Water-soluble MoS₂ quantum dots as effective fluorescence probe for the determination of bilirubin in human fluids

Bilirubin is an important biomarker in the diagnosis and prognosis of patients with liver disorders. Herein, we report a simple, rapid, sensitive and selective quantitative determination of bilirubin using molybdenum disulfide quantum dots (MoS₂ QDs) as a probe. The MoS₂ QDs were synthesized through a hydrothermal route by using sodium molybdate and cysteine as the starting materials. The obtained MoS₂ QDs exhibits strong luminescence property and excellent stability. The HR-TEM image shows that the size of the prepared MoS₂ QDs was 2.4 nm with a spherical morphology. The MoS₂ QDs emit intense blue photoluminescence (with excitation/emission peaks at 310/392 nm) under UV light and the fluorescence of MoS₂ QDs was drastically quenched by the addition of bilirubin. The Förster resonance energy transfer (FRET) and inner filter effect (IFE) between MoS₂ QDs and bilirubin resulted in the fluorescence quenching of MoS₂ QDs. The present method demonstrated high sensitivity towards bilirubin with the limit of detection (LOD) of 2.1 nM (S/N = 3). The MoS₂ QDs probe showed remarkable selectivity to bilirubin over other possible interferences. Moreover, the present fluorophore was successfully utilized for the detection of bilirubin in human serum and urine samples. QDs based fluorescence probe for the recognition of bilirubin is reported for the first time.