Sustainable carbon nanodots synthesised from kitchen derived waste tea residue for highly selective fluorimetric recognition of free chlorine in acidic water: A waste utilization approach.

Highlights • Sugar and milk richer waste tea residue utilised for carbon nanodot synthesis. • Required materials available worldwide, easily, economical, and sustainable. • Simple carbonization route used for fluorescent carbon nanodot synthesis. • Environmental scavenger for free chorine over twenty-one (21) common ion tested. • Explored for water quality monitoring in various water bodies. Abstract A world wide easily available, economical, and sustainable carbonaceous source based on kitchen derived waste tea residue (containing sugar and milk) was used for the synthesis of carbon dots (CDs). Pyrolysis of waste tea residue in controlled condition was employed to synthesis water soluble carbon dots (WTR-CDs). The as-synthesised WTR-CDs exhibited emission at 415 nm, excitation dependent behavior, stability towards the pH and ionic strength. The emission intensity of WTR-CDs dwindled with an addition of hypochlorite ion (ClO⁻) and designed sensor achieved sensitive detection of free chlorine rapidly with higher selectivity over twenty-one (21) common interfering ion tested. WTR-CDs showed good response over a range of 0.02–2.0 µg mL⁻¹ of ClO⁻. Furthermore, the Stern-Volmer equation was used to obtain calibration curve displayed a very good linear response for the analyte within the range 0.02–0.30 µg/mL with the lowest limit of detection (LOD) is 0.038 µg/mL. Moreover, potential applications of this developed method were explored in various water bodies by standard addition method which finds a new avenue for the quantification of free chlorine and water quality monitoring. Graphical abstract Image, graphical abstract [ABSTRACT FROM AUTHOR]