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Fractal Analysis of Cosmic Microwave Background Radiation
, Article Houches-Ecole d'Ete de Physique Theorique ; Volume 86, Issue C , 2007 , Pages 552- ; 09248099 (ISSN) ; Sharif University of Technology
2007
Precise Cosmology with Redshift Space Distortion and Calculating Pecular Velocity of SNe type Ia
, M.Sc. Thesis Sharif University of Technology ; Baghram, Shant (Supervisor)
Abstract
The distance measurement is the corner stone of the modern cosmology. They are measured via ”Doppler Effect”, accordingly the distances in cosmology are obtained in red-shift space. Despite the cosmological background expansion, the peculiar velocities due to the local density contrast distort these measurements. One of the main challenges in upcoming cosmological studies is to distinguish the peculiar velocity effect from the background expansion.Supernova Type Ia as standard candles can be think of a crucial observation to address the above problem. In this thesis, we study the effect of cosmological perturbations on distance-redshift relation of the SNIa. The corrective effects are from weak...
Synthesis of S- and N-doped Carbon Quantum Dots
,
M.Sc. Thesis
Sharif University of Technology
;
Madah Hosseini, Hamid Reza
(Supervisor)
Abstract
In recent years, adjustable optical properties, simple and inexpensive synthesis, and excellent biocompatibility of carbon dots have attracted much attention. However, the widespread use of carbon dots in biomedical diagnostics, photoluminescence, and photocatalysis has been limited due to a lack of emission or excitation in the red or near-infrared region. Studies have shown that doping in carbon dots can affect the displacement and increase the light intensity. This study aims to use the engineering methods of optical properties of carbon points by doping heteroatoms and adjusting the surface state to synthesize biocompatible carbon dots with luminescence at long wavelengths with strong...
Investigating Process Factors on Red-shift of Photoluminescence of Carbon Dots
, M.Sc. Thesis Sharif University of Technology ; Madah Hosseini, Hamid Reza (Supervisor)
Abstract
In recent years, studies in luminescent carbon dots are overgrowing, the prominent features of carbon quantum dots include cheap and straightforward synthesis, excellent biocompatibility, and adjustable optical properties. However, the widespread use of carbon dots in biomedical diagnostics, photoluminescence, and photocatalysis has been limited due to a lack of emission and excitation in the red or near-infrared region.. However, the widespread use of carbon dots in biomedical diagnostics, photoluminescence, and photocatalysis has been limited due to a lack of emission and excitation in the red or near-infrared region. This research tried to produce carbon dots with redshift in emission...
Frequency Shift by Binary Microlensing System
, M.Sc. Thesis Sharif University of Technology ; Rahvar, Sohrab (Supervisor)
Abstract
Gravitational microlensing with the binary lenses are one the tools for detection of exoplanets. Due to the degeneracy nature of the solutions for the observed light curves additional features such as parallax and finite-size effects help to break the degeneracy. Here in this work we introduce the application of frequency shift effect in the microlensing observations where for the single lens, it has been studied in [5] .In this work our purpose is to study the frequency shifts in binary lenses. Therefore, after reviewing the frequency shift in single gravitational lens systems, we will study this phenomenon in binary systems.In binary lenses, which are mainly used to detect extrasolar...
Anderson localization and propagation of electromagnetic waves through disordered media
, Article Waves in Random and Complex Media ; Volume 20, Issue 1 , 2010 , Pages 191-200 ; 17455030 (ISSN) ; Abedpour, N ; Sepehrinia, R ; Niry, M. D ; Reza Rahimi Tabar, M ; Sahimi, M ; Sharif University of Technology
2010
Abstract
We have used the dynamic method to calculate the frequency dependence of the localization length in a disordered medium, using the amplitude change and the redshift of the spectral density of the propagating incident pulse. The frequency dependence of the localization length in an effectively one-dimensional disordered medium is computed in terms of the strength of the disorder. The results obtained with the dynamic method are confirmed by computing the same results using the transfer-matrix method
Evaluation of antibacterial behavior of in situ grown CuO-GO nanocomposites
, Article Materials Today Communications ; Volume 28 , 2021 ; 23524928 (ISSN) ; Fattahi Nafchi Fatahi, R ; Sangpour, P ; Bagheri, M ; Rahimi, T ; Sharif University of Technology
Elsevier Ltd
2021
Abstract
The growth of harmful microorganisms is a severe threat to human life. Nowadays, it is necessary to prepare antimicrobials materials with high biocompatibility properties. Hence, the use of nanomaterials and their nanocomposites has been proposed as a suitable way to obtain safe and potent antibacterial materials. Recently, several studies have been conducted on the antibacterial properties of metal oxide and graphene oxide (GO) nanomaterials individually. This study investigated the synergistic effect of GO and copper oxide (CuO) as a nanocomposite. CuO-GO nanocomposite containing 5%, 15%, 25%, 50%, and 75% of GO were synthesized to study antibacterial properties. X-ray diffraction (XRD)...
Anderson Localization of Electromagnetic Waves
, Ph.D. Dissertation Sharif University of Technology ; Rahimi Tabar, Mohammad Reza (Supervisor)
Abstract
The electrons scatter by the impurities during propagation through the media and become localized by increasing the impurities. So the metal insulator transition occurs. This phenomenon was first proposed by W. Anderson and is known as Anderson Localization. In this thesis the Anderson localization of electromagnetic waves is investigated. The disordered media with random dielectric constant is studied by considering Maxwell’s equations. There are different numerical methods to study this phenomenon such as transfer matrix method and level statistics we have used in this thesis. In three dimension, different scaling behavior shows the phase transition from localized states to extended states...
Comparison of different strategies for the assembly of gold colloids onto Fe3O4@SiO2 nanocomposite particles
, Article Physica E: Low-Dimensional Systems and Nanostructures ; Volume 49 , 2013 , Pages 30-38 ; 13869477 (ISSN) ; Yaghmaei, S ; Roostaazad, R ; Arpanaei, A ; Sharif University of Technology
2013
Abstract
Three strategies were employed for the assembly of gold nanoparticles on silica-coated magnetite particles (SCMPs). In strategy I, citrate-coated gold nanoparticles were attached on the surface of amine-SCMPs. In strategy II, amine-SCMPs were coated with carboxylated gold nanoparticles via amide bond formation. In strategy III, the thiol-SCMPs surface was coated with gold nanoparticles. Among the above examined strategies, coating amine-SCMPs with gold nanoparticles via strategy I resulted in a better coverage and stronger intensity of absorption bands. Furthermore, results obtained through strategy I showed that decreasing the pH of the solution from 7 to 3 leads to a further red-shift of...
Micro arc oxidation of nano-crystalline Ag-doped TiO2 semiconductors
, Article Materials Letters ; Volume 65, Issue 5 , March , 2011 , Pages 840-842 ; 0167577X (ISSN) ; Aminzare, M ; Molaei, R ; Sadrnezhaad, S. K ; Sharif University of Technology
2011
Abstract
Simple synthesis of silver doped TiO2 nanostructured layers by micro arc oxidation process is reported for the first time. The layers consisted of anatase and rutile phases whose characteristic XRD-peaks shifted toward lower diffraction angles when compared to the pure micro arc oxidized TiO 2 layers. Silver-doping was confirmed by XPS technique. The anatase phase crystalline size was determined as 27.6 and 21.8 nm for the layers grown under the voltages of 350 and 500 V. Employing a UV-Vis spectrophotometer, a red shift in the absorption edge of the layers was observed when silver was incorporated into the titania lattice
Influence of scalar-relativistic and spin-orbit terms on the plasmonic properties of pure and silver-doped gold chains
, Article Journal of Physical Chemistry C ; Volume 123, Issue 14 , 2019 , Pages 9331-9342 ; 19327447 (ISSN) ; Asadi Aghbolaghi, N ; Jamshidi, Z ; Sharif University of Technology
American Chemical Society
2019
Abstract
The unique plasmonic character of silver and gold nanoparticles has a wide range of applications, and tailoring this property by changing electronic and geometric structures has received a great deal of attention. Herein, we study the role of the quantum properties in controlling the plasmonic excitations of gold and silver atomic chains and rods. The influence of relativistic effects, scalar as well as spin-orbit, on the intensity and energy of plasmonic excitations is investigated. The intensity quenching and the red shift of energy in the presence of relativistic effects are introduced via the appearance of d orbitals directly in optical excitations in addition to the screening of...
Fast nuclear spin relaxation rates in tilted cone Weyl semimetals: Redshift factors from Korringa relation
, Article Journal of Physics Condensed Matter ; Volume 33, Issue 21 , 2021 ; 09538984 (ISSN) ; Faraei, Z ; Jafari, S. A ; Sharif University of Technology
IOP Publishing Ltd
2021
Abstract
Spin lattice relaxation rate is investigated for 3D tilted cone Weyl semimetals (TCWSMs). The nuclear spin relaxation rate is presented as a function of temperature and tilt parameter. We find that the relaxation rate behaves as (1-ζ2)-α with α ≈ 9 where 0 ζ < 1 is the tilt parameter. We demonstrate that such a strong enhancement for ζ ≲ 1 that gives rise to very fast relaxation rates, is contributed by a new hyperfine interactions arising from the tilt itself. This can be attributed to the combination of anisotropy of the Fermi surface and an additional part related to the structure of the spacetime: extracting an effective density of states (DOS) ρ from the Korringa relation, we show that...
Evaluation of antibacterial behavior of in situ grown CuO-GO nanocomposites
, Article Materials Today Communications ; Volume 28 , 2021 ; 23524928 (ISSN) ; Fattahi Nafchi Fatahi, R ; Sangpour, P ; Bagheri, M ; Rahimi, T ; Sharif University of Technology
Elsevier Ltd
2021
Abstract
The growth of harmful microorganisms is a severe threat to human life. Nowadays, it is necessary to prepare antimicrobials materials with high biocompatibility properties. Hence, the use of nanomaterials and their nanocomposites has been proposed as a suitable way to obtain safe and potent antibacterial materials. Recently, several studies have been conducted on the antibacterial properties of metal oxide and graphene oxide (GO) nanomaterials individually. This study investigated the synergistic effect of GO and copper oxide (CuO) as a nanocomposite. CuO-GO nanocomposite containing 5%, 15%, 25%, 50%, and 75% of GO were synthesized to study antibacterial properties. X-ray diffraction (XRD)...
Exploitation of n-gene of sars-cov-2 to develop a new rapid assay by ASOs@AuNPs
, Article Analytical Chemistry ; Volume 94, Issue 39 , 2022 , Pages 13616-13622 ; 00032700 (ISSN) ; Samadikhah, H. R ; Hosseinkhani, S ; Sharif University of Technology
American Chemical Society
2022
Abstract
A naked-eye (equipment-free), label-free (cost-effective), and RNA extraction-free (to speed up) method for SARS-CoV-2 (as a case study of RNA viruses) detection is developed. Here, the DNA is being used as a template for in situ formation of anisotropic gold nanoparticles (AuNPs) without any chemical modification or DNA labeling. In this study, synthesized AuNPs for the direct detection of N-gene (nucleocapsid phosphoprotein) of SARS-CoV-2 are exploited. To this aim, antisense oligonucleotides (ASOs) with an extra poly guanine tail (G12) were designed. Thus, in the presence of its viral target RNA gene and ASOs@AuNPs-RNA hybridization, there was a red shift in its localized surface plasmon...
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
2012
Abstract
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...
Adsorption and solar light activity of transition-metal doped TiO 2 nanoparticles as semiconductor photocatalyst
, Article Journal of Materials Science: Materials in Electronics ; Volume 23, Issue 3 , 2012 , Pages 659-667 ; 09574522 (ISSN) ; Simchi, A ; Jafari, T ; Sharif University of Technology
Abstract
There is an eminent interest to improve the photoactivity of TiO 2 nanostructures via doping with midband gap donors or acceptors to achieve a high solar absorption. In the present work, Cr- and V-doped TiO 2 nanoparticles were prepared via a facile chemical vapor synthesis method. The effect of the transition metals (TM) on the solar light activity of the semiconductor nanoparticles as photocatalyst was examined by degradation of methylene blue and acid red 27. Induced coupled plasma and X-ray photoelectron spectroscopy analyses indicated high efficiency of the doping process in the hot wall reactor without surface covering of the TiO 2 nanoparticles by the dopants. Diffuse reflectance...
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...
Geometrical optimization for silver nanowire mesh as a flexible transparent conductive electrode
, Article Applied Optics ; Volume 59, Issue 10 , 2020 , Pages 3073-3080 ; Mahdavi, S. M ; Sadrnezhaad, S. K ; Sharif University of Technology
OSA - The Optical Society
2020
Abstract
We report the effect of the geometric parameters on transparency and conductivity in a metallic nanowire mesh as a transparent electrode. Today, indium tin oxide and fluorine-doped tin oxide are used as the transparent electrode for displays and solar cells. Still, there is a definite need for their replacement due to drawbacks such as brittleness, scarcity, and adverse environmental effects. Metallic nanowire mesh is likely the best replacement option, but the main issue is how to find the optimal structure and how to get the best performance. Since the interaction of light with nanowire mesh is complicated, there is no straightforward rule with a simple analytical solution. We developed a...
When photoluminescence, electroluminescence, and open-circuit voltage diverge-light soaking and halide segregation in perovskite solar cells
, Article Journal of Materials Chemistry A ; Volume 9, Issue 24 , 2021 , Pages 13967-13978 ; 20507488 (ISSN) ; Yang, B ; Kim, Y ; Mohammadpour, R ; Taghavinia, N ; Hagfeldt, A ; Tress, W ; Sharif University of Technology
Royal Society of Chemistry
2021
Abstract
Perovskite solar cells suffer from various instabilities on all time scales. Some of them are driven by light, in particular when employing compounds with mixed halides. Such light soaking effects have been observed to result in performance changes of solar-cell devices. They have also been spectroscopically investigated in detail on films, where the formation of a low-gap iodine-rich phase, seen as a red shift of the PL, has been found to be responsible for a reduced open-circuit voltage. However, studies synchronously examining device performance and its relation to spectroscopy data are scarce. Here, we perform an in operando study, where we investigate the changes of open-circuit voltage...
Development of DESHIMA: A redshift machine based on a superconducting on-chip filterbank
, Article Proceedings of SPIE - The International Society for Optical Engineering ; Volume 8452 , 2012 ; 0277786X (ISSN) ; 9780819491534 (ISBN) ; Baselmans, J. J. A ; Van Der Werf, P. P ; Knoors, B ; Javadzadeh, S. M. H ; Yates, S. J. C ; Thoen, D. J ; Ferrari, L ; Baryshev, A. M ; Lankwarden, Y. J. Y ; De Visser, P. J ; Janssen, R. M. J ; Klapwijk, T. M ; Sharif University of Technology
2012
Abstract
Distant, dusty and extremely luminous galaxies form a key component of the high redshift universe, tracing the period of intense cosmic activity that ultimately gave rise to the present-day universe. These highly luminous galaxies, first detected in the ground-based submillimeter region, are however optically very faint, which hampers identification of the optical counterpart and the measurement of a redshift. We are developing a new direct-detection submm spectrograph DESHIMA. By taking advantage of the rapidly advancing technology of superconducting microresonators, DESHIMA will revolutionize the appearance and capabilities of a submm spectrograph. There will no longer be large grating...