Reduced Graphene Oxide Nanocomposite Films Research Articles

Titanium Dioxide Loaded Reduced Graphene Oxide Nanocomposite Film as Counter Electrodes for Dye-Sensitized Solar Cells

The demands on conventional fossil fuels are increasing especially developing countries. The growth of population among countries also put a lot of pressure on coil consumption and resulted effect of greenhouse. These phenomena will dramatically increase the global warming and pollutes the nature of earth. For the worse, it would forming some erratic patterns like flood, draughts, wildfire, and so on. Therefore, renewable solar energy is the key target to reduce the fossil fuel consumption, minimize global warming issues, and involuntary minimizes the erratic weather patterns. Dye-sensitized solar cell (DSSCs) is one of the promising prospects for efficient renewable resources. Most of the researchers were tried to use platinum as counter electrode to perform the photovoltaic studies. However, the platinum material will made higher for the entire fabrication cost. Recently, we demonstrated a counter electrode in DSSCs system using the low-cost titanium dioxide (TiO2) decorated reduced graphene oxide (rGO) nanocomposite film. The TiO2-rGO nanocomposite (TiO2-rGO NC) as counter electrode is addressed to minimize electron losses and hence rapid the rate of dye regeneration at ground state. Practically, TiO2-rGO NC synthesized via one-step hydrothermal method. The crystallinity, functional groups, element composition, and morphology of TiO2-rGO NC were comprehensively studied. One-step hydrothermal method revealed that Ti particles (∼60 nm) have capable bonded with rGO thin film, as agreement with XRD and FTIR results. In DSSCs photovoltaic performance, the optimized power conversion energy (PCE) of TiO2-rGO NC as counter electrode achieved a 2.90%, which achieved a desire performance as comparable with rGO and TiO2. In this work, the low-cost TiO2-rGO NC as counter electrode with suppressed recombination in DSSCs is studied.

Highly sensitive detection of rutin in pharmaceuticals and human serum using ITO electrodes modified with vertically-ordered mesoporous silica-graphene nanocomposite films.

Herein we report a simple and rapid approach to fabricate a vertically-ordered mesoporous silica-electrochemically reduced graphene oxide nanocomposite film (VMSF/ErGO) on an indium tin oxide (ITO) electrode surface by the electrochemically-assisted self-assembly (EASA) method, which is capable of greatly promoting the electroanalytical performance of rutin compared to the previously reported VMSF modified ITO electrode and, meanwhile, displaying excellent anti-fouling and anti-interference ability in pharmaceutical formulations and human serum. Due to the excellent electrocatalytic activity of ErGO and the synergistic enrichment effects from the π-π interaction of ErGO and the hydrogen bond effect from the VMSF, the present VMSF/ErGO/ITO sensor is able to detect rutin with a wide linear range, a high sensitivity and a low limit of detection. Moreover, the VMSF/ErGO/ITO electrode could retain the high sensing performance with high transmittance upon tailoring the concentration of the modified graphene oxide (GO), which provides a simple approach for modifying transparent ITO electrodes and could be potentially used for optoelectronic devices.

Zinc oxide: reduced graphene oxide nanocomposite film for heterogeneous photocatalysis

The nanocomposite film based on zinc oxide nanostructures and reduced graphene oxide bilayer (ZnO/rGO) was synthesized, characterized and tested for the photodegradation of model organic dye (methyl orange) in water. Specifically, the nanorods of zinc oxide were obtained by the hydrothermal methods on the surface of rGO bilayers deposited on the quartz surface. The kinetics of dye photodegradation was studied via measurement of variation of the optical density at the maximum observed for the dye at 465 nm. The photodegradation efficiency of methyl orange (MO) was found to be increased from 70 to 85% when the nanocomposite material was used instead of pure ZnO nanostructures. The reaction rate constants calculated using the first-order approximation were equal to 7.2 × 10−3 min−1, 1 × 10−3 min−1 and 1.4 × 10−2 min−1 for ZnO nanorods, rGO bilayer, and ZnO/rGO nanocomposite, respectively. Hence, the rate constants clearly indicate that ZnO and rGO are functioning in a synergistic manner in the fabricated nanocomposite photocatalyst. It is necessary to point that the sample keeps its integrity after multiple experiments that is important for practical applications. The obtained results evidently demonstrate potential of the nanocomposite films based on ZnO nanostructures and rGO bilayers for production of the efficient catalysts.

Rapid and Sensitive Determination of Vanillin Based on a Glassy Carbon Electrode Modified with Cu2O-Electrochemically Reduced Graphene Oxide Nanocomposite Film

A facile cuprous oxide nanoparticles functionalized electro-reduced graphene oxide modified glassy carbon electrode (denoted as Cu2O NPs-ERGO/GCE) was fabricated via a simple physical adsorption and electrochemical reduction approach. Cyclic voltammetry and second-order derivative linear scan voltammetry were used to investigate the electrocatalysis oxidation of vanillin on the Cu2O NPs-ERGO/GCE. The compound yielded a well-defined voltammetric response in 0.1 M H2SO4 at 0.916 V (vs. saturated calomel electrode (SCE)). A linear calibration graph was obtained in the concentration range of 0.1 μM to 10 μM and 10 μM to 100 μM, while the detection limit (S/N = 3) is 10 nM. In addition, the Cu2O NPs-ERGO/GCE presented well anti-interference ability, stability, and reproducibility. It was used to detect vanillin sensitively and rapidly in different commercial food products, and the results were in agreement with the values obtained by high performance liquid chromatography.

Improved dye entrapment–liberation performance at electrochemically synthesised polypyrrole–reduced graphene oxide nanocomposite films

In this work, we have reported the application of electropolymerised polypyrrole–reduced graphene oxide (Ppy–RGO) nanocomposite films as an effective tool for entrapping and liberating the model dye Acid Red 1, and thereby proposed this as an ecofriendly treatment for dye-containing textile effluents. Initially, a polypyrrole–graphene oxide (Ppy–GO) nanocomposite film was anodically synthesised by an in situ electropolymerisation of pyrrole and GO. The Ppy–GO film was then electrochemically reduced to form a Ppy–RGO nanocomposite film. The synthesised nanocomposite films were characterised by spectroscopy, microscopy, surface analysis and thermogravimetry. Brunauer, Emmett and Teller surface area analysis showed a 7.4-fold increase in surface area of Ppy–RGO films compared to that of $${\text{NO}}_{3}^{ - }$$ -polypyrrole films. In addition, based on tensile strength, Ppy–RGO films were demonstrated to be 12.7-folds mechanically stronger than $${\text{NO}}_{3}^{ - }$$ –Ppy films. When Acid Red 1 was entrapped in these films, an entrapment efficiency of as high as 95% for Acid Red 1 was achieved at Ppy–RGO films, which is significantly higher than 56% achieved at Ppy films. Similarly, while liberating the entrapped Acid Red 1 from the Ppy–RGO nanocomposite films, a liberation efficiency of 73% was estimated compared to 36% from the Ppy films.

How Beneficial Is Reduced Graphene Oxide (RGO) for Long-Term Photo Generated Charge Transport in Bismuth Titanate – RGO Nanocomposite Films?

This work delineates the results of a systematic analysis of the photoelectrochemical (PEC) and optical responses of reduced graphene oxide (RGO) combined with a representative multi-metal oxide – bismuth titanate (BTO) on films. We investigated the role of RGO as a promoter of charge separation and transport, by suppressing recombination loss of carriers in BTO. The micro-structure of the BTO/RGO composite observed using transmission, scanning electron, and atomic force microscopy, revealed a well-integrated, and highly porous morphology compared to pristine BTO film. The integration of BTO with RGO resulted in a ∼7 fold increase in photocurrent density with an optimal RGO loading of 2 wt%. The performance of the BTO/RGO interface was further examined to obtain critical insights on: (i) how the electrolyte influences the stability of the BTO/RGO composite and (ii) what interactions prevail at the BTO/RGO interface under long-term illumination that impact RGO stability. This work assumes immediate significance because implementation of RGO as a charge transport agent in oxidative systems is currently heavily researched. Unless we can determine a mechanism to protect RGO, its long-term stability, especially under oxidative conditions of any form, must be thoroughly investigated on a case-by-case basis to ensure composite longevity.

A facile one step electrostatically driven electrocodeposition of polyviologen–reduced graphene oxide nanocomposite films for enhanced electrochromic performance

Polyviologen (PV)–reduced graphene oxide (rGO) nanocomposite films were fabricated by simple, one-step reductive electropolymerization of cyanopyridinium based precursor monomer (CNP) in an aqueous dispersion of graphene oxide (GO). Since the polymer formation and reduction of graphene oxide occurs within the same potential window, electrocodeposition method was preferred for obtaining nanostructured PV–rGO films. Cyclic voltammetry experiments of PV–rGO displayed two well resolved, reversible one-electron redox processes typical of viologen. Being a redox polymer, incorporation of rGO further enhances the electroactivity of the PV in the composite films. Vibrational spectral analysis with surface characterization revealed structural changes after composite formation along with subsequent reduction of GO within the polymer matrix. The PV–rGO nanostructured film exhibits a high-contrast electrochromism with low driving voltage induced striking color changes from transparent (0V) to purple (−0.6V), high coloration efficiency, fast response times and better cycling stability compared to a pristine PV film. This improved performance can be attributed to the high stability of the electrochrome in the composite assembly induced by electrostatically driven non-covalent interactions between redox PV2+ and negatively charged rGO, improved electrical conductivity and enlarged surface area accessed through reinforced nanostructured graphene sheets for tethering PV molecules.

Photoinduced superhydrophilicity and high photocatalytic activity of ZnO–reduced graphene oxide nanocomposite films for self-cleaning applications

A series of ZnO–reduced graphene oxide (ZnO–rGO) nanocomposite films were developed on glass substrate by a sol–gel technique. The deposited films were highly transparent and showed enhanced photocatalytic activity with increasing rGO content. Significantly, the films showed surface hydrophilicity and photoinduced superhydrophilicity that enhanced with the increase of rGO/ZnO ratio. The enhancement of photocatalytic activity of ZnO–rGO films with increasing rGO/ZnO ratio is attributed to the enhancement of their efficient charge separation owing to electrons injection from the conduction band of ZnO to graphene, the decrease of average particle size, and the increase of superhydrophilicity. The promising characteristics (inexpensive, transparent, photoinduced superhydrophilic, and highly photocatalytically active) make the ZnO–rGO films have the potential use in self-cleaning and various indoor applications.

Improved energy harvesting capability of poly(vinylidene fluoride) films modified by reduced graphene oxide

Piezoelectric energy harvesters can be used to convert ambient energy into electrical energy and power small autonomous devices. In recent years, massive effort has been made to improve the energy harvesting ability in piezoelectric materials. In this study, reduced graphene oxide was added into poly(vinylidene fluoride) to fabricate the piezoelectric nanocomposite films. Open-circuit voltage and electrical power harvesting experiments showed remarkable enhancement in the piezoelectricity of the fabricated poly(vinylidene fluoride)/reduced graphene oxide nanocomposite, especially at an optimal reduced graphene oxide content of 0.05 wt%. Compared to pristine poly(vinylidene fluoride) films, the open-circuit voltage, the density of harvested power of alternating current, and direct current of the poly(vinylidene fluoride)/reduced graphene oxide nanocomposite films increased by 105%, 153%, and 233%, respectively, indicating a great potential for a broad range of applications.

A novel lable-free electrochemical immunosensor for carcinoembryonic antigen based on gold nanoparticles–thionine–reduced graphene oxide nanocomposite film modified glassy carbon electrode

In this paper, gold nanoparticle–thionine–reduced graphene oxide (GNP–THi–GR) nanocomposites were prepared to design a label-free immunosensor for the sensitive detection of carcinoembryonic antigen (CEA). The nanocomposites with good biocompatibility, excellent redox electrochemical activity and large surface area were coated onto the glassy carbon electrode (GCE) surface and then CEA antibody (anti-CEA) was immobilized on the electrode to construct the immunosensor. The morphologies and electrochemistry of the formed nanocomposites were investigated by using scanning electron microscopy (SEM), ultraviolet–visible (UV–vis) spectrometry, electrochemical impedance spectroscopy (EIS) and cyclic voltammetry (CV). CV and differential pulse voltammetry (DPV) studies demonstrated that the formation of antibody–antigen complexes decreased the peak current of THi in the GNP–THi–GR nanocomposites. The decreased currents were proportional to the CEA concentration in the range of 10–500pg/mL with a detection limit of 4pg/mL. The proposed method was simple, fast and inexpensive for the determination of CEA at very low levels.