Frequency sensitivity analysis of series photodetector frequency circuit system using circuit parameters of quartz crystal

The 48 MHz series photodetector frequency circuit systems matched with different quartz crystals were developed for frequency sensitivity analysis. In accordance with derived theory of series photodetector frequency circuit system, the circuit parameters of quartz crystal such as Rq and Cq can be applied to improve the frequency sensitivity. On the basis of parameter adjustment, the quartz crystal with proper Rq and Cq was selected to improve the frequency sensitivity of fluorescence detection. In the optimal conditions of Rq and Cq, the detection limit of U1392-Hex fluorescence dye concentration 3.3 pmol/L can be measured by 48 MHz sensor system. Moreover, the frequency method showed that the detection limit of U1392-Hex fluorescence dye concentration was lower than the conventional fluorescence technique by 2–3 orders. The result also indicated that the frequency shift ΔF was linearly related to the logarithm of fluorescence dye concentration in the range 3.3 pmol/L–3.3 μmol/L.