Department of Nano Materials (2011 - Present)
Physics
Physics, Sharif University of Technology, Tehran, Iran
Physics
Physics, Sharif University of Technology, Tehran, Iran
Physics
Physics, Sharif University of Technology, Tehran, Iran
I earned my B.Sc, M.Sc, and P.hD degrees from Department of Physics, Sharif University of Technology. I am presently an associate professor of Nanomaterials at department of Materials Engineering, Tarbiat Modares University. My main research interests are in the area of nanomaterials synthesis, processing and applications especially, laser processing of nanomaterials, oxide semiconductors, arc discharge synthesis and processing of nanomaterials, photo-catalysts, water splitting and optical nanomaterials.
Synthesis and utilization of nanostructures exhibiting both magnetic and plasmonic characteristics have been considered significantly important. In this research, 12-nm iron nanoparticles were first synthesized by the electric arc discharge procedure. Gold nanoparticles were then synthesized via the chemical reduction of gold salt which were used to cover magnetic nanoparticles uniformly. X-ray powder diffraction, scanning and transmission electron microscopies, and UV–Vis spectroscopy were implemented to determine available phases, particles sizes, the morphology of nanoparticles and optical characteristics. Surface plasmon resonance behavior appeared at nm for iron-based@ gold nanoparticles. Vibrating sample magnetometry of iron nanopar
We are proposing a novel method to form thin films that are composed of ordered arrays of iron-gold core-shell (Fe@Au) nanoparticles with tunable optical responses. The method is based on the crosslinking of the adjacent Fe@Au nanoparticles using bifunctional group organic molecules. Molecules of m-phenylenediamine (MPD) as conjugated diamines can crosslink the adjacent Fe@Au nanoparticles. Experimental results show that the larger the Fe@Au/MPD mass ratio, the more intense the corresponding plasmon resonance. Images of the optical microscopy and FE-SEM show that there is a tradeoff between the Fe@Au/MPD mass ratio and the formation of ordered arrays of Fe@Au nanoparticles. In particular, Fe@Au/MPD ≈0.4% is the optimum mass ratio for form
Interface modification in perovskite solar cells is a key factor for achieving high power conversion efficiency by suppressing electron-hole recombination and accelerating charge carrier extraction. Here, we use a series of phenyl ammonium derivatives, phenyl ammonium iodide (PAI), benzyl ammonium iodide (BAI), and phenyl ethyl ammonium iodide (PEAI), to modify the interface between methylammonium lead triiodide (MAPbI3) perovskite and Spiro-OMeTAD as a hole transport layer in solar cell devices. The structural and optical properties of the perovskite films are studied and the results reveal the formation of two-dimensional perovskite interfacial layers on the surface of the MAPbI3 film modified with PEAI and BAI whereas the MAPbI3 layer mo
Flame-treatment as a simple, low cost, and highly reliable strategy was applied to effectively enhance the photoelectrochemical (PEC) properties of liquid phase deposited Ti-doped hematite thin films. The samples were heat-treated in three steps: 2 hours at 600 ?C, one minute at 800 ?C, and then 90 seconds in the flame of a paraffin wax candle. The microstructure studies revealed that the granular – morphology of the films depends on Ti doping levels and varies from acicular-like for the undoped and 1% Ti doped to spherical-like for 2–4% Ti, and then to warm-like morphology for 5% Ti-doped samples. The optical band-gap energy values of the samples decreased from 1.94 eV for the undoped to 1.53 eV for the 4% Ti-doped sample. The PEC inve
The real mechanisms beyond the effect of nanoparticles on oil phase displacement by water are still not completely understood. So, in this research, the simultaneous effects of charge and concentration of silica nanoparticles on the oil droplet detachment from calcite surface has been investigated for the first time. For this aim, the parameters of oil droplet contact angle, oil Center Of Mass, Mean Square Displacement and viscosity of water phase have been studied by using molecular dynamics simulation. The thickness of 15?A is selected for all simulations after checking the thickness effect on contact angle results. It was declared that initial shape of oil droplet affected on final contact angle slightly with the relative error of 0.7%.
Topological Insulators are systems where the broken time reversal symmetry gives rise to protected edge modes that support backscatter-free and one-way propagation of electromagnetic waves by opening non-trivial bandgaps. In this study we investigate a oneway topologically protected waveguide in the frequency range of f= 6.0 to 8.0 GHz. The time reversal symmetry is broken by an applied magnetic field in the z direction. We show that the waveguide propagates the light in only one direction that can be controlled by the applied magnetic field and no backscattering is present in the waveguide which results in a near 100% transmission of light to the output. Furthermore, we investigate effect of the applied magnetic field on the topological pr
Recent advances and studies have shown that inorganic nanomaterials based on heavy elements represent a new contrast agent which is highly appropriate for X-ray computed tomography (CT) in comparison with commercial Iohexol contrast agents which have several limitations, including short imaging time, rapid renal clearance and toxicity. In this contribution, elemental bismuth (Bi) nanoparticles with polyethylene glycol (PEG) coating are synthesised by pulsed Nd:YAG laser ablation of Bi target in PEGs with 400 and 600?g/mol molecular weight. The effect of PEG molecular weight as surface coating on colloidal stability and size distribution of Bi nanoparticles were investigated. It is found that by in situ surface modification during the ablati
Growth of the gold plasmonic shells on the iron based nanoparticles could enhance the linear and nonlinear optical properties of the iron based nanostructures, due to the coupling of the localized surface plasmon (LSP) modes on the inner and outer surface of each Au-shell. We have fabricated the iron based nanoparticles via arc discharge technique in water that is a cost effective and simple single-step synthesis route. Then, the gold shells have been grown chemically on the iron-based cores. The structural properties of core-shell nanoparticles have been investigated using X-ray diffraction (XRD) and transmission electron microscopy (TEM). XRD measurements have exposed the existence of three phases of iron (oxides) including pure iron, mag
In this study, by using tungsten nanoparticles as filler and RTV silicon rubber (SR) as the matrix, thick flexible highly loaded composites were fabricated (up to 80 wt%). Interestingly, by incorporation of W particles in SR, the tensile strength of composites improved by average, eg 45% augmentation in 80 wt%. The young modulus was increased as well, eg from 0.38 MPa in the pure polymer to 1.10 MPa in 80 wt% composite. Experimental results showed that, the absorption of x-ray increases considerably by increasing tungsten proportion of samples. For example, the mass attenuation coefficient of 59.5 keV x-ray grows from 0.20 cm 2 g− 1 in the pure polymer to 2.32 cm 2 g− 1 in 80 wt%. Moreover, the attenuation process is simulated by a Mont
In this study zirconia nanoparticles (NPs) were successfully synthesized via the direct current (DC) arc discharge method in water. Formation mechanism of NPs and the effect of arc current on morphological, structural and optical properties of NPs have been studied. The NPs were synthesized at four different currents in the 40–160 A range. SEM observations showed NPs are spherical in shape and their average size decrease from 40 to 22 nm by increasing the current from 40 to 160 A. XRD analysis revealed phase composition of NPs is a mixture of tetragonal and monoclinic for all the samples, and the phase fraction of NPs are arc current dependent in such a way that an increase in the current leads to an increase in the weight percent of the
TiC nanoparticles were synthesized by submerged direct current (DC) arc discharge in liquid. Synthesis process was carried out in methanol, ethanol and acetone under inert atmosphere by applying 40 A between two pure titanium electrodes with vertical configuration. X-ray diffraction, field emission scanning electron microscopy and UV–visible spectroscopy were used for characterization of nanoparticles. In addition, plasma species were characterized via optical emission spectroscopy (OES). According to the obtained results, nanoparticle shape is spherical, and average particle size of nanoparticles is 28, 45 and 38 nm in methanol, ethanol and acetone, respectively. Although composition of nanoparticles in ethanol and acetone is single-phas
In this study, Bi2O3 nanoparticles were employed as computed tomography (CT) contrast agents. In this regard, X-ray attenuation of Bi2O3 nanoparticles, prepared via DC arc discharge in water, was investigated. In addition, the optical, structural, morphology and cytotoxicity properties of afforded nanoparticles were also studied. The electric arc discharge was done via bismuth electrodes in a water medium. Then, to stabilise Bi2O3 nanoparticles, chitosan molecule was cross linked via glutaraldehyde around Bi2O3 nanoparticles. X-ray diffraction analysis demonstrated the monoclinic structure and field emission-scanning electron microscopy images clarified the average size of Bi2O3 as 40 nm. Fourier transform infrared analysis proved chitosan
Bismuth based rod-like nanostructures were prepared via oriented attachment of colloidal bismuth based nanoparticles synthesized by direct current (DC) arc discharge in liquid. For the synthesis of bismuth based nanoparticles 5 A and 20 A DC electrical currents were applied between two pure bismuth electrodes in water. Bismuth based nanoparticles extracted from the water after 30 days then dispersed in ethanol. Bismuth based rod-like nanostructures formed via the oriented attachment mechanism in ethanol during 30 days. According to X-ray diffraction (XRD) patterns of as-prepared samples, the main parts of the particles were bismuth phase while after 30 days bismuth oxide and bismuth hydroxide phases were dominant. To investigate the spe
The control of thin film nanocomposite (TFN) membranes cross-linking degree is an important factor to design new membranes and optimizing permeation characteristics. The Fe3O4 nanoparticle's based TFN membranes due to potentially added magnetic responsive properties to the membrane has a great importance in developing membrane architectures. Fe3O4/polyamide (PA) TFN membranes filled with nanoparticles in different sizes and concentrations have been synthesized. Cross-linking degree of PA layer characterized with Fourier transform spectroscopy (FTIR) and x-ray photoelectron spectroscopy (XPS) methods to evaluate size dependency of the cross-linking degree of PA layer network. Obvious correlations and competitions between concentration and si
The poor adhesion of nitride coatings to steel substrates is one of the main challenges for industrial applications. In this study, plasma nitriding process and TiN functional intermediate layer were used in order to increase the adhesion of TiCN coating to the hot worked steel H13 substrate and also to improve its mechanical properties. The functionally graded nanostructured TiCN coating was deposited using pulsed-DC plasma-assisted chemical vapor deposition (PACVD) method. The coatings microstructural and mechanical properties were investigated using X-ray diffraction (XRD), scanning electron microscopy (SEM), optical microscopy (OM), Rockwell-C indentation, micro hardness and ball-on-disk tests. The results showed that peaks of TiN and T
A new synergetic hybrid Ag/ZnO nanostructure was fabricated which is able to cause photocatalytic degradation (in high yields) of methylene blue under visible light as well as in the dark. In this nanostructure, ZnO was synthesized using the arc discharge method in water and was coupled with Ag via a chemical reduction method. X-ray photoelectron spectroscopy (XPS) and photoluminescence spectroscopy results confirmed the existence of defects in ZnO in the hybrid nanostructures; these defects act as electron traps and inhibit the recombination of electron-hole pairs. The absorption edge of the hybrid nanostructure shifts toward the visible region of the spectrum due to a combination of the Ag plasmonic effect and the defects in ZnO. Band-edg
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