Abstract
Carbon dots (CDs) have been studied for years as one of the most promising fluorescent nanomaterials. However, CDs with red or solid-state fluorescence are rarely reported. Herein, through a one-pot solvothermal treatment, hydrophobic CDs (H-CDs) with blue dispersed emission and red aggregation-induced emission are obtained. When water is introduced, the hydrophobic interaction leads to aggregation of the H-CDs. The formation of H-CD clusters induces the turning off of the blue emission, as the carbonized cores suffer from π-π stacking interactions, and the turning on of the red fluorescence, due to restriction of the surfaces’ intramolecular rotation around disulfide bonds, which conforms to the aggregation-induced-emission phenomenon. This on-off fluorescence of the H-CDs is reversible when the H-CD powder is completely dissolved. Moreover, the H-CD solution dispersed in filter paper is nearly colorless. Finally, we develop a reversible two switch-mode luminescence ink for advanced anti-counterfeiting and dual-encryption.
Highlights
Carbon dots (CDs) have been studied for years as one of the most promising fluorescent nanomaterials
transmission electron microscopy (TEM), X-ray diffraction (XRD) and Raman spectra were taken to confirm the nature of the hydrophobic CDs (H-CDs) carbon nanoparticles
H-CDs was confirmed by X-ray photoelectron spectra (XPS), Fourier transform infrared (FT-IR) spectra and nuclear magnetic resonance (NMR)
Summary
Carbon dots (CDs) have been studied for years as one of the most promising fluorescent nanomaterials. CDs with red or solid-state fluorescence are rarely reported. The hydrophobic interaction leads to aggregation of the H-CDs. The formation of H-CD clusters induces the turning off of the blue emission, as the carbonized cores suffer from π-π stacking interactions, and the turning on of the red fluorescence, due to restriction of the surfaces’. Intramolecular rotation around disulfide bonds, which conforms to the aggregation-inducedemission phenomenon This on-off fluorescence of the H-CDs is reversible when the H-CD powder is completely dissolved. The currently accepted mechanism of this phenomenon is similar to the Haggregation of organic fluorescent molecules; CDs suffer from π–π stacking in the solid state and the aggregation of large conjugated systems consumes the transition energy, resulting in the quenching of the CDs’ fluorescence. Chen et al.[13] prepared N-doped
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