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    Defect study of TiO2 nanorods grown by a hydrothermal method through photoluminescence spectroscopy

    , Article Journal of Luminescence ; Volume 157 , January , 2015 , Pages 235-242 ; 00222313 (ISSN) Rajabi, M ; Shogh, S ; Iraji Zad, A ; Sharif University of Technology
    Elsevier  2015
    Abstract
    This paper describes the photoluminescence study of titanium dioxide (TiO2) nanorods grown by a hydrothermal synthesis method on the surface of fluorine doped tin oxide (FTO) coated glass. The effects of growth conditions including: reaction time, precursor concentration and adding NaCl to hydrothermal solution on the structural and optical properties of productions are examined by using SEM, XRD, TEM and room temperature photoluminescence measurements. Also, the performance of the TiO2 nanorods as a photoanode of dye sensitized solar cells is investigated. The different excitation energies and intensities are chosen to verify the discrete electronic state of radiative recombination centers... 

    Time dependence of the surface plasmon resonance of copper nanorods

    , Article Journal of Physics Condensed Matter ; Volume 19, Issue 44 , 2007 ; 09538984 (ISSN) Azarian, A ; Iraji zad, A ; Dolati, A ; Ghorbani, M ; Sharif University of Technology
    2007
    Abstract
    Copper nanorods have been synthesized by electrodeposition with different lengths in porous polycarbonate (PCT) membranes with a pore diameter of 50nm and a thickness of 4νm. The PCT membranes were dissolved in dichloromethane (CH2Cl2) and the solvent was replaced by methanol solutions. Extinction peaks at 587, 581 and 574nm were observed for the Cu nanorods with aspect ratio R = 6,8 and 10 in methanol, respectively. Polarization of the molecules of the medium around the wires changes the dielectric constant of the medium. Hence, the wavelength of the extinction peaks does not shows good agreement with calculations that were done on basis of Gans' theory with nominal dielectric constant of... 

    Enhanced thermal stability and biocompatibility of gold nanorods by graphene oxide

    , Article Plasmonics ; 2017 , Pages 1-10 ; 15571955 (ISSN) Shirshahi, V ; Hatamie, S ; Tabatabaei, S. N ; Salimi, M ; Saber, R ; Sharif University of Technology
    Abstract
    In the present study, the effect of nanosized graphene oxide layer on thermal stability and biocompatibility of gold nanorods has been examined. The graphene oxide-wrapped gold nanorods were prepared by electrostatic interaction between negatively charged graphene oxide and positively charged nanorods. The resulting nanohybrids were then heated at different time intervals to 95 °C in a water bath to assess the effect of heat on the rods morphology. The structural changes in gold nanorods were monitored via UV-Vis spectroscopy measurements and transmission electron microscopy images. In similar experiments, the graphene oxide used to wrap gold nanorods was reduced by ascorbic acid in a 95 °C... 

    Enhanced thermal stability and biocompatibility of gold nanorods by graphene oxide

    , Article Plasmonics ; Volume 13, Issue 5 , 2018 , Pages 1585-1594 ; 15571955 (ISSN) Shirshahi, V ; Hatamie, S ; Tabatabaei, S. N ; Salimi, M ; Saber, R ; Sharif University of Technology
    Abstract
    In the present study, the effect of nanosized graphene oxide layer on thermal stability and biocompatibility of gold nanorods has been examined. The graphene oxide-wrapped gold nanorods were prepared by electrostatic interaction between negatively charged graphene oxide and positively charged nanorods. The resulting nanohybrids were then heated at different time intervals to 95 °C in a water bath to assess the effect of heat on the rods morphology. The structural changes in gold nanorods were monitored via UV-Vis spectroscopy measurements and transmission electron microscopy images. In similar experiments, the graphene oxide used to wrap gold nanorods was reduced by ascorbic acid in a 95 °C... 

    The UV photodetection enhancement of tailored ZnO nanorods by controlling the aspect ratio

    , Article Surfaces and Interfaces ; Volume 28 , 2022 ; 24680230 (ISSN) Nazari, N. F ; Rajabi, M ; Moshfegh, A. Z ; Sharif University of Technology
    Elsevier B.V  2022
    Abstract
    ZnO Nanorods (NRs) are deposited on glass substrate using the hydrothermal method by applying a strategic growth control to improve their aspect ratios. In this research, the aspect ratio was tuned by tailoring the synthesis parameters, including the seed layer annealing temperature, absence/presence of polyethylenimine (PEI) in the growth solution, and the solution preheating process. The effects of these parameters on the morphology, crystal structure, room temperature photoluminescence properties, and current-voltage characteristics were examined by FESEM, XRD, PL, and I-V measurements. It was demonstrated that by varying the seed layer annealing temperature and presence of PEI solution... 

    A diffusion-controlled kinetic model for growth of Au-catalyzed ZnO nanorods: Theory and experiment

    , Article Journal of Crystal Growth ; Volume 309, Issue 1 , 2007 , Pages 70-75 ; 00220248 (ISSN) Hejazi, S. R ; Madaah Hosseini, H. R ; Sharif University of Technology
    2007
    Abstract
    A kinetic model for growth of ZnO nanorods via vapor-liquid-solid (VLS) mechanism based on the bulk diffusion of Zn atoms through the Au-Zn droplet is presented. The dependences of the growth rate on size are given quantitatively. A general expression for the growth rate of nanorods during VLS process is derived. The derived formula shows the dependences of growth rate on lateral size of nanorods, concentration and supersaturation of Zn atoms in the liquid droplet. Based on the presented kinetic model the smaller nanorods have faster growth rate. Au-catalyzed ZnO nanorods are grown by chemical vapor transport and condensation (CVTC) process experimentally. Theoretical and experimental... 

    A wide-range pH indicator based on colorimetric patterns of gold@silver nanorods

    , Article Sensors and Actuators B: Chemical ; Volume 358 , 2022 ; 09254005 (ISSN) Orouji, A ; Abbasi Moayed, S ; Ghasemi, F ; Hormozi Nezhad, M. R ; Sharif University of Technology
    Elsevier B.V  2022
    Abstract
    The potential of hydrogen (pH) is a basic and critical parameter representing the function of numerous chemicals/biomolecules. Due to the widespread applications of pH in diverse fields, the development of rapid and simple yet reliable probes for the determination of pH has attracted significant interest. In this paper, by using AuNRs, silver ions, and ascorbic acid as colorimetric pH sensor, a multicolorimetric nanosensor is described for pH measurement. The reduction of silver ions by ascorbic acid which is strongly influenced by pH, results in silver nanoshell deposition on the surface of AuNRs. Consequently, the formation of Au@Ag core-shell NRs causes a series of blue shifts in the... 

    Preparation, Characterization and Applications of Niobium Oxide Nanorods by Combined Sputtering-Thermal Oxidation Method

    , M.Sc. Thesis Sharif University of Technology karimi khaneghah, Shamim (Author) ; Moshfegh, Ali Reza (Supervisor) ; Akhavan, Omid (Supervisor)
    Abstract
    Recently, quasi 1D (Q1D) structures of materials such as nanowires, nanorods and nanobelts with high surface to volume ratio (A/V) and small grain size devoted an extensive part of researches. This is due to their unique properties and thus various applications in manufacturing of nanometric devices. Niobium pentoxide (Nb2O5) as semiconductor with wide bandgap has been applied in various fields including: electrochromic devices, gas sensors, anti-reflective coatings, capacitors, photocatalysts , field emission and recently; antibacterial systems. In this project , initially niobium thin films was deposited on Si(100) substrate using RF magnetron sputtering method and then niobium oxide... 

    Synthesis and Characterization of Electrophoretic Deposited One- Imensional Nano Structured Titania

    , M.Sc. Thesis Sharif University of Technology Ordikhani, Farideh (Author) ; Mohammadi, Mohammad Reza (Supervisor) ; Khomamizadeh, Farzad (Supervisor)
    Abstract
    Recent studies have indicated that one-dimensional titanium dioxide (TiO2) shows excellent properties in comparison to other forms of TiO2 materials in photocatalysis, sensing, self-cleaning coating and photovoltaic applications. In this project TiO2 nanorods were grown in polycarbonate template, with pore diameter of 200 nm, by solelectrophoretic deposition method. Firstly, properties of TiO2 sol were investigated. The average particle size of TiO2 (measured by zeta sizer instrument) was 17 nm and the zeta potential was around 45 mV, which confirmed good stability of the sol against aging. Moreover, FTIR analysis showed that a full conversion of precursor (titanium isopropoxide) was... 

    Three-dimensional hybrid graphene/nickel electrodes on zinc oxide nanorod arrays as non-enzymatic glucose biosensors

    , Article Sensors and Actuators, B: Chemical ; Volume 251 , 2017 , Pages 462-471 ; 09254005 (ISSN) Mazaheri, M ; Aashuri, H ; Simchi, A ; Sharif University of Technology
    Elsevier B.V  2017
    Abstract
    We present a novel hybrid electrode based on reduced graphene oxide/nickel/zinc oxide heterostructures. The sensor was fabricated by template-free hydrothermal growth of ZnO nanorod arrays on conductive glass substrates (FTO) followed by conformal electrodeposition of nickel nanoparticles with an average size of 18 nm. Then, in-situ reduction and electrophoretic deposition of graphene oxide (GO) nanosheets on the structured ZnO/Ni electrode was performed. The prepared three-dimensional nanostructure exhibited fast electrocatalytic response (<3 s) towards glucose oxidation due to the large surface area and high electro-activity. The prepared biosensor possessed a wide linear range over... 

    Application of Experimental Design for Synthesis and Controlling Aspect Ratio of Metallic Nanorods

    , M.Sc. Thesis Sharif University of Technology Robatjazi, Hossein (Author) ; Jalali-Heravi, Mehdi (Supervisor) ; ormozi Nezhad, Mohammad Reza (Supervisor)
    Abstract
    Aspect ratio dependant optical properties of silver and gold nanorods is responsible for great attention toward controlling the aspect ratio of this class of the nanostructure for their application in variety of area, such as medical diagnosis, drug delivery, biosensing and treatment. In this research, gold and silver nanorods have been synthesized using chemical reducation and growth based on seed mediated method, which is the newest and one of the best methods with less difficulty for producing silver and gold nanorods. Absorption of the visible light by gold and silver nanorods results in appearing the longitudinal and transverse Plasmon bands in their absorption spectra which is related... 

    Sensitive and selective room temperature H2S gas sensor based on Au sensitized vertical ZnO nanorods with flower-like structures

    , Article Journal of Alloys and Compounds ; Volume 628 , April , 2015 , Pages 222-229 ; 09258388 (ISSN) Hosseini, Z. S ; Mortezaali, A ; Iraji Zad, A ; Fardindoost, S ; Sharif University of Technology
    Elsevier Ltd  2015
    Abstract
    Pursuing a sensing structure with a large effective surface area, partial ordered arrays of ZnO nanorods with flower-like structures are introduced for gas sensing applications. Room temperature H2S response of the grown structure shows significant enhancement after modification with Au nanoparticles. High response (about 1270 at 6 ppm H2S gas) and selectivity were achieved by depositing an Au layer with nominal thickness ∼6 nm. X-ray photoelectron spectroscopy (XPS) was utilized to describe the H2S sensing mechanism  

    Graphene-mediated self-assembly of gold nanorods into long fibers with controllable optical properties

    , Article Materials Letters ; Volume 224 , 2018 , Pages 13-17 ; 0167577X (ISSN) Bagheri, P ; Farivar, M ; Simchi, A ; Sharif University of Technology
    Elsevier B.V  2018
    Abstract
    The paper presents graphene-templated self-assembly of gold nanorods into long fibers with controllable optical properties. It is shown that the size of self-assembled nanostructures varies with time and is controlled by chemical reactions between amine groups of graphene and the functional groups of gold. The absorption peak of the nanostructures changes over time while the photoluminescence intensity is quenched. The self-assembled nanostructures with variable plasmon resonance effects are potentially usable for the fabrication of nanoscale devices for biomedical applications. © 2018 Elsevier B.V  

    Engineering of metallic nanorod-based hyperbolic metamaterials for broadband applications operating in the infrared regime

    , Article Applied Nanoscience (Switzerland) ; Volume 11, Issue 1 , 2021 , Pages 229-240 ; 21905509 (ISSN) Baqir, M. A ; Farmani, A ; Raza, M ; Niaz Akhtar, M ; Hussain, A ; Sharif University of Technology
    Springer Science and Business Media Deutschland GmbH  2021
    Abstract
    Metamaterials are manmade structures that have attained considerable attention over the past 2 decades in the modern fields like cloaking, sensing, and imaging owing to their ability to harness electromagnetic fields. In this regard, we have inspected the dielectric properties of the hyperbolic metamaterials (HMM) made of metallic nanorods and dielectric medium at the infrared wavelength regime. The periodically arranged subwavelength-sized metallic nanorods embedded in the silicon dioxide (SiO 2) substrate glass. The spacing between two adjacent nanorods is of subwavelength in size. Furthermore, effective permittivity of the metamaterial has been analyzed by employing the Maxwell Garnett... 

    Synthesis, Characterization and Photocatalytic Application of ZnO/g- C3N4 Composite Nanorods Fabricated by Combined Sol Gel-Hydrothermal Methods

    , M.Sc. Thesis Sharif University of Technology Soltani, Mojtaba (Author) ; Moshfegh, Alireza (Supervisor)
    Abstract
    Because of the working conditions of semiconductors at ambient temperature and pressure, degradation of organic pollutants through semiconductors photocatalysis has attracted the interest of many researchers. Because of its large exciton binding energy,high chemical and physical stability,high electron and hole mobility, and low cost; zinc oxide, an n-type semiconductor with 3.2 eV direct band gap, is widely used in applications such as photocatalysts, solar cells, and light-emitting diodes. Among various morphologies of ZnO, 1D nanostructures such as nanowires and nanorods have recieved much attention due to their high surface to volume ratio. However, the application of ZnO as a... 

    Colorimetric Sensing of Nitrite and Glutathione Based on Morphological Changes of High Aspect Ratio of Gold Nanorods

    , M.Sc. Thesis Sharif University of Technology Fahimi - Kashani, Nafiseh (Author) ; Hormozi Nezhad, Mohammad Reza (Supervisor)
    Abstract
    The fascinating size-dependent properties of noble metal nanop articles have created a great promise for their use in a different applications specially chemical sensing. Gold nanorods (GNRs), specifically, have received a great deal of attention due to their unusual optical properties. The nanoscale confinement of electrons on the surface of gold nanorods grants them aspect ratio-dependent properties not seen in larger particles. Due to the intriguing properties of GNRs, significant work has gone into the application of nanorods for sensing and detection of various an alytes in biological and other systems. The major modalities which have been developed for... 

    , Ph.D. Dissertation Sharif University of Technology (Author) ; Aashuri, Hossein (Supervisor) ; Simchi, Abdolreza (Co-Advisor)
    Abstract
    We demonstrated efficient direct electron transfer from the enzyme glucose oxidase to vertically aligned gold nanorods with a diameter of ~160 nm and a length of ~2 μm that are covalently linkage to a 3-dimensional network of reduced graphene oxide nanosheets. The assembly can be prepared by a 2-step electrochemical procedure. This hybrid structure holds the enzyme in a favorable position while retaining its functionality that ultimately provides enhanced performance for enzymatic sensing of glucose without utilizing mediators. The nanorod assembly was applied to the voltammetric detection of glucose. Figures of merit include an electrochemical sensitivity of 12 µA⋅mM-1⋅cm-2 (obtained from... 

    Growth of One Dimensional TiO2 Nanostructure by Hydrothermal Method

    , M.Sc. Thesis Sharif University of Technology Dadar, Hoda (Author) ; Mohammadi, Mohammad Reza (Supervisor)
    Abstract
    Amongst different methods for synthesis one-dimensional TiO2 nanostructures, hydrothermal process has various advantages such as use of water as growth media and can be defined as an environmentally friendly processing. Hydrothermal processing parameters including processing temperature and time, nature of titanium source and its primary particle size, concentration of titanium source, drying temperature, annealing temperature and re-hydrothermal process have significant influence on crystal structure and morphology of the final product. These parameters were investigated in the present study. Therefore, five different titanium sources including three TiO2 powders and two TiO2 sols as well... 

    Synthesis of Hydroxyapatite Whisker and Nanorods/Polycaprolactone Composites and Scaffolds: In vitro & In vivo studies

    , M.Sc. Thesis Sharif University of Technology Lebasi, Mohammad Ali (Author) ; Mohammadi, Mohammad Reza (Supervisor)
    Abstract
    This work describes the effect of hydroxyapatite with different morphology including nanorods and whisker on the properties of hydroxyapatite/polycaprolactone (HA/PCL) composite. Biodegradable polymer/Hydroxyapatite (HA) composites with the morphology of nanorods and whisker of (HA) as bone replacement scaffolds are synthesized by sol-gel and hydrothermal methods, respectively with a Ca/P ratio of 1.67 and 20:80 (HA/PCL).The crystallization behavior and porosity of HA/PCL composite are studied by scanning electron microscope and X-Ray diffraction. The response of bone marrow-derived human mesenchymal stem cells (hMSCs) in terms of cell proliferation and differentiation to the osteoblastic... 

    In Situ Synthesis of Nanorod Hydroxyapatite Reinforced Polycaprolactone Nanocomposite for Bone Tissue Engineering Application

    , M.Sc. Thesis Sharif University of Technology Moeini, Saeed (Author) ; Mohammadi, Mohammad Reza (Supervisor) ; Simchi, Abdol Reza (Supervisor)
    Abstract
    Hydroxyapatite is the most substantial inorganic constituent of bone tissue which displays splendid biocompability and bioactivity. Nevertheless, its mechanical properties is not utmost appropriate for a bone substitutes. Therefore, it is used to improve the mechanical properties of polymer matrix composite scaffolds. In the present work polycaprolactone as a polymeric matrix was employed to fabricate hydroxyapatite-polycaprolactone biocomposite scaffolds via in situ route. Solvothermal method was employed to synthesize in situ hydroxyapatite in polymer matrix. Porous scaffolds were fabricated via freeze-drying/porogen leaching. Physical, mechanical (compressive module and compressive...