The custom making of hierarchical micro/nanoscaled titanium phosphate coatings and their formation mechanism analysis

In this study, a series of hierarchical micro/nanoscaled titanium phosphate (TiP) coatings possessing various surface morphologies were successfully fabricated on titanium (Ti) discs. The hydrothermal reactions of Ti discs in hydrogen peroxide (H₂O₂) and phosphoric acid (H₃PO₄) mixed solution yield diverse topographies such as hemispheric clump, cylindrical rod, spherical walnut, micro/nano grass, micro/nano sheet, and fibrous network. And their crystal structures were mainly composed of Ti(HPO₄)₂·0.5H₂O, (TiO)₂P₂O₇, H₂TiP₂O₈, Ti(HPO₄)₂ and TiO₂. The morphology and crystal shape of the TiP coatings depend strongly on the mass ratio of H₂O₂/H₃PO₄, reaction temperature and water content. Besides, the formation mechanism of TiP coatings with diverse morphologies was explored from the perspective of energetics and crystallography. The mechanism exploration paved the way for custom-making TiP coatings with desirable micro/nanoscaled morphologies to meet specific application purposes. The in vitro cytological performances of TiP coatings were also evaluated by co-culturing with rat bone marrow stromal cells (BMSCs), demonstrating a positive prospect for their use in bone tissue engineering.