Chapter 1: This chapter briefly outlined the preparation and optical properties of CQDs,and sensing applications of CQDs,and reviewed their research development on applications in sensor.Chapter 2: Fluorescent carbon quantum dots(CQDs),witch exhibited an obvious bright blue color under UV light(365nm),were synthesized by a green and economical one-step solvo-waterthermal method using banana as carbon source.The products were characterized by X-ray diffraction(XRD),transmission electron microscopy(TEM),Fouri...