Characterization of the interaction of a mono-6-thio-β-cyclodextrin-capped CdTe quantum dots–methylene blue/methylene green system with herring sperm DNA using a spectroscopic approach

摘要

Novel,water-soluble CdTe quantum dots (QDs) cappedwith β-cyclodextrin (β-CD) and ~ 4.0 nmin diameter were synthesized in aqueous solution, and characterized using transmission electron microscopy (TEM). A fluorescence-sensing system based on the photoinduced electron transfer (PET) of (mono-6-thio-β-CD)–CdTe QDs was then designed to measure the interaction of phenothiazine dyes [methylene blue (MB) and methylene green (MG)]with herring spermDNA (hsDNA). This fluorescencesensing systemwas based on a fluorescence “OFF–ON” mode. First,MB/MG adsorbed on the surface of (mono-6-thio-β-CD)–CdTe QDs effectively quenches the fluorescence of (mono-6-thio-β-CD)–CdTe QDs through PET. Then, addition of hsDNA restores the fluorescence intensity of (mono-6-thio-β-CD)–CdTe QDs, because hsDNA can bind with MB/MG and remove it from the asprepared (mono-6-thio-β-CD)–CdTe QDs. In addition, detailed reaction mechanisms of the (mono-6-thio-β-CD)–CdTe QDs–MB/MG–hsDNA solution system were studied using optical methods, by comparison with the TGA–CdTe QDs–MB/MG–hsDNA solution system.