Optimization of a UV light-emitting diode based fluorescence-phase sensor

Abstract

A set of UV light-emitting diodes (LEDs) with the peak wavelengths ranging from 255 nm to 375 nm was applied for the investigation of spectral and decay-time fluorescence signatures in dry <i>B. globigii </i>spores and common airborne interferants (albuminous, epithelium, and cellulosous materials as well as aromatic hydrocarbons). The fluorescence decay signature was represented by a phase shift of the sinusoidal fluorescence waveform in respect of excitation provided by high-frequency modulated LEDs. The obtained data matrix was used for the optimization a bioparticle fluorescence sensor with a minimized number of excitation sources and detection channels and maximized discrimination ability of bioparticles against common interferants. Based on the optimization, a new concept for a UV LED based "detect-to-warn" bioparticle fluorescence sensor is proposed. The sensor contains a single deep-UV LED emitting at 280 nm that is harmonically modulated at a high frequency (of about 70 MHz) and a dual-channel fluorescence detector with the spectral windows peaked at 320 nm and 450 nm. The output parameters of the sensor are the ratio of the fluorescence intensity in the two windows and the phase shift of the fluorescence waveform in the 320-nm detection channel in respect of the excitation one. Such a sensing scheme has a smaller number of optical components and a potentially higher discrimination ability of bioparticles against common interferants in comparison with the conventional approach based on just fluorescence intensity measurement under dual-wavelength excitation (280 nm and 340 nm).