An ionic liquid composed of purely functional sensing molecules: a colorimetrically calcium responsive ionic liquid

Area of Science:

• Chemical Sensing
• Ionic Liquids
• Optical Sensors

Background:

• Conventional ionic liquids (ILs) typically use imidazolium or lipophilic cations.
• Existing optical sensors for calcium ions (Ca2+) lack high sensitivity and reversibility.

Purpose of the Study:

• To synthesize a novel ionic liquid (IL) composed entirely of functional chemical sensing molecules.
• To develop a highly sensitive and selective optical sensor for Ca2+ detection using the novel IL.

Main Methods:

• Synthesis of a highly lipophilic ionic liquid (IL) comprising an anionic calcium ionophore and a cationic dye.
• Fabrication of poly(vinyl chloride)-based and neat liquid membrane optical sensors incorporating the synthesized IL.
• Evaluation of sensor performance, including sensitivity, selectivity, and reversibility for Ca2+ detection, with preliminary tests against Na+.

Main Results:

• Successful synthesis of a novel IL consisting solely of sensing molecules (anionic ionophore and cationic dye).
• IL-based optical sensors demonstrated a 13-fold increase in sensitivity for Ca2+ compared to conventional sensors.
• The developed sensor exhibited fully reversible and selective responses to Ca2+.

Conclusions:

• The first report of an IL composed purely of functional sensing molecules, distinct from traditional imidazolium-based ILs.
• The high dye concentration in the IL leads to dramatically enhanced sensitivity in optical sensors.
• The novel IL-based sensor offers a promising platform for highly sensitive, selective, and reversible Ca2+ detection.