Simple Time-Resolved Fluorometer Based on a Nanosecond Digital Oscilloscope and a Diode-Pumped, Solid-State Laser

Abstract

A simple time-resolved fluorometer is constructed with an all-solid-state-based, frequency-tripled, Q-switched, diode-pumped Nd:YLF laser as the excitation source. Signal processing is accomplished with a digital oscilloscope. Simplicity of operation and applicability to trace analysis and in time-resolved spectroscopy are demonstrated with this new instrument. The laser produces 2.5-ns pulses at 349 nm and is capable of kilohertz repetition rates. For every shot of the laser, the oscilloscope collects an entire fluorescence decay at a 1-ns digitizer resolution and can average these data at the maximum laser repetition rate. When one is operating at 1 kHz and signal averaging for one second, detection limits (S/N = 3) in the 10–100 pM region are obtained. Excited-state decays are collected for several enzymatic probes and quinine sulfate, providing lifetimes consistent with those obtained by established instruments.