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Surface roughness analysis of hydrophilic SiO2/TiO 2/glass nano bilayers by the level crossing approach
, Article Physica A: Statistical Mechanics and its Applications ; Volume 392, Issue 9 , 2013 , Pages 2175-2181 ; 03784371 (ISSN) ; Reza Rahimi Tabar, M ; Moshfegh, A. Z ; Sharif University of Technology
2013
Abstract
The effect of etching time on the statistical properties of hydrophilic surfaces of SiO2/TiO2/glass nano bilayers has been studied using atomic force microscopy (AFM) and a stochastic approach based on a level crossing analysis. We have created rough surfaces of the hydrophilic SiO 2/TiO2 nano bilayer system by using 26% potassium hydroxide (KOH) solution. Measuring the average apparent contact angle allowed us to assess the degree of hydrophilicity, and the optimum condition was determined to be 10 min etching time. A level crossing analysis based on AFM images provided deeper insight into the microscopic details of the surface topography. With different etching times, it has been shown...
Simulation of the Biomolecule Imaging and Manipulation Via AFM by Molecular Dynamics Method
, M.Sc. Thesis Sharif University of Technology ; Meghdari, Ali (Supervisor) ; Moosavi, Ali (Supervisor)
Abstract
In this thesis we try to find optimized parameters for imaging and manipulation of a biosample with AFM. For this we have prepared a numerous Molecular Dynamics simulation and find some reliable result. So, first we have focused on imaging process in Non contact mode (the less harmful mode). Then we headed into the manipulation process. The main problem about manipulating a biosample is the environment. In imaging section, the process of imaging a biomolecule by AFM is modeled using molecular dynamics simulations. Since the large normal force exerted by the tip on the biosample in contact and tapping modes may damage the sample structure and produce irreversible deformation, the non-contact...
Developing a Molecular Dynamics Simulation Software for Modeling of Nano-Contact Processes (CEDRA Molecular Dynamics Software )
,
M.Sc. Thesis
Sharif University of Technology
;
Meghdari, Ali
(Supervisor)
;
Mahboobi, Hanif
(Supervisor)
Abstract
Molecular Dynamics as a powerful method in the field of Nano-simulation has been widely used in recent years. Different contact processes such as Nano-manipulation, AFM Imaging, and Nano-indentation can be simulated using this method. There have been numerous researches done on calculating techniques of simulation of different phenomena in Nano-technology. Specifically, friction and Nano-indentation which are parts of Nano-contact processes have been simulated by different investigators. However, on some other parts, e.g. Nano-manipulation and AFM Imaging, there are few studies done up to now. Thus, a simulation and computational software seems necessary in this field. The main goal of...
Determination of the Surface Properties and Topography in AFM Using System Dynamics
,
M.Sc. Thesis
Sharif University of Technology
;
Nejat, Hossein
(Supervisor)
Abstract
Nowadays, the atomic force microscopy (AFM) has become a useful laboratory tool with variety of applications. In the traditional imaging technique, usually the amplitude or frequency of AFM tip oscillations is set at a desired value using a feedback control system which is a relatively slow process. In the current research, we propose an estimation approach which uses an adaptive fading extended Kalman filter (augmented with forgetting factor) as a system observer and couples with the system dynamics to determine the sample topography. As a result, in addition to state variables of system dynamic, the sample height as an unknown parameter is estimated with high accuracy in a relatively short...
Effect of chemical substitution on the morphology and optical properties of Bi1-xCaxFeO3 films grown by pulsed-laser deposition
, Article Journal of Materials Science: Materials in Electronics ; Volume 24, Issue 1 , 2013 , Pages 248-252 ; 09574522 (ISSN) ; Mahdavi, S. M ; Nemati, A ; Sharif University of Technology
2013
Abstract
The morphological characteristics as well the optical properties of Ca-doped BiFeO3 films grown by pulsed-laser deposition technique have been investigated. AFM images revealed that calcium has a radical effect on the surface features of BiFeO3 films. By utilizing spectrophotometer, transmission behaviour of the films was investigated. Local IV characteristics of the films disclosed about three orders of magnitude enhancement concerning electrical conductivity through Ca doping. X-ray photoelectron spectroscopy results revealed that Ca can reduce the valence state of iron in the compound
CO gas sensor properties of Cu@CuO core-shell nanoparticles based on localized surface plasmon resonance
, Article Journal of Physical Chemistry C ; Volume 115, Issue 45 , 2011 , Pages 22126-22130 ; 19327447 (ISSN) ; Zahrabi, H ; Saani, M. H ; Vesaghi, M. A ; Sharif University of Technology
2011
Abstract
Hexagonal array of Cu@CuO core-shell nanoparticles (NPs) on the a-C:H thin film was prepared by codeposition of RF-sputtering and RF-PECVD. The trace of hexagonal NPs supperlattice was recognized by AFM image and XRD result. On the basis of localized surface plasmon resonance (LSPR) of core-shell NPs, the prepared array detected a low flow rate of CO gas at room temperature. XPS results indicate that the surface of Cu@CuO core-shell NPs have no chemical reaction with CO molecule. The physical absorption of CO molecule on the surface of Cu@CuO core-shell NPs increases the LSPR absorbance and causes a red shift in LSPR wavelength. These experimental results are in agreement with Mie theory...
Preparation and characterization of nanocrystalline and mesoporous strontium titanate thin films at room temperature
, Article Journal of Coatings Technology Research ; Volume 8, Issue 5 , July , 2011 , Pages 585-593 ; 15470091 (ISSN) ; Fray, D. J ; Sharif University of Technology
2011
Abstract
The low temperature perovskite-type strontium titanate (SrTiO 3) thin films and powders with nanocrystalline and mesoporous structure were prepared by a straightforward particulate sol-gel route. The prepared sol had a narrow particle size distribution with hydrodynamic diameter of about 17 nm. X-ray diffraction (XRD) revealed that the synthesized powders had a perovskite-SrTiO 3 structure with preferable orientation growth along the (1 0 0) direction. TEM images showed that the average crystallite size of the powders annealed in the range 300-800°C was around 8 nm. FE-SEM analysis and AFM images revealed that the deposited thin films had mesoporous and nanocrystalline structure with the...
The effect of Au/Ag ratios on surface composition and optical properties of co-sputtered alloy nanoparticles in Au-Ag:SiO2 thin films
, Article Journal of Alloys and Compounds ; Volume 486, Issue 1-2 , 2009 , Pages 22-28 ; 09258388 (ISSN) ; Akhavan, O ; Zaker Moshfegh, A. R ; Sharif University of Technology
2009
Abstract
Gold-silver alloy nanoparticles with various Au concentrations in sputtered SiO2 thin films were synthesized by using RF reactive magnetron co-sputtering and then heat-treated in reducing Ar + H2 atmosphere at different temperatures. The UV-visible absorption spectra of the bimetallic systems confirmed the formation of alloy nanoparticles. The optical absorption of the Au-Ag alloy nanoparticles exhibited only one plasmon resonance absorption peak located at 450 nm between the absorption bands of pure Au and Ag nanoparticles at 400 and 520 nm, respectively, for the thin films annealed at 800 °C. The maximum absorption wavelength of the surface plasmon band showed a red shift with increasing...