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Papers by Seyed Aboutalebi

Wet-spinning of multifunctional graphene fibers using graphene oxide liquid crystals

In order to study the mechanical properties of nanofibers, a method based on atomic force spectro... more In order to study the mechanical properties of nanofibers, a method based on atomic force spectroscopy is introduced. The ability of the atomic force microscope to measure the forces with subnanoNewton sensitivity and nanometer-scale lateral resolution has led to using it as a powerful tool to measure the mechanical properties of nanostructured materials. In this work, composite fibers were produced by electrospinning solution of polyacrylonitrile with carbon nanofibers dispersed in dimethylformamide, which is an effective solvent for carbon nanofibers. Distance dependent measurements were performed on reinforced composite fibers. To quantitatively measure the elastic modulus of nanocomposite materials, measurements were carried out on different points on the surface of the sample and force-distance curves were then plotted. The obtained results fairly agree to previously measured values. The great improvement in elastic modulus was achieved without sacrificing the mechanical streng...

Journal of Materials Chemistry A

Low electrostatic bending stiffness of graphene oxide sheets determines the conformation and cons... more Low electrostatic bending stiffness of graphene oxide sheets determines the conformation and consequently their environmental fate in aquatic environments.

Graphene has emerged as a new class of material in materials science communities in the past few ... more Graphene has emerged as a new class of material in materials science communities in the past few years [1-4]. Discovering excellent properties of graphene and the introduction of new methods to prepare graphene have resulted in significant progress in finding numerous new applications [2-4]. Exploring new methods for mass production of monolayer carbon sheet has made it possible to formulate graphene-based materials [5-6]. Being one of the thinnest and strongest materials with exceptionally high electron mobility and heat conductivity, graphene makes an excellent filler to hybridize with other matrix materials to form composites possessing unique properties [7]. As such, graphene oxide and reduced graphene sheets have attracted significant attention as filler for polymer nanocomposites that are finding diverse applications [8-10]. However, the production of high performance and costeffective polymer-graphene composites is still a challenge mainly because of the difficulties associat...

We report the synthesis of graphene oxide/multi-walled carbon nanotube (MWCNT) composites employi... more We report the synthesis of graphene oxide/multi-walled carbon nanotube (MWCNT) composites employing an alternative and novel approach for possible application as supercapacitor materials in energy storage devices. Integrating these nanostructures resulted in a strong synergistic effect between the two materials consequently leading to a robust and superior hybrid material with higher capacitance compared to either graphene oxide or MWCNTs. Specific capacitances of 251, 85 and 60 F g−1 were obtained for graphene oxide-multi-walled carbon nanotubes, MWCNTs and graphene oxide, respectively, in a potential range from −0.1 to 0.5 V. Most importantly, a 120% increase in capacitance was observed with increasing cycle number at 20 mV s−1. The ease of synthesis and the exceptional electrochemical properties make the use of this nanostructure an attractive, alternative way of designing future supercapacitors in both conventional fields and new emerging areas.

TiO 2 nanotube arrays (TNTA) have been prepared by anodic oxidation of a Ti foil (99.7% purity, S... more TiO 2 nanotube arrays (TNTA) have been prepared by anodic oxidation of a Ti foil (99.7% purity, Sigma) acting as an anode and a Pt foil acting as a cathode at 15 V for 17 h at room temperature, followed by annealing at different temperatures ranging from 450 ⁰C to 650 ⁰C for 5 h under argon atmosphere. The electrolytes consisted of 0.2 wt% NH 4 F dissolved in a mixture of glycerol and di-ionized water (9:1 in volume). The anodic TiO 2 nanotube arrays

The significant breakthroughs of flexible gel electrolytes have attracted extensive attention in ... more The significant breakthroughs of flexible gel electrolytes have attracted extensive attention in modern wearable electronic gadgets. The lack of all-around high-performing gels limits the advantages of such devices for practical applications. To this end, developing a multi-functional gel architecture with superior ionic conductivity while enjoying good mechanical flexibility is a bottleneck to overcome. Herein, an architecturally engineered gel, based on PVA and H3PO4 with different molecular weights of PVA for various PVA/H3PO4 ratios, was developed. The results show the dependence of ionic conductivity on molecular weight and also charge carrier concentration. Consequently, fine-tuning of PVA-based gels through a simple yet systematic and well-regulated strategy to achieve highly ion-conducting gels, with the highest ionic conductivity of 14.75 ± 1.39 mS cm-1 have been made to fulfill the requirement of flexible devices. More importantly, gel electrolytes possess good mechanical ...

Polymer

Abstract Recently, incorporation of nanomaterials into gel electrolytes has been used to improve ... more Abstract Recently, incorporation of nanomaterials into gel electrolytes has been used to improve the electrochemical performance of energy storage devices. Here, graphene oxide-based gel electrolyte samples were prepared by exploiting Poly (vinyl alcohol) as the polymer matrix and H₃PO₄ as ion producer. There has been a significant improvement in ionic conductivity by adding a small amount of graphene oxide, 0.05 wt % and 0.1 wt % for large-area graphene oxide and small-area graphene oxide which is 23.85 ± 0.23 and 29.21 ± 0.06 mS cm−1, respectively. The improvement may be attributed to the homogeneous distribution of graphene oxide, acting as an ionic conductivity promoter. Moreover, graphene oxide sheets with small area have lower bulk resistance as they can move easily through the gel with high amount of bound water, resulting in high ionic conductivity. Additionally, the GO containing gel has superior mechanical properties (tensile modulus of 2.77 ± 0.65 MPa and tensile strength of 8.33 ± 1.99 MPa) and high cyclic stability (retained 89% of initial specific capacitance after 2000 cycles) compared to the one without GO which makes it a potential candidate for use as gel electrolyte in flexible and wearable electronic gadgets.

Applied Physics A

The paper aims to explain the effect of laser irradiation on the nonlinear optical (NLO) response... more The paper aims to explain the effect of laser irradiation on the nonlinear optical (NLO) response of MoS2 nanosheets. MoS2-layered nanostructures were prepared by liquid-phase exfoliation (LPE) in deionized (DI) water. The characterization of MoS2 dispersion proves the formation of 2-3-layered 2H-MoS2 nanosheets with less than 100 nm lateral dimension. The NLO response of prepared dispersion was explored using the Z-scan technique with 532 nm continuous wave (CW) laser beam at 30, 50, 70 mW powers. The main finding of this research is that the nonlinear refractive index (n2) of MoS2 dispersion is a laser-assisted tunable quantity. It has been shown that the nonlinear refractive index of MoS2 nanosheets is altered up to 48% of its initial value only by 1-h laser irradiation with 30 mW power.

Journal of Energy Storage

Abstract We here report a breakthrough in the fabrication of green high performance symmetric sup... more Abstract We here report a breakthrough in the fabrication of green high performance symmetric supercapacitors. Our system is based on binder-free reduced graphene oxide foam electrodes using NaCl aqueous electrolyte (1 M). A liquid crystal ultra large graphene oxide sheets dispersion in water was used for the fabrication of foams through freeze drying. Proper initial self-assemblage/alignment of graphene oxide (GO) sheets of the aqueous mixture on the substrate and exposure to vacuum sublimation conditions resulted in a unique 3D open structure. A novel technique based on nitrogen adsorption has been applied for the first time to estimate the average wall thickness. The combination of the use of ultra large GO, freeze drying, and employment of NaCl electrolyte resulted in an exceptionally high capacitance of 618.15 F g−1 at a current density of 3.0 A g−1. This is the highest value ever reported for a pure carbonaceous electrode in a two electrode system. Although electrical double layer storage is dominant, our device exhibits a high capacitance typical of pseudo capacitive systems and does not suffer from a limited cycle life. Another excellent feature of the novel supercapacitor is the persistence of high capacitive behavior (132.13 F g−1) even at a high charge/discharge rate of 51.5 A g−1. This is mainly attributed to the amphiphilic character of the reduced graphene oxide sheets resulting from the high percentage of the carbonyl/carboxyl surface residual oxygenate groups which impart an enhanced wetting of the surface by the electrolyte in addition to inducing a higher concentration of Na+ and Cl- ions in the electrical double layers. Our optimum combination of energy and power densities is 42.92 W kg−1 and 1.35 kW h kg−1, respectively.

Advanced Materials Technologies

Nanoscale, 2016

Engineered molybdenum disulfide (MoS2) crystals with preferred orientation can readily exfoliate ... more Engineered molybdenum disulfide (MoS2) crystals with preferred orientation can readily exfoliate into ultra-large MoS2 sheets that form liquid crystalline dispersions in water.

Proceedings of the National Academy of Sciences, 2016

Graphene oxide (GO), the main precursor of graphene-based materials made by solution processing, ... more Graphene oxide (GO), the main precursor of graphene-based materials made by solution processing, is known to be very stiff. Indeed, it has a Young’s modulus comparable to steel, on the order of 300 GPa. Despite its very high stiffness, we show here that GO is superflexible. We quantitatively measure the GO bending rigidity by characterizing the flattening of thermal undulations in response to shear forces in solution. Characterizations are performed by the combination of synchrotron X-ray diffraction at small angles and in situ rheology (rheo-SAXS) experiments using the high X-ray flux of a synchrotron source. The bending modulus is found to be 1 kT, which is about two orders of magnitude lower than the bending rigidity of neat graphene. This superflexibility compares with the fluidity of self-assembled liquid bilayers. This behavior is discussed by considering the mechanisms at play in bending and stretching deformations of atomic monolayers. The superflexibility of GO is a unique ...

Advanced Functional Materials, 2016

The development of electrically conducting fibers based on known cytocompatible materials is of i... more The development of electrically conducting fibers based on known cytocompatible materials is of interest to those engaged in tissue regeneration using electrical stimulation. Herein, it is demonstrated that with the aid of rheological insights, optimized formulations of graphene containing spinnable poly(lactic-co-glycolic acid) (PLGA) dopes can be made possible. This helps extend the general understanding of the mechanics involved in order to deliberately translate the intrinsic superior electrical and mechanical properties of solutionprocessed graphene into the design process and practical fiber architectural engineering. The as-produced fibers are found to exhibit excellent electrical conductivity and electrochemical performance, good mechanical properties, and cellular affinity. At the highest loading of graphene (24.3 wt%), the conductivity of as-prepared fibers is as high as 150 S m-1 (more than two orders of magnitude higher than the highest conductivity achieved for any type of nanocarbon-PLGA composite fibers) reported previously. Moreover, the Young's modulus and tensile strength of the base fiber are enhanced 647-and 59-folds, respectively, through addition of graphene.

The recent discovery of liquid crystalline (LC) behavior of graphene oxide (GO) dispersions in va... more The recent discovery of liquid crystalline (LC) behavior of graphene oxide (GO) dispersions in various organic, and aqueous media brings added control to the assembly of larger structures using the chemical process approach.[1-3] The LC state can be used to direct the ordered assembly of nanocomponents in macroscopic structures via simple methods like wet-spinning.