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    Improved efficiency of dye-sensitized solar cells based on a single layer deposition of skein-like TiO 2 nanotubes

    , Article Journal of the American Ceramic Society ; Vol. 97, issue. 9 , 2014 , pp. 2873-2879 ; ISSN: 00027820 Mojaddami, M ; Mohammadi, M. R ; Madaah Hosseini, H. R ; Sharif University of Technology
    Abstract
    We present a new TiO2 morphology, featuring high surface area and open structure, synthesized by a two-step chemical route for the manufacture of dye-sensitized solar cells (DSSCs). This construct is sets of intertwined one-dimensional (1D) nanostructures (i.e., nanotubes), so-called skein-like nanotubes (NTs). Such morphology is produced by a combination of TiC oxidation and hydrothermal processes. The mesoporous TiO2 nanoparticles, as the product of TiC oxidation operation, is used as the precursor of hydrothermal process to grow the skein-like NTs. The effect of processing parameters of TiC oxidation and hydrothermal processes is studied. The skein-like morphology enables to eliminate the... 

    Hydrothermal preparation of TiO2-ZnO nano core-shell structure with quantum size effect

    , Article AIP Conference Proceedings, 12 May 2011 through 15 May 2011 ; Volume 1400 , May , 2011 , Pages 425-428 ; 0094243X (ISSN) ; 9780735409712 (ISBN) Asl, S. K ; Rad, M. K ; Sadrnezhaad, S. K ; Sharif University of Technology
    Abstract
    Nano sized ZnO on TiO 2 spherical core shells were prepared by using hydrothermal method. The particle size of initial TiO 2 was around 20 nm, and the specific surface area was 50 m2/gr. Different ratios of TiO 2 and ZnO applied to synthesize core shell particle. X-ray diffraction (XRD) used to phase characterization and crystalline size, scanning electron microscopy (SEM) to morphology and microstructure investigations. S. Brunauer, P. H. Emmett and E. Teller method (BET) to find specific surface area, Diffusive UV-visible-NIR spectrometry to bang gap calculations. The results indicate that powders with a shell of zinc oxide in specific range have the quantum size effect. Titanium oxide and... 

    TiO2 surface nanostructuring for improved dye loading and light scattering in double-layered screen-printed dye-sensitized solar cells

    , Article Journal of Applied Electrochemistry ; Volume 45, Issue 8 , 2015 , Pages 831-838 ; 0021891X (ISSN) Jalali, M ; Moakhar, R. S ; Kushwaha, A ; Goh, G. K. L ; Sadrnezhaad, S. K ; Riahi Noori, N ; Sharif University of Technology
    Kluwer Academic Publishers  2015
    Abstract
    Abstract: Surface-nanostructured TiO2 nanorods were synthesized hydrothermally at 180 °C. Such nanorods have ‘crack-like’ surfaces that resemble burnt charcoal. Compared to nanorods with relatively smoother surfaces, the charcoal-like nanorods have higher-specific surface areas. By using the nanorods as a light-scattering layer in double-layered dye-sensitized solar cells, the cells based on the charcoal-like nanorods have 20 % higher dye loading and also higher diffuse reflectance compared with cells utilizing ‘smooth’ nanorods. The efficiency of a screen-printed double-layer dye-sensitized solar cell based on the charcoal-like nanorods is higher at 7.29 %. Electrochemical... 

    Preparation and characterization of nanostructured TiO2thin film codoped with nitrogen and vanadium on glass surface by sol–gel dip-coating method

    , Article Research on Chemical Intermediates ; 2014 ; ISSN: 09226168 Khatibnezhad, H ; Sani, M. A. F ; Sharif University of Technology
    Abstract
    To enhance hydrophilicity and photocatalytic activity, N-doped and N–V-codoped TiO2films were coated on glass substrates by the sol–gel dip-coating method. The substrates were previously coated with SiO2using the same method. The coated samples, after annealing at 450 °C for 30 min in air, were analyzed by an X-ray diffractometer, scanning electron microscope, Fourier transform infrared spectroscope, X-ray photoelectron spectroscope, and UV–visible spectroscope. The SiO2/N–V-codoped TiO2photocatalyst showed a narrower band gap (2.93 eV) compared to the SiO2/N-doped. Degradation tests, methyl orange under UV light and stearic acid under visible light, were performed in order to evaluate... 

    Sensor performance of nanostructured TiO2-Cr2O3 thin films derived by a particulate Sol-Gel route with various Cr:Ti molar ratios

    , Article Journal of Electronic Materials ; Vol. 43, issue. 11 , Jul , 2014 , p. 3922-3932 Mohammadi, M. R ; Fray, D. J ; Sharif University of Technology
    Abstract
    Nanocrystalline and nanostructured TiO2-Cr2O3 thin films and powders were prepared by a facile and straightforward aqueous particulate sol-gel route at low temperature of 400°C. The prepared sols showed a narrow particle size distribution with hydrodynamic diameter in the range of 17.7 nm to 19.0 nm. Moreover, the sols were stable over 4 months, with constant zeta potential measured during this period. The effect of the Cr:Ti molar ratio on the crystallization behavior of the products was studied. X-ray diffraction (XRD) analysis revealed that the powders crystallized at low temperature of 400°C, containing anatase-TiO2, rutile-TiO2, and Cr2O3 phases, depending on the annealing temperature... 

    Nanosheet arrays of TiO2synthesized by one step conversion of ZnO nanosheets: Boosting of electron transport rate and application in dye solar cells

    , Article RSC Advances ; Vol. 4, issue. 85 , 2014 , pp. 45174-45179 ; ISSN: 20462069 Alimirsalari, S ; Tajabadi, F ; Salehkoutahi, S. M ; Ghahary, R ; Taghavinia, N ; Sharif University of Technology
    Abstract
    A TiO2replica of ZnO nanosheet films is synthesized using a chemical replacement process. ZnO nanosheets are grown by electrodeposition on fluorine doped tin oxide (FTO) films, and a dissolution/deposition process is used to convert the ZnO template into a TiO2replica. Electron microscopy shows the final TiO2structure follows the morphology of the initial ZnO template. X-ray diffraction and energy dispersive spectroscopy verify the total transformation of ZnO to TiO2. The as-synthesized TiO2sheets are amorphous and after annealing turn into the anatase phase. The film of TiO2nanosheets is used as the photoanode of a dye sensitized solar cell. Despite the low roughness factor of 100, a... 

    Comparative photodecolorization of red dye by anatase, rutile (TiO 2), and wurtzite (ZnO) using response surface methodology

    , Article Turkish Journal of Chemistry ; Volume 36, Issue 1 , 2012 , Pages 121-135 ; 13000527 (ISSN) Asl, S. K ; Sadrnezhaad, S. K ; Rad, M. K ; Üner, D ; Sharif University of Technology
    2012
    Abstract
    Treatment of dye pollution containing C.I. Acid Red 14 (AR14) by a coupled photocatalytic process was studied. Titanium dioxide, in the form of anatase and rutile, and zinc oxide, were used as photocatalysts. The investigated photocatalysts were Aldrich-produced nanopowders with crystallites of a mean size of 20-30 nm and a specific surface area of about 50 m 2/g. A comparison of TiO 2(anatase), TiO 2(rutile), TiO 2(a,r), and ZnO for the decolorization of the AR14 solution was performed. Results showed that color removal followed the decreasing order of TiO 2(a,r), ZnO > TiO 2(a,r) > TiO 2(a), ZnO > TiO 2(r), ZnO >TiO 2(a,r) > TiO 2(a) > ZnO > TiO 2(r). Response surface methodology (RSM) was... 

    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... 

    Structural and optical properties of Pd 2+-doped mesoporous TiO 2 thin films prepared by sol-gel templating technique

    , Article Optoelectronics and Advanced Materials, Rapid Communications ; Volume 4, Issue 10 , 2010 , Pages 1572-1577 ; 18426573 (ISSN) Yarmand, B ; Sadrnezhaad, S. K ; Sharif University of Technology
    2010
    Abstract
    Pd 2+-doped TiO 2 thin films with mesoporous structure were produced on quartz substrate by sol-gel dip coating. The structural, morphological and optical properties of the film were characterized by X-ray diffraction (XRD), Brunauer-Emmett-Teller (BET), transmission electron microscopy (TEM), atomic force microscopy (AFM) and UV/vis transmittance spectroscopy. By increasing the Pd 2+ concentration from 0 to 6 mol%, the crystallites appeared solely as the anatase phase and their average sizes decreased from 10.5 to 7.1 nm. Addition of Pd 2+ also resulted in increasing of the specific surface area and decreasing of the pore size of the layer. The transmittance of the films decreased in the... 

    Micro arc oxidation of nano-crystalline Ag-doped TiO2 semiconductors

    , Article Materials Letters ; Volume 65, Issue 5 , March , 2011 , Pages 840-842 ; 0167577X (ISSN) Bayati, M. R ; 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  

    Application of sugimoto model on particle size prediction of colloidal TiO2 nanoparticles

    , Article Nanotechnology 2010: Advanced Materials, CNTs, Particles, Films and Composites - Technical Proceedings of the 2010 NSTI Nanotechnology Conference and Expo, NSTI-Nanotech 2010, 21 June 2010 through 24 June 2010 ; Volume 1 , 2010 , Pages 436-439 ; 9781439834015 (ISBN) Mehranpour, H ; Askari, M ; Sasani Ghamsari, M ; Farzalibeik, H ; Sharif University of Technology
    2010
    Abstract
    In this paper, Sugimoto model has been employed to study the nucleation and the growth of TiO2 nanoparticles. On the base of this model some parameters of the nucleation and the growth of nanoparticles such as supply rate of the solute (Q0), molar volume of the solid (Vm), and mean volumic growth rate of the stable nuclei during the nucleation period (v) were determined. For this approach, TiO2 nanoparticles were synthesized in two stages in an aqueous solution by using HNO3 and TTIP and TIPO as starting materials. In this experiment, it was obviously observed that the changing of Ti+4concentrations was followed with LaMer diagram. Typical obtained results were v=2.93×102 nm3.s -1 and... 

    Stereoselective synthesis ofβ-Amino ketones via direct mannich-type reaction catalyzed with SO 2- 4/TiO 2 and SO 2- 4/nano TiO 2

    , Article Synthetic Communications ; Volume 39, Issue 24 , 2009 , Pages 4441-4453 ; 00397911 (ISSN) Samet, M ; Eftekhari Sis, B ; Mahmodi Hashemi, M ; Farmad, F ; Sharif University of Technology
    2009
    Abstract
    At room temperature, SO 2- 4/nano-TiO 2 efficiently catalyze the direct Mannich-type reaction of varieties of in situ-generated aldimines using aldehydes and anilines with ketones in a three-component reaction under solvent-free conditions. The reaction proceeds rapidly and affords the correspondingβ-amino ketones in good to high yields with good to excellent stereoselectivity. The catalyst can be recycled for subsequent reactions without any appreciable loss of efficiency  

    Effect of brookite presence on nanocrystalline anatase - Rutile phase transformation

    , Article International Journal of Nanotechnology ; Volume 6, Issue 10-11 , 2009 , Pages 961-972 ; 14757435 (ISSN) Mahshid, S ; Askari, M ; Sasani Ghamsari, M ; Sharif University of Technology
    2009
    Abstract
    TiO2nanocrystals were prepared by hydrolysis and peptisation of titanium isopropoxide under different pH values. The as-prepared powder of very fine anatase crystallites ranges from 8 nm in acidic solution of pH 3 to 10 nm in basic solution of pH 8. Heat treatment of the powders leads to grain growth and anatase - rutile transformation. Experimental results have shown that the anatase to rutile phase transformation in the heat-treated powders depend not only on primary crystallite size but also the presence of brookite phase. It is observed that in the powders with the same size the presence brookite phase would accelerate the anatase to rutile transformation. Furthermore it has been found... 

    Semiconductor TiO2-Al2O3 thin film gas sensors derived from aqueous particulate sol-gel process

    , Article Materials Science in Semiconductor Processing ; Vol. 27, issue , 2014 , p. 711-718 Mohammadi, M. R ; Sharif University of Technology
    Abstract
    Nanostructured TiO2-Al2O3 films and powders were prepared by a straightforward aqueous particulate sol-gel route. Titanium (IV) isopropoxide and aluminum chloride were used as precursors, and hydroxypropyl cellulose was used as a polymeric fugitive agent in order to increase the porosity. The effect of Al:Ti molar ratio was studied on the crystallization behavior of the products. X-ray diffraction (XRD) revealed that the powders crystallized at 800°C, containing anatase-TiO2, rutile-TiO2 and cubic-Al2O3 phases. Furthermore, it was found that Al2O3 retarded the anatase to rutile transformation. Transmission electron microscope (TEM) image showed that one of the smallest crystallite sizes was... 

    Design of TiO2 dye-sensitized solar cell photoanode electrodes with different microstructures and arrangement modes of the layers

    , Article Journal of Sol-Gel Science and Technology ; Volume 76, Issue 3 , December , 2015 , Pages 666-678 ; 09280707 (ISSN) Garmaroudi, Z. A ; Mohammadi, M. R ; Sharif University of Technology
    Kluwer Academic Publishers  2015
    Abstract
    Different structures of TiO2 photoelectrodes were fabricated with various arrangement modes of the layers. TiO2 nanoparticles were synthesized by a combination of sol–gel and solvothermal methods and were employed as the active layer of solar cells. Hierarchical TiO2 spheres (HTS) and spherical TiO2 particles (STP) were also prepared by hydrothermal and sol–gel processes, respectively, and used as the scattering layer of solar cells. Field emission scanning electron microscope and X-ray diffraction analyses revealed that all synthesized morphologies showed anatase structure with particle size around 20, 200–400 nm and 1.5–2.0 µm for the... 

    Photocatalytic activity of rutile/anatase TiO 2 nanorod/nanobranch thin film loaded with Au@Ag@Au core double shell nanoparticles

    , Article Journal of Photochemistry and Photobiology A: Chemistry ; Volume 380 , 2019 ; 10106030 (ISSN) Daneshvar e Asl, S ; Sadrnezhaad, S. K ; Sharif University of Technology
    Elsevier B.V  2019
    Abstract
    A seeding-growth approach was used to prepare Au@Ag@Au core double shell nanoparticles which were loaded on a rutile-nanorods/anatase-nanobranches thin film via the impregnation method. The thin film was synthesized on a fluorine-doped SnO 2 substrate via three stages of (i)TiCl 4 treatment, (ii)hydrothermal, and (iii)aqueous chemistry. The photocatalytic capability of the newly developed nanostructure was higher than P25 TiO 2 thin film by 40% under visible light and by 100% under UV light irradiation. Photogenerated charges separation at the junctions of rutile-nanorods and anatase-nanobranches along with localized surface plasmon resonance followed by the hot electron transfer from the... 

    CVD-grown TiO2 particles as light scattering structures in dye-sensitized solar cells

    , Article RSC Advances ; Volume 2, Issue 32 , 2012 , Pages 12278-12285 ; 20462069 (ISSN) Pazoki, M ; Taghavinia, N ; Abdi, Y ; Tajabadi, F ; Boschloo, G ; Hagfeldt, A ; Sharif University of Technology
    2012
    Abstract
    Chemical vapour deposition (CVD) at atmospheric pressure, using TiCl 4 as a precursor, was used to grow nanostructured TiO2 films on glass substrates. At relatively low temperatures (∼245 °C) and using relatively high reactant concentrations, different nano-morphologies of TiO2 were formed simultaneously, such as spheres, nanowires and mesoporous structures. The TiO2 spheres were successfully applied as light-scattering particles in dye-sensitized solar cells, either by direct deposition onto electrodes in the reactor, or by preparation of a printing paste from the deposited particles. For dye-sensitized solar cells using the organic dye D35 as sensitizer and a cobalt-complex based redox... 

    Visible light photo-induced antibacterial activity of CNT-doped TiO 2 thin films with various CNT contents

    , Article Journal of Materials Chemistry ; Volume 20, Issue 35 , Jun , 2010 , Pages 7386-7392 ; 09599428 (ISSN) Akhavan, O ; Azimirad, R ; Safa, S ; Larijani, M. M ; Sharif University of Technology
    2010
    Abstract
    Carbon nanotube (CNT)-doped TiO2 thin films with various CNT contents were synthesized by sol-gel method for visible light photoinactivation of Escherichia coli bacteria. Post annealing of the CNT-doped TiO2 thin films at 450 °C resulted in anatase TiO2 and formation of Ti-C and Ti-O-C carbonaceous bonds in the film. By increasing the CNT content, the thin films could further inactivate the bacteria in the dark. Meanwhile, as the CNT content increased from zero to 40 wt% the effective optical band gap energy of the CNT-doped TiO2 thin films annealed at 450 °C decreased from 3.2-3.3 to less than ∼2.8 eV providing light absorption in the visible region. Concerning this, visible light... 

    Mesoporous submicrometer TiO 2 hollow spheres as scatterers in dye-sensitized solar cells

    , Article ACS Applied Materials and Interfaces ; Volume 4, Issue 6 , 2012 , Pages 2964-2968 ; 19448244 (ISSN) Dadgostar, S ; Tajabadi, F ; Taghavinia, N ; Sharif University of Technology
    2012
    Abstract
    Hierarchical submicrometer TiO 2 hollow spheres with outer diameter of 300-700 nm and shell thickness of 200 nm are synthesized by liquid phase deposition of TiO 2 over carbon microspheres as sacrificial templates. The final TiO 2 hollow spheres are applied as a scattering layer on top of a transparent nanocrystalline TiO 2 film, serving as the photoanode of a dye-sensitized solar cell (DSC). In addition to efficient light scattering, the mesoporous structure of TiO 2 hollow spheres provides a high surface area, 74 m 2/g, which allows for higher dye loading. This dual functioning suggests that TiO 2 hollow spheres may be good replacements for conventional TiO 2 spheres as scatterers in DSCs.... 

    Synthesis of nanostructured and nanoporous TiO2-AgO mixed oxide derived from a particulate sol-gel route: Physical and sensing characteristics

    , Article Metallurgical and Materials Transactions A: Physical Metallurgy and Materials Science ; Volume 42, Issue 8 , August , 2011 , Pages 2481-2492 ; 10735623 (ISSN) Mohammadi, M. R ; Fray, D. J ; Sharif University of Technology
    2011
    Abstract
    Nanocrystalline TiO2-AgO thin films and powders were prepared by an aqueous particulate sol-gel route at the low temperature of 573 K (300 °C). Titanium tetraisopropoxide and silver nitrate were used as precursors, hydroxypropyl cellulose was used as a polymeric fugitive agent in order to increase the specific surface area. X-ray diffraction (XRD) and Fourier transform infrared spectroscopy (FTIR) revealed that the phase composition of the mixed oxide depends upon the annealing temperature, being a mixture of TiO2 and AgO in the range 573 K to 773 K (300 °C to 500 °C) and a mixture of TiO2, AgO, Ag2O at 973 K (700 °C). Furthermore, one of the smallest crystallite sizes was obtained for TiO...