A general strategy for template-free and low-cost synthesis of inorganic hollow spheres

Inorganic hollow spheres have a great potential in many fields, such as calcium phosphate (Ca-3(PO4)(2)) as carriers of active ingredients and local delivery. They are typically synthesized by the methods that reply on template based strategies. However, the template residue and energy consumption during template removal are drawbacks. Currently developed template-free methods remain challenges such as time, cost and complicated procedures. In this paper, we introduce a general low-cost and template-free precipitation method with simple procedure. A series of inorganic hollow spheres, including calcium phosphate, calcium fluoride, strontium phosphate, strontium fluoride, barium phosphate and barium fluoride via magnesium were successfully synthesized, respectively. Based on these experimental results, a new model is proposed to explain the mechanism of the hollow inorganic spheres formation. This paper provides a general method to synthesize inorganic hollow spheres, which may have an important indication to other systems. (C) 2017 Elsevier B.V. All rights reserved.