105,883 research outputs found
Gate-induced blueshift and quenching of photoluminescence in suspended single-walled carbon nanotubes
Gate-voltage effects on photoluminescence spectra of suspended single-walled
carbon nanotubes are investigated. Photoluminescence microscopy and excitation
spectroscopy are used to identify individual nanotubes and to determine their
chiralities. Under an application of gate voltage, we observe slight blueshifts
in the emission energy and strong quenching of photoluminescence. The
blueshifts are similar for different chiralities investigated, suggesting
extrinsic mechanisms. In addition, we find that the photoluminescence intensity
quenches exponentially with gate voltage.Comment: 4 pages, 4 figure
Photoluminescence upconversion at GaAs/InGaP2 interfaces driven by a sequential two-photon absorption mechanism
This paper reports on the results of an investigation into the nature of photoluminescence upconversion at
GaAs/InGaP2 interfaces. Using a dual-beam excitation experiment, we demonstrate that the upconversion in our
sample proceeds via a sequential two-photon optical absorption mechanism. Measurements of photoluminescence
and upconversion photoluminescence revealed evidence of the spatial localization of carriers in the InGaP2
material, arising from partial ordering of the InGaP2. We also observed the excitation of a two-dimensional electron
gas at the GaAs/InGaP2 heterojunction that manifests as a high-energy shoulder in the GaAs photoluminescence
spectrum. Furthermore, the results of upconversion photoluminescence excitation spectroscopy demonstrate that
the photon energy onset of upconversion luminescence coincides with the energy of the two-dimensional electron
gas at the GaAs/InGaP2 interface, suggesting that charge accumulation at the interface can play a crucial role in
the upconversion process
Band structure and optical properties of germanium sheet polymers
The band structure of H-terminated Ge sheet polymers is calculated using density-functional theory in the local density approximation and compared to the optical properties of epitaxial polygermyne layers as determined from reflection, photoluminescence, and photoluminescence excitation measurements. A direct band gap of 1.7 eV is predicted and a near resonant excitation of the photoluminescence is observed experimentally close to this energy
Comparison of the photoluminescence properties of semiconductor quantum dots and non-blinking diamond nanoparticles. Observation of the diffusion of diamond nanoparticles in living cells
Long-term observations of photoluminescence at the single-molecule level were
until recently very diffcult, due to the photobleaching of organic ?uorophore
molecules. Although inorganic semiconductor nanocrystals can overcome this
diffculty showing very low photobleaching yield, they suffer from
photoblinking. A new marker has been recently introduced, relying on diamond
nanoparticles containing photoluminescent color centers. In this work we
compare the photoluminescence of single quantum dots (QDs) to the one of
nanodiamonds containing a single-color center. Contrary to other markers,
photoluminescent nanodiamonds present a perfect photostability and no
photoblinking. At saturation of their excitation, nanodiamonds
photoluminescence intensity is only three times smaller than the one of QDs.
Moreover, the bright and stable photoluminescence of nanodiamonds allows wide
field observations of single nanoparticles motion. We demonstrate the
possibility of recording the tra jectory of such single particle in culture
cells
Photoluminescence of nanocrystals embedded in oxide matrices
We used the theory of finite periodic systems to explain the
photoluminescence spectra dependence on the average diameter of nanocrystals
embedded in oxide matrices. Because of the broad matrix band gap, the
photoluminescence response is basically determined by isolated nanocrystals and
sequences of a few of them. With this model we were able to reproduce the shape
and displacement of the experimentally observed photoluminescence spectra.Comment: 4 pages, 3 figure
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