A substrate-independent fabrication of hollow sphere arrays via template-assisted hydrothermal approach and their application in gas sensing

•A colloidal crystal-assisted hydrothermal method was proposed to fabricate hollow sphere arrays.•Various hollow sphere arrays were in-situ fabricated on desired substrates.•The hollow sphere arrays can be controlled in microstructures and sizes.•The as-fabricated Fe2O3 hollow sphere arrays show excellent gas sensing performances.