How to effectively and greenly prepare multi-scale structural starch nanoparticles for strengthening gelatin film (ultrasound-Fenton system).

Ultrasound (US) assisted with Fenton (US-Fenton) reaction was developed to efficiently and greenly prepare starch nanoparticles (SNPs) that were employed as nanofillers to enhance gelatin (G) film properties. Compared to Fenton reaction alone, US-Fenton reaction significantly improved preparation efficiency and dispersion of SNPs (p < 0.05). An optimal US-Fenton reaction parameter (300 mM HO, ascorbic acid 55 mM, US 45 min) was found to prepare SNPs with uniform sizes (50-90 nm) and low molecular weight (M 7.91 × 10 Da). The XRD, FT-IR, and SAXS analysis revealed that the US-Fenton reaction degraded the amorphous and crystalline zones of starch from top to down, leading to the collapse of the original layered structure starch and the progressive formation of SNPs. The different sizes of SNPs were selected to prepare the composite films. The G-SNP3 film (with 50-90 nm SNPs) showed the most outstanding UV blocking, tensile, and barrier properties. Especially, the tensile strength of G-5%SNP3 film (containing 5 % SNPs) increased by 156 % and 6 % over that of G film and G-5%SNP2 film (containing 5%SNPs with 100-180 nm), respectively. Therefore, the nanomaterial was promisingly prepared by the US-Fenton system and provided a strategy for designing and producing nanocomposite films.