In Situ XAS Study on Growth of PVP‐Stabilized Cu Nanoparticles

Abstract Cu nanoparticles have been synthesized from copper acetate using NaBH 4 as a reducing agent and poly( N ‐vinyl‐2‐pyrrolidone) (PVP) as a stabilizing agent under an inert ambience. In‐situ time‐resolved X‐ray absorption spectroscopy (XAS) measurement, which include both X‐ray near edge structure (XANES) and extended X‐ray absorption fine structure (EXAFS) techniques, have been carried out in a specially designed measurement cell during the formation of Cu nanoparticles using a specialized computer controlled flow setup. Principal Component Analysis (PCA) and Multivariate Curve Resolution with Alternating Least Squares (MCR‐ALS) analysis have been successfully applied to the time‐resolved Cu K‐edge XANES data recorded during the growth of Cu nanoparticles. PCA of the XANES spectra predicted three chemical species present in the reaction solution including an intermediate species apart from the initial and the product species. From MCR‐ALS analysis of the Cu K‐edge XANES spectra, the oxidation state of the reaction intermediate species and the concentration profile of the constituents during the reactions have been determined. Finally the EXAFS spectra of the intermediate species has been extracted and analyzed to predict the local structure of Cu cations in this species.