Polyvinyl Alcohol Graphene Oxide Research Articles

In-situ reduced graphene oxide-polyvinyl alcohol composite coatings as protective layers on magnesium substrates

A simple and feasible method was developed to fabricate in-situ reduced graphene oxide-polyvinyl alcohol composite (GO-PVA) coatings as protective layers on magnesium substrates. Polyvinyl alcohol was used as an in-situ reductant to transform GO into reduced GO. Contiguous and uniform GO-PVA coatings were prepared on magnesium substrates by dip-coating method, and were further thermally treated at 120°C under ambient condition to obtain in-situ reduced GO-PVA coatings. Owing to the reducing effect of PVA, thermal treatment at low temperature led to effective in-situ reduction of GO as confirmed by XRD, Raman, FTIR and XPS tests. The corrosion current density of magnesium substrates in 3.5wt% NaCl solution could be lowered to its 1/25 when using in-situ reduced GO-PVA coatings as protective layers.

Hierarchical and reversible assembly of graphene oxide/polyvinyl alcohol hybrid stabilized Pickering emulsions and their templating for macroporous composite hydrogels

Control over the reversible assembly of micro- and nano-scopic building blocks is highly important but very challenging in the fabrication of many hierarchical composite materials. Here we report the reversible assembly of emulsion micro-droplets stabilized by graphene oxide/polyvinyl alcohol (GO/PVA) hybrid via simply controlling the hydrogen bonding interaction between GO and PVA. The assembled emulsion droplets at acidic condition can be shaped into different macroscopic objects with a high degree of morphological control through injection molding. Attributed to the reversible hydrogen bonding interactions, the assembled emulsion monoliths/aggregates can be interestingly disassembled back into dispersed droplets when increasing the pH of aqueous phase. Utilizing this GO/PVA hybrid stabilized emulsion as a template, macroporous composite hydrogel was produced via facile polymerization of the aqueous phase, which can be further used for selective payload release, for example, anticancer drug Doxorubicin hydrochloride (DOX). It revealed that DOX release from the composite hydrogels was considerably accelerated when the pH of release medium decreased from 7.4 to 4.0, and the release DOX remained biologically active and had high capability to kill cancer cells, demonstrating the feasibility of using GO/PVA macroporous composite hydrogels as potential drug delivery platforms for cancer treatments.

Tuning optical and three photon absorption properties in graphene oxide-polyvinyl alcohol free standing films

We report the optical and nonlinear optical properties of graphene oxide (GO)-polyvinyl alcohol (PVA) free standing films. The composite polymer films were prepared in ex-situ method. The variation in optical absorption spectra and optical constants with the amount of GO loading was noteworthy from the optical absorption spectroscopic studies. Nonlinear optical studies done at 532 nm using 5 ns laser pulses show three photon absorption like behaviour. Both steady state and time resolved fluorescence studies reveal that the GO was functioning as a pathway for the decay of fluorescence from PVA. This is attributed to the energy level modifications of GO through hydroxyl groups with PVA. Raman spectroscopy also supports the interaction between GO and PVA ions through OH radicals.

Biomimetic jellyfish-like PVA/graphene oxide nanocomposite hydrogels with anisotropic and pH-responsive mechanical properties

Jellyfish mesogloea with a well-developed anisotropic microstructure exhibits excellent and pH-responsive mechanical properties. It remains a great challenge to fabricate hydrogels mimicking the hierarchical structures and intriguing properties of biological hydrogels. Here we report the fabrication of a biomimetic jellyfish-like polyvinyl alcohol/graphene oxide (PVA/GO) nanocomposite hydrogel through a convenient and effective directional freezing–thawing technique. The resulting hydrogels show microstructures, water contents, and mechanical properties very similar to those of jellyfish mesogloea. Free-standing PVA/GO hydrogels with extremely high water contents (97–99 wt%) are obtained. The hydrogels show anisotropic porous structures consisted of microsized fibers and lamellae. The hydrogels exhibit high tensile and compressive strengths, up to 0.17 MPa and more than 2 MPa, respectively. In addition, anisotropic tensile mechanical properties are also observed. More interestingly, the PVA/GO nanocomposite hydrogels exhibit pH-responsive mechanical properties, which become weaker when swollen in acidic and basic solutions. Jellyfish-like structure that can mimic the swimming style of jellyfish is constructed with the PVA/GO nanocomposite hydrogel. This study might provide new idea for designing and fabricating novel biological or bio-inspired hydrogels for various applications in biomedical, industrial, and soft robotics fields.

Adsorption of Cu2+and Cd2+from aqueous solution by novel electrospun poly(vinyl alcohol)/graphene oxide nanofibers

Novel poly(vinyl alcohol)/graphene oxide (PVA/GO) nanofibers were fabricated by electrospinning and applied to remove Cu2+ and Cd2+ from aqueous solution. The adsorption performances of the PVA/GO nanofibers were investigated by removing Cu2+ and Cd2+. The results showed that the adsorption of Cu2+ and Cd2+ onto PVA/GO nanofibers increased as the pH was increasing, but only slightly reduced with the increasing of ionic strength. The adsorption could reach equilibrium within 25 min and the experimental kinetic data followed the pseudo-second-order kinetic model. The equilibrium adsorption data can be well fitted with the Langmuir model. The thermodynamic parameters calculated from adsorption isotherms at four different temperatures indicated that the adsorption processes were endothermic and spontaneous. The PVA/GO nanofibers have good regeneration ability and can be recycled 8 times with a small amount of loss in adsorption efficiency. FTIR and XPS results indicated that the carboxyl and the carbonyl groups of GO on the surface of the nanofibers mainly participated in the adsorption of Cu2+ and Cd2+.

Graphene-oxide modified polyvinyl-alcohol as microbial carrier to improve high salt wastewater treatment

This work discussed the preparation and characterization of graphene oxide (GO) modified polyvinyl alcohol (PVA) for bacteria immobilization to enhance the biodegrdation efficiency of saline organic wastewater. GO–PVA material has lamellar structure with higher surface area to support bacterial growth and high salinity tolerance. It significantly stimulated the bacterial population by 1.4 times from 2.07×103CFU/mL to 5.04×103CFU/mL, and the microbial structure was also improved for salinity tolerance. Acinetobacter, Pseudomonas and Thermophilic hydrogen bacilli were enriched inside GO–PVA materials for glucose biodegradation. Compared to the CODCr removal efficiency with only PVA as the carrier (52.8%), GO–PVA material had better degradation performance (62.8%). It is proved as a good candidate for bioaugmentation to improve biodegradation efficiency in hypersaline organic wastewater.

Flexible, robust and highly efficient broadband nonlinear optical materials based on graphene oxide impregnated polymer sheets

We report a simple solution-processed method for the fabrication of low-cost, flexible optical limiting materials based on graphene oxide (GO) impregnated polyvinyl alcohol (PVA) sheets. Such GO–PVA composite sheets display highly efficient broadband optical limiting activities for femtosecond laser pulses at 400, 800, and 1400 nm with very low limiting thresholds. Femtosecond pump–probe measurement results revealed that nonlinear absorption played an important role for the observed optical limiting activities. High flexibility and efficient optical limiting activities of these materials allow these composite sheets to be attached to nonplanar optical sensors in order to protect them from light-induced damage.

Flexible and transparent resistive switching devices using Au nanoparticles decorated reduced graphene oxide in polyvinyl alcohol matrix

We have investigated the resistive switching mechanism in solution processed Au-reduced graphene oxide-polyvinyl alcohol (PVA) nanocomposites on flexible substrates. Monodispersed gold nanoparticles (Au NPs) attached to reduced graphene oxide (RGO) in aqueous PVA solution have been synthesized using a novel one pot technique. The fabricated hybrid device showed high On/Off switching ratio more than 103 with low operating voltages. The performance of hybrid device can be effectively enhanced over control RGO device. The switching mechanism occurs from the electrochemical reduction/oxidation process of partially reduced graphene oxide. The proposed devices reveal superior asymmetric bipolar resistive switching characteristics attractive for solution processable flexible and transparent non-volatile memory applications.

A systematic study of the effect of molecular weights of polyvinyl alcohol on polyvinyl alcohol-graphene oxide composite hydrogels.

Polyvinyl alcohol (PVA) hydrogels have been proposed for use as promising biomaterials in biomedical and tissue engineering, and graphene oxide (GO) has been recognized as a unique two-dimensional building block for various graphene-based supramolecular architectures. In this article, we systematically studied the influence of three kinds of PVA with different molecular weights on the interaction between PVA and GO. Moreover, the effects of PVA on the gelation of GO were also investigated. The native PVA hydrogel, as well as PVA-GO hybrid hydrogels, have been thoroughly characterized by the phase behavior study and various techniques including field emission scanning electron microscopy (FE-SEM), Fourier transform infrared (FT-IR) spectroscopy, thermogravimetric analysis (TGA) and rheological measurements. It can be seen that with the increase of the molecular weight of PVA, the addition of GO can effectively promote the gelation of PVA which can be reflected by a decrease of the critical gel concentration (CGC) for PVA-GO hydrogels. Dye adsorption experiments indicate that the toxic dye, i.e., methylene blue (MB), was efficiently entrapped in the PVA-GO xerogels. It is also demonstrated that the gelation of PVA and GO composites can be promoted by different supramolecular interactions, including hydrogen bonding and electrostatic interaction. This work indicates that the PVA-GO composite is a good candidate for preparing "super" and "smart" hydrogels and will enable further studies on the supramolecular chemistry of PVA, graphene and its derivatives.

Mode-locked Nd: GdVO4 laser with graphene oxide/polyvinyl alcohol composite material absorber as well as an output coupler

Graphene oxide/polyvinyl alcohol (GO/PVA) composite material saturable absorbers were fabricated. Sandwich structured GO/PVA absorber was used as an absorber as well as an output coupler in mode-locked Nd: GdVO4 laser. The laser pulses with the duration of 12ps, repetition rate of 120MHz and the maximum average output power of 680mW were produced.

Computational Investigation on the Effect of Graphene Oxide Sheets as Nanofillers in Poly(vinyl alcohol)/Graphene Oxide Composites

Poly(vinyl alcohol)/graphene oxide (PVA/GO) composites were studied by molecular mechanics and molecular dynamics methods to analyze the effect of GO sheet addition on PVA material. The properties ...