Synthesis and characterisation of spherical core-shell Ag/ZnO nanocomposites using single and two – steps ultrasonic spray pyrolysis (USP).

Graphical abstract Highlights • Core-shell Ag/ZnO nanocomposites were synthesized by USP method. • By XRD, Wurtzite (ZnO) and face-centered-cubic (Ag) structures have been identified. • 2-steps route gives consecutive precursor precipitation, improving silver deposition. • Environmental applications of Ag/ZnO synthesized samples are promising. • The optimum Ag+/Zn2+ = 0.2 molar ratio aims the highest photocatalytic activity (93%). Abstract Spherical core-shell Ag/ZnO nanocomposites were synthesised by ultrasonic spray pyrolysis (USP) method from zinc nitrate hexahydrate, Zn(NO 3) 2 ·6H 2 O (ZN) and silver nitrate, AgNO 3 (SN) precursors. Varying solution concentrations and equipment installations (either single − or two-step USP) allowing simultaneous and consecutive precipitation of Ag and ZnO were examined regarding their effect on final particle microstructure and photocatalytic properties. Morphological analyses revealed pure Ag/ZnO core-shell structure where ZnO secondary submicron sized particles formed by primary crystals with the size of 5–20 nm. Depending on the solution concentrations and USP installations, various distributions of Ag in the final microstructure was revealed. Photocatalytic analyses (all samples reached >45% MB degradation) confirm the all Ag/ZnO USP systems viability for environmental applications. The best result (93% of methylene blue (MB) elimination) is obtained for the sample with the maximum available surface, which strongly depends on particle morphology, size, and dispersion. Moreover, all samples synthesised by single step co-precipitation revealed higher dye elimination concerning ones with two steps precipitation due to the favoured distribution of silver nanoparticles in their microstructure and higher specific surface area. Moreover, samples with a uniform and homogeneous Ag distribution exhibited silver-induced enhancement of photocatalytic performance. [ABSTRACT FROM AUTHOR]