Guangzhou Hu

Humic acids (HAs) are widely used as adsorbents or carriers, yet they still lack oxygenic functional groups under certain conditions. Modification via catalytic oxidation under mild conditions is an ideal method to increase the oxygenic functional groups in HAs—if simple catalyst separation could be realized. Here, we report the use of CuO nanoparticles supported by Fe₃O₄ magnetic nanospheres as magnetic catalytic systems (MCSs) that could catalyze HA modification via Fenton oxidation. These MCSs can be easily magnetically separated from the products. The content of carboxyl groups increased from 2.45% to 10.47% after reaction, while the yield of modified HAs remained approximately 100%. These results indicate that oxidation with MCSs could be a potential method for HA modification.

Carbon dots have attracted widespread attention due to their excellent optical properties and so on and are therefore used in various fields such as anti‐counterfeiting. There are many reports on carbon dot‐based room‐temperature phosphorescent materials, but there are still fewer reports on carbon dot‐based room‐temperature phosphorescent materials with time‐dependent color‐changing properties. In this work, a time‐dependent color‐changing carbon dot‐based room‐temperature phosphorescent material with the ability to change from green to blue was successfully prepared by a simple one‐pot heating method using hydroxyurea as the only raw material. In this process, hydroxyurea is used as both a carbon and nitrogen source, and in the process of material formation, hydroxyurea also partially forms cyanuric acid as a matrix to make the carbon dots uniformly dispersed in it. By blending the ratio of the dual emission centers of the carbon dots themselves, the final effect of time‐dependent color‐changing is achieved by taking advantage of the intensity changes and color differences of each emission center. The present work provides new ideas for the preparation of time‐dependent color‐changing carbon dot‐based room‐temperature phosphorescent materials.