The preparation of carbon dots (CDs) from waste fish scales is an attractive and high-value transformation. In this study, fish scales were used as a precursor to prepare CDs, and the effects of hydrothermal and microwave methods on their fluorescence properties and structures were evaluated. The microwave method was more conducive to the self-doping of nitrogen due to rapid and uniform heating. However, the low temperature associated with the microwave method resulted in insufficient dissolution of the organic matter in the fish scales, result...