Photochemical Synthesis of Hierarchical Multiple-Growth-Hillock Superstructures of Silver Nanoparticles on ZnO

Abstract

Hierarchical superstructures of Ag nanoparticles with novel morphology resembling multiple growth hillocks were synthesized for the first time using photochemical method through the screw-dislocation-driven, nanoparticle-mediated crystal growth mechanism. The Ag nanoparticles were in situ synthesized from the photoreduction of Ag + ions adsorbed on ZnO. The absence of organic capping agents in the synthesis protocol makes this photochemical approach suitable for preparing metal/semiconductor hybrid materials with clean metal/semiconductor interfaces that can find important applications in plasmon-assisted photocatalysis, photovoltaics, and plasmon-enhanced spectroscopies. Finally, we demonstrated that the photoluminescence properties of ZnO can be subtly modified by the photodeposited Ag nanostructures through synergistic mechanisms of surface plasmon−exciton resonant coupling and surface passivation.

Out-of-Substrate Ag–Ag2O Nanoplates: Surfactantless Photochemical Synthesis, Structural Evolution, and Mechanistic Study

“…We have recently reported that short-time (less than 10 min) UV illumination would yield multiple-growth-hillock-like superstructures of nanoparticles on ZnO. 23 The nanoparticle-mediated crystallization process was governed by screw dislocations under relatively low supersaturation. Note that the volume of the reaction solution is only about 100–200 μL.…”

“…(A) Small nanoplates obtained at 10 min, coexisting with the multiple-growth-hillock-like superstructures. 23 (B) Small nanoplates obtained at 30 min. (C) Close-up view of the small nanoplates obtained at 30 min.…”

“…The ZnO film was prepared using the method reported by us before. 23 Unless otherwise specified, all synthesis reactions were carried out in a concentrated (3–8 M) AgNO 3 aqueous solution. Ag–Ag 2 O nanoplates with different morphologies and sizes were obtained by adjusting the UV illumination time.…”

“…For photochemical synthesis, a ZnO film covered by aliquots of an aqueous solution of AgNO 3 containing 20% ethanol was illuminated with a UV lamp (wavelength: 365 nm): AgNO 3 was used as the precursor of Ag and ethanol as the hole scavenger. The ZnO film was prepared using the method reported by us before . Unless otherwise specified, all synthesis reactions were carried out in a concentrated (3–8 M) AgNO 3 aqueous solution.…”

“…We have recently reported that in situ photochemically synthesized nanoparticles can act as elementary structural units for further crystallization. 23 When the supersaturation is relatively low, the in situ synthesized nanoparticles further crystallize into multiple-growth-hillock-like superstructures via a screw-dislocation-driven crystallization mechanism. Herein, we extended our study to the crystallization of in situ synthesized nanoparticles under a high supersaturation level.…”