61 research outputs found
Non-specific cellular uptake of surface-functionalized quantum dots
We report a systematic empirical study of nanoparticle internalization into
cells via non-specific pathways. The nanoparticles were comprised of commercial
quantum dots (QDs) that were highly visible under a fluorescence confocal
microscope. Surface-modified QDs with basic biologically-significant moieties,
e.g. carboxyl, amino, streptavidin were used, in combination with the surface
derivatization with polyethylene glycol (PEG) in a range of immortalized cell
lines. Internalization rates were derived from image analysis and a detailed
discussion about the effect of nanoparticle size, charge and surface groups is
presented. We find that PEG-derivatization dramatically suppresses the
non-specific uptake while PEG-free carboxyl and amine functional groups promote
QD internalization. These uptake variations displayed a remarkable consistency
across different cell types. The reported results are important for experiments
concerned with cellular uptake of surface-functionalized nanomaterials, both
when non-specific internalization is undesirable and also when it is intended
for material to be internalized as efficiently as possible.
Published article at: http://iopscience.iop.org/0957-4484/21/28/285105/Comment: 14 pages 7 figure
Direct Observation of Propagating Gigahertz Coherent Guided Acoustic Phonons in Free Standing Single Copper Nanowires
We report on gigahertz acoustic phonon waveguiding in free-standing single
copper nanowires studied by femtosecond transient reflectivity measurements.
The results are discussed on the basis of the semianalytical resolution of the
Pochhammer and Chree equation. The spreading of the generated Gaussian wave
packet of two different modes is derived analytically and compared with the
observed oscillations of the sample reflectivity. These experiments provide a
unique way to independently obtain geometrical and material characterization.
This direct observation of coherent guided acoustic phonons in a single
nano-object is also the first step toward nanolateral size acoustic transducer
and comprehensive studies of the thermal properties of nanowires
Localised and delocalised plasmons in metallic nano-voids
Nanostructured metal films comprised of periodically arranged spherical voids are grown by electrochemical deposition through a self-assembled template. Detailed measurements of the angle- and orientation-dependent reflectivity for different sample geometries reveal the spectral dispersion of several different types of surface plasmon modes. The dependence of the energies of both delocalized Bragg and localized Mie plasmons on the void goemetry is presented, along with theoretical models to explain some of these experimental findings. Strong interactions between the different plasmon modes as well as other mixing processes are identified. Understanding such plasmonic crystals allows for the engineering of devices tailored for a wide range of sensing application
Plasmon polaritons of metallic nanowires for controlling submicron propagation of light
Abstract: The optical resonances of individual plasmonic dimer antennas are investigated using confocal darkfield spectroscopy. Experiments on an array of antennas with varying arm lengths and interparticle gap sizes show large spectral shifts of the plasmon modes due to a combination of geometrical resonances and plasmon hybridization. The resonances of the coupled-dimer antennas are considerably broadened compared to those of single nanorods, which is attributed to a superradiant damping of the coupled antenna modes. The scattering spectra are compared with electrodynamic model calculations that demonstrate both the near-field and far-field characteristics of a half-wave antenna
Penetration of CdSe/ZnS quantum dots into differentiated vs undifferentiated Caco-2 cells
Localised and delocalised plasmons in metallic nano-voids
Nanostructured metal films comprised of periodically arranged spherical voids are grown by electrochemical deposition through a self-assembled template. Detailed measurements of the angle- and orientation-dependent reflectivity for different sample geometries reveal the spectral dispersion of several different types of surface plasmon modes. The dependence of the energies of both delocalized Bragg and localized Mie plasmons on the void goemetry is presented, along with theoretical models to explain some of these experimental findings. Strong interactions between the different plasmon modes as well as other mixing processes are identified. Understanding such plasmonic crystals allows for the engineering of devices tailored for a wide range of sensing application
Ultrafast Vibrations of Gold Nanorings
We investigate the vibrational modes of gold nanorings on a silica substrate with an ultrafast optical technique. By comparison with numerical simulations, we identify several resonances in the gigahertz range associated with axially symmetric deformations of the nanoring and substrate. We elucidate the corresponding mode shapes and find that the substrate plays an important role in determining the mode damping. This study demonstrates the need for a plasmonic nano-optics approach to understand the optical excitation and detection mechanisms for the vibrations of plasmonic nanostructures
Whispering gallery mode emission at telecommunications-window wavelengths using PbSe nanocrystals attached to photonic beads
We report the selective chemical attachment of infrared emitting PbSe nanocrystal quantum dots onto micron-scale glass photonic beads. Upon optical excitation, photoluminescence from the shell of nanocrystals is seen to couple into the high-Q 'whispering gallery' modes of the bead via the evanescent optical field, resulting in a series of sharp peaks being observed at wavelengths of around 1550 nm. Theoretical modelling gives a close agreement with the data for angular modes corresponding to l ~ 120. This work demonstrates the potential of narrow-bandgap II–VI semiconductor nanocrystals for use in a wide range of telecommunications-window photonics applications
Ultrafast Vibrations of Gold Nanorings
We investigate the vibrational modes of gold nanorings on a silica substrate with an ultrafast optical technique. By comparison with numerical simulations, we identify several resonances in the gigahertz range associated with axially symmetric deformations of the nanoring and substrate. We elucidate the corresponding mode shapes and find that the substrate plays an important role in determining the mode damping. This study demonstrates the need for a plasmonic nano-optics approach to understand the optical excitation and detection mechanisms for the vibrations of plasmonic nanostructures
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