Search for: electrostatic-interactions
Evolution of quantum electronic features with the size of silicon nanoparticles embedded in a SiO2 layer obtained by low energy ion implantation, Article 11th International Autumn Meeting on Gettering and Defect Engineering in Semiconductor Technlogy, GADEST 2005, Giens, 25 September 2005 through 30 September 2005 ; Volume 108-109 , 2005 , Pages 71-76 ; 10120394 (ISSN); 3908451132 (ISBN); 9783908451136 (ISBN) ; Shalchian, M ; BenAssayag, G ; Coffin, H ; Bonafos, C ; Dumas, C ; Atarodi, S. M ; Claverie, A ; Sharif University of Technology
Trans Tech Publications Ltd 2005
In this paper, we have studied the evolution of quantum electronic features with the size of silicon nanoparticles embedded in an ultra-thin SiO 2 layer. These nanoparticles were synthesized by ultralow energy (1 KeV) ion implantation and annealing. Their size was modified using the effect of annealing under slightly oxidizing ambient (N2+O2). Material characterization techniques including transmission electron microscopy (TEM) Fresnel imaging and spatially resolved electron energy loss spectroscopy (EELS) have been used to evaluate the effects of oxidation on structural characteristics of nanocrystal layer. Electrical transport characteristics have been measured on few (less than two...
Synthesis and Investigation of Physical Properties of PVDF/Graphene Nanostructured Membranes for Molecular Sieving, M.Sc. Thesis Sharif University of Technology ; Esfandiar, Ali
Poly vinylidene fluoride (PVDF) as a fluorine polymer with acceptable thermal, chemical and physical property attractive create attention in membrane technology for water treatment application. However, with differential surface free energy between PVDF and water (∆G_s=30 mJ/m^2) PVDF polymer is divided as a hydrophobic materials, that is one of the basic problem for PVDF polymer. Due to its hydrophobicity the water molecules repulsion away from hydrophobic PVDF membrane surface as a spontaneous process with an entropy increasing and therefore pollutant molecules with hydrophobic functional group have tendency to adsorb onto membrane surface and dominate the boundary layer. In recent years...
The effects of oxidation conditions on structural and electrical properties of silicon nanoparticles obtained by ultra-low-energy ion implantation, Article Nanotechnology ; Volume 16, Issue 12 , 2005 , Pages 2987-2992 ; 09574484 (ISSN) ; Shalchian, M ; Ben Assayag, G ; Coffin, H ; Bonafos, C ; Schamm, S ; Atarodi, S. M ; Claverie, A ; Sharif University of Technology
In this paper, we have studied the effect of annealing under slightly oxidizing ambient (N2+O2) on the structural and electrical characteristics of a limited number of silicon nanoparticles embedded in an ultra-thin SiO2 layer. These nanoparticles were synthesized by ultra-low-energy (1 keV) ion implantation and annealing. Specific experimental methods have been used to characterize the ncs populations. They include transmission electron microscopy (TEM) Fresnel imaging for evaluating the distances and widths of interest and spatially resolved electron energy loss spectroscopy (EELS) using the spectrum-imaging mode of a scanning transmission electron microscope (STEM) to measure the size...
Spectrophotometric determination of glutathione and cysteine based on aggregation of colloidal gold nanoparticles, Article Scientia Iranica ; Volume 19, Issue 3 , June , 2012 , Pages 958-963 ; 10263098 (ISSN) ; Seyedhosseini, E ; Robatjazi, H ; Sharif University of Technology
We report herein the development of a highly sensitive colorimetric method for the determination of cysteine and glutathione, based on aggregation of the citrate capped gold nanoparticles (Au NPs). This was exploited from high affinity of low-molecular-weight aminothiols towards the Au NPs surface, which could induce displacement of the citrate shell by the thiolate shell of target molecules, resulting in aggregation of the NPs through intermolecular electrostatic interaction or hydrogen-bonding. As a result of aggregation, which can be affected by the ionic strength, pH and concentration of Au NPs, the plasmon band at around 521 nm decreases gradually, along with formation of a new red...
Effect of side by side interactions on the thermodynamic properties of adsorbed CO molecules on the Ni(111) surface: A cluster model study, Article Molecular Physics ; Volume 108, Issue 10 , 2010 , Pages 1397-1412 ; 00268976 (ISSN) ; Parsafar, G ; Sharif University of Technology
The effect of electrostatic interactions on vibrational frequencies and thermodynamic properties of CO adsorbate on the Ni(111) surface is calculated by taking the first and second nearest-neighbour interactions into account. In order to obtain reasonable results, the cluster model of various surface adsorption sites with CO adsorbate is partially optimized, using Density Functional Theory and also the MP2 method for the hcp site. Comparison between DFT and MP2 results shows that DFT results are more reliable for this system. The stretching and bending frequencies of CO adsorbate are calculated using both Partial Hessian Analysis and Cluster-Adsorbate Coupling methods. Stretching and bending...
Mechanistic understanding of the interactions between nano-objects with different surface properties and α-synuclein, Article ACS Nano ; Volume 13, Issue 3 , 2019 , Pages 3243-3256 ; 19360851 (ISSN) ; Hosseini, A ; Adeli, M ; Ejtehadi, M. R ; Christiansen, G ; Sahin, C ; Tu, Z ; Tavakol, M ; Dilmaghani Marand, A ; Nabipour, I ; Farzadfar, F ; Otzen, D. E ; Mahmoudi, M ; Hajipour, M. J ; Sharif University of Technology
American Chemical Society 2019
Aggregation of the natively unfolded protein α-synuclein (α-syn) is key to the development of Parkinson's disease (PD). Some nanoparticles (NPs) can inhibit this process and in turn be used for treatment of PD. Using simulation strategies, we show here that α-syn self-assembly is electrostatically driven. Dimerization by head-to-head monomer contact is triggered by dipole-dipole interactions and subsequently stabilized by van der Waals interactions and hydrogen bonds. Therefore, we hypothesized that charged nano-objects could interfere with this process and thus prevent α-syn fibrillation. In our simulations, positively and negatively charged graphene sheets or superparamagnetic iron oxide...
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
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...
A colorimetric sensor array for detection and discrimination of biothiols based on aggregation of gold nanoparticles, Article Analytica Chimica Acta ; Volume 882 , July , 2015 , Pages 58-67 ; 00032670 (ISSN) ; Hormozi-Nezhad, M.R ; Mahmoudi, M ; Sharif University of Technology
Developments of sensitive, rapid, and cheap systems for identification of a wide range of biomolecules have been recognized as a critical need in the biology field. Here, we introduce a simple colorimetric sensor array for detection of biological thiols, based on aggregation of three types of surface engineered gold nanoparticles (AuNPs). The low-molecular-weight biological thiols show high affinity to the surface of AuNPs; this causes replacement of AuNPs' shells with thiol containing target molecules leading to the aggregation of the AuNPs through intermolecular electrostatic interaction or hydrogen-bonding. As a result of the predetermined aggregation, color and UV-vis spectra of AuNPs...