*2.2. Etching of HNTs*

The etching of HNTs was mainly based on the method of Abdullayev et al., and some changes were made in the process of implementation [22]. Five grams of HNTs were added to 500 mL of sulfuric acid (1.0 M) and the dispersion was stirred and kept at 60 ◦C for 30 h. The treated HNTs (T-HNTs) were then washed with deionized water five times until their pH range was between 6 and 7. Finally, the samples were dried at 50 ◦C for 24 h and crushed into powder with a mortar.

### *2.3. Fabrication of T-HNTs-CIN Nanoparticles*

The method of T-HNTs loading CIN was mainly modified and implemented by referring to the method of Zou et al. [23]. T-HNTs and CIN were mixed in 30 mL anhydrous ethanol solution, stirred overnight, and then treated with ultrasound for 15 min. The suspension was vacuumed twice for 15 min to remove air to encapsulate CIN into the

cavity of HNT. Finally, the suspension was centrifuged to obtain CIN-loaded nanoparticles (T-HNTs-CIN) and dried at room temperature for 24 h.

#### *2.4. Preparation of the SA Composite Film*

The nanocomposite film was prepared by the solution casting method. First, 2 g sodium alginate powder was dissolved in 100 mL of distilled water containing glycerol (30 wt% relative to SA) and bathed in water at 50 ◦C for 30 min to prepare the sodium alginate solution. SA/T-HNTs-CIN dispersion was obtained by dispersing the T-HNTs-CIN nanoparticles in sodium alginate solution by loading a certain amount of CIN on T-HNT (5% by weight relative to SA). Simultaneously, the same amount of T-HNTs (5% by weight relative to SA) or CIN (The amount of CIN supported by 5 wt% T-HNTs) was added to the sodium alginate as the control. The prepared dispersions were poured into the polytetrafluoroethylene plate and dried at room temperature for 36 h to form the film. Then, 1% *w*/*v* CaCl2 solution was poured onto the film so that the film was completely covered by the solution. After the reaction for one minute, the CaCl2 solution was poured out and washed twice with distilled water. Finally, after drying for 48 h at room temperature, it was stored in a desiccator at 25 ◦C and 50% relative humidity. The manufactured films were identified as SA, SA/CIN, SA/T-HNTs, and SA/T-HNTs-CIN, respectively.
