Now showing 1 - 3 of 3
No Thumbnail Available
Publication

Efficient Quenching of TGA-Capped CdTe Quantum Dot Emission by a Surface-Coordinated Europium(III) Cyclen Complex

2013-03-25, Gallagher, Shane A., Comby, Steve, Wojdyla, Michal, Quinn, Susan J., et al.

Extremely efficient quenching of the excited state of aqueous CdTe quantum dots (QDs) by photoinduced electron transfer to a europium cyclen complex is facilitated by surface coordination to the thioglycolic acid capping ligand. The quenching dynamics are elucidated using steady-state emission and picosecond transient absorption.

No Thumbnail Available
Publication

Synthesis and spectroscopic studies of chiral CdSe quantum dots

2010-08, Gallagher, Shane A., Moloney, Mícheál P., Wojdyla, Michal, Quinn, Susan J., Kelly, John M., Gun'ko, Yurii K.

Using microwave irradiation, water soluble, optically active, penicillamine (Pen) capped CdSe nanocrystals with broad spectral distribution (430-780 nm) of photoluminescence have been produced and studied by a range of instrumental techniques including absorption, circular dichroism and both steady state and time resolved photoluminescence spectroscopy. The photoluminescence of these nanocrystals is attributed to emission from surface defect states. The decay of the excited state in the nanosecond region, which can be analysed as a triple exponential, depends strongly on the emission wavelength selected, but only weakly on the excitation wavelength.

No Thumbnail Available
Publication

Photophysical studies of CdTe quantum dots in the presence of a zinc cationic porphyrin

2012-09-24, Keane, Páraic M., Gallagher, Shane A., Magno, Luís M., Leising, Miriam J., Clark, Ian P., Greetham, Gregory M., Towrie, Michael, Gun'ko, Yurii, Kelly, John M., Quinn, Susan J.

The photophysical properties of 2.3 nm thioglycolic acid (TGA) coated CdTe quantum dots (QDs) prepared by a reflux method have been studied in the presence of cationic meso-tetrakis(4-N-methylpyridyl) zinc porphyrin (ZnTMPyP4). Addition of the CdTe QDs to the porphyrin in H2O results in a marked red-shift and hypochromism in the porphyrin absorption spectrum, indicative of a non-covalent binding interaction with the QD surface. Only low equivalents of the quantum dot were required for complete quenching of the porphyrin fluorescence revealing that one quantum dot may quench more than one porphyrin. Similarly addition of porphyrin to the quantum dot provided evidence for very efficient quenching of the CdTe photoluminescence, suggesting the formation of CdTe'porphyrin aggregates. Definitive evidence for such aggregates was gathered using small angle X-ray spectroscopy (SAXS). Ultrafast transient absorption data are consistent with very rapid photoinduced electron transfer (1.3 ps) and the resultant formation of a long-lived porphyrin species.