%0 Journal Article %J Physical Chemistry Chemical Physics %D 2018 %T Defect engineering in 1D Ti–W oxide nanotube arrays and their correlated photoelectrochemical performance %A A.A. Abdelhafiz %A M.A. Ganzoury %A Amer, A. W. %A A.A. Faiad %A A.M. Khalifa %A S.Y. AlQaradawi %A El-Sayed, M. A. %A Alamgir, F. M. %A Allam, N. K. %B Physical Chemistry Chemical Physics %G eng %& 10258 %0 Journal Article %J The Journal of Physical Chemistry C %D 2018 %T Single-Crystal Electrospun Plasmonic Perovskite Nanofibers %A A.M. Abdellah %A A. Hafez %A Panikkanvalappil, S. R. %A El-Sayed, M. A. %A Allam, N. K. %B The Journal of Physical Chemistry C %G eng %0 Journal Article %J J. Phys. Chem. %D 2016 %T Tuning the Photoactivity of Zirconia NanotubesBased Photoanodes Via Ultra-Thin Layers of Zrn: An Effective Approach Towards Visible Light-Water Splitting %A Amer, A. W. %A El-Sayed, M. A. %A Allam, N. K. %B J. Phys. Chem. %G eng %0 Journal Article %J Applied Physics Letters %D 2013 %T Bandgap bowing in Ta-W-O system for efficient solar energy conversion: Insights from density functional theory and X-ray diffraction %A Nashed, R. %A Alamgir, F. M. %A Jang, S. S. %A Ismail, Y. %A El-Sayed, M. A. %A Allam, N. K. %B Applied Physics Letters %V 103 %8 Sep %@ 0003-6951 %G eng %M WOS:000325284500110 %] 133905 %! Appl. Phys. Lett. %R 10.1063/1.4823543 %0 Journal Article %J Journal of Physical Chemistry C %D 2013 %T Thermal/Electrochemical Growth and Characterization of One-Dimensional ZnO/TiO2 Hybrid Nanoelectrodes for Solar Fuel Production %A Shaheen, B. S. %A Salem, H. G. %A El-Sayed, M. A. %A Allam, N. K. %B Journal of Physical Chemistry C %V 117 %P 18502-18509 %8 Sep %@ 1932-7447 %G eng %M WOS:000330162700026 %! J. Phys. Chem. C %R 10.1021/jp405515v %0 Journal Article %J Energy & Environmental Science %D 2011 %T Bacteriorhodopsin/TiO(2) nanotube arrays hybrid system for enhanced photoelectrochemical water splitting %A Allam, N. K. %A Yen, C. W. %A Near, R. D. %A El-Sayed, Mostafa A %X In recent years, considerable efforts have been made to improve the performance of photoactive nanostructured materials for water splitting applications. Herein, we report on the assembly and use of a bacteriorhodopsin (bR)/TiO(2) nanotube array hybrid electrode system. Photoanode materials composed of similar to 7 mu m long self-ordered and vertically oriented nanotube array of titanium dioxide films were fabricated via the anodization of Ti foil in formamide electrolytes containing NH(4)F at room temperature followed by sensitization of the electrodes with bR. The stability of bR on the TiO(2) surface was found to depend on the pretreatment process of the TiO(2) films. Our results demonstrate the opportunity to fabricate fairly stable bR/TiO(2) hybrid electrodes that can be used as photoanodes for photoelectrochemical water splitting. Under AM 1.5 illumination (100 mW/cm(2)), the hybrid electrodes achieved a photocurrent density of 0.65 mA/cm(2) which is a similar to 50% increase over that measured for pure TiO(2) nanotubes (0.43 mA/cm(2)) fabricated and tested under the same conditions. In the presence of a redox electrolyte, the photocurrent increased to 0.87 mA/cm(2). To the best of our knowledge, this is the first report on the use of bR/TiO(2) hybrid electrodes in photoelectrochemical water oxidation cells. We believe the proton pumping property of bR can be used in a variety of applications, especially those related to third generation photovoltaic cells. %B Energy & Environmental Science %V 4 %P 2909-2914 %8 Aug %@ 1754-5692 %G eng %M WOS:000293213600037 %R 10.1039/c1ee01447a %0 Journal Article %J Journal of Physical Chemistry C %D 2011 %T Electrochemical Fabrication of Strontium-Doped TiO(2) Nanotube Array Electrodes and Investigation of Their Photoelectrochemical Properties %A Hamedani, H. A. %A Allam, N. K. %A Garmestani, H. %A El-Sayed, Mostafa A %X In recent years, considerable efforts have been made to improve the performance of photoactive nanostructured materials for water-splitting applications. Herein, we report on the fabrication and photoelectrochemical properties of highly ordered Sr-doped TiO(2) nanotube arrays synthesized via a one-step electrochemical anodization technique. Nanotube arrays of Sr-doped TiO(2) were synthesized via anodization of titanium foil in aqueous electrolytes containing NH(4)F and various concentrations of Sr(OH)(2) at different electrolyte pHs. The morphology and quality of the fabricated materials were found to be significantly affected by the pH of the electrolyte as well as the solubility limit of Sr(OH)(2) in the test electrolyte. The photoelectrochemical measurements revealed that Sr doping can significantly improve the photoconversion efficiency of the material. Using Sr-doped TiO(2) nanotube arrays, an electrode photoconversion efficiency of 0.69% was obtained, which is more than 3 times higher than that of the undoped nanotube arrays (0.2%) fabricated and tested under the same conditions. %B Journal of Physical Chemistry C %V 115 %P 13480-13486 %8 Jul %@ 1932-7447 %G eng %M WOS:000292479700045 %R 10.1021/jp201194b %0 Journal Article %J Acs Applied Materials & Interfaces %D 2011 %T Self-Standing Crystalline TiO(2) Nanotubes/CNTs Heterojunction Membrane: Synthesis and Characterization %A Hesabi, Z. R. %A Allam, N. K. %A Dahmen, K. %A Garmestani, H. %A El-Sayed, Mostafa A %X In the present study, we report for the first time synthesis of TiO(2) nanotubes/CNTs heterojunction membrane. Chemical vapor deposition (CVD) of CNTs at 650 degrees C in a mixture of H(2)/He atmosphere led to in situ detachment of the anodically fabricated TiO(2) nanotube layers from the Ti substrate underneath. Morphological and structural evolution of TiO(2) nanotubes after CNTs deposition were investigated by field- emission scanning electron microscopy (FESEM), glancing angle X-ray diffraction (GAXRD), and X-ray photoelectron spectroscopy (XPS) analyses. %B Acs Applied Materials & Interfaces %V 3 %P 952-955 %8 Apr %@ 1944-8244 %G eng %M WOS:000289762400006 %R 10.1021/am200124p %0 Journal Article %J Acs Nano %D 2011 %T Vertically Oriented Ti-Pd Mixed Oxynitride Nanotube Arrays for Enhanced Photoelectrochemical Water Splitting %A Allam, N. K. %A Poncheri, A. J. %A El-Sayed, Mostafa A %X In recent years, considerable efforts have been made to design and discover photoactive nanostructured materials that can be used as anodes in water photoelectrolysis cells. Herein, we report on the growth of a novel photoanode material composed of self-ordered, vertically oriented nanotube arrays of titanium palladium mixed oxynitride films via anodization of Ti-Pd alloy in an electrolyte solution of formamide containing NH(4)F at room temperature, followed by annealing in an ammonia atmosphere. The nanostructure topology was found to depend on both the anodization time and the applied voltage. Our results demonstrate the ability to grow mixed oxynitride nanotube array films that are several micrometers thick. The Ti-Pd oxynitride nanotube array films were utilized In solar-spectrum water photoelectrolysis, demonstrating a photocurrent density of 1.9 mA/cm(2) and a similar to 5-fold increase in the photoconversion efficiency under AM 1.5 illumination (100 mW/cm(2), 1.0 M KOH) compared to pure TiO(2) nanotubes fabricated and tested under the same conditions; The obtained efficiency is among the highest reported values for a TiO(2) nanotube-based photoelectrochemical cell. This enhancement in the photoconversion efficiency is related to the synergistic effects of Pd alloying, nitrogen doping, and the unique structural properties of the fabricated nanotube arrays. %B Acs Nano %V 5 %P 5056-5066 %8 Jun %@ 1936-0851 %G eng %M WOS:000292055200093 %R 10.1021/nn201136t %0 Journal Article %J Acs Nano %D 2010 %T Enhanced Photoassisted Water Electrolysis Using Vertically Oriented Anodically Fabricated Ti-Nb-Zr-O Mixed Oxide Nanotube Arrays %A Allam, N. K. %A Alamgir, F. %A El-Sayed, Mostafa A %X Self-ordered, highly oriented arrays of titanium-niobium-zirconium mixed oxide nanotube films were fabricated by the anodization of Ti(35)Nb(5)Zr alloy in aqueous and formamide electrolytes containing NH(4)F at room temperature. The nanostructure topology was found to depend on the nature of the electrolyte and the applied voltage. Our results demonstrate the possibility to grow mixed oxide nanotube array films possessing several-micrometer-thick layers by a simple and straightforward electrochemical route. The fabricated Ti-Nb-Zr-O nanotubes showed a similar to 17.5% increase in the photoelectrochemical water oxidation efficiency as compared to that measured for pure TiO(2) nanotubes under UV illumination (100 mW/cm(2), 320-400 nm, 1 M KOH). This enhancement could be related to a combination of the effect of the thin wall of the fabricated Ti-Nb-Zr-O nanotubes (10 +/- 2 nm) and the formation of Zr oxide and Nb oxide layers on the nanotube surface, which seems to slow down the electron-hole recombination in a way similar to that reported for Gratzel solar cells. %B Acs Nano %V 4 %P 5819-5826 %8 Oct %@ 1936-0851 %G eng %M WOS:000283453700046 %R 10.1021/nn101678n %0 Journal Article %J Journal of Physical Chemistry C %D 2010 %T Photoelectrochemical Water Oxidation Characteristics of Anodically Fabricated TiO(2) Nanotube Arrays: Structural and Optical Properties %A Allam, N. K. %A El-Sayed, Mostafa A %X There are currently immense needs to optimize low-cost materials, such as TiO(2), so they can efficiently split water photoelectrochemically into hydrogen and oxygen, thus providing a clean energy fuel. To this end, the nature of the crystalline phase and the dimension of the photocatalyst are of crucial significance. In this study, films of 7 mu m long titania nanotube arrays were fabricated via anodization of titanium foil in formamide electrolytes containing NH(4)F and H(3)PO(4). Upon annealing the as-anodized nanotubes, the anatase-to-rutile phase transformation was found to start at 550 degrees C, which is about 120 degrees C above the temperature observed for the 500 nm long nanotube films, with the nanotube films remaining stable up to 580 degrees C. Analysis of the variation of crystallite size with annealing temperature along with XPS analysis of the films was used to investigate the reason behind this observation. UV-vis measurements showed that the absorption edges of the annealed samples were red shifted from that of the as-anodized sample. The stabilization of the anatase phase up to 550 degrees C, while keeping the tubular structure in place, is very significant as anatase is the most photoactive polymorph of titania. Besides, the 7 mu m long nanotubular structure provides a large surface medium for light utilization through scattering. Used as photoanodes to photoelectrochemically split water, the 580 degrees C crystallized nanotube arrays showed a three-electrode photoconversion efficiency of 10% under UV illumination (100 mW/cm(2), 320-400 nm, 1 M KOH). %B Journal of Physical Chemistry C %V 114 %P 12024-12029 %8 Jul %@ 1932-7447 %G eng %M WOS:000279507900050 %R 10.1021/jp1037014 %0 Journal Article %J Journal of the American Chemical Society %D 2010 %T TiO(2) Nanotube/CdS Hybrid Electrodes: Extraordinary Enhancement in the Inactivation of Escherichia coli %A Hayden, S. C. %A Allam, N. K. %A El-Sayed, Mostafa A %X Titanium dioxide nanotubes offer distinct advantages over films of the same material in the production of hydroxyl radicals and subsequent inactivation of Escherichia coli in wastewater. However, their visible light absorption capabilities are limited. Semiconducting nanocrystals of cadmium sulfide have been used to increase the sensitivity of TiO(2) nanotubes to visible light. A small applied potential, using CdS-coated TiO(2) nanotube arrays, allowed for total inactivation of E. call in hitherto record short time. %B Journal of the American Chemical Society %V 132 %P 14406-14408 %8 Oct %@ 0002-7863 %G eng %M WOS:000283276800030 %R 10.1021/ja107034z