Matrix-assisted synthesis of palladium nanocage and nanowires

Our study describes the synthesis of novel nanoscale Pd cage and wires whose sizes and shapes are templated by mesoporous matrices. The templates used are cubic phase MCM-48 and hexagonal phase C_nMCM-41 (n = 16, and 22), SBA-15, which have pore diameters of ∼3, ∼3.8, ∼4.7, and ∼9 nm, respectively. For Pd@MCM-48, the Pd metal forms spherical domains (∼ 38 nm) consisting of three dimensionally interconnected into Pd arrays; for Pd@SBA-15 and Pd@MCM-41, the Pd metal forms of one-dimensional wires. Etching out the matrix produces porous Pd cages (pore sizes of ∼1.5 - 2.0 nm) with retaining original domain sizes of ∼38 nm; similarly Pd@SBA-15 and Pd@MCM-41 afford freestanding Pd nanowires. All the materials are examined by TEM, XRD, BET, and EDAX analysis. Furthermore, the thermal behaviour of Pd nanowire is briefly described.