Effect of ZnSe and CdS Shells on the Structural and Photophysical Behavior of CdSe Nanocrystals in a PVA Matrix

In this work, metal/semiconductor nanocomposites/metal devices with aluminium (Al) as top electrode (TE) and bottom electrode (BE) were fabricated and investigated using ZnO nanoparticles (ZNPs) embedded in an insulating polyvinyl alcohol (PVA) matrix for non-volatile memory applications. The I-V measurements of Al/ZnO-PVA/Al device exhibited a non-volatile bistable resistive switching behaviour. The switching mechanism of the device was suggested by the models of trap controlled space-charge limited conduction (SCLC) and the charges trapping-detrapping process at the centers of ZNPs in the PVA matrix. The state of the device was maintained even after removal of the applied bias, indicating the non-volatile bistable memory. There was no remarkable degradation of the device in both the LRS and the HRS after 30 minutes continuous operation which demonstrated excellent stability of the device. The current ratio of high resistance state (HRS) to low resistance state (LRS) is about of the order of 102 at room temperature. This demonstration provides a class of memory devices for non-volatile bistable memory device applications.In this work, metal/semiconductor nanocomposites/metal devices with aluminium (Al) as top electrode (TE) and bottom electrode (BE) were fabricated and investigated using ZnO nanoparticles (ZNPs) embedded in an insulating polyvinyl alcohol (PVA) matrix for non-volatile memory applications. The I-V measurements of Al/ZnO-PVA/Al device exhibited a non-volatile bistable resistive switching behaviour. The switching mechanism of the device was suggested by the models of trap controlled space-charge limited conduction (SCLC) and the charges trapping-detrapping process at the centers of ZNPs in the PVA matrix. The state of the device was maintained even after removal of the applied bias, indicating the non-volatile bistable memory. There was no remarkable degradation of the device in both the LRS and the HRS after 30 minutes continuous operation which demonstrated excellent stability of the device. The current ratio of high resistance state (HRS) to low resistance state (LRS) is about of the order of 102 at room ...

With an intention to replace the synthetic non-biodegradable films in packaging applications, the polyvinyl alcohol (PVA) blended with green banana peel filler (GBPF), the biodegradable films were prepared by solution casting method with varying the concentrations of GBPF (5–25 wt%) in PVA matrix. The bio films were characterized by Fourier-transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), thermo gravimetric analysis, transmissibility, FESEM, tensile test, film solubility and water absorption, water vapour transmission (WVT), soil burial test. Based on results obtained, the changes evidenced in the FTIR spectrum of this PVA/GBPF biofilms suggest that strong hydrogen bonding is taking place due to interfacial exchanges of GBPF in PVA matrix. The XRD results showed that crystallinity of bio films are greater than PVA. Thermo gravimetric analyses predicted that PVA/GBPF bio films are thermally stable up to 300 °C. The light is 45% for transmittance in the visible light region for the PVA/GBPF (25 wt%) bio film. The FESEM micrographs of biofilms palpable that formation of good physical interaction and compatibility between polymer matrix and GBPF up to 20 wt% of GBPF in PVA Matrix. FESEM results also confirmed that higher loading of GBPF (25 wt%) in PVA matrix, observed voids and agglomerations in film surface. The PVA/GBPF bio films with 20% of GBPF gave the highest tensile strength and young’s modulus 44.5 MPa and 66.7 GPA respectively compared to other samples. The elongation at break decreases with increases the GBPF in PVA Matrix up to 20 wt%.The slight decrease in mechanical properties perceived due to higher loading of GBPF (25 wt%) with PVA matrix. The solubility, water absorption and WVT of the PVA/GBPF bio films increased upon increasing the GBPF content. The biodegradation test results discovered that he highest weight loss at 42.3% (25 wt% of GBPF) probably due to the hydrophilic nature of GBPF in PVA matrix. On the whole, the present investigation confirmed that the PVA/GBPF bio films potential for possible utilization in active packaging applications attributable to its better mechanical, thermal, optical, water absorption and biodegradation properties.

Growth of MgO on multi-layered graphene and Mg in PVA matrix

Background: Polymer-clay nanocomposite (PCN) materials have become a focus of research due to their unique characteristics and potential commercial applications. Clay addition in polymers improves their properties and may result in better features. PCN materials are reported to have enhanced thermal, mechanical, flame retardation, corrosion protection characteristics. Objectives: This study investigates the effect of different loading concentrations of Na-rich montmorillonite (MMT) clay when they are effectively dispersed in a organic polyvinyl alcohol (PVA) matrix. Methods: PCN materials were prepared using the solution method. The structure morphology of the PCN was studied using x-ray diffraction (XRD) and NSEM. FTIR was applied to study the molecular structure of the PCN. The mechanical properties of the pure PVA and PCN were studied. The thermal stability of the PCN was studied using TGA and differential scanning calorimetry (DSC). Results: The morphological images and crystalline morphology indicated that PVA and MMT clay has intercalated by the uniform and homogenous dispersion and confinement of the PVA polymer chains within silicate layers of the clay. PCN XRD pattern has a high d-spacing compared to the pure MMT clay XRD pattern, which has a low d-spacing (Fig. 1). FTIR showed that as the loading of MMT clay increases, the intensities of the MMT clay bands become stronger in the FTIR spectra of PCN (Fig. 2). NSEM results showed that intercalation that took place between the PVA and MMT. It was found that the small amount of MMT clay made the tensile modulus and elongation percentage the PCN significantly higher than the pure PVA, due to polymer-clay intercalation. Thermal stability results showed that the PCN is more thermally stable than pure PVA. Conclusions: The excellent MMT nanoclay dispersion in PVA matrix leads to significantly enhanced mechanical properties, notably an increase in tensile moduli with significant increase in tensile strength, maximum load and percentage elongation of the PVA due to adding the small amount of MMT clay. The uniform and homogenous dispersion of MMT in PVA matrix results in an increase in thermal decomposition temperature and glass transition temperature of the promoted PVA polymer based on TGA (Fig. 3) and DSC (Fig. 4) results.

Photoluminescence study of PVP capped CdS nanoparticles embedded in PVA matrix

Visible-light-excited long-lived organic room-temperature phosphorescence of phenanthroline derivatives in PVA matrix by H-bonding interaction for security applications

A composite compound (CC) has been developed by the physical mixing of two coordination compounds(1,10-Phenanthroline)tris[4,4,4-trifluoro-1-(2-thienyl)-1,3butanedionato]europium (III) [abbreviated as Eu(TTA)3Phen or ETP] and (1,10-Phenanthroline)tris[2-acetoxybenzoate]terbium(III) [abbreviated Tb(ASA)3Phen or TAP]. Strong photo-physical properties of CC have been used for its study in different liquid medium and in PVA polymer matrix also. The studies of optical as well as structural properties of composite material have been carried out to observe the nature of interaction, energy transfer and migration of energies. The Fourier Transform Infrared (FTIR) spectra of CC show no new bond formation at atomic level and hence both ETP and TAP are entangled to each other by weak interacting forces. The photoluminescence (PL) emission of the Eu3+ ions enhance while of the Tb3+ ions decreases in the CC, indicating migration of energy from Tb3+ to Eu3+ ion. The effect of medium on the optical properties of this composite material has been investigated in detail. The excitation, emission as well as decay profiles of the composite material has been carried out in polar (ethanol), non-polar (Chloroform) as well as in polymer matrix {Poly-vinyl alcohol (PVA) matrix}. The reason behind the different shape and intensity in excitation and emission spectra of the composite material in different medium has been discussed. That concludes maximum fluorescence intensity in PVA matrix and least in polar solvents. In last stage, the plasmonic silver nanoparticles (AgNPs) have been introduced to further enhance the emission intensity in PVA matrix.

Effect of 8 MeV electron irradiation on the optical properties of PVP capped CdS nanoparticles in PVA matrix

This work was conducted to investigate the interactive effect of carbon nanotubes (CNTs) and montmorillonite (MMT) on the mechanical–physical properties of the polyvinyl alcohol (PVOH) nanocomposites. The increasing of CNTs amounts from 0.5 phr to 1 phr has gradually increased tensile strength and Young's modulus of all PVOH/MMT blends due to good interaction effect between MMT and CNTs with PVOH matrix especially for 2 phr MMT added PVOH blends. Besides, the addition of low CNTs amounts (≤1 phr) in PVOH matrix has significantly weakened the hydrogen bonding polymer matrix of all PVOH/MMT blends as evaluated in FTIR analysis. This is attributed to the good of dispersion of low amounts of CNTs could disturb the hydrogen bonding between PVOH molecules and thus induced the strength of OH stretching in PVOH matrix. However, higher amounts of CNTs (≥1.5 phr) have significantly increased hydrogen bonding in PVOH matrix due to the agglomeration of higher amounts of CNTs particles in PVOH matrix as observed in Fourier transform infrared spectroscopy and scanning electron microscopy analysis. From X‐ray diffraction and transmission electron microscopy observation, the MMT particles were found to effectively exfoliate in PVOH matrix of 2 phr MMT (low amounts) added PVOH/MMT/MCNTs composites, indicates that low MMT amounts could improve the interaction effect between PVOH matrix and CNTs particles. In conclusion, the incorporation of lower amounts of CNTs has effectively improved on the mechanical and physical properties of all PVOH and PVOH/MMT blends. J. VINYL ADDIT. TECHNOL., 26:77–89, 2020. © 2019 Society of Plastics Engineers

In this study, a type of alkaline solid polyelectrolyte (ASPE) membrane was developed via the introduction of microcrystalline cellulose (MCC) and its modified product (QMCC) into the polyvinyl alcohol (PVA) matrix. In this process, green NaOH/urea-based solvent was used to achieve a good dispersion of MCC in the PVA matrix; meanwhile, the OH− groups in the NaOH/urea-based solvent provided an alkaline environment for good ion conductivity. Compared to the MCC-incorporated ASPE, further improved conductivity was achieved when the MCC was modified with quantitative quaternary ammonium salt. TGA showed that the addition of QMCC improved the water retention of the matrix, which was beneficial to the OH− conduction in the system. Compared to the control (50 mS cm−1), a maximum conductivity of 238 mS cm−1 was obtained after the incorporation of QMCC in the PVA matrix. Moreover, the tensile strength of the polymer electrolyte were also significantly increased with the addition of QMCC. Finally, this developed ASPE membrane was used in assembling a flexible Zn–air battery and showed a promising potential in the development of flexible electronic devices.

Effects of hydrolysis degree on the formation of ferroelectric-core fillers and the electric performance of polyvinyl alcohol composites

In this research, titanium dioxide (TiO2) nanoparticles were immobilized into polyvinyl alcohol (PVA) matrix without and with surfactants via solution casting film combined with thermal treatment method. The dispersion and distribution of TiO2 nanoparticles presented by scanning electron microscopy (SEM) showed the uniform distribution of TiO2 nanoparticles in PVA matrix with surfactant. Fourier-transform infrared spectroscopy (FTIR) showed increasing intensity peak at 560-800 cm-1 corresponding to Ti-O stretching vibration indicating interaction between PVA and TiO2 after thermal treatment. X-ray diffraction (XRD) result showed peak of PVA crystal structure due to the thermal treatment, and the addition of surfactant could decrease the average crystallite size of TiO2 in PVA/TiO2 nanocomposite films. Photocatalytic activity was determined from the film efficiency on removal of methylene blue (MB) under ultraviolet (UV). The results showed the greater MB removal efficiency of the PVA/TiO2 nanocomposite films with surfactant and thermal treatment than those without surfactant and thermal treatment.

Polymer inorganic nanocomposites are attracting a considerable amount of interest due to their enhanced electrical and optical properties. The inclusion of inorganic nanoparticles into the polymer matrix results in a significant change in the nanocomposite’s properties. With this in mind, we have developed a nanocomposite film based on zinc oxide (ZnO) and polyvinyl alcohol (PVA) using a solution casting method with varying concentrations of ZnO nano powder in the PVA matrix. The ZnO / PVA film surface morphology was observed by the scanning electron microscope (SEM). The micrographs indicate that ZnO nanoparticles in the PVA matrix are homogeneously distributed. XRD results indicated that the crystallinity of the film was influenced by the interaction of ZnO nanoparticles and the PVA main chain. Crystallinity is also affected by the doping of ZnO nanoparticles in the PVA matrix and it increases when the concentration of ZnO is low and then decreases when the excess concentration of ZnO is present in the PVA matrix. The FTIR transmission spectra confirmed that significant interaction took place between the ZnO nanoparticles and the PVA main chain over the wave number range of 400–4000 cm−1. The UV–vis spectra reveal that the increase in concentration of ZnO nanoparticles in the polymer matrix results in the movement of the absorption edge in the direction of higher wavelength or lower energy associated with the blue/green portion of the visible spectrum. A decrease in the optical energy bandgap is observed with the increase in nano ZnO concentration in the matrix. Thickness has a signifcant affect on the properties of the ZnO/PVA nanocomposite and the morphology, particle size, degree of crystallinity and bandgap of the ZnO/PVA nanocomposite samples were influenced by the thickness of the sample. The optimal thickess of 0.03 mm with a weight percentage of 16.6% (ZnO) and 83.3% (PVA matrix) was selected due to its higher bandgap of 4.22 eV, reduced agglomeration/aggregation and smaller ZnO particle size of 14.23 nm in the matrix. The optimal film can be used in photovoltaic research.

Surfactants used to exfoliate and disperse nanoparticles are expected to have an impact on polymer nanocomposite properties. In this work, both ionic tetrabutylammonium hydroxide (TBA) and amphiphilic polyoxyalkyleneamine (M1000) surfactants were used to exfoliate α‐zirconium phosphate (ZrP) in polyvinyl alcohol (PVA) matrix through simple solution blending. The oxygen barrier properties of the nanocomposites were investigated as a function of ZrP content based on the above two surfactant types. At a low ZrP loading level (≤2.4 vol%), regardless of the surfactant type, the ZrP nanoplatelets in PVA matrix do indeed create a “torturous pathway” to improve barrier properties even though the crystallinity in PVA/ZrP‐M1000 system is decreased. In addition, the PVA/ZrP‐TBA films exhibit excellent transparency as good as the neat PVA films. Furthermore, it is found that the high molecular weight amphiphilic M1000 surfactant is less effective than the low molecular weight ionic TBA surfactant in dispersion and exfoliation of ZrP in PVA. This relative incompatibility of ZrP‐M1000 compared to ZrP‐TBA in PVA leads to its dramatic drop in oxygen barrier properties. This facile aqueous solution blending technique is eco‐sustainable and expected to facilitate the preparation of effective polymer nanocomposites for barrier properties applications.

Cellulose nanofibers (CNFs) were modified with 2 bilayers coating composed of polyethlenimine (PEI), melamine and phytic acid using a layer-by-layer self-assembly technique. The (PEI + melamine/phytic acid)2 based coating was successfully deposited on the surface of modified cellulose nanofibers (MCNFs). Herein, the CNF referred to the carbon source and the phytic acid was chosen as the acid source. Polyethylenimine and melamine served as the blowing agents. Then the CNF and MCNF were introduced to the polyvinyl alcohol (PVA) matrix to investigate the thermal decomposition, flammability, light transmittance and mechanical properties of the PVA/CNF and PVA/MCNF composites. The thermal decomposition of PVA-MCNF-6 (with 6 wt% MCNF) was retarded compared with that of pure PVA. Meanwhile, the addition of 6 wt% MCNF obviously reduced the peak heat release rate of PVA, as evidenced by the 37% reduction. The PVA/CNF and PVA/MCNF composites exhibited similar light transmittance compared with the pure PVA film. Moreover, the addition of CNFs in the PVA matrix resulted in higher tensile strength and elongation at break than those of the PVA matrix.