Water-soluble carbonized polymer dots with tunable solid- and dispersion-state fluorescence for multicolor films, anti-counterfeiting, and fungal imaging

Abstract

Water-soluble carbonized polymer dots (CPDs) with both superior solid/aggregation-state fluorescence (SSF) and dispersion-state fluorescence (DSF) are highly desired for biological, optoelectronic, and information safety applications due to their quenching-resistance and low toxicity. In this study, three matrix-free silicon-, europium/silicon-, and terbium/silicon-doped CPDs (Si-CPDs, Eu/Si-CPDs, and Tb/Si-CPDs) possessing favorable powder white SSF and aqueous concentration-dependent DSF were achieved by introducing the unique structures of sp2/sp3-hybridized carbon cores with abundant surface N, O, Si-related functional groups and polymer chains through one-step hydrothermal synthesis. The participations of Eu3+ and Tb3+ salts in the synthesis bestowed the corresponding Eu/Si-CPDs and Tb/Si-CPDs with higher graphitic N, accompanied by the red-shifted SSF and DSF emissions. Nevertheless, compared with Si-CPDs, Eu/Si-CPDs with ultratrace Eu (<0.001%) showed stronger powder photoluminescence quantum yield but weaker solution ones, while Tb/Si-CPDs with 0.96% Tb had both weaker powder and solution ones, suggesting the occurrence of electron transfer from CPDs to Eu3+ in dispersion state. The three CPDs solutions exhibited red-shifted luminescence from the cooperative carbon core and sub-fluorophores to the surfaces with their concentrations ranging from 1 to 200 mg/mL, causing the turning on of pale-yellow ice SSF. Interestingly, Si-CPDs, Eu/Si-CPDs, and Tb/Si-CPDs films, formed from their solutions, presented unprecedented multicolor SSF from blue to red, initiated by CPDs skeletons and trace Eu3+/Tb3+, through modulating the excitation wavelength. Importantly, these advanced merits successfully expanded the applications of as-prepared CPDs in anti-counterfeiting and pathogenic fungi detection, affording a new perspective for designing versatile quenching-resistant optical materials.