Sharif Digital Repository

In this study, graphene oxide/gold/methylene blue (GO/Au/MB) ternary composites were synthesized and characterized through UV–vis, FTIR, XRD, XPS, SEM, and TEM analyses towards plasmon-enhanced singlet oxygen (1O2) generation. Through using gold nanoparticles and MB photosensitizers, the visible light adsorption capability of GO was enhanced by 115%. Moreover, applying this ternary composite as a photocatalyst under visible light interestingly revealed a drastic step-increase of 14% (i.e., from 9 to 23%) in the conversion of photooxygenation of Anthracene. This behavior was rationalized using finite-difference time-domain (FDTD) simulations which confirms the plasmonic field of gold... 

The search for cathode materials with fast oxygen reduction reaction (ORR) catalytic activities and high ionic conductivity is the key obstacle to SOFCs commercialization and its operation at low temperatures. In order to search for a cathode with enhanced catalytic functionality, herein we report a single-phase CoFe2O4 (CFO) and CoGd0.2Fe1.80O4 (CGFO), which can be employed as an active cathode to improve electrocatalytic ORR functionalities at low temperature. It is found that CGFO having enriched oxygen vacancies exhibits the least polarization resistance (RP) of 0.42 Ωcm2 compared to the pure CFO which shows polarization resistance of 0.56 Ω cm2 under H2/air conditions. Furthermore,... 

Two-dimensional MXenes are the newly emerging family of nanomaterials with competitive performance for nano-device development. Surface functional groups and abundant binding sites make these materials ideal candidates for sensor applications. Herein, we report the successful fabrication of a MXene-based nano-bio device for capturing, sensing, and filtering the Escherichia coli (E. coli) bacteria. Mannose carbohydrate, which binds strongly to E.coli's fimH protein via glucan multivalent interactions, is used as the bio-receptor element. MXene's structure was engineered to guarantee efficient E. coli capturing without mannose detachment. Electrochemical impedance spectroscopy (EIS) and cyclic... 

Here, we report the synthesis and characterization of a binuclear Co(ii) complex (Co2(2py)2Cl4) with two dinaphtho-diazacrown ether macrocyclic ligands, bearing two pyridine arms as a colourimetric and fluorescent sensor for detecting different xylene isomers as well as acting as a catalyst for the oxidation of o- and m-xylene under vacuum at room temperature. Chromogenic detection occurred when Co2(2py)2Cl4 was exposed to the xylene isomers, wherein the original blue colour of the complex changed to green and green-blue in the presence of o- and m-xylene, respectively. Meanwhile, no colour change was observed in the presence of the p-xylene isomer. Fluorescence spectroscopy revealed that... 

Chiral recognition has long been a challenging issue to deal with in biological systems, drug design and food authentication. Implementing nanoparticle-based probes with intrinsic or induced chirality in this field has addressed several issues concerning sensitivity, reliability, rapidness and the cost of chiral sensing platforms. Yet, research into chiral nanoprobes that can be used for visual monitoring of chiral substances is still in its infancy. As part of this study, a visual chiral recognition platform has been developed in which a combination of blue-emitting carbon dots (BCDs) and mercaptopropionic acid-capped CdTe quantum dots (MPA-QDs) with inherent chiroptical activity were... 

Here, a solution combustion method was employed to construct a photoanode based on bismuth vanadate (BV) composition. To curtail the fast charge recombination, phosphorus-doped g-C3N4 nanosheets (PCNS) in combination with BV are considered a potential approach. The prepared solution combustion facilitated the formation of a BiVO4-PCNS (BV-PCNS) hybrid photoanode with worm-like morphology with a simple setup. The weight ratio of PCNS/BiVO4 and the loading volume/cm2 were optimized to determine the most efficient photoanode. The highest photocurrent density of 0.5 mA/cm2 at 1.23 V vs reversible hydrogen electrode (RHE) under 1 sun illumination was achieved for the hybrid nanostructure at 2 wt... 

With the advent of the Internet of Things (IoT), the development of self-powered sensors has received much attention. Introducing triboelectric nanogenerators (TENGs) as a power source that converts mechanical movement into electrical signals has been admired recently. Moreover, the monitoring of humidity has become enormously essential in several technological contexts from environment monitoring to biomedical applications, thus joining these two subjects provides a huge benefit in achieving self-powered humidity sensors. Here, in this research, facile, low-priced and self-powered humidity sensors are fabricated utilizing transition-metal dichalcogenides (TMD) nanosheets. Semi-vertical SnS2... 

Novel Bi2S3/NiCo2O4 nanocomposites (BS/NCO) with various mass ratios were prepared using NiCo-MOF as precursor. The morphology, composition and structure of the as-prepared catalysts were studied by different techniques such as FE-SEM, EDX, XRD, FT-IR, VSM and BET. The as-synthesized composite with 20 % Bi2S3 (%20 BS/NCO) demonstrated the best performance in reduction reaction of 4-nitrophenol (4-NP). The enhanced catalytic activity of %20 BS/NCO composite compared to the Bi2S3 and NiCo2O4 can be assigned to the optimized synergistic effects between the two pristine materials. Thermodynamic parameters and the activation energy of the reaction in the presence of %20 BS/NCO composite were... 

This paper, for the first time, presents a lateral tunneling transistor based on a two-dimensional boron nitride (BN) and hexagonal boron-carbon-nitrogen (hBCN) heterostructure. The device operation is analyzed based on a non-equilibrium Greens Function (NEGF) method and an atomistic tight-binding (TB) model. The TB hopping parameters are achieved by fitting the bandstructure to density functional theory (DFT) results. This model has been used to calculate the electrical characteristics of the device, such as ION/IOFFratio, subthreshold swing, and intrinsic gate-delay time. The results indicate a switching ratio of over eight orders of magnitude, much higher than the previous two-dimensional... 

In this project, the protective effect of Biebersteinia multifida root extract (BMRE) against corrosion of 1018 low carbon steel (1018LCS) in HCl solutions was appraised by assessing weight loss, electrochemical impedance spectroscopy (EIS), and polarization at 25 °C. The maximum inhibitory efficacy for the concentration of 1 g/l of the BMRE was 92.8% at 25 °C after 2 h and increased to 95.3% after 24 h of immersion. Polarization experiments have shown that the extract in acidic solutions can act as a mixed corrosion inhibitor. The corrosion inhibitory efficacy of BMRE decreased with increasing temperature, and at all temperature settings studied, the adsorption of BMRE molecules on 1018 LCS... 

Resonance Raman spectroscopy has long been established as one of the most sensitive techniques for detection, structure characterization, and probing the excited-state dynamics of biochemical systems. However, the analysis of resonance Raman spectra is much facilitated when measurements are accompanied by Density Functional Theory (DFT) calculations that are expensive for large biomolecules. In this work, resonance Raman spectra are therefore computed with the Density Functional Tight-Binding (DFTB) method in the time-dependent excited-state gradient approximation. To test the accuracy of the tight-binding approximations, this method is first applied to typical resonance Raman benchmark... 

In this contribution, the effect of physical immobilization of methylene blue (MB) into silica nanocomposites was investigated on the conversion and selectivity of the photooxygenation of anthracene and dihydroartemisinic acid (DHAA). Physically immobilized photocatalysts were synthesized through a developed Stöber method and were thoroughly characterized by UV–Vis, FTIR, XRD, XPS, SEM, TEM, HR-TEM, BET-BJH, and EDX analyses. Based on the TEM and UV–Vis results, it was determined that enhancement of the MB concentration as an organocatalyst for the Stöber reaction led to an increase in the size of the nanoparticles from 54 to 183 nm and a 21 nm blue shift in their UV–Vis spectra. Moreover,... 

Understanding the effect of crystallographic orientation on the twinnin/detwinning mechanisms in NiTi shape memory alloys at an atomistic scale can help to control and tune the mechanical properties and failure behavior of such materials. In this work, we employed classical molecular dynamics (MD) and density functional theory (DFT) computational methods to better understand how twinning and detwinning occurs through a combination of slip, twin, and shuffle on 〈0 1 0〉, 〈1 1 0〉, and 〈1 1 1〉 crystallographic orientations under uniaxial tensile test. Elastic constants including Young's Modulus (E), Bulk modulus (B), Poisson's ratio (ν), and Shear Modulus (G) are obtained and computed for... 

In this contribution, reduced grapheme oxides (rGO) with immobilized tin oxide (SnO2) nanocatalysts were synthesized via the Incipient Wetness Impregnation (IWI) method. To characterize the SnO2/rGO composites, several analyses including the; XRD, Raman, FTIR, ICP-OES, BET-BJH, XPS, TEM, and TPD were utilized. Then the effects of parameters including reaction time, total metal loading, and the initial sulfur concentration of model fuel in the dibenzothiophene (DBT) oxidation desulfurization process were evaluated. After determining the optimal conditions for the aforementioned parameters, the influences of 3 effective factors of the molar ratio of oxidant/substrate (O/S), the molar ratio of... 

Very recently, two-dimensional (2D) iodinene, a novel layered and buckled structure has been successfully fabricated (Qian et al 2020 Adv. Mater. 32 2004835). Motivated by this latest experimental accomplishment, for the first time we conduct density functional theory, first-principles calculations to explore the structural, electronic, and optical properties of monolayer, few-layer and bulk iodinene. Unlike the majority of monoelemental 2D lattices, iodinene is predicted to be an intrinsic semiconductor. On the basis of calculations using the generalized gradient approximation of Perdew-Burke-Ernzerhof for the exchange-correlation functional and the Heyd-Scuseria-Ernzerhof (HSE06)... 

The Hubble tension may introduce a new course of action to revise the standard Lambda cold dark matter (ΛCDM) model to unravel dark energy and dark matter physics. The Hubble parameter can be reconstructed by late-time observations of the background evolution model independently. We relate the reconstructed Hubble parameter to the structure formation and large-scale structure observables in this work. We use excursion set theory to calculate the number density of dark matter haloes and the mass function of progenitors. We obtain results for both the Markov and non-Markov extensions of excursion set theory in the context of spherical and ellipsoidal collapse. We show that the number density... 

This work suggests a green method for synthesizing Au nanoparticles (AuNPs) using the aqueous extract of Salix aegyptiaca extract. The mechanism of green synthesized AuNPs was examined by molecular electrostatic potential (MEP) calculations. AuNPs were characterized with different techniques such as Ultraviolet–visible spectroscopy (UV–vis), Fourier-transform infrared spectroscopy (FT-IR) spectroscopy, X-ray diffraction (XRD), and Transmission electron microscopy (TEM). Electrochemical investigation of modified glassy carbon electrode using AuNPs (AuNPs/GCE) shows that the electronic transmission rate between the modified electrode and [Fe (CN)6]3−/4− increased. Process of oxidation, energy... 

Density functional theory calculations are utilized for probing the effect of doping Al, Ga, and Zn atoms on the sensing performance of a C60 fullerene in detecting the dichlorosilane (DS) gas. We predicted that the interaction of pure C60 with DS is physisorption, and the sensing response (SR) of C60 is 8.6. The adsorption energy of DS changes from − 21.4 to − 84.4, − 86.7, and − 90.7 kJ/mol, by doping the Al, Ga, and Zn metals, respectively. Also, the corresponding SR meaningfully rises to 33.7, 52.3, and 92.9, indicating that the Zn transition metal much more increases the sensitivity of fullerene compared to the Al and Ga metals. Our theoretical results further support the fact that the... 

The potential of carbon-based nanosheet membranes with functionalized pores is great as water treatment membranes. Using the molecular dynamic simulation technique, the dimethyl sulfoxide (DMSO) separation from the water/DMSO binary solution is investigated, and the functionalized graphene nanosheets are used as a membrane. This membrane was functionalized by –F (fluorine) and –H (hydrogen) functional groups. For the separation of DMSO, external hydrostatic pressures up to 100 MPa were applied to the considered systems. The separation mechanism was based on molecular size. Multiple analyses were done to study the capability of considered membranes for the separation of DMSO molecules from... 

APS (3-Aminopropyl) trimethoxysilane) and APhS (p-Aminophenyl) trimethoxysilane) are the most commonly used linkers on a silicon surface. We investigate the surface properties of the structures, including APS or APhS on a silicon substrate. The studied structures consist of APS or APhS linkers with one, two, or three bonds with a substrate, which is a thin layer of Si with crystal orientation 〈1 0 0〉 or 〈1 1 1〉. Using a first-principles study based on density functional theory (DFT), we investigated the electronic and optical properties of the silicon-linker interface, such as interface states, orbital location, dielectric function, and photon absorption. The effects of linker type, number...