Professor Robert Taylor

Abstract:

We present a series of fullerene derivatives and a study on their photoluminescence properties, complete with their efficiency as singlet oxygen generation photosensitizers. We demonstrate the intramolecular charge transfer between pyrene donor and fullerene acceptor. The opposite effect in decay lifetime measurements is observed for the mono and bis adducts of C60 and C70 for the first time, indicating an interplay between charge-separation and locally excited states. A monoexponential decay was observed for the mono adduct of C60 and the bis adduct of C70, while a biexponential decay was observed for the bis adduct of C60 and the mono adduct of C70. The effect of these molecules as sensitizers of the singlet oxygen radical was tested using detailed 3D excitation photoluminescence maps. A quenching of the singlet oxygen for the C60-mono and C70-bis adducts was observed while a strong photosensitizing effect was observed for the C60-bis and C70-mono adducts.

Abstract:

We report on the realisation of ultra-small-modevolume tunable dye lasers based on hemispherical open microcavities. The cavity mode volume is of the order of cubic micrometers, such that self-diffusion of the dye molecules allows continuous wave operation over several minutes without the need for driven circulation. Such micro lasers could be integrated into lab-on-a-chip devices. A rate-equation model that incorporates the diffusion mechanism is used to predict the effect of the microcavity parameters on the lasing threshold.

Abstract:

We report on the realisation of ultra-small-mode-volume tunable dye lasers based on hemispherical open microcavities. The cavity mode volume is of the order of cubic micrometers, such that self-diffusion of the dye molecules allows continuous wave operation over several minutes without the need for driven circulation. Such micro lasers could be integrated into lab-on-a-chip devices. A rate-equation model that incorporates the diffusion mechanism is used to predict the effect of the microcavity parameters on the lasing threshold.

Abstract:

We investigate nontrivial surface effects on the optical properties of self-assembled crystalline GaN nanotubes grown on Si substrates. The excitonic emission is observed to redshift by ∼100 meV with respect to that of bulk GaN. We find that the conduction band edge is mainly dominated by surface atoms, and that a larger number of surface atoms for the tube is likely to increase the bandwidth, thus reducing the optical bandgap. The experimental findings can have important impacts in the understanding of the role of surfaces in nanostructured semiconductors with an enhanced surface/volume ratio.