Precious-Metal Nanoparticles Anchored onto Functionalized Halloysite Nanotubes

Natural halloysite nanotubes (HNTs) were functionalized with a silane coupling agent with the aim of tuning the loading rate and dispersion of precious-metal nanoparticles. The samples were characterized by FTIR spectroscopy, TEM, and XPS. The results indicated that a large number of precious-metal nanoparticles were anchored on the surface of the silanized HNTs, with an average diameter of ∼3 nm. The functionalized HNTs contain a large number of functional groups (−NH 2 or −SH groups) that have one lone electron pair and can form a chemical bond complex with nanoparticles. Because of bond formation between the nanoparticles and the functional groups, most of the nanoparticles (NPs) are anchored by the functional groups, resulting in the formation of nanoparticle–functional group complexes. Bond formation between the nanoparticles and the functional groups was demonstrated, and furthermore, atomic-level interfaces for NPs anchored onto functionalized HNTs were depicted. The chemical immobilization of precious-metal nanoparticles onto silanized HNTs could avoid particle aggregation and movement, thus leading to a higher catalytic efficiency.