Time-gated detection of europium nanoparticles in a microchannel-based environmental immunoassay

Abstract

Using MEMs (Micro Electro Mechanical system) fabrication techniques, it is possible make a micro-sized instrument for optical detection of trace amounts of chemical species in aqueous solutions. The redemitting Eu 2 O 3 nanoparticle is suitable for a biolabel for such species because of its long fluorescence lifetime and narrow emission bandwidth. The europium nanoparticles are excited by a laser pulse. Their long-lived emission allows the detected signal to be separated from the laser pulse both spectrally and temporally. The background signal can also be eliminated in this manner. The instrument we present, is assembled with silicon and glass layers with a 200μm deep channel. A Nd:YAG pumped optical parametric oscillator (OPO) is used as the excitation source. The measurement sensitivities using two detectors, a PMT (Photo Multiplier Tube) and an APD (Avalanche Photodiode), are compared. The underlying fundamental principles and the micro-fabrication steps for the instrument and detection are discussed.