Highly exfoliated g-C3N4 as Turn OFF-ON (Ag+/CN-) optical sensor and the intermediate (g-C3N4@Ag) for catalytic hydrogenation

Abstract Highly exfoliated mono/few-layered graphitic carbon nitride (g-C3N4) was prepared through the thermal oxidation method. The obtained exfoliated g-C3N4 (Ex_g-C3N4) shows multiple emission (λem ≈ 433, 458, and 484 nm) peaks with an excitation independent fluorescence property. The luminescent Ex_g-C3N4 was tested for the selective optical detection of silver (Ag+) and cyanide (CN-) ions using PL spectroscopy. The quenching in the PL signal was noticed by the addition of Ag+ ions (Turn OFF) to the Ex_g-C3N4. Regeneration of the PL signal occurred upon the addition of CN- ions to Ag+ treated Ex_g-C3N4 (Turn OFF-ON). The minimum detection limit of Ag+ and CN- was calculated to be 2.15 and 380 nM respectively. The achieved nanomolar level sensitivity is advantageous since detection limits are far less than the WHO recommended limits. This method is beneficial over other traditional detection methods like spectroscopic and colorimetric methods in terms of cost, sensitivity, selectivity, and limits of detection. Additionally, we demonstrated the enhanced catalytic hydrogenation of the microgram quantity of p-nitrophenol to p-aminophenol using the nanogram quantity of recovered Ag+ treated Ex_g-C3N4 (g-C3N4@Ag).