Ratiometric Fluorescence Detection of DNA Based on the Inner Filter Effect of Ru(bpy)(2)(dppx)(2+) toward Silicon Nanodots

[Image: see text] A ratiometric DNA sensor was developed based on fluorescent silicon nanodots (SiNDs) and Ru(bpy)(2)(dppx)(2+). The absorption spectrum of Ru(bpy)(2)(dppx)(2+) has significant overlap with both the excitation and emission spectra of SiNDs. Therefore, fluorescence quenching of Ru(bpy)(2)(dppx)(2+) 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)(2)(dppx)(2+) and DNA. Fluorescence turn-on detection of DNA can be performed employing Ru(bpy)(2)(dppx)(2+) and SiNDs as the response and reference signals, respectively. Using SiND–Ru(bpy)(2)(dppx)(2+), a convenient, sensitive, rapid, and precise method could be developed for DNA detection. In aqueous solutions, the I(601)/I(448) fluorescence intensity ratio of SiND–Ru(bpy)(2)(dppx)(2+) 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, n = 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%.