Polyvinyl Alcohol Graphene Oxide Research Articles

Tribological properties of aluminum alloy coated with graphene oxide/polyvinyl alcohol composites after micro-arc oxidation

PurposeAluminum alloy is considered an ideal material in aerospace, automobile and other fields because of its lightweight, high specific strength and easy processing. However, low hardness and strength of the surface of aluminum alloys are the main factors that limit their applications. The purpose of this study is to obtain a composite coating with high hardness and lubricating properties by applying GO–PVA over MAO coating.Design/methodology/approachA pulsed bipolar power supply was used as power supply to prepare the micro-arc oxidation (MAO) coating on 6061 aluminum sample. Then a graphene oxide-polyvinyl alcohol (GO–PVA) composite coating was prepared on MAO coating for subsequent experiments. Samples were characterized by Fourier infrared spectroscopy, X-ray diffraction, Raman spectroscopy and thermogravimetric analysis. The friction test is carried out by the relative movement of the copper ball and the aluminum disk on the friction tester.FindingsResults showed that the friction coefficient of MAO samples was reduced by 80% after treated with GO–PVA composite film.Originality/valueThis research has made a certain contribution to the surface hardness and tribological issues involved in the lightweight design of aluminum alloys.Peer reviewThe peer review history for this article is available at: https://publons.com/publon/10.1108/ILT-12-2023-0427/

Nanofibrous membranes modified by zwitterionic polyelectrolyte brushes for effective adsorption of ciprofloxacin hydrochloride

In this study, zwitterionic polyelectrolyte brushes poly(2-methacryloyloxyethyl phosphorylcholine) (PMPC) were grafted on poly (vinyl alcohol)/graphene oxide (PVA/GO) nanofibrous membranes by surface-initiated activators generated by electron transfer for atom transfer radical polymerization (AGET ATRP). The obtained PVA/GO@PMPC nanofibrous membranes were used as adsorbents for removal of ciprofloxacin hydrochloride. The membrane prepared with the most amount of GO in the electrospinning solution and the highest MPC concentration during grafting polymerization displayed the largest adsorption amount of ciprofloxacin hydrochloride (245.6 mg/g). Within 15 h, the adsorption achieved equilibrium, and the removal process agreed well with pseudo-second-order kinetic model. At pH = 7.0, the maximum adsorption capacity was attained, and the adsorption capacity increased gradually with temperature. Study on adsorption mechanism revealed that π-π interactions, hydrogen bonding interactions and electrostatic interactions might be involved for removal of ciprofloxacin hydrochloride. After being repeatedly used for six times, binding affinity of the membrane did not change significantly. This study provided a general method for creating nanofibrous membranes with superior adsorption performance for removal of organic pollutants.

Non-volatile resistive switching behavior and time series analysis of Ag/PVA-graphene oxide/Ag device

Non-volatile memory devices have been getting significant attention from researchers worldwide in recent years due to their application in resistive random access memory and neuromorphic computing. Here, we have fabricated polyvinyl alcohol-graphene oxide (PVA-GO) composite as an active material for the resistive switching with different concentrations of GO (0.0, 0.1, 0.2, 0.3, 0.4, and 0.5 wt. % GO solution) dispersed in 5 wt. % PVA matrix in a 2:1 volume ratio. We demonstrate the non-volatile forming free resistive switching properties of Ag/PVA-GO/Ag devices. Structural properties of PVA-GO composites are established from the x-ray diffraction pattern, which indicates the complete dispersion of GO inside the PVA matrix. The Ag/PVA-GO-0.1 wt. %/Ag device shows better bipolar resistive switching at VSET ∼ 0.4 V and VRESET at ∼−0.8 V. This device indicates well-resolved two distinct states at a read voltage of 0.1 V in endurance and retention measurements. The fabricated device switches successfully tested for 2.5 × 103 cycles and retains its state for 3.36 × 103 s without any observable degradation. Furthermore, the non-volatile retention property was modeled using time series analysis. For this, Holt–Winter's exponential smoothing technique was utilized. Additionally, the charge–flux linkage characteristic shows the double-valued function, and time domain–charge and time domain–flux show asymmetric behaviors. The electrical conduction mechanism exhibits ohmic behavior in the entire region of the low resistance state and the lower voltage region of the high resistance state. In the high-voltage region of the high resistance state, the space charge-limited conduction mechanism is observed. The resistive switching behavior is explained with the help of an appropriate model.

Simultaneous Detection of Temperature, Strain, Refractive Index, and pH Based on a Phase-Shifted Long-Period Fiber Grating

A novel π-phase-shifted (PS) long-period fiber-grating (LPFG) sensor operating near the phase-matching turning point (PMTP) was proposed. The PS-LPFG sensor can simultaneously detect temperature, strain, refractive index (RI), and pH. Due to the introduction of π phase shift, the double resonance peak of the selected cladding mode was divided into four loss peaks, which is convenient for multiparameter measurement. By monitoring the resonant-wavelength shifts of four dips of PS-LPFG, simultaneous detection of temperature, strain, RI, and pH can be achieved. Moreover, using a simple LPFG design on one fiber and a multiparameter matrix algorithm, the crosstalk between multiple signals was eliminated. Graphene oxide/polyvinyl alcohol (GO/PVA) hydrogel was coated onto the grating sensing area to measure the change in pH, and the sensitivity was higher than that of the same type of fiber-grating sensor. Results showed that the maximum sensitivity of temperature, strain, RI, and pH of the fabricated phase-shifted grating sensing structure were 0.2128 nm/°C, 0.1225 nm/μϵ, 718 nm/RIU, and -1.0166 nm/pH, respectively. Overall, the proposed sensor had great potential applications in monitoring marine environments and biochemistry sensing.

Development of PVA/GO Nanocomposites Membranes for Air-Filtration and Purification

Climate change due to the air pollution is actually one of the largest environmental challenges worldwide. Preparation and development of stable and highly efficient nanocomposite membranes remain a significant goal because of its enormous importance of controlling the environment. This study investigated a simple synthesis of poly (vinyl alcohol)/graphene oxide (PVA/GO) nanocomposite membrane for air pollutant remediation. The chemical and physical structures, morphologies, and conductivities were investigated as a function of the GO loading. The objective of the present study was to evaluate the efficiency of novel PVA/GO membranes in the removal of both formaldehyde (FA) as a pollutant VOCs model and SO2 as a model of greenhouse gases. Furthermore, the purpose of this study is to identify good predictors for selecting the appropriate optimal GO content in GO/PVA nanocomposites that exhibit higher air pollutant removal performance as well as design an economical GO/PVA nanocomposite air purification system for removal of the air pollutants in the field. To our knowledge, field application of GO/PVA nanocomposite volatile organic compound (VOCS) filters and control of SO2 gas pollutants from indoor air has not yet been realized. The nanocomposite membranes with an optimum GO content exhibited higher removal performance for the FA gas pollutant, this enhancement reached 90% in the laboratory scale. However, during the application in the field, it showed 75% FA removed from the indoor air. These new nano-membranes reveal also wide efficiencies of SO2 removal (80%) when applied in the field. Therefore, this filter system proved an excellent efficacy in the removal of air pollutants and could be more promising in various industrial applications.

Characteristics of PVA/GO Composite Membranes Prepared Using Solution Casting Technique for Reducing Methylene Blue Concentration

In this study, the composite films of polyvinyl alcohol (PVA) and graphene oxide (GO) that referred as PVA/GO composites were prepared with a solution casting technique to be used as a filtration membrane. PVA/GO solution was prepared by mixing PVA powder, GO dispersion and aqueous solvent, then subjected to a hydrothermal process. The PVA/GO composite solution was cast on the glass substrate, then dried overnight so the solvent evaporated and then the composites films were removed from the substrate. The PVA/GO composite that characterized by SEM indicates that the GO is evenly dispersed within the PVA matrix. The FTIR spectrum of the composite has a sharp peak at 1655 cm-1 that associated with C=O and C=C bonds relating to GO characteristics. The TGA measurement results show that the PVA/GO composite film has better thermal stability than the PVA film. The PVA/GO composite films have been used as filtration membranes to reduce the concentration of methylene blue (MB) solutions contained in water. The filtration experiment that performed at various pressures showed that the permeability of the PVA/GO composite membranes was relatively constant at each pressure. Membrane permeability at pressures of 20 psi, 30 psi and 45 psi for PVA membranes are 1.95×10-3, 2.08×10-3 and 2.00×10-3 Darcy, while for PVA/GO composite membranes are 2.49×10-4, 1.22×10-3 and 2.23×10-3 Darcy

Abundant dynamics of group velocity locked vector solitons from Er-doped fiber laser based on GO/PVA film

Abstract With the insertion a segment of polarization-maintaining fiber (PMF) inside the cavity, abundant dynamics of group velocity locked vector solitons (GVLVSs) in Er-doped fiber laser have been investigated by using graphene oxide/polyvinyl alcohol (GO/PVA) film as a saturable absorber (SA). The generated Kelly sidebands in emission spectra reveal peak-valley or valley-peak alternation and slightly shift in two orthogonal components, which are the characteristics of GVLVSs. Through proper adjustment of polarization controllers (PCs) inside the EDFLs cavity, versatile vector soliton dynamics such as polarization locked GVLVSs (PL-GVLVSs), polarization rotation GVLVSs (PR-GVLVSs), dual wavelength GVLVSs, bound state GVLVSs, bunch GVLVSs and harmonic mode-locking GVLVSs (HML-GVLVSs) have been observed. The separation between two emission peaks from the dual wavelength GVLVSs was controlled by the Lyot filter and related to the insertion length of PMF inside the cavity. Unlike PL-GVLVSs, the period-doubling phenomenon has been found in two orthogonal components of the PR-GVLVSs. Besides, the bound state GVLVSs were generated showing strongly modulated interference fringes in emission spectrum. For the bunch and HML GVLVSs, the number of solitons inside the cavity increased with the pump power, and it showed the quintuple solitons and the 7th HML-GVLVSs at the highest pump power.

Resistive switching memory based on polyvinyl alcohol-graphene oxide hybrid material for the visual perception nervous system

Resistive random-access memory (RRAM) is a new memory technology that can not only realize high-density storage, but also can simulate the neural synapse for use in artificial intelligence applications. In this study, we propose an RRAM device that shows competitive resistive memory characteristics and can similarly be used as a synapse in simulation of the human visual perception nervous system. First, we demonstrate that the polyvinyl alcohol-graphene oxide (PVA@GO) hybrid material-based RRAM device offers competitive resistive memory characteristics, including long retention capability, high durability, repeatability, and mechanical flexibility. Second, we integrate the RRAM (as the artificial synapse) with a light-sensitive electronic component (a photoreceptor cell) to construct an artificial visual perception system, and realize effective emulation of light perception and conversion of light signals into synaptic signals. Under light irradiation at 532 nm, a range of versatile synaptic functions, including short-term plasticity (STP), long-term plasticity (LTP), and paired pulse facilitation (PPF), was imitated. This work provides valuable insight into the development path for next-generation high-density data storage technology, and also offers a new way to imitate the human visual neural network for multi-functional humanoid robots.

Twisted weakly coupled relative humidity sensor coated with a graphene oxide/polyvinyl alcohol composite.

A new coupled fiber optic humidity sensor based on a double-tapered fiber twisted weakly coupled structure coated with a graphene oxide/polyvinyl alcohol (GO/PVA) film has been reported for the first time, to the best of our knowledge. The sensor adopts a 2×2 coupler structure with a waist diameter of 20 µm. The GO/PVA composite film is coated in the weakly coupled area to increase the sensitivity of the sensor. The thickness of the coating layer is about 3 µm. The sensor can realize linear sensing in the relative humidity (RH) range of 45%-85%RH with a dynamic response time of 1.9 s and a recovery time of 5.7 s. The sensitivity of the sensor is up to 0.002/%RH, and the linearity of the sensor is as high as 98.65%. Moreover, the sensor has good stability, reversibility, and low-temperature crosstalk.

Sand coated with graphene oxide-PVA matrix for aqueous Pb2+ adsorption: Insights from optimization and modeling of batch and continuous flow studies

In the present study, a composite of graphene oxide-polyvinyl alcohol coated sand (GO-PVA@sand) was prepared and examined for adsorption of aqueous Lead ion (Pb2+) in batch and fixed-bed columns. The characterization of GO-PVA@sand revealed that GO-sheets were randomly immobilized into the PVA-matrix and formed a stable complex surrounding sands particles. And hence, preventing leaching of GO from the GO-PVA@sand and avoiding agglomeration of GO-PVA@sand inside the column that leads to no column chocking. The adsorption of Pb2+ onto GO-PVA@sand was endothermic in nature, attained equilibrium in ≤ 45 min, followed the pseudo-second-order kinetics, and the Langmuir adsorption isotherm with the maximum adsorption capacity of 8.25 mg/g. Moreover, the fixed-bed column study revealed that the adsorption capacity (qeq) decreased from 7.4 to 7.0 mg/g by increasing inlet flow rate from 5 to 15 mL/min because of drop in the contact time between Pb2+ and GO-PVA@sand. In contrast, the qeq increased from 7.2 to 7.6 mg/g, with an increase of bed-height from 2 to 6 cm, due to greater contact time and surface exposure. Besides increasing inlet concentration from 20 to 40 mg/L, the qeq increased from 7.2 to 8.0 mg/g, apparently because of the presence of a higher mass driving force. To understand the potential for process scale-up, breakthrough modeling was performed and found that the Thomas and Yoon-Nelson model best described the adsorption behavior. The post-adsorption characterization of GO-PVA@sand showed Pb2+ adsorbed through ion-exchange, cation-π, electrostatic interaction, and hydrogen bonding. The regeneration and reuse potential of the GO-PVA@sand up-to five adsorption-desorption cycles, signify its relevance in low-cost continuous water treatment.

Evaluation of Structural and Optical Properties of Graphene Oxide-Polyvinyl Alcohol Thin Film and Its Potential for Pesticide Detection Using an Optical Method

In the present work, graphene oxide (GO)–polyvinyl alcohol (PVA) composites thin film has been successfully synthesized and prepared by spin coating techniques. Then, the properties and morphology of the samples were characterized using Fourier transform infrared spectroscopy (FTIR), ultraviolet-visible spectroscopy (UV-Vis), and atomic force microscopy (AFM). Experimental FTIR results for GO–PVA thin film demonstrated the existence of important functional groups such as -CH2 stretching, C=O stretching, and O–H stretching. Furthermore, UV-Vis analysis indicated that the GO–PVA thin film had the highest absorbance that can be observed at wavelengths ranging from 200 to 500 nm with a band gap of 4.082 eV. The surface morphology of the GO–PVA thin film indicated the thickness increased when in contact with carbaryl. The incorporation of the GO–PVA thin film with an optical method based on the surface plasmon resonance (SPR) phenomenon demonstrated a positive response for the detection of carbaryl pesticide as low as 0.02 ppb. This study has successfully proposed that the GO–PVA thin film has high potential as a polymer nanomaterial-based SPR sensor for pesticide detection.

Boosting moisture induced electricity generation from graphene oxide through engineering oxygen-based functional groups

Harvesting energy from ubiquitous moisture is attracting growing interest for directly powering electronic devices. However, it is still challenging to fabricate high-performing moisture-electric generators (MEGs) with high and stable electric output. Herein, we report a simple strategy to modify the oxygen-based groups of graphene oxide using hydrochloric acid treatment, which boosts the electric output based on the device structure of graphene oxide/polyvinyl alcohol (GO/PVA) MEGs. The resulting MEG enables a stable voltage of 0.85 V and a current of 9.28 μA (92.8 μA∙cm-2), which are among the highest values reported so far. More excitingly, electric output gets further improved by simply assembling four MEG units in series or parallel. Moreover, the MEG shows great commercial potential for flexible and wearable applications. Driven by these advancements, the assembled MEGs can successfully power sensors and calculators. This work opens a new era of advance for a new energy conversion technology able to directly powering electronic devices.

Molecular simulation of enhanced separation of humid air components using GO-PVA nanocomposite membranes under differential pressures.

Hydrophilic nanocomposite membranes have significant advantages in the separation of water vapor which is the core process in air dehumidification. This paper focuses on exploring the micro-mechanism of enhanced separation using graphene oxide-polyvinyl alcohol (GO-PVA) nanocomposite membranes. The sorption and diffusion behaviors of water vapor and nitrogen in GO-PVA membranes were investigated using molecular dynamics (MD) and Monte Carlo (MC) methods. The study showed that embedding GO into a PVA matrix results in a higher glass transition temperature and fractional free volume. The latter is believed to enhance the diffusivity of gas molecules in polymeric membranes. The interaction between the polymer chains and GO nanoparticles notably promotes the adsorption capacity of water vapor and inhibits nitrogen adsorption in the membrane. A water vapor permeance of 8844.07 Barrer and a separation factor of 3.53 could be achieved with the GO-PVA-0.5 membrane. The analysis confirmed that GO has the same effect on single gas and binary gas mixtures, i.e., increasing the water vapor permeability and selectivity. The calculated water vapor permeance of binary gas is 83% lower than that of single gas permeation. It is expected that this research could provide fundamentals for the optimization and synthesis of gas separation membranes.

Polyvinyl Alcohol Polymer Functionalized Graphene Oxide Decorated with Gadolinium Oxide for Sequestration of Radionuclides from Aqueous Medium: Characterization, Mechanism, and Environmental Feasibility Studies.

Uranium (U(VI)) and thorium (Th(IV)) ions produced by the nuclear and mining industries cause water pollution, thereby harming the environment and human health. In this study, gadolinium oxide-decorated polyvinyl alcohol-graphene oxide composite (PGO–Gd) was developed using a simple hydrothermal process to treat U(VI) and Th(IV) ions in water. The developed material was structurally characterized by highly advanced spectroscopy and microscopy techniques. The effects of pH, equilibration time and temperature on both radionuclides (U(VI) and Th(IV)) adsorption by PGO–Gd were examined. The PGO–Gd composite adsorbed both metal ions satisfactorily, with adsorption capacities of 427.50 and 455.0 mg g−1 at pH 4.0, respectively. The adsorption properties of both metal ions were found to be compatible with the Langmuir and pseudo–second-order kinetic models. Additionally, based on the thermodynamic characteristics, the adsorption was endothermic and spontaneous. Furthermore, the environmental viability of PGO–Gd and its application was demonstrated by studying its reusability in treating spiked surface water. PGO–Gd shows promise as an adsorbent in effectively removing both radionuclides from aqueous solutions.

Preclinical assessment of chitosan–polyvinyl alcohol–graphene oxide nanocomposite scaffolds as a wound dressing

The present research aimed to examine the biological properties of chitosan (CS)–polyvinyl alcohol (PVA) scaffolds reinforced with graphene oxide (GO) nanosheets, as wound dressings. The scaffolds were characterized by various techniques. The scanning electron microscopy (SEM) and thermogravimetry analyses (TGAs) were used to investigate distribution of the GO within the polymer. The viscoelastic properties were evaluated by dynamic mechanical thermal analysis (DMTA) to examine the quality of a wound dressing. In vitro and in vivo studies were conducted to assess the biocompatibility of the scaffolds as wound dressing. The cell viability and proliferation results indicated that mouse fibroblast cells (L929) could adhere on the 50CS–50PVA/3 wt% GO scaffold. Herewith, the fabricated CS–PVA–GO nanocomposite scaffolds are suggested as promising biomaterials for skin tissue engineering and wound dressing.

Synthesis of graphene oxide/ polyvinyl alcohol (GO/PVA) composite film as an adsorbent

In this study, heavy metal ions or organic in the aqueous solution are removed by adsorbent without filtration or centrifugation as well as incorporate magnetic materials into the adsorbent. A composite film GO/PVA from PVA and self – synthesized GO by co - precipitation method has synthesized successfully. This composite was characterized by XRD, SEM, FT-IR to evaluate the properties of this material. The results showed that there was an interaction between GO and PVA so we have tested the adsorption capacity of this composite with Co(II) ions and the obtained efficiency of this process was 99.5% with the initial concentration of solution is 20 mg.L-1. This film is completely capable of removing heavy metal ions from waste water.

Temperature self-calibrated pH sensor based on GO/PVA-coated MZI cascading FBG.

A temperature self-calibrated potential of hydrogen (pH) sensor based on the single mode fiber-tapered dual core photonic crystal fiber-single mode fiber (SMF-TDCPCF-SMF) structure cascaded with a fiber Bragg grating (FBG) is proposed and demonstrated. The TDCPCF structure formed Mach-Zehnder interferometer (MZI) is modified with a coating of graphene oxide/polyvinyl alcohol (GO/PVA) hybrid hydrogel to realize the measurement of pH, and the uncoated FBG is used to calibrate temperature. In our experiment, the sensitivity coefficient of 0.69 nm/pH with R2=0.99 and the hysteresis loss of less than 0.007 are achieved within the pH range from pH 4.00 to pH 9.85. The measured response time from pH 7.00 to pH 4.00, 6.00 and 9.85 are no higher than 10s. Moreover, the resonant wavelengths of MZI and FBG also exhibit good linear relationship with the temperature sensitivity coefficient of 0.15 nm/°C (R2=0.99) and 0.09 nm/°C (R2=0.97) respectively. It is demonstrated successfully that the proposed sensor has broad application prospects in the field of environmental monitoring, biological sensing and chemical analysis, due to the good performance of the temperature self-calibrated pH monitoring, repeatability, linearity, response time and reversibility.

Study on the Adsorption of Methylene Blue on Graphene Oxide/ Polyvinyl Alcohol Composite Film

With the aim of investigate the adsorption capacity of graphene oxide/polyvinyl alcohol (GO/PVA) polymer (the adsorbent), methylene blue is selected as an object to assess the adsorption capacity. The results showed that, after 93 minutes, the adsorption get the equilibrium state and 86% of methylene blue is adsorbed. Temperature, pH are also studied to find the optimum conditions for the adsorption where by pH 7 has the highest adsorption capacity and in the base environment, the obtained adsorption capacity is very low (<0,15 mg/g).. Repeated this process triple times on the same adsorbent (the adsorbent is treated after using each time), there is still 80% of methylene blue is adsorbed. This make save the money and protect the environment so this material promises to be a suitable alternate for adsorbents.

Numerical simulation and optimal design of photonic crystal fiber hygrometer coated with PVA/GO composite film

In this paper, a new hygrometer sensor based on a taper-photonic crystal fiber (PCF)-dislocation structure coated with polyvinyl alcohol/graphene oxide (PVA/GO) composite film is proposed and analyzed by the beam propagation method (BPM) method and experimental measurement. Due to the moisture absorption characteristic, the refractive index (RI) of the PVA/GO composite film changes linearly, so the PCF RI interferometer can realize high sensitivity humidity detection. In order to further promote its sensing performance, we use CO2 laser lattice to optimize the sensor with a narrower linewidth and an enhanced RI sensitivity. By optimizing the sensing structure and testing the humidity sensitive film, the research results show that the humidity sensitivity can reach 0.0824 nm/%RH in the range of 20%RH-90%RH.

Synthesis and electrochemical properties of V2O5[rad]nH2O compound with reduced graphene oxide/polyvinyl alcohol film as the free-standing cathode for coin-typed aqueous Zn-ion batteries

Recently aqueous zinc-ion batteries (AZIBs) have been widely studied on the aspects of electrode materials and electrolytes, but it is still far from practical application. The limitation of AZIBs is that it is difficult to have both high specific capacity and good cycle stability. Herein, a free-standing cathode V2O5nH2O/reduced graphene oxide-polyvinyl alcohol (denoted as V2O5nH2O/rGO-PVA) film was synthesized by one-step hydrothermal method and vacuum filtration. As the cathode for the coin-typed AZIBs, the V2O5nH2O/rGO-PVA film cathode delivers the ultrahigh capacity of 553 mA h g−1 at the current density of 0.1 A g−1. And the capacity is 194 mA h g−1 at 0.5 A g−1, after 300 cycles, it still remains 152 mA h g−1. At the power density of 183 W·kg−1, the high energy density is calculated as 354 Wh·kg−1 based on the mass of the cathode. The energy storage mechanism was studied by some ex-situ characterizations as well. This work not only proposes a strategy for the synthesis of V2O5∙nH2O/rGO-PVA film, but also demonstrates that the as-obtained free-standing cathode is beneficial to the assembly of coin-typed AZIBs and exhibits excellent electrochemical performance.