Towards carbon-free flame spray synthesis of homogeneous oxide nanoparticles from aqueous solutions

► Homogeneous nanoparticles by flame-assisted spray pyrolysis of cheap aqueous nitrates. ► Nitrates of high volatility result in uniform powders by gas-to-particle conversion. ► Long high temperature droplet and particle residence times promote powder homogeneity. ► H2 as fuel allows carbon-free flame synthesis of homogeneous Bi2O3 nanoparticles.