Sharif Digital Repository

A novel optoelectronic property of two-dimensional (2D) materials suggests they can be used for high-performance photodetector design. There has been a lot of attention paid to MoS2 and Despite its higher optical absorbance, MoSe2 has received little attention. A chemical vapor deposition system was used to prepare atomically thin MoSe2 films. Our research developed a method of preparing hexagon-shaped MoSe2 photodetector on Si/SiO2 substrates in atmospheric pressure with sawtooth edges, leading to large-scale MoSe2 layers with the size of ∼ 70µm . The Raman characterization of the grown flakes indicated that they possessed high quality few layers of MoSe2 and the distance between the two... 

The main goal of this research is to detect and characterize single-photon emitters in two-dimensional hexagonal boron nitride crystal with the help of fluorescence confocal microscope and Hanbury-Brown and Twiss interferometer. The origin of single-photon radiation in this crystal is not precisely known. It seems that the transition between energy levels, which occurs due to the presence of point defects in the crystal structure of this material, in the distance between the conduction and valence bands, is the source of single-photon radiation. This material does not require low temperature for single-photon radiation, which is an important advantage for it. In a confocal microscope, the... 

Reverse electrodialysis-based membranes are one of the most promising approaches to osmotic energy production. However, conventional reverse electrodialysis membranes have high strength and insufficient mass transfer, which leads to low power density and efficiency. In recent decades, the transport of ions at the nanoscale for the manufacture of reverse electrodialysis machines has attracted much attention. Compared to conventional devices, power density and energy conversion efficiency increase dramatically due to space constraints and electrostatic interactions at the nanoscale. Lamellar nanostructures, which can be easily fabricated by stacking two-dimensional nanosheets, may be a... 

Nanostructured graphene based membranes demonstrated excellent capabilities in various applications in nanofiltration and energy conversion due to unique atomically smooth surfaces and adjustable pore size or interlayers spacing at Angstrom scales.In addition to graphitic surface and physical confinement on ions in Graphene-oxide (GO) laminates, surface charges on such 2D-slits provide an attractive aspects to have more channels walls interactions with ions. There are some reports on the osmotic power generation using physical confinements and electrostatic interactions between ions and GO membranes. However, the results indicated insufficient power densities (1 W=m2 ) can be achieved... 

Poly vinylidene fluoride (PVDF) as a fluorine polymer with acceptable thermal, chemical and physical property attractive create attention in membrane technology for water treatment application. However, with differential surface free energy between PVDF and water (∆G_s=30 mJ/m^2) PVDF polymer is divided as a hydrophobic materials, that is one of the basic problem for PVDF polymer. Due to its hydrophobicity the water molecules repulsion away from hydrophobic PVDF membrane surface as a spontaneous process with an entropy increasing and therefore pollutant molecules with hydrophobic functional group have tendency to adsorb onto membrane surface and dominate the boundary layer. In recent years... 

In the current century, an energy storage is one of the critical and important factors affecting on human life. Rechargeable batteries, specially Lithium ion batteries (LIBs), can be considered as ideal energy storage devices including various advantages e.g. high energy and power densities. In this work, Tin IV sulfide (SnS2) and its composites, making by conductive materials e.g. Reduced Graphene Oxide (SnS2@rGO), are prepared during two different synthesis methods consisting of Hydrothermal and Hot-bath, and their properties are investigated as anode material in LIB. The structural and electrochemical analyses demonstrated that the composite sample prepared by hot-bath method exhibited... 

Wide utilization of nanomanipulation as a promising approach in microorganisms, nanoelectromechanical systems (NEMS) and assembly of nanostructures remarks the importance of nanostructures’ motion in electric fields. Despite of many reports on manipulation and assembly of nanowires (NWs) in non-uniform and alternating electric fields by dielectrophoresis, and also rotation of NWs in rotating electric fields, there is still a lack of knowledge on rotational and translational dynamics of metallic and dielectric NWs in uniform static electric fields. In this dissertation, we study the dynamics of silver (Ag) and titanium dioxide (TiO2) NWs, with diameters and lengths in the range of 40 to 100... 

Two-dimensional nanostructures can significantly absorb solar irradiation, due to diverse energy levels, large effective surfaces, layered and porous structures with adjustable physical and chemical properties. Mono and multilayers of graphene, as the first isolated 2D materials with special band-structure of a zero-band gap, along with impressive optical properties, tunable light interaction, and adjustable optical properties by chemical doping or structural defects, have great potential for the next generation of nanophotonic devices. So, graphene is an appropriate candidate for absorption, frequent reflection, and energy conversion of electromagnetic waves at the frequency range of the... 

In recent years, MXenes, a class of 2D materials, have drawn significant interest because of their special properties and layered structures. Among the MXenes family, Ti3C2 is a promising candidate in energy storage field due to its unique electrical conductivity, hydrophilicity, surface redox reactions, excellent packing density and high volumetric capacitance. In this thesis, synthesis and supercapacitor application of Ti3C2 have been investigated. HCl and LiF solution and mild exfoliation method has been used for etching Al layers from Ti3AlC2 and MXene synthesis. To analyze the structure of this material, scanning electron microscopy, atomic force microscopy, X-ray diffraction... 

Titanium carbide MXene (Ti_3 C_2 T_x) has attracted significant research interest because of its extraordinary advantages as advanced electrode material for energy storage. In this study, 4-aminodiphenylamine functionalized Ti_3 C_2 T_x/polyaniline composite synthesized by in situ growth of PANI on 4-aminodiphenylamine functionalized Ti_3 C_2 T_x nanosheets. First, Ti_3 C_2 T_x MXene nanosheets was prepared according to the minimally intensive layer delamination (MILD) method followed by sonication. Ti_3 C_2 T_x nanosheets were modified with 4-aminodiphenylamine diazonium salt. The FTIR، FE-SEM and EDS analysis were used to characterize modified Ti_3 C_2 T_x. Finally, the Ti_3 C_2 T_x... 

Titanium trisulfide (TiS3), a transition metal chalcogenide, bears the potential to replace silicon, when taking the form of nanoflakes, due to its favorable band gap and optical response. In this work, first we investigate the response of TiS3 nanoflakes to gas detection through a careful quantum computational approach and a few succinct measurements. The computations are benchmarked and compared with a relevant experiment at each step, where their results/conclusions are discussed. The most stable surface of TiS3 particles is determined to (001), in agreement with the literature. The adsorption of 5 gas molecules is characterized through formulating and estimating their adsorption... 

This work addresses adaptive neural control for a class of stochastic nonlinear systems in the nonstrict-feedback form. By introducing a nonlinear mapping, the output-constrained stochastic system transformed into a new system without constraint. The systems under study is subject to state time delay, input nonlinearity, unavailable states, unknown dynamics and actuator failure. The appropriate Lyapunov-Krasovskii functionals is used to compensate the time-delay effects, the neural network is used to approximate the unknown nonlinearities, the linear state observer is constructed to estimate the unmeasured states, and a variable separation method is used to deal with the difficulty caused by...