Foliar fertilization of crops has been researched since the 1950's. The Wikipedia article is short, but decent: https://en.wikipedia.org/wiki/Foliar_feeding

Nano-P fertilisers may be foliar absorbed depending on their particle size. If the particle size is well < 100 nm, then it can be absorbed after foliar fertilisation through the cuticle as well as through stomata.

for example, dissolved potassium phosphate in solution is smaller in size than nano potassium phosphate fertilizer particles as it dissociates into K⁺ and PO₄³⁻ ions. In ionic form it will be absorbed much more rapidly by the plant foliage than as nano size formulation (

Yes, plants can absorb nano-phosphate (NPs) through their aerial parts, primarily via foliar application. Nanoparticles (NPs) have unique physicochemical properties such as a high surface area, greater solubility, and enhanced mobility, which enable them to penetrate plant surfaces efficiently.

Mechanism of Nano-Phosphate Absorption Through Aerial Parts