Sharif Digital Repository

Nanofibrous structures that mimic the native extracellular matrix and promote cell adhesion have attracted considerable interest for biomedical applications. In this study, GO-modified nanofibrous biopolymers (GO) were prepared by electrospinning blended solutions of chitosan (80 vol%), polyvinyl pyrrolidone (15 vol%), polyethylene oxide (5 vol%) containing GO nanosheets (0–2 wt%). It is shown that GO nanosheets significantly change the conductivity and viscosity of highly concentrated chitosan solutions, so that ultrafine and uniform fibers with an average diameter of 60 nm are spinnable. The GO-reinforced nanofibers with controlled pore structure exhibit enhanced elastic modulus and... 

According to current researches, graphene oxide (GO) membranes show promising desalination properties due to ease of synthesis, low production cost, and high efficiency. There are several experimental works to study ionic sieving properties of GO membranes. However, it is difficult to characterize atomistic mechanism of water permeation and ion rejection by experimental approaches. On the other hand, there exist a few reports in which the atomistic picture of water permeation across GO membranes is investigated by means of molecular dynamics (MD) simulation. In the present work, in addition to water desalination, the atomic scale mechanism of ion rejection is studied using large scale MD... 

Here in, for the first time, we report a new and simple procedure for preparing reduced graphene oxide/nickel-cobalt double layered hydroxide composite on the nickel foam (Ni-Co LDH/rGO/NF) via a fast and simple two-step electrochemical method including potentiostatic routes in the presence of CTAB as a cationic surfactant. Graphene oxide coated nickel foam prepared by simple immersion method. After that, the prepared electrode reduced electrochemically to obtain rGO/NF electrode. Finally, the rGO/NF electrode was used as cathode for electrodeposition of Ni-Co LDH in the presence of CTAB as cationic surfactant. The prepared electrodes were characterized by field emission scanning electron... 

Biosensors could be used as digital devices to measure the sample infield. Consequently, computational programming along with experimental achievements are required. In this study, a novel biosensor/artificial neural network (ANN) integrated system was developed. Poly (3,4-ethylenedioxy-thiophene)(PEDOT), graphene oxide nano-sheets (GONs) and laccase (Lac) were used to construct a biosensor. The simple and one-pot process was accomplished by electropolymerizing 3,4-ethylenedioxy-thiophene (EDOT) along with GONs and Lac as dopants on glassy carbon electrode. Scanning electron microscopy (SEM) and electrochemical characterization were conducted to confirm successful enzyme entrapment. The... 

The aim of this work is to investigate the effect of molybdenum disulfide on tribological properties of Ultra-high-molecular-weight polyethylene (UHMWPE). UHMWPE/MoS2 nano-composites were prepared using in-situ polymerization and Ziegler-Natta catalytic system. Studies showed that, in order to obtain the optimum tribological properties, interlayer distance between nanosheets should be as high as possible. Therefore, the nanosheets were subjected to oxidation using the required oxidants followed by thermal shock and ultrasound. Fourier-transform infrared spectroscopy (FTIR) analysis was used to determine the formation of functional groups which indicate the formation of S═O bond in the... 

Controlled growth of atomic monolayers of IV-VII transition metal dichalcogenides (TMDs) has provided unprecedented opportunities to fabricate modern optoelectronic nanodevices. However, synthesis of large-area and high quality two-dimensional TMDs is still challenging. We have synthesized WS2 and MoS2 nanosheets by atmospheric pressure chemical vapor deposition (APCVD) at wide-range of processing conditions. The nanostructures were analyzed by optical and confocal microscopy, atomic force microscopy, Raman spectroscopy, and X-ray diffraction to determine the thickness, lateral size and structure of the deposits. Through designing and performing of a set of controlled experiments as well as... 

In this study, four types of mixed matrix membranes were fabricated using polysulfone (as the base polymer) and different contents of graphene oxide (GO) nanosheets (as modifier) through wet phase inversion method. Based on the amounts of GO (0, 0.5, 1, and 2 wt%), the synthesized membranes named as M1, M2, M3, and M4, respectively. The membranes characteristics were evaluated using FE-SEM, FT-IR, and water contact angle measurements. In addition, the performance of the prepared membranes was investigated in terms of basic parameters: filtrate water flux, nitrate removal efficiency, and antifouling properties. Results showed significant improvements of the characteristics of modified... 

The present study reports a simple electrochemical approach to the fabrication of a new nanocomposite containing PtPd nanoflowers (NFs) promoted with two-dimensional (2D) nanosheets (NSs) structure cuprous oxide (Cu2O) supported on reduced graphene oxide (rGO) (PtPd-NFs/Cu2O-NSs/rGO). Scanning electron microscopy, X-ray diffraction, Fourier transform infrared spectra, Raman spectroscopy, and energy dispersive X-ray spectroscopy are used for characterization of the PtPd-NPs/Cu2O-NPs/rGO. SEM images showed that vertical-standing arrays of Cu2O with an edge length up to 1 μm and thickness of about 20 nm are electrodeposited on the surface of rGO film. Also, PtPd needle-like NFs with visible and... 

In the present work, the effect of graphene oxide (GO) nanosheets on the antibacterial activity of CuO nanowire arrays under visible light irradiation is shown. A combined thermal oxidation/electrophoretic deposition technique was employed to prepare three-dimensional networks of graphene oxide nanosheets hybridized with vertically aligned CuO nanowires. With the help of standard antibacterial assays and X-ray photoelectron spectroscopy, it is shown that the light-activated antibacterial response of the hybrid material against gram-negative Escherichia coli is significantly improved as the oxide functional groups of the GO nanosheets are reduced. In order to explore the physicochemical... 

In this work, graphene oxide (GO) aqueous suspensions prepared by a chemical exfoliation method showed a fluorescence peak at ∼615 nm. Photoluminescence spectroscopy determined that functionalization of the GO sheets by 3-(2-Aminoethylamino) propyltrimethoxysilane molecules significantly quench the fluorescence property of the GO sheets. Fourier transform infrared spectroscopy confirmed proper functionalization of the GO sheets. Curcumin was applied as a fluorescent natural material with an emission peak at ∼550 nm wavelength for green fluorescent labeling of the functionalized-GO sheets. The curcumin-labeled functionalized-GO sheets showed an intense emission band fluorescent property with... 

Pulse-potential coelectrodeposition of reduced graphene oxide/zinc (rGO-Zn) nanocomposite coating is directly controlled upon a steel substrate from a one-pot aqueous mixture containing [GO-/Zn2+]δ+ nanoclusters. GO nanosheets are synthesized by modified Hummer's approach while Zn cations are produced in the solution and deposited on GO nanosheets using anodic dissolution technique. Eventually, nanoclusters are reduced to rGO-Zn film through an electrochemical process. Chemical composition, surface morphology, and corrosion resistance of the thin film are characterized. Results show that the corrosion resistance of rGO-Zn coating is approximately 10 times more than the bare steel. © 2018 S.... 

Chalcostibite copper antimony sulfide (CuSbS2) micro- and nanoparticles with a different shape and size have been prepared by a new approach to hot injection route. In this method, sulfur in oleylamine (OLA) is employed as a sulfonating agent providing a simple route to control the shape and size of the particles, which enables the optimization of CuSbS2 for a variety of applications. The sulfur to metallic precursor ratio appears to be one of the most effective parameters along with the temperature and time for controlling the size and morphology of the particles. The growth mechanism study shows in addition to the CuSbS2 phase the presence of not previously observed intermediate phases... 

The authors demonstrate efficient direct electron transfer from the enzyme glucose oxidase to vertically aligned gold nanorods with a diameter of ~160 nm and a length of ~2 μm that are covalently linkage to a 3-dimensional network of reduced graphene oxide nanosheets. The assembly can be prepared by a 2-step electrochemical procedure. This hybrid structure holds the enzyme in a favorable position while retaining its functionality that ultimately provides enhanced performance for enzymatic sensing of glucose without utilizing mediators. The nanorod assembly was applied to the voltammetric detection of glucose. Figures of merit include an electrochemical sensitivity of 12 μA·mM−1·cm−2... 

The design of 3-dimensional (3-D) nanostructured materials on the novel current collectors has recently considered as a promising strategy for developing high-performance supercapacitors. Herein, in the first step, a novel 3-D nickel nanocone arrays (NCAs) are synthesized on the surface of nickel plate (NP) by a one-step electrodeposition method without using any template (NCAs-NP). Then, a simple and efficient method is developed for fabricating ternary metal sulfides electrodes based on the electrodeposition of nickel cobalt iron sulfide (Ni-Co-Fe-S) ultrathin nanosheets on the surface of NCAs-NP. Taking advantages of the unique flower like structure of Ni-Co-Fe-S ultrathin nanosheets and... 

A fluorometric method was developed for simultaneous determination of Cr(VI) and Cr(III) ions using graphitic carbon nitride nanosheets (g-C3N4 NS) as a nanosized fluorescent indicator probe. The g-C3N4 NS were prepared using high-temperature carbonization of melamine followed by ultrasonication-assisted liquid exfoliation. The g-C3N4 NS display fluorescence with excitation/emission peaks located at 320 and 450 nm. The chromium speciation is based on the quenching of g-C3N4 NS fluorescence. The total concentration of chromium is determined after oxidation of Cr(III) to Cr(VI). The Cr(III) content was then calculated by subtracting the concentration of Cr(VI) from that of total chromium. The... 

Here in, for the first time, we report a new and simple procedure for preparing reduced graphene oxide/nickel-cobalt double layered hydroxide composite on the nickel foam (Ni-Co LDH/rGO/NF) via a fast and simple two-step electrochemical method including potentiostatic routes in the presence of CTAB as a cationic surfactant. Graphene oxide coated nickel foam prepared by simple immersion method. After that, the prepared electrode reduced electrochemically to obtain rGO/NF electrode. Finally, the rGO/NF electrode was used as cathode for electrodeposition of Ni-Co LDH in the presence of CTAB as cationic surfactant. The prepared electrodes were characterized by field emission scanning electron... 

Herein, a novel sensing platform based on NiCo layered double hydroxide (LDH) nanosheets/graphene nanoribbons (GNRs) modified glassy carbon electrode is presented for sensitive non-enzymetic determination of glucose. In the first step, nanoflower-like NiCo LDH nanosheets were grown on the surface of ZIF-67 dodecahedron nanocrystals which used as sacrificial template and were further characterized by means of scanning electron microscopy (SEM), transmission electron microscopy (TEM), energy dispersive X-ray spectroscopy (EDX), X-ray powder diffraction (XRD) and FTIR. In the next step, in order to fabricate a mechanically stable modified electrode, the as-prepared nanosheets were mixed with... 

A high performance asymmetric supercapacitor (ASC)has been fabricated by using nickel oxide-cobalt oxide nanosheets (NiO–CoO NSs), which were directly grown on carbon nanotubes (CNTs)and hydrothermal carbon spheres (HTCs)as positive and negative electrodes, respectively. Both electrode materials are binder-free prepared by using a catalytic chemical vapour deposition (CVD)approach followed by a facile hydrothermal method for cathode and a one-step environmental-friendly route called hydrothermal carbonization for anode. Using NiO–CoO NSs@CNTs and HTCs, which were directly grown on Ni foam, not only leads to a very small equivalent series resistance, but also provides an impressive capacitive... 

The modified Hummer technique was used in the preparation of graphene oxide (GO) nanosheets, and then SiO 2 decorated GO [GO(SiO 2 )] nanosheets were synthesized via the sol–gel method. Then, ultrahigh-molecular-weight polyethylene (UHMWPE) nanocomposites loaded with 0.5, 1, 1.5, and 2 wt % of GO(SiO 2 ) were prepared using magnesium ethoxide/GO(SiO 2 )-supported Ziegler–Natta catalysts via the in situ polymerization. Morphological study of the prepared polymer powders was assessed using field-emission scanning electron microscopy, which showed that GO(SiO 2 ) nanohybrids have been uniformly dispersed and distributed into the UHMWPE matrix. Also, the neat UHMWPE and its nanocomposites were... 

While the differentiation factors have been widely used to differentiate mesenchymal stem cells (MSCs) into various cell types, they can cause harm at the same time. Therefore, it is beneficial to propose methods to differentiate MSCs without factors. Herein, magnetoelectric (ME) nanofibers were synthesized as the scaffold for the growth of MSCs and their differentiation into neural cells without factors. This nanocomposite takes the advantage of the synergies of the magnetostrictive filler, CoFe 2 O 4 nanoparticles (CFO), and piezoelectric polymer, polyvinylidene difluoride (PVDF). Graphene oxide nanosheets were decorated with CFO nanoparticles for a proper dispersion in the polymer through...