The depuration fate of the mixtures of CdS/ZnS quantum dots (QDs) with different surface coatings on mangrove and wheat root epidermis: results from a novel method

Abstract

Background: The depuration fate of mixtures of metal-based quantum dots (QDs) in root epidermis is an important factor that determined their follow-up transportation and transformation processes in plant. However, the related mechanisms are poorly understood due to the lack of appropriate quantitative methods. Results: In our study, a novel method for in situ determination of mixtures of CdS/ZnS QDs with different surface coatings located on root epidermis was developed using an excitation–emission matrix combined with multi-way parallel factor analysis (PARAFAC) and n-way partial least squares (n-PLS). Then, the fates of CdS/ZnS QDs on mangrove and wheat root epidermis were investigated using the established method. During the rapid dissipation stage, intracellular and intercellular degradation of metal ions instead of transportation and rhizophytic bacteria degradation was the predominant reasons for the reduction in the CdS/ZnS QDs mixtures. However, due to vertical migration of CdS/ZnS QDs in the slow depuration stage, negative linear relationships were observed between the Ks values of oleic acid-CdS/ZnS QDs and the polarity index of the root epidermis (p < 0.05), which further indicated a difference between the single and mixture QDs. Conclusions: To our knowledge, this study provided a new approach to investigate the fate of QDs located on root epidermis and revealed the related mechanisms.