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Abstract:

Photoluminescence spectroscopic measurements have allowed the acquisition of high resolution spectra at low temperature for the endohedral metallofullerenes, Er2 @ C82 (isomer I) and Er2 C2 @ C82 (isomer I). The characteristic emission in the 1.5-1.6 μm region corresponds to the ⁴ I13 / 2 (m) → ⁴ I15 / 2 (n) transitions of the Er^{3 +} ion for both molecules. The emission arising from Er2 C2 @ C82 (I) appears acuminated (narrow lines that taper to a point) when compared with that of Er2 @ C82 (I). The Er2 C2 @ C82 (I) emission linewidths are comparable to those found in crystals, making this molecule of interest for applications where accessible, well-defined quantum states are required. © 2009 Elsevier B.V. All rights reserved.

Abstract:

ZnO nanostructures attract current interest because they have the potential to implement cavity quantum electrodynamics at room temperature. We report a photoluminescence mapping of ZnO nanobelts both at room temperature and 4.2 K. The multicavity modes were observed all over the belt surface, which were induced by Fabry-Ṕrot interference. The emission from the belt surface is enhanced at both the ends and the sides of the belt, and is highly linearly polarized in the direction perpendicular to the long axis of the belt. The results are explained using finite-difference time-domain simulations. © 2009 American Institute of Physics.

Abstract:

With the aim of providing a thorough description of the optical properties of Er³⁺-doped endohedral fullerenes, we studied their characteristics in the light of those of well-known Er³⁺-doped β-PbF2 single-crystals. Various Er³⁺-doped endohedral fullerenes were considered: Er2C2@C82, where the Er2C2 group is encapsulated inside a cage of 82 carbon atoms and the Er3-xScxN@C80 (x = 0, 1 and 2) family, where the Er3N, Er2ScN and ErSc2N clusters are trapped in a 80 carbon atom cage. In this article, we discuss the absorption and photoluminescence of trivalent erbium ions in fullerenes and in β-PbF2 crystals. The extinction coefficient of Er3N@C80 was found to be 4.8 (±0.5) × 10³ mol/l^-1 cm^-1 at 540 nm, due to the C80 cage absorbance. Even in a saturated fullerene solution, the absorption of Er³⁺ encapsulated inside a C80 cage cannot be observed at room temperature. We suggest that this is due to an insufficient number of Er³⁺ ions in the solution and their low absorption cross-section. Low temperature photoluminescence measurements show that the line width of Er³⁺ in a carbon cage, dissolved in a polycrystalline solvent, is similar to the one of Er³⁺ in β-PbF2 single-crystals. The quantum efficiency of Er³⁺ at 1.5 μm in fullerenes is four orders of magnitude lower than that for Er³⁺ in crystals, due to very efficient non-radiative decay processes. Molecular vibrations of the cage might be responsible for those rapid non-radiative de-excitations. © 2009 Elsevier B.V. All rights reserved.