Carbon dots with aggregation induced emission enhancement for visual permittivity detection

Area of Science:

• Materials Science
• Nanotechnology
• Photochemistry

Background:

• Carbon dots (CDs) are fluorescent nanomaterials with diverse applications.
• Understanding their photoluminescence mechanisms, particularly aggregation-induced emission enhancement (AIEE), is crucial for optimizing their use.
• Tannic acid (TA) is a readily available precursor for synthesizing CDs.

Purpose of the Study:

• To investigate the AIEE properties of carbon dots prepared from tannic acid.
• To elucidate the relationship between solvent permittivity and the photoluminescence of these CDs.
• To explore the potential of TA-derived CDs for visual sensing applications.

Main Methods:

• Hydrothermal synthesis of carbon dots using tannic acid.
• Photoluminescence spectroscopy to measure emission intensity at 455 nm (excited at 350 nm).
• Solvent-dependent emission studies using various organic solvents with differing dielectric constants.

Main Results:

• The synthesized carbon dots displayed AIEE, with emission intensity significantly enhanced in organic solvents compared to water.
• A clear exponential decay relationship was observed between the ratio of photoluminescence intensity (organic solvent/water) and solvent permittivity.
• The restricted rotation of surface groups, including aromatic rings and phenolic hydroxyl groups, was identified as the cause of AIEE.
• Visually striking luminescence was observed in low-permittivity solvents like tetrahydrofuran (THF).

Conclusions:

• Tannic acid-derived carbon dots exhibit tunable AIEE properties dependent on solvent polarity.
• The observed AIEE mechanism is attributed to the hindering of rotational motion of surface functional groups.
• These findings highlight the potential of TA-based CDs for developing visual indicators in low-permittivity environments.