Valorization of cellulose pulp derived carbon quantum dots by controllable fractionation

Fabrication and valorization of carbon quantum dots from lignocellulosic biomass is of significant importance. Herein, this study presents a simple and controllable route to prepare nitrogen and phosphorus co-doped CQDs (N,P-CQDs) in a one-pot synthesis from cellulose pulp. The subsequent fractionation based on molecular weight yielded three fractions of N,P-CQDs, i.e., N,P-CQDs-3500, N,P-CQDs-1000, and N,P-CQDs-500. The characteristics of each fraction N,P-CQDs were comprehensively evaluated. The fractionation endowed each fraction of N,P-CQDs with unique and different properties. The results showed that the resultant of N,P-CQDs were explored as a probe for pH detection, metal ions detection, and cell imaging. N,P-CQDs-500 exhibited unique selectivity towards Fe(II), which is novel and of importance in the biological process. The N,P-CQDs-1000 is sensitive to pH and has the potential to be a pH probe. The N,P-CQDs-3500 showed excellent bio-imaging ability in five cancer cells, and different performance on suspension and adherent cells. This study will not only help to expand the applications of lignocellulosic biomass for preparing CQDs, but also help to achieve upgrading of cellulose pulp into a high value-added product.