Abstract
Pyrolytic conversion of biomass stands as one of the most promising sustainable routes to carbon-based nanostructures, including carbon dots (CDs). Yet, molecular composition of functionalized carbon dots is limited to heteroatom doping and the incorporation of few single metal precursors. Besides, most of these modifications were undertaken by strenuous post-grafting procedures, requiring organic solvents for carbon dispersion and excluding a large library of potential reactants because of incompatible experimental conditions. In a significant divergence from the well-established literature, we herein disclose an innovative and highly versatile approach for enriching carbon dot functionalities. This straightforward method merges chitosan as carbon precursor and metal alkoxide as ceramic precursor and explores a twin growth of two dissimilar "metal oxide@carbon dots" phases through hydrothermal conversion of the carbohydrate solution. Owing to the structure-directing effect of chitosan toward metal alkoxide precursors, a set of crystalline metal oxides including titanium dioxide, germanium oxide, and iron oxide clusters were intimately fused within the in situ formed nitrogen-containing carbon framework. Distinctively, the following approach uses water as solvent and renewable biomass as carbon source and is expected to shed light on the hidden talent of discarded bio-waste for engineering functional nanomaterials.