Search for: silica
Total 382 records
Oxidation of benzylic methylene compounds to ketones with 4-aminoperoxybenzoic acid supported on silica gel in presence of oxygen or air, Article Monatshefte fur Chemie ; Volume 135, Issue 2 , 2004 , Pages 185-188 ; 00269247 (ISSN) ; Ghazanfari, D ; Karimi Jaberi, Z ; Sharif University of Technology
4-Aminoperoxybenzoic acid supported on silica gel in presence of oxygen or air was found to be a convenient and selective oxidant for the oxidation of benzylic methylene compounds to the corresponding ketones
Efficient and practical protocol for silylation of hydroxyl groups using reusable lithium perchlorate dispread in silica gel under neutral condition, Article Journal of Organometallic Chemistry ; Volume 691, Issue 5 , 2006 , Pages 817-820 ; 0022328X (ISSN) ; Yousefi, R ; Saidi, M. R ; Sharif University of Technology
A very efficient and mild procedure for the trimethylsilylation of a wide variety of alcohols, including primary, allylic, benzylic, secondary, hindered secondary, tertiary, and phenols with hexamethyldisilazane on the surface of silica gel dispersed with LiClO4 in room temperature at few minutes in excellent yields under neutral conditions is reported. This procedure also allows the excellent selectivity under LP-SiO2 system for silylation of alcohols in the presence of amine and phenolic hydroxy groups. © 2005 Elsevier B.V. All rights reserved
Investigation of the applicability of nano silica particles as a thickening additive for polymer solutions applied in EOR processes, Article Energy Sources, Part A: Recovery, Utilization and Environmental Effects ; Vol. 36, Issue. 12 , 2014 , Pages 1315-1324 ; ISSN: 15567036 ; Kharrat, R ; Ghazanfari, M. H ; Sharif University of Technology
In past decades, many attempts have been made to use water-soluble polymers as a mobility control agent to improve sweep efficiency of enhanced oil recovery processes. However, sensitivity of the thickening behavior of these polymers to some harsh conditions, such as high salinity, has cast serious doubt on their applicability in reservoir conditions. By expansion of nanotechnology, scientists discovered that nanoparticles can be utilized as thickening and rheology control agents in many polymer solutions. In this study, hydrophilic fumed silica is added to hydrolyzed polyacrylamide and sulfonated polyacrylamide solutions. The effect of the addition of nano silica on the thickening and...
Investigating the rheological properties of nanofluids of water/hybrid nanostructure of spherical silica/MWCNT, Article Thermochimica Acta ; Volume 578 , 20 February , 2014 , Pages 53-58 ; ISSN: 00406031 ; Rashidi, A ; Soleimanisalim, A. H ; Rashtchian, D ; Sharif University of Technology
Regarding the importance of rheological properties of water based drilling fluids, the effects of silica nanospheres, multiwall carbon nanotubes (MWCNTs) and two types of their hybrid, i.e. H1 (80 wt.% silica nanosphere/20 wt.% MWCNT) and H2 (50 wt.% silica nanosphere/50 wt.% MWCNT) on the viscosity and density of distilled water were investigated. According to the results, viscosity and density of the nanofluids increased with the concentration, while they were reduced by increasing the temperature. At high concentrations, the least increase in the viscosity of distilled water by adding the nanomaterials is related to H2 (8.2% increase at 1.0 wt.%). Likewise, the optimum operating...
Effect of zircon content on chemical and mechanical behavior of silica-based ceramic cores, Article Ceramics International ; Vol. 40, issue. 1 PART A , January , 2014 , p. 1093-1098 ; Faghihi-Sani, M. A ; Nayyeri, M. J ; Mohammadi, M ; Hajfathalian, M ; Sharif University of Technology
In this work, the effect of zircon content on the mechanical and chemical behaviors of injection molded silica-based ceramic cores has been investigated. In order to simulate a casting process condition, the sintered samples at 1220 C were consequently heated up to 1430 C. Three point bending tests were carried out on all the prepared samples. The chemical resistance of the prepared cores was evaluated by leaching of samples in 43% KOH solution at its boiling point. Phase evolution and microstructure were investigated by XRD and SEM, respectively. Results showed that increasing zircon content led to an increase in MOR and decrease in leachability owing to the decrease in content of fused...
Investigation on cristobalite crystallization in silica-based ceramic cores for investment casting, Article Journal of the European Ceramic Society ; Volume 33, Issue 15-16 , 2013 , Pages 3397-3402 ; 09552219 (ISSN) ; Faghihi Sani, M. A ; Alizadeh, H. R ; Sharif University of Technology
In this work, cristobalite crystallization and its effects on mechanical and chemical behaviour of injection moulded silica-based ceramic cores were investigated. In order to simulate casting process condition, the sintered samples at 1220 °C were also heated up to 1430 °C. Flexural strength test was carried out on both sintered and heat treated samples. Chemical resistance of the cores was evaluated by leaching the samples inside 43. wt% KOH solution at its boiling point. Phase evolution and microstructure were investigated by thermal analyses (DTA and DSC), X-ray diffraction (XRD), scanning electron microscopy (SEM) and optical microscopy (OM). Results showed that cristobalite was...
Adsorption isotherms and ideal selectivities of hydrogen sulfide and carbon dioxide over methane for the Si-CHA zeolite: Comparison of carbon dioxide and methane adsorption with the all-silica DD3R zeolite, Article Adsorption ; Volume 19, Issue 5 , 2013 , Pages 1045-1053 ; 09295607 (ISSN) ; Soltanieh, M ; Bozorgzadeh, H ; Mohamadalizadeh, A ; Sharif University of Technology
Adsorption isotherms of H2S, CO2, and CH4 on the Si-CHA zeolite were measured over pressure range of 0-190 kPa and temperatures of 298, 323, and 348 K. Acid gases adsorption isotherms on this type of zeolite are reported for the first time. The isotherms follow a typical Type-I shape according to the Brunauer classification. Both Langmuir and Toth isotherms describe well the adsorption isotherms of methane and acid gases over the experimental conditions tested. At room temperature and pressure of 100 kPa, the amount of CO2 adsorption for Si-CHA zeolite is 29 % greater than that reported elsewhere (van den Bergh et al. J Mem Sci 316:35-45 (2008); Surf Sci Catal 170:1021-1027 (2007)) for the...
Silica-supported DABCO-tribromide: A recoverable reagent for oxidation of alcohols to the corresponding carbonyl compounds, Article Scientia Iranica ; Volume 20, Issue 3 , 2013 , Pages 598-602 ; 10263098 (ISSN) ; Masoud, N ; Foroushani, B. K ; Saryazdi, S ; Ghonouei, N ; Daemi, E ; Sharif University of Technology
In this study, 1,4-diazabicy lo[2.2.2] octane (DABCO) tribromide was immobilized on silica support by using 3-chloro propyl trimethoxy silane to obtain a silica-supported DABCO tribromide reagent. The synthesized reagent was characterized with elemental analysis, FT-IR spectroscopy, and thermo-gravimetric analysis (TGA). This reagent has been applied in the conversion of alcohol to corresponding carbonyl compounds. Alcohol oxidation reactions yield in 52-95%, and the reagent may be recycled five times with further bromine treatment
PEG-co-polyvinyl pyridine coated magnetic mesoporous silica nanoparticles for pH-responsive controlled release of doxorubicin, Article International Journal of Polymeric Materials and Polymeric Biomaterials ; Volume 64, Issue 11 , 2015 , Pages 570-577 ; 00914037 (ISSN) ; Mazaheri Tehrani, Z ; Bennett, C ; Sharif University of Technology
Taylor and Francis Inc 2015
In the present work a pH responsive drug nanocarrier based on magnetic mesoporous silica nanoparticles (MMSN) and polyethylene glycol-co-polyvinyl pyridine (PEG-co-PVP) was prepared. The core-shell nanocarrier was formed due to electrostatic interaction between protonated polyvinyl pyridine and surface modified MMSN with carboxylate groups. This carrier was used for pH-controllable doxorubicin release. The maximum release was occurred at pH 5.5 (pH of endosomes). This carrier was characterized by Fourier transform infrared spectroscopy, thermogravimetric analysis, UV-Vis spectrophotometer, scanning electron microscope, and high-resolution transmission electron microscope techniques. Also the...
A note on the synergistic effect of surfactants and nanoparticles on rising bubble hydrodynamics, Article Chemical Engineering and Processing - Process Intensification ; Volume 155 , 2020 ; Bastani, D ; Lotfi, M ; Sharif University of Technology
Elsevier B.V 2020
Various mixtures of surfactants and nanosilica particles were investigated to assess their influence on rising bubble hydrodynamics. For this purpose, local velocities of rising bubbles were measured experimentally. Also, the effects of concentration of three types of surface-modified silica nanoparticles on density, viscosity, and surface tension of surfactant solutions were determined. Experimental results revealed that the simultaneous presence of nanoparticles and surfactant molecules led to the decrease of local velocities of rising bubbles. The presence of nanoparticles in surfactant solutions leads to a more reduction of bubble local velocity. This could be caused by the formation of...
The stability and surface activity of environmentally responsive surface-modified silica nanoparticles: the importance of hydrophobicity, Article Journal of Dispersion Science and Technology ; Volume 41, Issue 9 , 2020 , Pages 1299-1310 ; Mohammadi, A ; Sharif University of Technology
Taylor and Francis Inc 2020
In this study, the effect of hydrophobicity of environmentally responsive surface-modified silica nanoparticles on the stability and surface activity of the nanoparticles is examined. To this end, n-propyl, n-hexyl, or n-octyl chains and methoxy poly(ethylene glycol) chains at various quantities were coated covalently on the surface of silica nanoparticles to regulate the hydrophobicity of the responsive nanoparticles. Various experimental tools such as stability analysis, interfacial-tension and contact-angle measurements, and emulsion formation were performed to investigate the effect of hydrophobicity. It became evident that the presence of the hydrophobic agents influences considerably...
Processing and Characterization of Fracture Behavior of Hybrid Epoxy Nanocomposite Modified with Polycarbonate, M.Sc. Thesis Sharif University of Technology ; Bagheri, Reza
Epoxy resins have good mechanical and thermal properties, high chemical resistance and low shrinkage during cure but in spite of these good properties,they are brittle and this limits the usage of them. Adding a second, soft or rigid, phase has been always an effective strategy to improve the toughness of epoxy. Rigid phase used in resins are divided into organic and inorganic. The aim of this study is to increase epoxy toughness, maintaining mechanical properties and study effect of silica and polycarbonate on fracture toughness simultaneously. Mechanical properties including yield strength and elastic modulus are evaluated by pressure test. Additionally fracture toughness and three...
3D Stem Cell Culture and Differentiation Using Alginate Hydrogel Scaffolds Incorporated with Silicon-Based Nanoparticles, Ph.D. Dissertation Sharif University of Technology ; Yaghmaei, Soheila ; Arpanaei, Ayyoob ; Dolatshahi Pirouz, Alireza
Bone is one of the most vital parts of the body for almost any functional movement. Due to its many involved diseases, traumas and injuries, bone maintenance and regeneration are of high importance. Engineering and design of complex tissues, with impeccable mimicry of the native ones, are always accounted as the solution to dysfunction of body organs due to aging, various diseases, etc. However, the inability to complete mimicry of the native tissue architecture and cell microenvironment are the main barriers to functional tissue regeneration. In this project, in order to design a suitable scaffold for bone regeneration, hydrogel nanocomposites with polysaccharide basis were developed by...
Febrication of Superhydrophobic Nanocomposites Containing Modified Silica Nanoparticles and Silicone Polymers and Evaluation of Their Application, M.Sc. Thesis Sharif University of Technology ; Pourjavadi, Ali ; Alamolhoda, Ali Asghar
Rehabilitation usually involves physical therapy, occupational therapy and counseling for the patient's morale to help to restore his power and performance. Considering the economic outlook and the costs of rehabilitation methods and due to the increasing prevalence of stroke and the need to recover the patients in a short period, only the use of robotic systems opens the door to the medical community. Since a large rehabilitation robots designed and built and each been used according to their advantages and shortcomings. In this project, the major shortcomings examined and exoskeleton designed on two major features including portability and covering shoulder workspace. Shoulder movement was...
Chitosan based supramolecular polypseudorotaxane as a pH-responsive polymer and their hybridization with mesoporous silica-coated magnetic graphene oxide for triggered anticancer drug delivery, Article Polymer (United Kingdom) ; Volume 76 , October , 2015 , Pages 52-61 ; 00323861 (ISSN) ; Mazaheri Tehrani, Z ; Jokar, S ; Sharif University of Technology
Elsevier Ltd 2015
Chitosan based polyseudorotaxane was designed as a pH-responsive supramolecular polymeric shell around the mesoporous silica-coated magnetic graphene oxide (Fe
3O 4@GO@mSiO 2). It was used for doxorubicin delivery at cancerous tissue in a controlled manner. The core-shell nanocarrier was formed due to electrostatic interaction between chitosan and carboxylated surface of Fe 3O 4@GO@mSiO 2. The maximum release occurred at pH 5.5 (pH of endosomes) because the shell collapsed at this pH. The drug nanocarrier has potential application in tumor therapy due to good pH-sensitive behavior, improved solubility and high colloidal stability in...
synergistic toughening in ternary silica/hollow glass spheres/epoxy nanocomposites, Article Polymer - Plastics Technology and Engineering ; Volume 54, Issue 6 , 2015 , Pages 581-593 ; 03602559 (ISSN) ; Bagheri, R ; Kouchakzadeh, M. A ; Abadyan, M ; Sharif University of Technology
Taylor and Francis Inc 2015
Herein, the fracture toughness of ternary epoxy systems containing nanosilica and hollow glass microspheres (HGMS) is investigated. The experimental measurements reveal synergistic fracture toughness in some hybrid compositions: The incorporation of 10 phr of HGMS and nanosilica alone modify the fracture toughness of epoxy by 39% and 91%, respectively. However, use of 10 phr hybrid modifier can enhance the fracture toughness of the resin up to 120%. Observations reveal different toughening mechanisms for the blends i.e., plastic deformation for silica nanoparticles and crack bifurcation for HGMS. Both of these toughening mechanisms additively contribute to the synergism in ternary epoxies
Curcumin-loaded amine-functionalized mesoporous silica nanoparticles inhibit α-synuclein fibrillation and reduce its cytotoxicity-associated effects, Article Langmuir ; Volume 32, Issue 50 , 2016 , Pages 13394-13402 ; 07437463 (ISSN) ; Morshedi, D ; Yaghmaei, S ; Aliakbari, F ; Rahimi, F ; Arpanaei, A ; Sharif University of Technology
American Chemical Society 2016
This study aimed to develop a drug carrier based on amine-functionalized mesoporous silica nanoparticles (AAS-MSNPs) for a poorly water-soluble drug, curcumin (CUR), and to study its effects on α-synuclein (α-Syn) fibrillation and cytotoxicity. Here, we show that AAS-MSNPs possess high values of loading efficiency and capacity (33.5% and 0.45 mg drug/mg MSNPs, respectively) for CUR. It is also revealed that α-Syn species interact strongly with the CUR-loaded AAS-MSNPs, leading to a significant inhibition of the fibrillation process. Furthermore, these samples reduce the toxic effects of CUR. However, drug-loaded AAS-MSNPs do not affect the cytotoxic properties of the formed fibrils...
Functionalized mesoporous silica-coated magnetic graphene oxide by polyglycerol-g-polycaprolactone with pH-responsive behavior: designed for targeted and controlled doxorubicin delivery, Article Journal of Industrial and Engineering Chemistry ; 2015 ; ISSN: 1226086X ; Tehrani, Z. M ; Jokar, S ; Sharif University of Technology
In the present work a novel multifunctional drug nanocarrier was prepared. Polyglycerol-. g-polycaprolactone was grafted on Mesoporous silica-coated magnetic graphene oxide. Doxorubicin, as anticancer drug, was loaded on this carrier. The in vitro drug release showed the controlled pH responsive behavior. At the endosomal pH (pH 5.5) the amount of drug release enhanced. This nanocarrier would have potential application in the tumor therapy owing to its biodegradability, controlled release and pH responsive behavior
Communication - Co-electrodeposition of Ni/SiO2(CH2)3SH composite: Modified Guglielmi’s model and mechanism of nucleation, Article Journal of the Electrochemical Society ; Volume 164, Issue 13 , 2017 , Pages E472-E474 ; 00134651 (ISSN) ; Rouhollahi, A ; Dolati, A ; Ghahramanifard, F ; Sharif University of Technology
Electrochemical Society Inc 2017
This work studies the influence of surface modification of silica nanoparticles by mercaptopropyl trimethoxysilane on silica weight percent in Ni coating during electrodeposition. Results showed SiO2(CH2)3SH particles were embedded in the Ni coating up to 11%. Also, modified Guglielmi’s model and mechanicsm of nucleation of Ni-SiO2(CH2)3SH composite were studied. © 2017 The Electrochemical Society. All rights reserved
Immobilization of cellulase on non-porous ultrafine silica particles, Article Scientia Iranica ; Volume 14, Issue 4 , 2007 , Pages 379-383 ; 10263098 (ISSN) ; Kazemi, A ; Kheirolomoom, A ; Nejati, S ; Sharif University of Technology
Sharif University of Technology 2007
The immobilization of cellulase onto non-porous ultrafine silica particles was studied. Cellulase was extracted from a Trichoderma reesei culture after partial purification with ammonium sulfate (pH = 5.0), which was then immobilized onto non-porous ultrafine silica particles, with or without the use of glutaraldehyde as a crosslinking agent. Cellulase was immobilized by adsorption onto ultrafine silica particles efficiently, as well as by covalent cross-linking with glutaraldehysde. Increasing the concentration of the free form of enzyme increased the amount of immobilized cellulase. The maximum enzyme immobilization happened at the free enzyme concentration of 0.48 mg/ml. In general, the...