Abstract
Carbonized polymer dots (CPDs) have great potential for bioimaging and biosensing owing to their low toxicity, low cost, resistance to photobleaching, and low environmental impact. Here, the hydrothermal condensation of biomolecules (l‐serine and l‐tryptophan) is used to vary the CPDs' inner structure from amorphous to lattice. A new type of carbon lattice CPD is thus demonstrated that is bright (the photoluminescence quantum yield (PLQY) is as high as 89.57%) and shows room‐temperature ferromagnetism (RTFM), with the magnetic moment increasing from 0.0025 emu g−1 in crosslinked polymer clusters to 0.021 emu g−1 in the latticed sample. Hydrothermal synthesis at 300 °C leads to a distinct type of CPD with an obvious carbon lattice, which shows the highest PLQY and the greatest ferromagnetism. Then, the origin of the RTFM is examined in the CPDs via first‐principles calculation, revealing that graphitic nitrogen triggers RTFM in CPDs. Moreover, a possible growth mechanism is suggested that includes kinetics as an important factor in the formation of the CPD crystallites. Overall, these findings identify graphitic nitrogen and high crystallinity as crucial to the enhancement of the CPDs' photoluminescence and room‐temperature ferromagnetism which suggests that they deserve more research attention to develop practical applications.
Highlights
Heating at 100 °C for 8 h resulted in annular polymer dots with an average diameter of 20 nm, which were detectable by transmission electron microscopy (TEM) (Figure 1a)
Crosslinked polymer clusters, an amorphous carbon structure, and an obvious carbon lattice were achieved by altering the temperature in one synthesis system
As the presence of graphitic nitrogen and the level of crystallization increased, the CPDs’ PL and room-temperature ferromagnetism (RTFM) were strongly enhanced: the PL quantum yield (PLQY) reached a maximum of 89.57%, and the magnetic moment increased from 0.0025 to 0.021 emu g−1
Summary
(CPDs) comprising eco-friendly carbon materials have emerged as fluorescent materials that fill the gap between semiconductor quantum dots and organic fluorophores They have wide potential applicability in the fields of bioimaging, fluorescence sensors, and energy conversion due to their unique properties such as high water solubility, low toxicity, high optical and chemical stability, and flexibility of surface modification.[1,2] Various synthesis methods have led to CPDs with varying structures that show tunable properties that can fit many specific sible growth mechanism is suggested that includes kinetics as an important factor in the formation of the CPD crystallites.
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