Screening the Formation of Silver Nanoparticles Using a New Reaction Kinetics Multivariate Analysis and Assessing Their Catalytic Activity in the Reduction of Nitroaromatic Compounds

On the basis of in situ selection utilizing a reaction kinetics parameter, a new and straightforward method for screening the formation of catalytically active silver-PVP nanoparticles is reported. The method utilizes a multivariate analysis for the optimization of the reactant concentrations in the synthesis of nanoparticles with an analytical response based on the ability of the nanoparticles formed to catalyze the reduction of p-nitrofenol in situ. The best synthetic conditions were selected, the nanoparticles fully characterized, and their catalytic properties with regard to the reduction of five nitroaromatic compounds, possessing different substituents at the para position, were determined. The kinetics analysis was based on the Langmuir-Hinshelwood semi-heterogeneous model. The results showed the greater ability of substrates to adsorb onto the nanoparticle surface compared with that of borohydride ions and that the substrates possessing an electron-withdrawing substituent are more catalytically favored. These differences are discussed in terms of substrate adsorption and of a linear free-energy relationship based on the Hammett plot.