FRET-driven red phosphorescence in lignin carbon dots for stimuli-responsive encryption

Area of Science:

• Materials Science
• Organic Chemistry
• Nanotechnology

Background:

• Achieving long-wavelength red room-temperature phosphorescence (RTP) in carbon dots (CDs) is challenging due to the energy gap law, which limits quantum yield and lifetime.
• Biomass-derived CDs offer a sustainable platform, but red emission properties are difficult to attain.

Purpose of the Study:

• To develop a novel strategy for efficient long-wavelength red RTP in biomass-derived CDs.
• To overcome the limitations imposed by the energy gap law for red-emitting phosphors.
• To explore applications in optical anti-counterfeiting and sensing.

Main Methods:

• Synthesized yellow-emissive lignin-based CDs with high fluorescence quantum yield and millisecond phosphorescence lifetime via precursor design and nitrogen functionalization.
• Constructed a Förster resonance energy transfer (FRET) pair between CDs (donors) and a red-absorbing organic dye (acceptor) within a rigid polymer matrix.
• Utilized stimuli-responsive dynamic bonds for advanced material functionalities.

Main Results:

• Achieved intense red RTP centered at 584 nm with a long phosphorescence lifetime (>258.15 ms) by decoupling phosphor bandgap from triplet state stability.
• Demonstrated a general solution to bypass the energy gap law limitation for red-shifted emission.
• Developed a fast-response hydrochromic RTP ink and multilevel information encryption capabilities.

Conclusions:

• The proposed energy-relay strategy provides a versatile design paradigm for sustainable long-wavelength RTP materials.
• This approach opens new possibilities for advanced optical anti-counterfeiting and sensing technologies.
• The method offers a general solution for overcoming the energy gap law in phosphorescent materials.