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    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
    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
    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... 

    Optoelectronic properties of cauliflower like ZnO-ZnO nanorod/p-Si heterostructure

    , Article Solid-State Electronics ; Volume 80 , 2013 , Pages 33-37 ; 00381101 (ISSN) Rajabi, M ; Dariani, R. S ; Iraji Zad, A ; Zahedi, F ; Sharif University of Technology
    The cauliflower like ZnO nanostructures are grown on ZnO nanorods using spray pyrolysis method. First, ZnO nanorod arrays are grown on p-type silicon substrate without catalyst by chemical vapor transport and condensation method in a horizontal tube furnace. Afterwards, the cauliflower like ZnO nanostructures is deposited on top of the ZnO nanorod array. The PL spectra of cauliflower like ZnO nanostructures consist of UV emission bands around 387 nm and a visible emission at ∼440 nm. The current-voltage (I-V) measurement under dark and UV illumination condition are performed to study photodetection of the cauliflower like ZnO-ZnO nanorod/p-Si heterostructure. The experimental data of dark... 

    Graphene nanomesh by ZnO nanorod photocatalysts

    , Article ACS Nano ; Volume 4, Issue 7 , 2010 , Pages 4174-4180 ; 19360851 (ISSN) Akhavan, O ; Sharif University of Technology
    Local photodegradation of graphene oxide sheets at the tip of ZnO nanorods was used to achieve semiconducting graphene nanomeshes. The chemically exfoliated graphene oxide sheets, with a thickness of ∼0.9 nm, were deposited on quartz substrates. Vertically aligned ZnO nanorod arrays with diameters of 140 nm and lengths of <1 μm were grown on a glass substrate by using a hydrothermal method. The graphene oxide sheets were physically attached to the tip of the ZnO nanorods by assembling the sheets on the nanorods. UV-assisted photodegradation of the graphene oxide sheets (with dimension of ∼5 × 5 μm) at a contact place with the ZnO nanorods resulted in graphene nanomeshes with a pore size of... 

    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
    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  

    Hydrothermal synthesis of ZnO nanorod arrays for photocatalytic inactivation of bacteria

    , Article Journal of Physics D: Applied Physics ; Volume 42, Issue 22 , 2009 ; 00223727 (ISSN) Akhavan, O ; Mehrabian, M ; Mirabbaszadeh, K ; Azimirad, R ; Sharif University of Technology
    Arrays of ZnO nanorods were synthesized on ZnO seed layer/glass substrates by a hydrothermal method at a low temperature of 70 °C. The effect of pH > 7 of the hydrated zinc nitrate-NaOH precursor on the morphology and topography (e.g. size, surface area and roughness), the optical characteristics (e.g. optical transmission and band-gap energy), hydrophilicity and antibacterial activity of the grown ZnO nanostructure and nanorod coatings were investigated. For pH = 11.33 of the precursor (NaOH concentration of 0.10M), a fast growth of ZnO nanorods on the seed layer (length of ∼1 νm in 1.5 h) was observed. The fast growth of the ZnO nanorods resulted in a significant reduction in the optical... 

    Well-designed Ag/ZnO/3D graphene structure for dye removal: Adsorption, photocatalysis and physical separation capabilities

    , Article Journal of Colloid and Interface Science ; Volume 537 , 2019 , Pages 66-78 ; 00219797 (ISSN) Kheirabadi, M ; Samadi, M ; Asadian, E ; Zhou, Y ; Dong, C ; Zhang, J ; Moshfegh Zaker, A. R ; Sharif University of Technology
    Academic Press Inc  2019
    In this research, adsorption and photocatalytic degradation process were utilized to remove organic dye from wastewater. To accomplish that, a newly-designed ternary nanostructure based on Ag nanoparticles/ZnO nanorods/three-dimensional graphene network (Ag NPs/ZnO NRs/3DG) was prepared using a combined hydrothermal-photodeposition method. The three-dimensional structure of graphene hydrogel as a support for growth of ZnO nanorods was characterized using field emission scanning electron microscopy (FESEM). In addition, diameter of silver nanoparticles grown on the ZnO nanorods with the average aspect ratio of 5 was determined in the range of 30–80 nm by using transmission electron microscopy... 

    Effects of initial precursor and microwave irradiation on step-by-step synthesis of zinc oxide nano-architectures

    , Article Materials Letters ; Volume 67, Issue 1 , 2012 , Pages 342-345 ; 0167577X (ISSN) Kajbafvala, A ; Samberg, J. P ; Ghorbani, H ; Kajbafvala, E ; Sadrnezhaad, S. K ; Sharif University of Technology
    ZnO nano-architectures were produced with the aid of a fast, simple and low cost microwave-assisted synthesis method. Solid semispherical ZnO nanoparticles on the order of 600 nm in diameter along with rice-like ZnO nanorods 95 nm thick were produced from butanol, triethanolamine (TEA), and zinc acetate dihydrate. Solid spherical ZnO nano-architectures with an average diameter of 250 nm were produced from the same starting materials in addition to NaOH. X-ray diffraction, scanning electron microscopy, and transmission electron microscopy were used to characterize the ZnO nano-architectures as well as the precursor. This method is cheap, fast and simple; capable of producing large quantities... 

    ZnO nanowires from nanopillars: influence of growth time

    , Article Current Nanoscience ; Volume 5, Issue 4 , 2009 , Pages 479-484 ; 15734137 (ISSN) Sangpour, P ; Roozbehi, M ; Akhavan, O ; Moshfegh, A. R ; Sharif University of Technology
    A double-tube vapor phase transport system has been used to grow ZnO nanostructures. Nanopillars, nanorods and nanowires of zinc oxide were synthesized on Au nanoparticle catalyst depending on source-substrate distance and temperature gradient in the quartz tube. In addition, influence of growth time and substrate temperature on the morphology of the nanorods and nanowires were also investigated. The scanning electron microscope (SEM), X-ray diffraction (XRD) and transmission electron microscopy (TEM) were employed to further understand the nanostructures growth mechanism on various temperatures and growth time steps. Longer length (>4μm) with hexagonal-cross-sectional nanowires, in [002]... 

    Effect of morphology on the solar photocatalytic behavior of ZnO nanostructures

    , Article Journal of Alloys and Compounds ; Volume 485, Issue 1-2 , 2009 , Pages 616-620 ; 09258388 (ISSN) Mohajerani, M ; Lak, A ; Simchi, A ; Sharif University of Technology
    ZnO nanostructures in the shape of particle, rods, flower-like and micro-sphere were synthesized via facile hydrothermal methods and the effect of morphology on the decolorization of CI Acid Red 27 solution under direct irradiation of sunlight was investigated. XRD patterns showed that the synthesized nanostructures have Wurtzite-type hexagonal structure with high crystallinity and crystallite size in the range of 67-100 nm. UV-vis absorption spectra indicated that the ZnO nanorods have higher visible light harvesting as compared to the other morphologies. The decolorization obeys the first order kinetics rate with the kinetics constant of 4.5-19.5 × 10-3 min-1 dependent on the ZnO... 

    Comparative study of ZnO nanostructures grown on silicon (1 0 0) and oxidized porous silicon substrates with and without Au catalyst by chemical vapor transport and condensation

    , Article Journal of Alloys and Compounds ; Volume 509, Issue 11 , March , 2011 , Pages 4295-4299 ; 09258388 (ISSN) Rajabi, M ; Dariani, R. S ; Zad, A. I ; Sharif University of Technology
    ZnO tetrapods and rods were grown on silicon and thermally oxidized porous silicon substrates with and without Au catalyst layer by carbothermal reduction of ZnO powder through chemical vapor transport and condensation method (CVTC). Porous silicon was fabricated by electrochemical etching of silicon in HF solution. The effect of substrates on morphology, structure and photoluminescence spectra of ZnO nanostructures has been studied. The texture coefficient (TC) of each sample was calculated from XRD data that demonstrated random orientation of ZnO nanostructures on the oxidized porous silicon substrate. Moreover, TC indicates the effect of Au catalyst layer on formation of more highly... 

    ZnO nanoparticle/nanorod-based label-free electrochemical immunoassay for rapid detection of MMP-9 biomarker

    , Article Biochemical Engineering Journal ; Volume 164 , 2020 Shabani, E ; Abdekhodaie, M. J ; Mousavi, S. A ; Taghipour, F ; Sharif University of Technology
    Elsevier B.V  2020
    A label-free electrochemical biosensor was developed for the rapid detection of the matrix metalloproteinase 9 (MMP-9) biomarker on the basis of antibody immobilizing on the zinc oxide (ZnO) nanoparticle and ZnO nanorod electrodes. The charge transfer resistance (Rct) of the electrodes was used as the indicator for MMP-9 concentration, which was obtained through cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS). The ZnO nanorod-based biosensor exhibited linear behavior in the MMP-9 concentration range of 1–1000 ng/ml, which is a wider range than the available concentration ranges for most of the conventional methods. The biosensor sensitivity was 32.5 μA/(decade × cm2)...