%0 Journal Article %J Proceedings of the National Academy of Sciences %D 2017 %T Targeting cancer cell integrins using gold nanorods in photothermal therapy inhibits migration through affecting cytoskeletal proteins %A Ali, Moustafa RK %A et al. %K display %B Proceedings of the National Academy of Sciences %G eng %0 Journal Article %J Biomaterials %D 2016 %T Targeting heat shock protein 70 using gold nanorods enhances cancer cell apoptosis in low dose plasmonic photothermal therapy %A Ali, Moustafa RK %A et al. %B Biomaterials %G eng %0 Journal Article %J International journal of nanomedicine %D 2016 %T Treatment of natural mammary gland tumors in canines and felines using gold nanorods-assisted plasmonic photothermal therapy to induce tumor apoptosis %A Ali, M. R. K. %A et al. %B International journal of nanomedicine %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 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 Journal of Physical Chemistry C %D 2013 %T Thin to Thick, Short to Long: Spectral Properties of Gold Nanorods by Theoretical Modeling %A Near, R. D. %A Hayden, S. C. %A El-Sayed, M. A. %B Journal of Physical Chemistry C %V 117 %P 18653-18656 %8 Sep %@ 1932-7447 %G eng %M WOS:000330162700044 %! J. Phys. Chem. C %R 10.1021/jp4078344 %0 Journal Article %J Plos One %D 2013 %T Tissue Distribution and Efficacy of Gold Nanorods Coupled with Laser Induced Photoplasmonic Therapy in Ehrlich Carcinoma Solid Tumor Model %A El-Sayed, M. A. %A Shabaka, A. A. %A El-Shabrawy, O. A. %A Yassin, N. A. %A Mahmoud, S. S. %A El-Shenawy, S. M. %A Al-Ashqar, E. %A Eisa, W. H. %A Farag, N. M. %A El-Shaer, M. A. %A Salah, N. %A Al-Abd, A. M. %X Gold nanorods (GNR) within tumor microregions are characterized by their ability to absorb near IR light and emit heat in what is called photoplasmonic effect. Yet, the efficacy of nanoparticles is limited due to intratumoral tissue distribution reasons. In addition, distribution of GNRs to normal tissue might result in non specific toxicity. In the current study, we are assessing the intratumoral and tissue distribution of PEGylated GNRs on the top of its antitumor characteristics when given intravenously or intratumoral to solid tumor bearing mice and coupled with laser photoplasmonic sessions. PEGylated GNRs with a longitudinal size of less than 100 nm were prepared with aspect ratio of 4.6 showing strong surface plasmon absorption at wavelength 800 nm. Pharmacokinetics of GNR after single I.V. administration (0.1 mg/kg) showed very short systemic circulating time (less than 3 h). On the other hand, tissue distribution of I.V. GNR (0.1 mg/kg) to normal animals showed preferential deposition in spleen tissue. Repeated administration of I.V. GNR resulted in preferential accumulation in both liver and spleen tissues. In addition, I.V. administration of GNR to Ehrlich carcinoma tumor bearing mice resulted in similar tissue distribution; tumor accumulation and anti-tumor effect compared to intratumoral administration. In conclusion, the concentration of GNR achieved within tumors microregions after I.V. administration was comparable to I.T. administration and sufficient to elicit tumoral growth arrest when coupled with laser-aided photoplasmonic treatment. %B Plos One %V 8 %8 Oct %@ 1932-6203 %G eng %M WOS:000325434500052 %] e76207 %R 10.1371/journal.pone.0076207 %0 Conference Proceedings %B SPIE Solar Energy+ Technology %D 2013 %T Towards a perfect system for solar hydrogen production: an example of synergy on the atomic scale %A Nashed, Ramy %A Alamgir, Faisal M %A Seung-Soon, Jang %A Ismail, Yehea %A El-Sayed, Mostafa A. %A Allam, Nageh %B SPIE Solar Energy+ Technology %I International Society for Optics and Photonics %P 88220A-88220A-7 %G eng %0 Conference Proceedings %B CANCER RESEARCH %D 2013 %T Toxicities and antitumor efficacy of tumor-targeted AuNRs in mouse model %A Peng, Xianghong %A Mackey, Megan %A Austin, Lauren %A Oyelere, Adegboyega %A Chen, Georgia %A Huang, Xiaohua %A El-Sayed, Mostafa A. %A Shin, Dong M %B CANCER RESEARCH %I AMER ASSOC CANCER RESEARCH 615 CHESTNUT ST, 17TH FLOOR, PHILADELPHIA, PA 19106-4404 USA %V 73 %@ 0008-5472 %G eng %! Cancer Res. %0 Journal Article %J Nano Letters %D 2011 %T Tailoring Plasmonic and Electrostatic Field Effects To Maximize Solar Energy Conversion by Bacteriorhodopsin, the Other Natural Photosynthetic System %A Yen, C. W. %A Hayden, S. C. %A Dreaden, Erik %A Szymanski, P. %A El-Sayed, Mostafa A %X We have explored the plasmonic field enhancement of current production from bacteriorhodopsin (bR) by maximizing the blue light effect, where the influx of blue photons absorbed by the long-lived M intermediate drastically shortens the time scale of the bR photocycle, leading to current enhancement. To this end, we used three approaches in our solution-based cell: proton selective Nafion membrane. (2) We maximized the plasmonic surface (1) We improved the charge carrier separation in solution through the use of a field effects by selecting the capping polymer with minimum surface field screening and best nanopartide stability. (3) We selected the plasmonic nanoparticle with the strongest plasmonic field whose surface plasmon resonance has the largest spectral overlap with the blue light absorbing M-intermediate. Theoretical models are used to explain experimental results, which show a 40 nm cuboidal nanoparticle capped with 55k PVP polymer to give the best photocurrent enhancement. Enhanced by this particle, bR in our Nafion membrane solution cell gave a photocurrent of 0.21 mu A/cm(3), which is 5000 times larger than the published results for thin film bR electrochemical cells even with an applied bias. Additional possible enhancements are proposed. %B Nano Letters %V 11 %P 3821-3826 %8 Sep %@ 1530-6984 %G eng %M WOS:000294790200054 %R 10.1021/nl2018959 %0 Journal Article %J Nano Letters %D 2011 %T Time Dependence and Signs of the Shift of the Surface Plasmon Resonance Frequency in Nanocages Elucidate the Nanocatalysis Mechanism in Hollow Nanoparticles %A Mahmoud, M A %A El-Sayed, Mostafa A %X Surface plasmon resonance (SPR) wavelength of plasmonic nanopartides is sensitive to changes in the dielectric function of its exposed surface to the medium. Gold nanocages (AuNCs) have two surfaces (inner and outer) and thus two plasmon fields., When the dielectric of the medium changes around the outer surface only, the SPR shifts to different extent from that observed when the dielectric constant of the medium changes around both surfaces. This property of plasmonic AuNCs was used to elucidate the mechanism of the catalytic reduction of 4-nitro to 4-amino phenol, whether it is occurring within the cavity or on the exterior surface of the nanocages. For this purpose two types of nanocages were prepared, one with two plasmonic surfaces and the other with Au/Pt shell-shell nanocages, where only the external surface is plasmonic as gold is outside and Pt is inside. By following the time dependence of the plasmonic band shift resulting from the addition of the reactants and comparing the reaction kinetic parameters for two types of nanocages with those of the pure single metallic nanocages, it was concluded that the catalysis is taking place within the cavity in both types of hollow nanopartides. %B Nano Letters %V 11 %P 946-953 %8 Mar %@ 1530-6984 %G eng %M WOS:000288061500005 %R 10.1021/nl103265s %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 %0 Journal Article %J Bioconjugate Chemistry %D 2009 %T Tamoxifen-Poly(ethylene glycol)-Thiol Gold Nanoparticle Conjugates: Enhanced Potency and Selective Delivery for Breast Cancer Treatment %A Dreaden, Erik %A Mwakwari, S. C. %A Sodji, Q. H. %A Oyelere, A. K. %A El-Sayed, Mostafa A %X The breast cancer treatment drug tamoxifen has been widely administered for more than three decades. This small molecule competes with 17 beta-estradiol for binding to estrogen receptor, a hormone receptor upregulated in a majority of breast cancers, Subsequently initiating programmed cell death. We have synthesized a thiol-PEoylated tamoxifen derivative that can be used to selectively target and deliver plasmonic gold nanoparticles to estrogen receptor positive breast cancer cells with tip to 2.7-fold enhanced drug potency in vitro. Optical microscopy/spectroscopy, tirne-dependent dose-response data, and estrogen competition studies indicate that augmented activity is due to increased rates of intracellular tamoxifen transport by nanoparticle endocytosis, rather than by passive diffusion of the free drug. Both ligand- and receptor-dependent intracellular delivery of gold nanoparticles suggest that plasma membrane localized estrogen receptor alpha may facilitate selective uptake and retention of this and other therapeutic nanoparticle conjugates. Combined targeting selectivity and enhanced potency provides opportunities for both multimodal endocrine treatment strategies and adjunctive laser photothermal therapy. %B Bioconjugate Chemistry %V 20 %P 2247-2253 %8 Dec %@ 1043-1802 %G eng %M WOS:000272690100006 %R 10.1021/bc9002212 %0 Journal Article %J Journal of Physical Chemistry C %D 2008 %T Time-resolved investigation of the acoustic vibration of a single gold nanoprism pair %A Burgin, J. %A Langot, P. %A Del Fatti, N. %A Vallee, F. %A Huang, Wenyu %A El-Sayed, Mostafa A %X The acoustic vibration of single gold nanoprism pairs on a glass substrate has been investigated in the time-domain combining a spatial modulation spectroscopy microscope with a high-sensitivity femtosecond pump-probe setup. Three modes were observed and ascribed to two in-plane and one out-of-plane vibration of the nanoprisms forming the pair, in agreement with a theoretical analysis. The periods of the two former modes with similar nature show weak (about 10%) and well correlated pair to pair fluctuations that can be unambiguously ascribed to variation of the prism geometry. In contrast, strong fluctuations, by almost a factor of 6, of the mode damping are evidenced with no correlation with their period. This indicates large variations of the prism-substrate coupling, providing a unique way for its local investigation. %B Journal of Physical Chemistry C %V 112 %P 11231-11235 %8 Jul %@ 1932-7447 %G eng %M WOS:000257927100026 %R 10.1021/jp802365s %0 Journal Article %J Journal of Physical Chemistry B %D 2003 %T Thermal properties of bacteriorhodopsin %A Heyes, C D %A El-Sayed, Mostafa A %X In this Feature Article we review the effects of various parameters on the structure and thermal stability of one of the most widely studied membrane proteins, bacteriorhodopsin. This protein has recently been crystallized and its high-resolution structure elucidated to 1.55 Angstrom. This information has proved invaluable in understanding its proton-pumping mechanism. However, the question of why bacteriorhodopsin is so stable over a wide range of conditions, and which factors contribute to this stability, is still largely unanswered. Spectroscopic and calorimetric experiments provide information on the thermodynamics, kinetics and structural changes upon unfolding and refolding the protein under various environmental perturbations. FT-IR spectroscopy has been particularly useful in determining the changes in secondary structure upon heating through its thermal transitions after changing pH and cations, removing and adding lipids and detergents, retinal reduction and removal, and site-directed mutagenesis. These experiments are reviewed, and the information that they have afforded have been brought together to try to understand how nature has controlled the conditions of bR to make it one of the most stable proteins known. %B Journal of Physical Chemistry B %V 107 %P 12045-12053 %8 Nov %@ 1520-6106 %G eng %M WOS:000186282200004 %R 10.1021/jp035327b %0 Journal Article %J Journal of Physical Chemistry A %D 2002 %T Thermodynamic and kinetic characterization of the interaction between N-butylamine and similar to 1 nm CdSe nanoparticles %A Landes, Christy F. %A El-Sayed, Mostafa A %X When butylamine (0.1-0.25 M) is added to a colloidal solution of CdSe nanoparticles (NPs) that are 1-2 nm in diameter, the band gap absorption changes from a broad, relatively weak band centered at 445 nm to a narrow, relatively strong absorption centered at 414 nm. The effect of concentration on the observed spectrum shows an isobestic point, suggesting an equilibrium between two species. Thermodynamic and kinetic studies of this process were carried out. The transition was found to be exothermic, with a size-dependent heat of reaction,that suggests that there is a direct proportionality between the NP size and the exothermicity of the interaction. The decay kinetics of the original peak were studied and compared to the rise kinetics of the 414 nm peak. The decay of the original NPs was biexponential, with a lifetime that depends on the NP size, concentration of reactants,. and the temperature. The rise in the 414 nm peak was found to be multiexponential, reflecting 2 transformations from the ensemble having different NP sizes. A mechanism is proposed for this interaction that depends on the binding of butylamine to the NP surface, followed by a release in energy. The nature of the new species absorbing at 414 nm is discussed. %B Journal of Physical Chemistry A %V 106 %P 7621-7627 %8 Aug %@ 1089-5639 %G eng %M WOS:000177472700019 %R 10.1021/jp0201130 %0 Journal Article %J Biophysical Journal %D 2002 %T Time-resolved long-lived infrared emission from bacteriorhodopsin during its photocycle %A Wang, Jianping %A El-Sayed, Mostafa A %X The infrared emission observed below 2000 cm(-1) upon exciting retinal in bacteriorhodopsin (bR) is found to have a rise time in the submicrosecond time regime and to relax with two exponential components on the submillisecond to millisecond time scale. These time scales, together with the assignment of this emission to hot vibrations from the all-trans retinal (in bR) and the 13-cis retinal (in the K intermediate), support the recent assignment of the J-intermediate as an electronically excited species (Atkinson et al., J. Phys. Chem. A. 104:4130-4139, 2000) rather than a vibrationally hot K intermediate. A discussion of these time scales of the observed infrared emission is given in terms of the competition between radiative and nonradiative relaxation processes of the vibrational states involved. %B Biophysical Journal %V 83 %P 1589-1594 %8 Sep %@ 0006-3495 %G eng %M WOS:000177774500033 %0 Journal Article %J Chemical physics letters %D 2002 %T Transfer times of electrons and holes across the interface in CdS/HgS/CdS quantum dot quantum well nanoparticles %A Braun, Markus %A Link, Stephan %A Burda, Clemens %A El-Sayed, Mostafa A %X The electron and hole trapping times in the HgS well of a 6 nm CdS/HgS/CdS quantum dot quantum well nanoparticle were determined from the rise time of the ultrafast transient absorption in the visible and IR regions as well as the trap fluorescence when the CdS core is excited. From the 1.5 ps observed rise time of the well fluorescence (which is determined by the trapping time of the slowest carrier) and the intraband hole IR absorption (150 fs), the electron localization time is found to be 1.5 ps while that of the hole is ∼150 fs. This large difference in the observed dynamics of the electron and hole in crossing the CdS/HgS interface is discussed. %B Chemical physics letters %I Elsevier %V 361 %P 446-452 %@ 0009-2614 %G eng %U http://dx.doi.org/10.1016/S0009-2614(02)01001-1 %N 5-6 %R 10.1016/S0009-2614(02)01001-1 %0 Journal Article %J Chemical Physics Letters %D 2002 %T Transition from nanoparticle to molecular behavior: a femtosecond transient absorption study of a size-selected 28 atom gold cluster %A Link, Stephan %A El-Sayed, Mostafa A %A Schaaff, T. G. %A Whetten, R. L. %X The ultrafast electron dynamics of chemically prepared gold nanoclusters with a 28 atom gold core surrounded by 16 glutathione molecules were investigated. After excitation with femtosecond laser pulses these clusters show an induced transient absorption in the visible from 2.58 to 1.65 eV (480-750 nm) with a maximum around 2.07 eV (600 nm). The excited state relaxation shows a biexponential decay with a subpicosecond and a longer nanosecond decay time independent of the laser pump power. These results are different from those observed previously for larger gold nanoparticles, which suggests that the Au-28-glutathione system shows molecular properties. (C) 2002 Elsevier Science B.V. All rights reserved. %B Chemical Physics Letters %V 356 %P 240-246 %8 Apr %@ 0009-2614 %G eng %M WOS:000175408600009 %R 10.1016/s0009-2614(02)00306-8 %0 Journal Article %J Journal of the American Chemical Society %D 2001 %T Temperature-jump investigations of the kinetics of hydrogel nanoparticle volume phase transitions %A Wang, Jianping %A Gan, D. J. %A Lyon, L. A. %A El-Sayed, Mostafa A %X The dynamics of the deswelling and swelling processes in thermoresponsive poly-N-isopropylacrylamide (pNIPAm) hydrogel nanoparticles have been studied by using time-resolved transmittance measurements, in combination with a nanosecond laser-induced temperature-jump (T-jump) technique. A decrease in the solution transmittance associated with deswelling of the particles has been observed as the solution temperature traverses the volume phase transition temperature of the particles. Upon inducing the T-jump, the deswelling transition only occurs in a small percentage (< 10%) of the particle volume, which was found to be a thin periphery layer of the particles. The particle deswelling occurs on the microsecond time scale, and as shown previously, the collapse time can be tuned via adding small amounts of hydrophobic component to the particle shell. In contrast, the reswelling of the particles was thermodynamically controlled by bath equilibration, and only small differences in particle reswelling kinetics were found due to sluggish heat dissipation (millisecond time scale) from the sample cell. %B Journal of the American Chemical Society %V 123 %P 11284-11289 %8 Nov %@ 0002-7863 %G eng %M WOS:000172239900018 %R 10.1021/ja016610w %0 Journal Article %J Biophysical Journal %D 2001 %T Time-resolved Fourier transform infrared spectroscopy of the polarizable proton continua and the proton pump mechanism of bacteriorhodopsin %A Wang, Jianping %A El-Sayed, Mostafa A %X Nanosecond-to-microsecond time-resolved Fourier transform infrared (FTIR) spectroscopy in the 3000-1000-cm(-1) region has been used to examine the polarizable proton continua observed in bacteriorhodopsin (bR) during its photocycle. The difference in the transient FTIR spectra in the time domain between 20 ns and 1 ms shows a broad absorption continuum band in the 2100-1800-cm(-1) region, a bleach continuum band in the 2500-2150-cm(-1) region, and a bleach continuum band above 2700 cm(-1). According to Zundel (G. Zundel, 1994, J. Mol. Struct. 322.33-42), these continua appear in systems capable of forming polarizable hydrogen bonds. The formation of a bleach continuum suggests the presence of a polarizable proton in the ground state that changes during the photocycle. The appearance of a transient absorption continuum suggests a change in the polarizable proton or the appearance of new ones. It is found that each continuum has a rise time of less than 80 ns and a decay time component of similar to 300 mus. In addition, it is found that the absorption continuum in the 2100-1800-cm(-1) region has a slow rise component of 190 ns and a fast decay component of similar to 60 mus. Using these results and those of the recent x-ray structural studies of bR(570) and M-412 (H. Luecke, B. Schobert, H.T. Richter, J.-P. Cartailler, and J. K. Lanyi, 1999, Science 286:255-260), together with the already known spectroscopic properties of the different intermediates in the photocycle, the possible origins of the polarizable protons giving rise to these continua during the bR photocycle are proposed. Models of the proton pump are discussed in terms of the changes in these polarizable protons and the hydrogen-bonded chains and in terms of previously known results such as the simultaneous deprotonation of the protonated Schiff base (PSB) and Tyr185 and the disappearance of water molecules in the proton release channel during the proton pump process. %B Biophysical Journal %V 80 %P 961-971 %8 Feb %@ 0006-3495 %G eng %M WOS:000166765100038 %0 Journal Article %J Biophysical Journal %D 1999 %T Temperature jump-induced secondary structural change of the membrane protein bacteriorhodopsin in the premelting temperature region: A nanosecond time-resolved Fourier transform infrared study %A Wang, Jianping %A El-Sayed, Mostafa A %X The secondary structural changes of the membrane protein, bacteriorhodopsin, are studied during the premelting reversible transition by using laser-induced temperature jump technique and nanosecond time-resolved Fourier transform infrared spectroscopy. The helical structural changes are triggered by using a 15 degrees C temperature jump induced from a preheated bacteriorhodopsin in D2O solution at a temperature of 72 degrees C. The structural transition from alpha(II)- to alpha(I)-helices is observed by following the change in the frequency of the amide I band from 1667 to 1651 cm(-1) and the shift in the frequency of the amide II vibration from 1542 cm(-1) to 1436 cm(-1) upon H/D exchange. It is found that although the amide I band changes its frequency on a time scale of <100 ns, the H/D exchange shifts the frequency of the amide II band and causes a complex changes in the 1651-1600 cm(-1) and 1530-1430 cm(-1) frequency region on a longer time scale (>300 ns). Our result suggests that in this "premelting transition" temperature region of bacterioriorhodopsin, an intrahelical conformation conversion of the alpha(II) to alpha(I) leads to the exposure of the hydrophobic region of the protein to the aqueous medium. %B Biophysical Journal %V 76 %P 2777-2783 %8 May %@ 0006-3495 %G eng %M WOS:000080278600043 %0 Journal Article %J Journal of Physical Chemistry A %D 1999 %T Temperature-dependent size-controlled nucleation and growth of gold nanoclusters %A Mohamed, MB %A Wang, Z.L. %A El-Sayed, Mostafa A %X The electrochemical method of synthesis of gold nanorods in micelles gives substrate solutions that upon spotting and heating on a transmission electron microscope (TEM) substrate result in the nucleation and growth of small gold nanoclusters of narrow size distribution. The size of the nanoclusters, and not their numbers, is found to increased with increasing final temperature to which the substrate is heated. The data are fitted to a mechanism, based on Ostwald ripening in which atomic gold diffusion followed by nucleation on nucleating sites leads to the formation of these small clusters. %B Journal of Physical Chemistry A %V 103 %P 10255-10259 %8 Dec %@ 1089-5639 %G eng %M WOS:000084318700027 %R 10.1021/jp9919720 %0 Journal Article %J Physical Review B %D 1999 %T Time-resolved Fourier-transform infrared and visible luminescence spectroscopy of photoexcited porous silicon %A Wang, Jianping %A Song, Li %A Zou, Bingsuo %A El-Sayed, Mostafa A %X In order to identify the luminescent centers in aged porous silicon, both the time-resolved vibration spectra in the 750-2000-cm(-1) region and the visible luminescence spectra are studied for the same sample in the 0-440-mu s time domain. Laser excitation gives rise to emission characteristics of the porous silicon as well as strong bleach in the infrared spectrum in the region of the ground-stale silicon-oxygen stretching vibration frequencies at 1100 and 1235 cm(-1). In addition, new transient absorption bands appear in this region as a result of the laser excitation. Three characteristic Lifetimes in the decay of the bleach band at 1235 cm(-1) are observed on the 1-, 10-, and 100-mu s time scale. These are similar to the observed decay times of the photoluminescence from porous silicon. These results suggest that the emitting centers in aged porous silicon are trapped excitation sites in an inhomogeneously defected oxidized silicon surface. [S0163-1829(99)09207-3]. %B Physical Review B %V 59 %P 5026-5031 %8 Feb %@ 0163-1829 %G eng %M WOS:000078778800080 %R 10.1103/PhysRevB.59.5026 %0 Journal Article %J Journal of Physical Chemistry B %D 1998 %T Thermal reshaping of gold nanorods in micelles %A Mohamed, MB %A Ismail, K. Z. %A Link, Stephan %A El-Sayed, Mostafa A %X Gold nanorods are prepared in aqueous solution by an electrochemical method and are shape controlled by using capping micelles as described by Yu et al. (J. Phys. Chem. B 1997, 101 (34), 6661). Transmission electron microscopic (TEM) images are determined for these gold nanorods, taken from solutions heated to various temperatures in the range of 25-160 degrees C. Size and shape analysis of their TEM images showed that the mean aspect ratio of the nanorods in solution decreases with increasing temperature, mostly as a result of reduction in their length. Heating the dried nanorods themselves on a TEM slide to much higher temperatures does not produce any shape changes. This suggests that the observed relative instability of the longer nanorods in the micellar solutions is attributed to the relative instability of the micelles capping the longer gold nanorods. Following the change with time of the longitudinal surface plasmon absorption band of the gold nanorods at five different temperatures, the activation energy for the thermal decomposition of the micelles is found to be 21.0 +/- 1.0 K cal mol(-1). The most stable rod-shaped micelle is found to have an aspect ratio of 2.0. The craft decomposition (dissolution) temperature of these micelles is found to be similar to 155 degrees C. This study offers a new method in which the thermal stability of micelles of various shapes is used to change the size distribution of metal nanorods in solution. On the other hand, TEM or the absorption maximum of the longitudinal plasmon resonance of gold nanorods can be used as a sensitive monitor in studying the physical properties of the host micelles themselves. %B Journal of Physical Chemistry B %V 102 %P 9370-9374 %8 Nov %@ 1089-5647 %G eng %M WOS:000078514100003 %R 10.1021/jp9831482