Absorption, emission, and time-resolved fluorescence maxima of 3,5-dimethylphenol (35DMP) were examined in various solvents, as well as in α-CD and β-CD solutions at pH ~2, pH ~7, and pH ~11. The corresponding nanomaterials were synthesized and characterized using SEM, DSC, FTIR, XRD, and ¹H NMR analyses. In CD solutions, the absorption and emission spectra of 35DMP are similar at pH ~2 and pH ~7 but differ at pH ~11. At higher β-CD concentrations, the spectral maxima and shapes are similar in all the pH, suggesting the formation of a same type of inclusion complex. But, α-CD shows distinct absorption and emission maxima at different pH values, indicating the formation of different inclusion. 35DMP is more deeply encapsulated in the nonpolar interior of β-CD than in α-CD, as reflected by the increase in fluorescence lifetime in the order: pH α-CD β-CD. The calculated HOMO–LUMO energy gap, total energy, free energy, enthalpy, entropy, dipole moment, and zero-point vibrational energy of the CD: 35DMPcomplex differed significantly from those of the isolated 35DMP, α-CD and β-CD molecules, and both the vertical and horizontal bond lengths between the methyl and hydroxy groups are smaller than the β-CD cavity size confirming the formation of an inclusion complex. SEM-EDX analysis confirmed the presence of silver in the nanomaterials. DSC thermograms of Ag: 35DMP: CD complexes show new thermal peaks distinct from those of pure 35DMP, α-CD, and β-CD. FTIR spectra of the nanomaterials indicate substantial decreases or absence of most characteristic peaks, confirming strong interactions between 35DMP, the CD cavity, and the silver nanoparticles.
Rajendiran et al. (Fri,) studied this question.