Hg(ii) causes photoluminescence quenching of pyrene inside a blue emitting ionic liquid-derived crystalline nanoball

Abstract

This report presents the self-assembly of a blue-emitting ionic liquid (IL), NTIL, prepared by combining pyrene butyrate with a quaternary phosphonium ionic liquid (IL) through a straightforward ion exchange method. Water-dispersible crystalline nanoparticles, referred to as nNTIL, were developed using a reprecipitation technique. The nanocrystalline and molecular-level organization of pyrene moieties within these nanoparticles was validated using various spectroscopic, microscopic, and calorimetric analyses. Pyrene counterparts in the nanocrystalline nanomaterials demonstrate a strong tendency to self-associate when excited. The self-aggregation of pyrene moieties in their electronic excited state is found to be pronounced and beyond the simple excimeric dimerization process. Hg²⁺ ions cause strong photoluminosity quenching, which is found to be pronounced owing to the strong π–π stacking interactions among the pyrene moieties inside the crystalline nanoball due to the strong electrostatic interaction between pyrene butyrate and Hg²⁺ ions, causing further clotting of water dispersed nanoparticles. The induction of further coagulation of nNTIL by Hg²⁺ ions was validated through scanning electron microscopy (SEM) and energy dispersive X-ray spectroscopy (EDS) analysis. Analysis of the quenching of photoluminosity through photoluminescence lifetime decay analysis revealed that the process is dynamic. The practical applications of nNTIL were illustrated through analyses of water and soil samples, paving the way for applications in diverse fields. Furthermore, we investigated the sensor's effectiveness in detecting Hg²⁺ ions using affordable test strips. The present report introduces the fabrication and implications of metal-sensitive IL-based low-dimensional materials exhibiting remarkable photophysical properties compared with traditional ones.