Abstract
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%.