Influence of CuO Nanoparticle Aspect Ratio and Surface Charge on Disease Suppression in Tomato (Solanum lycopersicum)

Nanoparticles (NPs) have been shown to deliver micronutrientstoplants to improve health, increase biomass, and suppress disease.Nanoscale properties such as morphology, size, composition, and surfacechemistry have all been shown to impact nanomaterial interactionswith plant systems. An organic-ligand-free synthesis method was usedto prepare positively charged copper oxide (CuO) nanospikes, negativelycharged CuO nanospikes, and negatively charged CuO nanosheets withexposed (001) crystal faces. X-ray photoelectron spectroscopy measurementsshow that the negative charge correlates to increased surface concentrationof O on the NP surface, whereas relatively higher Cu concentrationsare observed on the positively charged surfaces. The NPs were thenused to treat tomato (Solanum lycopersicum) grown in soil infested with Fusarium oxysporum f. sp. lycopersici under greenhouseconditions. The negatively charged CuO significantly reduced diseaseprogression and increased biomass, while the positively charged NPsand a CuSO4 salt control had little impact on the plants.Self-assembled monolayers were used to mimic the leaf surface to understandthe intermolecular interactions between the NPs and the plant leaf;the data demonstrate that NP electrostatics and hydrogen-bonding interactionsplay an important role in adsorption onto leaf surfaces. These findingshave important implications for the tunable design of materials asa strategy for the use of nano-enabled agriculture to increase foodproduction.