Transforming high-density polyethylene plastic bags into eco-friendly carbon dots for detecting ferric (Fe3+) ions

Eco-friendly transformation of HDPE plastic waste into carbon dots (CDs) has been developed in this work. A
green technique involving modified pyrolysis-sonication-hydrothermal processes has successfully synthesized the
CDs within a short time frame of 9 h and low concentration oxidant (5 wt% H2O2) with remarkable quantum
yield (QY) of up to 16.16 %. The resulting CDs showed good fluorescence stability as exposed to UV light
irradiation, various ionic strengths, and extended periods of storage. Furthermore, the CDs exhibit a crystalline
graphite-like structure and a consistent range of sizes, from 1.0 to 4.5 nm. Structurally, the produced CDs contain
oxygenated groups (carbonyl, carboxyl, and hydroxyl) and reveal high selectivity for detecting Fe3+ ions with a
limit of detection (LOD) of 3.82 μM. The CDs have also demonstrated good %Recovery of 88.25–95.33 % and %
RSD of <5 % as Fe3+ sensors for tap water. The synthesized CDs exhibit tremendous potential as a highly
promising Fe3+ ions sensor, particularly capable of detecting low concentrations in real water samples.