Existence of nano-sized aggregates in aniline and chloroform binary system

Abstract

The liquid binary system of aniline (ANL) and chloroform (CHL) was discovered to form aggregates at a nano-size level responsible for the peculiar trends of some physico-chemical properties, reflected in morphology. The density and viscosity were recorded in the temperature range from 273.15 K to 313.15 K at ten different molar fractions. While the correlation of viscosity and density with molar fraction indicated a modest deviation from ideality, the excess molar volume values derived from density values exhibited a large discrepancy from the directly measured results, suggesting the potential aggregation leading to local inhomogeneity of mixtures’ concentration. On the other hand, FT-IR and Raman spectra showed no significant frequency shift both for N-H stretching on ANL and C-H stretching vibration on CHL upon mixing, in agreement with quantum mechanical calculations, which revealed the presence of a few complexes with stoichiometry ANL:CHL = 1:2 and 2:2, formed through CH···π interactions. The nano-scale morphology was characterised using the dynamic light scattering (DLS) method and SEM imaging. The calculated molecular electrostatic potential (MEP) of complexes indicated the capability for further association among complexes or between complexes and ANL or CHL molecules to form larger aggregates. For the first time, nano-sized aggregates were spotted for a liquid binary system made of small-sized organic molecules (solvents) using the combination of thermodynamic measurement, vibrational spectroscopy, quantum mechanical calculations and SEM imaging.