**3. Results**

#### *3.1. Chemical Composition of the Lemon Essential Oil*

A lemon-like odor liquid oil isolated by steam distillation from lemon peels was transparent and colorless. The components of the LEO identified are given in Table 3. Analysis of the volatile constituents of the LEO compounds by GC–MS identified 15 compounds that accounted for more than 0.5%, with a total of 96.36%. The major components detected in LEO were limonene (48.54%), α-pinene (30.90%), β-citral (3.65%), and β-myrcene (3.01%). As seen, the main constituents of the EO in this study were composed of monoterpene hydrocarbons (83.53%), including limonene, α-pinene, β-myrcene, and terpinolene.

**Table 3.** Chemical composition (%) of the essential oil isolated from lemon peels.


### *3.2. Single-Factor Experiments*

The effects of parameters on the mean droplet size of LEO-NEs were investigated using singlefactor experiments, including the HLB value (8, 9, 10, 11, 12, 13, 14 and 15), concentration of essential oil (0.05, 0.06, 0.07, 0.08, 0.09 and 1 g/mL), concentration of surfactant (0.0125, 0.025, 0.05, 0.1 and 0.2 g/mL), ultrasonic power (100, 300, 500, 700 and 900 W) and ultrasonic time (0, 10, 20, 30 and 40 min). The ranges for parameter values of RSM were set to the right and left of the optimum values.
