Ratiometric Fluorescence Detection of DNA Based on the Inner Filter Effect of Ru(bpy)(dppx) toward Silicon Nanodots.

A ratiometric DNA sensor was developed based on fluorescent silicon nanodots (SiNDs) and Ru(bpy)(dppx). The absorption spectrum of Ru(bpy)(dppx) has significant overlap with both the excitation and emission spectra of SiNDs. Therefore, fluorescence quenching of Ru(bpy)(dppx) toward SiNDs can occur on account of the strong inner filter effect. The effect of quenching is not influenced by the specific binding between Ru(bpy)(dppx) and DNA. Fluorescence turn-on detection of DNA can be performed employing Ru(bpy)(dppx) and SiNDs as the response and reference signals, respectively. Using SiND-Ru(bpy)(dppx), a convenient, sensitive, rapid, and precise method could be developed for DNA detection. In aqueous solutions, the / fluorescence intensity ratio of SiND-Ru(bpy)(dppx) increases linearly in the DNA concentration range of 20-1500 nM. The limit of detection and precision of the method is 4.3 nM and 3.5% (50 nM, = 13), respectively. The ratiometric sensor was tested for visual detection of trace DNA. Moreover, this method was found suitable for the ratiometric detection of DNA in a simulated sample and a human serum sample, and the recoveries were in the range of 98-119%.