Selective, Sensitive and Label-Free Detection of Fe³⁺ Ion in Tap Water Using Highly Fluorescent Graphene Quantum Dots

Graphene quantum dots (GQDs) as a new type of fluorescent carbon nanomaterials, showing excellent photoluminescence properties, biocompatibility, photoelectric properties, have become the current research focus. Iron element as an essential element in the human body and an important part of hemoglobin, is very important for human health, so the detection of ferric ions has great significance. In this paper, GQDs with strong blue light emission were prepared through pyrolysis treatment using citric acid as a carbon source. Through characterization by transmission electron microscopy (TEM) and fluorescence spectrometer, it was observed that the GQDs have a uniform particle size distribution and highly fluorescent intensity with a quantum yield of 27.4%. Due to the strong quenching effect of Fe³⁺ on GQDs fluorescence, GQDs was used as a green and facile fluorescence sensor to detect Fe³⁺ selectively and sensitively. The GQDs fluorescence sensor shows a sensitive response to Fe³⁺ in a wide linear range (3.5 × 10^-6-6.7 × 10^-4 M), a low detection limit of 1.6 μM (S/N = 3) and good selectivity. Importantly, the new sensor realizes the detection of Fe³⁺ ions in tap water because of its low detection limit, wide linear range, and high sensitivity.