Ag/lamellar hosts composites: A route to morphology-controllable synthesis of Ag nanoparticles

摘要

An easy and novel routine are reported for the preparation of metallic silver nanoparticles (AgNPs) with controlled morphology, using Na ~+-magadiite swelled with hexadecyltrimethylammonium bromide (CTA ~+-magadiite) and a layered aluminophosphate with kanemite-type structure modified with n-dodecylammonium and n-butylammonium (but,dod-AlPO-kan) as hosts. For the preparation of the metallic AgNPs (Ag~0) in the interlamellar space, the CTA~+-magadiite and but,dod-AlPO-kan hosts were dispersed in N,N-dimethylformamide (DMF) solution with different AgNO _3 concentrations. DMF acts as reducing agent of Ag~+ ions leading to nanoparticles with disk-like morphology of magadiite silicate; these were characterized by TEM and UV-Vis spectroscopy. On the other hand, the AgNPs are intercalated in but,dod-AlPO-kan showing spherical-like morphology. The UV-Vis spectra of the nanocomposites based on Ag~0 and magadiite silicate show bands at 565 nm that can be attributed to Ag~0 nanodisks. The Ag-but,dod-AlPO-kan-based nanocomposites present a band at 422 nm attributed to the surface plasmon resonance of Ag~0 nanospheres. The results of transmission electron microscopy agree very well with XRD and UV-Vis analysis, indicating the formation of AgNPs with different morphologies using the two kinds of lamellar materials. The magadiite host has an important role in the synthesis of Ag nanodisks, because it controls the growth of nanoparticles inside the interlayer region with disk-like morphology due the high interlayer interactions of the silicate, leading to the growth of nanoparticles in only two directions (xy plane). On the other hand, when but,dod-AlPO-kan is used a sphere-like morphology is preferred due the best accommodation of AgNPs between the layers of aluminophosphate host.