How does substrate hydrophobicity affect the morphological features of reconstituted wax films and their interactions with nonionic surfactant and pesticide?

JOURNAL OF COLLOID AND INTERFACE SCIENCE

卷:575

Article

Hu, Xuzhi¹  Pambou, Elias¹  Gong, Haoning¹  Liao, Mingrui¹  Hollowell, Peter¹  Liu, Huayang¹  Wang, Weimiao^2,3  Bawn, Carlo⁴  Cooper, Jos⁵  Campana, Mario⁵  Ma, Kun⁵  Li, Peixun⁵  Webster, John R. P.⁵  Padia, Faheem⁶  Bell, Gordon⁶  Lu, Jian R.¹ 

[1] Univ Manchester, Sch Phys & Astron, Biol Phys Grp, Oxford Rd, Manchester M13 9PL, Lancs, England

[2] Univ Manchester, Dept Mat, Oxford Rd, Manchester M13 9PL, Lancs, England

[3] Univ Manchester, Natl Graphene Inst, Oxford Rd, Manchester M13 9PL, Lancs, England

[4] Univ Manchester, Sch Chem, Oxford Rd, Manchester M13 9PL, Lancs, England

[5] Rutherford Appleton Lab, STFC ISIS Facil, Didcot OX11 0QX, Oxon, England

[6] Jealotts Hill Int Res Ctr, Syngenta, Bracknell RG42 6EY, Berks, England

关键词: Wheat;    Triticum;    Plant waxes;    Deuterated wax;    Neutron reflection;    Spectroscopic ellipsometry;    Nonionic surfactant;    Pesticide;   

DOI  :  10.1016/j.jcis.2020.04.043

来源: Elsevier

【 摘 要 】

Hypothesis: Surfactants are widely used in agri-sprays to improve pesticide efficiency, but the mechanism underlying their interactions with the surface wax film on plants remains poorly understood. To facilitate physical characterisations, we have reconstituted wheat cuticular wax films onto an optically flat silicon substrate with and without octadecyltrimethoxysilane modification to control surface hydrophobicity. Experiments: Imaging techniques including scanning electron microscopy (SEM) unravelled morphological features of the reconstituted wax films similar to those on leaves, showing little impact from the different substrates used. Neutron reflection (NR) established that reconstituted wax films were comprised of an underlying wax film decorated with top surface wax protrusions, a common feature irrespective of substrate hydrophobicity and highly consistent with what was observed from natural wax films. NR measurements, with the help of isotopic H/D substitutions to modify the scattering contributions of the wax and solvent, revealed different wax regimes within the wax films, illustrating the impact of surface hydrophilicity on the nanostructures within the wax films. Findings: It was observed from both spectroscopic ellipsometry and NR measurements that wax films formed on the hydrophobic substrate were more robust and durable against attack by nonionic surfactant C12E6 solubilised with pesticide Cyprodinil (CP) than films coated on the bare hydrophilic silica. Thus, the former could be a more feasible model for studying the wax-surfactant-pesticide interactions. (C) 2020 Published by Elsevier Inc.

【 授权许可】

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