Stimuli Responsive Ionogels for Sensing Applications—An Overview

Abstract

This overview aims to summarize the existing potential of “Ionogels” as a platform to develop stimuli responsive materials. Ionogels are a class of materials that contain an Ionic Liquid (IL) confined within a polymer matrix. Recently defined as “a solid interconnected network spreading throughout a liquid phase”, the ionogel therefore combines the properties of both its solid and liquid components. ILs are low melting salts that exist as liquids composed entirely of cations and anions at or around 100 °C. Important physical properties of these liquids such as viscosity, density, melting point and conductivity can be altered to suit a purpose by choice of the cation/anion. Here we provide an overview to highlight the literature thus far, detailing the encapsulation of IL and responsive materials within these polymeric structures. Exciting applications in the areas of optical and electrochemical sensing, solid state electrolytes and actuating materials shall be discussed.

Modular microfluidic valve structures based on reversible thermoresponsive ionogel actuators

“…The use of ionogel gel-based valves prevents this occurring since ILs have a negligible vapour pressure so that a more robust gel can be obtained. [14] Figure 4 shows the degree of dehydration of the hydrogel and ionogel over time and their linear response (inset). These results demonstrate that valves fabricated using the EMIES ionogel dehydrate about three times slower than those based on the hydrogel.…”

“…Ionic liquids have attracted much attention because of the potential applications in many fields of chemistry and industry due to their chemical and thermal stability, low vapour pressure, high ionic conductivity properties, and tuneable hydrophobic and hydrophilic nature. [14] Incorporating ILs into polymer gels is also attractive as this generates materials with the inherent advantages of ILs within a solid or semi-solid gel-type structure.…”

Applications of Ionic Liquids for the Development of Optical Chemical Sensors and Biosensors

“…Despite the achieved progress and the wealth of the literature on the considered topic, a comprehensive review highlighting the various roles of ILs in optical chemical sensors and evaluation of their potential to yield the novel materials for chemical analysis is still needed. To our knowledge, the previous reviews either cover briefly such optical sensors 25,[40][41][42] or focus on the classification and methods of the preparation of the IL-based materials. 25,28,43 Warner et al 44 reported the IL functions while producing photonic IL sensors.…”

“…[22][23][24][25][26] The electrochemical sensing materials prepared using ILs have been discussed in detail in the reviews. [22][23][24][25][26] The ability of some ILs to dissolve a broad range of substances gave rise to studying the possibilities of ILs in optical sensing technologies. ILs can dissolve inorganic gases (O2, CO2, CO, SO2, NO2, H2S, etc.…”

Properties and Customization of Sensor Materials for Biomedical Applications

“…The employment of ILs as a replacement for water in gel-based polymers has led to the emergence of ionogels as a relatively new subclass of materials. To date, ionogels have been the subject of reviews detailing their preparation and applications in sensor science (95,302). The ionogel template is an ideal matrix as the properties of the IL is hybridized within those of the polymer component, combining the favorable characteristics of both independent phases in one material.…”