Deep Eutectic Solvents

DESs are classified as the novel type of solvents that are associated with a hydrogen bond network followed by a depression in melting point at a fixed ratio when set against the individual constituents. DES is currently viewed as a newer and more versatile alternative to ionic liquids, with a lot of benefits and widespread applications. There are many characteristics of DESs that are similar to those of ILs, such as impressive thermal stability, reduced vapor pressure, adjustable polarity, non-flammability, low volatility, etc. These attributes make DESs strong contenders for replacing the approximately 600 or more volatile organic compounds (VOCs) currently prevalent in research and industrial applications. In addition to that, DESs have less complicated synthesis methods, are cheaper to make, are usually non-toxic with high purity, recyclable, biodegradable, and may also be applied to biological systems. As a result, DESs can be an alternative to toxic organic solvents used in different industrial processes, particularly electroplating, metal processing, polymer synthesis, biodiesel purification, drug solubility studies, biological transformations, and carbon dioxide removal absorption. Researchers have also applied DESs in different areas of research, such as organic synthesis, organic extractions, and electrochemistry.

During my undergrad, I was involved in two DES-based projects, which I will outline shortly below.

Mechanochemical Preparation of Deep Eutectic Solvents

Recent developments in mechanochemistry have enabled the preparation of deep eutectic solvents (DESs), which can be a greener and more viable alternative to the traditional thermal preparation of DESs. Although the mechanochemical method has been widely employed in both organic and inorganic preparation, its application in the preparation of DESs is still limited. Since the mechanochemical method can be performed under ambient conditions and does not require the application of heat, the mechanical energy generated during the grinding process can be sufficient to dissolve the solid HBA and HBD components and create a homogeneous mixture of DES. In this research, we used an efficient and eco-friendly mechano-assisted DES using rotary tumbler ball milling techniques instead of applying any heat, where mechanical energy is applied to facilitate the formation of DES. In this regard, we prepared three different types of DESs using the mechanochemical method and compared them to traditional thermally prepared DESs, all of which were characterized and analyzed using multi-technique approaches including spectroscopic, statistical, and thermal analysis. A spectroscopic FT-IR investigation was used to confirm the formation of DES using both methods. Principal Component Analysis (PCA) of the FTIR spectra data showed that both methods produced similar results for all the DESs prepared. Thermal analysis of the DESs was performed using differential scanning calorimetry (DSC) and thermogravimetric analysis (TGA). The results revealed that in all cases, even and almost for more challenging DESs, the mechanochemical-assisted rotary tumbler ball milling method showed unique advantages in comparison with traditional preparation processes in terms of energy, performance, security, operating time, economics, and thus industrial-scale reality. This method can reveal the pathway to meet the industry’s new expectations for DES production and the future development of this green solvent-based process in different fields.

In this project, we prepared three classes of DES using mechanochemical methods and compared them with conventional thermal methods. We characterized the formation of DES using experimental ATR-FTIR, DSC, and TGA techniques. Additionally, we compared the results with the thermal method of preparing the same DESs.

PHYSICOCHEMICAL AND STRUCTURAL CHARACTERIZATION OF NEW AMINO ACID-BASED DEEP EUTECTIC SOLVENTS (AADES)

Amino acid-based deep eutectic solvents (AADES) are safe, sustainable, biodegradable, and environmentally friendly substances by nature. They demonstrated potential in improving protein, drug, and biosynthetic solubilities. Although numerous studies are focused on the preparation and application of DESs, few studies are reported to elucidate the complex structure, dynamics, and interaction behavior of DESs.

Here we employed molecular dynamics (MD), atom-atom radial distribution functions (RDFs), and density functional theory (DFT) coupled with spectroscopic approaches to explore the formation of amino acid-based DES.