A compact, highly specific, inexpensive and user friendly optical fibre laser-induced fluorescence (LIF) sensor based on fluorescence quenching by nanoparticles has been developed to detect single-strand (ss-) DNA hybridization at femtomolar level. The fluorescence of fluorophore-tagged ss-DNA increases by a factor of 80 when it binds to a complimentary DNA, while the addition of single-base mismatch DNA had no effect on the fluorescence efficiency. We present theoretical and experimental results on dye fluorescence quenching induced by gold nanoparticles having different particle sizes. Fluorescence spectra clearly show that the quenching efficiency decreases with increasing size of the gold nanoparticles and increasing the distance between dye and nanoparticles. The mechanism of size- and distant-dependent fluorescence quenching has been discussed. Effects of various influential experimental parameters and configurations were investigated in order to optimize and miniaturize the sensor performance.

No abstract

No abstract

Persistent hole burning is observed in a europium doped sodium borate glass from 10 to 100 K. Hole burning efficiency increased 18× when 5% yttrium oxide was added to the glass mixture. Hole burning was observed up to 300 K in Eu3+, Y3+ Co-doped glass.

Persistent spectral hole burning has been observed in europium-doped sodium germanate glass. Hole-burning efficiency increased by 85% when the glasses were made in a reduced atmosphere, and hole burning was detected even at room temperature. There is evidence for photochemical as well as photophysical hole-burning mechanisms.