Seed-Mediated Synthesis of Unusual Struvite Hierarchical Superstructures Using Bacterium

In this paper, struvite hierarchical, superstructures such as macroporous quasi-spheres constructed from small flakes are synthesized by using dittmarite seed crystals in Proteus mirabilis/urea aqueous solution at 30 +/- 2 degrees C. The struvite superstructures are used to support silver (Ag) nanoparticles, indicating that they may have applications such as catalyst carriers. Four control experiments are also performed for investigating the roles of the seed crystals, urea, and the bacterium Proteus mirabilis in the formation of the unusual. struvite superstructures. The results indicate that only rod-like or prism-like struvite crystals are formed without seed crystals or using magnesium phosphate seed crystals in Proteus mirabilis/urea solutions or utilizing ammonium carbonate instead of urea and the bacterium in the absence or presence of dittmarite seed crystals. This suggests that the bacterium, urea and the dittmarite seed crystals all play important roles in directing the struvite superstructures. The influence of aging time on the morphology and structure of struvite superstructures is also studied, indicating that the quasi-spherical struvite superstructures are transformed into tetragonal bipyramids or prismatic particles after a long aging time. The formation mechanism of the struvite superstructures is also explored. This study is very significant for synthesizing new and special functional materials and underlining the untapped potential of biological methods in expanding the scope of crystal engineering. Also, it will provide new insights into biomineralization mechanisms.