Determination of the Physical Properties of Room Temperature Ionic Liquids Using a Love Wave Device

Abstract

A s their name indicates, room temperature ionic liquids (RTILs) are liquids that are composed entirely of ions and that remain liquids at room temperature. They are generally very stable over a large temperature range, nonflammable, and have low volatility and are therefore rapidly emerging as alternative environmentally friendly solvents. 1À3 Their applications have been reported in a wide range of areas, including organic synthesis, catalysis, electrochemistry, 4 liquid crystal, 5 and separation technologies. 6,7 With over a million simple ionic liquids available, scientists and engineers are presented with numerous opportunities to design ionic liquids with specific properties for different applications but also with challenges to develop methods to characterize them to optimize their properties. Although with increasing utilization, the cost of some ionic liquids is decreasing, ionic liquids are, in general, relatively expensive, and new ionic liquids require synthetic routes to be developed. Currently, full characterization of the physical properties of such ionic liquids requires significant volumes of material to be synthesized before it is known whether they are useful for the process to be developed. Therefore, to reduce the synthetic burden and the cost, robust and high-throughput analytical techniques that require minimal volumes of liquids for characterization are desirable.High-frequency acoustic wave devices are widely used in telecommunications but also provide a surface oscillation that can be used to probe or sense materials with which they come into contact. In a Rayleigh-type surface acoustic wave, the oscillation includes an out-of-plane component, and this prevents their use with most liquids because on contact with the liquid, the wave's component of displacement normal to the surface generates a compressional wave into the liquid, giving rise to significant attenuation of the surface wave. However, acoustic wave sensors, using a shear-wave polarization with a particle displacement in the plane of the device surface, do not generate compressional waves and have been successful in liquid sensing applications. 8À10 Device types include the quartz crystal microbalance (QCM), which uses a thickness shear mode operation, and the surface acoustic wave device (SAW), which uses a planar fabricated set of interdigital transducers (IDTs) to excite the wave. Both types of sensors operate by creating a highfrequency shear wave that entrains the liquid present on the surface and causes a change in the wave velocity and amplitude. Recently, a QCM operating at a fundamental frequency of 5 MHz and its harmonics was successfully used to study the Newtonian response of RTILs by measuring the shift in the resonant frequency of the device and its bandwidth after the liquid is introduced. 11 This showed that the densityÀviscosity product of a liquid can be determined from only 40 μL of liquid ABSTRACT: In this work, we have shown that a 100 MHz Love wave device can be used to determine whether room temperatur...

Hybrid Sensor Device for Simultaneous Surface Plasmon Resonance and Surface Acoustic Wave Measurements

“…Furthermore, a linear correlation between phase and amplitude change should be expected for Newtonian liquids, which can be evaluated from Equation (10) [46]:…”

Applications of ionic liquids in the removal of contaminants from refinery feedstocks: an industrial perspective

“…The solubility of diesel in the ILs was measured using a gravimetric method by weighing the mass difference of a given amount of IL and the IL saturated with diesel. The results showed that the diesel has a certain solubility in 3-methylpyridinium-based ILs and its solubility in 3-methylpyridinium-based ILs varies to a large extent for different IL species and follows the order [C 8 3 MPy][BF 4 ] > [C 6 3 MPy][BF 4 ] > [C 4 3 MPy][BF 4 ], with the solubility being 9.5, 7.6 and 6.1 wt%, respectively. This diesel solubility order was attributed to the hydrophobic increase from [C 4 3 MPy][BF 4 ] to [C 8 3 MPy][BF 4 ] as the alkyl substituents in the ILs increase from butyl to octyl.…”

“…The results showed that the diesel has a certain solubility in 3-methylpyridinium-based ILs and its solubility in 3-methylpyridinium-based ILs varies to a large extent for different IL species and follows the order [C 8 3 MPy][BF 4 ] > [C 6 3 MPy][BF 4 ] > [C 4 3 MPy][BF 4 ], with the solubility being 9.5, 7.6 and 6.1 wt%, respectively. This diesel solubility order was attributed to the hydrophobic increase from [C 4 3 MPy][BF 4 ] to [C 8 3 MPy][BF 4 ] as the alkyl substituents in the ILs increase from butyl to octyl. The reason for this may be that the hydrophobicity of these three 3-methylpyridiniu-based ILs is stronger than those mentioned in our previous reports because of the alkyl substituent on the pyridine ring.…”

“…The properties of ILs are variable and can be in theory adjusted for any application, i.e., they are not all non-corrosive, but they can be designed to be non-corrosive, but in general, they are characterized to have low vapor pressures, thermal and chemical stability, non-ammabilit. 3 The applications of ILs include microwave-assisted organic synthesis, 4 catalysis, 5a-c biocatalysis, 6 separation, 7 extraction, 8 electrochemistry, 9 nanomaterials synthesis, 10 polymerization reactions, 11 as well as corrosion inhibitors. 12 Interestingly, ILs can also offer promising opportunities to reassess and optimize existing technologies and processes related to the petroleum industry, as demonstrated by the large number of research studies on the evaluation of ILs in petroleum-derived applications.…”

Interfaces Based on Carbon Nanotubes, Ionic Liquids and Polymer Matrices for Sensing and Membrane Separation Applications

“…Ouali et al used a Love wave sensor in order to verify the Newtonian behaviour of ILs [36]. Th e viscosity and viscoelastic behaviour of ILs strongly depends on the concentrations of dissolved volatile compounds or gases, and access to the respective data is crucial for process applications where ILs serve as a solvent or interface.…”