In Situ SERS Monitoring Chemical Reactions Catalyzed By Ni Nanoparticles

Surface-enhanced Raman spectroscopy(SERS)has been proved to be a powerful tool for monitoring catalytic reactions on surface.However,SERS detection of catalytic reactions are limited to chemical reactions catalyzed by noble metals.As cheap metal catalysts Ni nanoparticles(NPs)offer additional advantages in terms of metal resources and cost.In situ SERS at the catalytic interface on Ni NPs which helps in understanding the reaction mechanism is instructive for rational design of high-performance Ni catalysts.In this work,Au@Ni superstructures synthesized by one-step assembly method were employed to investigate chemical reactions on Ni NP surface.The vibrational signal from molecules adsorbed on Ni catalysts can help in understanding the reaction mechanism and rationally designing cheap and high-performance catalysts.This work is a new experiment in monitoring chemical reactions on cheap catalysts and opens a new pathway for self-assembly,SERS and reaction mechanism.1.In situ SERS monitoring of catalytic reductions on Ni NPs: In the past few years,the reduction of 4-NTP to 4-ATP by sodium borohydride has been limited to the catalytic interface of noble metals.Bifunctional Au@Ni superstructures were employed for in situ SERS monitoring of Ni-catalyzed 4-NTP reduction.Firstly,the SERS-active Au NPs and catalytic-active Ni NPs were prepared,respectively.Bifunctional coresatellite nanostructures were synthesized by a one-step assembly method.The catalytic process on Ni NPs occured in the localized surface plasmon resonance field of Au NPs and then was recorded via in situ SERS.Four different types of molecule-metal combinations were fistly proposed and compared.The Au@Ni superstructures(the 4-NTP only on the Ni surface)can be used for nondestructive kinetic SERS monitoring of catalytic reduction on Ni surface.2.C-H arylation on Ni NPs discovered by in situ SERS monitoring: Bifunctional Au@Ni superstructures are employed for in situ SERS monitoring of Ni-catalyzed CC bond-forming reactions.Surprisingly,the reaction which was thought to be an Ullmann-type self-coupling reaction,was found to be a cross-coupling reaction proceeding by photoinduced aromatic C-H bond arylation.According to the discovery enabled by the in situ SERS monitoring,a series of biphenyl compounds are synthesized photocatalytically,at room temperature using the cheap Ni NP catalysts.