Sharif Digital Repository

In this contribution, spinel MgAl2O4 nanospheres prepared by the combustion method were coupled with thermally-exfoliated g-C3N4 nanosheets (TE-GCN) through an efficient isoelectric point-assisted calcination technique. Physical characteristics of the synthesized nanocomposite were understudied utilizing the XRD, FT-IR, FE-SEM, TEM, BET-BJH, UV–Vis DRS, PL, and EIS analyses. This material was used as a novel nano-photocatalyst for degradation of reactive red 195 (RR195) industrial dye contaminant. Results revealed that, a successful synthesis of a heterojunction between the components of the nanocomposite was achieved. This exhibited an enormously improved electron-hole separation leading to... 

Recently, hybrid graphene–quantum dot systems have attracted increasing attention for the next-generation optoelectronic devices such as ultrafast photo-detectors and solar energy harvesting. In this paper, a novel, one-step, reproducible, and solution-processed method is introduced to prepare hybrid graphene–PbS colloids by employing supercritical ethanol. In the hybrid nanocomposite, PbS quantum dots (~3 nm) are decorated on the reduced graphene oxide (rGO) nanosheets (~1 nm thickness and less than 1 micron lengths). By employing X-ray photoelectron and Raman and infrared spectroscopy techniques, it is shown that the rGO nanosheets are bonded to PbS nanocrystals through carboxylic bonds.... 

The impacts of dopant nanoparticles, graphene nanosheets (GNSs) and cobalt decorated-graphene nanosheets (CoGNSs), were studied in relation to the wettability and rheological behavior in low-Ag lead-free SAC0307 (Sn–0.3Ag–0.7Cu) solder paste. The solidification range of the solders was evaluated using differential scanning calorimetry. Phase identification in the solder bulk and interface of the solder and copper substrate was carried out by X-ray diffraction and energy-dispersive X-ray spectroscopy. Spreading properties and reactive wetting behavior along with the rheological properties of the solders were also studied. Results showed that the addition of both nanoparticles did not... 

In the present work, N-doped hollow carbon nanospheres (N-HCNSs) is prepared by direct carbonization of polyaniline-co-polypyrrole (PACP) hollow spheres without template needing. Two different NiO nanostructures (nanosheets and nanowires) are prepared by forming a shell around the N-HCNSs via simple hydrothermal/calcination processes (NiO-NSs@N-HCNSs and NiO-NWs@N-HCNSs). The morphology and structure of the nanostructures are characterized using field emission scanning electron microscopy (FE-SEM), transmission electron microscope (TEM), Fourier transform infrared spectroscopy (FT-IR), and X-ray diffraction (XRD). The prepared nanocomposites are used as catalysts for the electrocatalytic... 

Herein, the effect of electrodeposition time on the super-capacitive performance of three-dimensional (3D) MnO2/g-C3N4 heterostructured electrodes was investigated. MnO2 nanoparticles were electrodeposited on the g-C3N4 nanosheets drop-casted on the Ni foam substrate. The microstructural analysis, carried out by FE-SEM and TEM, confirmed the homogeneous distribution of MnO2 nanoparticles on g-C3N4 nano-sheet layers. The electrochemical capacitive performances of the MnO2/g-C3N4 electrodes were evaluated by cyclic voltammetry (CV), galvanostatic charge/discharge tests, and electrochemical impedance spectra (EIS). The obtained results suggested that the supercapacitor (SC) performance of all... 

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... 

In this paper, the mechanical properties of graphene nanosheets are evaluated based on the nonlinear modified Morse model. The interatomic interactions including stretching and bending of the covalent bonds between carbon atoms, are replaced by nonlinear extensional and torsional spring-like elements. The finite element method is implemented to analyze the model under different loading conditions and linear characteristics of the graphene structure including the Young's modulus, surface modulus, shear modulus and Poisson's ratio are evaluated for various geometries and chirality where these properties are shown to be size and aspect ratio dependent. It is also found that when the dimensions... 

Although important advances have been acquired in the field of electrocatalysis, the design and fabrication of highly efficient and stable non-noble earth-abundant metal catalysts for the oxygen evolution reaction (OER) and hydrogen evolution reaction (HER) remain a significant challenge. In this study, we have designed a superior bifunctional catalyst for OER and HER in alkaline media based on the Co-Mo-P/Zn-Co-S multicomponent heterostructure. The as-prepared multicomponent heterostructure was successfully obtained via a simple three-step hydrothermal-sulfidation-electrodeposition process consisting of star-like Co-Zn-S covered with Co-Mo-P. The structure and morphology evaluation of the... 

Active edge sites of MoS2 nanosheets exhibit promising futures for hydrogen evolution reaction (HER), comparable with remarkable performances of highly cost platinum. However, 3D structures of MoS2 suffer from a lack of high mobility and unexposed active sites which lower the electrocatalytic activity. In this study, we show that there is a balance between increasing the active sites on the one hand and managing the charge transfer to facilitate the reaction on the other hand, and achieving this balance increases the efficiency of the electrocatalyst tremendously. For this purpose, we directly attached exfoliated MoS2 nanosheets onto carbon cloth (CC) substrate as a 3D network of conductive... 

Active edge sites of MoS2 nanosheets exhibit promising futures for hydrogen evolution reaction (HER), comparable with remarkable performances of highly cost platinum. However, 3D structures of MoS2 suffer from a lack of high mobility and unexposed active sites which lower the electrocatalytic activity. In this study, we show that there is a balance between increasing the active sites on the one hand and managing the charge transfer to facilitate the reaction on the other hand, and achieving this balance increases the efficiency of the electrocatalyst tremendously. For this purpose, we directly attached exfoliated MoS2 nanosheets onto carbon cloth (CC) substrate as a 3D network of conductive... 

A novel ultrasensitive modified electrode was fabricated with a graphene nanosheets and carbon nanospheres (GNS-CNS)-based nanocomposite film as a powerful platform. Pt nanoparticles (PtNPs) were simply electrodeposited onto the GNS-CNS-coated glassy carbon electrode creating a PtNPs/GNS-CNS hybrid nanocomposite modified electrode. Scanning electron microscopy, energy dispersive X-ray spectroscopy and linear sweep voltammetry (LSV) techniques were used for the characterization of the prepared modified electrode. The results of investigation of electrochemical response characteristics of cefepime (CP) revealed a considerable improvement in the oxidation peak current of CP on PtNPs/GNS-CNS/GCE... 

Here in, for the first time, we report a new and simple procedure for preparing reduced graphene oxide/nickel-cobalt double layered hydroxide composite on the nickel foam (Ni-Co LDH/rGO/NF) via a fast and simple two-step electrochemical method including potentiostatic routes in the presence of CTAB as a cationic surfactant. Graphene oxide coated nickel foam prepared by simple immersion method. After that, the prepared electrode reduced electrochemically to obtain rGO/NF electrode. Finally, the rGO/NF electrode was used as cathode for electrodeposition of Ni-Co LDH in the presence of CTAB as cationic surfactant. The prepared electrodes were characterized by field emission scanning electron... 

The present study reports a simple electrochemical approach to the fabrication of a new nanocomposite containing PtPd nanoflowers (NFs) promoted with two-dimensional (2D) nanosheets (NSs) structure cuprous oxide (Cu2O) supported on reduced graphene oxide (rGO) (PtPd-NFs/Cu2O-NSs/rGO). Scanning electron microscopy, X-ray diffraction, Fourier transform infrared spectra, Raman spectroscopy, and energy dispersive X-ray spectroscopy are used for characterization of the PtPd-NPs/Cu2O-NPs/rGO. SEM images showed that vertical-standing arrays of Cu2O with an edge length up to 1 μm and thickness of about 20 nm are electrodeposited on the surface of rGO film. Also, PtPd needle-like NFs with visible and... 

Here in, for the first time, we report a new and simple procedure for preparing reduced graphene oxide/nickel-cobalt double layered hydroxide composite on the nickel foam (Ni-Co LDH/rGO/NF) via a fast and simple two-step electrochemical method including potentiostatic routes in the presence of CTAB as a cationic surfactant. Graphene oxide coated nickel foam prepared by simple immersion method. After that, the prepared electrode reduced electrochemically to obtain rGO/NF electrode. Finally, the rGO/NF electrode was used as cathode for electrodeposition of Ni-Co LDH in the presence of CTAB as cationic surfactant. The prepared electrodes were characterized by field emission scanning electron... 

The planned design of nanocomposites combined with manageable production processes, which can offer controllability over the nanomaterial structure, promises the practical applications of functional nanomaterials. Hollow core-shell nanostructure architectures represent an emerging category of advanced functional nanomaterials, whose benefits derived from their notable properties may be hampered by complicated construction processes, especially in the sensing domain. In this regard, we designed a highly porous three-dimensional array of hierarchical hetero Cu(OH)2@CoNi-LDH core-shell nanotubes via a quick, very simple, green, and highly controllable three-step in situ method; they were... 

Demand increasing for next generation portable and miniaturized electronics has aroused much interest to explore microscale and lightweight energy storage devices. Herein, we demonstrate successful development of flexible wire-shaped micro-supercapacitors (micro-SCs) based on novel CoNi2S4/E-NZP film@Cu wire electrode. The etched Ni-Zn-P (E-NZP) film was synthesized by directly deposition of NZP film on Cu wire, followed by a chemical etching process. Alkaline etching treatment provides a micro- and mesoporous structure with high surface area and facilitates the penetration of electrolyte ions into the electrode matrix. Then, CoNi2S4 nanosheets as electroactive material are electrochemically... 

Evolution of renewable energies in the era of the modernized world has been strongly tied up to the incessant development of high-performance energy storage systems benefiting from both high energy and power densities. In the present work, binder-free positive electrodes are fabricated via a facile electrochemical deposition route in which copper oxide nanorods (CuO NRs) directly grown onto the copper foam (CF) are decorated with bimetallic cobalt-zinc sulfide nanoarrays (Co-Zn-S NAs). The fabricated Co-Zn-S@CuO-CFs represent promising specific capacity of 317.03 C.g−1 at 1.76 A.g−1, along with superior cyclic stability (113% retention after 4500 cycles). Negative electrodes were further... 

PEGylated MoS2 nanoflower (MoS2-NF) and nanosheet (MoS2-NS) are synthesized through a one-pot hydrothermal method as photo absorbing agent (PAA). It is found that employing different thiol precursors result in distinct morphologies. The products are structurally, chemically, and morphologically characterized. Electron microscopy demonstrates the formation of sheet and flower morphologies of MoS2. Fourier transform infrared (FTIR) and thermal gravimetric (TGA) analysis confirm the PEGylation of MoS2 nanostructures. Raman and X-ray photoelectron spectroscopy (XPS) confirm the formation of 1T/2H structure of both samples. MoS2-NS demonstrates higher NIR absorption than MoS2-NF with a mass... 

In this study, we prepared cerium oxide (CeO2) hybridized with reduced graphene oxide (rGO) nanosheets using the hydrothermal method. CeO2 and CeO2/rGO were evaluated as electrode materials for use in supercapacitor applications. The structure and morphology of the synthesized materials were investigated. Cyclic voltammetry tests determined a high specific capacitance of 581 F g−1 for CeO2/rGO at a scan rate of 10 mV s−1 in 2 M KOH. In addition, the CeO2/rGO electrode retained 91 % of its initial capacitance after 5000 consecutive cycles, thereby indicating its excellent electrochemical stability. The excellent stability of CeO2/rGO was due to a synergistic effect between CeO2 and rGO. CeO2... 

According to current researches, graphene oxide (GO) membranes show promising desalination properties due to ease of synthesis, low production cost, and high efficiency. There are several experimental works to study ionic sieving properties of GO membranes. However, it is difficult to characterize atomistic mechanism of water permeation and ion rejection by experimental approaches. On the other hand, there exist a few reports in which the atomistic picture of water permeation across GO membranes is investigated by means of molecular dynamics (MD) simulation. In the present work, in addition to water desalination, the atomic scale mechanism of ion rejection is studied using large scale MD...