Clay/PVP nanocomposites enriched with Syzygium aromaticum essential oil as a safe formulation against Aedes aegypti larvae

Clay-polymer composites represent the possibility to stabilize, protect volatile and easily oxidized compounds such as essential oils. Thus, the aim of this study was to develop an eco-friendly formulation based on bentonite/PVP nanocomposites to incorporate Syzygium aromaticum essential oil (SAEO) in for controlling Aedes aegypti larvae. The bentonite/PVP nanocomposites were prepared with different ratios 1:2, 1:1, 2:1 in both absence (INano) or presence of SAEO (NanoSAEO), and evaluated by X-ray diffraction (XRD), small angle X-ray scattering (SAXS), differential scanning calorimetry (DSC), scanning electron microscopy (SEM) and Fourier transformed infrared spectroscopy (FTIR). Finally, larvicidal activity was performed. XRD indicated an intercalated structure because of the displacement of reflections at low angle range and an increase in INano interlayer space (d). After SAEO incorporation, the interlayer space (d) did not changed, therefore suggesting that SAEO may be associated to the nanocomposite-intercalated layers. SAXS also demonstrated the composite intercalated structure that in presence of SAEO induced a reflection displacement and change in the curve profile suggesting a structure transition to accommodate SAEO. This structure transition after SAEO incorporation was enough to shift the nanocomposite endothermic peak to lower temperatures (T-peak = 68 degrees C) in DSC analysis. NanoSAEO demonstrated a LC50 of 27.34 ppm, while eugenol and SAEO presented 48.19 ppm and 40.74 ppm, respectively. Furthermore, SAEO incorporated in the nanocomposite was not harmful to non-target organisms, being not toxic up to 1000 ppm. Thus, bentonite/PVP nanocomposites containing SAEO is a promising formulation for controlling Aedes aegypti larvae.