MHz LED source for nanosecond fluorescence sensing

• Published in: Measurement science & technology Vol. 13; no. 1; pp. 84 - 91
• Main Authors: O'Hagan, W J, McKenna, M, Sherrington, D C, Rolinski, O J, Birch, D J S
• Format: Journal Article
• Language: English
• Published: Bristol IOP Publishing 01.01.2002; Institute of Physics
• Subjects: Applied sciences; Biological and medical sciences; Electronics; Exact sciences and technology; Fluoroscopy; Instruments, apparatus, components and techniques common to several branches of physics and astronomy; Investigative techniques, diagnostic techniques (general aspects); Light-emitting devices; Medical sciences; Miscellaneous. Technology; Optical instruments, equipment and techniques; Optoelectronic devices; Physics; Radiodiagnosis. Nmr imagery. Nmr spectrometry; Semiconductor electronics. Microelectronics. Optoelectronics. Solid state devices; Lifetime; Resonance fluorescence; Resonant energy transfer; Nanosecond; Metal ion; Pulsed source; Light emitting diodes; Modelling; Sensitized fluorescence; Energy transfer; Excitation systems
• ISSN: 0957-0233; 1361-6501
• DOI: 10.1088/0957-0233/13/1/311

An inexpensive and portable pulsed LED source with variable repetition rate up to 10 MHz suitable for time-resolved fluorescence sensing in medical, environmental and industrial applications is described. The pocket-sized battery-driven source is pulsed by signals from a simple logic circuit, giving measured optical pulse widths of about 1.9 ns at 525 nm as recorded using time-correlated single-photon counting. Pulses are presented for three LEDs with peak emissions at 525, 560 and 590 nm. The measurement performance is illustrated by the fluorescence lifetime and anisotropy decay of rhodamine 6G in various solvents and a fluorescence resonance energy transfer (FRET) sensor for detecting metal ions in water which uses a new measurand, namely, the site distribution function rho(r) of metal ion acceptors accumulating in an anionic porous polymer with respect to the donor fluorophores. The rho(r) dependence reveals a minimum fluorophore-metal ion separation of about 7 A, which explains the selectivity of such FRET sensors in discriminating against other quenching mechanisms. (Author)