CeO2 loaded on L-tryptophan functionalized graphitic carbon nitride colorimetric-fluorescent dual-channel detection

In this study, a nanocomposite with CeO2 loaded on L-tryptophan functionalized graphitic carbon nitride (CeO2/L-g-C3N4) was developed by a facile two-step method. Firstly, L-tryptophan functionalized graphitic carbon nitride (L-g-C3N4) was achieved via π-π stacking interactions through a physical ultrasonic treatment process, which had better dispersibility in water than Bulk-g-C3N4. Then the final product of CeO2/L-g-C3N4 was obtained by a hydrothermal co-precipitation technique with cerium nitrate as precursor. The characterization of morphology indicated that CeO2 nanoparticles evenly distributed on the surface of CeO2/L-g-C3N4, which might be attributed to L-tryptophan offering more bonding sites (-COOH) for the deposition of nanoparticles. The material exhibited excellent oxidase-mimicking activity which could catalyze the colorless TMB into blue oxTMB, and a new hydroquinone (HQ) colorimetric sensing strategy was proposed. And theoretical simulations indicate that the increased enzymatic activity is mainly attributable to the reduced binding energy of absorbed intermediates. Additionally, due to the material's exceptional fluorescence properties, combined with the inner filter effect and redox reactions, a unique on-off-on fluorescence sensing mechanism had been successfully developed for the detection of Cr(VI) and SO32-.