Functionalized chalcogenide thin films for early detection of plant diseases via spore detection

Abstract

This study investigates the functionalization of Ge-Se-Te chalcogenide thin films using various organosilane precursors, including TEOS, OTES, APTES, ImPTES and MPTMS, to render them more hydrophilic or hydrophobic, or impart surface charges. The integrity of the deposited hybrid layers was confirmed by proton Nuclear Magnetic Resonance spectroscopy after alkaline depolymerization of test samples. The modified surfaces were characterized by Water Contact Angle measurements, Scanning Electron Microscopy and Atomic Force Microscopy. The ability of these functionalized surfaces to immobilize individual or mixed spores of two different varieties, Venturia inaequalis and Penicillium expansum, both responsible for fruit tree diseases, was evaluated. The two spore varieties behaved similarly, whether alone or mixed. Neither spore variety adhered to very hydrophilic surfaces. While the percentage of immobilized Venturia inaequalis spores increased with the surface hydrophobicity, Penicillium expansum spores were not immobilized on highly hydrophobic surfaces. Venturia inaequalis spores, characterized by a very negative zeta potential, were very well immobilized on positively charged surfaces. Consequently, the best immobilization percentage for this spore variety was obtained for the surface functionalized with ImPTES, a precursor characterized by a stable positive charge of imidazolium group. Penicillium expansum spores were less sensitive to positive charges due to their less negative zeta potential. The highest immobilization percentage for this spore variety was obtained with the precursor TEOS. One explanation could be the formation of hydrogen bonds.