Construction of Acetaldehyde-Modified g-C₃N₄ Ultrathin Nanosheets via Ethylene Glycol-Assisted Liquid Exfoliation for Selective Fluorescence Sensing of Ag⁺

We successfully prepared acetaldehyde-modified graphitic carbon nitride (g-C3N4) ultrathin nanosheets (ACNNSs) by a simple ethylene glycol-assisted liquid exfoliation method. The introduction of acetaldehyde regulated the surface energy of g-C3N4 to better match with that of water, which improved the exfoliation efficiency. Moreover, acetaldehyde introduces defects into the g-C3N4 structure, which can act as excitation energy traps and cause considerable variation in the fluorescence emission. Benefiting from the stable photoluminescence emission, good water solubility, and biocompatibility, the obtained ACNNSs showed a selective fluorescent response to Ag+ in both aqueous solution and living cells. The strong absorption and intimate contact with Ag+ and its appropriate redox potential of ACNNSs contributed to this excellent fluorescent response. A simple and environmental friendly approach was proposed to simultaneously achieve modification and exfoliation of g-C3N4 in aqueous solution. These findings might lead to wider applications of carbon-based nanomaterials as active materials for fluorescence detection in the environment.