Carbon Dots Derived from Human Hair for Ppb Level Chloroform Sensing in Water

Chlorination is a widely adopted disinfection method in water and wastewater treatment for the protection of public health, as it greatly reduces pathogen risks and associated incidence of waterborne diseases. Chlo-rination, however, also creates disinfection by-products (DBPs) such as trihalomethanes, which, epidemiolog-ically, have been associated with a higher incidence of some forms of cancer. Therefore, developing sensors for monitoring the chlorine dosage and DBPs concentrations in real-time and in-line is of critical importance to public health. Carbon dots (CDs) are an emergent class of fluorescent nanomaterial offering highly-sensitive sensing functionalities towards a diverse range of chemical/biochemical contaminants, owing to their tuneable fluorescence, rich surface functionalities, low to non-toxicity and ease of synthesis. In this study, we demonstrate that 1) highly fluorescent CDs (quantum yield 38%) can be produced from simple thermal treatment from biowastes such as human hairs without employing any solvents; 2) the fluorescence spectra and intensity of the synthesized CDs responds to the presence and quantity of chloroform with high sensitivity, with a limit of detection of 3 ppb; and 3) through a pair-wise comparative study on autoclave-synthesized CDs (OCDs) and microwave-synthesized counterpart, we discovered that the pyridinic N oxide that is unique to OCDs imparts sensitive and selective sensing functionality towards chloroform; 4) the PL-based sensing functionality is not solely determined by the binding affinity between the analyte and the carbon dots, but also the electronic structures of the interacting entities. This study provides an in-depth study on how to utilize the diverse features of biowastes and impart unique functionalities to CDs for developing advanced functional materials. (c) 2020 Published by Elsevier B.V.