Rapid sequential detection of Al3+ and glyphosate using an “Off-On-Off” fluorescent probe based on salicylate modified layered double hydroxides

A fluorescent probe based on salicylate modified layered double hydroxide (LDH-SA) is presented, enabling the swift sequential detection of Al³⁺, fosetyl-Al and glyphosate in aqueous environment. The probe was synthesized using a simple co-precipitation procedure, and its properties and synthesis conditions were thoroughly characterized and optimized. A unique “off-on-off” fluorescent response was observed when the probe sequentially interacted with Al³⁺ and glyphosate, and the detection method based on this phenomenon was established. The limits of detection for Al³⁺ and glyphosate were determined as 0.03 μmol/L and 0.03 mg/L, respectively, with rapid detection periods of one minute and four minutes. The LDH-SA/Al³⁺ complex requires Al³⁺ to generate a chelation-gathered fluorescence effect, which is the mechanism by which it quenches LDH-SA. This is possible due to the inhibition of excited-state intramolecular proton transfer and photoinduced electron transfer processes within LDH-SA after incorporating Al³⁺. Upon interaction with glyphosate, competitive complexation between glyphosate and Al³⁺ is initiated, which leads to a recovery of the fluorescence spectrum of LDH-SA and demonstrating the “off-on-off” behavior. An “INHIBIT” logic gate system was devised utilizing the response, indicating potential applications in fluorescence-based devices. Such a rapid, sequential detection capacity is impressive. It attests to the utility of LDH-SA as a probe for Al³⁺ or glyphosate, and suggests promise for applications in pollutant analysis or environmental monitoring applications.