Metastable materials have received extensive attention due to their unique physical and chemical properties, which are different from those of the thermodynamically stable phase. However, the variety of reported metastable materials is still very limited owing to difficulties in the effective synthesis of samples, as they can easily transform into their corresponding stable phases. Therefore, an important task for material and chemical scientists is to search for effective strategies that allow controllable synthesis of various metastable materials with new and fascinating functions.

The team, which is led by Huogen Yu from Wuhan University of Technology, has controllably synthesized hierarchically porous metastable β-Ag2WO4 hollow nanospheres with a diameter of 50–500 nm by a facile precipitation reaction between AgNO3 and Na2WO4 in the presence of poly methacrylic acid (PMAA). The resultant metastable β-Ag2WO4 hollow nanospheres show a large specific surface area (165.5 m2/g). In addition, the group found that the PMAA not only provides a spherical soft template to induce the formation of hollow nanospheres, but also functions as an inhibitor to prevent the phase transformation from thermodynamically unstable β-Ag2WO4 to stable α-Ag2WO4.

In testing, the nanospheres were shown to decompose methyl orange and phenol aqueous solutions with a high photocatalytic activity and could offer a promising approach towards solving environmental and energy-related issues. Furthermore, owing to its hierarchically porous structure, the material also has various potential applications in chemical reactors, drug-delivery carriers, solar cells, catalysis, and separation and purification fields.

More details can be found in the journal Nanotechnology.