A turn-on fluorescent organic nano-optode derived from pyrene-coupled phenanthroimidazolate room temperature ionic liquid for ultrasensitive detection of dextran sulphate

Abstract

A very simple and inexpensive ionic liquid (IL)-based method has been utilised to detect a polysaccharide polyanionic derivative of dextran using a simple phenanthroimidazolate-based fluorescent IL, trihexyltetradecylphosphonium 2-pyrene phenanthroimidazolate, [PPIP]. The unique photophysical properties of the synthesised ILs have been characterised using various spectroscopic techniques. The aggregation behavior of [PPIP] was analyzed by varying the water percentage from 0% to 100%. During these experiments, the molecule exhibited special photophysical properties, including aggregation-caused quenching (ACQ) and J-type aggregation. Furthermore, the [PPIP] in its aggregated form, n[PPIP], shows an intense yellow color emission, which further rapidly transformed to a remarkable greenish cyan color emission upon addition of dextran sulphate sodium (DSS) salt. The detection limit is observed to be in the ng mL⁻¹ range and found to be superior than others available in the literature. This report enables rapid, visual detection of DSS. It supports the expanded use of IL-based photonic materials for next-generation photoluminescent low-dimensional optodes in biomedical, diagnostic, environmental, and forensic applications.