Enhancement Of Lanthanide Fluorescence By Carbon Dots

As a new kind of carbon nanomaterials, carbon quantum dots (C-dots) have several advantages including stable fluorescence and outstanding resistance to photo-bleaching. Moreover, C-dots have extremely efficient light absorption throughout a wide spectrum. Therefore C-dots have received great attentions in the fields of biological sensing, medical imaging and light-emitting diodes. On the other hand, lanthanide ions (Ln3+) possess large Storks shift, sharp emission and long lifetime, allowing using time-resolved fluorescence techniques to obtain high signal-to-noise ratio. However, the emission of Ln ions is weak, in most occasions; organic ligands have to be used to enhance their luminescence, which often limits the applications of lanthanide-based emissions.In this paper, the combination of C-dots and Tb ion was taken as a main research. We studied the enhancement of C-dots to the lanthanide luminescence. We prepared new lanthanide-doped C-dots nanocomposites and established their fluorescence analysis methods. The main contents are summarized as follows:1. C-dots enhanced luminescence of Tb3+We used polyethylene glycol as a raw material to prepare hydroxyl-rich C-dots by hydrothermal reaction. The prepared C-dots have good dispersibility, uniform shape and excellent optical properties. Then we prepared a Tb3+-doped C-dots nanomaterial by using Tb3+ions and the C-dots above. We found the enhancement of Tb3+luminescence by C-dots and the fluorescence resonance energy transfer from C-dots to Tb3+. We discussed the mechanism of the fluorescence enhancement, and designed a fluorescence assay for ATP on the basis of the C-dots enhanced luminescence of Tb3+. This result lays the groundwork for the applications of C-dots enhanced luminescence of lanthanide ions.2. C-dots enhanced photoinduced-electron-transfer (PET)Photoinduced electron transfer (PET) is one kind of common mechanism of fluorescent sensings. It has been widely used in the design of various fluorescent sensors.Using the interaction between tryptophan-dipicolinic acid-Tb3+(Trp-DPA-Tb3+) and Hg2+ as a photoinduced electron transfer system, we studied the effect of C-dots to the system and prepared C-dots doped C-dot-Trp-DPA-Tb3+ nanocomposite. The photoinduced electron transfer in C-dot-Trp-DPA-Tb3+ was found 30 times stronger. We also used the C-dots enhanced C-dot-Trp-DPA-Tb3+ to detect Hg2+. The detection limit reached 0.1 nM, which is lower than most fluorescence methods. This result has important significance to various fluorescence analyses based on the PET effects.