## 3 Results and Discussion  
### The Electrospraying Process Observation  
To achieve a stable cone-jet, the effective parameters in electrospinning or electrospray process, namely, the concentration of the shell solution, the solvent characteristics, applied voltage, flow rates, and the distance between the needle tip and collector, should be optimized [31; 32].  
The concentration of the shell solution is important not only to control the viscosity, electrical conductivity, and interfacial tension of the solution but it also affects the stability of the tailor cone. It is difficult to obtain an intact shell with a low concentration of polymer and is challenging to achieve a stable cone-jet mode with high polymer concentration. It may also cause the formation of fibers instead of capsules, as shown in Figure S1 in the supplementary file. Therefore, the shell concentrations of 4, 5, and 6 wt.% were examined. The applied voltage also plays a critical role in the formation of core-shell capsules. The stable cone-jet can be obtained by changing the applied voltage. The dripping mode occurs when low voltage is applied, and, by applying high voltage, multi-jet occurs in the electrospray process [31]. Therefore, the applied voltages of 18 to 24 kV were examined to obtain the optimum applied voltage. Figure S2a, of the supplementary file, shows the FE-SEM image of the collector in dripping mode (low voltage), and Figure S2b shows the FE-SEM images of the prepared capsules in the multi-jet mode (high voltage). In addition, the inner and the outer flow rates in coaxial electrospray are the other effective factors for cone-jet stability and droplet size. A stable core-shell structure can be formed for a small range of inner/outer liquid flow rates [31]. Therefore, in this research, several feed rates were investigated, 0.5 to 1 mL.h\({}^{-1}\) as a shell feed rate and 0.01 to 0.06 mL.h\({}^{-1}\) as a core feed rate. Some of the unsuccessful encapsulations are shown through the FE-SEM images of Figure S3. Another important process parameter is the distance between the tip and the collector. At a constant voltage, a shorter distance is advantageous for generating a higher electrical field strength and consequently smaller particles are prepared. However, very short distance results in low solvent evaporation and, consequently, the coalescence and aggregation of wet particles at the collector. On the other hand, the long collector to tip distance would need higher applied voltage to compensate for the reduced electrical field strength. In general, one could expect to obtain larger particles compared to particles produced at a shorter collector to tip distance setup [33]. In this research, 13, 15, and 17 cm were examined as the distance of the needle to the collector. Figure S4 shows the FE-SEM images of the prepared capsules in two needle-to-collector distances. Using DMF as the solvent of shell material keeps the collector wet due to its slow evaporation rate, while DCM solvent leads to the formation of bigger particles (micro-scale) that is not appropriate for coating applications. Therefore, using a mixture of these solvents with equal amounts addressed the issue by optimizing solvent evaporation rate and electrical conductivity of the solution, which is reported in previous studies [34; 35]. Figure S5 depicts the FE-SEM images of the prepared capsules when the neat DCM and DMF were employed as shell solvent.  
Other effective parameters were optimized by changing a parameter and keeping the other constant. The parameters were chosen as optimum at those values where the electrospraying process is stable and led to the preparation of the nanocapsules in a spherical shape with the minimum average of the capsule's diameter. The optimized parameters obtained were 22 kV, 0.6 and 0.05 mL/h, 15 cm, and 5 _w/v_ % for applied voltage, flow rates of the shell and core solutions, the distance of needle and collector, and the concentration of the shell solution, respectively.