Reducing Agent For Graphene Oxide Research Articles

Effect of a Ag-rGO structure on the SERS activity of PEDOT:PSS films

π-Conjugated organic semiconductors with tunable electronic structures are new prospective active substrate materials for surface-enhanced Raman scattering (SERS). However, observing higher SERS activity when using organic semiconductors as substrates could be difficult because there is no plasmonic effect of hot electrons. Here, we designed a Ag-reduced graphene oxide (rGO) structure, introduced it into a poly(3,4-ethylenedioxythiophene)-poly(styrene sulfonate) (PEDOT:PSS) solution, and spin-coated the solution to obtain a Ag-rGO/PEDOT:PSS (ARPP) film. Our analyses demonstrate that the introduction of this Ag-rGO structure can not only enhance the electromagnetic field effect based on plasmon resonance but also improve the interaction between the target molecule and the substrate in the ARPP film. This innovative approach not only improves the SERS activity of π-conjugated organic polymers but also provides novel ideas for the preparation of other organic semiconductor-based SERS substrates.

Antimicrobial waterborne acrylic paint by the additive of graphene nanosheets/silver nanocomposite

In this work, the use of the nanocomposite of silver nanoparticles (NPs) and reduced graphene oxide (RGO), Ag-RGO, as a promising antibacterial agent to water-based acrylic paints has been investigated. The hybrid nanomaterial represented a strong antibacterial activity against two bacteria strains of Gram-negative of Escherichia coli (E. coli) and Gram-positive of methicillin-resistant Staphylococcus aureus (S. aureus). To prepare the antibacterial paint, 190 ppm Ag-RGO was added to the paint under sonication. By increasing the concentration of Ag-RGO in paint, the inhibition efficiency increased. The atomic force microscopy images showed that after 24 h incubation of E. coli and S. aureus bacteria with the antibacterial paint, their lengths decrease and degrade. The antibacterial activity of antibacterial paint against S. aureus was greater than that of E. coli. Also, the antibacterial activity of Ag NPs, RGO, and Ag-RGO was investigated. Among these nanomaterials, Ag-RGO has the highest antibacterial property so that its value of minimum inhibitory concentration for both E. coli and S. aureus is the same as 230 ppm. The minimum bactericidal concentration values for Ag-RGO was measured as 330 and 280 ppm for E. coli and S. aureus, respectively.

A Brief Review: The Use of L-Ascorbic Acid as a Green Reducing Agent of Graphene Oxide.

The reduced form of graphene oxide (r-GO) represents a versatile precursor to obtain graphene derivatives. Graphene oxide (GO) consists of a layered material based on a carbon skeleton functionalized by different oxygen-containing groups, while r-GO is obtained by the almost complete removal of these oxygen-containing functional groups. The r-GO has mechanical, electrical, and optical properties quite similar to graphene, thus, it proves to be a convenient 2D material useful for many technological applications. Nowadays, the most important aspects to consider in producing r-GO are: (i) the possibility of obtaining the highest reduction grade; (ii) the possibility of improving the dispersion stability of the resulting graphene using surfactants; (iii) the use of environmentally friendly and inexpensive reducing agents. Consequently, the availability of effective soft-chemistry approaches based on a green reducing agent for converting GO to r-GO are strongly needed. Among the green reductants, the most suitable is L-ascorbic acid (L-aa). Different studies have revealed that L-aa can achieve C/O ratio and conductivity values comparable to those obtained by hydrazine, a typical reducing agent. These aspects could promote an effective application strategy, and for this reason, this review summarizes and analyzes, in some detail, the up-to date literature on the reduction of GO by L-aa. The results are organized according to the two most important approaches, which are the reduction in liquid-phase, and the reduction in gel-phase. Reaction mechanisms and different experimental parameters affecting the processes were also compared.

Highly Sensitive Detection of Carbaryl Pesticides Using Potentiometric Biosensor with Nanocomposite Ag/r-Graphene Oxide/Chitosan Immobilized Acetylcholinesterase Enzyme

Novel, sensitive, selective, efficient and portable electrochemical biosensors are needed to detect residual contaminants of the pesticide 1-naphthyl methylcarbamate (carbaryl) in the environment, food, and essential biological fluids. In this work, a study of nanocomposite-based Ag reduced graphene oxide (rGO) and chitosan (CS) that optimise surface conditions for immobilisation of acetylcholinesterase (AChE) enzyme to improve the performance of catalytic biosensors is examined. The Ag/rGO/CS nanocomposite membrane was used to determine carbaryl pesticide using a potentiometer transducer. The AChE enzyme-based biosensor exhibits a good affinity for acetylthiocholine chloride (ATCl). It can catalyse the hydrolysis of ATCl with a potential value of 197.06 mV, which is then oxidised to produce a detectable and rapid response. Under optimal conditions, the biosensor detected carbaryl pesticide at concentrations in the linear range of 1.0 × 10−8 to 1.0 μg mL−1 with a limit of detection (LoD) of 1.0 × 10−9 μg mL−1. The developed biosensor exhibits a wide working concentration range, detection at low concentrations, high sensitivity, acceptable stability, reproducibility and simple fabrication, thus providing a promising tool for pesticide residue analysis.

Photocatalytic degradation of Janus Green Blue dye in wastewater by green synthesised reduced graphene oxide-silver nanocomposite

ABSTRACT In this study, green synthesis of reduced graphene oxide-Ag (rGO-Ag) nanocomposite was carried out via bioreduction of Ag salt and graphene oxide (GO) using waste dry cell battery rod and Corchorus olitorius extract as GO precursor and reducing agent, respectively. Characterisation of rGO-Ag nanocomposite was achieved by UV/Vis spectroscopy, XRD, SEM, FTIR and BET analyses. Photocatalytic degradation of Janus Green blue (JGB) dye was conducted in batch mode. Effects of irradiation time, photocatalyst composition, temperature and recyclability were investigated. BET surface area of the nanocomposite was 532.914 m2/g with pore size of 2.136 nm. Optimal percentage photo-removal and equilibrium adsorption capacity of JGB dye by the nanocomposite achieved were 95.72% and 120.48 mg/g, respectively. Photocatalytic adsorption process followed more accurately Freundlich model implying multilayer adsorption onto rGO-Ag surface. Adsorption kinetics fitted perfectly into pseudo-second-order model while the enthalpy change is endothermic. The photocatalyst exhibited considerable stability, efficiency and was successfully applied for the removal of JGB in wastewater samples.

Room-Temperature One-Step Synthesis of Silver/Reduced Graphene Oxide Nanocomposites as an Excellent Microwave Absorber.

The present study is focused on room-temperature synthesis carried out by reduction of an aqueous silver nitrate (AgNO3) and AgNO3/graphene oxide (GO) dispersion using a low-cost commercial Fehling B solution in one step to form silver quantum dots (Ag QDs) and their Ag/reduced graphene oxide (Ag/RGO) nanocomposites and their characterization. The crystallinity, surface chemistry, structural, and morphological studies indicated the formation of crystalline small-sized quasispherical-functionalized Ag particles distributed uniformly on the surface of RGO. The conductivity measurements further showed an improvement in the conductivity of Ag/RGO nanocomposites as compared to neat Ag QDs. Our findings showed that Ag/RGO nanocomposites prepared by using 0.055 wt % of GO exhibited a total enhanced electromagnetic interference (EMI)-shielding efficiency (SET) of ∼39.2-42.3 dB (2-8 GHz) with a maximum value of ∼43.8 dB at 7. 5 GHz due to conduction loss, an interconnected conducting network, and a synergistic effect, and it followed an absorption mechanism. Furthermore, this superior absorption-dominated shielding conferred reflection loss (RL) in the range of -79 to -82.5 dB with a RL minima of -88 dB at 7.5 GHz, considering an effective absorption bandwidth of ∼6 GHz with 99.9% absorptivity. It is anticipated that Ag/RGO nanocomposites prepared in one step at room temperature could find potential EMI-shielding applications.

Enhanced Surface-Enhanced Raman Scattering Activity of MoS2–Ag-Reduced Graphene Oxide: Structure-Mediated Excitonic Transition

Enhanced Surface-Enhanced Raman Scattering Activity of MoS₂–Ag-Reduced Graphene Oxide: Structure-Mediated Excitonic Transition

Detection of Imatinib Based on Electrochemical Sensor Constructed Using Biosynthesized Graphene-Silver Nanocomposite.

The establishment of a monitoring technique for imatinib is necessary in clinical and environmental toxicology. Leaf extracts of Lycoris longituba were used as reducing agent for the one-step synthesis of reduced graphene oxide-Ag nanocomposites. This nanocomposite was characterized by TEM, FTIR, XRD, and other instruments. Then, the graphene/Ag nanocomposite was used as a modifier to be cemented on the surface of the glassy carbon electrode. This electrode exhibited excellent electrochemical sensing performance. Under the optimal conditions, the proposed electrode could detect imatinib at 10 nM−0.28 mM with a low limit of detection. This electrochemical sensor also has excellent anti-interference performance and reproducibility.

A novel H2O2photoelectrochemical sensor based on ternary RGO/Ag-TiO2 nanotube arrays nanocomposite

Ternary nanocomposite photoelectrodes composed of Ag nanoparticles, reduced graphene oxide (RGO), and TiO2 nanotube arrays (TNTs) were successfully designed and achieved by a combining technique of cyclic voltammetry and anodic oxidation. Herein, the obtained RGO/Ag-TNTs composites were employed for photoelectrochemical (PEC) monitoring platform of hydrogen peroxide (H2O2) for the first time. Compared to pure TNTs, Ag-TNTs, and RGO-TNTs, the ternary RGO/Ag-TNTs nanocomposites with appropriate loading amount of RGO and Ag show much higher PEC activity, which were contributed to the synergistic effect resulting from the effective incorporation of Ag nanoparticles and RGO onto the TNTs to accelerate the electron transfer, increase the charge carrier density and prolong the electron lifetime demonstrated by electrochemical impedance spectroscopy (EIS), Mott-Schottky (M-S) measurements and open circuit voltage decay (OCVD) measurement. Under the optimal experimental conditions, the as-prepared PEC sensors exhibited an extremely wide dynamic range from 10−7 nM to 10 mM, and in the range of 0.1–10 mM with higher sensitivity and a detection limit of 20 μM. Moreover, the PEC sensors displayed good reproducibility, long-term stability, and selectivity toward the determination of H2O2. These excellent results make the as-developed ternary RGO/Ag-TNTs nanocomposites a promising candidate in PEC detection H2O2.

One-step fabrication of Ag/RGO doped TiO2 nanotubes during anodization process with high photocatalytic performance

Reduced graphene oxide (RGO) and Ag nanoparticles were incorporated simultaneously with two-step anodic TiO2 nanotube through anodization process, and their photocatalytic activity was investigated in the degradation of 2,4-dichlorophenol (2,4-DCP). Furthermore, the optical properties and photocatalytic degradation efficiency were examined as a function of Ag NPs concentration in Ag/RGO–TiO2 nanotube. Morphological characterization showed that Ag NPs and RGO sheets were well-doped inside and outside the TiO2 nanotubes’ walls. Meanwhile, X-ray diffraction and EDX analysis confirmed the existence of both Ag NPs and RGO. The optical investigation revealed that the incorporation of Ag NPs and RGO with TiO2 nanotubes improved the light absorbance and the narrowing of TNT bandgap energy (from 2.85 to 2.35 eV). Therefore, among the various samples, Ag50/RGO–TNTs photocatalyst had the most optimal performance, degrading 96% and 66% of 2,4-DCP under UV and visible light irradiation, respectively. The kinetic study confirmed that degradation reactions over all photocatalysts followed zero-order kinetics. Finally, the recovery test of the optimum sample (Ag50/RGO–TNT) showed 6% reduction following 5-cycle photocatalytic degradation of 2,4-DCP under UV irradiation.

Green synthesis of reduced graphene oxide grafted Ag/ZnO for photocatalytic abatement of methylene blue and antibacterial activities

We have reported a facile, green synthesis of reduced graphene oxide (RGO) grafted Ag/ZnO (RGO-Ag/ZnO) nanocomposite in the presence of L-Methionine (L-Met) for synergetic photocatalytic degradation of methylene blue (MB) and antibacterial activities. L-Met shows an excellent efficiency as stabilizing and reducing agents for the synthesis of both Ag NPs and RGO. The successful synthesis of pure phase L-Met-RGO-Ag/ZnO was confirmed by XRD. According to UV-DRS analysis, the doping of Ag resulted in a decrease bandgap energy of ZnO from 3.34 eV to 3.18 eV. The mixed morphologies of the nanocomposite were studied by SEM and TEM. The photocatalytic degradation efficiency of L-Met-RGO-Ag/ZnO towards MB dye was investigated at varying initial concentrations of MB dye, H2O2, and ultrasonication. The optimum degradation efficiency of the nanocomposite (50 mg) at room temperature (25 °C) was found to be 99% with an initial MB dye concentration of 10 mg/L and 120 min contact time. The fast degradation of MB dye was observed in the presence of H2O2. The ultrasonication of the catalyst vanishes the synergetic interface of the nanocomposite, as a result, poor photocatalytic performance (85%) was observed even at a long period of contact time (210 min). Moreover, RGO-Ag/ZnO nanocomposites have shown strong antibacterial activity against both Gram-positive bacteria (B. Subtilis) and Gram-negative bacteria (E. coli). In conclusion, RGO-Ag/ZnO nanocomposite shows a promising photocatalyst for the degradation of organic dyes and antibacterial activities.

One-Step Eco-Friendly Synthesis of Ag-Reduced Graphene Oxide Nanocomposites for Antibiofilm Application

This study focuses on the synthesis and characterization of Ag nanoparticle-decorated reduced graphene oxide (RGO) nanocomposites (Ag-RGO), which were obtained via a facile, green and efficient one-pot hydrothermal method. TEM results showed that the silver nanoparticles (20-50 nm) were uniformly attached onto RGO sheets with C/O ratio of 6.4 and 80% of sp2 carbon, obtained from XPS analysis. Compared with GO and RGO, the prepared Ag-RGO composites possessed significant antibacterial property; the minimum inhibitory concentration of Ag-RGO was just 31.25 μg/mL against Gram-positive bacteria S. aureus and Gram-negative bacteria E. coli. Particularly, the Ag-RGO nanocomposites released more Ag+ in acidic condition, promoting the produce of reactive oxygen species, which are acknowledged as disruption to the membrane integrity of the bacteria. Moreover, the Ag-RGO nanocomposites effectively dispersed and eliminated the maturely formed biofilm, showing superior advantages in responding to public health threats posed by biofilm-related infections.

Effect of Ag/rGO on the Optical Properties of Plasmon-Modified SnO2 Composite and Its Application in Self-Powered UV Photodetector

A facile hydrothermal method was employed to synthesize silver–reduced graphene oxide (Ag/rGO) plasmon-modified SnO2 composite, by incorporating Ag–reduced graphene oxide (Ag/rGO) into SnO2 nanorods as a photoanode for assembling a self-powered ultraviolet photodetector (UVPD). The as-synthesized samples were investigated in detail by X-ray diffraction (XRD), scanning electron microscopy (SEM), Raman spectroscopy, and UV visible spectrophotometer. The as-prepared Ag/rGO films show enhanced light absorption attributed to the localized surface plasmon resonance (LSPR). The optimized 1.0 wt.% Ag/rGO incorporated into SnO2-based UVPD exhibits a significant photocurrent response due to the enhanced absorption light and effective suppression of charge recombination. This UVPD demonstrates a high performance, with photocurrent density reaching 0.29 mAcm−2 compared to the SnO2-based device with 0.16 mAcm−2. This device also exhibits a high on:off ratio of 195 and fast response time, which are superior to that of the free-modified one. In addition, the UVPD based on plasmon-modified SnO2 photoanode treated with TiCl4-aqueous solution has attained a higher photocurrent with a maximum value reaching 5.4 mAcm−2, making this device favorable in ultraviolet detection.

Fabrication of Reduced Graphene Oxide-Ag Nanocomposites and Analysis on the Interaction with BSA

Graphene is an excellent platform to support and stabilize silver nanoparticles (AgNPs). The reduced graphene oxide-silver nanoparticles (rGO-AgNPs) were synthesized by the chemical reduction method and characterized by using ultraviolet-visible (UV-vis) absorption, transmission electron microscopy (TEM), X-ray diffractometer (XRD), and scanning probe microscopy (SPM). The binding reaction of rGO-AgNPs with bovine serum albumin (BSA) was investigated by using fluorescence spectrometry and SPM. As the concentration of AgNPs increased, the fluorescence spectrum was quenched, and the quenching process of rGO-AgNPs and BSA was static quenching. Thermodynamic parameters of the absorption process were evaluated at different temperatures, and the negative values of Gibbs free energy ( Δ G ) showed that this process was spontaneous. The main type of interaction was hydrophobic interaction according to the values of changes in standard enthalpy ( Δ H ) and entropy ( Δ S ). In addition, the morphology changes of proteins interacting with nanomaterials were detected by SPM.

Biosynthesis of the silver nanoparticles on the graphene oxide’s surface using Pistacia atlantica leaves extract and its antibacterial activity against some human pathogens

In this study, a complete green synthesis method to reduced graphene oxide-Ag nanoparticles hybrid by applying extract of Pistacia atlantica leaves as both stabilizing and reducing agent was reported. P. atlantica leaves extract reduce graphene oxide and adsorbing on the graphene surface. Moreover, the surface adsorbed P. atlantica leaves extract can more in situ reduce Ag ions to Ag nanoparticles and stabilize them. The resultant nanocomposite, i.e. RGO-P. atlantica/Ag, is characterized by UV–Vis spectroscopy, field emission scanning electron microscopy (FE-SEM), wavelength-dispersive X-ray spectroscopy (WDX), X-ray diffraction (XRD), Fourier transform infrared (FT-IR) spectroscopy, transmission electron microscopy (TEM), energy dispersive X-ray spectroscopy (EDS) and inductively coupled plasma (ICP). In addition, antibacterial properties of RGO-P. atlantica/Ag nanocomposite were studied. Agar disk and agar well diffusion are the methods to determined antibacterial properties of synthesized nanocomposite. Also MIC (Minimum Inhibitory Concentration) and MBC (Minimum Bactericidal Concentration) were recognized by macro broth dilution assay.

Green syntheses of silver nanoparticle decorated reduced graphene oxide using l-methionine as a reducing and stabilizing agent for enhanced catalytic hydrogenation of 4-nitrophenol and antibacterial activity.

Herein, we have reported a facile and green synthesis approach of Ag NP decorated reduced graphene oxide (RGO) through an in situ self-assembly method in the presence of l-methionine (l-Met) as reducing and stabilizing agent. The electronic properties, crystal structure, and morphology of the as-synthesized RGO–Ag nanocomposite were investigated by UV-Visible (UV-Vis) spectroscopy, Fourier transform-infrared (FTIR), X-ray diffraction (XRD), field emission scanning electron microscopy (FESEM) and transmission electron microscopy (TEM) techniques. UV-Vis and FTIR show the effective reduction of GO and the formation of Ag NPs using l-Met. FESEM, TEM, and XRD analysis show the successful impregnation of Ag NPs into RGO with a 23 nm average crystallite size. The RGO–Ag nanocomposite with NaBH4 shows a fast-catalytic reduction of 4-nitrophenol (4-NP) to 4-aminophenol (4-AMP). The enhanced catalytic activity of RGO–Ag nanocomposites can be attributed to the synergistic effect of improved adsorption capacity and the absence of agglomeration of Ag nanoparticles. Moreover, RGO–Ag showed strong antibacterial activity against B. subtilis and E. coli.

Performance Analysis of Silver-Based Graphene Nanocomposite Bulk Materials Obtained by Spark Plasma Sintering

Silver-based bulk materials containing Ag/reduced graphene oxide (Ag/rGO) nanocomposite were prepared via a two-step procedure. First, a one-pot procedure was used to form Ag/rGO nanocomposites from AgNO3 and GO using hydrazine as a reductant. Then, Ag/rGO nanocomposites with various graphene contents were mixed with silver nanopowder and consolidated using spark plasma sintering. The hardness of the bulk material increased to 70 HV when the graphene content was increased to 2.5 wt.%. The bulk densification varied from 87.2% to 96% and was highest at graphene content of 2.5 wt.%. The conductivity (43.00–53.73 MS/m) was highest at 0.7 wt.% graphene content. The variation of the intensity and conductivity is mainly related to the formation of Ag-C bonds, while the variation of the density is mainly related to the sintering process.

Green synthesis of reduced graphene oxide-Ag nanoparticles as a dual-responsive colorimetric platform for detection of dopamine and Cu2+

A one pot rapid and green synthesis approach using pine (Pinus densiflora) leaf extracts was developed to prepare AgNPs decorated with graphene nanocomposites (rGO@AgNPs). The rGO@AgNPs was used for an innovative, facile and reliable dual functional assay of dopamine (DA) and copper ions (Cu2+). Synergistic interactions of DA with rGO@AgNPs through π-π interactions and hydrogen bindings could induce aggregation of the rGO@AgNPs and color changing of the solution from yellow to brown. The UV–vis absorption ratio (A515/A405), corresponded to the color changes, was monitored for quantitative determination of DA. The sensor was also utilized to detect Cu2+ through an anti-aggregation mechanism. Cu2+ ions could prevent aggregation of rGO@AgNPs through formation of a complex with DA, and DA acted as a selective chelating agent for Cu2+. In the presence of a certain amount of DA, the aggregation of rGO@AgNPs decreased by increasing the concentration of Cu2+ ions in the solution. It accompanies with a color change from brown to yellow and increasing the absorption ratio of A405/A515. The limit of detection (LOD) for DA and Cu2+ were estimated as 16 and 9.8 nM, respectively. The green synthesized rGO@AgNPs were used for selective detection of DA and Cu2+ in human urine and tomato samples.

Specific ion effect on the surface properties of Ag/reduced graphene oxide nanocomposite and its influence on photocatalytic efficiency towards azo dye degradation

The surface property of a catalyst is influenced by the presence of different inorganic ions as well as pH of the medium. Ag/reduced graphene oxide (Ag/rGO) nanocomposite was synthesized by adopting simple solution chemistry technique using simple ultrasonication process. The influence of the specific anions like Cl−, Br−, NO3−, SO42−, CH3COO− as well as cations like Na+, NH4+, Mg2+ and Ca2+ ions on the surface charge (zeta potential) of the nanocomposite and their effect on the photocatalytic degradation efficiency towards azo dye degradation in aqueous medium was studied. We found that the catalytic property of the nanocomposite is significantly influenced by its surface property which is a function of pH of the medium and the different inorganic ions present in the system.

Effects of reducing agents on the synthesis of Ag/rGO nanocomposites

A facile and rapid microwave-assisted green route has been used for the formation of Ag nanoparticles (AgNPs) and the reduction of graphene oxide (GO) simultaneously with five different reducing agents, sodium hydroxide (NaOH), potassium hydroxide (KOH), sodium citrate, urea and ascorbic acid. The experimental results show that the structural properties and phase of Ag/reduced graphene oxide (Ag/rGO) nanocomposites are connected with reducing agent. AgNPs can be uniformly and compactly anchored on reduced GO (rGO) surface in the microwave field for 2 min by the assist of NaOH or KOH as reducing agent. The OH− can not only accelerate the ionization of acidic functional groups but also act as the nucleophile for Ag+. By addition of sodium citrate and urea, the GO sample remains its original structure, and Ag+ tends to form Ag2CO3, which then decomposes into Ag2O. While in the urea solution, Ag2O turns into [Ag(NH3)2]+ ions with abundant urea, then [Ag(NH3)2]+ ions are reduced to Ag0 by electrons, which leads to both Ag and Ag2O phase coexisting in the urea treated samples. In addition, it can be found that NaOH shows the best results in terms of the crystallinity and purity of Ag grains anchored on rGO surface.