SYNTHESIS AND APPLICATIONS OF MORPHOLOGICALLY CONTROLLED SILVER MICRO/NANOSTRUCTURES

Abstract

In this work, three morphologically controlled synthesis protocols of silver micro/nanostructures using chemical approach were developed. The detailed growth mechanisms were extensively studied. The first work was the morphology controlled synthesis of silver micro/nanoplates under an etching environment using hydrogen peroxide (H2O2) as a reducing agent. The results revealed that chloride ions (Cl-) were essential for creating etching environment capable of selective dissolution of single crystal and multiply twinned crystal, while leaving plate structures unaffected. The second work was the morphology controlled synthesis of silver chloride (AgCl) microstructures via a precipitation of silver ammine complex ([Ag(NH3)2]+) by an addition of Cl-. The growth mechanism suggested that the eight-pod family grew from the cubic seeds in Cl--rich environment while the six-pod family grew from an octahedral seeds in an NH4OH-rich environment. The third work was the morphology controlled synthesis of nanoporous silver microstructures via galvanic replacement of AgCl microstructures. The concerting reaction between oxidative etching of nanoporous silver microstructures and re-deposition of Ag atoms converts large silver structures to small structures. The research findings enabled a development of a large scale silver recovery protocol from industry and laboratory wastes by converting AgCl precipitates into highly pure silver microstructures (>99.99%). The recovered products could be directly employed as a raw material for silver jewelry applications.