Sharif Digital Repository

Asian red ginseng was used for green reduction of chemically exfoliated graphene oxide (GO) into reduced graphene oxide (rGO). The reduction level and electrical conductivity of the ginseng-rGO sheets were comparable to those of hydrazine-rGO ones. Reduction by ginseng resulted in repairing the sp 2 graphitic structure of the rGO, while hydrazine-rGO showed more defects and/or smaller aromatic domains. The ginseng-rGO sheets presented a better stability against aggregation than the hydrazine-rGO ones in an aqueous suspension. Whilst the hydrophobic hydrazine-rGO films exhibited no toxicity against human neural stem cells (hNSCs), the hydrophilic GO and ginseng-rGO films (as more... 

Nickel modified graphite electrodes (G/Ni) prepared by galvanostatic deposition were examined for their redox process and electrocatalytic activities towards the oxidation of methanol, ethanol, 1-propanol and 2-propanol in alkaline solutions. The methods of cyclic voltammetry (CV), chronoamperometry (CA) and impedance spectroscopy (EIS) were employed. In CV studies, the electrochemical response, peak current varied in the order of MeOH > EtOH > 1-PrOH > 2-PrOH. Under the CA regime, a higher catalytic rate constant obtained for methanol oxidation was in agreement with CV measurements. Lower charge transfer resistance was obtained for low carbon alcohols oxidation and significantly higher... 

In this study, adsorption of important pollutant cations on the surface of graphitic carbon nitride (g-C3N4) was investigated by density functional theory. The calculations indicated that N6 cavity surrounded by triazine units is the most probable adsorption site on this surface. The structural optimizations also predicted a planar surface for Cr3+, and Ni2+/g-C3N4 systems while the structure of the surface for other systems indicated a considerable distortion with strong dependency on the cation size. Also, g-C3N4 surface exhibited the high adsorption energies for Cr3+, As3+, and Sb3+ ions in the gas phase. However, formation energies of the metal-aquo complexes of these cations indicated... 

The planned design of nanocomposites combined with manageable production processes, which can offer controllability over the nanomaterial structure, promises the practical applications of functional nanomaterials. Hollow core-shell nanostructure architectures represent an emerging category of advanced functional nanomaterials, whose benefits derived from their notable properties may be hampered by complicated construction processes, especially in the sensing domain. In this regard, we designed a highly porous three-dimensional array of hierarchical hetero Cu(OH)2@CoNi-LDH core-shell nanotubes via a quick, very simple, green, and highly controllable three-step in situ method; they were... 

The electrocatalytic oxidation of hydrazine was studied over Ni, Cu, Co and Ni-based ternary alloy on graphite electrodes in alkaline solution. The catalysts were prepared by cycling the graphite electrode in solutions containing Ni, Cu and Co ions at cathodic potentials. The synergistic effects and the catalytic activity of the modified electrodes were investigated by cyclic voltammetry (CV), chronoamperometry (CA) and electrochemical impedance spectroscopy (EIS). It was found that, in the presence of hydrazine, the modified Ni-based ternary alloy electrode (G/NiCuCo) exhibited a good catalytic activity for the oxidation of hydrazine at a reduced overpotential and it has a significant high... 

In this paper, the bending modulus of a multi-layered graphene sheet is investigated using a geometrically based analytical approach. For this purpose, a bending potential energy is derived, based on the van der Waals interactions of atoms belonging to the two neighboring sheets of a double-layered graphene sheet. The inter-atomic spacing between the adjacent layers is determined along the line of action of the applied bending moments. The bending potential of the double-layered sheet is calculated by summing up the potentials at discrete hexagons over the length and width of the sheet. A multi-layered graphene sheet is considered as consisting of many stacking double-layers. It is observed... 

Metal-organic framework (MOF) based graphene oxide (GO) recently merits of attention because of the relative correspondence of GO with metal ions and organic binding linkers. Furthermore, introducing the GO to the Co-MOF to make a new nanoporous hybrid have are improved the selectivity and stability of the Co-MOF. Here the graphene oxide/cobalt metal organic framework (GO/Co-MOF) was synthesized by a solvothermal process using cobalt salt and terephthalic acid and used for biocidal activity, against the growth of the Gram-negative Escherichia coli and Gram-positive Staphylococcus aureus bacteria. X-ray diffraction, Fourier transform infrared spectroscopy and Raman spectroscopy were confirmed... 

A novel modified pyrolytic graphite electrode with nano-diamond/graphite was fabricated. The electrochemical response characteristics of the modified electrode toward the epinephrine (EN) and uric acid (UA) were studied by means of cyclic and linear sweep voltammetry. The structural morphology and thickness of the film was characterized by SEM technique. The prepared electrode showed an excellent catalytic activity in the electrochemical oxidation of EN and UA, leading to remarkable enhancements in the corresponding peak currents and lowering the peak potentials. The prepared modified electrode acts as a highly sensitive sensor for simultaneous determination of EN and UA in the presence of... 

In this paper, the effect of aluminum content on the formation mechanism, volume fraction, morphology and particle size distribution of graphite has been investigated. Addition of aluminum on ductile iron causes some fundamental changes in iron-carbon phase-diagram and as a result, improves the graphite formation during eutectic transformation. The results reveals that aluminum compounds have been formed in the core of graphite nodules, thus aluminum plays an important role in the formation of graphite nodules. Furthermore, it is indicated that an increase in the aluminum content also leads to an increase in the number of graphite nodules and a decrease in the nodules size. By using EPMA,... 

CeO 2-TiO 2 nanoparticles were prepared by the sol-gel process using 2-hydroxylethylammonium formate as room-temperature ionic liquid and calcined at different temperatures (500-700°C). CeO 2-TiO 2-graphene nanocomposites were prepared by hydrothermal reaction of graphene oxide with CeO 2-TiO 2 nanoparticles in aqueous solution of ethanol. The photocatalysts were characterized by X-ray diffraction, BET surface area, diffuse reflectance spectroscopy, scanning electron microscopy, and Fourier transformed infrared techniques. The results demonstrate that the room-temperature ionic liquid inhibits the anatase-rutile phase transformation. This effect was promoted by addition of CeO 2 to TiO 2.... 

The potential of carbon-based nanosheet membranes with functionalized pores is great as water treatment membranes. Using the molecular dynamic simulation technique, the dimethyl sulfoxide (DMSO) separation from the water/DMSO binary solution is investigated, and the functionalized graphene nanosheets are used as a membrane. This membrane was functionalized by –F (fluorine) and –H (hydrogen) functional groups. For the separation of DMSO, external hydrostatic pressures up to 100 MPa were applied to the considered systems. The separation mechanism was based on molecular size. Multiple analyses were done to study the capability of considered membranes for the separation of DMSO molecules from... 

Bacteriorhodopsin (bR) molecules were utilized as light-driven proton pumps for green as well as effective reduction of single-layer graphene oxide (GO) sheets. The bR molecules and graphene sheets were separated from each other in an aqueous environment by using a polytetrafluoroethylene membrane filter, in order to prevent their direct interactions (including attachment of the bR molecules onto the GO). Although reduction of GO using hydrazine or bR showed similar deoxygenation levels (based on X-ray photoelectron spectroscopy), the former resulted in formation of CAN bonds which can substantially decrease the electrical conductivity of the reduced sheets. The electrical characteristics of... 

A soil microbial fuel cell was investigated that uses soil and groundwater to generate electricity. The cathode surface area and materials are always important for increasing power. Power density was shown to be a linear function of cathode surface area. Biofilm formation on the graphite cathode was observed to be helpful in enhancing power output and maximum performance reached 89.2 mW/m2. As an application for the insertion-type soil microbial fuel cell, nitrate removing was investigated in cathode. Nitrate was reduced in an aerobic cathode at the rate of 37.5 mg nitrate/lit/day and 55 mg nitrate/lit/day in anaerobic cathode  

Injectable hydrogels which mimic the physicochemical and electromechanical properties of cardiac tissue is advantageous for cardiac tissue engineering. Here, a newly-developed in situ forming double-network hydrogel derived from biological macromolecules (oxidized alginate (OA) and myocardial extracellular matrix (ECM)) with improved mechanical properties and electrical conductivity was optimized. 3-(2-aminoethyl amino) propyltrimethoxysilane (APTMS)-functionalized reduced graphene oxide (Amine-rGO) was added to this system with varied concentrations to promote electromechanical properties of the hydrogel. Alginate was partially oxidized with an oxidation degree of 5% and the resulting OA... 

Background: Researchers are trying to study the mechanism of neural stem cells (NSCs) differentiation to oligodendrocyte-like cells (OLCs) as well as to enhance the selective differentiation of NSCs to oligodendrocytes. However, the limitation in nerve tissue acces-sibility to isolate the NSCs as well as their differentiation toward oligodendrocytes is still challenging. Purpose: In the present study, a hybrid polycaprolactone (PCL)-gelatin nanofiber scaffold mimicking the native extracellular matrix and axon morphology to direct the differentiation of bone marrow-derived NSCs to OLCs was introduced. Materials and Methods: In order to achieve a sustained release of T3, this factor was... 

In this paper, a bottom-up hydrothermal route is reported for the synthesis of oxygen and nitrogen co-decorated carbon quantum dots (CQDs) using ammonium hydrogen citrate (AHC) as a single precursor. DLS data approved the formation of 4.0 nm (average size) CQDs. XRD pattern shows the interlayer spacing (002) of 3.5 Å for CQDs, which is exactly the same as that of crystalline graphite. XPS and FTIR spectra verified the formation of oxygen and nitrogen functional groups on the CQDs surface. Co-decorated carboxyl, hydroxyl and amine groups on the CQDs surfaces make them as promising polyelectrolyte for gene delivery. Toxicity assay showed a survival rate of 70% under different incubation times... 

A modified carbon paste electrode is prepared by incorporating multi-walled carbon nanotube (MWCNT) and cobalt salophen (CoSal). A mixture of fine graphite powder with 10 wt% of MWCNT is applied for the preparation of carbon paste (by dispersing in Nujol) and finally modified with CoSal. The electrocatalytic oxidation of tryptophan (Trp) is investigated on the surface of the MWCNT/CoSal-modified electrode using cyclic voltammetry (CV) and differential pulse voltammetry (DPV). Using the modified electrode, the kinetics of the electro-oxidation of Trp is considerably enhanced, by lowering the anodic overpotential through a catalytic fashion. The mechanism of electrochemical behavior of Trp at... 

This work presents the catalytic graphitization process of phenolic resins (PR's) by addition of in situ nano-Fe particles as catalyst. Pyrolysis treatments of prepared compositions including various contents of nano-Fe particles were carried out at 600–1200 °C for 3 h under reducing atmosphere and graphitization process were evaluated by different techniques such as X-Ray diffraction (XRD), Field Emission Scanning Electron Microscopy (FESEM), High Resolution Transmission Electron Microscopy (HRTEM), Simultaneous Thermal Analysis (STA) and Raman spectroscopy that mainly performed to identify the phase and microstructural analysis, oxidation resistance and extend of graphitized carbon... 

Coating of graphite flakes with MgO/carbon nanocomposite was carried out via gaseous state reaction between mixture of Mg metal, CO gas and graphite flakes at 1000 °C. XRD and FE-SEM analysis of coating showed that the coating was comprised of MgO nano particles and amorphous carbon distributed smoothly and covered the graphite surface evenly. Thermodynamic calculations were employed to predict the reaction sequences as well as phase stability. The effect of coating on water wettability and oxidation resistance of graphite was studied using contact angle measurement and TG analysis, respectively. It was demonstrated that the reaction between Mg and CO could result in MgO/C nanocomposite... 

Background: This research follows some investigations through neural tissue engineering, including fabrication, surface treatment, and evaluation of novel self-stimuli conductive biocompatible and degradable nanocomposite scaffolds. Methods: Gelatin as a biobased material and polyvinylidene fluoride (PVDF) as a mechanical, electrical, and piezoelectric improvement agent were co-electrospun. In addition, polyaniline/graphene (PAG) nanoparticles were synthesized and added to gelatin solutions in different percentages to induce electrical conductivity. After obtaining optimum PAG percentage, cold atmospheric plasma (CAP) treatment was applied over the best samples by different plasma variable...