%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 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 Chemical Society Reviews %D 2011 %T Beating cancer in multiple ways using nanogold %K display %X Gold nanoparticles possess a unique combination of properties which allow them to act as highly multifunctional anti-cancer agents (X. H. Huang, P. K. Jain, I. H. El-Sayed and M. A. El-Sayed, Nanomedicine, 2007, 2, 681-693; P. Ghosh, G. Han, M. De, C. K. Kim and V. M. Rotello, Adv. Drug Delivery Rev., 2008, 60, 1307-1315; S. Lal, S. E. Clare and N. J. Halas, Acc. Chem. Res., 2008, 41, 1842-1851; D. A. Giljohann, D. S. Seferos, W. L. Daniel, M. D. Massich, P. C. Patel and C. A. Mirkin, Angew. Chem., Int. Ed., 2010, 49, 3280-3294). Not only can they be used as targeted contrast agents for photothermal cancer therapy, they can serve as scaffolds for increasingly potent cancer drug delivery, as transfection agents for selective gene therapy, and as intrinsic antineoplastic agents. This tutorial review will highlight some of the many forms and recent applications of these gold nanoparticle conjugates by our lab and others, as well as their rational design and physiologic interactions. %B Chemical Society Reviews %V 40 %P 3391-3404 %@ 0306-0012 %G eng %M WOS:000291807600001 %R 10.1039/c0cs00180e %0 Journal Article %J Photochemistry and Photobiology %D 2010 %T Bacteriorhodopsin O-state Photocycle Kinetics: A Surfactant Study %A Chu, L. K. %A El-Sayed, Mostafa A %X The spectroscopy and dynamics of interaction between the O intermediate of bacteriorhodopsin (bR) and several surfactants (cetrimonium bromide [CTAB], sodium dodecyl sulfate [SDS] and diethylene glycol mono-n-hexyl ether [C6E2]) were investigated using steady-state UV-VIS spectrometry, circular dichroism spectroscopy and time-resolved absorption techniques. The steady-state spectral results show that bR can retain its trimeric state without severe damage in the molar concentration ratio of C6E2/bR ranging up to 4000. Time-resolved observations indicate that the rise and decay rates and transient populations of the O state can be increased in the presence of nonionic surfactant C6E2; however, these studies indicate the opposite phenomenon in the presence of the ionic surfactants CTAB and SDS. The observed 40% enhancement in the transient population of the O intermediate state that results from treatment of C6E2 is proposed to result from an expanding bR structure, which leads to more effective proton pumping efficiency in the photosynthetic system of bR. %B Photochemistry and Photobiology %V 86 %P 70-76 %8 Jan-Feb %@ 0031-8655 %G eng %M WOS:000273318800009 %R 10.1111/j.1751-1097.2009.00629.x %0 Journal Article %J Biosensors & Bioelectronics %D 2010 %T Bacteriorhodopsin-based photo-electrochemical cell %A Chu, L. K. %A Yen, C. W. %A El-Sayed, Mostafa A %X A simple solution-based electrochemical cell has been constructed and successfully employed in the detection of the photoelectric response upon photoexcitation of bacteriorhodopsin (bR) without external bias. Commercially-available indium tin oxide (ITO) glasses served as the optical windows and electrodes. Small amounts of bR suspensions (similar to 100 mu L) were utilized as the photovoltaic medium to generate the proton gradient between two half-cells separated by a molecular porous membrane. Continuous broadband visible light (lambda >380 nm) and a short-pulse 532-nm laser were employed for the photoexcitation of bR. Upon the modulated cw broadband irradiation, an instantaneous rise and decay of the current was observed. Our observations of the pH-dependent photocurrent are consistent with previous reports in a bR thin film configuration, which also showed a polarity inversion at pH 5-6. This is due to the change of the priority of the proton release and proton uptake in the photocycle of bR. Studies on the ionic strength effect were also carried out at different KC1 concentrations, which resulted in the acceleration of the rise and decay of the photoelectric response. This was accompanied by a decrease in the stationary photocurrent at higher KC1 concentrations in the broadband excitation experiments. The solution-based electrochemical cell uses aqueous medium, which is required for the completion of the bR proton pumping function. Due to the generation of the stationary current, it is advantageous to convert solar energy into electricity without the need of film-based photovoltaic devices with external bias. (C) 2010 Elsevier B.V. All rights reserved. %B Biosensors & Bioelectronics %V 26 %P 620-626 %8 Oct %@ 0956-5663 %G eng %M WOS:000283804400051 %R 10.1016/j.bios.2010.07.013 %0 Journal Article %J The Journal of Physical Chemistry %D 1994 %T Binding of, and Energy-Transfer Studies from Retinal to, Organic Cations in Regenerated Reduced Bacteriorhodopsin %A Wu, Shuguang %A El-Sayed, Mostafa A %X See http://dx.doi.org/10.1021/j100088a040 for article's front page in lieu of an abstract %B The Journal of Physical Chemistry %I American Chemical Society %V 98 %P 9339 - 9344 %8 1994 %@ 0022-3654 %G eng %U http://dx.doi.org/10.1021/j100088a040 %N 37 %! J. Phys. Chem. %R doi: 10.1021/j100088a040