Origin of solvent and excitation dependent emission in newly synthesized amphiphilic carbon dots

Abstract

The present work demonstrates the synthesis of a new amphiphilic carbon dot from octylamine. Steady-state emission studies show excitation dependent emission features. Time-resolved emission studies show three different emission decay traces while exciting at 267 nm, 292–339 nm, and 374–445 nm regions. These excitation bands are assigned to the π–π*, n–π*, and surface group states respectively. It was further observed that only surface state exhibit excitation dependent emission behavior while both π–π* and n–π* states show marginal effect; the observation rarely discussed in the literature. Both growth and emission lifetime of π–π* is higher as compared to n–π* and surface group states suggesting the possibility of energy transfer from former to latter. The emission peak position was different in different solvents by exciting π–π* states however it was almost same when monitoring at the surface states which in contrast to the belief that π–π* states are embedded inside the shell and has the least exposure to the solvent. The study also suggests that in protic solvents both π–π* and n–π* states interact but not in other solvents. Moreover, the presence of multiple emission states is responsible for excitation dependent emission features from surface group states, each having its own lifetime.