@article {1636,
	title = {Dual-excitation nanocellulose-plasmonic membranes for molecular and cellular SERS detection},
	journal = {ACS applied materials \& interfaces},
	year = {2018},
	author = {S. Zhang and R. Xiong and Mahmoud, M A and E. Quigley and H. Chang and El-Sayed, M. A. and Tsukruk, V. V.}
}
@article {1593,
	title = { Electrically Controlled Plasmonic Behavior of Gold Nanocube@ Polyaniline Nanostructures: Transparent Plasmonic Aggregates},
	journal = {Chem. Mater.},
	year = {2016},
	author = {Jeon, J.-W. and Ledin, P. A. and Geldmeier, J. A. and Ponder, J. F. and Mahmoud, M A and El-Sayed, M. and Reynolds, J. R. and Tsukruk, V. V.}
}
@article {1587,
	title = {Probing Structural Evolution and Charge Storage Mechanism of Nio2hx Electrode Materials Using in Operando Resonance Raman Spectroscopy},
	journal = { Advanced Science},
	year = {2016},
	author = {Chen, D. and Xiong, X. and Zhao, B. and Mahmoud, M A and El-Sayed, M. A. and Liu, M.}
}
@article {1358,
	title = {Hollow and Solid Metallic Nanoparticles in Sensing and in Nanocatalysis},
	journal = {Chemistry of Materials},
	volume = {26},
	number = {1},
	year = {2014},
	note = {Mahmoud, Mahmoud A. O{\textquoteright}Neil, Daniel El-Sayed, Mostafa A.Si},
	month = {Jan},
	pages = {44-58},
	keywords = {n/a},
	isbn = {0897-4756},
	doi = {10.1021/cm4020892},
	author = {Mahmoud, M A and O{\textquoteright}Neil, D. and El-Sayed, M. A.}
}
@article {1359,
	title = {Shape- and Symmetry-Dependent Mechanical Properties of Metallic Gold and Silver on the Nanoscale},
	journal = {Nano Letters},
	volume = {14},
	number = {2},
	year = {2014},
	note = {Mahmoud, Mahmoud A. O{\textquoteright}Neil, Daniel El-Sayed, Mostafa A.},
	month = {Feb},
	pages = {743-748},
	isbn = {1530-6984},
	doi = {10.1021/nl4040362},
	author = {Mahmoud, M A and O{\textquoteright}Neil, D. and El-Sayed, M. A.}
}
@article {1388,
	title = {Determining the Mechanism of Solution Metallic Nanocatalysis with Solid and Hollow Nanoparticles: Homogeneous or Heterogeneous},
	journal = {Journal of Physical Chemistry C},
	volume = {117},
	number = {42},
	year = {2013},
	note = {Mahmoud, Mahmoud A. Garlyyev, Batyr El-Sayed, Mostafa A.},
	month = {Oct},
	pages = {21886-21893},
	isbn = {1932-7447},
	doi = {10.1021/jp4079234},
	author = {Mahmoud, M A and Garlyyev, B. and El-Sayed, M. A.}
}
@article {1391,
	title = {Different Plasmon Sensing Behavior of Silver and Gold Nanorods},
	journal = {Journal of Physical Chemistry Letters},
	volume = {4},
	number = {9},
	year = {2013},
	note = {Mahmoud, Mahmoud A. El-Sayed, Mostafa A.},
	month = {May},
	pages = {1541-1545},
	isbn = {1948-7185},
	doi = {10.1021/jz4005015},
	author = {Mahmoud, M A and El-Sayed, M. A.}
}
@article {1389,
	title = {High-Frequency Mechanical Stirring Initiates Anisotropic Growth of Seeds Requisite for Synthesis of Asymmetric Metallic Nanoparticles like Silver Nanorods},
	journal = {Nano Letters},
	volume = {13},
	number = {10},
	year = {2013},
	note = {Mahmoud, Mahmoud A. El-Sayed, Mostafa A. Gao, Jianping Landman, Uzi},
	month = {Oct},
	pages = {4739-4745},
	isbn = {1530-6984},
	doi = {10.1021/nl402305n},
	author = {Mahmoud, M A and El-Sayed, M. A. and Gao, J. P. and Landman, U.}
}
@article {1392,
	title = {Inducing Cancer Cell Death by Targeting Its Nucleus: Solid Gold Nanospheres versus Hollow Gold Nanocages},
	journal = {Bioconjugate Chemistry},
	volume = {24},
	number = {6},
	year = {2013},
	note = {Mackey, Megan A. Saira, Farhat Mahmoud, Mahmoud A. El-Sayed, Mostafa A.},
	month = {Jun},
	pages = {897-906},
	isbn = {1043-1802},
	doi = {10.1021/bc300592d},
	author = {Mackey, M. A. and Saira, F. and Mahmoud, M A and El-Sayed, M. A.}
}
@article {1374,
	title = {The Last Step in Converting the Surface Plasmonic Energy into Heat by Nanocages and Nanocubes on Substrates},
	journal = {Small},
	volume = {9},
	number = {23},
	year = {2013},
	note = {Szymanski, Paul Mahmoud, Mahmoud A. El-Sayed, Mostafa A.},
	month = {Dec},
	pages = {3934-3938},
	isbn = {1613-6810},
	doi = {10.1002/smll.201300233},
	author = {Szymanski, P. and Mahmoud, M A and El-Sayed, M. A.}
}
@article {1385,
	title = {Properties of pi-Conjugated Fluorescence Polymer-Plasmonic Nanoparticles Hybrid Materials (vol 116, 13336, 2012)},
	journal = {Journal of Physical Chemistry C},
	volume = {117},
	number = {9},
	year = {2013},
	note = {Mahmoud, M. A. Poncheri, A. J. El-Sayed, M. A. Bryant, J. Bunz, U.},
	month = {Mar},
	pages = {4876-4876},
	isbn = {1932-7447},
	doi = {10.1021/jp4006197},
	author = {Mahmoud, M A and Poncheri, A. J. and El-Sayed, M. A. and Bryant, J. and Bunz, U.}
}
@article {1390,
	title = {Substrate Effect on the Plasmonic Sensing Ability of Hollow Nanoparticles of Different Shapes},
	journal = {Journal of Physical Chemistry B},
	volume = {117},
	number = {16},
	year = {2013},
	note = {Mahmoud, Mahmoud A. El-Sayed, Mostafa A.Si},
	month = {Apr},
	pages = {4468-4477},
	isbn = {1520-6106},
	doi = {10.1021/jp3085793},
	author = {Mahmoud, M A and El-Sayed, M. A.}
}
@article {1378,
	title = {Surface-Enhanced Raman Spectroscopy for Real-Time Monitoring of Reactive Oxygen Species-Induced DNA Damage and Its Prevention by Platinum Nanoparticles},
	journal = {Acs Nano},
	volume = {7},
	number = {9},
	year = {2013},
	note = {Panikkanvalappil, Sajanlal R. Mahmoud, Mahmoud A. Mackey, Megan A. El-Sayed, Mostafa A.},
	month = {Sep},
	pages = {7524-7533},
	isbn = {1936-0851},
	doi = {10.1021/nn403722x},
	author = {Panikkanvalappil, S. R. and Mahmoud, M A and Mackey, M. A. and El-Sayed, M. A.}
}
@article {1333,
	title = {Application of surface enhanced Raman spectroscopy to the study of SOFC electrode surfaces},
	journal = {Physical Chemistry Chemical Physics},
	volume = {14},
	number = {17},
	year = {2012},
	note = {Times Cited: 3Li, Xiaxi Blinn, Kevin Fang, Yingcui Liu, Mingfei Mahmoud, Mahmoud A. Cheng, Shuang Bottomley, Lawrence A. El-Sayed, Mostafa Liu, Meilin},
	pages = {5919-5923},
	abstract = {SERS provided by sputtered silver was employed to detect trace amounts of chemical species on SOFC electrodes. Considerable enhancement of Raman signal and lowered detection threshold were shown for coked nickel surfaces, CeO2 coatings, and cathode materials (LSM and LSCF), suggesting a viable approach to probing electrode degradation and surface catalytic mechanism.},
	isbn = {1463-9076},
	doi = {10.1039/c2cp40091j},
	author = {Li, X. X. and Blinn, K. and Fang, Y. C. and Liu, M. F. and Mahmoud, M A and Cheng, S. and Bottomley, L. A. and El-Sayed, M. and Liu, M. L.}
}
@article {1339,
	title = {Different Methods of Increasing the Mechanical Strength of Gold Nanocages},
	journal = {Journal of Physical Chemistry Letters},
	volume = {3},
	number = {23},
	year = {2012},
	note = {Times Cited: 0Mahmoud, Mahmoud A. Szymanski, Paul El-Sayed, Mostafa A.},
	month = {Dec},
	pages = {3527-3531},
	abstract = {Using the ultrafast coherent modulation of the surface plasmon band intensity with the totally symmetric lattice vibration of gold nanocages, we were able to determine and use their frequencies as a measure of the cage{\textquoteright}s mechanical stability. The presence of an inner "stiff" transition-metal nanoshell with a higher value of the elastic modulus is found to increase the frequency of the lattice vibration of the outer soft gold nanoshell. This could also explain the observed increase in both the gold lattice vibrational frequency as well as the lattice vibration relaxation time in the Au-Pt and Au-Pd double-shell nanocages. It is also found that when these nanoparticles are assembled into monolayers on quartz substrates by the Langmuir-Blodgett technique, the oscillation frequency of the gold shell with the transition metal having the largest elastic constant suffers the least change in its oscillation frequency as a result of its resistance to distortion as a result of binding to the substrate.},
	isbn = {1948-7185},
	doi = {10.1021/jz301503z},
	author = {Mahmoud, M A and Szymanski, P. and El-Sayed, M. A.}
}
@article {1335,
	title = {Effect of the Dielectric Constant of the Surrounding Medium and the Substrate on the Surface Plasmon Resonance Spectrum and Sensitivity Factors of Highly Symmetric Systems: Silver Nanocubes},
	journal = {Journal of the American Chemical Society},
	volume = {134},
	number = {14},
	year = {2012},
	note = {Times Cited: 3Mahmoud, Mahmoud A. Chamanzar, Maysamreza Adibi, Ali El-Sayed, Mostafa A.},
	month = {Apr},
	pages = {6434-6442},
	abstract = {Silver nanocubes (AgNCs), 60 nm, have four extinction surface plasmon resonance (SPR) peaks. The finite difference time domain (FDTD) simulation method is used to assign the absorption and scattering peaks and also to calculate the plasmon field intensity for AgNCs. Because AgNCs have a highly symmetric cubic shape, there is a uniform distribution of the plasmon field around them, and they are thus sensitive to asymmetric dielectric perturbations. When the dielectric medium around a nanoparticle is changed anisotropically, either by placing the particle on a substrate or by coating it asymmetrically with a solvent, the plasmon field is distorted, and the plasmonic absorption and scattering spectra could shift differently. For the 60 nm AgNC, we found that the scattering resonance peak shifted more than the absorption peak. This changes the extinction bandwidth of these overlapping absorption and scattering bands, and consequently the figure of merit of the nanoparticle, as a localized SPR sensor, no longer has a constant value.},
	isbn = {0002-7863},
	doi = {10.1021/ja300901e},
	author = {Mahmoud, M A and Chamanzar, M. and Adibi, A. and El-Sayed, M. A.}
}
@article {1337,
	title = {Metallic Double Shell Hollow Nanocages: The Challenges of Their Synthetic Techniques},
	journal = {Langmuir},
	volume = {28},
	number = {9},
	year = {2012},
	note = {Times Cited: 5Mahmoud, M. A. El-Sayed, M. A.},
	month = {Mar},
	pages = {4051-4059},
	abstract = {Hollow metallic nanoparticles have been attracting the attention of many researchers in the past five years due to their new properties and potential applications. The unique structure of the hollow nanoparticles; presence of two surfaces (internal and external), and the presence of both cavities and pores in the wall surfaces of these nanoparticles are responsible for their unique properties and applications. Here the galvanic replacement technique is used to prepare nanocages made of gold, platinum, and palladium. In addition, hollow double shell nanoparticles are made of two metal shells like Au-Pt, Pt-Au, Au-Pd, Pd-Au, Pd-Pt, and Pt-Pd. Silver nanocubes are used as templates during the synthesis of hollow nanoparticles with single metal shell or double shell nanocages. Most of the problems that could affect the synthesis of solid Silver nanocubes used as template as well as the double shell nanocages and their possible solutions are discussed in a detail. The sizes and shapes of the single-shell and double-shell nanocages were characterized by a regular and high-resolution TEM. A SEM mapping technique is also used to image the surface atoms for the double shell hollow nanoparticles in order to determine the thickness of the two metal shells. In addition, optical studies are used to monitor the effect of the dielectric properties of the other metals on the plasmonic properties of the gold nanoshell in these mixed nanoparticles.},
	isbn = {0743-7463},
	doi = {10.1021/la203982h},
	author = {Mahmoud, M A and El-Sayed, M. A.}
}
@article {1345,
	title = {Nanocatalysts Can Change the Number of Electrons Involved in Oxidation-Reduction Reaction with the Nanocages Being the Most Efficient},
	journal = {Journal of Physical Chemistry C},
	volume = {116},
	number = {45},
	year = {2012},
	note = {Times Cited: 0Weng, Guojun Mahmoud, Mahmoud A. El-Sayed, Mostafa A.},
	month = {Nov},
	pages = {24171-24176},
	abstract = {Eosin Y (EY) is a fluorescein derivative dye that can be reduced by accepting either one or two electrons. The one- or two electron reduction potentials have comparable values. The two-electron reduction pathway dominates when sodium borohydride is used, whereas the reduction pathway changes to a one-electron reduction pathway when gold solid (AuNS) or hollow (AuHS) nanosphere catalysts are used. The reduction reaction of EY by borohydride proceeds via one kinetic stage, whereas in the presence of gold nanocatalysts, three different stages are identified. The first stage has the same reaction rate as in the absence of the nanocatalyst, and no one-electron product is observed (absorption peak at 405 nm). The second stage starts when the rate of the disappearance of EY is suddenly increased; a new peak at 405 nm beings to appear. This stage ends when the rate of the disappearance of EY decreases. The third stage has a rate close to that of the first stage, and the EY is reduced again by accepting two electrons. The lifetime of the first stage is greatly affected by the concentration of the nanocatalyst and decreases as the concentration of the nanocatalyst is increased. The conversion ratio of EY to its one electron reduced form is found to increase proportionally with the concentration of the gold nanocatalyst. In the case of using hollow nanospheres as a catalyst, the conversion ratio is found to be 3 times higher than that when using the solid nanospheres due to the cage effect.},
	isbn = {1932-7447},
	doi = {10.1021/jp308869m},
	author = {Weng, G. and Mahmoud, M A and El-Sayed, M. A.}
}
@article {1338,
	title = {Properties of pi-Conjugated Fluorescence Polymer-Plasmonic Nanoparticles Hybrid Materials},
	journal = {Journal of Physical Chemistry C},
	volume = {116},
	number = {24},
	year = {2012},
	note = {Times Cited: 1Mahmoud, M. A. Poncheri, A. J. El-Sayed, M. A.},
	month = {Jun},
	pages = {13336-13342},
	abstract = {Recently, great interest has risen in studying and using hybrid material made by mixing polymeric materials with plasmonic nanoparticles. In the present work, the photophysical properties of two poly(p-phenyleneethynylene) fluorescent polymers, varying in chain length, were studied as a function of (1) pure polymer surface compression after deposition from a Langmuir-Blodgett trough onto a substrate and (2) deposition of a constant amount of polymer onto the surface of silver nanocube arrays of varying particle densities. The results are discussed in terms of the surface pressure and nanoparticle topography effects on conformation of the fluorescent polymer. It was found that the short polymer is much less affected by increased surface pressure, remaining isolated from interchain interaction. The long polymer exhibits signs of conjugation breaking, presumably due to compression of its longer, "tangled", structure. The two polymer chains in the nanoparticle/polymer series of experiments exhibited a blue-shift and a substantial narrowing of their emission spectra when deposited onto the lowest surface pressure nanoparticle sample. With increasing nanoparticle density, the spectra continue to blue-shift and narrow. This effect is presumably a combined effect of conformational changes that shift the emission to higher energy (blue-shift) and plasmonic effects that result in enhancement of primary emission of the polymer (emission from the 0-0 and 1-0 transitions), thus narrowing the emission.},
	isbn = {1932-7447},
	doi = {10.1021/jp303908e},
	author = {Mahmoud, M A and Poncheri, A. J. and El-Sayed, M. A.}
}
@article {1076,
	title = {Following Charge Separation on the Nanoscale in Cu(2)O-Au Nanoframe Hollow Nanoparticles},
	journal = {Nano Letters},
	volume = {11},
	number = {8},
	year = {2011},
	note = {A. Mahmoud, Mahmoud Qian, Wei El-Sayed, Mostafa A.},
	month = {Aug},
	pages = {3285-3289},
	abstract = {Cu(2)O-Au nanoframes with different nanolayer thicknesses of Cu(2)O were prepared, and their photocatalytic properties in aqueous solutions were studied. Cu(2)O semiconductor excitation leads to electron-hole separation. In aqueous solution, the hole is known to oxidize water to produce hydroxyl radicals whose concentration (and that of the holes) can be monitored by the rate of the degradation of dissolved methylene blue dye. The exciton lifetime is determined by femtosecond techniques and is determined by electron-hole recombination which depends on the rates of a number of competing processes such as, electron or hole transfer to an acceptor such as a gold nanoframe and/or the electron or hole trapping processes at the Cu(2)O-Au nanoframe interface. We measured the exciton lifetime as a function of the average Cu(2)O-Au layer separation. A good correlation was found between the rate of the photocatalytic degradation of methylene blue and the exciton lifetime. The exciton lifetime is found to increase as the Cu(2)O thickness is increased. This leads to an increase in the electron-hole separation time and thus an increase in the hole (and so the hydroxyl radical) concentration leading to an observed enhanced rate of the dye degradation.},
	isbn = {1530-6984},
	doi = {10.1021/nl201642r},
	author = {Mahmoud, M A and Qian, Wei and El-Sayed, Mostafa A}
}
@article {1077,
	title = {Plasmonic Field Effects on the Energy Transfer between Poly(p-phenyleneethynylene) Fluorescent Polymer and Au Nanocages},
	journal = {Journal of Physical Chemistry C},
	volume = {115},
	number = {26},
	year = {2011},
	note = {Mahmoud, M. A. El-Sayed, M. A.},
	month = {Jul},
	pages = {12726-12735},
	abstract = {Colloidal gold nanocages (AuNCs) with a wall length of 60 nm and wall thickness of 6 nm were prepared by the galvanic replacement method. The AuNCs were assembled into monolayers with different percents of surface coverage, using the Langmuir-Blodgett technique. The same technique was used to coat the assembled monolayers of AuNCs with another monolayer of poly(p-phenyleneethynylene) (PPE) fluorescent polymer. The surface plasmon resonance (SPR) spectrum of the AuNCs red-shifts as the percent of AuNCs coverage increases due to growth of the interparticle surface plasmon resonance field coupling as interparticle distance decreases. While after coating the AuNCs array with PPE, the SPR of all the AuNCs monolayers arrays were red-shifted to the same position (693 nm). This unsystematic red-shift behavior is based on the presence of two plasmon fields (inside and outside of AuNCs) and is described by discrete dipole approximation (DDA) simulation. The polymer fluorescence intensity is found to decrease when the polymer is deposited over the AuNCs. This observation is due to the energy transfer between the excited PPE and the AuNCs as well interchain energy transfer. Upon turning on the plasmonic field (exciting the surface plasmon resonance band), it is found that the fluorescence intensity of the polymer increased to a maximum value at AuNCs percent coverage of 10\% and then decreased as the interparticle separation distance decreased. DDA calculations showed that this is consistent with the dependence of the SPR field strength on the interparticle separation. Physically, this is a result of the interplay between the changes in the surface plasmon fields within the cavity of each nanoparticle and their external surface fields as a pair of AuNCs approach one another.},
	isbn = {1932-7447},
	doi = {10.1021/jp2007528},
	author = {Mahmoud, M A and El-Sayed, Mostafa A}
}
@article {1078,
	title = {Time Dependence and Signs of the Shift of the Surface Plasmon Resonance Frequency in Nanocages Elucidate the Nanocatalysis Mechanism in Hollow Nanoparticles},
	journal = {Nano Letters},
	volume = {11},
	number = {3},
	year = {2011},
	note = {Mahmoud, M. A. El-Sayed, M. A.},
	month = {Mar},
	pages = {946-953},
	abstract = {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.},
	isbn = {1530-6984},
	doi = {10.1021/nl103265s},
	author = {Mahmoud, M A and El-Sayed, Mostafa A}
}
@article {1092,
	title = {Experimental Evidence For The Nanocage Effect In Catalysis With Hollow Nanoparticles},
	journal = {Nano Letters},
	volume = {10},
	number = {9},
	year = {2010},
	note = {Mahmoud, M. A. Saira, F. El-Sayed, M. A.},
	month = {Sep},
	pages = {3764-3769},
	abstract = {Five different hollow cubic nanoparticles with wall length of 75 nm Were synthesized from platinum and/or palladium elements. The five nanocatalysts are pure platinum nanocages (PtNCs), pure palladium :nanocages (PdNCs), Pt/Pd hollow shell-shell nanocages (NCs) (where Pd is defined as the inner shell around the cavity) Pd/Pt shell-shell NCs, and Pt-Pd alloy NCs. These are used to catalyze the reduction of 4-nitrophenol with sodium borohydride. The kinetic parameters (rate constants, activation energies, frequency factors, and entropies of activation) of each shell/shell NCs are found to be comparable to that of pure metal NCs made of the same metal coating the cavity in the shell-shell NCs. These results strongly Suggest that the catalytic reaction takes place inside the cavity of the hollow nanoparticles. Because of the nanoreactor confinement effect of the hollow nanocatalysts, the frequency factors obtained from the Arrhenius plots are found to be the highest ever reported for this reduction reaction. This is the reason for enhanced rate of this reaction inside the cavity. The importance of mechanism of the homogeneous and the heterogeneous nanocatalytic reactions occurring on the external surface of a solid nanoparticle are contrasted with those occurring on the nanocavity surface.},
	isbn = {1530-6984},
	doi = {10.1021/nl102497u},
	author = {Mahmoud, M A and Saira, F. and El-Sayed, Mostafa A}
}
@article {1094,
	title = {Gold Nanoframes: Very High Surface Plasmon Fields and Excellent Near-Infrared Sensors},
	journal = {Journal of the American Chemical Society},
	volume = {132},
	number = {36},
	year = {2010},
	note = {Mahmoud, Mahmoud A. El-Sayed, Mostafa A.},
	month = {Sep},
	pages = {12704-12710},
	abstract = {The sensing efficiency or factor of noble metal nanoparticles is defined as the wavelength shift of the surface plasmon resonance extinction peak position per unit change in the refractive index of the surrounding medium. The sensitivity of different shapes and sizes of gold nanoparticles has been studied by many investigators and found to depend on the plasmon field strength. As a result, the sensitivity factors were found to be larger for hollow nanoparticles than for solid ones of comparable dimensions. This is due to the strong plasmonic fields resulting from the coupling between the external and internal surface plasmon fields in the hollow nanoparticles. In the present paper, the sensitivity factors of a large number of gold nanoframes of different size and wall thickness have been determined by experimental and theoretical computation (using the discrete dipole approximation method). The dependence of the sensitivity factors and the plasmon field strength on the wall thickness and the size of the nanoframes has been determined and is discussed. The sensitivity factors are found to increase linearly with the aspect ratio (wall length/wall thickness) of the nanoframes and are especially sensitive to a decrease in the wall thickness. In comparison with other plasmonic nanoparticles, it is found that nanoframes have sensitivity factors that are 12, 7, and 3 times higher than those of gold nanospheres, gold nanocubes, and gold nanorods, respectively, as well as more than several hundred units higher than those of comparable-size gold nanocages.},
	isbn = {0002-7863},
	doi = {10.1021/ja104532z},
	author = {Mahmoud, M A and El-Sayed, Mostafa A}
}
@article {1093,
	title = {Plasmonic Field Enhancement of the Exciton-Exciton Annihilation Process in a Poly(p-phenyleneethynylene) Fluorescent Polymer by Ag Nanocubes},
	journal = {Journal of the American Chemical Society},
	volume = {132},
	number = {8},
	year = {2010},
	note = {Mahmoud, Mahmoud A. Poncheri, Adam J. Phillips, Ronnie L. El-Sayed, Mostafa A.},
	month = {Mar},
	pages = {2633-2641},
	abstract = {Using the Langmuir-Blodgett (LB) technique, a poly(paraphenyleneethynylene) (PPE) fluorescent conjugated polymer was assembled on either a quartz substrate (system I) or on the surface of silver nanocube (AgNC) monolayers (system II). The fluorescence intensity of the polymer was studied in system I as a function of the surface density of the polymer sample when deposited on quartz substrates and in system II on the surface coverage of the underlying AgNC monolayers. In system I, a continual increase in the fluorescence intensity is observed as the surface density of excited polymer is increased. In system II, the fluorescence intensity of the polymer first increased until a threshold surface coverage of AgNC was reached, after which it decreased rapidly with increasing surface coverage in the AgNC monolayer. The exciting light intensity dependence is studied before and after this threshold in system II. The results suggest that one-photon processes were responsible for the increased intensity before the threshold, and two-photon processes were responsible for the rapid decrease in the polymer fluorescence intensity after the threshold. These observations are explained by the increase of the surface plasmon enhancement of the exciting light intensity as the nanoparticle surface coverage is increased. In turn, this increases the polymer absorption rate, which results in a continuous increase in the exciton density and is evident by an increase in the fluorescence intensity. At the threshold, the increased exciton density leads to an increase in the rate of exciton-exciton collisions, which leads to exciton-exciton annihilations. When this phenomenon becomes faster than the rate of fluorescence emission, an intensity decrease is observed. By exploiting the surface plasmon enhancement of absorption processes, we have observed the first exciton-exciton annihilation using a low-intensity Hg-lamp continuous wave source.},
	isbn = {0002-7863},
	doi = {10.1021/ja907657j},
	author = {Mahmoud, M A and Poncheri, A. J. and Phillips, R. L. and El-Sayed, Mostafa A}
}
@article {1091,
	title = {Polystyrene Microspheres: Inactive Supporting Material for Recycling and Recovering Colloidal Nanocatalysts in Solution},
	journal = {Journal of Physical Chemistry Letters},
	volume = {1},
	number = {1},
	year = {2010},
	note = {Mahmoud, M. A. Snyder, B. El-Sayed, M. A.},
	month = {Jan},
	pages = {28-31},
	abstract = {Alumina and silica have been the most commonly, used solid supports in the recovery of colloidal nanocatalysts in solution. In order to avoid possible involvement of the support in the catalytic mechanism, polystyrene microspheres are here demonstrated to be effective and nonreactive supports on which the nanocatalyst can be easily attached by using the swelling and shrinking properties of the polystyrene microspheres. The activation energy of the reduction of 4-nitrophenol with sodium borohydride on platinum nanocubes free in solution is comparable to those on polystyrene microspheres.},
	isbn = {1948-7185},
	doi = {10.1021/jz9000449},
	author = {Mahmoud, M A and Snyder, B. and El-Sayed, Mostafa A}
}
@article {1090,
	title = {Surface Plasmon Fields and Coupling in the Hollow Gold Nanoparticles and Surface-Enhanced Raman Spectroscopy. Theory and Experiment},
	journal = {Journal of Physical Chemistry C},
	volume = {114},
	number = {16},
	year = {2010},
	note = {Mahmoud, M. A. Snyder, B. El-Sayed, M. A.},
	month = {Apr},
	pages = {7436-7443},
	abstract = {Most gold nanoparticles have surface plasmon fields only surrounding their surfaces. Recently, hollow nanoparticles have been studied, such as gold nanocages (AuNC) and gold nanoframes (ALINE). Those particles have two types of surfaces, one facing the outside and the other within the cavity. Their coupling provides a surface field inside the hollow particle and on the outside surface. Using DDA computational method, we have shown that the coupling between these fields gives field intensities and distribution inside and outside the nanoparticles that are sensitive to the thickness (the distance between the two surfaces) as well as the nanoparticle size. For small sizes, the coupling between the fields on the opposite sides of the cage is detected. These effects are detected by following the changes in the experimentally observed surface plasmon resonance spectra of these nanoparticles and the surface-enhanced Raman spectra of adsorbed molecules. The effect of the interaction between the external and internal field as well as the available surface area inside and outside the nanoparticle effects on the Raman-enhancement is detected by comparing the Raman intensities dependence on the interparticle distance with those observed on solid nanocubes surfaces.},
	isbn = {1932-7447},
	doi = {10.1021/jp9109018},
	author = {Mahmoud, M A and Snyder, B. and El-Sayed, Mostafa A}
}
@article {1116,
	title = {Aggregation of Gold Nanoframes Reduces, Rather Than Enhances, SERS Efficiency Due to the Trade-Off of the Inter- and Intraparticle Plasmonic Fields},
	journal = {Nano Letters},
	volume = {9},
	number = {8},
	year = {2009},
	note = {Mahmoud, M. A. El-Sayed, M. A.},
	month = {Aug},
	pages = {3025-3031},
	abstract = {It is usually observed and understood that aggregation of silver and gold solid nanoparticles gives rise to enhanced SERS spectra due to the increased plasmon field between the particles. In the present work, we observed that the increase of aggregation of Langmuir-Blodgett assembled 80 nm gold nanoframe particles reduces the efficiency of the surf ace-enhanced Raman spectra of adsorbed thiophenol molecules. Using discrete dipole approximation simulation of the plasmonic fields of a pair of nanoframes as a function of their interparticle separation, it is found that at large separation the fields inside the cavities are stronger than those outside. As the interpair separation decreases, the gain in the interparticle field does not make up for the loss in the field within the cavities, supporting the observation of the decrease in the SERS intensity with aggregation.},
	isbn = {1530-6984},
	doi = {10.1021/nl901501x},
	author = {Mahmoud, M A and El-Sayed, Mostafa A}
}
@article {1107,
	title = {Photocatalysis in Gold Nanocage Nanoreactors},
	journal = {Journal of Physical Chemistry A},
	volume = {113},
	number = {16},
	year = {2009},
	note = {Yen, C. W. Mahmoud, M. A. El-Sayed, M. A.},
	month = {Apr},
	pages = {4340-4345},
	abstract = {The photodegradation of methyl orange was found to take place very efficiently using hollow Au nanocages which are known to have remaining Ag on their interior walls which can be oxidized to Ag(2)O. The degradation rate is found to be more efficient than photodegradation reaction using semiconductor nanomaterials, such as TiO(2) and ZnO. The reaction rate is found to increase by increasing the degree of Ag oxidation on the interior wall of the nanocages prior to the reaction and is a function of the nanocavity size and the pore density of the nanocage walls. As the cage size varies, it is found that the photocatalytic rate increases and then decreases with a maximum rate at nanoparticle size of 75 nm with a medium pore density-in the walls. All these results suggest that the catalysis is occurring inside the cavity, whose interior walls are covered with the Ag(2)O catalysts. Similar to the mechanism proposed in the degradation by the other semiconductors, we propose that the photodegradation mechanism involves the formation of the hydroxyl radical resulting from the photoexcitation of the Ag(2)O semiconductor. The observed results on the rate are discussion in terms of (1) the surface area of the inner wall covered with Ag (Ag(2)O), (2) the density and size of the pores in the walls, and (3) the cavity size of the nanoparticles.},
	isbn = {1089-5639},
	doi = {10.1021/jp811014u},
	author = {Yen, C. W. and Mahmoud, M A and El-Sayed, Mostafa A}
}
@article {1115,
	title = {Surface-Enhanced Raman Scattering Enhancement by Aggregated Silver Nanocube Monolayers Assembled by the Langmuir-Blodgett Technique at Different Surface Pressures},
	journal = {Journal of Physical Chemistry C},
	volume = {113},
	number = {14},
	year = {2009},
	note = {Mahmoud, M. A. Tabor, C. E. El-Sayed, M. A.},
	month = {Apr},
	pages = {5493-5501},
	abstract = {The surface-enhanced Raman scattering spectrum of poly(vinyl) pyrrolidone (PVP) molecules capping 50 nm silver nanocubes assembled in a monolayer via the Langmuir-Blodgett (LB) technique is studied at different surface pressures (at different nanoparticle densities). The observed correlation between the intensity of different SERS bands of the PVP with the nanoparticle density and those of the extinction intensity of the localized surface plasmon resonance bands (as a measure of the surface plasmon field) suggests the following: (1) the observed SERS enhancement results mostly from surface fields of the aggregated nanoparticles; and (2) the relative intensities of the different Raman bands are in reasonable agreement with those expected from the electromagnetic mechanism of enhancement. Besides the large surface plasmon field used in the Raman scattering enhancement, the broad SPR band of the aggregated nanocubes provides an additional advantage in the analytical applications of Raman spectroscopy.},
	isbn = {1932-7447},
	doi = {10.1021/jp900648r},
	author = {Mahmoud, M A and Tabor, C. E. and El-Sayed, Mostafa A}
}
@article {1112,
	title = {On the Use of Plasmonic Nanoparticle Pairs As a Plasmon Ruler: The Dependence of the Near-Field Dipole Plasmon Coupling on Nanoparticle Size and Shape},
	journal = {Journal of Physical Chemistry A},
	volume = {113},
	number = {10},
	year = {2009},
	note = {Tabor, Christopher Murali, Raghunath Mahmoud, Mahmoud El-Sayed, Mostafa A.},
	month = {Mar},
	pages = {1946-1953},
	abstract = {The localized surface plasmon resonance (LSPR) spectral band of a gold or silver nanoparticle is observed to shift as a result of the near-field plasmonic field of another nanoparticle. The dependence of the observed shift on the interparticle distance is used as a ruler in biological systems and gave rise to a plasmonic ruler equation in which the fractional shift in the dipole resonance is found to decrease near exponentially with the interparticle separation in units of the particle size. The exponential decay length constant was observed to be consistent among a small range of nanoparticle sizes, shapes, and types of metal. The equation was derived from the observed results on disks and spherical nanoparticles and confirmed using results on a DNA conjugated nanosphere system. The aim of the present paper is to use electron beam lithography and DDA calculations to examine the constancy of the exponential decay length value in the plasmonic ruler equation on particle size and shape of a number of particles including nanoparticles of different symmetry and orientations. The results suggest that the exponent is almost independent of the size of the nanoparticle but very sensitive to the shape. A discussion of the nanoparticles most suitable for different applications in biological systems and a comparison of the plasmonic ruler with Forster resonance energy transfer (FRET) is mentioned.},
	isbn = {1089-5639},
	doi = {10.1021/jp807904s},
	author = {Tabor, C. E. and Murali, R. and Mahmoud, M A and El-Sayed, Mostafa A}
}
@article {1123,
	title = {Comparative study of the assemblies and the resulting plasmon fields of Langmuir-Blodgett assembled monolayers of silver nanocubes and gold nanocages},
	journal = {Journal of Physical Chemistry C},
	volume = {112},
	number = {37},
	year = {2008},
	note = {Mahmoud, M. A. El-Sayed, M. A.},
	month = {Sep},
	pages = {14618-14625},
	abstract = {Silver nanocubes (72 nm) and gold nanocages (75 nm) were assembled by varying the average interstitial particle distances by the Langmuir-Blodgett technique. The shape of the surface pressure-area isotherms for the two types of nanoparticles are discussed in terms of the degree of surface capping of each nanoparticle which depends on the surface quality. Monolayer films formed at different surface pressures were transferred by the vertical dipping method to silicon and glass substrates where their optical spectra and SEM. images were examined. A red-shift of the strong plasmon peak maximum was observed as the average particle distance was decreased. From the SEM images, the morphology as well as the percent area of the substrate surface covered at different pressures was determined. A linear relationship was observed between the percent of covered area and the plasmon peak maximum, the slope of which reflects the average plasmon field felt by the nanoparticles. The increase in the average field with increasing percent covered area is a result of the decrease in the average nanoparticle separation and/or the increase in the number of nanoparticles in each cluster in the distribution formed. The strength of the plasmon field resulting from gold cages is found to be much higher than that from the silver cubes and increases as the gold wall thickness decreases. These results are discussed in terms of the coupling between the two separate fields of the cage wall surfaces.},
	isbn = {1932-7447},
	doi = {10.1021/jp8040499},
	author = {Mahmoud, M A and El-Sayed, Mostafa A}
}
@article {1122,
	title = {A new catalytically active colloidal platinum nanocatalyst: The multiarmed nanostar single crystal},
	journal = {Journal of the American Chemical Society},
	volume = {130},
	number = {14},
	year = {2008},
	note = {Mahmoud, Mahmoud A. Tabor, Christopher E. El-Sayed, Mostafa A. Ding, Yong Wang, Zhong Lin},
	month = {Apr},
	pages = {4590-+},
	abstract = {Nanocatalysts that possess large amounts of atoms on sharp corners and edges and high indexed sites are known to be more catalytically active. We report here on a novel yet simple method to synthesize in large yields a very active platinum nanocatalyst; the multiarmed nanostar single crystal. We utilize a seed mediated method using tetrahedral nanoparticles that are also synthesized by a new and simple technique. High-resolution TEM shows that the nanostar has many arms, varying from a few to over 30, whereby even the largest ones :re found to have single-crystal structures. This strongly suggests that they are formed by a growth mechanism of the seed crystals and not by the aggregation of seed crystals, which should produce twinning planes. Due to the reduction reaction of ferricyanide by thiosulfate, the nanostars are found to have an activation energy, which is nearly 60\% of that of the tetrahedral seeds themselves, both having the same PVP capping agent. This is undoubtedly due to the multiarms with edges, corners, and the presence of high indexed facets in the nanostar catalyst.},
	isbn = {0002-7863},
	doi = {10.1021/ja710646t},
	author = {Mahmoud, M A and Tabor, C. E. and El-Sayed, Mostafa A and Ding, Y. and Wang, Z.L.}
}
@article {814,
	title = {Reaction of Platinum Nanocatalyst with the Ferricyanide Reactant to Produce Prussian Blue Analogue Complexes},
	journal = {The Journal of Physical Chemistry C},
	volume = {111},
	year = {2007},
	note = {doi: 10.1021/jp709735n},
	month = {2007},
	pages = {17180 - 17183},
	publisher = {American Chemical Society},
	abstract = {The field of catalysis with colloidal nanoparticles is in its infancy. The question of whether the catalysis occurs on the surface of the nanoparticle (thus heterogeneous) or homogeneously in solution using a complex made by the nanoparticle is now being debated. Thus, the molecular mechanism of nanocatalysis has not yet been studied in detail. The first step in this effort is to study the molecular mechanism of the reaction of each reactant with the nanoparticle. This letter is an effort in this direction. A great deal of research has used platinum nanoparticles (PtNPs) to catalyze electron-transfer reactions such as that between thiosulfate and hexacyanoferrate III. We monitored this reaction in detail using optical, Raman, and IR spectroscopies. By increasing the reaction time, two sequential dominant species are formed. The first one is found to have spectral signatures of a Prussian blue analogue with a structure of K[PtIIFeIII(CN)6]. With increasing time, the intensity of the spectrum of this complex is found to decrease, whereas a spectrum similar to that of a complex having the structure of [PtIVFeII(CN)6] increased. A mechanism for the formation of these metal-mixed valency Prussian blue analogues is given.The field of catalysis with colloidal nanoparticles is in its infancy. The question of whether the catalysis occurs on the surface of the nanoparticle (thus heterogeneous) or homogeneously in solution using a complex made by the nanoparticle is now being debated. Thus, the molecular mechanism of nanocatalysis has not yet been studied in detail. The first step in this effort is to study the molecular mechanism of the reaction of each reactant with the nanoparticle. This letter is an effort in this direction. A great deal of research has used platinum nanoparticles (PtNPs) to catalyze electron-transfer reactions such as that between thiosulfate and hexacyanoferrate III. We monitored this reaction in detail using optical, Raman, and IR spectroscopies. By increasing the reaction time, two sequential dominant species are formed. The first one is found to have spectral signatures of a Prussian blue analogue with a structure of K[PtIIFeIII(CN)6]. With increasing time, the intensity of the spectrum of this complex is found to decrease, whereas a spectrum similar to that of a complex having the structure of [PtIVFeII(CN)6] increased. A mechanism for the formation of these metal-mixed valency Prussian blue analogues is given.},
	isbn = {1932-7447},
	doi = {10.1021/jp709735n},
	url = {http://dx.doi.org/10.1021/jp709735n},
	author = {Mahmoud, M A and El-Sayed, Mostafa A}
}
