An insight into the solvatochromic and photophysical behaviours of biowaste-origin carbon nanodots

Abstract

In this work, C-dots were synthesised inexpensively, using hydrothermal, one-step pathway from persimmon peel biowaste. The prepared C-dots were investigated by UV–Vis spectroscopy, photoluminescence spectroscopy, XRD, TEM, CHN, FE-SEM and FT-IR. It was found that the C-dot is amorphous in nature, spherical in shape, narrow-sized, monodispersed, polar functionalised with average 2 nm size and highly dispersible in aqueous and non-aqueous media. Optical study in wide range of solvents, exhibited excitation wavelength dependency of photoluminescence, bathochromic and hypsochromic shifts in absorption and emission spectra and incredibly high quantum yields ranging from 10% to 60%. It was shown that the C-dot could be exploited as nanoprobe for polarity of medium in addition as fluorescent chemical sensing platform for some metal ions. Analyses resulted in different functional groups on the surface (carboxylic, carbonyl, amine, amide and hydroxyl) and led us to treat the solvatochromic method as convincing argument to resolve the dilemma of whether or not which functional groups are responsible for the intriguing observed optical properties. The increasing trend of emission efficiencies of homologues alcohols was interpreted in terms of exoergic (specific and non-specific) interaction parameters included in Kamlet-Taft’s equation along with the endoergic solubility parameters and correspondingly the stiffness of solvent.