Fast fluctuations in deep eutectic melts: Multi-probe fluorescence measurements and all-atom molecular dynamics simulation study

Larger excitation wavelength dependence of fluorescence emission of chromophores with shorter lifetime suggests fast environmental fluctuations in (CH3CONH2 + LiBr/NO3) deep eutectics. Stronger fractional viscosity dependence for rotation of a short-lifetime probe has been observed and ascribed to stronger sensitivity to these fast fluctuations. All-atom molecular dynamics simulations reveal stretched exponential relaxation for the wavenumber dependent incoherent and coherent scattering functions for acetamide with dominating sub-hundred picosecond and sub-nanosecond timescales. These simulated results provide support to the experimentally observed different fractional viscosity dependence of rotation rates for probes with different lifetimes, and stronger decoupling for short-lifetime probes in these melts.