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ABSTRACT: The plasmon resonance of metal nanoparticles shifts upon refractive index changes of the surrounding medium through the binding
of analytes. The use of this principle allows one to build ultra-small plasmon sensors that can detect analytes (e.g., biomolecules)
in volumes down to attoliters. We use simulations based on the boundary element method to determine the sensitivity of gold
nanorods of various aspect ratios for plasmonic sensors and find values between 3 and 4 to be optimal. Experiments on single
particles confirm these theoretical results. We are able to explain the optimum by showing a corresponding maximum for the
quality factor of the plasmon resonance.
KeywordsPlasmon-Sensors-Nanorods-BEM-Spectroscopy-Nanoparticles-Nanocrystals-Gold
Plasmonics 04/2012; 5(2):161-167. · 2.99 Impact Factor
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ABSTRACT: We compare the single-particle plasmonic sensitivity of silver and gold nanorods with similar resonance wavelengths by monitoring the plasmon resonance shift upon changing the environment from water to 12.5% sucrose solution. We find that silver nanoparticles have 1.2 to 2 times higher sensitivity than gold, in good agreement with simulations based on the boundary-elements-method (BEM). To exclude the effect of particle volume on sensitivity, we test gold rods with increasing particle width at a given resonance wavelength. Using the Drude-model of optical properties of metals together with the quasi-static approximation (QSA) for localized surface plasmons, we show that the dominant contribution to higher sensitivity of silver is the lower background polarizability of the d-band electrons and provide a simple formula for the sensitivity. We improve the reversibility of the silver nanorod sensors upon repeated cycles of environmental changes by blocking the high energy parts of the illumination light.
ACS Nano 08/2011; 5(9):6880-5. · 10.77 Impact Factor
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Thomas D Schladt,
Mohammed Ibrahim Shukoor,
Kerstin Schneider,
Muhammad Nawaz Tahir,
Filipe Natalio,
Irene Ament, Jan Becker,
Florian D Jochum,
Stefan Weber,
Oskar Köhler,
Patrick Theato,
Laura Maria Schreiber,
Carsten Sönnichsen,
Heinz C Schröder,
Werner E G Müller,
Wolfgang Tremel
Angewandte Chemie International Edition 05/2010; 49(23):3976-80. · 13.45 Impact Factor
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Thomas D. Schladt,
Mohammed Ibrahim Shukoor Dr,
Kerstin Schneider,
Muhammad Nawaz Tahir Dr,
Filipe Natalio,
Irene Ament, Jan Becker,
Florian D. Jochum,
Stefan Weber,
Oskar Köhler,
Patrick Theato Dr,
Laura Maria Schreiber Prof. Dr,
Carsten Sönnichsen Prof. Dr,
Heinz C. Schröder Prof. Dr. Dr,
Werner E. G. Müller Prof. Dr,
Wolfgang Tremel Prof. Dr
Angewandte Chemie International Edition 04/2010; 49(23):3976 - 3980. · 13.45 Impact Factor
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Thomas D. Schladt,
Mohammed Ibrahim Shukoor Dr,
Kerstin Schneider,
Muhammad Nawaz Tahir Dr,
Filipe Natalio,
Irene Ament, Jan Becker,
Florian D. Jochum,
Stefan Weber,
Oskar Köhler,
Patrick Theato Dr,
Laura Maria Schreiber Prof. Dr,
Carsten Sönnichsen Prof. Dr,
Heinz C. Schröder Prof. Dr. Dr,
Werner E. G. Müller Prof. Dr,
Wolfgang Tremel Prof. Dr
Angewandte Chemie 04/2010; 122(23):4068 - 4072.
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ABSTRACT: We propose and demonstrate a hybrid cavity system in which metal nanoparticles are evanescently coupled to a dielectric photonic crystal cavity using a nanoassembly method. While the metal constituents lead to strongly localized fields, optical feedback is provided by the surrounding photonic crystal structure. The combined effect of plasmonic field enhancement and high quality factor (Q approximately 900) opens new routes for the control of light-matter interaction at the nanoscale.
Nano Letters 02/2010; 10(3):891-5. · 13.20 Impact Factor
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ABSTRACT: We prepared rod-shaped gold nanorattles solid gold nanorods surrounded by a thin gold shell using a galvanic replacement process starting with silver-coated gold nanorods. These structures are very promising candidates for catalytic applications and optimized plasmon sensors. They combine the advantages of rods (low plasmon resonance frequency, large polarizability, small damping) with the high surface area of hollow structures. The plasmon sensitivity to changes in the dielectric environment is up to 50% higher for gold nanorattles compared to gold nanorods with the same resonance frequency and 6x higher than for plasmons in spherical gold nanoparticles. The catalytic activity measured for the reduction of p-nitrophenol is 4x larger than for bare gold nanorods.
Journal of the American Chemical Society 02/2009; 131(5):1871-5. · 9.91 Impact Factor
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ABSTRACT: We study the wavelength and polarization dependent plasmon resonances of single silver and gold nanorods, triangles, cubes, and dimers with a novel single particle spectroscopy method (RotPOL). In RotPOL, a rotating wedge-shaped polarizer encodes the full polarization information of each particle within one image. This reveals the symmetry of the particles and their plasmon modes, allows analyzing inhomogeneous samples and the monitoring of particle shape changes during growth in situ.
Nano Letters 08/2008; 8(8):2345-50. · 13.20 Impact Factor
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ABSTRACT: Silver coating gold nanorods reduces the ensemble plasmon line width by changing the relation connecting particle shape and plasmon resonance wavelength. This change, we term "plasmonic focusing", leads to less variation of resonance wavelengths for the same particle size distribution. We also find smaller single particle linewidth comparing resonances at the same wavelength but show that this does not contribute to the ensemble linewidth narrowing.
Nano Letters 07/2008; 8(6):1719-23. · 13.20 Impact Factor
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ABSTRACT: We present a nanosized and addressable sensor platform based on membrane coated plasmonic particles and show unequivocally the covering with lipid bilayers as well as the subsequent detection of streptavidin binding to biotinylated lipids. The binding is detected on membrane covered gold nanorods by monitoring the spectral shift by fast single particle spectroscopy (fastSPS) on many particles in parallel. Our approach allows for local analysis of protein interaction with biological membranes as a function of the lateral composition of phase separated membranes.
Nano Letters 07/2008; 8(6):1724-8. · 13.20 Impact Factor
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ABSTRACT: Size- and shape-dependent optical properties of gold nanorods allow monitoring their growth using a novel fast single-particle spectroscopy (fastSPS) method. FastSPS uses a spatially addressable electronic shutter based on a liquid crystal device to investigate particles randomly deposited on a substrate, orders of magnitude faster than other techniques. We use fastSPS to observe nanoparticle growth in situ on a single-particle level and extract quantitative data on nanoparticle growth.
Nano Letters 07/2007; 7(6):1664-9. · 13.20 Impact Factor
