The series photodetector frequency circuit system with ITO–Si metal–semiconductor–metal photodetector for linearity improvement in Hex fluorescence concentration detection of DNA probe

The 48 MHz series photodetector frequency circuit system with ITO–Si metal–semiconductor–metal photodetector was developed for frequency sensitivity and detection linearity improvement in Hex fluorescence detection of DNA probe U1392. In accordance with derived theory of series photodetector frequency circuit system, the circuit parameters such as Cp and A (tan θ) can be applied to improve the frequency sensitivity for detection of fluorescence dye concentration. In this research, the lower capacitance of ITO–Si metal–semiconductor–metal photodetector (Cp) was made and selected to improve the frequency sensitivity. And the higher A was also adjusted to improve the frequency sensitivity. In the optimal parameter conditions of Cp and A, the detection limit of U1392-Hex fluorescence dye concentration 3.3 pmol/L can be measured by 48 MHz sensor system. The frequency method showed that the frequency sensitivity of sensor system was improved and the detection limit of U1392-Hex fluorescence dye concentration was lower than conventional fluorescence technique by 2–3 orders. The experimental result also indicated that the detection linearity of sensor system was improved and the frequency shift ΔF was linearly related to the logarithm of fluorescence dye concentration in the range 3.3 pmol/L–33.3 μmol/L.