A facile and high sensitive micro fluorimeter based on light emitting diode and photodiode

A facile and high sensitive micro fluorimeter was developed and evaluated. It employed light emitting diode (LED) as light source, cuvette as detection cell, and photodiode (PD) as optoelectronic detector. Optical and electronic parameters were optimized and demonstrated. A high power LED was chosen, which could irradiate the inner area of the cuvette completely at the same time with divergence angle as small as possible. The optimum LED brought 2.5 times signal-to-noise ratio (SNR) enhancement. Using reflector at the opposite direction of excitation light path doubled SNR. The amplifier circuit of PD was deeply investigated to achieve high sensitivity, low noise, and good stability. The limit of detection (LOD) of fluorescein isothiocyanate (FITC) and chlorophyll at SNR = 3 were 10 pM similar to 0.004 ppb and 0.05 ppb, respectively. Basing on the principle structure, a portable fluorimeter for fungimycin detection was developed using a low power DV LED as light source. The LOD for aflatoxin B1 was 0.1 ppb.