Design and synthesis of Bi-doped NiAl-LDH/g-C3N4 heterostructure; a novel 2D/2D system for simultaneous enhanced photocatalytic degradation and fluorescence sensing of ciprofloxacin

2D systems enable new opportunities for the development of photocatalysts. Layered double hydroxides (LDHs) indicate a wide range of applications due to their tunable functional properties. Regarding the intrinsic catalytic performance and excellent electronic structure of LDHs, and physicochemical stability of g-C3N4, we innovatively propose and investigate a novel Bi-doped NiAl-LDH/g-C3N4 2D/2D heterostructure system toward visible-light-driven photocatalytic degradation and fluorescence sensing of ciprofloxacin (Cipro). Based on the electrostatic self-assembly method, LDH nanosheets were grown on the g-C3N4 surface. SEM and TEM images confirmed that the LDH nanosheets were successfully loaded on the carbon nitride's smooth surface. The most efficient composite (40%-g-C3N4/LDH) displayed 86% Cipro removal efficiency over 180 min under visible light irradiation. The main reason for the aforementioned improvement in catalytic activity was due to the intimate face-to-face contact in heterojunction between two semiconductors and increased flow of charge-carrier to the surface. As an auxiliary agent, bismuth-containing LDH can trap electrons and thus reduce carrier pairs recombination. Additionally, the prepared composite displayed excellent fluorescence sensitivity toward Cipro with a low detection limit of 3.7 nM. Our approach will provide a new perspective on designing 2D/2D heterojunctions between LDH and other two-dimensional semiconductors toward simultaneous photodegradation and detection of antibiotics.