Distinct changes of Debye relaxation in primary and secondary monoalcohols by carbon nano-dots

摘要

The origin of the dielectric Debye relaxation in monoalcohols has kept interests for decades. In this work, we explored the Debye relaxation in a primary alcohol, 2-ethyl-1-hexanol, and a secondary one, 4-methyl-3-heptanol, by doping with carbon nano-dots. Dielectric and infrared spectra of the pure and doped samples were measured, We found that doping in 2-ethyl-1-hexanol decreases slightly the Debye relaxation strength together with a subtle decrease in the relaxation time, while, strikingly, the Debye relaxation strength in 4-methyl-3-heptanol is enhanced significantly, accompanied by increased relaxation time. Differently, the relaxation strength of the structural a-relaxation is both enhanced in the two monoalcohols. The infrared measurements reveal an evident increase in the fraction of associated hydrogen bonds for the doped 4-methyl-3-heptanol when compared to the pure sample. In contrast, only trivial difference is exhibited for the case of 2-ethyl-1-hexanol and its doped one. The remarkable effects of the carbon nano-dots on the Debye relaxation in the tested 4-methyl-3-heptanol sample could suggest the preferential transition from H-bond rings to chains. (C) 2019 Elsevier B.V. All rights reserved.