Reduced Graphene Oxide Nanoparticles Research Articles

Reduction of amorphous carbon clusters from the highly disordered and reduced graphene oxide NPs by acoustical shock waves — Towards the formation of highly ordered graphene

The journey of exploring the acoustical shock wave-induced solid state phase transitions on polymorphic and allotropy materials have gained enormous momentum in recent years after the invention of the tabletop Reddy tube, but, the knowledge of shock wave-induced phase transitions on allotropy materials is very limited in comparison to the polymorphic materials. Hence, in this framework, we report the shock wave-induced transitions based on the reduction of the amorphous carbon clusters in the highly disordered and reduced graphene oxide nanoparticles (rGO NPs) [rGO — is also called as modified graphene]. The reduction of the disordered carbon in the rGO NPs under shocked conditions is examined by the techniques such as X-ray diffractometry and Raman spectrometer. X-ray crystallographic studies clearly present that as the shock pulses are increased, the intensity of the (002) peak is increased for which the authentication is observed by the Raman spectral analyses wherein it is clearly indicated the decrement and increment of the D and G bands against the exposure of the shock pulses thereby the ID/IG ratios are found to be 1.24, 1.17, 1 and 0.927 for 0, 100, 200 and 400 shocks, respectively. According to the Raman spectral results, the area of the amorphous Raman peak is reduced against the shock pulses such that the values are 98, 82, 81 and 48 for the 0, 100, 200 and 400 shocks, respectively. The removal of amorphous carbon clusters in the rGO NPs can be explained on the basis of the conversion of sp3 to sp2 hybridizations based on the shock wave induced hot-spot nucleation mechanism.

Label-free electrochemical immunosensor based on staphylococcal protein a and AgNPs-rGO-Nf for sensitive detection of virginiamycin M1

Virginiamycin (VIR), a feed additive, is used to promote pig and poultry growth. However, it is hazardous to human health. This work described a label-free electrochemical immunosensor based on silver nanoparticles-reduced graphene oxide (AgNPs-rGO) nanocomposites and staphylococcal protein A (SPA) for the first time to directly detect the residual marker VIR M1. Good catalytic currents for oxygen reduction reaction were apparently obtained after the modification of nanocomposites on gold electrode. Nanocomposites were characterized using UV–Vis, X-ray diffraction (XRD) patterns, Fourier transform infrared spectroscopy (FTIR) and transmission electron microscopy (TEM). SPA was targeted to immobilize VIR M1 monoclonal antibody (mAb) by binding to Fc region of antibody. The proposed immunosensor showed a wide linear range from 0.25 ng mL−1 to 100 ng mL−1, providing detection limit (LOD) of 0.18 ng mL−1 of VIR M1. Recovery rates ranged from 92.27% to 98.84%, and relative standard deviation (RSD) was not above 6.6%, indicating the immunosensor could detect VIR M1 in actual samples with high accuracy. The sensor showed good selectivity, reproducibility and stability and could be considered as a potential tool for detection of VIR M1 in feed and animal derived food.

Preparation of Polyindole-MnO2/Reduced Graphene Oxide-based Ternary Composite System for Supercapacitive Application

ABSTRACT A polyindole-MnO2 (PIn-MnO2)/reduced graphene oxide (RGO)-based ternary composite system has been assembled by an in-situ polymerization. In this system, the concentration of RGO has been varied by the interval of 0.25 wt.% in fixed quantity of PIn-MnO2 system. The mean crystallite size of RGO was observed to be 6.64 nm calculated by using Debye–Scherrer formula. This study demonstrates the dispersion of RGO nanoparticles in PIn-MnO2 system to optimize the supercapacitive properties. As expected, the supercapacitive properties of PIn-MnO2-RGO composites were influenced by the addition of RGO nanoparticles and it is optimized for 0.5 wt.% of RGO concentration. The 0.5 wt.% RGO-loaded PIn-MnO2-RGO composite shows specific capacitance of the order 1750 Fg−1 at a scan rate of 50 mV s−1. The main accomplishment of present work is that the 0.5 wt.% RGO-loaded composite shows long-term stability, which is capacitance retention up to 6000 cycles. Similarly, galvanostatic charge/discharge curves of 0.5 wt.% RGO-loaded composite show long and nearly symmetric behavior, which is suitable for range of practical applications.

Biosynthesis of Reduced graphene oxide nanoparticles from Uropathogenic K.oxytoca

With advantages over physical and chemical methods from an economic and environmental standpoint, bioproduction possibilities for nanoparticles are becoming a very important topic. The current study's objective is to synthesis of reduced graphene oxide nanoparticles from Klebsiella oxytoca that cause urinary tract infections and characterized the synthesized biogenic nanoparticles by different method for characterization include Fourier transform infrared, energy dispersive spectroscopy, and scanning electron microscopy.
 CONCLUSIONS 
 The isolated K.oxytoca from urinary tract infections have the ability to biosynthesized of reduced graphene oxide nanoparticles with size range from 35-85 nm and average diameter was 49.31 , the EDS determine the elemental analysis of rGO that contained carbon, oxygen, nitrogen, phosphate, and chloride and many active group detected by FTIR technique .

Highly stable ammonium ion-selective electrodes based on one-pot synthesized gold nanoparticle-reduced graphene oxide as ion-to-electron transducers

An effective transducer for all-solid-state ion-selective electrodes (SC-ISEs) was developed based on gold nanoparticle-reduced graphene oxide (AuNP-rGO) hybrid material. The AuNP-rGO composite was synthesized via a simple, eco-friendly, and one-pot method with sodium citrate as the reducing agent and the stabilizer. The nanocomposite was deposited on the GC substrate via the drop-casting method and then covered with an ammonium ion-selective membrane (NH4+-ISM) to form the potentiometric electrode. The AuNP-rGO layer possessed a large surface area, high capacitance, and good hydrophobicity; thereby effectively enhancing the potential stability of the electrode without the formation of an aqueous layer. The electrode also exhibited a rapid potential response (<10 s) to NH4+ ions, an excellent Nernstian response with a slope of 56.94 (±1.57) mV/decade, a detection range of 10-5 − 10-2 M, and a detection limit of 3.80 × 10-6 M. The proposed electrode also exhibited outstanding properties including insensitivity to interferences (light, oxygen, carbon dioxide, and redox species), good reproducibility, and long operating life. The electrode has been successfully applied for NH4+ detection in real water samples, which makes it a promising alternative for developing effective and robust SC-ISEs.

Photocatalytic Activity of Nanocomposites Based on Titania Nanorods and Nanotubes Doped with Ag and Reduced Graphene Oxide Nanoparticles

Photocatalytic Activity of Nanocomposites Based on Titania Nanorods and Nanotubes Doped with Ag and Reduced Graphene Oxide Nanoparticles

Simultaneously improved electrical and mechanical performance of hot-extruded bulk scale aluminum-graphene wires

Aluminum-based alloys are highly sought after as lightweight alternatives in electric grid applications. Improving the electrical conductivity of aluminum alloys has the potential to increase the energy efficiency of power transport. The hot extrusion process was used to synthesize AA1100 alloy with low-cost reduced graphene oxide nanoparticles to manufacture ultra-conductive aluminum composites in this study. The effects of graphene content on the electrical and mechanical performance of the composites were evaluated. The macroscale AA1100/graphene wires demonstrated a 2.1% enhancement in electrical conductivity at 20 °C, while the ultimate tensile strength increased by 6.1%. A Zener-Hollomon model was used to confirm the in-process exfoliation of the agglomerated graphene nanoparticle feedstock into high electrical conductivity graphene-like flakes during extrusion. The graphene-like flakes may have provided high-velocity carrier pathways leading to the enhanced electrical performance of the alloy. Transmission electron microscopy at aluminum-graphene interfaces ensures the preclusion of detrimental carbide formation during composite synthesis while confirming the structure of graphene-like flakes. The in-process exfoliation provides an economically viable technique to produce bulk scale “graphinated” aluminum composites for advanced applications and this can also be applied more generally to other alloy systems.

Hollow mesoporous organosilica nanoparticles reduced graphene oxide based nanosystem for multimodal image-guided photothermal/photodynamic/chemo combinational therapy triggered by near-infrared.

Developing a nanosystem that can perform multimodal imaging-guided combination therapy is highly desirable but challenging. In this study, we introduced multifunctional nanoparticles (NPs) consisting of graphene oxide-grafted hollow mesoporous organosilica loaded with the drug doxorubicin (DOX) and photosensitizers tetraphenylporphyrin (TPP). These NPs were encapsulated by thermosensitive liposomes that release their contents once the temperature exceeds a certain threshold. Metal oxide NPs grown on the graphene oxide (GO) surface served multiple roles, including enhancing photothermal efficiency, acting as contrast agents to improve magnetic resonance imaging, increasing the sensitivity and specificity of photoacoustic imaging, and catalysing hydrogen peroxide for the generation of reactive oxygen species (ROS). When locally injected, the HMONs-rNGO@Fe3 O4 /MnOx@FA/DOX/TPP NPs effectively enriched in subcutaneous Hela cell tumour of mice. The photothermal/photodynamic/chemo combination therapy triggered by near-infrared (NIR) successfully suppressed the tumour without noticeable side effects. This study presented a unique approach to develop multimodal imaging-guided combination therapy for cancer.

Experimental investigations on thermal diffusivity of heterogeneous materials

The paper presents alternative methods for determining thermal diffusivity of heterogeneous materials. In the study the thermal regular regime method and the step-heating technique were applied to measure the thermal diffusivity of graphene oxide/rubber composites characterized by different kinds of basic matrix and different weight concentrations of the reduced graphene oxide nanoparticles. Thermal diffusivity plays a relevant role in the analysis of transient heat transfer processes. It is an essential material property which may be a measure of the quality of different kinds of engineering materials. Therefore, the knowledge of thermal diffusivity is important, especially for what heterogeneous materials (composites) concerns. In the present study composites with three kinds of matrix - have been studied: FKM- fluoroelastomer, NBR- acrylonitrile butadiene rubber and HNBR- hydrogenated acrylonitrile butadiene rubber. The reduced graphene oxide rGO in the form of crumpled flakes was used as filler in order to significantly influence the thermophysical properties of the composites. In the two tested experimental methods, - thermal regular regime method and step-heating technique, relatively large material samples were used. Hence, the influence of the material heterogeneity on the investigation results immaterial. The obtained results, both from thermal regular regime method and step-heating technique, show an increase of the thermal diffusivity with increasing the graphene oxide content in the composite. An uncertainty analysis of the results of applied research methods has been carried out, as well as measurements of the heat capacity of the matrix of two composites using differential scanning calorimetry to validate the thermal diffusivity results from the values of thermal conductivity and density.

Analytical possibilities of determining aristolochic acid I using amperometric biosensors and polarizing fluorescent immunoanalysis

Tyrosinase amperometric biosensors based on graphite printed electrodes modified with reduced graphene oxide (RGO), multi-walled carbon nanotubes (MWNTs), and a nanocomposite based on RGO and silver nanoparticles (Ag NPs), as well as a variant of polarization fluorescence immunoanalysis (PFIA) using a tracer based on fluorescein-5(6)-carboxamidohexanoic acid for determining aristolochic acid Ⅰ (AA) were developed. It has been found that AA Ⅰ is a tyrosinase inhibitor in the concentration range of 1×10–10–1×10–8 M, with LOD of 7×10–11 M. Modifying the electrode surface by RGO and MWCNTs improved the analytical characteristics of the biosensor; analyzed concentration range increased to 1×10–11–1×10–6 M for RGO and 1×10–10–1×10–6 M for MWCNTs. The correlation coefficient and LOD were 0.9828 and 8×10–12 M, and 0.9859 and 5×10–11 M in the case of the biosensors modified with RGO and MWCNT, respectively. A variant of a competitive polarization fluorescent immunoanalysis was developed, which permitted determining AA Ⅰ in the concentration range of 1×10–11–1×10–7 M with LOD of 7×10–12 M. The concentration of antibodies was 1 mg/ml, the time of incubation of the immune complex tracer-antibody was 5 min. Methods for determining AA Ⅰ were tested using samples of herbal preparations, in roots, leaves, stems of European hoof, as well as in crops grown together with hoof.

SnO2 Nanoparticle-Reduced Graphene Oxide Hybrids for Highly Selective and Sensitive NO2 Sensors Fabricated Using a Component Combinatorial Approach

SnO₂ Nanoparticle-Reduced Graphene Oxide Hybrids for Highly Selective and Sensitive NO₂ Sensors Fabricated Using a Component Combinatorial Approach

CuxPd1-xO nanoparticle-reduced graphene oxide nanocomposite catalyzed direct ortho-C–H acylation of 2-aryl pyridines

We report the application of CuxPd1-xO nanoparticle-reduced graphene oxide nanocomposites as efficient catalysts for direct CH bond activation using alcohols as carbonyl sources. The composition of the CuxPd1-xO nanoparticles plays a vital role in determining their catalytic activity because of a composition-dependent synergistic effect. We show that the catalysts can be reused for successive 5 cycles without obviously losing their catalytic activity. Our catalysts offer considerable advantages over previous metallic alloy nanoparticles not only due to their catalytic performance but also for the ease of their synthesis and catalytic robustness.

Lignin nanoparticles-reduced graphene oxide based hydrogel: A novel strategy for environmental applications

In this work, facile fabrication of lignin nanoparticles (LNP)-based three-dimensional reduced graphene oxide hydrogel (rGO@LNP) has been demonstrated as a novel strategy for environmental applications. Herein, LNP were facilely synthesized from walnut shell waste through a direct chemical route. These LNP were incorporated into the continuous porous network of rGO network to fabricate rGO@LNP hydrogel. Characterization studies were carried out using various analytical techniques viz. scanning electron microscopy, Fourier transform IR spectroscopy, X-ray diffraction and thermogravimetric analysis. The efficiency of rGO@LNP hydrogel as adsorptive platform was evaluated by employing methylene blue and Pb2+ as model pollutants, whilst the effect of various experimental parameters was ascertained for optimal performance. Furthermore, Agar well diffusion method was used to check the antibacterial activities of the hydrogel using two bacterial pathogenic strains, i.e. Klebsiella pneumoniae (gram negative) and Enterococcus faecalis (gram positive). Results showed that after the inclusion of LNP into rGO hydrogel, there was a marked improvement in pollutant's uptake ability and compared to bare LNP and rGO, the composite hydrogel showed enhanced bactericidal effect. Overall, this approach is outstanding because of the synergy of functional properties of nano-lignin and rGO due to multi-interaction sites in the resulting hydrogel. The results presented herein support the application of rGO@LNP as innovative water filter material for scavenging broad spectrum pollutants and bactericidal properties.

Optimizing the thermophysical properties and combustion performance of biodiesel by graphite and reduced graphene oxide nanoparticle fuel additive

In this study, 50 and 75 ppm reduced graphene oxide and graphite nanoparticle additives were added to cottonseed oil methyl ester which was obtained by the trasterification method. The effects of the related nanoparticle additives on fuel properties such as viscosity, lower heating value, density and cetane number were determined, and their effects on engine performance and exhaust emissions were experimentally investigated. The superior properties of reduced graphene oxide such as superior conductivity, high reactivity and large surface area to engine performance and emissions were experimentally investigated and presented the in this paper. The results indicated that, brake thermal efficiency increased in NPs additive added fuels by 6.92 % in CGt-50, 11.89 % in CGt-75, 14.35 % in CGn-50 and 17.97 % in CGn-75 fuels, respectively compared to C0 fuel at full load. Brake specific fuel consumptions decreased by 6.92 %, 11.25 %, 13.36 and 16.28 %, respectively. At 8 Nm load, the cylinder pressures of nanoparticle added fuels increased between 1.91 % and 5.16 % compared to base fuel. It was concluded that the heat release rate increased with the increase of the NPs additive ratio. Between the rate of 2 %-5.09 % reducing were obtained in ID, 0.84 %-5.85 % in CD for CGt-75 and CGn75 fuels according to C0 fuel. Compared to C0 fuel, CO emissions decreased by 9.48 %, 11.85 %, 14.23 % and 14.99 %, consecutively, in CGt-50, CGt-75, CGn-50 and CGn-75 fuels at full load. Thanks to the nanoparticle additive, the thermophysical properties and heat transfer rate of the fuels improved and the fuel mixture was stabilized, leading to an improvement of 8.98 %, 11.79 %, 14.04 % and 15.73 % in HC emissions, respectively. The NPs additive increased the cylinder temperature by 10.59 %-17.72 %, which enhanced NOx emissions. It was also observed that smoke emissions were reduced by 8.57 %-18.09 %.

Ionic liquid modified chloroperoxidase is immobilized on gold nanoparticles-reduced graphene oxide nanocomposites for efficient sensoring of nitrite by electroenzymatic catalysis

Electroenzymatic biosensors have wide applications due to its fastness and sensitivity. Here we propose a bio-nanocomposite to be dropped on glassy carbon electrode (GCE) for nitrite sensoring by electroenzymatic catalysis. The composite is constructed by ionic liquids (1-butyl-3-methylimidazolium bromide, ILBMB) modified chloroperoxidase (CPO) immobilized on gold nanoparticles (Au NPs) modified reduced graphene oxide (rGO). The ILBMB can facilitate the direct electron transfer (DET) of CPO on GCE without a redox mediator. The molecular docking indicates ILBMB is located at the opening of substrate channel rather than occupy the active site of CPO, which is beneficial to its DET. Circular dichroic spectrum (CD) verifies the α-helix content of CPO is increased, and ultraviolet-visible spectrum (UV–vis) demonstrates the heme prosthetic group become more exposed by ILBMB. These changes result in the enhancement of CPO activity. The rGO-Au NPs plays two roles enhancing the detection signal and improving the loading of CPO on GCE. The sensor (CPO-ILBMB/rGO-Au NPs/GCE) provides two models for nitrite detection as cyclic voltammetry and amperometry. The detection limit is 0.25 μmol·L−1 and 0.049 μmol·L−1, respectively with corresponding detection range of 2.0−2500 μmol·L−1 and 0.5–300 μmol·L−1. The high sensitivity, stability, and selectivity of this electroenzymatic biosensor ensure its potential practical application.

Bioinspired synthesis of hematite nanoparticles-reduced graphene oxide composite for application in bisphenol a detection: A new in-sight

Bisphenol A (BPA), one of the well-known environmental endocrine-disrupting compounds, has an effective estrogenic activity that badly impacts the environment and human health. Therefore, an urgent need arises to develop a simple and effective method for BPA detection. Herein, we report novel, disposable and flexible nanoplatforms for electrochemical determination of BPA using carbon cloth electrode supported hematite nanoparticles (α-Fe2O3NPs) on reduced graphene oxide (rGO) composite. The α-Fe2O3NPs@rGO composite was synthesized through a green route using leaves extract of Cinnamomum tamala that acted as a reducing and stabilizing agent for α-Fe2O3NPs followed by the addition of graphene oxide to convert it into rGO. The nanoplatform was fabricated using the electrophoretic deposition technique on carbon cloth (CC) substrate, i.e., (α-Fe2O3NPs@rGO/CC). The analytical performance of α-Fe2O3NPs@rGO/CC nanoplatform is ascribed to the synergistic effect of α-Fe2O3NPs and rGO that resulted in a larger active surface to volume ratio, superior conductivity, and enhanced electrochemical behavior. The fabricated α-Fe2O3NPs@rGO/CC nanoplatform exhibited a broad linear range from 1.9 × 10−10 to 1.00 μM having a higher sensitivity of 33.04 μA (log μM)−1 cm−2 and a low limit of detection of 0.23 μM. It also displayed excellent selectivity, repeatability, reproducibility, and stability with satisfying results. Moreover, the electrochemical nanoplatform helped analyze the real samples to detect BPA with acceptable results. Hence, this nanoplatform could be further utilized to detect other estrogenic analytes.

POROUS SILICON NANOSYSTEMS FOR ETHANOL SENSOR

Sensory elements based on hybrid films containing porous silicon and reduced graphene oxide nanostructures have been created. A decrease in electrical resistance and an increase in the capacitance of sensor elements in the AC mode due to the adsorption of ethanol molecules have been registered. To assess the sensory properties of hybrid films, the concentration dependences of the adsorption ability in the 0–4.5% range were determined and the dynamic characteristics of ethanol sensors based on them were studied. It was found that sensor films with different ratios of porous silicon and reduced graphene oxide nanoparticles have the maximum sensitivity to ethanol in different concentration ranges. The functional properties of hybrid films can be controlled by changing the proportions of their components. The reaction time of sensory elements to changes in the concentration of ethanol molecules is 40–50 s. The obtained results expand the perspective of the application of nanosystems based on porous silicon in sensor devices.

Photokilling of waterborne-resistant pathogenic bacteria using cobalt-doped zinc oxide doped on reduced graphene oxide nanoparticles

This study is aimed at the chemical synthesis of light-activated cobalt-doped zinc oxide and its further doping on reduced graphene oxide (RGO) and assessment of its antibacterial activity on antibiotic-resistant waterborne pathogens including Enterococcus faecalis, Staphylococcus aureus, Klebsiella pneumonia, and Pseudomonas aeruginosa. The synthesized nanoparticles were characterized via UV–vis spectroscopy, scanning electron microscopy (SEM), and energy-dispersive X-ray spectroscopy (EDS). The minimal inhibitory concentration (MIC) of nanoparticles portrayed a significant killing of both Gram-positive and Gram-negative bacteria. The synthesized nanoparticles were further found as active killers of bacteria in drinking water. Further, these nanoparticles were found photothermally active alongside ROS generators. The photokilling activity makes them ideal replacement candidates for traditional water filters.

Development of an ultrasensitive molecularly imprinted poly-(ortho-phenylenediamine) based sensor for the determination of melamine adulteration in milk and infant formula.

A sensitive molecularly imprinted poly‐(ortho‐phenylenediamine) electrochemical sensor was fabricated for selective melamine detection in milk and infant formula. The pencil graphite electrode (PGE) was modified by deposition of Au nanoparticles and reduced graphene oxide (RGO) on its surface. The fabrication of the electrode in various stages was monitored using cyclic voltammetry. The immobilized RGO, MIP, and gold nanoparticles on the PGE surface were morphologically characterized by field‐emission scanning electron microscopy (FESEM). Under the optimized conditions, the linear range and the limit of detection (LOD) were 10–17–10–8 M and 2.64 × 10–16 M (S/N = 3), respectively. The prepared sensor exhibited a good reproducibility and repeatability response. The recovery range of melamine‐spiked milk and infant formula was 92.7%–103.9% and 93.5%–105.8%, respectively. The sensor could apply successfully for melamine determination in milk and infant formula samples.

Plasmon-induced broad spectrum photocatalytic overall water splitting: Through non-noble bimetal nanoparticles hybrid with reduced graphene oxide

Semiconductor-based photocatalysts have a narrow absorption range of sunlight and low light utilization efficiency, due to the limitation of band gap of semiconductor materials. Using pure metal as plasmonic photocatalyst, completely different from traditional semiconductor photocatalyst system. The resonance effect between the free electrons and photons on the metal surface runs through the whole light region. Herein, our study provides a non-noble plasmonic Cu6Sn5 bimetal nanoparticles-reduced graphene oxide (rGO) composite with broad spectrum absorption to obtain excellent performance for photocatalytic overall water splitting. The proposed design is able to efficiently produce the electron-hole pair by plasmonic Cu6Sn5 bimetal, further injected in the rGO. The Cu6Sn5 and rGO structure provides photocatalytic sites, which is saturated with charge efficiently initiate overall water splitting. Taken together, our studies provide an important insight in the field of non-noble and non-semiconductor plasmonic photocatalyst.