The Preparation Of Carbon Quantum Dots Fluorescence Probe And Its Application For Heavy Metal Ions Analysis

Carbon quantum dots (CQDs),a kind of fluorescence probe, exhibit many advantages,such as high water solubility, robust chemical inertness, low cytoxicity, good biocompatibilityand high resistance to photobleaching. Hence, they have become the research hotspot inrecognition and detection of metal ions. But there are still some problems, for example theobtained CQDs do not show high fluorescence intensity or are not well functionalized,leading to low detection sensitivities and bad selectivities. Besides, the CQDs exist in theliquid and can not be used repeatedly, leading to the waste of cost and the secondary pollutionof environmental. To counter the problems above, this dissertation to work in two major areas,on the one hand, carbon quantum dots with cheap carbon soot as raw materials, weresynthesized and then the reduced carbon quantum dots (rCQDs) were grafted in calciumalginate(CA) to form a calcium alginate pore structure film (CA-rCQDs). It realizes theimmobilization of CQD. On the other hand, the CQDs were synthesized by using low-costethylene glycol as precursors and the fluorescence resonance energy transfer(FRET) systemwas fabricated by using CQDs and Rhodamine B(RhB). It realizes the more diverseapplications of CQDs with low fluorescence intensity. The specific research content asfollows:CQDs with cheap carbon soot as raw materials, were synthesized by the way of nitricacid oxidation and they were then reduced by sodium borohydride. The fluorescence probewas prepared by grafting rCQDs in calcium alginate to form a CA-rCQDs. Fluorescencecharacteristics of the probe and interaction between the probe and metal ions were studiedusing fluorescence spectrophotometer and Uv-vis spectrophotometer. The results showed thatthe fluorescence intensity of the novel probe was strong and varied with the concentration ofCu2+. In addition, it was found that the probe could detect Cu2+repeatedly by using EDTA.Moreover, the quenched fluorescence intensity of probe was linearly proportional to theconcentration of Cu2+in the range from5×10-6to100×10-6M. This method is not only suitable for the detection of Cu2+, also achieved the immobilization of CQDs, ensuring theprobe to be recycled and reused.The CQDs with uniform particle size and graphitic crystallinity were synthesized byusing low-cost ethylene glycol as precursors. The FRET system was fabricated by usingCQDs and RhB acted as fluorescence donor and fluorescence acceptor, respectively.Furthermore, effect of the concentration of both CQDs and RhB and the pH values on FRETwere studied, and then the optimum experiment conditions for FRET system were selected. Inaddition, the selectivity and sensitivity of the RhB-modified CQDs (RhB@CQDs) towardiron ion were investigated. None of metal ions except for Fe3+ions not only hindered FRETeffects between CQDs and RhB but also quenched photo-induced electrons at the highlyexcited state, resulting in enhancement of fluorescence quenching rates. The results provedthat the RhB@CQDs could be used as a fluorescence probe for the improved higher sensitiveand selective. Finally, the RhB@CQDs sensor could be potential in application of fastmonitoring corrosion process of iron devices and equipments.