Facile synthesis of novel cage-like porous Ag-decorated silica nanotubes with enhanced catalytic activity

Novel cage-like porous Ag-decorated silica nanotubes (silica-Ag NTs) were synthesized as the porous silica NTs were firstly synthesized using the silk fibroin nanofibers (SF NFs) as sacrificial template via the sol-gel route and then supported the in situ decoration of Ag nanoparticles (NPs) via the hydrothermal route to derive porous silica@Ag NTs. SF NFs were prepared by electrospinning the SF solution via an electrospinning method, and then supported the self-assembly and packing of silica nanospheres when soaked in the Stöber-type sol-gel system consisting of tetraethoxysilane , water, ethanol and ammonia, and finally removed by calcination to produce the porous silica NTs. TEM and SEM observations indicated that the resultant silica NTs presented cage-like and porous hollow structure with controllable pore size from 139 ± 11 nm to 209 ± 64 nm. They induced the deposition of Ag nanoparticles (NPs) with the diameter of 5–10 nm when hydrothermally treated in the solution of AgNO 3 and played the reduction role in the conversion of AgNO 3 to Ag NPs. When exposed to the 4-nitrophenol/NaBH 4 solution, the resultant porous silica-Ag NTs showed catalytic activity for conversion of 4-nitrophneol to 4-aminophenol.