Publications (5)0 Total impact
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ABSTRACT: Absorption and photoluminescence excitation (PLE) spectra were recorded for colloidal CdSe quantum dots of different sizes. No significant deviation between the PLE and the absorption spectra, provided appropriate corrections and sample treatment are made were found. This implies that there is no intrinsic wavelength dependence of the luminescence quantum yield, in line with the ultrafast intraband relaxation processes reported in the literature. Probably a possible source for the deviations reported in the literature is the scattering produced by aggregates formed of nanodots and org. ligands in as-prepd. colloidal solns. [on SciFinder (R)]
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ABSTRACT: The (sub)-ps relaxation processes in PbSe quantum dots of different sizes were measured by near-IR luminescence upconversion. The early-time spectra are characterized by emission from several low-lying excited states. The direct measurement of the Huang-Rhys factors of the lowest excited states excludes strong electron-phonon coupling in the intraband relaxation. The kinetics point to a fast sequential cascade process between excited states, governed by energy gaps and a quasicontinuous valence-band structure.
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ABSTRACT: The authors used light to transform a colloidal soln. of spherical silver nanoparticles into larger nanoparticles of a different shape. The particle size and shape can be controlled by choosing the wavelength(s) of light used to drive the photochem. growth. These findings suggest a new way of thinking about growth of nanoparticles in soln. and show the exciting possibility that light can be used as a major control parameter in metallic nanoparticle growth reactions. [on SciFinder (R)]
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ABSTRACT: We present ultrafast pump-probe studies on chem. prepd. CdSe nanocrystals. Upon pulsed optical excitation we find pronounced oscillations, indicating strong coupling to a LO phonon mode. From the polarization dependence of the signal addnl. information about the very first coherent events of exciton dynamics is obtained. The obsd. anisotropy behavior suggests strongly driven dynamics and rapid coherent motion. [on SciFinder (R)]
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ABSTRACT: The temp. dependence of the absorption and fluorescence spectra of colloidal CdSe nanocrystals was compared for three different shapes (dots, rods, and tetrapods) at 4-300 K. While the shift of the fluorescence max. indicates little dependence on the shape, the broadening of the emission spectrum behaves very differently for dots and rods, indicating major differences in the broadening mechanisms for different shapes. Tetrapods behave more similarly to dots, which suggests that the lowest exciton state is centered at the core. [on SciFinder (R)]
