## 1 Introduction  
Silica aerogels have received much attention recently owing to their exceptional properties such as low density (0.003-0.8 g/cm\({}^{3}\)), large porosity (>90% having pore sizes ranging from 5 to 100 nm), high surface area, low thermal conductivity, and so forth [1, 2, 3]. These superior properties of aerogels make them useful for applications in the fields of optical sensors, biomolecule encapsulation, catalysis, adsorbents, chemical separation, drug delivery, and aerospace [4; 5; 6]. However, the traditional synthesis of silica aerogels involves the hydrolysis and condensation of tetraalkoxysilane precursors using a mildly acidic or basic catalyst followed by a drying process. The release of alcohol (from silane precursors) has detrimental effects on the activity of biomolecules during hydrolysis [7]. Moreover, the conventional drying process can cause up to 80% shrinkage of the gel network, resulting in limited entrapment of biomolecules. This limits the application of silica aerogel in the fields of biomolecule encapsulation and biosensors due to slow response time [8]. The encapsulation of biomolecules inside the gel matrix can be achieved in situ or after supercritical drying to eliminate network collapse. However, harsh supercritical drying can easily damage the biomolecule structure [9; 10]. To avoid this problem, ionic liquids (ILs) were recently used as green solvents for the preparation of sol-gel-derived silica-based aerogels [11; 12; 13]. Ionic liquids can control the structure of silica (i.e., pore size, structure, and distribution) apart from the type of catalyst, water content, solvent, and template used [14; 15; 16]. In addition, ILs can avoid the problem of gel shrinkage and act as a pore-forming template during the sol-gel formation. Ionic liquids can be confined inside the pores of silica aerogel, which act as a protective agent for the encapsulated biomolecules, thereby retaining their conformational stability [17]. The use of different ionic liquids for the preparation of silica aerogel was attempted by several researchers over the years [18; 19; 20]. [PERSON] et al. [18] reported the preparation of silica aerogel using imidazolium-based ionic liquids, which eliminated the risky supercritical drying process. ILs based on the salts of imidazolium ions were used as a morphology controller and precatalyst for the preparation of silica xerogel [19]. Additionally, ILs could be used as a drying control chemical additive during the sol-gel transition, which prevents the strain associated with the evaporation of solvents [20]. Ionogels are a new class of materials that emerged recently that are prepared using ionic liquids in which the ionic liquid is confined inside the nanopores of the silica gel matrix [21; 22; 23]. These solid-like macroscopic materials exhibit superior properties, which do not flow at room temperature compared with bulk ionic liquids [21; 24; 25; 26]. The properties include luminescence, transport, and high ionic or electronic conductivity [27; 28]. Novel ionogels were prepared using tamarind gum and ILs (1-butyl-3-methylimidazolium chloride and 1-butyl-3-methylimidazolium bromide), which have shown good adherence to human finger muscles and skin. These novel ionogels may find applications in electrochemical biosensors, actuators, and biomaterials [29]. Ionogels prepared by utilizing 1-methyl-3-butylimidazolium ibuprofenate with a minimal amount of solvent can be used as an efficient drug delivery system and the drug release kinetics can be controlled by the nature of the silica wall surface [30]. Furthermore, 1-butyl-3-methylimidazolium tetrafluoroborate IL was used to make a gel of low-molecular-weight iron dextran complex, which has applications in medical electrosensitive gel device fabrications [31]. Very recently, new types of nanocomposites containing agarose-chitosan-1-butyl-3-methylimidazolium chloride solutions were developed using an antisolvent method, suitable for sensors, solar cells, and electronic device materials [32].