ZrS₂ Nanosheets as Fluorescence Nanosensors for the Detection of Quercetin

Quercetin (QC) plays a crucial role in human health, driving demand for innovative sensors of fast response, being portable, and affordable tools to measure QC in everyday foods, supplements, biological matrices, and pharmaceuticals. ZrS2 nanosheets, two-dimensional fluorescence transition-metal chalcogenide (2D-fTMD), are demonstrated via their direct fluorescence or intrinsic fluorescence, then further employed as a fluorescent nanosensor for QC detection. A simple, easy, and fast solvothermal synthesis method was adopted for synthesizing the fluorescent and porous ZrS2 nanosheets, and the structure morphology, porosity, chemical composition, and optical properties were characterized with a variety of instruments, including TEM, DLS, BET, FTIR, UV–visible, and photoluminescence (PL) spectroscopy. After the structural and chemical characterizations were confirmed, the synthesized fluorescent ZrS2 nanosheets were utilized as a fluorescent nanosensor for detecting quercetin. Upon the addition of QC to ZrS2 nanosheets, the fluorescence was quenched, and the quenching response of nanosensors was recorded in the range of 30–700 nM, which demonstrated a linear response at 30–500 nM. The detection limit for this study was 1.42 nM with a linear regression value of 0.99. The quenching of the ZrS2 nanosheet fluorescence by the QC was explained by Förster resonance energy transfer (FRET). The nanosensor’s selectivity toward QC was evaluated by interfering compounds and metal ions, but there was a negligible effect on the fluorescence behavior of the ZrS2 nanosheets. The sensitivity and selectivity of the nanosensors toward QC prompted us to implement them in real-world applications for QC detection. The nanosensor was utilized to detect QC in a human urine sample, exhibiting a significant fluorescence recovery for the sample.