Thermodynamics-Oriented Crystal Growth Enables Lignocellulose-Enticed Nanostructured Hydroxyapatite with Boosted Phosphorus Fertilizer Utility

Nanostructured hydroxyapatite (HAP) has been increasingly regarded as a promising substitute for commercial phosphorus fertilizers (CPFs) for sustainable agriculture. However, developing new starting materials for green synthesis and then disentangling the association of both HAP structural properties and soil microbes with the fertilizer functionality of HAP nanoparticles remain a challenge. Here, three typical refractory calcium phosphates (RCPs) were facilely transformed to nanoenabled HAP via lignocellulose-enticed recrystallization in a one-pot hydrothermal process. The HAP nanoparticles were endowed with three distinctive morphologies, resulting from thermodynamically oriented nanocrystallization. Soybean cultivation experiments demonstrated that the accumulation of P in the whole plant increased by 14.11-36.61% depending on the RCP-derived HAP as a nanoenabled P fertilizer (NPF), particularly in the developed fruit (2.60-24.74%), when compared to the CPF. The partial least-squares path model identified that the material properties including surface hydrophilicity, hydrodynamic particle size, and zeta potential as well as the recruited rhizobacteria collectively engaged the HAP-based NPFs in P uptake and subsequent use during plant growth. Thermodynamic computations revealed that the present lignocellulose during synthesis decreased total Gibbs free energy by approximately 2.36% compared to those with the absence of lignocellulose, thus configuring the thermodynamics-retrofitted improvements in these material properties of the HAP nanocrystals for their P fertilizer utility. With the established water-root-rhizobacteria synergetic linkage of P supply by the HAP-based NPFs, increasing c-planes in HAP nanocrystals to maximally expose reactive hydroxyl groups can rationalize a design of multifunctional HAP-based nanoagrochemicals.