Size- and shape-controlled synthesis of Prussian Blue nanoparticles by a polyvinylpyrrolidone-assisted crystallization process

The preparation of coordination polymer nanoparticles is currently the focus of research attention because of the advantage of increasing the specific surface area. In this paper, we report a facile method to prepare Prussian Blue (PB) nanoparticles with different particle sizes. Their particle sizes have a wide range from a few dozen nanometres to a submicrometre, depending on the synthetic conditions. The obtained particles can be divided into three categories: small (around 20 nm), medium-sized (around 100 nm), and large (in excess of 200 nm). The medium-sized and large particles are formed by oriented aggregation of fine nanoparticles, showing a mesocrystal conformation (i.e., pseudo-single crystal nature). Our results strongly suggested that non-classical crystallization dominates the present system, which can help to further control and understand the crystallization process of other coordination polymers. By means of N ₂ gas adsorption-desorption measurements, the nanoporosity and specific surface areas for typical samples with three different particle sizes are characterized. Among these samples, medium-sized PB particles show the highest surface area of 260 m ² g ^-1, while large PB particles exhibit very poor porosity. The results show that the gas uptakes of coordination polymers can be adjusted by the particle size and shape.