Graphene Ag Nanoparticles Research Articles

Flexural strength, biocompatibility, and antimicrobial activity of a polymethyl methacrylate denture resin enhanced with graphene and silver nanoparticles.

The study evaluates the effect of adding graphene-Ag nanoparticles (G-AgNp) to a PMMA auto-polymerizing resin, with focus on antibacterial activity, cytotoxicity, monomer release, and mechanical properties. Auto-polymerizing acrylic resin (M) was loaded with 1 wt% G-AgNp (P1) and 2 wt% G-AgNp (P2). Methyl methacrylate monomer release (MMA) was measured after immersion of the samples in chloroform and cell medium respectively. Cell viability was assessed on dysplastic oral keratinocytes (DOK) and dental pulp stem cells. Oxidative stress and inflammatory response following exposure of dysplastic oral keratinocytes to the experimental resins was evaluated. Antibacterial activity against Staphylococcus aureus, Streptococcus mutans and Escherichia coli and also flexural strength of the resins were assessed. Residual monomer: For samples immersed in chloroform, MMA concentration reached high levels, 10.27 μg/g for sample P1; MMA increased at higher G-AgNp loading; 0.63 μg/g MMA was found in medium for P1, and less for sample P2. Cell viability: Both cell lines displayed a viability decrease, but remained above 75%, compared to controls, when exposed to undiluted samples. Inflammation: proinflammatory molecule TNF-α decreased when DOK cultures were exposed to G-AgNp samples. MDA levels indicated increased oxidative stress damage in cells treated with PMMA, confirmed by the antioxidant mechanism activation, while samples containing G-AgNp induced an antioxidant effect. All tested samples showed antibacterial properties against Gram-positive bacteria. Samples containing G-AgNp also exhibited bactericide action on E. coli. Mechanical properties: both samples containing G-AgNp improved flexural strength compared to the sample resin, measured through elastic strength parameters. PMMA resin loaded with G-AgNp presents promising antibacterial activity associated with minimal toxicity to human cells, in vitro, as well as improved flexural properties. These encouraging results obtained in vitro support further in vivo investigation, to thoroughly check whether the PMMA loaded with graphene-silver nanoparticles constitute an improvement over current denture materials.

A three-dimensional Ag nanoparticle/graphene hydrogel composite and its application as an improved supercapacitor’s electrode

In this work, pure graphene hydrogel (GH) and graphene/Ag nanoparticle (GH-AgNP) composite hydrogels with various wt% of 0.01, 0.1, 1, 10, 30, and 50% Ag were produced. Samples were characterized by XRD, Raman spectroscopy, and SEM analysis. Supercapacitor electrodes based on pure GH and GH-AgNP composite hydrogel were fabricated without the use of any additives and adhesives, and their electrochemical behaviors were investigated by cyclic voltammetry (CV), galvanostatic charge/discharge (GCD), and electrical impedance spectroscopy (EIS). High specific capacitances of 252 F/g and 180 at scan speeds of 10 and 200 mV/s for pure hydrogel and specific capacitances of 260 to 143 F/g for composite hydrogels were observed, respectively. GCD analyses implied that GH-AgNP composites possessed lower internal resistance (IR), therefore better rate capabilities. Consequently, it seems that the optimization of GH-AgNP composite hydrogels is an effective way of reducing the supercapacitor’s internal resistance and thereby increasing the power and improving supercapacitor performance. It was observed that the addition of Ag nanoparticles to graphene hydrogels, even with low wt%, significantly reduces the charge transfer resistance. In a GH-AgNP sample with an Ag/GO ratio of 1%, the charge transfer resistance value was reduced by 77%, while the specific capacitance was reduced by just 8%.

Enhanced Efficiency of Dye-Sensitized Solar Cells Benefited from Graphene Modified by Ag Nanoparticles.

In this paper, graphene modified by Ag nanoparticles was successfully applied into dye sensitized solar cells. The morphologies and compositions of graphene and graphene-Ag nanoparticles were characterized by scanning electron microscope and energy dispersive X-ray spectroscopy. The optical and electrical properties were evaluated by UV-vis-NIR absorption spectroscopy, electrochemical impedance spectroscopy and current-voltage curve. The results indicated that the incorporation of graphene or graphene-Ag nanoparticles can improve the light absorption and decrease the charge recombination. The solar cells with graphene-Ag nanoparticles exhibited short-circuit current density of 14.34 mA cm-2, open-circuit voltage of 709 mV and conversion efficiency of 6.01%, which were higher than those of DSSCs with graphene or pure TiO2.

Three-dimensional electrochemical DNA biosensor based on 3D graphene-Ag nanoparticles for sensitive detection of CYFRA21-1 in non-small cell lung cancer

Abstract Many studies have confirmed that CYFRA21-1 DNA is a sensitive and specific marker for non-small cell lung cancer (NSCLC). Hence, there is an urgent need to explore new strategies for early diagnosis of CYFRA21-1 DNA in the clinic. Here, we report a three-dimensional electrochemical DNA biosensor based on 3D graphene functionalized with Ag nanoparticles for sensitive DNA detection. The highly conductive nanocomposite layer was characterized by using scanning and transmission electron microscopy, contact angle analysis, and cyclic voltammetry. The 3D GF/AgNPs provide a favorable microenvironment to retain the bioactivity of immobilized probe ssDNA and effectively promote electron transfer owing to their excellent biocompatibility and good conductivity. Under optimal conditions, the biosensor could detect target DNA down to 1.0 × 10−14 M with high sensitivity, and the peak currents were linear with the logarithm of the concentrations of target DNA from 1.0 × 10−14 to 1.0 × 10−7 M. Furthermore, in clinical trials, the three-dimensional biosensing system detected CYFRA21-1 DNA in real lung cancer samples with satisfactory results. Our research suggests that this newly developed 3D electrochemical biosensor is a promising method for potential use in the early diagnosis of lung cancer patients.

Preparation of graphene-Ag nanoparticles hybrids and their SERS activities

Surface-enhanced Raman scattering (SERS) substrates based on graphene and Ag nanoparticles hybrid structures with low cost, high uniformity were prepared by a standard process of immobilization of silver nanoparticles with 3-aminopropyltrimethoxysilane (APTMS). Thermal annealing was used for removing residual APTMS and adjusting the morphology of silver nanoparticles, and the effectiveness of this method was verified experimentally. The influence of annealing temperature, dipping duration, and APTMS volume on the distribution of Ag nanoparticles and Raman enhancement was investigated experimentally and analyzed in detail. Our samples were prepared under the preparation conditions of 10% ν/ν APTMS, dipping time of 48h, annealing temperature of 450°C, duration of 30min, and Ar flow rate of 40sccm. SERS activities with enhancement of 107 and relative standard deviation of <20% were observed using rhodamine 6G (R6G) as probe molecule with a concentration of 10−6M and 10−7M.

Fabrication and Characterization of Graphene-Ag Nanoparticles Composites

Graphene-Ag nanoparticles composites were prepared by one step in situ synthesis method,using nontoxic green glucose as reducer.Graphite oxide and ammoniacal silver ions were reduced at the same time without stabilizing agent under mild reaction conditions of aqueous solution.X-ray diffraction(XRD),Fourier transform infrared spectroscopy(FT-IR),Raman spectroscope,scanning electronic microscope(SEM),and transmission electronic electron microscope(TEM) were used to characterize the resulting composites.The results of analysis indicate that graphite oxide and ammoniacal silver ions are reduced by glucose simultaneously.Ag nanoparticles(AgNPs) uniformly distribute in the graphene sheets,and most of AgNPs show twin boundary.The quantity of silver nitrate influences the size and range of sizes of the AgNPs.The range of sizes of AgNPs on the graphene sheets centralizes at 25 nm under a suitable concentration of silver ions.The intensities of the Raman signals of graphene in the composites increase 7 fold by the loaded AgNPs.