Mango Leaves ( Mangifera indica )-Derived Highly Florescent Green Graphene Quantum Dot Nanoprobes for Enhanced On-Off Dual Detection of Cholesterol and Fe 2+ Ions Based on Molecular Logic Operation.

In the present study, we have engineered a molecular logic gate system employing both Fe 2+ ions and cholesterol as bioanalytes for innovative detection strategies. We utilized a green-synthesis method employing the mango leaves extract to create fluorescent graphene quantum dots termed "mGQDs". Through techniques like HR-TEM, i.e., high-resolution transmission electron microscopy, Raman spectroscopy, and XPS, i.e., X-ray photoelectron spectroscopy, the successful formation of mGQDs was confirmed. The photoluminescence (PL) characteristics of mGQDs were investigated for potential applications in metal ion detection, specifically Fe 2+ traces in water, by using fluorescence techniques. Under 425 nm excitation, mGQDs exhibited emission bands at 495 and 677 nm in their PL spectrum. Fe 2+ -induced notable quenching of mGQDs' PL intensity decreased by 97% with 2.5 μM Fe 2+ ions; however, adding 20 mM cholesterol resulted in a 92% recovery. Detection limits were established through a linear Stern-Volmer (S-V) plot at room temperature, yielding values of 4.07 μM for Fe 2+ ions and 1.8 mM for cholesterol. Moreover, mGQDs demonstrated biocompatibility, aqueous solubility, and nontoxicity, facilitating the creation of a rapid nonenzymatic cholesterol detection method. Selectivity and detection studies underscored mGQDs' reliability in cholesterol level monitoring. Additionally, a molecular logic gate system employing Fe 2+ metal ions and cholesterol as a bioanalyte was established for detection purposes. Overall, this research introduces an ecofriendly approach to craft mGQDs and highlights their effectiveness in detecting metal ions and cholesterol, suggesting their potential as versatile nanomaterials for diverse analytical and biomedical applications.