Preparation of biodiesel oil-in-water nanoemulsions by mixed surfactants for bifenthrin formulation

Although several approaches have been reported on the development of nanoemulsions over the last few years, studies on the formation of biodiesel nanoemulsions for bifenthrin formulation by the low-energy phase inversion composition (PIC) method are still scarce. Herein, the preparation of oil-in-water (O/W) nanoemulsions suitable for pesticide application has been achieved in biodiesel by dissolving a bifenthrin/mixture of a non-ionic surfactant (NP-6) and an anionic surfactant (ABSCa)/water system by the PIC method. The mechanism of the formation of bifenthrin nanoemulsions by dripping the water phase into the oil–surfactant phase was exemplified via the pseudo-ternary phase diagram. The effects of the mass ratio of NP-6 and ABSCa, mR(OS), stirring rate, the addition rate of water and the emulsification temperature on the mean droplet size of the nanoemulsion were investigated by dynamic light scattering (DLS). In addition, the interfacial tension and the contact angle of bifenthrin nanoemulsions for the spraying application were investigated. The insecticidal activity of bifenthrin nanoemulsions against cabbage maggots was further studied. Moreover, the emulsion stability of the bifenthrin nanoemulsions against Ostwald ripening behavior was evaluated, and the long-term stability of the bifenthrin formulation was studied by the HPLC method to assess the shelf life of the pesticide formulation. Experimental results showed that the optimum emulsification conditions for the mass ratio of NP-6 and ABSCa, mR(OS), stirring rate, the addition rate of water and the emulsification temperature were respectively 5/5, 1.4, 8000 rpm, 0.7 mL min(−1) and 25 °C. The bifenthrin nanoemulsion with low interfacial tension and contact angle, easy adsorption on plant leaf surfaces and good shelf life has great potential for use as a pesticide formulation.