Polyvinyl Alcohol Thin Film Research Articles

Resistive Switching in Reduced Graphene Oxide Incorporated Polyvinyl Alcohol Films

Reduced graphene oxide (rGO) nanoparticle incorporated thin films of polyvinyl alcohol (PVA) were spin coated on ITO coated glass substrates. I-V characteristics revealed resistive switching in these films. The ON/OFF switching ratio values varied with voltage sweep cycles. The largest switching ratios obtained were 8 orders between the high resistance state (HRS) to low resistance state (LRS) and 7 orders for the LRS to HRS. In the LRS, the electrical conduction was initially space charge limited which turned to ohmic behavior that persisted till switching occurred to HRS. In the reverse voltage sweep, the conduction in HRS was initially ohmic, which then turned into a hopping type of conduction which persisted till switching occurred to the LRS. These conduction mechanisms in LRS and HRS are qualitatively different from that of pure rGO and other PVA composite films investigated earlier.

H‐BN huddled starch reinforced polyethylhexylacrylate\polyvinyl alcohol thin films for packaging applications

Herein, starch hybrid polyethylhexylacrylate\polyvinyl alcohol (PEHA/PVA‐s) thin films are synthesized by in situ polymerization of ethylhexylacrylate (EHA) with incorporation of hexagonal boron nitride (h‐BN). The occurrence of h‐BN nanoparticles in PEHA/PVA‐s thin films is characterized by Fourier transform infrared (FTIR) spectroscopy, X‐ray diffraction (XRD), and energy dispersive X‐ray (EDX) analysis. The field emission scanning electron microscopy (FESEM) images illustrates the embedment of h‐BN nanoparticles in the PEHA/PVA‐s films. It is found that, h‐BN nanoparticles have an average particle size of 100 nm observed with a lattice fringe of 0.35 nm are known from high resolution transmission electron microscopy (HRTEM) images. The surface and nano‐tribological features of thin films are studied by atomic force microscope (AFM). The thermal conductivity of films is enhanced with increase in h‐BN concentrations. From rheological study, it is observed that, the tan δ value varies from 0.3 to 0.5. The biodegradation, refractive index, and chemical resistance properties of the thin films are studied. The oxygen barrier properties of the thin films are substantially reduced by 18 folds due to incorporation of huddled h‐BN layers. The prepared PEHA/PVA‐s@h‐BN thin films with improved physicochemical behaviors and reduction in gas barrier properties can enable the material for packaging applications. POLYM. COMPOS., 40:1810–1818, 2019. © 2018 Society of Plastics Engineers

Polyvinyl alcohol thin film reinforced by green synthesized zirconia nanoparticles

The focus of this work is to prepare polyvinyl alcohol (PVA) thin film reinforced by green synthesized zirconia nanoparticles. In order to do so, firstly, zirconia nanoparticles were synthesized by the rosemary extract-assisted sol-gel process as both template and stabilizing agents. The results showed that the as-obtained sample with zirconium salt to rosemary extract ratio of 1:4 had a semi-spherical morphology with the mean particle size of 12–17 nm. This nanoparticle was added as reinforcement with different ratios to the polyvinyl alcohol matrix. The mechanical property of the as-prepared nanocomposites revealed that the elastic modulus of 1 wt% ZrO2-PVA sample was about 5.5 times higher than pure PVA thin film.

Ultrashort Pulse Soliton Fiber Laser Generation With Integration of Antimony Film Saturable Absorber

A soliton-locked Erbium-doped fiber laser is demonstrated for the first time using a pure Antimony (Sb) film as a saturable absorber (SA). The SA device is fabricated by depositing a 5 μm Sb layer onto a polyvinyl alcohol thin film via Physical vapor deposition process. Self-starting soliton mode-locked pulses train with a constant repetition rate of 0.99 MHz is obtained as the pump power increased from 101 mW to 142 mW. The laser operates at 1559 nm with a pulse width of 3.53 ps. At the pump power of 142 mW, the maximum peak power and pulse energy are calculated as 5.83 kW and 20.59 nJ, respectively. The obtainable pulse is very stable with a signal-to-noise ratio (SNR) of 70 dB. Our experimental results manifest that the pure Sb thin film-based SA is able to generate mode-locked pulsed laser at the 1.55-micron laser regime.

Q-switched and mode-locked thulium-doped fiber laser with pure Antimony film Saturable absorber

Stable and compact Q-switched and mode-locked thulium-doped fiber laser (TDFL) is demonstrated by employing Antimony (Sb) film Saturable absorber (SA) in the ring cavity. The Sb film SA is fabricated by sputtering a thin layer of Sb element onto polyvinyl alcohol (PVA) thin film. Self-pushed TDFL Q-switched with repetition rate and pulse width of 14.5 kHz to 23.5 kHz and 11.6 μs to 4.9 μs respectively are obtained, as the pump power raises from the threshold (271 mW) to its maximum (399 mW). The TDFL Q-switched spectrum is centered at 1947 nm wavelength. At the maximum pump power (399 mW), the maximum peak power and the maximum pulse energy are obtained at 24.4 mW and 120.12 nJ respectively. Meanwhile, self-starting mode-locked TDFL emerges as the pump power varies from 454 mW to 582 mW. The TDFL mode-locked output spectrum is centered at 1914 nm wavelength. A nearly constant repetition rate of 8.65 MHz and pulse width of 64 ps are observed, as the pump power lifted to the maximum (582 mW). The results verify that the pure Sb PVA film SA is viable to construct stable and reliable short pulse laser in the 2-micron regime.

Enhanced electro-conductivity and multi-shielding performance with copper, stainless steel and titanium coating onto PVA impregnated cotton fabric

Samples of the woven cotton fabric are first modified with a continuous polyvinyl alcohol (PVA) thin film by using the padding method and then coated with copper (Cu), titanium and stainless steel (SS) respectively, by using a magnetron sputtering system. The samples are then systematically characterized with energy dispersive X-ray spectroscope, X-ray diffractometer, and scanning electron microscope. The infrared (IR), ultraviolet and electromagnetic interference shielding properties of the samples are also well investigated, as well as the contact angle (CA), light transmittance and conductivity. The results show that pretreatment with PVA can enlarge the light transmittance of cotton fabric. The metal coated PVA/cotton samples show a better performance in electro-conductivity although there is a little bit decrease in other properties compared to the metal coated cotton fabric. The Cu coated PVA/cotton sample has a higher electromagnetic interference shielding effectiveness of − 30 dB, a lower electrical resistivity of 5.49 × 10−6 Ω m, while the Cu coated cotton sample presents a higher IR reflection rate about 25%, the SS coated cotton fabric show a higher CA of 128.2 °and UPF of 117.647. The excellent properties of the coated cotton fabric mean that it is a promising electro-conductive and multi-shielding textile for smart applications.

All-optical modulator based on MoS2-PVA thin film

The all-optical approach plays an important role in ultrafast all-optical signal processing, and the all-fiber scheme has a wide application in optical communications. In this letter, we investigate an all-optical modulator using few-layer molybdenum disulfide (MoS2)-polyvinyl alcohol (PVA) thin films based on the thermo-optic effect and obtain a long-time stable modulated output by applying polarization interference. By absorbing the injected 980 nm pump (control light), MoS2 generates heat, changes the refractive index of MoS2, and modulates the polarization of light. The obtained thermal all-optical modulator has a rise time of 526 μs.

Bioinspired Dip Catalysts for Suzuki–Miyaura Cross‐Coupling Reactions: Effect of Scaffold Architecture on the Performance of the Catalyst

AbstractDip catalysts suitable for catalyzing important chemical reactions are designed based on bioinspiration principles and are fabricated using a facile soft lithography technique. Specifically, in this work, leaves from two different plants, Gladiolus dalenii and Amaryllis belladonna are chosen, due to their contrasting surface topographical features. The surface microstructures of these two leaves are replicated on a polymer in order to prepare scaffolds for the fabrication of dip catalysts. The microstructures of these scaffolds are utilized to direct the self‐assembly of Pd nanoparticles according to the surface topographical features. A thin film of polyvinyl alcohol is used to lock the nanoparticles on the surface and prevent them from leaching. The fabricated bioinspired dip catalysts are thoroughly characterized and are demonstrated to be highly efficient for Suzuki–Miyaura cross‐coupling reactions, examined under different experimental conditions. These bioinspired dip catalysts' performance is evaluated based on the percentage yields of the reaction and is correlated with the corresponding surface topographical features to understand the effect of the scaffold architecture on the performance of the catalysts. The developed strategy can be easily adopted to fabricate many more dip catalysts, with intriguing surface features, suitable for catalyzing several other chemical reactions as well.

Synthesis and Characterization of PVA/TiO<sub>2</sub> Nanocomposite <sub> </sub>

A thin film of polyvinyl alcohol (PVA) and nanocomposite of PVA/TiO2 have been prepared by spin coating method at room temperature. The influence of titanium dioxide nanoparticles on the structure, optical, and functional group analysis of nanocomposite of polyvinyl alcohol/titanium dioxide was studied by using X-ray diffraction analysis, UV–vis spectroscopy and FTIR (Fourier Transform Infrared Spectroscopy). As some significant amount of titanium dioxide nanoparticles were added to the synthesis process of a thin film of PVA/TiO2 nanocomposite and it was found that electronic band gap of the polyvinyl alcohol decreases from 3.94 eV to 3.04 eV, and absorption wavelength shifted towards red. For titanium dioxide nanoparticles, the calculated value of band gap is 3.24 eV. The XRD peak of the PVA/TiO2 was obtained in between the peak of the titanium dioxide nanoparticles and polyvinyl alcohol. FTIR confirms the presence of bonds Ti-O, -OH , -CH2 , -CH3 and of a carbonyl group.

Structural properties and temperature dependence dielectric properties of PVA-Al $$_2\mathrm{O}_3$$ 2 O 3 composite thin films

Thin films of polyvinyl alcohol (PVA)–aluminium oxide(Al\(_2\mathrm{O}_3\)) composite have been made by solution casting method. XRD, FESEM and FTIR techniques were used to characterize the prepared composite films for structural analysis. The existence of M–O bond was identified by FTIR. XRD study reveals that PVA composite has polycrystalline in nature. The morphological study shows the dispersion of Al\(_2\mathrm{O}_3\) particles on the surface of thin films. The effect of temperature and frequency on dielectric properties of PVA–Al\(_2\mathrm{O}_3\) composite was investigated and improvement of dielectric properties with temperature observed. AC conductivity is increased with temperature and maximum conductivity of \(3.20 \times 10^{-5}\) S/cm for PVAl-10% at 353 K is observed. Activation energy is evaluated from Arrhenius plot and found to lie in between 0.05 and 0.16 eV. Frequency exponent factor ‘s’ for Pristine PVA and PVAl-10% was calculated and found to lie in between 0 and 1. Impedance plots depict the semicircle at higher frequencies and residual tail at the lower frequencies and value of Rb is found to decrease till PVAl-10% and increased for further concentration. The prepared PVA–Al\(_2\mathrm{O}_3\) composites could be used in optoelectronic devices and thin film transistors as high k layer due to their high dielectric constant with low dielectric loss.

Effect of aluminum nanoparticles on the linear and nonlinear optical properties of PVA

Linear and nonlinear optical properties of Polyvinyl Alcohol thin film doped with aluminum nanoparticles have been investigated experimentally. Aluminum nanoparticles were produced using pulsed laser ablation method. The fundamental wavelength of Nd-YAG laser at 7 ns pulse width was employed to produce aluminum nanoparticles in water at different sizes and concentrations. TEM images were used to study the nanoparticles after ablation. UV–Vis–NIR spectroscopy data were used to extract the real and imaginary parts of refractive index and dielectric functions of films and z-scan technique was used to measure the nonlinear refractive index and absorption coefficient of films. Results show that in comparison with particle size, the concentration of doped nanoparticles is more effective on the optical properties of polymers thin films. Band gap energy of polymer films was decreased with decreasing the size and increasing the concentration of nanoparticles while their refractive index was decreased.

Graphene-oxide films printed on rigid and flexible substrates for a wide spectrum of applications

Structures of films produced from a water-based graphene oxide ink by 2D printing on various substrates, including those of the flexible type, are compared. It was shown that the deposition of a thin polyvinyl alcohol film making substrates hydrophilic leads not only to more uniform application of the ink, but also to a denser film structure with a shallower surface profile. The processing of a graphene-oxide suspension in a blender additionally reduces the particle size of the suspension, which results in improvement of the structure and, on the whole, a shallower surface profile of the film. Comparison of the electrical properties of films on silicon with various coatings hydrophilizing the substrates demonstrated that the properties of the structures strongly depend on the type of coatings, which can change the conductivity type of the silicon substrate and lead to doping of the graphene-oxide film. At graphene-oxide film thicknesses not exceeding 25 nm, noticeable currents (>1 µA) appear in the films at voltages higher than 1–1.5V. The graphene-oxide layers are promising for the fabrication of protective and insulating coatings and sensors and, in the case of reduction, for the deposition of transparent electrodes.

Micropatterning of silver nanoclusters embedded in polyvinyl alcohol films.

Direct laser writing has been utilized to fabricate highly photostable fluorescent nanocluster microstructures in an organic polymer poly(methacrylic acid), where the carboxyl functional group is reported to play a vital role in nanocluster stabilization. In this Letter, we demonstrate that not only the polymer containing the carboxyl functional group, but also the polymer comprising the hydroxyl group, namely polyvinyl alcohol (PVA), can act as an appropriate stabilizer matrix for laser-induced synthesis and patterning of silver nanoclusters. The as-formed nanoclusters in the PVA film exhibit broadband emission and photostability comparable to the nanoclusters formed in the poly(methacrylic acid) polymer. As PVA is a widely used, nontoxic, biocompatible and biodegradable polymer, the technique of patterning fluorescent nanoclusters in PVA thin films is expected to find numerous applications in fields like fluorescence imaging, biolabeling, and sensing.

Bi2Se3as a saturable absorber for ultrafast photonic applications of Yb-doped fiber lasers

We experimentally demonstrated a Q-switched mode-locked (QML) and a continuous-wave mode-locked (CWML) ytterbium-doped fiber lasers with topological insulator: Bi2Se3 as saturable absorber (SA) in all normal dispersion regime. The Bi2Se3-SA is conventionally composited by embedding Bi2Se3 nanoplatelets into polyvinyl alcohol thin film, which provides a modulation depth of 7.6% and a saturation intensity of 38.9 MW/cm2. Based on this SA, with different cavity length, ytterbium-doped fiber laser can be operated at QML and CWML state, respectively. In the QML operation, a Q-switched envelope has the shortest pulse width of 1.12 μs and the tunable repetition rate from 96 to 175 kHz. The largest pulse envelope energy is 39.6 nJ, corresponding to average output power of 6.93 mW. In the CWML operation, an environmentally stable dissipative soliton laser pulse with pulse duration of ∼210 ps is obtained. The single pulse energy is 0.83 nJ with the repetition rate of 11.38 MHz at the wavelength of 1037 nm.

Excitation energy transfer in partly ordered polymer films differing in donor and acceptor transition moments orientation

Based on spectroscopic measurements selected properties of nonradiative Förster energy transport are studied in uniaxially stretched polyvinyl alcohol thin films for three systems differing in donor and acceptor transition moments orientation relative to the axis of stretching. In particular, donor – acceptor emission anisotropy spectra yield completely different regularities for these systems in uniaxially stretched films, whereas they are similar in unstretched films. In particular it is shown that acceptor fluorescence can be either strongly polarized after nonradiative energy transfer in stretched films or depolarized depending on the angular distribution of acceptor transition moments in the matrix. Donor and acceptor emission anisotropy decays exhibit similar regularities to those of steady-state measurements. The obtained results are analyzed with the help of Monte Carlo simulations.

Photochromic Effect of Copper Doped Nano Silver Chloride Impregnated Polyvinyl Alcohol thin Film

Photochromic Effect of Copper Doped Nano Silver Chloride Impregnated Polyvinyl Alcohol thin Film

Investigation of structural and electrical properties of novel CuO–PVA nanocomposite films

The objective of this study was to investigate the effects of CuO nanoparticles on the structural, thermal and electrical properties of polyvinyl alcohol (PVA) thin films. The thin films were prepared by a solution casting technique with different weight percentages viz., 0.5, 1.0, 1.5 and 2.0 wt% of CuO nanoparticles in PVA matrix. The fabricated nanocomposite thin films were structurally characterised by Fourier transform infrared spectroscopy and X-ray diffraction, while differential scanning calorimetry indicated the effect of CuO nanoparticles on thermal properties of PVA. The surface morphology of the films was determined by scanning electron microscopy technique. Dielectric properties were analysed using high frequency LCR metre and were found to be dependent on frequency and CuO concentration. Dielectric constant decreased with increase in both frequency and CuO concentration. Dielectric loss increased with frequency increase and decreased with increase in CuO concentration. AC conductivity increased with increase in frequency. PVA-2.0 wt% CuO nanocomposite was found to possess desirable properties such as low dielectric constant and low dielectric loss which makes it a desirable material for use in microelectronics industry.

Determination of optical constants and nonlinear optical coefficients of Violet 1-doped polyvinyl alcohol thin film

The optical properties of Violet 1-doped polyvinyl alcohol (PVA) have been investigated using Wemble and Didomenico (WD) method. The optical constants such as refractive index n, the dispersion energy Ed, the oscillation energy E0, the lattice dielectric constant \(\varepsilon _{\infty } \), light frequency dielectric constant e0 and the ratio of carrier concentration to the effective mass N/m* have been determined using reflection spectra in the wavelength range 300–900 nm. The single- beam Z-scan technique was used to determine the nonlinear optical properties of Violet 1:polyvinylalcohol (PVA) thin film. The experiments were performed using continuous wave (cw) laser with a wavelength of 635 nm. The calculated nonlinear refractive index of the film, n2 = −2.79×10−7 cm2/W and nonlinear absorption coefficient, β = 6.31×10−3 cm /W. Optical limiting characteristics of the dye-doped polymer film was studied. The result reveals that Violet 1 can be a promising material for optical limiting applications.

Photoluminescent, morphological and electrical properties of ZrO2 and ZrO2:polyvinyl alcohol composite thin films

The authors introduce the sol–gel technique to grow the ZrO2 and ZrO2:polyvinyl alcohol (PVA) composite thin films. For ZrO2 and ZrO2:PVA thin films, the photoluminescence and field emission scanning electron microscopy results are compared, indicating that the ZrO2 agglomeration process is effectively controlled by incorporating PVA, which results in the removal of crystallographic defects. In order to determine the correlation between morphology and performance, the Au/ZrO2/n-type Si (n-Si) and Au/ZrO2:PVA/n-Si devices are fabricated and their current–voltage characteristics are obtained. The electrical conduction investigations suggest that the substrate-injection leakage behavior is governed by the space-charge-limited current (thermionic emission–diffusion) for Au/ZrO2/n-Si (Au/ZrO2:PVA/n-Si) devices. The incorporation of PVA into ZrO2 is an important issue for modulating the leakage performance of Au/ZrO2/n-Si devices.

Optical Characteristics of Erbium-Doped SiO<sub>2</sub>/PVA Electrospun Nanofibers

This paper reports on the fabrication and optical characteristics of erbium-doped silica/PVA nanofibers via sol gel and electrospinning techniques. Silica glass, PVA (polyvinyl alcohol) and SiO2/PVA composites displayed 85% to 90% transparent across 300 2000 nm wavelength range. The transmission spectra were measured using Cary 5000 UV-Vis-NIR spectrophotometer. Silica was synthesized using TEOS (tetraethylorthosilicate) as the precursor, while PVA solution comprised of 7.0 wt% in H2O. The compositional ratios of SiO2:PVA were from 6:4 to 1:9 and were doped with 0.2% to 0.6% of erbium. Suitable viscosities of Er3+-doped SiO2:PVA solutions were electrospun into mesh of long strands nanofibers. Morphological and material compositions in the nanofibers were analysed using FESEM (field-emission scanning electron microscopy) and EDX (energy-dispersive X-ray spectroscopy). Er3+-doped SiO2:PVA thin films were coated on fused-silica glass substrates via spin coating and were characterized for their refractive indices, optical transmission, and fluorescence using M-line technique, UV-Vis-NIR spectrometer and photoluminescence spectrophotometer, respectively. Lower ratios of silica to PVA solutions results in higher viscosities and produced more uniform nanofiber structures of diameters around 100 nm with lesser beads. The refractive index of 1.61 for Er-doped SiO2:PVA (1:9) thin film was measured with TE polarized 632.8 nm wavelength laser and the index shows to be higher for more content of PVA in the glass/polymer composites. The 0.4% of Er3+ in SiO2:PVA composite produced the highest luminescence intensity at 605 nm when excited with 514 nm source. Higher doping content caused ion clustering effect and leads to concentration quenching, hence decreased in the emission intensity.