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.