DES-Based Green Synthesis of 2D Fluorescent Molybdenum Disulfide for Highly Sensitive and Selective Detection of Nifedipine

Highly fluorescent 2D MoS_2–x nanosheets exhibiting intense blue emission were synthesized using a green chemistry approach, utilizing DES as both the reaction medium and a surface passivating agent. The material was synthesized via a hydrothermal method, followed by ultrasonication-assisted exfoliation to yield ultrathin nanosheets with enhanced photoluminescence properties. The 2D MoS_2–x nanosheets demonstrated strong fluorescence at λ_em = 420 nm when excited at λ_ex = 330 nm. These nanosheets were employed as a fluorescence probe for the detection of the calcium channel blocker drug nifedipine (NIF) via a fluorescence quenching mechanism. Upon addition of NIF, the fluorescence of the 2D MoS_2–x nanosheets was quenched due to electron transfer from the nanosheets to the electron-deficient NIF molecules, combined with the inner filter effect (IFE). The nanosheets enabled highly sensitive and selective detection of NIF, with photoluminescence spectroscopy revealing a broad linear detection range of 0.6–360 nM (R² = 0.993) and an exceptionally low limit of detection (LOD) of 0.40 nM. The system showed high selectivity toward NIF over structurally similar compounds, drugs, and common metal ions. The sensor was effectively applied for the detection of NIF in urine and Lotus Pond water samples, highlighting its potential for practical pharmacological monitoring. This study presents a sustainable and effective approach for fabricating DES-assisted 2D nanosheets for trace-level analyte detection.