Sharif Digital Repository

Designing efficient membranes for desalination to help reduce the water shortage crisis has been the subject of various studies. In this study, first, CuAl LDH nanosheets were prepared and the surface of some thin-film composite (TFC) membranes was modified by them. Afterward, the novel heterostructure nanocomposite consisting of CuAl LDH and WS2 nanosheets was synthesized by hydrothermal method, and a new kind of thin-film nanocomposite (TFN) membranes were made using them. All the obtained membranes performance was studied in the forward osmosis (FO) process. The effects of the prepared compounds on the morphology, chemical structure, hydrophilicity, and topology of the polyamide (PA)... 

Carbon nanomaterials (CNMs) have recently attracted much attention in biomedical applications. The size of these nanoparticles is in the range of 1 nm-1 μm, which is comparable to the sizes in biological environments such as protein, DNA, and the size of biological barriers like ion channels. This favorable size has made CNMs suitable nanocarriers for loading and delivering drugs to specific targets inside the body. In addition, some CNMs have unique optical properties that are suitable for biomedical applications such as imaging and photothermal therapy (PTT). However, despite the quick advancements in nanotechnology and biomaterials, it is still difficult to deliver chemotherapeutic agents... 

The fabrication of some new high-performance WS2-Cys-MOF-incorporated thin-film nanocomposite (TFN) forward osmosis (FO) membranes for use in desalination applications is reported. Herein, WS2-Cys-MOF nanosheets are synthesized through UiO-66-(CO2H)2 grafting on WS2-Cys and integrated into the PA selective layer of TFN membranes. The nanofillers content in the MPD aqueous solution was varied from 0 to 0.25 wt% to acquire the optimal loading and the best FO performance. The presence of polymer-matrix compatible WS2-Cys-MOF in the PA selective layer led to the formation of a defect-free smooth surface with additional channels within this layer, which can boost water flux and fouling resistance... 

We have studied the mechanical properties of a few-layer graphene cantilever (FLGC) using atomic force microscopy (AFM). The mechanical properties of the suspended FLGC over an open hole have been derived from the AFM data. Force displacement curves using the Derjaguin-Müller-Toporov (DMT) and the massless cantilever beam models yield a Young modulus of Ec ∼ 37, Ea ∼ 0.7TPa and a Hamakar constant of ∼ 3 × 10 -18J. The threshold force to shear the FLGC was determined from a breaking force and modeling. In addition, we studied a graphene nanoribbon (GNR), which is a system similar to the FLGC; using density functional theory (DFT). The in-plane Young's modulus for the GNRs were calculated from... 

We report experimental evidence of Cu surface segregation in Ni/Cu system, during deposition of Ni film onto Cu substrate at room temperature and during heat treatment in vacuum. Auger electron spectroscopy (AES) and X-ray photoelectron spectroscopy (XPS) by Tougaard's analysis results show that surface segregation defeats in competition with increase in Ni thickness and terminates when thickness of Ni increase to more than 4 nm. Surface energy and concentration were calculated using contact angle measurements and the results confirm that segregation reduces the surface energy. Surface segregation during heat treatment at 150-220 °C range as a function of time initially shows linear mass... 

Porous poly-silicon (PPS) is a cheaper alternative to single crystal porous silicon and is a favorable choice for making gas sensors. In this study, porous poly-silicon samples were prepared using different HF concentrations and the structural and gas-sensing properties were studied. The topography of the surface was investigated by scanning electron microscopy (SEM) and atomic force microscopy (AFM) techniques. The variation of electrical conductivity of the samples in the presence of dry air-diluted acetone, ethanol and methanol showed that for a constant etching current, the sensitivity was highest for samples prepared in 13% HF solution. The structure of the films in the optimum HF... 

The influence of an externally applied bias on photocatalytic performance of crystallized TiO2/Ti nanotubular electrode formed by anodization in fluoride-based electrolyte were investigated and compared to the behavior of multiporous TiO2 electrode. The photoelectrocatalytic oxidation behavior of methanol over the nanotubular electrode has been studied by measuring photocurrent response, potentiodynamic polarization spectroscopy and using electrochemical impedance spectroscopy (EIS). It was found that the photoelectrocatalytic oxidation and the charge transfer rate constant of reaction on TiO2/Ti nanotubular electrode can significantly be increased by applying electrochemical bias. Moreover,... 

We produced ZnO nanoparticles by high current electrical arc discharge of zinc electrodes in deionized (DI) water. X-ray diffraction (XRD) analysis shows formation of crystalline ZnO phase with hexagonal structure and 14 nm single crystalline domain size. Dynamic light scattering (DLS) result indicates that at 5 A arc current, the size of the particles is about 100 nm and increases by increasing the arc current. Absorption spectroscopy of the samples obtained at different arc currents shows an absorption edge on 370 nm which has a red shift by increasing the arc current. Band gap of the produced ZnO nanoparticles at 5 A arc current corresponds to 3.8 eV which decreases to 3.3 eV by... 

The X-ray photoemission (XPS) measurements of Cu1-xTlxBa2Ca2 Cu3-yZnyO10-δ (y = 0, 2.65) superconductors have been performed and compared. These studies revealed that the charge state of thallium in the Cu0.5Tl0.5Ba2O4-δ charge reservoir layer in Zn doped samples is Tl1+, while it is a mix of Tl1+ and Tl2+ in Zn free samples. The binding energy of Ba atoms in the Zn doped samples is shifted to higher energy, which when considered along with the presence of Tl1+ suggested that it more efficiently directed the carriers to ZnO2 and CuO2 planes. The evidence of improved inter-plane coupling witnessed in X-ray diffraction is also confirmed by XPS measurements of Ca atoms in the Zn doped samples.... 

X-ray photo-emission spectroscopy (XPS) studies of Cu1-xTlxBa2Ca3Cu4 O12-y superconductor thin films have been carried out for understanding the mechanism of superconductivity and to find out the reasons for the increase of zero resistivity critical temperature Tc(R = 0) with post-annealing in a nitrogen atmosphere. It is observed from these studies that reduction of charge state of thallium is a source of doping of carriers to the CuO2 planes. The reduced charge state of thallium (i.e. Tl1+) promotes lower oxygen concentration in the charge reservoir layer, which possibly results in movement of electrons to the conducting CuO2 planes. The higher density of electrons in the CuO2 planes... 

We present a general study on a high performance supercapacitor based on intercalated reduced graphene oxide with carbon black nanoparticles. Graphene oxide sheets were synthesized by oxidation and exfoliation of natural graphite and were reduced using hydroiodic acid in the presence of carbon black nanoparticles. Graphene paper was fabricated by one-step procedure via simultaneous reducing and drying the aqueous solution of mixed carbon black nanoparticles and graphene oxide on a conductive substrate. Transmission electron microscopy confirmed the intercalation of carbon black nanoparticles into reduced graphene oxide sheets, preventing them from restacking during the fabrication of paper.... 

Polyphosphate reduced graphene oxide on Ni foam (PPO-RGO/NF) is synthesized by varying weight ratios of Na5P3O10 (PO): graphene oxide (GO) with a simple, scalable and low cost method through freeze-drying of the PO-GO/NF followed by thermal treatment of the prepared electrodes. The resulting samples are characterized using scanning electron microscopy (SEM), energy dispersive spectroscopy (EDS), transmission electron microscopy (TEM), fourier transform infrared spectroscopy (FT-IR), X-ray diffraction (XRD), X-ray fluorescence spectroscopy (XRF), Brunauer-Emmett-Teller (BET), and raman spectroscopy methods. The results show that the weight ratio of PO:GO, considerably affect the... 

New membrane materials and processes have been extensively developed due to urgent needs for much more economic separation processes. Recently, graphene has been confirmed to be an excellent separation membrane. As there is no support in the obtained three-dimensional (3D) architecture constructed from tubular graphene network, it is possible to take full advantage of the large surface of graphene. In this study 3D graphene aerogels were synthesized by a simple method and modified to adjust hydrophilicity of the samples to achieve high liquid volumetric rate. Modified samples were used for the filtration of the enzymes including amylase, cellulase, lipase and protease. Slightly differently... 

We have investigated segregation of copper at the surface of V 2 O 5 films deposited onto Cu substrate by employing surface analysis techniques. X-ray photoelectron spectroscopy (XPS) and Auger electron spectroscopy (AES) confirmed that the Cu is segregated at the surface and its chemical state is Cu 2 O. According to secondary ion mass spectroscopy (SIMS) and glow discharge spectroscopy (GDS), the Cu concentration inside the deposited V 2 O 5 layer is low. Ultraviolet photoelectron spectroscopy (UPS) and scanning tunneling spectroscopy (STS) revealed the segregation alters the surface local density of states. Surface analysis of deposited samples in ultra high vacuum (UHV) condition... 

ZnO nanostructures were synthesized through arc discharge of zinc electrodes in deionized (DI) water. X-ray diffraction (XRD) analysis of the prepared nanostructures indicates formation of crystalline ZnO of hexagonal lattice structures. Transmission electron microscopy (TEM) images illustrate rod-like as well as semi spherical ZnO nanoparticles with 15-20 nm diameter range, which were formed during the discharge process with 5 A arc current. The average particle size was found to increase with the increasing arc current. X-ray photoelectron spectroscopy (XPS) analysis confirms formation of ZnO at the surface of the nanoparticles. Surface area of the sample prepared at 5 A arc current,... 

Silica aerogel-multi wall carbon nanotube composites were synthesized successfully with a waterglass precursor and an ambient pressure drying method. Pure silica aerogels are so fragile that they cannot be used easily. Carbon nanotubes (MWCNT) were used as reinforcements to strengthen the mechanical properties of pure silica aerogels. Results show that inserting small amounts of MWCNT causes silica aerogels to monolith. By addition of MWCNT, monolith nanocomposites were produced with 800 m2/g surface area and a 140° contact angle. Results show that the silica aerogels and reinforced composites have an excellent adsorption property for the removal of organic pollutants from water. The average... 

An efficient and commercially available method is introduced for preparation of a binder-free electrode for capacitive deionization (CDI) application. An interconnected porous composite consisting of polyphosphate (PPO), graphene (Gr) and multi-walled carbon nanotube (CNT) is fabricated and assembled on a Ni foam substrate to prepare a binder-free electrode (Ni/PPOGrCNT). The resulting electrodes were characterized using various instrumental techniques such as TEM, SEM, EDS, XRD, FT-IR, Raman, XPS and XRF. Characterization results indicated that a mesoporous PPO structure is formed on a 3D assembly of carbon backbone. Accordingly, the 3-D porous structure facilitates the ion diffusion into... 

Novel thin-film nanocomposite (TFN) membranes modified by the MoS2@Zeolite X nanocomposite were made and studied for desalination by the forward osmosis (FO) method. Herein, MoS2@Zeolite X nanocomposite (MoS2@Z) and zeolite X particles are integrated into the polyamide (PA) selective layer of the TFN membranes, separately. The aim of this study is the synthesis of nanocomposites containing hydrophilic zeolite X particles with a modified surface and pore and improvement of their effective properties on desalination and antifouling performance. For this purpose, MoS2 nanosheets with a high hydrophilicity were selected. The existence of polymer-matrix-compatible MoS2@Z inside the PA active... 

We report experimental evidence of Cu surface segregation in Ni/Cu system, during deposition of Ni film onto Cu substrate at room temperature and during heat treatment in vacuum. Auger electron spectroscopy (AES) and X-ray photoelectron spectroscopy (XPS) by Tougaard's analysis results show that surface segregation defeats in competition with increase in Ni thickness and terminates when thickness of Ni increase to more than 4 nm. Surface energy and concentration were calculated using contact angle measurements and the results confirm that segregation reduces the surface energy. Surface segregation during heat treatment at 150–220 °C range as a function of time initially shows linear mass... 

We have fabricated and characterised colloidal silver nanoparticles by the electrical arc discharge method in DI water. Size and optical properties of the silver nanoparticles were studied versus different arc currents. Optical absorption indicates a plasmonic peak at 392 nm for 10 A which increases to 398 nm for 20 A arc current. This reveals that by raising the arc current the size of the nanoparticles increases. Optical absorption of silver nanoparticles after 3 weeks shows precipitation of them in a water medium. The effect of different surfactant and stabilizer concentrations such as cethyl trimethylammonium bromide (CTAB), polyvinyl pyrrolidone (PVP), sodium citrate, sodium dodecyl...