title: Direct imaging Au nanoparticle migration inside mesoporous silica channels.
abstract: Supported metal nanoparticle (NP) catalysts have been widely used in many industry processes and catalytic reactions. Catalyst deactivation is mainly caused by the sintering of supported metal NPs. Hence, understanding the metal NPs' sintering behaviors has great significance in preventing catalyst deactivation. Here we report the metal particle migration inside/between mesochannels by scanning transmission electron microscopy and electron energy loss spectroscopy via an in situ TEM heating technique. A sintering process is proposed that particle migration predominates, driven by the difference of gravitational potential from the height of the uneven internal surface of the mesopores; when the distance of the gold nanoparticles with a size of about 3 and 5 nm becomes short after migration, the coalescence process is completed, which is driven by an "octopus-claw-like" expansion of a conduction electron cloud outside the Au NPs. The supports containing an abundance of micropores help to suppress particle migration and coalescence. Our findings provide the understanding toward the rational design of supported industrial catalysts and other nanocomposites with enhanced activity and stability for applications such as batteries, catalysis, drug delivery, gas sensors, and solar cells.
authors.affiliation: Department of Chemistry and Shanghai Key Lab of Molecular Catalysis and Innovative Materials, State Key Laboratory of Molecular Engineering of Polymers and Advanced Materials Laboratory, Fudan University , Shanghai 200433, P.R. China.
authors.forename: Zhengwang
authors.initials: Z
authors.lastname: Liu
authors.forename: Renchao
authors.initials: R
authors.lastname: Che
authors.forename: Ahmed A
authors.initials: AA
authors.lastname: Elzatahry
authors.forename: Dongyuan
authors.initials: D
authors.lastname: Zhao
mesh_terms: D006046:Gold / Q000737:chemistry*; D053768:Metal Nanoparticles / Q000737:chemistry*; D046529:Microscopy, Electron, Transmission; D012822:Silicon Dioxide / Q000737:chemistry*
chemical_list: D006046:Gold; D012822:Silicon Dioxide
keywords: gold nanoparticles; in situ TEM; mesoporous materials; particle migration