Folic Acid Sensing using CdTe doped Polyvinyl Alcohol Nanocomposite Hydrogels

This paper presents a novel class of multiwalled carbon nanotubes (MWCNTs) and zinc oxide (ZnO) doped polyvinyl alcohol (PVA) nanocomposites prepared using coagulation and solvent casting method. The dopant, ZnO nanoparticles, was prepared using precipitation method, and another dopant, MWCNTs, was treated with H2SO4and HNO3taken in 3:1volume ratio to create carboxylated MWCNTs. Furthermore, prepared ZnO and treated MWCNTs were doped into PVA matrix to prepare PVA nanocomposites by solvent casting technique. The Fourier transform infrared (FTIR) spectra detect the irregular shift in the bands of doped PVA nanocomposites indicating the presence of intra/intermolecular hydrogen bonding creating the interaction between the nanoparticles and neighboring OH group of PVA. Crystallinity of the prepared nanocomposites films was investigated using XRD technique, which explores the average particle size of the embedded nanoparticles and explains the complex formation and variation in crystallinity of the nanocomposites due to interaction of dopants. The decrease in optical energy band gap of nanocomposite films and the information of Urbach energy (Eu) were assessed by UV/vis spectroscopy. By using a universal testing machine, the mechanical properties of doped polymer films found escalation for doping percentage concentrationx=7.5 wt%. The phase homogeneity, film morphology, and chemical configuration of the nanocomposites were inspected using atomic force microscope, scanning electron microscopy and energy-dispersive X-ray spectroscopy, respectively.

Layered aligned dispersion of graphene in graphene/polyvinyl alcohol (PVA) nanocomposites is prepared in the form of films through simple solution processing route. The results indicate that there exist an interfacial interaction between PVA and graphene because of hydrogen bonding. This is responsible for the change in structure of PVA (such as decrease in the level of crystallization) and exhibiting ductile PVA nanocomposite film with improved tensile modulus, tensile strength, and thermal stability. Moreover, to improve the mechanical properties of PVA nanocomposites, graphene is successfully modified using a non-covalent modifier, sodium alginate (SA) and there exist an ‘anion-π’ type of interaction in between SA and graphene. The modification results in finer dispersion of the graphene in PVA/SA-m-graphene nanocomposites. In addition, there exist a hydrogen bonding in between PVA and SA. This has resulted in the remarkable improvement in mechanical properties of PVA/SA-m-graphene nanocomposites as compared to pure PVA and PVA/graphene nanocomposites. The increase in mechanical properties of PVA/SA-m-graphene nanocomposites is achieved through better load transfer from graphene to polymer matrix, despite decrease in crystallinity of PVA. Improvement in tensile modulus and tensile strength is highest at 0.5 wt.% of SA-modified graphene in PVA/SA-m-graphene nanocomposites because of finer dispersion of graphene and is 62 and 40% higher than that of pure PVA. Addition of SA-modified graphene also improves the thermal stability of PVA/SA-m-graphene nanocomposites remarkably as compared to unmodified graphene PVA nanocomposites.

Graphene nanoribbon (GNR) is quasi‐one dimensional carbon based nanomaterial, distinct from graphene and less explored nanofiller in optical and optoelectronic applications. Herein flexible poly vinyl alcohol (PVA) nanocomposites of 0, 0.25, 0.5 and 0.75 wt % compositions of GNR were prepared by using solution intercalation technique and characterized by spectroscopic methods to assess their structural and optical characteristics. The characterization of PVA@GNR nanocomposites revealed Vander Waals binding of GNR to PVA chains and also considerable crystallographic changes in PVA matrix upon the incorporation of GNR. The optical investigations showed UV‐visible absorption in the wavelength range of 200–280 and 350–520 nm which enhanced on increase in GNR dopant concentration. The decrease in the optical band gap and Urbach energy was also observed for the nanocomposites with increase in dopant concentrations thereby suggesting the formation of localized states in the forbidden band region. The refractive index, absorption coefficient, extinction coefficient and optical conductivity of PVA nanocomposites showed excellent agreement with the band gap revelations and indicated UVC light blocking properties in the wavelength of 200–280 nm. Further, the GNR incorporated PVA nanocomposites exhibited improved thermal stability, wettability transitions (hydrophilic to near hydrophilic) and excellent luminescent down‐conversion properties with a high Stokes's shift (100 nm) compared to pristine PVA nanocomposites. The study concludes that the proposed PVA@GNR nanocomposites can ideally fit optical and photovoltaic device applications owing to their transparency coupled with UV blocking and luminescence down‐shifting attributes.

A novel physicochemical crosslinked nanocomposite hydrogel based on polyvinyl alcohol (PVA) and natural Na‐montmorillonite (Na+‐MMT) was synthesized by chemical crosslinking of nanocomposite hydrogel followed by a freezing‐thawing process. The effects of physical crosslinking, as well as physicochemical crosslinking, on the structure, morphology, and properties (thermal, mechanical, swelling, and deswelling) of nanocomposite hydrogels were investigated and compared with each other. The structure and morphology of nanocomposites were studied by Fourier transform infrared, X‐ray diffraction, field emission scanning electron microscopy, and transmission electron microscopy techniques. The thermal and mechanical properties of nanocomposites that were affected by physical and physicochemical crosslinking were evaluated by thermogravimetric analysis, differential scanning calorimeter, dynamic mechanical analysis, hardness test, and Water vapor transmission rate (WVTR) experiments. The results showed that the physicochemical crosslinking of a PVA nanocomposite leads to a reduction in crystallinity and melting temperature, as well as an increase in the Hardness and WVTR compared to a physically crosslinked PVA nanocomposite hydrogel. The swelling and deswelling experiments were performed using a gravimetric method, and it was shown that controlled crosslinking of PVA nanocomposite hydrogel with glutaraldehyde causes the swelling ratio to increase and the cumulative amount of water loss to decrease. The swelling (sorption) and deswelling (desorption) kinetics data for physically and physicochemical crosslinking of nanocomposite hydrogels were fitted with a fickian model. It is concluded that through control crosslinking of PVA nanocomposite can lead to a hydrogel with higher swelling capacity than that is in conventional PVA nanocomposite hydrogel. POLYM. COMPOS., 37:897–906, 2016. © 2014 Society of Plastics Engineers

Double network polyvinyl alcohol (PVA) hydrogel nanocomposites were prepared through interpenetrating of an amide‐sulfonic acid functionalized hydrogel into the PVA matrix, which was reinforced by carboxylated β‐cyclodextrin (CCD) modified ZnO@Mg–Al LDH (CZnL). CZnL was prepared by the reconstructing calcined LDH, supported by ZnO nanoparticles in the presence of CCD. XRD, FE‐SEM, and TEM results indicated the successful self‐assembled and intercalated LDH in the presence of surface‐coated ZnO nanoparticles. The water content measurements indicated the significant impact of the double network hydrogel on the absorption of water molecules. The TGA result of the PVA sample loaded with 2 wt% of hydrogel exhibited highest thermal stability, suggesting a greater impact of the hydrogel compared to the nanohybrid filler. The MCC and LOI results indicated a desirable synergistic effect of CZnL and hydrogel in enhancing the flame retardancy of the PVA films. The PVA sample loaded with 2.5 wt% of CZnL and 2.5 wt% hydrogel exhibited 171 W·g−1 and 176 kJ·g−1 reductions in pHRR and HRC values, respectively, compared to neat PVA. The elongation at break and tensile strength of the mentioned sample increased from 17.68% to 21.25% and 88.30 to 96.86 MPa, respectively, compared to neat PVA.Highlights Preparation a nanohybrid including nanosized ZnO installed on the calcined LDH. Synthesis of carboxylated β‐cyclodextrin for modification of ZnO@LDH. Preparation of double network PVA/CD modified ZnO@LDH hydrogel nanocomposites. The effect investigation of hydrogel and modified nanohybrid on the PVA properties. Improved properties were observed in the PVA nanocomposites.

Effects of cellulose nanofibrils/graphene oxide hybrid nanofiller in PVA nanocomposites

Polyaniline (PANI) - Polyvinyl alcohol (PVA) nanocomposite were prepared using laser irradiation method. X-ray diffraction results showed that, (PANI/PVA) nanocomposite exhibited amorphous nature of polymer. The electronic transition will be studied using Ultraviolet-Visible spectrometer (UV-Vis). The real part of dielectric constant (έ) and imaginary part (ε") were studied. Also, the relaxation time was calculated.

The effects of UV irradiation on chemical, thermal, mechanical, and morphological properties of polyvinyl alcohol (PVOH)/2 wt.% of nanoclay(NC) filler were investigated. PVOH composite films were prepared from PVOH blend with fixed content (2%) of NC via the solution casting method. Pure PVOH and PVOH composites were exposed to 340 nm fluorescent UV lamps and assessed for 50 h, 100 h, and 200 h UV exposue. The experimental results such as Fourier transform infrared (FTIR) confirmed that 2% wt. NC filler is efficient and can resist chemical degradation that is caused by ultraviolet irradiation (UV). The carbonyl and hydroxyl indices were increased with increasing the UV exposure irradiation times of both PVOH and PVOH composite. However, the PVOH nanocomposites exhibited more resistant to increasing the indices after exposure to UV irradiation with a longer exposure time. The thermal results (TGA) indicated that PVOH nanocomposite is exhibited more resistance to thermal degradation after UV irradiation exposure compared to that of pure PVOH sample. From DMA results, the storage of modulus was reduced after exposure to UV irradiation of PVOH and PVOH nanocomposites. The results of Tg of PVOH nanocomposites increased after the incorporation of 2% wt. NC into PVOH after exposure to UV irradiation. PVOH nanocomposite exhibited more resistance to reduce the tensile strength after exposure to 200 h UV irradiation. XRD tests showed that PVOH/2 wt.% NC nanocomposites have more resistant to increase intensity after exposure to 200 h UV irradiation compared to that of PVOH sample. The morphology micrographs showed that no obvious cracks on the PVOH nanocomposite after UV irradiation exposure by comparing to that of pure PVOH.

This article presents a review of studies on materials, preparation, properties, and characterization of polyvinyl alcohol (PVA) nanocomposite hydrogels. The structure and properties of Montmorillonite, the nanoclay used in the manufacture of PVA nanocomposites and techniques for making PVA nanocomposite hydrogels have been reviewed. The characterization techniques such as Fourier transform infrared spectroscopy (FT‐IR), Differential scanning calorimetry (DSC), Dynamic mechanical analysis (DMA), Scanning electron microscopy, Transmission electron microscopy (TEM), X‐ray diffraction (XRD) are also studied. The XRD patterns and TEM images have proven the intercalated and exfoliated structures of PVA nanocomposite hydrogels that is due to the presence of nanoclay layers. Investigation of FT‐IR spectra shows the bonding formation between OH and silanol groups of PVA and Montmorillonite. Also, the results of DSC and DMA indicated a decrease in crystallinity and the glass transition temperature of PVA by the incorporation of nanoclay, while the loss modulus is increased compared to that of pure PVA. POLYM. COMPOS., 38:1086–1102, 2017. © 2015 Society of Plastics Engineers

High density energy storage is one of the current demands for sustaining renewable energy systems. This requires high charging and discharging rate, large power density and stability for prolong time of service. Several materials have been explored however none of them satisfy most or all of these requirements. Graphene oxide and Poly Vinyl Alcohol based nanocomposites have recently gained attention due to high mechanical stability. We have explored the use of Graphene Oxide – Poly Vinyl Alcohol nanocomposite as electrode material for supercapacitor applications. The oxygen containing groups in Graphene oxide enables the composite to store pseudo charge making it attractive for supercapacitor applications. Nanocomposite were synthesized by mixing poly vinyl alcohol and graphene oxide in solution phase. Electrochemical characterization shows that the Graphene Oxide – Poly Vinyl Alcohol has high specific capacitance and long life cycle, further they are ecofriendly, economical and hence potential candidates to be used as electrodes in supercapacitors.

Design and development of novel magnetic Lentinan/PVA nanocomposite for removal of diazinon, malathion, and diclofenac contaminants

Specimens of acidic multi‐walled carbon nanotubes (AMWNTs) reinforced polyvinyl alcohol (PVA) nanocomposites (AMWNTs‐PVA) were prepared using different amounts of AMWNTs by the traditional solution casting, involving ultrasonic wave agitation. The microstructures and tensile properties of AMWNTs‐PVA were investigated by scanning electron microscopy, dynamic mechanical analysis, and quasi‐static tensile testing. AMWNTs had good compatibility with PVA and dispersed evenly in the PVA matrix. The incorporation of AMWNTs improved the tensile modulus and strength of the PVA. The shape recovery testing revealed the shape recovery capacity of AMWNTs‐PVA. It was observed that the recovery ratio increased, and the shape recovery rate slightly decrease with the increase of AMWNTs content. The results showed that the AMWNTs had strong interaction with the segments of the PVA and hence affected the shape recovery behavior of PVA. © 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013

Natural halloysite nano clay with tubular structure was used for the preparation of polyvinyl alcohol (PVA) nanocomposites. A systematic and detailed study was conducted on the effect of nanotubes on the properties such as flame retardancy, water absorption capacity, and thermal stability of poly (vinyl alcohol) matrix. Morphological and structural characterizations of nanocomposites were performed by scanning electron microscopy (SEM), X-ray diffraction (XRD) and fourier transform infra red (FTIR) spectroscopy. XRD results showed peak broadening and disappearance in nanocomposites when compared to the peaks for nanotubes, indicating the better dispersion of nanotubes in the matrix. Owing to the hydrophilicity of nanotubes the nanocomposites exhibited enhanced water sorption properties. At higher temperature nano filler reinforced PVA showed better thermal stability and flammability due to barrier effect.

This paper is about tailoring high permittivity of multi-walled carbon nanotubes/silver nanoparticles (MWNT-AgNP) filled polyvinyl alcohol (PVA) nanocomposites at low frequency. PVA/MWNT-AgNP nanocomposites were synthesized via solution-casting technique at low MWNT content with different loading of AgNP. The nanocomposites showed a significant increment in ac conductivity, σac, and dielectric permittivity, ε′ by two orders of magnitude as compared to pure PVA. The maximum ε′ value was achieved about 600 at 1.0 wt% of AgNP due to the increased charge carriers density and high interfacial polarization within the nanocomposites. The relaxation frequency was shifted towards a higher value with the increased of AgNP content while the relaxation time was decreased by 40%. Field emission scanning electron microscopy (FESEM) images showed the enhanced distribution of MWNT in the presence of AgNP to provide conductive pathways in the matrix. This was confirmed by energy-dispersive x-ray (EDX) analysis and ultraviolet-visible (UV–vis) spectroscopy. As a result, PVA/MWNT-AgNP nanocomposites have great potential for electrical applications such as cable accessories, high charge-storage capacitor and electromagnetic interference shielding materials.

Objective: To determine the thermal stability of polyvinyl alcohol films under different concentrations of CeO2 nanoceria. Method: Cerium Oxide doped polyvinyl alcohol (PVA) nano-composites were synthesized by the traditional solution casting method for various concentrations of nano CeO2 by solution combustion method. The thermal properties of prepared PVA-2.5 wt% CeO2, PVA-7.5 wt% CeO2 , PVA-12.5 wt% CeO2, and PVA-25 wt% CeO2 composite films were elucidated by using techniques such as Differential Scanning Calorimetry, Thermogravimetry analysis and Differential Thermal analysis. Findings: The glass transition temperature of the pure PVA is found to be 114°C, whereas it varies between 110°C-120°C for composite films. The melting temperature of the composite films is the same as that of pure PVA except in the case of 7.5wt% CeO2 and 25wt% CeO2 composites. The reduced melting point of these composites elicits a decrease in crystallinity. A 12.5 wt % and 25 wt% CeO2-PVA nano-composite films exhibit an increase in the final degradation temperature, a high specific heat capacity, low mass loss, and a larger residual weight, indicating their potential applicability in thermal coating and thermal sensing applications. Polyvinyl alcohol (PVA) films are being used routinely as a dielectric layer for electrical applications due to the good physiochemical and dialectic properties of the material. An incorporation of CeO2 nanoceria improves not only the thermal but also the mechanical properties of PVA and extends its application for electrical and optical operation. Here in the present study, different concentrations of CeO2 were incorporated with the PVA and analysed for the thermal properties. The study showed that 12.5 wt % and 25 wt% CeO2-PVA nano-composite enhanced PVA film thermal stability. Keywords: PVA-CeO2 Nanocomposites; Differential Scanning Calorimetry; Thermogravimetry Analysis and Differential Thermal Analysis; Physical properties and thermal properties