Understanding shape and morphology of unusual tubular starch nanocrystals

Abstract

Starch nanocrystals (SNC) are aptly described as the insoluble degradation byproducts of starch granules that purportedly display morphologies that are platelet-like, round, square, and oval-like. In this work, we reported the preparation of SNC with unprecedented tubular structures through sulfuric acid hydrolysis of normal maize starch, subsequent exposure to ammonia and relaxation at 4°C. High-resolution transmission electron microscopy observation clearly proved that the SNCs possess tubular nanostructures with polygonal cross-section. After further reviewing the transformations of SNC by acid hydrolysis, ammonia treatment, and curing time at 4°C, a mechanism for T-SNC formation is suggested. It is conjectured that T-SNC gradually self-assembles by combination of smaller platelet-like/square nanocrystals likely loosely aggregated by starch molecular chains from residual amorphous regions. This work paves the way for the pursuit of new approaches for the preparation of starch-based nanomaterials possessing unique morphologies.

Keywords: Ammonia (PubChem CID: 222); Amylopectin (PubChem CID: 439207); Amylose (PubChem CID: 192826); Chemical transformation; Corn starch (PubChem CID: 439341); Self-assembly; Starch nanocrystals; Sulfuric acid (PubChem CID:1118); Tubular structures; d-Glucose (PubChem CID: 5793); α-d-Glucose (PubChem CID: 79025).