Optical Sensor Based on WS₂ Quantum Dots for Lamotrigine Determination

In this work, we obtained WS₂ quantum dots by both liquid exfoliation and hydrothermal synthesis following a top-down and a bottom-up approach, respectively. The resulting nanomaterials were spectroscopically characterized by UV-vis absorption and fluorescence techniques. Atomic force microscopy measurements were performed for the morphological characterization. We have studied the interaction between the as-synthesized WS₂ quantum dots with the antiepileptic drug lamotrigine, a noncolored analyte. This interaction produces a quenching of the native fluorescence of the nanomaterials, which depends linearly on the lamotrigine concentration. Moreover, the Stern-Volmer constants were calculated and the inhibition mechanism of the interaction was also investigated. Next, the WS₂ quantum dots were immobilized on quartz supports for the development of an optical sensor for lamotrigine determination. The sensor shows a linear response with the analyte concentration in the 35.4-250 μM range, with a limit of detection of 10.6 μM. The sensor was applied to the determination of lamotrigine in a synthetic serum sample, obtaining a recovery of 94%. Moreover, for a rapid and visual detection of lamotrigine, we have tested the suitability of using paper as a support for immobilizing WS₂ quantum dots.