Nanoparticle-decorated Reduced Graphene Oxide Research Articles

Hollow porous gold nanoparticle/reduced graphene oxide composite films for electrochemical supercapacitor applications

Here, we report the synthesis of hollow porous gold nanoparticles-decorated reduced graphene oxide (HPAuNPs/RGO) nanocomposites and their electrochemical performances as active electrode material for supercapacitors. Accordingly, the HPAuNPs were first prepared using a simple solution phase template method according to the modified literature procedure, and the size control of hollow porous gold particles was achieved by varying the concentration of hydroquinone used as the reducing agent. Then, the surface of the RGO nanosheets was decorated with HPAuNPs through the self-assembly approach. The structural and morphological features of synthesized nanoparticles and nanocomposites were evaluated by spectroscopic and morphologic methods. Also, the electrochemical supercapacitive performances of the HPAuNPs/RGO/GC nanocomposite electrodes as both cathode and anode materials were analyzed in Na2SO4 solution using electrochemical methods. As a control sample, the RGO/GC electrode was also examined under identical experimental conditions. The results indicate that the composite materials display higher specific capacitances (107–325 F/g) compared with bare RGO (55 and 37 F/g) at a potential scan rate of 20 mV/s. Furthermore, it is obtained that the specific capacitances of the composite electrodes based on hollow porous gold nanoparticles are larger than those of previously reported supercapacitors with spherical gold nanoparticles/graphene as electrode materials. The improved electrochemical properties of the HPAuNPs/RGO/GC nanocomposite electrodes can be ascribed to the hollow and porous structure of the gold particles on RGO sheets.

Cobalt oxide nanoparticle-decorated reduced graphene oxide (Co3O4–rGO): active and sustainable nanoelectrodes for water oxidation reaction

Herein, cobalt oxide (Co3O4)-decorated reduced graphene oxide (rGO)-based nanoelectrodes were fabricated by the chemical reduction method for electrocatalytic water oxidation reactions.

MnFe2O4 decorated reduced graphene oxide heterostructures: Nanophotocatalyst for methylene blue dye degradation

The photocatalytic degradation of methylene blue dye (MB) has been investigated using bare manganese ferrite (MnFe2O4) nanoparticles and MnFe2O4 nanoparticles-decorated reduced graphene oxide heterostructures (MnFe2O4/rGO) under ultra-violet irradiation. The MnFe2O4 nanoparticles prepared using a facile co-precipitation method showed single-phase cubic spinel structure and superparamagnetic property. The MnFe2O4/rGO heterostructures showed the formation of sphere-like MnFe2O4 nanoparticles well-attached on rGO nanosheets with reduced agglomeration. The photocatalysis study shows that MnFe2O4/rGO had higher photocatalytic activity compared to bare MnFe2O4 nanoparticles. MB degraded by 84% in presence of MnFe2O4 after UV irradiation of 290 min, while 97% of it degraded in merely 60 min in case of MnFe2O4/rGO heterostructures. This is further confirmed by the well-fitted Langmuir-Hinshelwood Kinetics equation. This improvement in the photocatalytic activity of the heterostructure is attributed mainly to the retardation of the recombination process of photo-generated charge carriers. Hydroxyl radicals play the crucial role in the MnFe2O4-graphene system for MB photodegradation. Thus, MnFe2O4 nanoparticles-decorated reduced graphene oxide heterostructures can act as potential photocatalyst for degradation of hazardous organic dyes present in water.

Magnetic-Assisted Cell Alignment within a Magnetic Nanoparticle-Decorated Reduced Graphene Oxide/Collagen 3D Nanocomposite Hydrogel.

Hydrogel scaffolds are particularly interesting for applications in tissue engineering because of their ability to create a favorable environment which mimics in vivo conditions. However, the hierarchically ordered anisotropic structure which is found in many native tissues and cellular components is hard to achieve in 3D scaffolds. In this work, we report the incorporation of magnetic nanoparticle-decorated reduced graphene oxide (m-rGO) within a collagen hydrogel. This magneto-responsive m-rGO aligned within the collagen hydrogel during gelation with the application of a low external magnetic field. This nanocomposite hydrogel with magnetically aligned m-rGO flakes is capable of encapsulating neuroblastoma cells (SH-SY5Y), promoting cell differentiation and inducing oriented cell growth owing to its excellent biocompatibility and electrical conductivity. The directionally oriented and differentiated SH-SY5Y cells within the m-rGO collagen hydrogel showed propagation of calcium signal along the direction of orientation. This method can be applied to creating magnetically responsive materials with potential for various biomedical applications.

Temperature control synthesis of platinum nanoparticle-decorated reduced graphene oxide of different functionalities for anode-catalytic oxidation of methanol

Platinum (Pt) nanoparticles of varying average diameters decorated on exfoliated reduced graphene oxide (Pt/rGO) of various functionalities have been synthesized by monitoring the temperature of co-reduction of PtIV and GO. The as-synthesized composites are characterized by X-ray diffraction, spectroscopic, thermo gravimetric and microscopic studies. The excellent catalytic capability of the composites for methanol oxidation reaction (MOR) is found to be synergistic in reference to single components, Pt and rGO and might be used in high efficient, less emissive, cost-effective direct methanol fuel cell operated in alkali. The poison tolerance capability of the electrodes as measured by the ratio of forward and backward peak currents due to MOR is found to be relatively high in respect to similar data in the literature and increases with the increase of defect concentration as evaluated from Raman spectroscopic study, on rising the temperature of synthesis of the catalyst. The forward peak current density of the electrode made with Pt/rGO composite synthesized at 40 °C is greater by 5.6 and 287 times than these for pure Pt and rGO based electrodes. The electrode exhibits the best catalytic activity due to presence of the lowest but sufficient defect sites, especially for formation of sp2-C-OH groups on the rGO surface in the vicinity of the poisoned Pt-surface and lowest average diameter (7.41 nm) of dispersed Pt nanoparticles.

A flexible and highly pressure-sensitive PDMS sponge based on silver nanoparticles decorated reduced graphene oxide composite

Flexible pressure sensors have a wide range of applications in wearable electronics and human-machine interfacing. A flexible and highly pressure-sensitive sensor was fabricated with silver nanoparticles (Ag NPs) decorated-reduced graphene oxide composites (Ag/rGO) filling into the PDMS sponge. The Ag/rGO composites were synthesized by one-step chemical reduction method that Ag NPs were tightly and uniformly coated on the surface of reduced graphene oxide nanosheets. Then Ag/rGO composites filled PDMS sponge (Ag/rGO-PDMS) was prepared through a dip-drying method as pressure sensitive materials. The Ag NPs coated on the surface of graphene nanosheets improved the conductivity of the Ag/rGO composites and reduced the contact resistance of graphene nanosheets. The graphene nanosheets could enhance the flexible stability and facilitate the electron transport in Ag/rGO-PDMS. The Ag/rGO-PDMS sponge with optimized GO to Ag weight ratio showed maximum pressure sensitivity of 8.86 kPa−1 which enhanced twenty-two times compared with that of pure rGO filled PDMS sponge (0.40 kPa−1). The flexible Ag/rGO-PDMS sponge with high pressure sensitivity could be used for detection of different kinds of mechanical forces (pressing, bending and twisting) and radial artery blood pulses in real-time.

Electrochemical fabrication of Ni or Ni(OH)2@Ni nanoparticle-decorated reduced graphene oxide for supercapacitor applications

Electrochemical-reduced graphene oxide (ERGO) nanocomposites decorated with Ni or Ni(OH)2@Ni nanoparticles (NPs) were fabricated directly on Au electrodes by one-pot electrochemical approach. This facile, rapid, scalable, and green approach is based on the simultaneous co-reduction of GO and Ni2+ ions at ambient conditions from an aqueous solution without using specific reducing and any other protective agents. The as-prepared NiNP/ERGO could be easily converted into Ni(OH)2@NiNP/ERGO by electrochemical cycling in alkaline solutions. Characterization with field-emission scanning electron microscopy, transmission electron spectroscopy, X-ray diffraction, X-ray photoelectron spectroscopy, and Raman spectroscopy illustrated that the GO were successfully reduced into wrinkled and scrambled ERGO structures and decorated homogenously by very stable and well-separated NiNPs. The electrochemical performances of the as-prepared NiNP/ERGO and the activated Ni(OH)2@NiNP/ERGO electrodes were evaluated via cyclic voltammetry, galvanostatic charge/discharge, and electrochemical impedance spectroscopy. The as-prepared NiNP/ERGO electrodes exhibited a high specific capacity of 293 C g−1 at 4 A g−1. After cycling for 500 times, the surface of NiNPs on ERGO were converted into Ni(OH)2@NiNP/ERGO with a superior specific capacity of 785 C g−1 at 4 A g−1. A maximum capacity of 948 C g−1 was obtained at 4 A g−1 after 1500 cycles, and excellent cycling stability with 92% capacitiy retention was observed after more than 2000 additional cycles. The electrochemical performance of NiNP/ERGO and Ni(OH)2@NiNP/ERGO nanocomposites renders them as potential electrodes in supercapacitors. The present one-pot electrochemical strategy could also be used in the decoration of GO by other metal and metal hydroxides.

Responses to comments on “Ni nanoparticle-decorated reduced graphene oxide for non-enzymatic glucose sensing: An experimental and modeling study [Electrochim. Acta 240 (2017) 388–398

In our recent work [Electrochim. Acta 240 (2017) 388–398], we examined the adsorption energy of glucose on graphene via Ni nanoparticles. In the present study, we have responded to comments to clarify the intricacies of dispersion effect and adsorption energies in our previous work. We have explored the performance and accuracy of some established and promising theoretical schemes, namely, the two-, three- (DFT-D2/3), and many-body (MBD@rSC) dispersion approaches, to account properly for the dispersive force contributions, which were not previously included in the system. Incorporating dispersive forces drastically increased the adsorption energy of glucose (Eads), where different active sites were obtained. The calculated energies were in the order Eads(DFT−D2) < Eads(DFT−D3) < Eads(MBD@rSC). However, because the accuracy of the preferred MBD@rSC method is closely related to the mesh-grid, it is too early to conclude which theoretical approach gives the most satisfactory results. The dependence of the glucose active site and adsorption energy was sensitive to the used theoretical approximation. Therefore, the accuracy of the selected theoretical method should be always tested or compared with the experimental data.

Comments on “Ni nanoparticle-decorated reduced graphene oxide for non-enzymatic glucose sensing: An experimental and modeling study [Electrochim. Acta 240 (2017) 388–398

We stress that the extraordinarily large adsorption energy and the large charge transfer to the adsorbate for the glucose adsorption structure of Ref. [1] are the results of adsorption of a C6H1O6 molecule rather than the adsorption of a glucose molecule. We report the glucose adsorption structure, the effect of Ni clusters on the adsorption energy of glucose, and the charge distribution for the glucose/Ni13/Gr system.

Highly Sensitive Electrochemical Sensor for Anticancer Drug by a Zirconia Nanoparticle-Decorated Reduced Graphene Oxide Nanocomposite.

Because of their large surface area and conductivity, some inorganic materials have emerged as good candidates for the trace-level detection of pharmaceutical drugs. In the present work, we demonstrate the detection of an anticancer drug (regorafenib, REG) by using an electrochemical sensor based on a nanocomposite material. We synthesized a zirconia-nanoparticle-decorated reduced graphene oxide composite (ZrO2/rGO) using a one-pot hydrothermal method. Reduction of the graphene oxide supports of the Zr2+ ions with hydrazine hydrate helped in preventing the agglomeration of the zirconia nanoparticles and in obtaining an excellent electrocatalytic response of the nanostructure ZrO2/rGO-based electrochemical sensor. Structural and morphological characterization of the nanostructure ZrO2/rGO was performed using various analytical methods. A novel regorafenib (REG) electrochemical sensor was fabricated by immobilizing the as-prepared nanostructure ZrO2/rGO on to a glassy carbon electrode (GCE). The resulting ZrO2/rGO/GCE could be used for the rapid and selective determination of REG in the presence of ascorbic acid and uric acid. The ZrO2/rGO/GCE showed a linear response for the REG analysis in the dynamic range 11–343 nM, with a remarkable lower detection limit and limit of quantifications of 17 and 59 nM, respectively. The newly developed sensor was used for the accurate determination of REG in both serum samples and pharmaceutical formulations, with satisfactory results.

Reduced Graphene Oxide-Zirconium Dioxide-Thionine Nanocomposite Integrating Recognition, Amplification, and Signaling for an Electrochemical Assay of Protein Kinase Activity and Inhibitor Screening.

Protein kinase activity analysis is essential and important for elucidation of many fundamental biological processes, disease diagnosis, and drug discovery. Herein, a novel electrochemical biosensing method for protein kinase (PKA) activity was demonstrated by the use of a reduced graphene oxide-zirconium dioxide-thionine (rGO-ZrO2-Thi) nanocomposite, which interestingly served as an integral phosphopeptide-recognizing, signal amplifying and reporting platform. The ZrO2 nanoparticle-decorated reduced graphene oxide (rGO-ZrO2) was first prepared by a hydrothermal reaction route, and then the thionine was conjugated onto the rGO surface via π-π stacking as an excellent electrochemical probe. The prepared rGO-ZrO2-Thi nanocomposites were well-characterized by various techniques. With the full advantage of specific recognition of ZrO2 nanoparticles for the phosphate group, signal amplification, and transduction of abundant thionines onto the rGO surface, and excellent conductivity of rGO, the rGO-ZrO2-Thi nanocomposite endowed a label-free and one-step electrochemical analysis of kemptide phosphorylation catalyzed by PKA. The detection limit for PKA activity was experimentally achieved as 0.005 U/mL, which was evidently lower than most of the reported methods. The proposed sensing strategy could be also applied for an efficient inhibitor evaluation. Therefore, it offered an excellent pathway for a generic and sensitive electrochemical assay of PKA activity and inhibitor.

Pt Nanoparticle-Decorated Reduced Graphene Oxide Hydrogel for High-Performance Strain Sensor: Tailoring Piezoresistive Property by Controlled Microstructure of Hydrogel

A class of conducting reduced graphene oxide hydrogels is prepared with various porosities, surface areas, and electrical conductivities using ethylenediamine (EDA)/functionalized graphene oxide (GO) and ascorbic acid (VC)/GO by hydrothermal method. The microstructure of hydrogels is tailored by changing the composition of materials. It is observed that the conducing network is formed by cross-linked graphene platelets, and the piezoresistive behavior of hydrogels under cyclic compressive strain shows a linear trend up to 6.8% strain when the hydrogel is prepared by adding 5 wt % of EDA in aqueous GO solution. In addition, platinum nanoparticle-decorated (Pt NP-decorated) EDA-GO hydrogel was also prepared, showing greatly improved linear strain range as high as 52.8% with an increase in compressive modulus by 873% because of the multiscale reinforcing mechanism, which is attributed to the strong interaction between Pt NPs and graphene platelets. The piezoresistivity of the hydrogels can be of great intere...

One-pot green synthesis of Ag nanoparticle-decorated reduced graphene oxide composites: effect of Ag/graphene oxide volume ratio and its demonstration as low-voltage on-chip photodetector

We present one-pot synthesis of silver nanoparticle-decorated reduced graphene oxide (AgNP-rGO) composite by utilizing ascorbic acid as a green reduction agent. The effect of volume ratio between Ag(NH3)2OH complex solution and GO solution was studied. High content of Ag volume seems to slower down the reduction of GO, hence providing high nucleation sites for the Ag ions to be reduced to nanoparticles with much higher density. Meanwhile, due to high reduction rate of GO at low content of Ag volume, it produces less density of nanoparticles with larger particle size. The composite was successfully demonstrated as a low-voltage on-chip photodetector. The presence of high-density AgNPs on rGO results to fast response (393 nA/s) and recovery rate (399 nA/s) with excellent cyclic stability even at low biasing voltage of 1 [V] due to the effective localized plasmon resonance of AgNPs. The detectivity and responsivity remarkably increase with the densities of AgNPs and the biasing voltages, where these values can increase from 3.58 × 105 cm Hz1/2 W−1 and 2.2 × 10−6 A/W at 1 [V] up to 2.12 × 108 cm Hz1/2 W−1 and 3.8 × 10−2 A/W at 20 [V], respectively, for the sample with Ag volume of 75%.

PdAg-decorated three-dimensional reduced graphene oxide-multi-walled carbon nanotube hierarchical nanostructures for high-performance hydrogen peroxide sensing

Abstract

Gold nanoparticle-decorated reduced-graphene oxide targeting anti hepatitis B virus core antigen

Hepatitis B virus core antigen (HBcAg) is the major structural protein of hepatitis B virus (HBV). The presence of anti-HBcAg antibody in a blood serum indicates that a person has been exposed to HBV. This study demonstrated that the immobilization of HBcAg onto the gold nanoparticles-decorated reduced graphene oxide (rGO-en-AuNPs) nanocomposite could be used as an antigen-functionalized surface to sense the presence of anti-HBcAg. The modified rGO-en-AuNPs/HBcAg was then allowed to undergo impedimetric detection of anti-HBcAg with anti-estradiol antibody and bovine serum albumin as the interferences. Upon successful detection of anti-HBcAg in spiked buffer samples, impedimetric detection of the antibody was then further carried out in spiked human serum samples. The electrochemical response showed a linear relationship between electron transfer resistance and the concentration of anti-HBcAg ranging from 3.91ngmL−1 to 125.00ngmL−1 with lowest limit of detection (LOD) of 3.80ngmL−1 at 3σm−1. This established method exhibits potential as a fast and convenient way to detect anti-HBcAg.

Palladium nanoparticle-decorated reduced graphene oxide sheets synthesized using Ficus carica fruit extract: A catalyst for Suzuki cross-coupling reactions.

We present a biogenic method for the synthesis of palladium nanoparticle (PdNP)-modified by reducing graphene oxide sheets (rGO) in a one-pot strategy using Ficus carica fruit juice as the reducing agent. The synthesized material was well characterized by morphological and structural analyses, including, Ultraviolet-Visible spectroscopy (UV-Vis), X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FT-IR) and Transmission Electron Microscopy (TEM) and Raman spectroscopy. The results revealed that the PdNP modified GO are spherical in shape and estimated to be a dimension of ~0.16 nm. The PdNP/graphene exhibits a great catalytic activity in Suzuki cross-coupling reactions for the synthesis of biaryl compounds with various substrates under both aqueous and aerobic conditions. The catalyst can be recovered easily and is suitable for repeated use because it retains its original catalytic activity. The PdNP/rGO catalyst synthesized by an eco-friendly protocol was used for the Suzuki coupling reactions. The method offers a mild and effective substitute to the existing methods and may significantly contribute to green chemistry.

Magnetite Nanoparticle Decorated Reduced Graphene Oxide Composite as an Efficient and Recoverable Adsorbent for the Removal of Cesium and Strontium Ions

Magnetite nanoparticles (Fe3O4) decorated reduced graphene oxide (rGO) composite was synthesized by the solvothermal method and utilized as a potential adsorbent for the removal of cesium (Cs+) and strontium (Sr2+) ions from aqueous solution. The effects of adsorbate concentration and reaction time on the removal efficiencies of Cs+ and Sr2+ were investigated. The adsorption capacity increases as the initial concentration of Cs+/Sr2+ increased from 1 to 170 mg/L, which might be due to the more available adsorption sites, and the adsorbent reached equilibrium at 360 min. The adsorption isotherm was fitted to the Freundlich model with maximum adsorption capacities of Cs+ and Sr2+ being 128.2 and 384.6 mg g–1, respectively. The kinetic study showed that the adsorption behavior followed pseudo-second-order kinetics. The rGO/Fe3O4 nanocomposite showed excellent selectivity toward Cs+ and Sr2+ even in the presence of competitive cations (Na+, K+, and Mg2+) having a higher concentration.

Determination of 8-hydroxy-2′-deoxyguanosine oxidative stress biomarker using dysprosium oxide nanoparticles@reduced graphene oxide

Electrochemical detection of 8-OHdG biomarker using Dy2O3@RGO/SPCE.

Ultrasensitive and Selective Organic FET-type Nonenzymatic Dopamine Sensor Based on Platinum Nanoparticles-Decorated Reduced Graphene Oxide.

Dopamine (DA), a catecholamine hormone, is an important neurotransmitter that controls renal and cardiovascular organizations and regulates physiological activities. Abnormal concentrations of DA cause unfavorable neuronal illnesses such as Parkinson's disease, schizophrenia, and attention deficit hyperactivity disorder/attention deficit disorder. However, the DA concentration is exceedingly low in patients and difficult to detect with existing biosensors. In this study, we developed an organic field-effect-transistor-type (OFET) nonenzyme biosensor using platinum nanoparticle-decorated reduced graphene oxide (Pt_rGO) for ultrasensitive and selective DA detection. The Pt_rGOs were fabricated by reducing GO aqueous solution-containing Pt precursors (PtCl4) with a chemical reducing agent. The Pt_rGOs were immobilized on a graphene substrate by π-π interactions and a conducting-polymer source-drain electrode was patterned on the substrate to form the DA sensor. The resulting OFET sensor showed a high sensitivity to remarkably low DA concentrations (100 × 10-18 M) and selectivity among interfering molecules. Good stability was expected for the OFET sensor because it was fabricated without an enzymatic receptor, and π-π conjugation is a part of the immobilization process. Furthermore, the OFET sensors are flexible and offer the possibility of wide application as wearable and portable sensors.

Selective Colorimetric Detection of Nitrite in Water using Chitosan Stabilized Gold Nanoparticles Decorated Reduced Graphene oxide

Excess nitrite (NO2-) concentrations in water supplies is considered detrimental to the environment and human health, and is associated with incidence of stomach cancer. In this work, the authors describe a nitrite detection system based on the synthesis of gold nanoparticles (AuNPs) on reduced graphene oxide (rGO) using an aqueous solution of chitosan and succinic acid. The AuNPs-rGO nanocomposite was confirmed by different physicochemical characterization methods including transmission electron microscopy, elemental analysis, X-ray diffraction, UV-visible (UV-vis) and Fourier transform infrared spectroscopy. The AuNPs-rGO nanocomposite was applicable to the sensitive and selective detection of NO2− with increasing concentrations quantifiable by UV–vis spectroscopy and obvious to the naked eye. The color of the AuNPs-rGO nanocomposite changes from wine red to purple with the addition of different concertation of NO2−. Therefore, nitrite ion concentrations can be quantitatively detected using AuNPs-rGO sensor with UV-vis spectroscopy and estimated with the naked eye. The sensor is able to detect NO2− in a linear response ranging from 1 to 20 μM with a detection limit of 0.1 μM by spectrophotometric method. The as-prepared AuNPs-rGO nanocomposite shows appropriate selectivity towards NO2− in the presence of potentially interfering metal anions.