An AIE active acidochromic pyrimidine-functionalized two-in-one fluorescent probe for selective relay detection of Al3+/Zn2+ and PPi with various detection applications

Abstract

A very simple multifunctional pyrimidine-based hydrazone was designed and developed as an effective tool for the dual-mode fluorescent turn-on detection of Al³⁺ and Zn²⁺ ions at two different wavelengths. The probe interestingly displayed blue fluorescence around 440 nm and cyan fluorescence around 470 nm with Al³⁺ and Zn²⁺ ions, respectively. Coordination of Al³⁺/Zn²⁺ ions with HSAL results in emission enhancement owing to chelation-enhanced fluorescence and inhibition of –CHN– isomerization as well as ESIPT. HSAL exhibited excellent sensitivity and selectivity towards the ions with good association constants and nanomolar level LOD values. In turn, HSAL–Al³⁺ and HSAL–Zn²⁺ ensembles could selectively and sensitively detect PPi ions among other anions. The overall binding mechanism of the probe towards Al³⁺/Zn²⁺ ions was analysed through Job's plot, ¹H NMR, mass, and density functional theory experiments. Besides, Al³⁺ ions could easily replace Zn²⁺ ions from HSAL–Zn²⁺ to demonstrate emission attributed to HSAL–Al³⁺, and also the probe showed a remarkable binding tendency towards Al³⁺ over Zn²⁺ ions in the presence of PPi. HSAL is capable of exhibiting reversible switching characteristics on the addition of Al³⁺/Zn²⁺ and PPi, which were successfully employed in constructing a logic gate. The excellent sensing characteristics of HSAL were utilized for various cost-effective applications including, real water, cotton swabs, thin film, and tablets. In addition, the compound HSAL was also able to reveal certain multifunctional behaviors like AIE and acidochromism.