Evaluation of Phthalic acid Tri-ethylene diamine (TED) and Folic acid-based carbon quantum dots for detection of heavy metals in water resources using fiber-optic instrumentation.

Heavy metal pollution and toxicity from water resources has remained a great concern for entire population. This research demonstrates the capability of carbon quantum dots (CQD) for the fluorescence-based heavy metals detection in different water resource using a fiber optic spectrometer device. Two different types of CQDs (phthalic acid & triethylenediamine (PT CQDs) and Folic acid (FCQDs) were synthesized using microwave irradiation & hydrothermal method, respectively. CQD were characterized using several techniques like TEM, EDX, XPS and FTIR. PTCQD & 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 (Pb 2+ , Co 2+ , Mn 3+ , Hg 2+ , Ni 2+ , Cr 3+ ) tested in the study in the range of 0-100 µM. The accuracy of heavy metal detection from both CQDs FCQDs and PTCQDs respectively showed that (Mercury (98.96%±1.04&106.6%±6.6), Nickle (99.29%±2.9&99.18%±102.8%±2.8), Lead (103.3%±3.3 &104.8%±4.8), Manganese (101.3 % ± 1.3 & 101.4 % ± 1.4), Chromium (101.9 % ± 1.9 & 101.9 % ± 1.9), Cobalt (100.8 %± 0.8 & 101.9%±1.9). It was found that FCQDs shows a three-fold higher sensitivity and greater resolution than PTCQDs for all the heavy metals samples. The CQDs sensing capability shows that CQDs are able to achieve a limit of detection in the range of 0.15-3µM along with 100% accuracy in terms of recovery with minimal error, these results clearly 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 shows more sensitivity for all metals as compared to PTCQDs and used in future as a sensing tool for heavy metal detection with better sensitivity and accuracy with less response time.