abstract
The vibrational dynamics and phase behavior of deep eutectic systems (DES) comprising ammonium salts and urea have been investigated using a combination of computational chemistry with inelastic neutron scattering (INS) and isotopic substitution. The study explores the impact of cation (a)symmetry on the vibrational modes of ammonium salts and urea in eutectic mixtures. By employing deuterated urea in tetraalkylammonium-based DES mixtures, selective observation of the INS spectra of individual components is achieved. Subtracting INS spectra for isotopically substituted urea mixtures provided separate “views” of the salt and urea contributions, highlighting changes in intermolecular interactions. Two types of organization of urea molecules are derived from the INS bands of urea in the mixture with symmetric and asymmetric cations. This is consistent with the view that the cation's asymmetry affects mostly the urea side of the solid–liquid equilibrium diagram and deep eutectic behavior stems from the deviation of the urea solid–liquid equilibrium line from ideality.
authors
Rafael AF Serrano, Catarina F Araújo, Paulo Ribeiro-Claro, Pedro D Vaz, Svemir Rudić, João AP Coutinho, Mariela M Nolasco
our authors
Catarina F. Araújo
Researcher
Mariela Martins Nolasco
Assistant Researcher
Paulo Ribeiro-Claro
Associate Professor with Aggregation
Rafael Alexandre Farinha Serrano
PhD StudentGroups
G4 - Renewable Materials and Circular Economy
G6 - Virtual Materials and Artificial Intelligence
Projects
CICECO - Aveiro Institute of Materials (UIDB/50011/2020)
CICECO - Aveiro Institute of Materials (UIDP/50011/2020)
Associated Laboratory CICECO-Aveiro Institute of Materials (LA/P/0006/2020)
acknowledgements
This work was developed within the scope of the project CICECO-Aveiro Institute of Materials, UIDB/50011/2020 (DOI 10.54499/UIDB/50011/2020), UIDP/50011/2020 (DOI 10.54499/UIDP/50011/2020) & LA/P/0006/2020 (DOI 10.54499/LA/P/0006/2020), financed by national funds through the FCT/MCTES (PIDDAC). FCT is also acknowledged for the PhD grant to CFA (SFRH/BD/129040/2017). The STFC Rutherford Appleton Laboratory is thanked for access to neutron beam facilities (TOSCA/RB1810054, https://doi.org/10.5286/ISIS.E.RB1810054). CASTEP calculations were made possible due to the computing resources provided by STFC Scientific Computing Department's SCARF cluster.