The study of a novel high selectivity pyrenyl-based fluorescence probe with aggregation-induced emission characteristics for Fe3+ detection designed by a structure modulation strategy

Abstract

The past decades have witnessed the feat of fluorescent probes for Fe³⁺ detection, where eliminating the interference by other metal ions plays a pivotal role in its detection by probes in complex environments. Herein, by taking advantage of the substituent effects, the electron-withdrawing group (EWG) –CF₃ and electron-donating group (EDG) –CH₃ were introduced to 2-(1-pyrenyl)pyridine (pypyr) to prepare two turn-off fluorescence probes, 5-trifluoromethyl-2-(1-pyrenyl)pyridine (pypyr-CF₃) and 5-methyl-2-(1-pyrenyl)pyridine (pypyr-CH₃). Intriguingly, both probes displayed novel aggregation-induced emission (AIE) characteristics in MeCN/H₂O mixtures and the size and morphology of the aggregated particles were studied via DLS and TEM. By the modulation strategy, pypyr-CF₃ can detect Fe³⁺ in the presence of 29 different metal ions without interference. Comparatively, pypyr-CH₃ experienced serious interference from other metal ions such as Hg²⁺ and Zr⁴⁺. Besides, pypyr-CF₃ not only demonstrated a higher photoluminescence quantum yield (PLQY) of 65.25% and wider pH adaptability but is also capable of Fe³⁺ detection over a wide pH range of 2–11 with a short response time (5 seconds). A plausible quenching mechanism based on the inner filter effect has also been demonstrated. More importantly, the versatile applications of pypyr-CF₃, such as the quantitative analysis of Fe³⁺ in actual water samples, anti-forgery ink, fingerprint identification, etc., further corroborate its superb capabilities. This study aims to lend concrete support to the design and selectivity modulation of probes.