The Carbon Dots-Based Fluorescence Turn-on Method For Biosensing

Carbon dots(CDots) are a kind of fluorescent nanomaterials, developed in recent years. Compared with traditional organic fluorchromes, CDots have unique optical properties, such as a relatively high fluorescence intensity and high photostability, as well as tunable excitation and emission spectra. Meanwhile, CDots have exhibited some advantages over widely used quantum dots, such as good biocompatibility, low toxicity, low molecular weight and small size. The superior optical properties show that CDots have potential applications for sensing and bioimaging fields.The major research works are as follow:(1) The methylene blue(MB), the malachite green(MG)and the crystal violet(CV) all can quench the fluorescence of CDots effectively. We have studied the change of the fluorescence of CDots, the change of CDots UV absorption, the quenching rate constant value of CDots and the fluorescence life of CDots when CDots solutions in the presence and absence of dyes, respectively. We have proved the methylene blue, the malachite green and the crystal violet quenched the fluorescence of CDots via static quenching processes.(2) We found that methylene blue caused an efficient quenching of the fluorescence of carbon dots. However, as ct-DNA was added, the fluorescence of CDots was restored reversibly. Under the experimental conditions, CDots were excellent electron donors. MB adsorbed on the surface of CDots and quenched the fluorescence of CDots through an electron-transfer process; and then the addition of DNA caused a restoration of the CDots fluorescence intensity, since DNA could bind with MB and remove it from the CDots. Based on this phenomenon, we developed a new system for DNA detection.(3) Cu2+can quench the fluorescence of CDots effectively. However, the fluorescence of CDots-Cu2+system restored reversibly in the presence of biothiol. Based on this phenomenon, we develop a new method for biothiols detection. This method offers good selectivity for detecting glutathione (GSH), cysteine (Cys). and homocysteine (Hcy) in the presence of amino acids and metal ions.