ZHU Shi-yang, HUANG Shi-hua, CHEN Duo-jia, DENG Zhao-ru. Phase Modulation Method Based on First Harmonic of Fourier Series for Measuring Fluorescence Lifetime[J]. Chinese Journal of Luminescence, 2008,29(5): 897-900
ZHU Shi-yang, HUANG Shi-hua, CHEN Duo-jia, DENG Zhao-ru. Phase Modulation Method Based on First Harmonic of Fourier Series for Measuring Fluorescence Lifetime[J]. Chinese Journal of Luminescence, 2008,29(5): 897-900DOI:
A modified phase demodulation method for measuring nanosecond fluorescence lifetime is introduced in this paper.The method is based on phase modulation technique and Fourier analysis of both the excitation and the emission waveforms.Excitation light is modulated by an arbitrary periodic wave.Emission of the sample follows the excitation light
is also modulated and with a delay because of the fluorescence lifetime.In the modified method
the first harmonics of the Fourier series are figured out from the excitation and the emission waveforms.The lifetime can be obtained by the relationship same as in the ordinary phase modulation method from the phase difference between the first harmonics.A test system
composed of an oscilloscope
a spectroscope and an excitation light source
was designed and developed.An LED light source modulated by a crystal oscillator is built at an acceptable cost for the system.The emission and excitation are detected by a spectroscope
converted to electrical signal by a photomultiplier tube
digitalized by a digital oscilloscope
and then transmitted to a computer.Fluorescence lifetime is then obtained by Fourier analysis of the emission and excitation waveforms.The relationship between the optimized modulation frequency and the range of the measured lifetimes is discussed.The lifetime of cresyl violet ethanol solution(0.0033 mol/L) measured with this method is(4.03±0.87) ns which is comparable with that by a commercial equipment.