Methods in optical oxygen sensing: protocols and critical analyses.

We study light absorption mechanisms in semiconducting carbon nanotubes using low-temperature, single-nanotube photoluminescence excitation spectroscopy. In addition to purely electronic transitions, we observe several strong phonon-assisted bands due to excitation of one or more phonon modes together with the first electronic state. In contrast with a small width of emission lines (sub-meV to a few meV), most of the photoluminescence excitation features have significant linewidths of tens of meV. All of these observations indicate very strong electron-phonon coupling that allows efficient excitation of electronic states via phonon-assisted processes and leads to ultrafast intraband relaxation due to inelastic electron-phonon scattering.

Luminescent Measurements↗

PubMed2005

Direct measurement of the singlet oxygen lifetime in zeolites by near-IR phosphorescence.

Time-resolved near-IR phosphorescence spectroscopy was employed to determine the lifetime of singlet oxygen in Y-zeolites and porous silica and it was found to depend strongly on the alumina content of the zeolite.

Luminescent Measurements↗

PubMed2005

Further analysis of delayed luminescence of plants.

The delayed luminescence curves of biological tissues, in particular the "hyperbolic" oscillations of the form exp(-iln (1 + lambda t)) with t as the time and lambda as a constant, were subjects of further experimental and theoretical investigations. It turned out that the oscillations are solutions of a Hamiltonian that keeps coherent states coherent. In agreement to the expectations the oscillations disappear as soon as the biological system looses its integrity or its collective structure. The photocount statistics (PCS) confirms these results. The illumination itself influences the biological state under consideration. The temperature dependence displays small deviations from the Arrhenius-law with a mean activation energy of about 0.5 eV in case of plants. The results may be useful for investigating supermolecular interactions as well as for assessing the quality or quality changes of biological tissues.

Luminescent Measurements↗