Evaluation of phthalic acid tri-ethylene diamine (TED) and folic acid-based carbon quantum dots for the detection of heavy metals in water resources using fibre-optic instrumentation.

Heavy metal pollution and toxicity from water resources have remained a great concern for the entire population. This research demonstrates the capability of carbon quantum dots (CQDs) for fluorescence-based heavy metal detection in different water resources using a fibre-optic spectrometer device. Two different types of CQDs phthalic acid and triethylenediamine (PT CQDs) and Folic acid (FCQDs) were synthesized using microwave irradiation and hydrothermal method, respectively. CQDs were characterized using several techniques such as TEM, EDX, XPS and FTIR. PTCQD and FCQDs both were tested for sensing capability in water reservoirs like household and river water. The results indicate that both CQDs were able to detect all six heavy metal ions (Pb2+, Co2+, Mn3+, Hg2+, Ni2+, Cr3+) tested in the study in the range of 0-100 µM. It was found that FCQDs show a three-fold higher sensitivity and greater resolution than PTCQDs for all the heavy metals samples. The CQDs' sensing capability shows that they can achieve a limit of detection in the range of 0.15-3 µM along with 100% accuracy in terms of recovery with minimal error, these results indicate that both CQDs have a tremendous potential to be used as a sensor for the detection of heavy metals even in complex water matrices. FCQDs show more sensitivity for all metals compared to PTCQDs and used in future as a sensing tool for heavy metal detection with better sensitivity and accuracy with less response time.