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Joseph M. McLellan

Bio: Joseph M. McLellan is an academic researcher from University of Washington. The author has contributed to research in topics: Nanocages & Surface plasmon resonance. The author has an hindex of 20, co-authored 25 publications receiving 4624 citations. Previous affiliations of Joseph M. McLellan include Lawrence Berkeley National Laboratory.

Papers
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TL;DR: Both triangular and hexagonal nanoplates of Pd exhibited surface plasmon resonance (SPR) peaks in the visible region, and their positions matched with the results of discrete dipole approximation (DDA) calculation.
Abstract: The rapid reduction of Na2PdCl4 by ethylene glycol in the presence of poly(vinyl pyrrolidone) (PVP) has recently been demonstrated as a convenient method of generating Pd cubooctahedra and twinned nanoparticles. Here we describe a new procedure where Pd triangular or hexagonal nanoplates could be selectively synthesized by manipulating the reduction kinetics of the polyol process. More specifically, the reduction rate was substantially reduced through the introduction of Fe(III) species and the O2/Cl- pair, two wet etchants for Pd(0). The etching power of the O2/Cl- pair could be further enhanced by adding an acid to lower the pH of the reaction solution. Unlike the previously reported synthesis of Ag and Au nanoplates, light was found to have no indispensable role in the formation of Pd nanoplates. Both triangular and hexagonal nanoplates of Pd exhibited surface plasmon resonance (SPR) peaks in the visible region, and their positions matched with the results of discrete dipole approximation (DDA) calcula...

616 citations

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TL;DR: With a combination of discrete-dipole approximation calculations and single-nanoparticle spectroscopy, the effect of nanostructure aspect ratio and corner sharpness on the frequency of plasmon resonance is explored.
Abstract: Silver nanobars with rectangular side facets and an average aspect ratio of 2.7 have been synthesized by modifying the concentration of bromide added to a polyol synthesis. Subsequent rounding of nanobars transformed them into nanorice. Due to their anisotropy, nanobars and nanorice exhibit two plasmon resonance peaks, scattering light both in the visible and in the near-infrared regions. With a combination of discrete-dipole approximation calculations and single-nanoparticle spectroscopy, we explored the effect of nanostructure aspect ratio and corner sharpness on the frequency of plasmon resonance. Near-field calculations and surface-enhanced Raman scattering measurements on single particles were performed to show how local field enhancement changes with both the wavelength and polarization of incident light.

598 citations

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TL;DR: After galvanic replacement, Pd-Ag and Pt-Ag nanostructures remain SERS active, suggesting their use as a SERS probe for studying the dependence of interfacial chemistry on composition.
Abstract: Silver nanocubes dispersed in water were transformed into Pd−Ag or Pt−Ag nanoboxes by adding either Na2PdCl4 or Na2PtCl4 By controlling the amount of noble metal salt added, and therefore the molar ratio of Na2PdCl4 or Na2PtCl4 to Ag, we could tune the surface plasmon resonance peak of the nanostructures across the entire visible spectrum, from 440 to 730 nm Replacement of Ag with Pd resulted in the formation of a nanobox composed of a Pd−Ag alloy single crystal, but the nanobox formed after replacement of Ag with Pt was instead composed of distinct Pt nanoparticles DDA calculations suggest that both nanoboxes absorb light strongly, with Qabs/Qsca ≈ 5 After galvanic replacement, Pd−Ag and Pt−Ag nanostructures remain SERS active, suggesting their use as a SERS probe for studying the dependence of interfacial chemistry on composition

508 citations

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TL;DR: Gold-silver alloy nanocages with controllable pores on the surface have been synthesized via galvanic replacement reaction between truncated Ag nanocubes and aqueous HAuCl4 using poly(vinyl pyrrolidone) (PVP) as capping agent.
Abstract: Gold−silver alloy nanocages with controllable pores on the surface have been synthesized via galvanic replacement reaction between truncated Ag nanocubes and aqueous HAuCl4. Unlike in the previous studies, the initiation of replacement reaction started in a controllable way, simultaneously from eight corners of the truncated Ag nanocubes where {111} facets were exposed. The formation of cubic nanocages with pores at all the corners was determined by the capping agent, poly(vinyl pyrrolidone) (PVP), which preferentially covered the {100} facets of a truncated Ag nanocube.

422 citations

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TL;DR: A two-step procedure for generating cubic nanocages and nanoframes with relatively narrow SPR peaks by controlling the amount of HAuCl4 used for the galvanic replacement reaction and thus the optimization of the percentage of Au in the alloy nanoboxes is described.
Abstract: This paper describes a two-step procedure for generating cubic nanocages and nanoframes. In the first step, Au/Ag alloy nanoboxes were synthesized through the galvanic replacement reaction between Ag nanocubes and an aqueous HAuCl4 solution. The second step involved the selective removal (or dealloying) of Ag from the alloy nanoboxes with an aqueous etchant based on Fe(NO3)3 or NH4OH. The use of a wet etchant other than HAuCl4 for the dealloying process allows one to better control the wall thickness and porosity of resultant nanocages because there is no concurrent deposition of Au. By increasing the amount of Fe(NO3)3 or NH4OH added to the dealloying process, nanoboxes derived from 50-nm Ag nanocubes could be converted into nanocages and then cubic nanoframes with surface plasmon resonance (SPR) peaks continuously shifted from the visible region to 1200 nm. It is also possible to obtain nanocages with relatively narrow SPR peaks (with a full width at half-maximum as small as 180 nm) by controlling the amount of HAuCl4 used for the galvanic replacement reaction and thus the optimization of the percentage of Au in the alloy nanoboxes.

353 citations


Cited by
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TL;DR: The arsenal of nanocarriers and molecules available for selective tumour targeting, and the challenges in cancer treatment are detailed and emphasized.
Abstract: Nanotechnology has the potential to revolutionize cancer diagnosis and therapy. Advances in protein engineering and materials science have contributed to novel nanoscale targeting approaches that may bring new hope to cancer patients. Several therapeutic nanocarriers have been approved for clinical use. However, to date, there are only a few clinically approved nanocarriers that incorporate molecules to selectively bind and target cancer cells. This review examines some of the approved formulations and discusses the challenges in translating basic research to the clinic. We detail the arsenal of nanocarriers and molecules available for selective tumour targeting, and emphasize the challenges in cancer treatment.

7,443 citations

Journal ArticleDOI
TL;DR: A comprehensive review of current research activities that center on the shape-controlled synthesis of metal nanocrystals, including a brief introduction to nucleation and growth within the context of metal Nanocrystal synthesis, followed by a discussion of the possible shapes that aMetal nanocrystal might take under different conditions.
Abstract: Nanocrystals are fundamental to modern science and technology. Mastery over the shape of a nanocrystal enables control of its properties and enhancement of its usefulness for a given application. Our aim is to present a comprehensive review of current research activities that center on the shape-controlled synthesis of metal nanocrystals. We begin with a brief introduction to nucleation and growth within the context of metal nanocrystal synthesis, followed by a discussion of the possible shapes that a metal nanocrystal might take under different conditions. We then focus on a variety of experimental parameters that have been explored to manipulate the nucleation and growth of metal nanocrystals in solution-phase syntheses in an effort to generate specific shapes. We then elaborate on these approaches by selecting examples in which there is already reasonable understanding for the observed shape control or at least the protocols have proven to be reproducible and controllable. Finally, we highlight a number of applications that have been enabled and/or enhanced by the shape-controlled synthesis of metal nanocrystals. We conclude this article with personal perspectives on the directions toward which future research in this field might take.

4,927 citations

Journal ArticleDOI

3,326 citations

Journal ArticleDOI
04 May 2007-Science
TL;DR: Platinum NCs of unusual tetrahexahedral (THH) shape were prepared at high yield by an electrochemical treatment of Pt nanospheres supported on glassy carbon by a square-wave potential to exhibit much enhanced catalytic activity for equivalent Pt surface areas for electro-oxidation of small organic fuels such as formic acid and ethanol.
Abstract: The shapes of noble metal nanocrystals (NCs) are usually defined by polyhedra that are enclosed by {111} and {100} facets, such as cubes, tetrahedra, and octahedra. Platinum NCs of unusual tetrahexahedral (THH) shape were prepared at high yield by an electrochemical treatment of Pt nanospheres supported on glassy carbon by a square-wave potential. The single-crystal THH NC is enclosed by 24 high-index facets such as {730}, {210}, and/or {520} surfaces that have a large density of atomic steps and dangling bonds. These high-energy surfaces are stable thermally (to 800°C) and chemically and exhibit much enhanced (up to 400%) catalytic activity for equivalent Pt surface areas for electro-oxidation of small organic fuels such as formic acid and ethanol.

2,782 citations