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hydrophobicity
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Preparation and Evaluation of Hydrophobic Pt Catalyst on Alumina and CNT to Produce Heavy Water Isotope
, M.Sc. Thesis Sharif University of Technology ; Kazemeini, Mohammad (Supervisor)
Abstract
Liquide phase catalytic exchange (LPCE) between liquid water and hydrogen is an important reaction for separation of the hydrogen isotope from liquid water. One of the application of this reaction is heavy water production. This method is mainly used hydrophobic catalysts with Pt active metal. The use of hydrophobic catalyst is necessary, because liquid water in the LPCE reaction, resulted in block the catalyst pores and loss of catalyst activity. Design of experiment has been done by using of Design Expert 7.0.0 for determination of number of tests and optimization of Pt weight percent. Alumina and carbon (included graphene, single-walled and multi-walled carbon nanotube) supported 5% wt Pt...
Synthesis and Application of Acidic and Hydrophobic Ionic Liquids in Mannich Reaction and Esterification of Fatty Acids
, M.Sc. Thesis Sharif University of Technology ; Mahmoodi Hashemi, Mohammed (Supervisor)
Abstract
The current study deals with application of a surfactant-like Brønsted acidic ionic liquid (IL) 1-dodecyl-3-methylimidazolium hydrogensulfate (catalys 1) for Mannich reaction at room temperature. The reaction has been efficiently proceeds in water as solvent without using any harmful and expensive organic additives. Our observation has been shown that the reaction is selective for cyclohexanone and no product was observed by using cyclopentanone at room temperature. Density functional theory (DFT) calculations were performed to provide evidence about the nature of reactivity of the cyclohexanone/cyclopentanone. The activity of the catalyst 2 (1-dodecyl-2,3-dimethylimidazolium...
Paclitaxel/β-CD-g-PG inclusion complex: An insight into complexation thermodynamics and guest solubility
, Article Journal of Molecular Liquids ; Volume 208 , August , 2015 , Pages 145-150 ; 01677322 (ISSN) ; Vossoughi, M ; Sharif University of Technology
Elsevier
2015
Abstract
Paclitaxel as one of the most effective anticancer drugs has low aqueous solubility. This inevitably reveals its commercial formulation in Cremophor EL®/ethanol mixture. However, this formulation leads to several severe side effects such as hypersensitivity reactions, neurotoxicity and nephrotoxicity. Inclusion complexation has been introduced as a practical approach in increasing paclitaxel aqueous solubility. To this end, a hybrid nanocarrier system based on hyperbranched polyglycerol and β-cyclodextrin is designed with key components uniquely structured at nanoscale and evaluated according to medical requirements. Paclitaxel is included in the hydrophobic cavity of cyclodextrin as guest...
An unsteady state retention model for fluid desorption from sorbents
, Article Journal of Colloid and Interface Science ; Volume 450 , July , 2015 , Pages 127-134 ; 00219797 (ISSN) ; Sadeghi, H ; Garcia Mayoral, R ; McKay, G ; Sharif University of Technology
Academic Press Inc
2015
Abstract
New studies regarding the sorption of fluids by solids are published every day. In performance testing, after the sorbent has reached saturation, it is usually removed from the sorbate bath and allowed to drain. The loss of liquid from the sorbents with time is of prime importance in the real-world application of sorbents, such as in oil spill response. However, there is currently no equation used for modeling the unsteady state loss of the liquid from the dripping sorbent. Here, an analytical model has been provided for modeling the dynamic loss of liquid from the sorbent in dripping experiments. Data from more than 60 sorbent-sorbate systems has been used to validate the model. The...
Carbon nanotubes part I: Preparation of a novel and versatile drug-delivery vehicle
, Article Expert Opinion on Drug Delivery ; Volume 12, Issue 7 , 2015 , Pages 1071-1087 ; 17425247 (ISSN) ; Solati, N ; Amiri, M ; Mirshekari, H ; Mohamed, E ; Taheri, M ; Hashemkhani, M ; Saeidi, A ; Estiar, M. A ; Kiani, P ; Ghasemi, A ; Basri, S. M. M ; Aref, A. R ; Hamblin, M. R ; Sharif University of Technology
Informa Healthcare
2015
Abstract
Introduction: It is 23 years since carbon allotrope known as carbon nanotubes (CNT) was discovered by Iijima, who described them as "rolled graphite sheets inserted into each other". Since then, CNTs have been studied in nanoelectronic devices. However, CNTs also possess the versatility to act as drug- and gene-delivery vehicles.Areas covered: This review covers the synthesis, purification and functionalization of CNTs. Arc discharge, laser ablation and chemical vapor deposition are the principle synthesis methods. Non-covalent functionalization relies on attachment of biomolecules by coating the CNT with surfactants, synthetic polymers and biopolymers. Covalent functionalization often...
Polymeric ionic liquid nanogel-anchored tungstate anions: A robust catalytic system for oxidation of sulfides to sulfoxides
, Article New Journal of Chemistry ; Volume 39, Issue 2 , 2015 , Pages 1348-1354 ; 11440546 (ISSN) ; Nazari Chamazkoti, M ; Hosseini, S. H ; Sharif University of Technology
Abstract
A new heterogeneous catalytic system was prepared by immobilization of tungstate ions on a cross-linked poly(ionic liquid) nanogel. The solid nanogel was easily synthesized by a surfactant-less method. The resulting catalyst was highly active in selective oxidation of sulfides to sulfoxides by H2O2. The oxidation reactions were successfully performed under solvent-free conditions affording high yields. The catalyst was recycled and reused for several reaction cycles without any significant loss of catalytic activity
Wettability properties of PTFE/ZnO nanorods thin film exhibiting UV-resilient superhydrophobicity
, Article Applied Surface Science ; Volume 341 , 2015 , Pages 92-99 ; 01694332 (ISSN) ; Ebrahimi, M ; Nourmohammadi, A ; Moshfegh, A. Z ; Sharif University of Technology
Elsevier
2015
Abstract
In this research, initially anodization process was used to fabricate ZnO nanorods on Zn substrate and then RF sputtering technique was applied to grow a thin layer of polytetrafluoroethylene (PTFE, Teflon) on the coated ZnO nanorods for producing a superhydrophobic surface. According to scanning electron microscopy (SEM) observations, ZnO nanorods were formed with average diameter and length of about ∼180 nm and 14 μm, respectively. Superhydrophilic property of ZnO nanorods and superhydrophobic property of PTFE/ZnO nanorods was investigated by water contact angle (WCA) measurements. It was found that the contact angle varied with the PTFE deposition time. The highest contact angle...
Investigation of salts behavior at liquid–liquid interfaces
, Article Springer Proceedings in Mathematics and Statistics, 26 August 2013 through 30 August 2013 ; Volume 117 , July , 2015 , Pages 265-270 ; 21941009 (ISSN) ; 9783319123066 (ISBN); 9783319123066 (ISBN) ; Bahramian, A ; Soltani, M ; Pourafshary, P ; Sarikhani, K ; Chen, P ; Ejtehadi, M. R ; Makarov R. N ; Melnik R. V. N ; Kotsireas I. S ; Shodiev H ; Cojocaru M. G ; Cojocaru M. G ; Makarov R. N ; Melnik R. V. N ; Kotsireas I. S ; Shodiev H ; Sharif University of Technology
Springer New York LLC
2015
Abstract
We have used molecular dynamics simulation to investigate hydrophilic– hydrophobic interfaces between calcium chloride (CaCl2) aqueous solutions and normal hexane. The results demonstrate the increasing impact of salt concentration on the liquid–liquid interfacial tension, hence, negative adsorption of CaCl2 according to Gibbs adsorption isotherm. Moreover, we calculated the density profiles of hexane, water, and the counter ions. The results reveal an electrical double layer near the interface and the less affinity of calcium cations toward the interface than that of chloride anions. Orientation of water molecules at the studied concentrations may result in developing a positively charged...
Synthesis and Investigation on the Properties of Silica-Graphene Oxide Nanocomposite Coating
, M.Sc. Thesis Sharif University of Technology ; Dolati, Abolghasem (Supervisor)
Abstract
The investigations on hydrophobic surfaces have attracted lots of intrests in science and technology. Silica sols have been used extensively in the area of producing hydrophobic coatings. On the other hand, carbon-based materials have attracted of a great deal of scientific interest in recent years. The purpose of this research is synthesis and investigation on the properties of Silica- Graphene Oxide nanocomposite coating.Graphene Oxide synthesized by using Hummer’s method. Silica nanoparticles were prepared using sol-gel process and tetraethylorthosilicate (TEOS) as precursor. The surface hydroxyl groups of silica nanoparticles are replaced with Methyl groups by treatment with...
Roles of inorganic oxide nanoparticles on extraction efficiency of electrospun polyethylene terephthalate nanocomposite as an unbreakable fiber coating
, Article Journal of Chromatography A ; Volume 1375 , 2015 , Pages 8-16 ; 00219673 (ISSN) ; Roostaie, A ; Sharif University of Technology
Elsevier
2015
Abstract
In the present work, the roles of inorganic oxide nanoparticles on the extraction efficiency of polyethylene terephthalate-based nanocomposites were extensively studied. Four fiber coatings based on polyethylene terephthalate nanocomposites containing different types of nanoparticles along with a pristine polyethylene terephthalate polymer were conveniently electrospun on stainless steel wires. The applicability of new fiber coatings were examined by headspace-solid phase microextraction of some environmentally important volatile organic compound such as benzene, toluene, ethylbenzene and xylene (BTEX), as model compounds, from aqueous samples. Subsequently, the extracted analytes were...
Observation of a crossover in kinetic aggregation of Palladium colloids
, Article Applied Surface Science ; Volume 353 , 2015 , Pages 1143-1149 ; 01694332 (ISSN) ; Ranjbar, M ; Rouhani, S ; Sharif University of Technology
Elsevier
2015
Abstract
We use field emission scanning electron microscope (FE-SEM) to investigate the growth of palladium colloids over the surface of thin films of WO3 /glass. The film is prepared by Pulsed Laser Deposition (PLD) at different temperatures. A PdCl2 (aq) droplet is injected on the surface and in the presence of steam hydrogen the droplet is dried through a reduction reaction process. Two distinct aggregation regimes of palladium colloids are observed over the substrates. We argue that the change in aggregation dynamics emerges when the measured water drop Contact Angel (CA) for the WO3 /glass thin films passes a certain threshold value, namely CA ≈ 46°, where a...
Preparation of ethylene vinyl acetate copolymer/graphene oxide nanocomposite films via solution casting method and determination of the mechanical properties
, Article Polymer - Plastics Technology and Engineering ; Volume 54, Issue 2 , Jan , 2015 , Pages 218-222 ; 03602559 (ISSN) ; Sedaghat, S ; Ramazani S. A, A ; Baniasadi, H ; Sharif University of Technology
Taylor and Francis Inc
2015
Abstract
Ethylene vinyl acetate/graphene oxide (EVA/GO) nanocomposite films were prepared via solution casting method. The morphological studies investigated using SEM and XRD methods and the results confirmed the formation of likely exfoliation structures and good interaction between matrix and fillers. The results of permeability measurements showed that films have good resistance against oxygen. Mechanical measurements revealed that Young’s modulus and tensile strength of EVA have improved with introducing GO because of proper dispersion of GO into matrix and good interaction between them; however, elongation at break decreased due to formation of strong and rigid polymer/filler network preventing...
Molecular dynamics simulation and MM-PBSA calculations of sickle cell hemoglobin in dimer form with Val, Trp, or Phe at the lateral contact
, Article Journal of Physical Organic Chemistry ; Volume 23, Issue 9 , March , 2010 , Pages 866-877 ; 08943230 (ISSN) ; Akbarzadeh, H ; Parsafar, G. A ; Sharif University of Technology
Abstract
As the delay time and hence nuclei formation play a crucial role in the pathophysiology of sickle cell disease, MD simulation and molecular mechanics-Poisson-Boltzmann surface area (MM-PBSA) calculations have been performed on three systems of hemoglobin; namely dimer of hemoglobin with valine (Hb S), tryptophan (Hbβ6W), and phenylalanine (Hbβ6F) at β6 position. The structural changes due to these aromatic substitutions are investigated. It is shown that β subunits have significant impact on the differences between a dimer and other crystal structures. Transition from a dimer to polymer for Hb S system affects the donor molecule more than that of the acceptor. In the case of donor and...
Synthesis and characterization of alumina flakes/polymer composites
, Article Journal of Applied Polymer Science ; Volume 115, Issue 6 , 2010 , Pages 3716-3720 ; 00218995 (ISSN) ; Iraji Zad, A ; Jafar Tafreshi, M ; Salartayefeh, S ; Sharif University of Technology
Abstract
Alumina flakes were prepared by solution combustion method and milled to provide powder. XRD and SEM data exhibited microsized flakes with 100 nm thickness and nanosized grains. Then the powders were dispersed in polystyrene (PS) and poly methyl methacrylate (PMMA) matrixes and thin sheets of composites were produced by solution method. Mechanical properties of the composites were characterized using tensile test and their fracture surfaces, elemental composition and hydrophobic property were tested by SEM, EDX and contact angle techniques, respectively. The results exhibited better mechanical properties compared to pure polymer samples i.e. the elastic modulus in PMMA and PS composites,...
Lipid membranes with transmembrane proteins in shear flow
, Article Journal of Chemical Physics ; Volume 132, Issue 2 , 2010 ; 00219606 (ISSN) ; Noguchi, H ; Gompper, G ; Sharif University of Technology
Abstract
The effects of embedded proteins on the dynamical properties of lipid bilayer membranes are studied in shear flow. Coarse-grained molecular simulations are employed, in which lipids are modeled as short polymers consisting of hydrophilic head groups and hydrophobic tail monomers; similarly, transmembrane proteins are modeled as connected hydrophobic double- or triple-chain molecules with hydrophilic groups at both ends. In thermal equilibrium, rigid proteinlike molecules aggregate in a membrane of flexible lipids, while flexible proteins do not aggregate. In shear flow parallel to the membrane, the monolayers of lipid bilayer slide over each other. The presence of transmembrane proteins...
Experimental Investigation of Water and Oil Based Colloidal Gas Aphron Drilling Fluid Performance Containing Nanoparticles in Formation Damage Reduction
, M.Sc. Thesis Sharif University of Technology ; Ghazanfari, Mohammad Hossein (Supervisor) ; Rashtchian, Davood (Supervisor)
Abstract
In recent years, utilizing the colloidal gas aphron (CGA) drilling fluids is getting more and more commonplace due to their little formation damage and filtration loss. This study tries to investigate the effect of presence of nanoparticles and their type (hydrophobicity) on stability and performance of water and oil based CGA drilling fluids. This is done through analyzing stability, filtration, rheology, and pore blockage tests. Water and oil based CGA drilling fluids consisted of stabilizer, surfactant, and nanoparticles are generated and through examining of the effects of polymer, surfactant, and nanoparticle concentrations, the optimum formulation is obtained. High pressure-high...
Silane functionalization of nanodiamond for polymer nanocomposites-effect of degree of silanization
, Article Colloids and Surfaces A: Physicochemical and Engineering Aspects ; Volume 506 , 2016 , Pages 254-263 ; 09277757 (ISSN) ; Shojaei, A ; Sharif University of Technology
Elsevier B.V
2016
Abstract
The silanization of nanodiamond (ND) was successfully carried out by using the esterification reaction of hydrolyzed vinyltrimethoxysilane (VTS) in alcoholic solution. The surface carboxylic group of ND was first enhanced by thermal oxidation to increase the degree of esterification reaction. The extent of silane functionalization of ND was controlled by varying the weight ratio of VTS and oxidized ND (oxND), from 2:1 to 10:1 (w/w) in the functionalization reaction medium. Fourier transform infrared spectroscopy (FTIR) and thermogravimetric analysis (TGA) revealed that the highest degree of silanization occurred at VTS/oxND of 5:1 (w/w), while more silane concentrations resulted in...
Rigidity of transmembrane proteins determines their cluster shape
, Article Physical Review E - Statistical, Nonlinear, and Soft Matter Physics ; Volume 93, Issue 1 , 2016 ; 15393755 (ISSN) ; Khoshnood, A ; Jalali, M. A ; Sharif University of Technology
American Physical Society
Abstract
Protein aggregation in cell membrane is vital for the majority of biological functions. Recent experimental results suggest that transmembrane domains of proteins such as α-helices and β-sheets have different structural rigidities. We use molecular dynamics simulation of a coarse-grained model of protein-embedded lipid membranes to investigate the mechanisms of protein clustering. For a variety of protein concentrations, our simulations under thermal equilibrium conditions reveal that the structural rigidity of transmembrane domains dramatically affects interactions and changes the shape of the cluster. We have observed stable large aggregates even in the absence of hydrophobic mismatch,...
Electrospun superhydrophobic polystyrene hollow fiber as a probe for liquid–liquid microextraction with gas chromatography-mass spectrometry
, Article Journal of Separation Science ; Volume 39, Issue 19 , 2016 , Pages 3782-3788 ; 16159306 (ISSN) ; Baktash, M. Y ; Jahandar, K ; Sharif University of Technology
Wiley-VCH Verlag
2016
Abstract
A superhydrophobic polystyrene hollow fiber was electrospun around a copper spring collector. This approach led to the construction of a hollow fiber membrane, and the copper spring acted as a scaffold. The characteristic properties of the hollow fiber were studied by scanning electron microscopy. The membrane was used as a probe to transfer the extracting solvent from aquatic media to a gas chromatograph. After performing the liquid–liquid microextraction procedure on 10 mL of water sample by octanol, the whole solution was passed through the prepared polystyrene hollow fiber. Propanol, containing 2 mg/L lindane as the internal standard, was used for desorption and an aliquot of 2 μL of the...
Facile synthesis of cauliflower-like hydrophobically modified polyacrylamide nanospheres by aerosol-photopolymerization
, Article European Polymer Journal ; Volume 83 , 2016 , Pages 323-336 ; 00143057 (ISSN) ; Ramazani, S. A. A ; Ahadian, M. M ; Tamsilian, Y ; Weber, A. P ; Sharif University of Technology
Elsevier Ltd
2016
Abstract
Amphiphilic copolymers consist of hydrophilic and hydrophobic monomer units have attracted great technological attention recently, owing to their unique properties and their ability to stabilize various interfaces in aqueous systems. This paper presents a novel and facile approach to produce spherical polyacrylamide, polystyrene and hydrophobically modified polyacrylamide (HM-PAM), as one of the most important type of amphiphilic copolymers, using a continuous aerosol-photopolymerization for the first time. To this end, the monomer droplets were generated by an atomizer, then photopolymerization was initiated ‘‘in flight’’ by ultraviolet (UV) irradiation of the aerosol monomer droplets...