Hydrogel Embedding Enables Enhanced Leaf Deposition and Bioavailability of Fe-Based Engineered Nanoparticles

Nanofertilizers comprising engineered nanoparticles (ENPs)
have
great potential in sustainable agriculture due to their strong capabilities
of improving crop yields. As an effective fertilization strategy,
foliar spraying could lead to broken and splashed ENP droplets, resulting
in inaccurate leaf targeting and potential environmental contamination.
Herein, we propose embedding Fe-based ENPs into a supramolecular hydrogel
to effectively enhance the deposition amount on leaves and thus the
bioavailability. The proper rheological properties of the hydrogel
droplets and their robust interaction with soybean leaf simultaneously
reduce the droplet rebound and fragmentation, especially under elevated
impact speeds, resulting in up to 168.9% more droplet deposition compared
to the ENP suspension. Computational fluid dynamics simulation analysis
suggests that the contact angle is a key sensitive factor influencing
the dynamic deposition behavior of the hydrogel droplet. A 15% reduction
in the contact angle results in a 14% reduction of the highest bouncing
height. The incorporation of ENPs enhances the viscous dissipation
rate by 7.4% in comparison with pure hydrogel droplets. The hydrogel
embedding also causes a 1.5-fold increase in ENP uptake compared to
that of the ENP suspension. The hydrogel embedding delivers a reduction
of 80% in the ENP application amount, compared to ENP suspensions,
while achieving a 28% increase in the fresh weight of soybean seedlings.
This work provides an effective method to enhance the deposition of
ENPs during foliar application.