Abstract: In this paper we described the construction of a novel dual fluorescent film sensor using fluorescent dye Acridine Orange(AO) as an internal standard and CdTe as a fluorescent probe. Poly-sodium-4-styrenesulfonate(PSS) and Chitosan(CS) were respectively assembled between AO and CdTe. The constructed selfassembly multilayers, Quartz/APES/PSS/AO/PSS/CS/CdTe, emits dual fluorescence at 600 and 530 nm, respectively. AO is shielded effectively by the assembled PSS and CS and thus its fluorescent intensity I₁ doesn’t change with the variation of the analyte concentration, thereby acting as an internal standard to provide reference signal. The ratio of dual fluorescence intensities of the thus constructed film sensor is not affected by the variations of the external environment factors such as excitation intensity and sensor position in the cell holder. A good linear relationship was found between dual fluorescence intensity ratio and DNA concentration over 0—250 ng/L. Quartz/APES/PSS/AO/PSS/CS/CdTe film is capable of an extremely highly sensitive detection for DNA with a detection limit of 6.6 ng/L. The analysis based on dual fluorescent self-assembled multilayers bearing a fluorescent internal standard would greatly improve the detection accuracy.

Key words: Fluorescent internal standard, Dual fluorescence, Self-assembled multilayer film, Interfacial sensor, CdTe, Acridine orange