In this work, the effects of various factors, including the ultrasonic duty cycle and intensity of ultrasonic irradiation, ultrasonication and clove oil content in production of clove oil nanoemulsion were investigated. In preparation of nanoemulsion Tween® 80/Span® 80 as nonionic surfactants via ultrasonic emulsification method was used. The average droplets size of clove oil nanoemulsion decreased with an increase in duty cycle; whereas pulsed ultrasound with proper intervals was more efficient than continuous ultrasonication. In order to replace the use of organic solvent and increase the dispersity of active ingredient, suitable emulsifiers were used. The nanopesticides made by ultrasound at optimum formula conditions were defined at ultrasonication time of 300s, surfactants concentration of 5wt%, hydrophilic–lipophilic balance number of 9, duty cycle 0.75% and ultrasonic intensity 208W/cm2. The stability of droplets size of nanoemulsions for duration of 6months was evaluated. Stable nanoemulsion clove oil with 10wt% of clove oil content was formulated at optimum conditions with average droplets size around 43nm at the beginning and after 6months nanoemulsions re-sized and it was around 100nm. A stable nanoemulsion of clove oil in water with suitable droplets size as a nanopesticide was prepared

Clove oil is an essential oil used as a biodegradable antibacterial agent in food and pharmaceutical products. Emulsions are used to stabilize and increase the antimicrobial efficacy of oils in aqueous solutions. Smaller droplets provide better distribution of the oil. In this study, we formulate clove oil in aqueous solution by nanoemulsion. The aim of this study was to optimize key parameters in the preparation of clove oil nanoemulsion to obtain stable emulsions with less than 50 nm droplet size. The evaluated parameters include the concentration of clove oil, concentration of emulsifier, hydrophilic–lipophilic balance (HLB) number, and ultrasonication time. We determined the following response parameters: droplet size, polydispersity index, and zeta potential, and we aimed to achieve <50 nm droplet size with low polydispersity index and a highly negative zeta potential. The optimization and evaluation was obtained via Taguchi method. Taguchi method identified the concentration of clove oil and the HLB as the most affecting factors in the preparation of nanoemulsions. The optimum conditions for the preparation of nanoemuslion such as mean droplet size, polydispersity index, and zeta potential were 50 nm, 0.49 and −40.7 mV, respectively. This formulation of clove oil resulted in minimum inhibitory concentration against Escherichia coli and Bacillus cereus of 16 and 32 μg/ml, respectively, and minimal bactericidal concentrations of 16 and 64 μg/ml, respectively.