Graphene Oxide/reduced Graphene Oxide Research Articles

Efficacy of Graphene-Based Nanocomposite Gels as a Promising Wound Healing Biomaterial.

The development of biocompatible nanocomposite hydrogels with effective wound healing/microbicidal properties is needed to bring out their distinguished characteristics in clinical applications. The positive interaction between graphene oxide/reduced graphene oxide (GO/rGO) and hydrogels and aloe vera gel represents a strong strategy for the advancement of therapeutic approaches for wound healing. In this study, the synthesis, characterization, and angiogenic properties of graphene-based nanocomposite gels have been corroborated and substantiated through several in vitro and in vivo assays. In this respect, graphene oxide was synthesized by incorporating a modified Hummer's method and ascertained by Raman spectroscopy. The obtained GO and rGO were uniformly dispersed into the aloe vera gel and hydrogel, respectively, as wound healing materials. These formulations were characterized via in vitro bio-chemical techniques and were found suitable for the appropriate cell viability, attachment, and proliferation. In addition, in vivo experiments were conducted using male Wistar rats. This revealed that the GO/rGO-based gels stimulated wound contraction and re-epithelialization compared to that of the non-treatment group. From the study, it is suggested that GO/rGO-based aloe vera gel can be recommended as a promising candidate for wound healing applications.

Quaternary Artificial Nacre-Based Electronic Textiles with Enhanced Mechanical and Flame-Retardant Performance

Interest in wearable electronics has led to extensive studies on woven textiles that are mechanically robust and stretchable, have high electrical conductivities, and exhibit fire resistance properties even at high temperatures. We demonstrate a highly easy and scalable method for fabricating defect-free graphene (dfG) nacre-based woven electronic textiles (e-textiles) with enhanced flame-retardant properties and high electronic conductivities. The as-prepared graphene shows perfect preservation of its inherent properties without any crystal damage during subsequent exfoliation and noncovalent melamine functionalization. The defect-free graphene functionalized by melamine (m-dfG) is well dispersed in various polar solvents. To investigate the synergistic effect of m-dfG, quaternary artificial nacre composites are fabricated by adding manganese(II) chloride to a m-dfG/polymer (carboxymethyl cellulose (CMC)) composite. Their mechanical, electrical, and thermal characteristics are then evaluated. The quaternary m-dfG-Mn2+-CMC artificial nacre exhibits exceptionally enhanced mechanical properties (tensile strength: 613.9 MPa; toughness: 7.13 MJ m-3) and the best flame retardancy (even at torch heating) as compared to those of graphene oxide/reduced graphene oxide (GO/rGO)-based nacres. In this context, our approach will be helpful to future wearable electronics and fire-retardant textiles with high strength, which can accelerate the commercial viability of e-textiles.

Nanometric and surface properties of semiconductors correlated to photocatalysis and photoelectrocatalysis applied to organic pollutants – A review

This review study summarizes relevant topics about the photoelectrocatalytic semiconductors for the degradation of organic pollutants. Among the topics are A) the basic concepts of photocatalysis and photoelectrocatalysis for the advanced oxidation of organics in water. B) The band theory about heterojunctions, Schottky barriers, and doping of these semiconductors being photocatalysts. C) Proposing the outlook for photocatalysts, as those systems arranging doped semiconductors with heterojunctions and having Schottky junctions, a set of tables and sections show reported cases that complement the semiconductor characteristics providing the percentage of degradation attained, such as photoanodes of Boron-doped TiO2 nanotubes, TiO2 - Sb2S3 composites, and so forth. D) The novel characteristics of graphene-based materials for improving photoelectrocatalytic systems. E) A systematic way of classifying and understanding photoelectrocatalytic semiconductors based on their relevant characteristics and photoelectrochemical mechanisms. Moreover, this work shows the photoelectrocatalytic properties of the recently reported graphene oxide - reduced graphene oxide (GO-rGO) nanohybrids, which can also be used for the degradation of organic pollutants. Finally, based on all the previously gathered and summarized information, some inferences are made about the photoelectrocatalytic properties of some GO-rGO based heterojunctions for the degradation of organic pollutants.

Light-driven diffraction grating based on a photothermal actuator incorporating femtosecond laser-induced GO/rGO.

A light-driven diffraction grating incorporating two grating patterns with different pitches atop a photothermal actuator (PTA) has been proposed. It is based on graphene oxide/reduced graphene oxide (GO/rGO) induced via femtosecond laser direct writing (FsLDW). The rGO, its controllable linewidth, and transmission support the formation of grating patterns; its noticeably small coefficient of thermal expansion (CTE), good flexibility, and thermal conductivity enable the fabrication of a PTA consisting of a polydimethylsiloxane layer with a relatively large CTE. Under different intensities of light stimuli, diffraction patterns can be efficiently tailored according to different gratings, which are selectively addressed by incident light beam hinging on the bending of the PTA. This is the first demonstration of combining gratings and PTA, wherein the GO plays the role of a bridge. The light-driven mechanism enables the contactless operation of the proposed device, which can be efficiently induced via FsLDW. The diffraction angle could be changed between 2° and 6° horizontally, and the deviation of side lobes from the main lobe could be altered vertically in a continuous range. The proposed device may provide powerful support for activating dynamic diffraction devices in photothermally contactless schemes.

Low cost flexible pressure sensor using laser scribed GO/RGO periodic structure for electronic skin applications

Abstract Considering electronic skin applications, a pressure sensor based on periodic structure of graphene oxide-reduced graphene oxide (GO-rGO) has been designed and fabricated based on a low cost direct laser writing technique by utilizing the laser diode of DVD drive's pickup head. The optimization of sensor structure has been performed using computational modelling through Finite Element Method (FEM) in the COMSOL environment. The optimized structure is fabricated based on the deposition of thin layer of GO on the surface of Kapton and the pattering is performed by laser irradiation. The fabricated sensor structure has been characterized structurally and functionally. The results show that the fabrication method is successful in the formation of periodic structure of GO-rGO and the sensor has an acceptable response in the range of 1.5–40 kPa.

Photocatalytic reduction of carbon dioxide using graphene oxide wrapped TiO2 nanotubes

Photocatalytic conversion of carbon dioxide to valuable chemicals by using semiconductor materials is one of the major challenges in materials science. Higher efficiency and product yield can be achieved by designing of a suitable photocatalyst with retarded recombination of photogenerated electron-hole pair and sufficient potential for the reduction of CO2. In this work, unique composite architecture of graphene-oxide wrapped TiO2 nanotubes for the photocatalytic reduction of CO2 has been developed. The TiO2 nanotubes formed by electrochemical anodization are wrapped with graphene oxide/reduced graphene oxide (GO/rGO) layers which also form interconnecting bridges between the adjacent nanotubes. Such a unique nanostructure helped the separation of photogenerated electron-hole pairs with better charge transfer to perform the reduction of adsorbed CO2 molecules. The rGO/TiO2 multi-leg nanotubes (MLNTs) have shown the highest photocatalytic activity with maximum yield of CO c.a. 1348 μmol g−1 within the first 20 min, which stabilize to about 760 μmol g−1 after 2 h of UV-A irradiation. More importantly, the CO formation rate is about an order of magnitude higher than that from graphene supported TiO2 nanocrystals.

Ultra-sensitive and selective label free electrochemical DNA detection at layer-by-layer self-assembled graphene oxide and vesicle liposome nano-architecture

Liposomes are self-assembled successfully on graphene oxide/reduced graphene oxide (GO/rGO) composite supported on a gold electrode for the ultra-sensitive and selective label free detection of target DNA in presence of gold nanoparticle electrochemically for the first time. This work used the chemically synthesized GO for controlling the bilayer to vesicle structure of cationic DOTAP by the simultaneous control of GO hydrophobic character and oxy functional group spacing. This has been achieved by two different approaches: (i) the traditional physical mixing of ascorbic acid reduced GO with the unreduced GO to form a trilayered rGO/GO/rGO network and (ii) in another method, the rGO was prepared electrochemically by the controlled potential reduction of acid functional groups on the GO in sulphuric acid medium (ErGO). Both these methods produce graphene surfaces with evenly spaced functional groups and low hydrophobic character which are essential to prevent liposome vesicle fusion on the GO surface. Electrochemical and quartz crystal micro balance techniques (QCM) suggest more adsorption of the vesicles on the ErGO than on the GO/rGO assembly. These surfaces are further decorated with gold nanoparticles to anchor single stranded DNA to detect target DNA ultrasensitively in the presence of ferri/ferro cyanide redox probe. When the complementary hybridization decreases the redox peak current in cyclic voltammetry, the non-complementary hybridization does not show any obvious change in the peak currents. The intact spherical liposome on the GO/rGO and ErGO promotes the ultrasensitive detection of target DNA and showed the lowest detection limit of 1.29×10−17M with a broad linear range 10−17–10−8M. The bilayered liposome/AuNP structures on the AuE, GO and rGO do not show any selectivity for DNA detection. The constructed sensor is stable, selective and sensitive with fast response time ensuing its applicability in molecular diagnosis.

Thermoresponsive Deformable Actuators Prepared by Local Electrochemical Reduction of Poly(N-isopropylacrylamide)/Graphene Oxide Hydrogels

Inspired by the shape deformations of plants with inhomogeneous structures, more and more attention has been paid to prepare deformable actuators with inhomogeneous structures and precisely program their shape deformations. Here, we report a simple and novel method to prepare graphene oxide/reduced graphene oxide (GO/RGO) nanocomposite hydrogel-based deformable actuators by local electrochemical reduction of homogeneous poly(N-isopropylacrylamide)/GO (PNIPAM/GO) hydrogels. GO nanosheets in PNIPAM/GO hydrogels can be reduced in an electrolytic cell made of two indium–tin oxide (ITO) glass plates, and local reduction can be realized by pasting patterned insulating stickers onto the cathodal ITO glass plate. The reduction of GO nanosheets leads to the breakage of hydrogen bonding between GO nanosheets and PNIPAM chains and hence lower cross-linking densities of the reduced regions. Therefore, the difference in the swelling/deswelling behaviors between the reduced and unreduced sides (or regions) enables the ...

Transparent, Luminescent, Antibacterial and Patternable Film Forming Composites of Graphene Oxide/Reduced Graphene Oxide

Multifunctional graphene oxide/reduced graphene oxide (GO/RGO) composites were prepared through electrostatic interaction using biocompatible ingredients. Different functionalities were added to GO/RGO by anchoring materials such as native lactoferrin (NLf), NLf protected Au clusters (designated as Au@NLf), chitosan (Ch) and combinations thereof. Anchoring of Ch and NLf enhances the antibacterial property of RGO/GO. The addition of Ch to RGO/GO not only helped in forming stable dispersions but also helped in fabricating large (cm(2)) area films through a simple solvent evaporation technique. Functionalities such as photoluminescence were added to Ch-RGO/GO composites by anchoring Au@NLf on it. The composites thus formed showed stable luminescence in presence of various metal ions in the solid state. The composite showed reasonable stability against pH and temperature variations as well. The as-prepared films were transparent and the transparency could be modulated by controlling the concentration of RGO/GO in the composite. The antibacterial property and ability to form stable thin films may provide an opportunity to use such composites for medical and environmental remediation applications as well. Erasable patterns were fabricated on the film by stamping required patterns under compressive pressure. Luminescent patterns can be inscribed on the film and can be erased by simply wetting it. Such films with erasable information may be useful for security applications.