NMR investigation of Ag nanoparticles

Abstract

109Ag nuclear magnetic resonance (NMR) and relaxation measurements have been performed on two powder samples of Ag nanoparticles with average sizes of 20 nm and 80 nm. The measurements have been done in an external field of 9.4 T and in the temperature range 10 K < T < 280 K. The 109Ag NMR spectra for both samples have close to Lorentzian shapes and turn out to be mixtures of homogeneous and inhomogeneous lines. The linewidth Δν at room temperature is 1.3 kHz for both samples and gradually increases with decreasing temperature. Both the Knight shift (K) and the nuclear spin-lattice relaxation rate (1/T1) are observed to be almost identical to the values reported for the bulk Ag metal, whereby the Korringa ratio R(= K2T1T/S) is found to be 2.0 for both samples in the investigated temperature range.