Silver–Copper Hollow Nanoshells as Phase-Transfer Reagents and Catalysts in the Reduction of 4-Nitroaniline

Abstract

Cysteine-stabilized Ag–Cu hollow nanoshells are prepared by the coreduction of silver nitrate and cupric nitrate with sodium borohydride in the presence of sodium thiocyanate. Transmission electron microscopic measurements show that the resulting Ag–Cu nanoshells exhibit a rather uniform size of 57.2 ± 11.9 nm with a shell thickness of 7.9 ± 1.6 nm, and the hollow volume ratio is estimated to be ≈62%. High-resolution transmission electron microscopic studies show that the nanoshells are composed of nanocrystalline Ag and CuO in segregated domains. Consistent results are obtained in X-ray diffraction measurements. X-ray photoelectron spectroscopic analysis shows that the elemental composition of the nanoshells is consistent with the initial feed ratio of the metal salt precursors. When capped with 1-dodecanethiol, the hollow nanoshells become dispersible in apolar organic solvents and the cavity may be exploited for the effective phase-transfer of target molecules such as rhodamine 6G between water and organic media. The Ag–Cu nanoshells also show apparent catalytic activity toward the reduction of 4-nitroaniline by sodium borohydride, a performance that is markedly better than that of the solid counterparts and comparable to leading results in recent literature based on relevant metal catalysts.