorubicin resistance in COLO205 cells.

The prime objective of current work was to develop a strategy for preparation of combinational nano-formulation for reversal of drug resistance. As a model system, doxorubicin (DOX)-resistant COLO205 cells were developed and validated. From co-treatment studies with DOX, curcumin was selected as it reversed DOX-resistance at lowest concentration. In an attempt to increase its solubility, curcumin was encapsulated into hydroxypropyl-β-cyclodextrin (HP-β-CD). Here, we propose that presence of stabilizer overcomes its low encapsulation efficiency. Thus, we evaluated curcumin encapsulation in HP-β-CD in presence of different stabilizers and organic solvents. Finally, the effect of nanocurcumin with liposomal DOX was studied for reversal of resistance in COLO205 cells. In the process encapsulation, selective optimization of organic solvent by freeze-drying was found to be appropriate among other methods. From optimization studies with different organic solvent (acetone and dichloromethane) and stabilizer [polyvinyl alcohol (PVA) and Pluronics], HP-β-CD-encapsulated curcumin prepared using acetone in PVA-stabilized dispersion increased encapsulation (60%) with size of ~40nm. Prepared nano-curcumin reversed the DOX resistance effectively in combination with liposomal DOX. Curcumin reversed DOX resistance in COLO205 cells at low concentration and enhanced curcumin encapsulation in HP-β-CD was noted in presence of PVA. Further, it was observed that prepared HP-β-CD-encapsulated curcumin is equi-efficacious to nano-dispersed curcumin.

Polarization, excited states, trans-cis properties and anisotropy of thermal and electrical conductivity of the 4-(phenyldiazenyl)aniline in PVA matrix

In the present work, Polarization, Excited States, Trans–Cis (E → Z) Isomerization Properties and Anisotropy of Thermal and Electrical Conductivity of the 4-(phenyldiazenyl)aniline in the presence of polyvinyl alcohol (PVA) matrix were studied. DFT, UV/Vis, IR-Spectroscopies and Indicator Method were used for Determination of Thermal Conductivity of polymer films. The absorption spectra of the 4-(phenyldiazenyl)aniline in dimethylformamide (DMF) solvent and in aqueous medium were calculated. The nature of absorption peaks of the 4-(phenyldiazenyl)aniline in the UV/Vis spectral regions were interpreted. The solvent effect on the absorption spectrum of the 4-(phenyldiazenyl)aniline has established. The molecular HOMO-LUMO, excitation energies and oscillator strengths for E and Z isomers of the 4-(phenyldiazenyl)aniline have also been calculated and presented. Optical Properties of the PVA-films containing 4-(phenyldiazenyl)aniline have been also investigated. Polarizing Efficiency (PE) of obtained PVA-film is 98–99% at Stretching Degree (Rs) 3.5. Anisotropy of thermal and electrical conductivity of PVA-films containing E and Z isomers of the 4-(phenyldiazenyl)aniline was also measured and discussed.

Silver Nanoparticles Synthesized Using Mint Extract and their Application in Chitosan/Gelatin Composite Packaging Film

The present study reports synthesis of silver nanoparticles (AgNPs) using mint extract (ME) in the presence of polyvinyl alcohol (PVA) as capping material. PVA, ME and silver nitrate at concentration of 1%, 0.01% and 0.02%, respectively were found to be optimum for the synthesis of nanoparticles. The formation of AgNPs was confirmed by measuring surface plasmon resonance (SPR) peak. The intensity of SPR peak remained unaltered thus suggesting stability of colloid without aggregation during storage. The nanoparticles inhibited the growth of food borne bacteria namely Escherichia coli, Pseudomonas aeruginosa and Bacillus cereus. The incorporation of these nanoparticles in chitosan and gelatin blend resulted in homogenous films. Mechanical properties and water vapor transmission rate of chitosan-gelatin films improved due to addition of AgNPs, whereas optical (opacity and UV light transmittance) and oxygen permeability properties remained unchanged. These films had the ability to inhibit growth of 5 log CFU of the above test organisms. These findings suggest that the AgNPs obtained by reduction of silver by ME can be effectively utilized to prepare antibacterial eco-friendly food packaging material.

Bacterial cellulose-assisted de-lignified wheat straw-PVA based bio-composites with novel characteristics

In the present study, in-house extracted ligninolytic consortium was used as a green catalyst to modify the pristine wheat straw through de-lignification. The ligninolytic consortium showed an enhanced level of de-lignification with a maximal cellulose exposure from 24% to 76.54% cellulose. The de-lignified wheat straw was further strengthened using bacterial cellulose integration. Subsequently, a well-known compression molding technique was used to develop bio-composites from a de-lignified and bacterially modified wheat straw in the presence of polyvinyl alcohol (PVA) and glycerol as a plasticizer. The newly developed bio-composites were characterized using a variety of analytical and imaging techniques including Fourier Transform Infra-Red Spectroscopy (FT-IR) and Scanning Electron Microscopy (SEM). Evidently, the characterization profile revealed a considerable improvement in the morphology, mechanical and water uptake features of the newly developed bio-composites. In summary, the improved characteristics of bacterial cellulose-assisted de-lignified wheat straw-PVA based bio-composites suggest a high potential of enzymatic treatment for biotechnological exploitability.

Bioactive 3D-Shaped Wound Dressings Synthesized from Bacterial Cellulose: Effect on Cell Adhesion of Polyvinyl Alcohol Integrated In Situ

We investigated wound dressing composites comprising fibrils of bacterial cellulose (BC) grown by fermentation in the presence of polyvinyl alcohol (PVA) followed by physical crosslinking. The reference biointerface, neat BC, favoured adhesion of fibroblasts owing to size exclusion effects. Furthermore, it resisted migration across the biomaterial. Such effects were minimized in the case of PVA/BC membranes. Therefore, the latter are suggested in cases where cell adhesion is to be avoided, for instance, in the design of interactive wound dressings with facile exudate control. The bioactivity and other properties of the membranes were related to their morphology and structure and considered those of collagen fibres. Bioactive materials were produced by simple 3D templating of BC during growth and proposed for burn and skin ulcer treatment.

Improved electrochemical performance of Li1.2Ni0.2Mn0.6O2 cathode material for lithium ion batteries synthesized by the polyvinyl alcohol assisted sol-gel method

Li-rich Mn-based cathode materials (Li1.2Ni0.2Mn0.6O2) have been synthesized by a polyvinyl alcohol (PVA)-assisted sol-gel method. The influence of PVA content on the structure and electrochemical performance of Li1.2Ni0.2Mn0.6O2 has been investigated respectively. XRD results of the Li1.2Ni0.2Mn0.6O2 powders show that they exhibit similar XRD patterns as those of Li-rich Mn-based cathode materials, and the crystalline nature of the layered compound are improved by the presence of PVA. Physical characterizations indicate that the as-synthesized oxide is composed of uniform and separated particles compared to the larged aggregated ones of the product synthesized under the same condition but without PVA. As cathode for lithium ion battery, the material synthesized with 10% PVA exhibits not only a relatively high discharge capacity of 254.2mAhg−1, but also excellent rate performance and good cycling performance. EIS results show that the material synthesized with PVA decreases the charge-transfer resistance and enhances the reaction kinetics, which is considered to be the major factor for higher rate performance.

The influence of particle size and surface treatment of filler on the properties of oyster shell powder filled polypropylene composites

In this study, properties of oyster shell powder filled polypropylene (OSP/PP) composites were improved by enhancing particle distribution and filler‐matrix interfaces in the composites. The OSP enhances thermal stability and fire retardant properties of polymer composites but it decreases the mechanical strength due to poor interaction with the polymer matrix. OSP is an amorphous powder which agglomerates during distribution. Polyvinyl alcohol (PVA) was used to enhance the interfacial bonding between OSP and PP, while distribution of the OSP particles in composites was improved by varying the particle size of the filler. The effects of particle size and PVA treatment on mechanical properties of composites were studied through experimental tests and finite element analysis. Experimental results and finite element analysis agree to each other, it was observed that small size particles and PVA incorporation resulted in improving properties of OSP/PP composites. Mechanical properties were improved while thermal stability and fire retardancy were further enhanced. Fourier transform infrared spectroscopy revealed a physical interaction between the composite constituents in the presence of PVA. POLYM. COMPOS., 39:2420–2430, 2018. © 2016 Society of Plastics Engineers

Improved thermoelectric performance of BiCuSeO by Ag substitution at Cu site

BiCuSeO oxyselenide-based thermoelectric materials are attracting much attention due to their ultra-low intrinsic thermal conductivity (ĸ) and moderate Seebeck coefficient (S). However, the low conversion efficiency limits their application in energy conversion systems. This paper investigated the effect of monovalent Ag-doping in BiCuSeO at Cu site in the presence of polyvinyl alcohol (PVA). The results show that Ag is effectively doped at Cu site. The heavy atom substitution in BiCu1−xAgxSeO at Cu site can enhance S and reduce its total thermal conductivity (k) by phonon scattering. Further, the incorporation of heavy atom (Ag) with different ionic radii results in the improved ZT of 0.64 for BiCu1−xAgxSeO, which is 16% more than that for pure BiCuSeO (ZT = 0.55) at 923 K. It is believed that the Cu site should be an efficient dopant site to improve the efficiency of oxyselenide-based thermoelectric materials.

Decontamination of chemical warfare sulfur mustard agent simulant by ZnO nanoparticles

In this study, zinc oxide nanoparticles (ZnO NPs) have been surveyed to decontaminate the chloroethyl phenyl sulfide as a sulfur mustard agent simulant. Prior to the reaction, ZnO NPs were successfully prepared through sol–gel method in the absence and presence of polyvinyl alcohol (PVA). PVA was utilized as a capping agent to control the agglomeration of the nanoparticles. The formation, morphology, elemental component, and crystalline size of nanoscale ZnO were certified and characterized by SEM/EDX, XRD, and FT-IR techniques. The decontamination (adsorption and destruction) was tracked by the GC–FID analysis, in which the effects of polarity of the media, such as isopropanol, acetone and n-hexane, reaction time intervals from 1 up to 18 h, and different temperatures, including 25, 35, 45, and 55 °C, on the catalytic/decontaminative capability of the surface of ZnO NPs/PVA were investigated and discussed, respectively. Results demonstrated that maximum decontamination (100 %) occurred in n-hexane solvent at 55 °C after 1 h. On the other hand, the obtained results for the acetone and isopropanol solvents were lower than expected. GC–MS chromatograms confirmed the formation of hydroxyl ethyl phenyl sulfide and phenyl vinyl sulfide as the destruction reaction products. Furthermore, these chromatograms proved the role of hydrolysis and elimination mechanisms on the catalyst considering its surface Bronsted and Lewis acid sites. A non-polar solvent aids material transfer to the reactive surface acid sites without blocking these sites.