Study on Ultrasonic Single-Step Synthesis and Optical Properties of Nitrogen-Doped Carbon Fluorescent Quantum Dots

Nitrogen doped carbon fluorescent quantum dots (NDCFDs) with downconversion fluorescent and upconversion fluorescence properties were prepared by an ultrasonic one-step process. The raw materials and reagents were inexpensive and easy to obtain. The effect of ultrasonic time and reaction temperature on the fluorescent quantum yield and particle size was study. Optimal preparation conditions of NDCFDs with the highest fluorescence quantum yield were achieved by employing a reaction time of 14 h at 50°C. NDFCDs were characterized by TEM, FTIR, Raman spectroscopy, XPS, UV spectrophotometer, and fluorescence spectrometer. The results showed that the surface of NDCFDs were rich in hydroxyl, carbonyl hydrophilic group, etc. The DNCFDs not only had downconversion fluorescent, but also had good upconversion fluorescence. The effect of concentration and type of solution on the fluorescence properties of NDCFDs was studied. The formation mechanism, fluorescence emission mechanism and self-assembly behavior of NDCFDs were also investigated.