rGO-Ag Nanocomposite Research Articles

In Situ Synthesis, Characterization and Photocatalytic Efficacy of Silver-Enhanced MXene and Graphene Nanocomposites

The emergence of 2D materials has significantly expanded the wide range of nanomaterials with diverse applications. Notably, their high conductivity, catalytic efficiency, and hydrophobicity have fueled heightened research interests for water treatment applications. This research aimed to investigate the synthesis and characterization of MXene and reduced graphene oxide (rGO) nanocomposites with silver nanoparticles (Ag) for enhanced catalytic activity in the decomposition of Direct Blue-24 dye. In this study, we employed well-established methods, previously documented in the literature, to prepare two distinct nanocomposites. Novel nanocomposites, namely reduced graphene oxide–silver nanoparticles (rGO–Ag) and MXene–silver nanoparticles (MXene–Ag), were synthesized using the hydrothermal and direct reduction method with an ammoniacal solution (aqueous solution). Comprehensive characterization using advanced tools revealed that the introduced Ag particles integrated seamlessly onto the parent nanofilms of the Carbon derivatives, forming a secondary phase with enhanced catalytic functionality. These nanocomposites demonstrated significant improvements in the catalytic decomposition reactions in simulated wastewater. Verification involved the reduction reaction of Direct Blue-24 dye at known nanocomposite concentrations. The results indicated that MXene–Ag exhibited a superior catalytic activity of 98% in 10 min compared to the rGO–Ag nanocomposite films, which achieved 96% in 35 min. The results indicated that MXene–Ag nanocomposites exhibited a 20–25% increase in catalytic efficiency compared to the rGO–Ag nanocomposites. The outcomes of this research hold promise for practical applications in textile wastewater management and various industrial sectors dealing with mutagenic and carcinogenic chemicals containing azo and/or phthalocyanine products.

Green Synthesis of Silver Nanoparticle Decorated on Reduced Graphene Oxide Nanocomposite using Clinacanthus nutans and Its Applications

A straightforward approach that uses Clinacanthus nutans leaf extract as a bio-reduction agent has been reported to anchor silver nanoparticles onto graphene oxide (rGO-Ag). The nanocomposite was characterized by using ultraviolet-visible spectroscopy, Fourier transform infrared spectroscopy, field emission scanning electron microscopy with energy-dispersive X-ray spectroscopy, and X-ray diffraction. A qualitative colour transition from yellowish to dark brown confirmed the biosynthesis of rGO-Ag nanocomposite and showed a surface plasmon resonance at 263 nm and 425 nm. Utilizing cyclic voltammetry, the electrochemical characteristics of the rGO-Ag nanocomposite modified screen printed carbon electrodes were examined. The rGO-Ag nanocomposite electrode enhanced anodic current approximately 1.29 times greater compared to silver nanoparticles (AgNPs) and 1.34 times greater compared to graphene oxide (GO). Moreover, rGO-Ag nanocomposites exhibited excellent antibacterial activity against typical Gram-positive (S. aureus) (11.99 ± 0.26 mm) and Gram-negative (E. coli) (11.86 ± 0.29 mm) bacteria. Toxicity was assayed using brine shrimp Artemia salina. The results of hatching and mortality assay demonstrates that AgNPs and rGO-Ag nanocomposite is biocompatible with A. salina at a low dosage (0.001 mg/mL). This work offers a guide for the future synthesis of nanocomposites using green reductants. The as- synthesized nanocomposite shows a promising component for the development of biomedical devices applications.

Effect of Ionic Liquid Anions in Tunning the Morphology and Size of Ag in rGO-Ag Nanocomposites: Anticancer Activity of the Composites Against A549 Lung Cancer Cells

Effect of Ionic Liquid Anions in Tunning the Morphology and Size of Ag in rGO-Ag Nanocomposites: Anticancer Activity of the Composites Against A549 Lung Cancer Cells

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.

GREEN SYNTHESIS OF REDUCED GRAPHENE OXIDE SILVER NANOCOMPOSITE USING Anisomeles malabarica (L.) R. BR. LEAF EXTRACT AND ITS ANTIBACTERIAL ACTIVITY

The development of new antimicrobial materials has arisen in response to the need to prevent and control the growth of pathogenic microorganisms without the use of antibiotics. The Silver (Ag) nanoparticles attached r-GO (rGO/Ag) nanocomposite was synthesised in the present work using a one-pot in-situ chemical reduction approach and studied for antibacterial property. We developed a rapid preparation of graphene from graphite using modified Hummers method and reduced by A. malabarica leaf extract. UV-Vis spectroscopy and FT-IR were used to characterize the synthesized GO and rGO–Ag nanocomposite. The antibacterial properties of the synthesized GO and rGo-Ag nanocomposite were evaluated against human pathogenic organisms like Escherichia coli, Pseudomonas aeruginosa, Klebsiella pneumoniae and Staphylococcus aureus using agar well diffusion method. At 50µl concentrations, synthesised GO inhibited Pseudomonas aeruginosa (19 mm) and rGO-Ag nanocomposite inhibited Staphylococcusaureus (28 mm).Antibacterial properties of the nanocomposites were found to be efficient against both gram positive and gram negative bacteria. Thus, green synthesized RGO-supported Silver nanoparticles play an important role in the medical disciplines.

Antibacterial and Antibiofouling Activities of Antimicrobial Peptide-Functionalized Graphene-Silver Nanocomposites for the Inhibition and Disruption of Staphylococcus aureus Biofilms.

Owing to the emergence of antibiotic-resistant strains, bacterial infection and biofilm formation are growing concerns in healthcare management. Herein, we report an eco-benign strategy for the synthesis and functionalization of graphene-silver (rGOAg) nanocomposites with an antimicrobial peptide (AMP) for the treatment of Staphylococcus aureus infection. The synthesis of rGOAg nanocomposites was carried out by simple microwave reduction, and the as-synthesized rGOAg was covalently functionalized with an AMP. As a natural AMP, poly-l-lysine (PLL) functionalization of rGOAg enhanced the antibacterial efficacy and target specificity against the S. aureus biofilm. The robust bactericidal efficiency and biofilm disruption by AMP-functionalized rGOAg (designated as GAAP) occurred through the "contact-kill-release" mode of action, where the electrostatic interaction with bacterial cells together with intracellular ROS generation induced physical disruption to the cell membrane. The internalization of GAAP into the cytoplasm through the damaged cell membrane caused an outburst of intracellular proteins and DNA. Crystal violet staining along with fluorescence and confocal microscopic images showed an effective inhibition and disruption of the S. aureus biofilm upon treatment with GAAP. PLL functionalization also prevented the dissolution of Ag+ ions and thereby minimized the in vitro toxicity of GAAP to the 3 T6 fibroblast and human red blood cells. The ex vivo rat skin disinfection model further demonstrated the potency of GAAP in eliminating the biofilm formation and disruption of the S. aureus biofilm. The obtained results demonstrated a general approach for designing a functional nanocomposite material to disrupt the mature biofilm and provided a promising strategy for treating bacterial infection.

Graphene oxide–silver nanocomposite SERS substrate for sensitive detection of nitro explosives

Here, we carried out the sensing of nitro amine explosives through surface-enhanced Raman scattering (SERS) employing silver nanoparticle (Ag NP)-decorated reduced graphene oxide (rGO) nanocomposite substrate. In situ reduction process has been utilized to prepare the reduced graphene oxide–silver nanocomposite. The areal distribution and structural properties of Ag NPs have been studied. The fabricated nanocomposite was characterized using microscopic, spectroscopic and thermogravimetric methods. Moreover, the electrochemical properties of rGO–Ag nanocomposites were analysed using electrochemical methods. Raman spectra show the enhancement in the Raman signal of rGO-decorated Ag NPs with an intensity enhancement factor of 12.5 for D peak and 9 for G peak. The Ag NP-enriched rGO has also demonstrated strong SERS activity towards the detection of cyclotetramethylene tetranitramine and cyclotrimethylenetrinitramine up to 10−12 M as the limit of detection with SERS enhancement of 109. Thus, the synthesized nanocomposite shows potential applications for sensing of explosives.

One-pot hydrothermal-synthesized rGO-Ag nanocomposite as a sensing platform for detection and quantification of methylene blue organic dye and tricyclazole pesticide

In this work, we established a simple and cost-effective method of dispersing silver nanoparticles on the surface GO nanosheets using a one-pot hydrothermal process with the presence of polyvinylpyrrolidone (PVP) as both surfactant and reducing agent. The systematic effects of synthesis conditions on the microstructure and formation of silver nanoparticles on the surface of rGO nanosheets were studied. Notably, the high-crystalline silver nanoparticles with a size of 15 nm were uniformly dispersed on the surface of rGO nanosheets when synthesis conditions were optimized at hydrothermal temperature 160 °C, pH = 9 and 10 mM of silver nitrate precursor. Our analysis results indicate that the as-prepared rGO-Ag nanocomposites exhibit the highest SERS efficiency and good sensitivity with methylene blue organic dye and tricyclazole pesticide. These can be explained by the electron interactions between silver nanoparticles and graphene oxide, which makes unique material advantages for the highly effective detection of pollutant molecules in the environmental monitoring applications.

The effect of Ag loading on supercapacitor performance of graphene based nanocomposites

In the present study, we prepared reduced graphene oxide (rGO) decorated with Ag nanoparticles by a one pot, simultaneous reduction method. The effect of AgNO3 amount on the chemical, morphological and electrochemical properties of binary rGO-Ag nanocomposite for supercapacitor application was investigated. The chemical and morphological characterization of prepared rGO-Ag nanocomposites was realized with field emission scanning electron microscopy (FE-SEM), transmission electron microscopy (TEM), ultraviolet-visible spectroscopy (UV-Vis), X-ray diffraction (XRD) and Fourier transform infrared spectroscopy (FTIR). For supercapacitor application, electrochemical performance of the nanocomposites was investigated with cyclic voltammetry (CV), galvanostatic charge-discharge (GCD) and electrochemical impedance spectroscopy (EIS) techniques. As a result of their excellent conductivity and spacer role which prevent aggregation of rGO nanosheets and maintain the electroactive surface area, Ag nanoparticles significantly enhance the electrochemical performance of the nanocomposite. The rGO-Ag nanoparticle nanocomposite exhibited a maximum specific capacitance of 34.2 mF cm−2 at 0.6 A cm−2 current density. The nanocomposite electrode also has excellent rate capability and cycle life. The capacitance retention of rGO-Ag electrode is 98% after 1000 charge-discharge cycle. The results showed that rGO-Ag nanocomposite is a building block for ternary or other multicomponent nanocomposites.

Silver-doped graphene oxide nanocomposite triggers cytotoxicity and apoptosis in human hepatic normal and carcinoma cells.

IntroductionGraphene oxide nanoparticles have been widely used in industry and biomedical fields due to their unique physicochemical properties. However, comparative cytotoxicity of silver-doped reduced graphene oxide (rGO–Ag) nanoparticles on normal and cancerous liver cells has not been well studied yet.Materials and methodsThis study aimed at determining the toxic potential of rGO–Ag nanocomposite on human liver normal (CHANG) and cancer (HepG2) cells. The rGO–Ag nanocomposite was characterized by using different advanced instruments, namely, dynamic light scattering, scanning electron microscope, and transmission electron microscope.ResultsThe rGO–Ag nanocomposite reduced cell viability and impaired cell membrane integrity of CHANG and HepG2 cells in a dose-dependent manner. Additionally, it induced reactive oxygen species generation and reduced mitochondrial membrane potential in both cells in a dose-dependent manner. Moreover, the activity of oxidative enzymes such as lipid peroxide, superoxide dismutase, and catalase were increased and glutathione was reduced in both cells exposed to rGO–Ag nanocomposite. Pretreatment with N-acetylcysteine inhibited cytotoxicity and reactive oxygen species generation in CHANG and HepG2 cells exposed to rGO–Ag nanocomposite (50 µg/mL). DNA damage was determined by Comet assay and maximum DNA damage occurred at rGO–Ag nanocomposite (25 µg/mL) for 24 h. It is also valuable to inform that HepG2 cells appear to be slightly more susceptible to rGO–Ag nanocomposite exposure than CHANG cells.ConclusionThis result provides a basic comparative toxic effect of rGO–Ag nanocomposite on hepatic normal and cancerous liver cells.

Electrochemical detection of L-dopa using crude Polyphenol oxidase enzyme immobilized on electrochemically reduced RGO-Ag nanocomposite modified graphite electrode

In the present work, we report the selective and sensitive electrochemical detection of L-dopa using crude Polyphenol oxidase enzyme (PPO) immobilized on electrochemically reduced graphene oxide–silver nanoparticles (RGO-Ag) nano composite modified graphite (Gr) electrode. The Gr electrode is first modified through the electrochemical reduction of graphene oxide - silver (GO-Ag) nano composite to RGO-Ag nano composite on graphite electrode. The crude extract of PPO from Manilkara Zapota (sapota) fruit is later immobilized onto Gr/RGO-Ag modified electrode. Modification of Gr electrode at each step is confirmed by cyclic voltammetry (CV) and Electrochemical impedance (EIS) techniques. The surface characterization of modified electrode is performed by Scanning electron microscopy (SEM). The developed sensor exhibited excellent electrocatalytic activity towards the detection of L-dopa in the concentration range of 1–150 µM with low detection limit and high sensitivity. Further, the practical applicability of the developed biosensor is examined for the detection of L-dopa in urine samples.

Graphene Oxide-Silver Nanocomposite Enhances Cytotoxic and Apoptotic Potential of Salinomycin in Human Ovarian Cancer Stem Cells (OvCSCs): A Novel Approach for Cancer Therapy.

The use of graphene to target and eliminate cancer stem cells (CSCs) is an alternative approach to conventional chemotherapy. We show the biomolecule-mediated synthesis of reduced graphene oxide–silver nanoparticle nanocomposites (rGO–Ag) using R-phycoerythrin (RPE); the resulting RPE–rGO–Ag was evaluated in human ovarian cancer cells and ovarian cancer stem cells (OvCSCs). The synthesized RPE–rGO–Ag nanocomposite (referred to as rGO–Ag) was characterized using various analytical techniques. rGO–Ag showed significant toxicity towards both ovarian cancer cells and OvCSCs. After 3 weeks of incubating OvCSCs with rGO–Ag, the number of A2780 and ALDH+CD133+ colonies was significantly reduced. rGO–Ag was toxic to OvCSCs and reduced cell viability by mediating the generation of reactive oxygen species, leakage of lactate dehydrogenase, reduced mitochondrial membrane potential, and enhanced expression of apoptotic genes, leading to mitochondrial dysfunction and possibly triggering apoptosis. rGO–Ag showed significant cytotoxic potential towards highly tumorigenic ALDH+CD133+ cells. The combination of rGO–Ag and salinomycin induced 5-fold higher levels of apoptosis than each treatment alone. A combination of rGO–Ag and salinomycin at very low concentrations may be suitable for selectively killing OvCSCs and sensitizing tumor cells. rGO–Ag may be a novel nano-therapeutic molecule for specific targeting of highly tumorigenic ALDH+CD133+ cells and eliminating CSCs. This study highlights the potential for targeted therapy of tumor-initiating cells.

Enhanced sunlight photocatalytic activity of silver nanoparticles decorated on reduced graphene oxide sheet

A facile and straightforward method has been developed to synthesize silver nanoparticles decorated on reduced graphene oxide (RGO) nanosheets through hydrothermal reaction. The composite was characterized by XRD, UV-Visible spectroscopy, SEM and TEM techniques. In this synthesized RGO-Ag nanocomposite, the Ag nanoparticles size ranges 30-50 nm. Moreover, the RGO-Ag composites exhibited excellent photocatalytic activity towards the degradation of methylene blue (MB) in presence of sunlight. This photocatalytic reaction is completed within 20 min and the rate of reaction depends on the amount of RGO present in the nanocomposites.

Microwave synthesis of reduced graphene oxide decorated with silver nanoparticles for electrochemical determination of 4-nitrophenol

A facile microwave-assisted synthesis of a reduced graphene oxide-silver (rGO-Ag) nanocomposite and its application towards the electrochemical determination of 4-nitrophenol (4-NP) are reported. The nanocomposite was characterized using UV–visible spectroscopy, X-ray diffraction (XRD), transmission electron microscopy (TEM), Raman, and X-ray photoelectron spectroscopy (XPS). The formation of spherical AgNPs was confirmed from the single surface plasmon absorption feature and the TEM analysis. The reduction of GO was conveniently monitored using D and G band intensity ratio (ID/IG) of Raman spectrum and XPS analysis. A glassy carbon electrode (GCE) was modified with the rGO-Ag nanocomposite and used for the electrocatalytic reduction and determination of 4-NP. The nanocomposite modified electrode displayed a higher reversible redox peak currents and lower charge transfer resistance (Rct) towards [Fe(CN)6]3−/4− couple compared other controlled electrodes. The amperometric i-t curve response to 4-NP at a working potential of −0.52V (vs. Ag/AgCl) covers the 1–1100μM concentration range, and the limit of detection is 0.32μM. The sensor is selective for 4-NP even in the presence of 50-fold higher concentrations of analogues such as bromophenol blue, 2-amino-4-nitrophenol, 2-chlorophenol and 2,4-dinitrophenol. The nanocomposite modified GCE was successfully applied for the determination of 4-NP in spiked real water samples where it gave recoveries between 94.3% and 100.2% at a concentration level of 10–50μM.

Hydrothermal preparation of reduced graphene oxide-silver nanocomposite using Plectranthus amboinicus leaf extract and its electrochemical performance.

Graphene based nanocomposites are receiving increasing attention in many fields such as material chemistry, environmental science and pharmaceutical science. In this study, a facial synthesis of a reduced graphene oxide-silver nanocomposite (RGO-Ag) was carried out from Plectranthus amboinicus leaf extract. The synthesized nanocomposite was characterized by using X-ray diffraction, scanning electron microscope, Fourier transform infrared spectroscopy, X-ray photoelectron spectroscopy, transmission electron microscope and UV-vis spectroscopy for structural confirmation. The reduction of graphene oxide and silver ions was achieved simultaneously due to the reducibility of the Plectranthus amboinicus leaf extract. We further investigated the electrochemical properties of the biosynthesized RGO-Ag nanocomposite. A nonenzymatic H2O2 electrochemical sensor was shown to be successfully fabricated by using biosynthesized RGO-Ag nanocomposite. Moreover, the fabricated electrochemical sensor also showed good selectivity.

Controlled synthesis of reduced graphene oxide supported silver nanoparticles for selective and sensitive electrochemical detection of 4-nitrophenol

An electrochemical sensing platform made of a reduced graphene oxide-silver (rGO-Ag) nanocomposite was developed for the detection of 4-nitrophenol. The synthesis of the nanocomposite was monitored at different reaction times (2h, 6h, 10h and 15h) in modified Tollens’ test and characterized using UV-visible absorption spectrum, transmission electron microscopy (TEM), X-ray diffraction (XRD), and Raman spectroscopy analyses. Completely spherical Ag nanoparticles (NPs) were found at a reaction time of 15h with an average particle size of 16nm. The nanocomposites prepared with different reaction times were used for the electrocatalytic reduction of 4-NP, and the rGO-Ag (15h) nanocomposite-modified glassy carbon (GC) electrode displayed a higher faradaic current at an overpotential of −0.5V toward 4-NP reduction. The rGO-Ag (15h) nanocomposite-modified electrode was used for the square wave voltammetric (SWV) detection of 4-NP in a 0.1M phosphate buffer (pH 7.2), and it showed a good sensitivity toward 4-NP detection even for a nanomolar concentration. The nanocomposite exhibited multi-linear ranges and 4-NP detection limit was found to be 1.2nM. The present sensor was stable and selective to 4-NP in the presence of its structural analogues such as 2-nitrophenol (2-NP), 2-aminophenol (2-AP), 3-aminophenol (3-AP), 4-aminophenol (4-AP), and 2,4-dichlorophenol (2,4-DCP). The rGO-Ag nanocomposite could be successfully applied for the determination of 4-NP in real water samples, and good recoveries were found.

Electrochemical properties of silver nanoparticle-supported reduced graphene oxide in nitric oxide oxidation and detection

Influence of different concentrations of ascorbic acid in the formation of rGO–Ag nanocomposites using an in situ synthesis method, and the electrocatalytic oxidation and in situ detection of NO were studied.

Reduced graphene oxide-silver nanoparticle nanocomposite: a potential anticancer nanotherapy.

BackgroundGraphene and graphene-based nanocomposites are used in various research areas including sensing, energy storage, and catalysis. The mechanical, thermal, electrical, and biological properties render graphene-based nanocomposites of metallic nanoparticles useful for several biomedical applications. Epithelial ovarian carcinoma is the fifth most deadly cancer in women; most tumors initially respond to chemotherapy, but eventually acquire chemoresistance. Consequently, the development of novel molecules for cancer therapy is essential. This study was designed to develop a simple, non-toxic, environmentally friendly method for the synthesis of reduced graphene oxide–silver (rGO–Ag) nanoparticle nanocomposites using Tilia amurensis plant extracts as reducing and stabilizing agents. The anticancer properties of rGO–Ag were evaluated in ovarian cancer cells.MethodsThe synthesized rGO–Ag nanocomposite was characterized using various analytical techniques. The anticancer properties of the rGO–Ag nanocomposite were evaluated using a series of assays such as cell viability, lactate dehydrogenase leakage, reactive oxygen species generation, cellular levels of malonaldehyde and glutathione, caspase-3 activity, and DNA fragmentation in ovarian cancer cells (A2780).ResultsAgNPs with an average size of 20 nm were uniformly dispersed on graphene sheets. The data obtained from the biochemical assays indicate that the rGO–Ag nanocomposite significantly inhibited cell viability in A2780 ovarian cancer cells and increased lactate dehydrogenase leakage, reactive oxygen species generation, caspase-3 activity, and DNA fragmentation compared with other tested nanomaterials such as graphene oxide, rGO, and AgNPs.ConclusionT. amurensis plant extract-mediated rGO–Ag nanocomposites could facilitate the large-scale production of graphene-based nanocomposites; rGO–Ag showed a significant inhibiting effect on cell viability compared to graphene oxide, rGO, and silver nanoparticles. The nanocomposites could be effective non-toxic therapeutic agents for the treatment of both cancer and cancer stem cells.

Rapid microwave-assisted synthesis of silver decorated-reduced graphene oxide nanoparticles with enhanced photocatalytic activity under visible light

A facile, fast, and scalable microwave irradiation (MWI) method for the synthesis of Ag nanoparticles (Ag NPs) dispersed on graphene sheets has been developed. The reduction of graphene oxide takes place in ethanol solution within 2min of MWI without any additional reducing agent or complicated treatment. The morphology and microstructure of the as-prepared hybrid were characterized by Scanning electron microscopy (SEM) and Transmission electron microscopy (TEM) images. The result showed the Ag NPs with an average size of 5–10nm decorated on the rGO sheets. X-ray powder diffraction (XRD) determined that the crystallographic structure of Ag is face-centered cubic and there was a strong interaction between Ag NPs and rGO sheets. Fourier transform infrared spectroscopy (FTIR) and X-ray photoelectron spectroscopy (XPS) showed that GO had been reduced to rGO in our hybrid. Moreover, visible photocatalytic activity of the rGO–Ag nanocomposites was tested using Rhodamine B (RhB) as the model contaminant. This result indicates that rGO–Ag nanocomposites display distinctly enhanced photocatalytic activities. The investigation gave a promise to the development of original yet highly efficient graphene-based photocatalysts that utilize visible light as an energy source.