One-step hydrothermal preparation of highly stable N doped oxidized carbon dots for toxic organic pollutants sensing and bioimaging

Abstract

A simple one-pot hydrothermally fabricated N- doped oxidized carbon dots (NOCDs) revealed an excellent photostability under constant illumination with 344 nm UV radiation for 24,000 s and intermittently tested stability under ambient conditions for over 18 months. The general susceptibility of their PL was tested under different conditions of pH and temperature. The NOCDs were found to act as optical fluorometric sensors for pH and temperature revealing a linear, cyclic and reversible trend in their fluorescence intensity between pH 3 and pH 9 (response time ≤60 s) and 25 °C–70 °C temperature range (response time: ≤240 s). As reasonable temperature and pH sensing agent, a good linear fit with an excellent regression coefficients of 0.979 and 0.989 respectively, were revealed. Typical organic pollutants such as anionic (methyl Orange (MO) and Bromophenol blue (BrPB)) and cationic (Methylene Blue (MB), Rhodamine 6 G (Rh6G)) dyes were found to quench the corresponding fluorescence through an inner filter effect. This is the first report on detection of organic pollutants (MO, Rh6G and BrPB) using NOCDs as optical sensing probe. In vitro imaging on three different kinds of cells (HEK293, A549 and MDA-MB-231) confirms their biocombatibility. The work represents great opportunities from experimental research towards the practical applications with a possibility to develop them as highly stable fluorescent imaging agents for the applications in bio-imaging and sensing.