Amperometric Glucose Biosensor Based on Integration of Glucose Oxidase with Palladium Nanoparticles/Reduced Graphene Oxide Nanocomposite

We report on a new type of amperometric glucose biosensor that was made by integration of glucose oxidase (GOD) with palladium nanoparticles/reduce graphene oxide (Pd/RGO) nanocomposite. The Pd/RGO was prepared by a one-step reduction method in which the palladium nanoparticles and the reduced graphene oxide (RGO) were simultaneously accomplished from the reduction of dispersed solution of PdCl2 and graphite oxide (GO) with hydrazine. The asprepared nanocomposite exhibits favorable electrocatalytic activities towards the oxidation of H2O2, which makes it a good platform for the construction of the glucose biosensor. The analytical performance of the glucose biosensor is fully evaluated. It shows good analytical properties in terms of a short response time (3 s), high sensitivity (14.1 μA/mM), and low detection limit (0.034 mM). In addition, the effects of pH value, applied potential, electroactive interference and the stability of the biosensor were discussed as well.

Selected gas response measurements using reduced graphene oxide decorated with nickel nanoparticles

The work reports the synthesis of nickel nanoparticles supported on thermally reduced graphene oxides(rGO)in the ionic liquid[BMIm][NTf_(2)]through microwave decomposition reaction.Ni@rGO with the polymer poly(3,4-ethylenedioxythiophene):poly(styrene sulfonate)(PEDOT:PSS)as binder was positively tested for its response towards the oxidizing gas nitrogen dioxide(10 ppm in air),the reducing gas carbon monoxide(3000 ppm in N_(2))and the volatile organic compound(VOC)acetone(35,000 ppm in air).The results from different gases were compared at different temperatures with the best results for NO_(2) at 200℃.Additionally,it is shown for NO_(2) gas that the Ni@rGO-PEDOT:PSS polymer composite gives better results than the rGO-PEDOT:PSS polymer composite.After the heat treatment the oxidation state of pure nickel nanoparticles were confirmed by powder diffraction.

Reduced graphene oxide supported Pd-Cu-Co trimetallic catalyst:synthesis,characterization and methanol electrooxidation properties

Trimetallic palladium-copper-cobalt nanoparticles supported on reduced graphene oxide(PdCuCo/RGO)with different molar ratios of Pd,Cu and Co can be synthesized by facile chemical reduction with NaBH_4 as reductant and cetrimonium bromide as stabilizer.The morphology,structure and composition of the as-synthesized catalysts are characterized by transmission electron microscopy,X-ray diffraction and Xray photoelectron spectroscopy.The cyclic voltammetry and chronoamperometry are utilized to investigate the electrochemical activities and stabilities of the as-obtained catalysts.The results demonstrate that the PdCuCo/RGO catalyst shows superior catalytic activity and stability for methanol electrooxidation in alkaline media compared with PdCu/RGO,PdCo/RGO,and Pd/RGO catalysts.These findings suggest that the PdCuCo/RGO catalyst possesses a great potential as a promising anode catalyst for direct methanol fuel cells.

Enhanced microwave absorption performance of MOF-derived hollow Zn-Co/C anchored on reduced graphene oxide

Composite materials assembled by metal/carbon nanoparticles and 2 D layered flakes can provide abundant interfaces,which are beneficial for high-performance microwave absorbers. Herein, Zn-Co/C/RGO composites, composed of ZnCo metal-organic framework-derived Zn-Co/C nanoparticles and reduced graphene oxide(RGO), were obtained through a facile method. The multilayer structure was due to the introduction of hollow Zn-Co/C nanoparticles in the RGO sheets. ZnCo/C nanoparticles provided abundant polarization and dipole centers on the RGO surface, which enhanced the microwave absorption abilities. Different concentrations of RGO were introduced to optimize impedance matching. The minimum reflection loss(R_(L)) of Zn-Co/C/RGO with a thickness of 1.5 mm reached-32.56 dB with the bandwidth corresponding to R_(L) at-10 dB, which can reach 3.92 GHz, while a minimum R_(L) of-47.15 dB at 11.2 GHz was also obtained at a thickness of 2.0 mm. The electromagnetic data demonstrate that Zn-Co/C/RGO presented excellent absorption performance and has potential for application in the microwave absorption field.

Synthesis of graphene-supported monodisperse Au Pd bimetallic nanoparticles for electrochemical oxidation of methanol

Monodisperse Au Pd bimetallic nanoparticles（NPs） with different compositions are synthesized by using oleylamine（OAm） as reducing reagent, stabilizer, and solvent. To obtain Au Pd solid solution NPs, Pd–OAm and Au–OAm precursors are firstly prepared by mixing OAm with Palladium（II） acetylacetonate（Pd（acac）2） and HAu Cl4, respectively. Then Pd–OAm and Au–OAm precursor solutions are injected into a hot oleylamine solution to form Au Pd NPs. The size of these NPs ranges from 6.0 to 8.0 nm and the composition is controlled by varying the precursor ratio. The Au Pd NPs are loaded onto reduced graphene oxide（RGO） sheets to make catalysts. Alloy NPs show high electrocatalytic activity and stability toward methanol oxidation in the alkaline media. Their catalytic activity for methanol oxidation is found to be dependent on the NP composition. As the Pd component increases, the peak current densities during the forward scan gradually increase and reach the maximum at Au Pd2. The enhancement of alloy NPs for methanol oxidation can be attributed to a synergistic effect of Au and Pd on the surface of alloy NPs.

Investigations on pool boiling critical heat flux, transient characteristics and bonding strength of heater wire with aqua based reduced graphene oxide nanofluids

In the present work, the pool boiling critical heat flux, transient heat transfer characteristics, and bonding strength of thin Ni-Cr wire with aqua based reduced graphene oxide(r GO) nanofluids are experimentally studied. Results indicate:(i) the critical heat flux(CHF) of 0.01, 0.05, 0.1, 0.2, and 0.3 g·L^(-1) concentrations of r GO-water nanofluids varies from 1.42 to 2.40 MW·m^(-2);(ii) the CHF remains same for the tested samples during transient heat transfer studies and(iii) a constant value of CHF upto 10 tests when the nanocoated Ni-Cr wire is tested with DI water and deterioration occurs beyond this which implies a chance of peel off of r GO layer below the critical coating thickness.

Highly dispersed Co-Mo sulfide nanoparticles on reduced graphene oxide for lithium and sodium ion storage

A novel hybrid,highly dispersed spinel Co-Mo sulfide nanoparticles on reduced graphene oxide(Co3S4/CoMo2S4@rGO),is reported as anode for lithium and sodium ion storage.The hybrid is synthesized by one-step hydrothermal method but exhibits excellent lithium and sodium storage performances.The as-synthesized Co3S4/CoMo2S4@rGO presents reversible capacity of 595.4 mA·h·g^−1 and 408.8 mA·h·g^−1 after 100 cycles at a current density of 0.2 A·g^−1 for lithium and sodium ion storages,respectively.Such superior performances are attributed to the unique composition and structure of Co3S4/CoMo2S4@rGO.The rGO provides a good electronically conductive network and ensures the formation of spinel Co3S4/CoMo2S4 nanoparticles,the Co3S4/CoMo2S4 nanoparticles provide large reaction surface for lithium and sodium intercalation/deintercalation,and the spinel structure allows fast lithium and sodium ion diffusion in three dimensions.

Integrating reduced graphene oxides and PPy nanoparticles for enhanced electricity from water evaporation

Developing high-performance nanostructured materials is key to deliver the potential of hydrovoltaic technology into practical applications.As single-component materials have approached its limit in generating hydrovoltaic electricity,the development of multi-component hydrovoltaic materials has been necessary in continuously boosting the electricity output.Here,we report a hydrovoltaic material by integrating reduced graphene oxides and polypyrrole nanoparticles(rGO/PPy),where the rGO contributes improved conductivity and large specific surface area while PPy nanoparticles enable enhanced interaction with water.The device fabricated with this material generates a short-circuit current of 6μA as well as a maximum power density of over 1μW/cm3 from natural evaporation of water.And the substantial ion-PPy interaction enables robust voltage generation from evaporation of various salt solutions.Moreover,an outstanding scaling ability is demonstrated by connecting 10 devices in series that generate a sustainable voltage of up to~2.5 V,sufficing to power many commercial devices,e.g.LED bulb and LCD screen.

Enhanced positive humidity sensitive behavior of p-reduced graphene oxide decorated with n-WS_(2) nanoparticles

Most resistance-type humidity sensors exhibit negative humidity sensitivity,i.e.,their resistance decreases with a corresponding increase in humidity.This is primarily attributed to the dominant role of ionic conduction in adsorbed water.In this work,a humidity sensor based on a p-type reduced graphene oxide(p-rGO)with positive humidity sensitivity is proposed.Moreover,its positive humidity sensing response is further enhanced by n-type WS_(2) nanoparticles modification.The results show that both rGO and r GO/WS_(2) humidity sensors have good linear response in the relative humidity(RH)range of0%-91.5%.The sensitivity of the rGO/WS_(2) humidity sensor is 1.87 times that of rGO humidity sensor,which is mainly attributed to p-n heterojunction between rGO and WS_(2).Besides,the r GO/WS_(2) humidity sensor has small humidity hysteresis(-3%RH)and good repeatability.This work demonstrates a humidity sensor based on rGO/WS_(2) composite film and provides a facile route for fabricating humidity sensor with positive humidity sensing properties.

Green Synthesis of Silver Nanoparticles and Their Reduced Graphene Oxide Nanocomposites as Antibacterial Agents:A Bio-inspired Approach

In this paper, silver nanoparticles （AgNPs） and AgNPs/reduced graphene oxide （RGO） nanocomposites were prepared using lemon juice under microwave irradiation （MWI） and UV light irradiation. AgNPs with face-centered cubic structure RGO peaks were observed by X-ray diffraction. The UV-Vis spectrum showed modifications in the absorption peaks of the AgNPs with the concentration of the precursor solution and irradiation time, and the optimized condition was obtained for 20 min MWI and 60 s of UV light. Raman analysis confirmed the presence of RGO as D and G bands in the spectrum. Transmission electron microscopy analyses confirmed that the AgNPs of size ranging from 3 to 8 nm were anchored onto the RGO sheets. The antibacterial properties of the AgNPs/RGO nanocomposites were investigated using gram-negative bacteria. The results revealed that AgNPs/RGO nanocomposites consisting of approximately 5 wt% AgNPs can achieve antibacterial performance similar to that of neat AgNPS. This method can be useful for the applications of AgNPs-based nanocomposites, where minute amount of silver will be utilized.

Hydrolytic dehydrogenation of ammonia borane catalyzed by poly(amidoamine) dendrimers-modified reduced graphene oxide nanosheets supported Ag_(0.3)Co_(0.7) nanoparticles

Poly(amidoamine) dendrimers-modified reduced graphene oxide nanosheets(PAMAM/rGO) composite was selected as a carrier of heterogeneous Ag0.3Co0.7nanoparticles in order to obtain an excellent catalyst for ammonia borane(AB) hydrolysis. During the synthetic processes, GO could easily assembled with PAMAM by the electrostatic and hydrogen-bonding interactions. Structural characterization revealed that Ag0.3Co0.7bimetallic nanoparticles with uniform size distribution of 5 nm are well dispersed on PAMAM/rGO composite architecture. Ag0.3Co0.7@PAMAM/rGO was found to be a highly active and reusable catalyst in hydrogen generation from the hydrolysis of AB with a turnover frequency value(TOF) of 19.79 molH2min-1molM-1at 25.0±0.1℃ and retained 75.4% of their initial activity with a complete release of hydrogen in five runs. The relatively high TOF value and low apparent activation energy(34.21 kJ mol-1) make these Ag0.3Co0.7@PAMAM/rGO NPs as a high-efficient catalyst for catalytic dehydrogenation of AB facilitating the development of practically applicable energy storage materials.

DNA Induced FePt Bimetallic Nanoparticles on Reduced Graphene Oxide for Electrochemical Determination of Dopamine

FePt bimetallic nanoparticles were formed on reduced graphene oxide（rGO） with the help of double-stranded DNA（dsDNA） via a simple and universal route to obtain a FePt/DNA-rGO composite. The FePt nanoparticles with an average size of about 5 nm were well dispersed on rGO. FePt/DNA-rGO modified glassy carbon electrode（GCE） exhibited excellent electrocatalytic activity for the oxidation of dopamine（DA） with a detec- tion limit of 100 nmol/L（S/N = 3）. In addition, the FePt/DNA-rGO based electrochemical sensor showed an excellent selectivity for DA in the presence of ascorbic acid（AA）, uric acid（UA） and other interference reagents. The as-prepared electrochemical biosensor shows great promise in the application of clinical diagnostics.

Gold nanoparticles/single-stranded DNA-reduced graphene oxide nanocomposites based electrochemical biosensor for highly sensitive detection of cholesterol

High density and uniform distribution of the gold nanoparticles functionalized single-stranded DNA modified reduced graphene oxide nanocomposites were obtained by non-covalent interaction.The positive gold nanoparticles prepared by phase inversion method exhibited good dimensional homogeneity and dispersibility,which could readily combine with single-stranded DNA modified reduced graphene oxide nanocomposites by electrostatic interactions.The modification of single-stranded DNA endowed the reduced graphene oxide with favorable biocompatibility and provided the preferable surface with negative charge for further assembling of gold nanoparticles to obtain gold nanoparticles/single-stranded DNA modified reduced graphene oxide nanocomposites with better conductivity,larger specific surface area,biocompatibility and electrocatalytic characteristics.The as-prepared nanocomposites were applied as substrates for the construction of cholesterol oxidase modified electrode and well realized the direct electron transfer between the enzyme and electrode.The modified gold nanoparticles could further catalyze the products of cholesterol oxidation catalyzed by cholesterol oxidase,which was beneficial to the enzyme-catalyzed reaction.The as-fabricated bioelectrode exhibited excellent electrocatalytic performance for the cholesterol with a linear range of 7.5–280.5μmol·L^(−1),a low detection limit of 2.1μmol·L^(−1),good stability and reproducibility.Moreover,the electrochemical biosensor showed good selectivity and acceptable accuracy for the detection of cholesterol in human serum samples.

Novel Ag2S nanoparticles on reduced graphene oxide sheets as a super-efficient catalyst for the reduction of 4-nitrophenol

Here,Ag2S nanoparticles on reduced graphene oxide（Ag2S NPs/RGO） nanocomposites with relatively good distribution are synthesized for the first time by conversing Ag NPs/RGO to Ag2S NPs/RGO via a facile hydrothermal sulfurization method.As an noval catalyst for the reduction of 4-nitrophenol（4-NP）,it only takes 5 min for Ag2S NPs/RGO to reduce 98% of 4-NP,and the rate constant of the composites is almost 13 times higher than that of Ag NPs/RGO composites.The high catalytic activity of Ag2S NPs/RGO can be attributed to the following three reasons：（1） Like metal complex catalysts,the Ag2S NPs is also rich with metal center Ag（δ^＋）,with pendant base S（δ） close to it,and thus the Ag and basic S function as the electron-acceptor and proton-acceptor centers,respectively,which facilitates the catalyst reaction;（2）RGO features the high adsorption ability toward 4-NP which provides a high concentration of 4-NP near the Ag2S NPs;and（3） electron transfer from RGO to Ag2S NPs,facilitating the uptake of electrons by 4-NP molecules.

Engineering Shewanella-re duce d graphene oxide aerogel biohybrid to efficiently synthesize Au nanoparticles

Biosynthesizing Au nanoparticles(AuNPs)from gold-bearing scraps provides a sustainable method to meet the urgent demand for AuNPs.However,it remains challenging to efficiently biosynthesize AuNPs of which the diameter is less than 10 nm from a trace amount of Au^(3+)concentration at the level of tens ppm.Here,we constructed an exoelectrogenic cell(eCell)-conductive reduced-graphene-oxide aero-gel(rGA)biohybrid by assembling Shewanella sp.S1(SS1)as living biocatalyst and rGA as conductive ad-sorbent,in which Au^(3+)at trace concentrations would be enriched by the adsorption of rGA and reduced to AuNPs through the extracellular electron transfer(EET)of SS1.To regulate the size of the synthe-sized AuNPs to 10 nm,the strain SS1 was engineered to enhance its EET,resulting in strain RS2(pYYD-P tac-ribADEHC&pHG13-P_(bad)-omcC in SS1).Strain RS2 was further assembled with rGA to construct the RS2-rGA biohybrid,which could synthesize AuNPs with the size of 7.62±2.82 nm from 60 ppm Au^(3+)so-lution.The eCell-rGA biohybrid integrated Au^(3+)adsorption and reduction,which enabled AuNPs biosyn-thesis from a trace amount of Au^(3+).Thus,the required Au^(3+)ions concentration was reduced by one or two orders of magnitude compared with conventional methods of AuNPs biosynthesis.Our work devel-oped an AuNPs size regulation technology via engineering eCell’s EET with synthetic biology methods,providing a feasible approach to synthesize AuNPs with controllable size from trace level of gold ions.

Ultra-small amorphous MoS2 decorated reduced graphene oxide for supercapacitor application

Amorphous materials have recently gained much attention as electrode materials in supercapacitor application due to the presence of larger amount active sites which can efficiently increase the storage capacity of the materials.Nano engineering is an elegant approach to fully utilize the advantages of the amorphous structure.Moreover,large surface area and high conductivity of reduced graphene oxide(RGO)can efficiently increase the storage capacity of the system.Exploiting this idea,in the present work,we have successfully synthesized amorphous MoS2 of two different sizes on reduced graphene oxide and thoroughly investigated the supercapacitor behavior of the system.The specific capacitance of the composite structures has been found to be largely increased with decreasing size of the amorphous nano particle.The specific capacitance of amorphous MoS2-RGO composite containing nearly 50 nm of MoS2 found to be 270 F/g whereas when the particle size is reduced to 5–7 nm,value of specific capacitance increases to 460 F/g.The large increase in specific capacitance with the tuning of the size of amorphous nano particle has been explained by the presence of a large number of active sulfur edges of ultra-small MoS2 nano structure along with the better charge transport which can effectively increase the storage capacity of the overall system.The retention in the capacitance of the material has been found to be 90%after 5000 cycles.

A novel ZnO/reduced graphene oxide and Prussian blue modified carbon paste electrode for the sensitive determination of Rutin

A carbon paste modified sensor based on a novel composite of zinc oxide nanoparticles deposited on reduced graphene oxide(ZnO-rGrO) and Prussian blue(PB) was drop-cast(ZnO-rGrO-PB/MCPE) for the sensitive estimation of Rutin(Rtn) at pH 7.0.The high surface area of ZnO-rGrO and electrocatalytic property of PB promotes the oxidation of Rtn. Field emission scanning electron microscope(FE-SEM) and energy-dispersive X-ray spectroscopy(EDX) techniques were employed to confirm the deposition of ZnO-rGrO and PB on carbon paste electrode(CPE). The ability of ZnO-rGrO-PB/MCPE in charge transfer at the interface was investigated using electrochemical impedance spectroscopy(EIS). The heterogeneous rate constant(ks) and the charge transfer coefficient(α) have been calculated as 6.08 s^(-1) and 0.74 respectively. This sensor showed a wide linear response for Rtn from 7.0×10^(-8)to 7.0×10^(-6) M and 7.0×10^(-6) to 1.0×10^(-4) M with a limit of detection(2.05±0.04)×10^(-8) M(S/N=3). The application of ZnO-rGrO-PB/MCPE was found in the analysis of Rtn in fruit juice samples using standard addition method. This sensor showed good reproducibility, stability, selectivity and sensitivity.

Synthesis of a nitrogen-doped titanium dioxide-reduced graphene oxide nanocomposite for photocatalysis under visible light irradiation

A nitrogen-doped titanium dioxide-reduced graphene oxide (N-TiO2-RGO)nanocomposite has been synthesized by the combination of a hydrothermal method and a thermal treatment under a NH3/N2 atmosphere.The resulting composites are characterized by Fourier transform infrared spectroscopy, scanning electron microscopy,transmission electron microscopy,diffuse reflectance absorption spectroscopy,energy-dispersive X-ray spectroscopy,and Raman characterization techniques.The sequence of the thermal treatment and hydrothermal treatment processes is shown to influence the photocatalytic activity of nitrogen-doped composites.The composites synthesized by using this method show better photocatalytic activities toward the degradation of acetaldehyde under visible light irradiation compared with P25,N-TiO2,and TiO2-RGO.By applying the thermal treatment process after the hydrothermal pro- cess,nitrogen atoms can be simultaneously doped in the lattice ofTiO2nanoparticles and on the surface of reduced graphene oxide sheets.The conversion of acetaldehyde,as the model molecule of volatile organic compounds,is measured in a continuous stirred-tank reactor until the steady state condition is reached. The conversion of 50 ppm acetaldehyde,in an air flow under illumination from an 80W Hg lamp with a UV cut-off filter,reaches 62% after a 1-h reaction using a 0.07g N-TiO2-RGO sample with an optimum loading of 2wt% graphene oxide.In comparison,the photocatalytic activity of P25 for the degradation of acetaldehyde under visible light irradiation is only 8% under the same reaction conditions.The reaction rates for acetaldehyde degradation are calculated and predicted with pseudo-first-order reaction kinetics,and the activity result of the best N-TiO2-RGO sample is 12.3times higher than for P25.

Underpotential Deposition Preparation of Pt-loading AuNPs/Reduced Graphene Oxide and Its Catalytic Detection of Catechol

Ultralow Pt-loading Au nanoparticles have been fabricated on the surface of reduced graphene oxide （RGO） by using underpotential deposition （UPD） monolayer redox replacement process. The Pt/Au/RGO modified electrode exhibits an excellent electrocatalytic activity toward catechol and hydroquinone. Under the optimized condition, the separation of peak-to-peak between hydroquinone and catechol is 197 mV, which is wide enough to distinguish the isomers of benzenediol. Catechol is detected by the Pt/Au/RGO/GCE with a low detection limit in the presence of hydroquinone.

A Prussian blue route to nitrogen-doped graphene aerogels as efficient electrocatalysts for oxygen reduction with enhanced active site accessibility

Developing high-performance nonprecious-metal electrocatalysts for the oxygen reduction reaction （ORR） is crucial for a variety of renewable energy conversion and storage systems. Toward that end, rational catalyst design principles that lead to highly active catalytic centers and enhanced active site accessibility are undoubtedly of paramount importance. Here, we used Prussian blue nano- particles to anchor Fe/Fe3C species to nitrogen-doped reduced graphene oxide aerogels as ORR catalysts. The strong interaction between nanosized Fe3C and the graphitic carbon shell led to synergistic effects in the ORR, and the protection of the carbon shell guaranteed stability of the catalyst. As a result, the aerogel electrocatalyst displayed outstanding activity in the ORR on par with the state-of-the-art Pt/C catalyst at the same mass loading in alkaline media, good performance in acidic media, and excellent stability and crossover tolerance that rivaled that of the best nonprecious-metal ORR electrocatalysts reported to date.