Starch materials are subject to loss of initial characteristics due to the retrogradation degenerative effect, high hygroscopicity, and favoring the growth of the microorganisms, which reduces the shelf life of packaging. In this sense, the insertion of nanoparticulated CuO was evaluated for the best performance.CuO is a semiconductor that can improve optical, mechanical, and antimicrobial properties, enabling excellent promotion of starch films. The hot injection precipitation method was used to obtain CuO nanoparticles in the nanometric scale rapidly. The films were carried out from the starch homogenization in water and urea under temperature, followed by thermopressing at 120 C. As a result, the 1% CuO (w w À1 ) increased tensile strength from 0.87 ± 0.40 to 1.92 ± 0.09 MPa. Furthermore, the films containing nanoparticles showed a barrier property against radiation in the ultraviolet-visible spectrum, not observed for the micrometric scale. Such results were attributed to the superior opacity of the films generated by nanometric reinforcement. Concerning antimicrobial activity, the films containing CuO showed a fungistatic effect (33%) for the Alternaria alternata fungus, a microorganism very susceptible to carbohydrate-rich sources. Thus, the CuO-reinforced starch films improved physicochemical and biological properties, making them promissory candidates for commercial application.

Agriculture's importance in human lives and the economy has directed studies to improve crop production. An essential challenge for improving fertilizer e cacy is reducing losses due to leaching and increasing the nutrients supplies. In this context, biodegradable sachets stand out as internal packaging instead of direct insertion into the polymer matrix, facilitating the system processing and making it easier to adapt the soil's nutritional quantity. Thus, the present work aimed to increase the zinc oxide (ZnO) solubility by obtaining nanoparticles using top-down and bottom-up approaches and packaging them in montmorillonite (MMT) reinforced starch sachets. The different diameters and forms of the ZnO nanoparticles were evaluated to understand the solubility dependence on these parameters. In this way, the top-down process was performed for the attritor milling method allowing the nanoparticles with about 71 nm average diameter and greater homogeneity than the commercial one (approximately 174 nm). The milled ZnO nanoparticles presented better solubility than those synthesized bottom-up processes and the commercial ones, reaching a 90 to 100% solubility plateau in 48 h. Concerning starch sachets, the 1% MMT (w w − 1 ) insertion in the polymeric matrix promoted increased water vapor barrier and mechanical properties, improving the tensile strength. In the solubility test for nanoparticulate ZnO packed in sachets, similar behaviors to free ZnO were observed due to the high a nity of the starch matrix with water.Therefore, starch sachet systems with improved properties from the MMT reinforcement insertion showed as an alternative source of Zn 2+ ions to minimize losses during application.

Agriculture's importance in human lives and the economy has directed studies to improve crop production. An essential challenge for improving fertilizer efficacy is reducing losses due to leaching and increasing the nutrients supplies. In this context, biodegradable sachets stand out as internal packaging instead of direct insertion into the polymer matrix, facilitating the system processing and making it easier to adapt the soil's nutritional quantity. Thus, the present work aimed to increase the zinc oxide (ZnO) solubility by obtaining nanoparticles using top-down and bottom-up approaches and packaging them in montmorillonite (MMT) reinforced starch sachets. The different diameters and forms of the ZnO nanoparticles were evaluated to understand the solubility dependence on these parameters. In this way, the top-down process was performed for the attritor milling method allowing the nanoparticles with about 71 nm average diameter and greater homogeneity than the commercial one (approximately 174 nm). The milled ZnO nanoparticles presented better solubility than those synthesized bottom-up processes and the commercial ones, reaching a 90 to 100% solubility plateau in 48 h. Concerning starch sachets, the 1% MMT (w w− 1) insertion in the polymeric matrix promoted increased water vapor barrier and mechanical properties, improving the tensile strength. In the solubility test for nanoparticulate ZnO packed in sachets, similar behaviors to free ZnO were observed due to the high affinity of the starch matrix with water. Therefore, starch sachet systems with improved properties from the MMT reinforcement insertion showed as an alternative source of Zn2+ ions to minimize losses during application.

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