Sharif Digital Repository

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... 

To improve the efficiency of electrochemical processes for environmental remediation, we present a new type of hybrid nanomaterials based on leaf-like copper-based quaternary transition metals and spongy monolayer graphene. To demonstrate the functionality of the hybrid electrocatalyst, fast and competent electrooxidation of water and glucose is shown. The mechanism of improved catalysis is ascribed to the synergetic catalytic effect of quaternary Cu-Ni-Fe-Co alloy with dendritic morphology along with the highly conductive and spongy structure of the graphene monolayer. It is shown that water oxidation can be performed at a low overpotential of 315 mV to reach a current denisty of 100 mA... 

Recently, huge attention has been drawn to improve optical sensing devices based on photonic resonators in the presence of graphene. In this paper, based on the transfer matrix approach and TE polarization of the incident electromagnetic waves, we numerically evaluate the transmission and reflection spectra for one-dimensional photonic resonators and surface plasmon resonances with strained graphene, respectively. We proved that a relatively small strain field in graphene can modulate linearly polarized resonant modes within the photonic bandgap of the defective crystal. Moreover, we study the strain effects on the surface plasmon resonances created by the evanescent wave technique at the... 

An economical epichlorohydrin cross-linked chitosan @ magnetic Fe3O4/activated carbon nanocomposite, CH-EP@Fe3O4/AC, was successfully synthesized and used as a suitable adsorbent material for removal of a triphenylmethane cationic dye, Malachite green (MG), an anionic dye, Reactive red 120 (RR120), and Mercury ions (Hg2+) from aqueous solution. The prepared adsorbent has been characterized with Fourier transform infrared spectroscopy, X-ray diffraction, Scanning electron microscopy, Thermogravimetric analysis, Brunauer–Emmett–Teller analysis as well as Vibrating sample magnetometer. According to the result of Brunauer–Emmett–Teller isotherm, the prepared adsorbent has a specific surface area... 

The Ni-P/Zn-Ni compositionally modulated multilayer coatings CMMCs were electrodeposited from a single bath by switching the deposition current density. The corrosion resistance of the deposits was studied and compared with that of monolayers of Ni-P and Zn-Ni alloys via Tafel polarization, EIS and salt spray tests. Characterization of corrosion products by means of EDS and XRD revealed more details from the corrosion mechanism of the monolayers and multilayers. The corrosion current density of Ni-P/Zn-Ni CMMCs were around one tenth of Zn-Ni monolayer. The CMMC with incomplete layers performed lower polarization resistance and higher corrosion current density compared to the CMMC with... 

La-MOF-NH2@Fe3O4 (magnetic-MOF) was used as an efficient, ultrafast, and selective adsorbent for the separation of Congo Red (CR) with 92.02% removal after 2 min. The magnetic-MOF was identified by X-ray diffraction (XRD), thermogravimetric analysis (TGA), Brunauer-Emmett-Teller (BET) surface area, Zeta Potential analysis, analysis of the magnetic hysteresis, Fourier-transform infrared spectroscopy (FTIR), scanning electron microscope (SEM) and energy-dispersive X-ray spectroscopy (EDS). Kinetics, isotherms, the effect of pH, thermodynamic, and selectivity of CR adsorption were investigated. The results confirmed that the adsorption kinetics complied with the pseudo-second-order model. The... 

To evaluate the selectivity and efficiency of solid phase microextraction (SPME) fiber coatings, synthesized by sol-gel technology, roles of precursors and coating polymers were extensively investigated. An on-line combination of capillary microextraction (CME) technique and high performance liquid chromatography (HPLC) was set up to perform the investigation. Ten different fiber coatings were synthesized in which five of them contained only the precursor and the rests were prepared using both the precursor and coating polymer. All the coatings were chemically bonded to the inner surface of copper tubes, intended to be used as the CME device and already functionalized by self-assembly... 

We present a new dandelion-like TiO2 spheres by a modified hydrothermal method for manufacture of dye-sensitized solar cells (DSSCs). This construct is composed of numerous nanowires for employment as the scattering layer of DSSCs. Such morphology is produced by nucleation-growth-assembly mechanism. The size of the dandelion-like spheres and their morphology can be tailored by controlling the processing parameters of the modified hydrothermal process. TiO2 nanoparticles with narrow size distribution are also synthesized by hydrothermal route for the active layer of DSSCs. The nanoparticles show pure anatase phase with average size of 40 nm, whereas the dandelion-like TiO2 spheres are pure... 

An accurate and fast method for guided modes extraction in monolayer colloidal crystals and their inverse replicas is presented. These three-dimensional structures are composed of a monolayer of spherical particles that can easily and simply be prepared by self-assembly method in close packed hexagonal lattices. In this work, we describe how the guided modes, even or odd modes and light cone boundary can be easily determined using phase variations of reflection and transmission coefficients. These coefficients are quickly calculated by Fourier modal method. The band structures are obtained for a monolayer of polystyrene particles and two-dimensional TiO2 inverse opal by this proposed method  

Herein, enhancement of dye-sensitized solar cell (DSC) performance is reported by combining the merits of the dye loading of TiO2 nanoparticles and light scattering, straight carrier transport path, and efficient electron collection efficiency of TiO2 cubes. We fabricate DSC devices with various arrangement styles and compositions of the electrodes in the forms of monolayer and double layer films. For this purpose, the solvothermal synthesized TiO2 cubic particles (100-600 nm) are employed as the scattering layer, whereas TiO2 nanoparticles (15-30 nm) synthesized via a combination of solvothermal and sol-gel routes are used as the active layer of devices. We improve the photovoltaic... 

Several evidences support the idea that a small population of tumour cells representing self-renewal potential are involved in initiation, maintenance, metastasis, and outcomes of cancer therapy. Elucidation of microRNAs/genes regulatory networks activated in cancer stem cells (CSCs) is necessary for the identification of new targets for cancer therapy. The aim of the present study was to predict the miRNAs pattern, which can target both metastasis and self-renewal pathways using integration of literature and data mining. For this purpose, mammospheres derived from MCF-7, MDA-MB231, and MDA-MB468 were used as breast CSCs model. They had higher migration, invasion, and colony formation... 

We theoretically investigate the magnetoelastic coupling (MEC) and its effect on magnon transport in two-dimensional antiferromagnets with a honeycomb lattice. MEC coefficients along with magnetic exchange parameters and spring constants are computed for monolayers of transition-metal trichalcogenides with Néel magnetic order (MnPS3 and VPS3) and zigzag order (CrSiTe3, NiPS3, and NiPSe3) by ab initio calculations. Using these parameters, we predict that the spin-Nernst coefficient is significantly enhanced due to magnetoelastic coupling. Our study shows that although Dzyaloshinskii-Moriya interaction can produce spin-Nernst effect in these materials, other mechanisms such as magnon-phonon... 

We investigate systematically the spin-Nernst effect in Néel and zigzag ordered honeycomb antiferromagnets. Monolayers of transition-metal trichalcogenides, MnPSe3, MnPS3, and VPS3 show an antiferromagnetic Néel order while CrSiTe3, NiPS3, and NiPSe3 show an antiferromagnetic zigzag order. We extract the exchange and Dzyaloshinskii-Moriya interaction parameters from ab initio calculations. Using these parameters, we predict that the spin-Nernst coefficient is at least two orders of magnitude larger in zigzag compared to the Néel ordered antiferromagnets. We find that this enhancement relies on the large band splitting due to the symmetry of magnetic configuration in the zigzag order. Our... 

The fabrication of the C6N7 monolayer [Zhao et al., Sci. Bull. 66, 1764 (2021)] motivated us to discover the optical, structural, mechanical, and electronic properties of the C6N7 monolayer by employing the density functional theory (DFT) method. We find that the shear modulus and Young's modulus of the C6N7 monolayer are smaller than the relevant values of graphene. However, Poisson's ratio is more significant than that of graphene. Applying the PBE (HSE06) functional bandgap of the C6N7 monolayer is 1.2 (1.97) eV, and the electronic dispersion is almost isotropic around the Γ point. C6N7 is more active in the ultraviolet region as compared to the visible light region. This study provides... 

We propose and theoretically evaluate a plasmonic light trapping solution for thin film photovoltaic devices that comprises a monolayer or a submonolayer of wavelength-scale silver particles. We systematically study the effect of silver particle size using full-wave electromagnetic simulations. We find that light trapping is significantly enhanced when wavelength-scale silver particles rather than the ones with subwavelength dimensions are used. We demonstrate that a densely packed monolayer of spherical 700 nm silver particles enhances integrated optical absorption under standard air mass 1.5 global (AM1.5G) in a 7 μm-thick N719-sensitized solar cell by 40% whereas enhancement is smaller... 

Density functional theory (DFT) calculations have been performed to investigate the electronic structure and photocatalytic activity of a hybrid Ag3PO4(111)/g-C3N4 structure. Due to Ag(d) and O(p) states forming the upper part of the valence band and C(p), N(p), and Ag(s) the lower part of the conduction band, the band gap of the hybrid material is reduced from 2.75 eV for Ag3PO4(111) and 3.13 eV for monolayer of g-C3N4 to about 2.52 eV, enhancing the photocatalytic activity of the Ag3PO4(111) surface and g-C3N4 sheet in the visible region. We have also investigated possible reaction pathways for photocatalytic CO2 reduction on the Ag3PO4(111)/g-C3N4 nanocomposite to determine the most... 

In this article, the synthesis, characterization, and cyclic voltammetry (CV) measurements are reported for ferrocene-terminated oligophenyleneimine (OPI_Fc) and ferrocene-terminated conjugation-broken oligophenyleneimine (CB-OPI_Fc) self-assembled monolayers (SAMs) in two different electrolytes, namely, 1-ethyl-3-methylimidazolium-bis (trifluoromethyl-sulfonyl) imide (EMITFSI) ionic liquid and tetrabutylammonium hexafluorophosphate (Bu4NPF6) in acetonitrile (0.1 M solution). The SAMs were synthesized on Au surfaces by the sequential imine condensation reactions. CV was used to investigate the kinetics of electron transfer (ET) to the ferrocene, and it was observed that the standard ET rate... 

Scattering particles constitute a key light trapping solution for thin film photovoltaics where either the particles are embedded in the light absorbing layer or a thick layer of them is used as a reflector. Here we introduce a monolayer of wavelength-scale core-shell silica@Ag particles as a novel light trapping strategy for thin film photovoltaics. These particles show hybrid photonic-plasmonic resonance modes that scatter light strongly and with small parasitic absorption losses in Ag (<1.5%). In addition, their scattering efficiency does not vary significantly with the refractive index of the surrounding medium. A monolayer of these particles is applied as the top-scattering layers in a... 

We report on charge transport across self-assembled monolayers (SAMs) of short tau peptides by probing the electron tunneling rates and quantum mechanical simulation. We measured the electron tunneling rates across SAMs of carboxyl-terminated linker molecules (C6H12O2S) and short cis-tau (CT) and trans-tau (TT) peptides, supported on template-stripped gold (AuTS) bottom electrode, with Eutectic Gallium-Indium (EGaIn)(EGaIn) top electrode. Measurements of the current density across thousands of AuTS/linker/tau//Ga2O3/EGaIn single-molecule junctions show that the tunneling current across CT peptide is one order of magnitude lower than that of TT peptide. Quantum mechanical simulation... 

Graphene nanoribbon field effect transistors are promising devices for beyond-CMOS nanoelectronics. Graphene is a semiconductor material with zero bandgap and its bandgap must be changed. One of the opening bandgap methods is using graphene nanoribbons. By applying a defect, there is more increase on band gap of monolayer armchair graphene nanoribbon field effect transistor. So, by applying more than one defect, we can reach to much more increase in bandgap of graphene nanoribbon field effect transistors (GNRFET). In this paper, double-gated monolayer armchair graphene nanoribbon field effect transistors (GNRFET) with one single vacancy (1SV) defect (so-called 1SVGNRFET)are simulated and...