High Throughput Signal-Off-On Fluorescent Aptasensor for Pb²⁺ Detection Based on Fluorescence Resonance Energy Transfer Between Graphite-Phase Carbon Nitride Nanosheets and Gold Nanoparticles

Heavy metal Pb<sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2+</sup> is widely distributed in several environmental media, and exposure to Pb<sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2+</sup> through various channels can seriously endanger the health of residents. Therefore, it is very important to detect Pb<sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2+</sup> in high throughput, accurately and specifically. Fluorescent sensors have obvious advantages in heavy metal detection. In comparison with the bulk phase, graphite phase carbon nitride nanosheets (g-CNNs) of atomic thickness and nanometer size can conspicuously improve the quantum yield and water solubility. The aptamer offers the benefits of exceptional specificity, robust stability, minimal toxicity, cost-effectiveness, straightforward synthesis and modification, and absence of immunogenicity. In this study, an high throughput signal-off-on fluorescent aptasensor was designed for detecting Pb<sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2+</sup> on the basis of fluorescence resonance energy transfer (FRET) mechanism between gold nanoparticles (AuNPs) and g-CNNs. Under the optimum experimental conditions, a linear correlation was established between (F-F<sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">0</sub>)/F<sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">0</sub> and Pb<sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2+</sup> concentration within the range of 0 to 1000 μg/mL. The linear equation was (F-F<sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">0</sub>)/F<sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">0</sub>=0.0002C + 0.0278, with an R2 value of 0.9744 and the detection limit was 0.8 μg/mL. The proposed fluorescent aptasensor had strong anti-interference ability, high sensitivity and good reproducibility, and the recoveries of spiked samples were between 90.32% and 103.99%. The detection results of Pb<sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2+</sup> in actual samples confirmed that this fluorescent aptasensor had good application potential.