Browsing by Author "Eren, H."
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Item Open Access Area-selective atomic layer deposition using an inductively coupled plasma polymerized fluorocarbon layer: A case study for metal oxides(American Chemical Society, 2016) Haider, A.; Deminskyi, P.; Khan, T. M.; Eren, H.; Bıyıklı, NecmiArea-selective atomic layer deposition (AS-ALD) has attracted immense attention in recent years for self-aligned accurate pattern placement with subnanometer thickness control. Here, we demonstrate a methodology to achieve AS-ALD by using inductively couple plasma (ICP) grown fluorocarbon polymer film as hydrophobic blocking layer for selective deposition. Our approach has been tested for metal-oxide materials including ZnO, Al2O3, and HfO2. Contact angle, X-ray photoelectron spectroscopy (XPS), spectroscopic ellipsometer, and scanning electron microscopy (SEM) measurements were performed to investigate the blocking ability of plasma polymerized fluorocarbon layers against ALD-grown metal-oxide films. A considerable growth inhibition for ZnO has been observed on fluorocarbon coated Si(100) surfaces, while the same polymerized surface caused a relatively slow nucleation for HfO2 films. No growth selectivity was obtained for Al2O3 films, displaying almost the same nucleation behavior on Si and fluorocarbon surfaces. Thin film patterning has been demonstrated using this strategy by growing ZnO on lithographically patterned fluorocarbon/Si samples. High resolution SEM images and XPS line scan confirmed the successful patterning of ZnO up to a film thickness of ∼15 nm. © 2016 American Chemical Society.Item Open Access Facile Synthesis of Three-Dimensional Pt-TiO2Nano-networks: A Highly Active Catalyst for the Hydrolytic Dehydrogenation of Ammonia–Borane(Wiley, 2016) Khalily, M. A.; Eren, H.; Akbayrak, S.; Susapto, H. H.; Bıyıklı, Necmi; Özkar, S.; Güler, Mustafa O.Three‐dimensional (3D) porous metal and metal oxide nanostructures have received considerable interest because organization of inorganic materials into 3D nanomaterials holds extraordinary properties such as low density, high porosity, and high surface area. Supramolecular self‐assembled peptide nanostructures were exploited as an organic template for catalytic 3D Pt‐TiO2 nano‐network fabrication. A 3D peptide nanofiber aerogel was conformally coated with TiO2 by atomic layer deposition (ALD) with angstrom‐level thickness precision. The 3D peptide‐TiO2 nano‐network was further decorated with highly monodisperse Pt nanoparticles by using ozone‐assisted ALD. The 3D TiO2 nano‐network decorated with Pt nanoparticles shows superior catalytic activity in hydrolysis of ammonia–borane, generating three equivalents of H2.Item Open Access Monodispersed, highly interactive facet (111)-oriented Pd nanograins by ALD onto free-standing and flexible electrospun polymeric nanofibrous webs for catalytic application(Wiley-VCH Verlag, 2017-10) Ranjith, K. S.; Celebioglu A.; Eren, H.; Bıyıklı, Necmi; Uyar, TamerAn atomic layer deposition (ALD) of monodispersed palladium (Pd) nanograins (≈2 nm) onto electrospun polymeric nanofibers (NF) is presented. By ALD, monodispersed Pd nanograins with (111) exposed facets are decorated on the surface of the free-standing flexible nanofibrous webs (NW). The Pd nanograin-decorated free-standing NW exhibit catalytic reduction of 4-nitrophenol to 4-aminophenol. Even under low loading capacity (≈20 µg mg−1), Pd nanograins manifest effective catalytic performance which can be referred to direct exposure of Pd single crystalline highly interactive (111) plains with high surface area on the NW. The Pd nanograins and the interactive sites along with the high surface area NW yield effective catalytic reduction of 4-nitrophenol to 4-aminophenol with the catalytic reduction rate of 0.0531 min−1. Pd nanograins display thermally tunable effective catalytic reduction properties with activation energy (Ea) of 1.705 J mol−1 on varying the reaction temperature from 12 to 42 °C. Moreover, Pd nanograin-decorated NW are exhibited the effective reusable behavior with stable structural integrity even after repeated catalytic reactions. The approach of this study opens up synthesis and surface decoration of metal nanostructures onto NF through ALD with controlled size and facet orientation for designing reusable and free-standing flexible catalytic nanofibrous materials.Item Open Access Nanoscale selective area atomic layer deposition of TiO2 using e-beam patterned polymers(Royal Society of Chemistry, 2016) Haider A.; Yilmaz, M.; Deminskyi, P.; Eren, H.; Bıyıklı, NecmiHere, we report nano-patterning of TiO2via area selective atomic layer deposition (AS-ALD) using an e-beam patterned growth inhibition polymer. Poly(methylmethacrylate) (PMMA), polyvinylpyrrolidone (PVP), and octafluorocyclobutane (C4F8) were the polymeric materials studied where PMMA and PVP were deposited using spin coating and C4F8 was grown using inductively coupled plasma (ICP) polymerization. TiO2 was grown at 150 °C using tetrakis(dimethylamido) titanium (TDMAT) and H2O as titanium and oxygen precursors, respectively. Contact angle, scanning electron microscopy (SEM), spectroscopic ellipsometry, and X-ray photoelectron spectroscopy (XPS) measurements were performed to investigate the blocking/inhibition effectiveness of polymer layers for AS-ALD of TiO2. TiO2 was grown with different numbers of growth cycles (maximum = 1200 cycles) on PMMA, PVP, and C4F8 coated substrates, where PMMA revealed complete growth inhibition up to the maximum number of growth cycles. On the other hand, PVP was able to block TiO2 growth up to 300 growth cycles only, whereas C4F8 showed no TiO2-growth blocking capability. Finally, mm-, μm-, and nm-scale patterned selective deposition of TiO2 was demonstrated exploiting a PMMA masking layer that has been patterned using e-beam lithography. SEM, energy-dispersive X-ray spectroscopy (EDX) line scan, EDX elemental mapping, and XPS line scan measurements cumulatively confirmed the self-aligned deposition of TiO2 features. The results presented for the first time demonstrate the feasibility of achieving self-aligned TiO2 deposition via TDMAT/H2O precursor combination and e-beam patterned PMMA blocking layers with a complete inhibition for >50 nm-thick films.Item Open Access Pd nanocube decoration onto flexible nanofibrous mats of core-shell polymer-ZnO nanofibers for visible light photocatalysis(Royal Society of Chemistry, 2017) Arslan, O.; Topuz, F.; Eren, H.; Bıyıklı, Necmi; Uyar, TamerPlasmonic enhancement for electron-hole separation efficiency and visible light photocatalysis was achieved by Pd nanocube decoration on a ZnO nanolayer coated onto electrospun polymeric (polyacrylonitrile (PAN)) nanofibers. Since exciton formation and sustainable electron-hole separation have a vital importance for realizing better solar energy in photovoltaic and photocatalytic devices, we achieved visible light photocatalysis by Pd nanocube decoration onto well designed core-shell nanofibers of ZnO@PAN-NF. By controlling the cubic Pd nanoparticle size and the thickness of the crystalline ZnO nanolayer deposited onto electrospun PAN nanofibers via atomic layer deposition (ALD), defect mediated visible light photocatalysis efficiency can be increased. By utilizing nanofabrication techniques such as thermal decomposition, electrospinning and ALD, this fabricated template became an efficient, defect mediated, Pd nanocube plasmon enhanced photocatalytic system. Due to the enhanced contact features of the Pd nanocubes, an increase was observed for the visible light photocatalytic activity of the flexible and nanofibrous mat of Pd@ZnO@PAN-NF.Item Open Access Reusable and flexible heterogeneous catalyst for reduction of TNT by Pd nanocube decorated ZnO nanolayers onto electrospun polymeric nanofibers(Wiley-Blackwell, 2017-10) Arslan, O.; Eren, H.; Bıyıklı, Necmi; Uyar, TamerAn effective method for the fabrication of well designed nanocomposite for the catalytic reduction of 2,4,6-trinitrotoluene (TNT) was developed. Here, cubic palladium (Pd) nanoparticles were utilized for enhancing the interface properties, attachment quality, catalytic yield and stability after the catalysis reactions. Ligand controlled facet growth by the Br- anions during thermal decomposition of the palladium-precursor resulted with cubic shaped average ∼13 nm palladium nanocubes (Pd NC). The anisotropic Pd NC were utilized to decorate the surface of the zinc oxide (ZnO) nanolayers deposited by atomic layer deposition (ALD) technique on the electrospun polyacrylonitrile (PAN) nanofibers. Due to the polymeric nature of the electrospun PAN nanofibers, Pd NC decorated nanoweb is highly flexible and has a high surface area. For the sustainable Pd NC decoration on the ZnO surfaces coated on PAN nanofibers, anchor points were formed by the functional thiol groups which can facilitate the Pd NC attachment and stability on the ZnO surface. The -OH and alkyl thiol groups obtained via sol-gel reactions positioned on the ZnO layer providing a better interface between ZnO and Pd NC which cannot be obtained by pristine PAN nanofibers. Additionally, due to the increased surface interaction, geometrical positioning on fibers for a better intermediate complex formation and stability via soft-soft interaction, Pd NC decorated flexible polymeric electrospun nanoweb provided enhanced catalytic reduction of TNT in aqueous medium.Item Open Access Self-assembled peptide nanofiber templated ALD growth of TiO2 and ZnO semiconductor nanonetworks(Wiley - V C H Verlag GmbH & Co. KGaA, 2016) Garifullin, R.; Eren, H.; Ulusoy, T. G.; Okyay, Ali Kemal; Bıyıklı, Necmi; Güler, Mustafa O.Here peptide amphiphile (PA) nanofiber network is exploited as a three‐dimensional soft template to construct anatase TiO2 and wurtzite ZnO nanonetworks. Atomic layer deposition (ALD) technique is used to coat the organic nanonetwork template with TiO2and ZnO. ALD method enables uniform and conformal coatings with precisely controlled TiO2 and ZnO thickness. The resulting semiconducting metal oxide nanonetworks are utilized as anodic materials in dye‐sensitized solar cells. Effect of metal oxide layer thickness on device performance is studied. The devices based on thin TiO2 coatings (<10 nm) demonstrate considerable dependence on material thickness, whereas thicker (>17 nm) ZnO‐based devices do not show an explicit correlation.Item Open Access Surface decoration of Pt nanoparticles via ALD with TiO2 protective layer on polymeric nanofibers as flexible and reusable heterogeneous nanocatalysts(Nature Publishing Group, 2017) Celebioglu, A.; Ranjith, K. S.; Eren, H.; Bıyıklı, Necmi; Uyar, T.Coupling the functional nanoheterostructures over the flexible polymeric nanofibrous membranes through electrospinning followed by the atomic layer deposition (ALD), here we presented a high surface area platform as flexible and reusable heterogeneous nanocatalysts. Here, we show the ALD of titanium dioxide (TiO2) protective nanolayer onto the electrospun polyacrylonitrile (PAN) nanofibrous web and then platinum nanoparticles (Pt-NP) decoration was performed by ALD onto TiO2 coated PAN nanofibers. The free-standing and flexible Pt-NP/TiO2-PAN nanofibrous web showed the enhancive reduction of 4-nitrophenol (4-NP) to 4-aminophenol (4-AP) within 45 seconds though the hydrogenation process with the degradation rate of 0.1102 s-1. The TiO2 protective layer on the PAN polymeric nanofibers was presented as an effective route to enhance the attachment of Pt-NP and to improve the structure stability of polymeric nanofibrous substrate. Commendable enhancement in the catalytic activity with the catalytic dosage and the durability after the reusing cycles were investigated over the reduction of 4-NP. Even after multiple usage, the Pt-NP/TiO2-PAN nanofibrous webs were stable with the flexible nature with the presence of Pt and TiO2 on its surface.