Ionic liquid advances in optical, electrochemical, and biochemical sensor technology

In addition to the features just mentioned, ILs exhibit a wide electrochemical window, high ionic conductivity, a broad temperature range of the liquid state, and frequently possess excellent chemical inertness as well. Moreover, the physical properties of ILs-including density, melting point, conductivity, polarity, Lewis acidity, viscosity, and enthalpy of vaporization-can all be tuned by changing the cation and anion pairing. Thus one can, in principle, design an IL for a speci c task (e.g., extraction, separation, reaction) simply by manipulating its key physicochemical properties as a result of appropriate cation/anion pairings. The dual nature (discrete ions) of ILs allows for the compartmentalized molecular-level design of a wide range of versatile molten systems. All of these features, particularly their tunable property sets, have proved to be important drivers in the areas of electrochemistry, separation sciences, chemical synthesis, catalysis, energetic materials, pharmaceutics, biotechnology, lubricants, heat transfer uids, nanochemistry, and analytical chemistry, among others. To date, ILs have been used in numerous chemical applications but they have, of course, been most often discussed as possible substitutes for volatile organic solvents in synthesis and catalysis, industrial processing, electrochemistry, and separation technologies. Most recently, interest surrounding their distinctive potential in analytical chemistry, particularly in sensor and device technology, is gaining extraordinary momentum [10-14]. This chapter focuses on such contemporary developments into the application of ILs in optical, and electrochemical-biosensors and, to a lesser extent, in actuator and micro uidic devices.