Size-dependent elasticity of gold nanoparticle measured by atomic force microscope based nanoindentation

Elasticity is one of the key properties in gold nanoparticles (AuNPs) and plays an essential role in the process design and applications. In this work, we have proposed an Argon plasma based technique to obtain well dispersed and pure AuNPs without surface functional groups. Our investigation on the size-dependent elasticity focused on the AuNPs with the size ranging from 2 nm to 12 nm by using an atomic force microscope based nanoindentation technique under the peakforce quantitative nanomechanical mapping mode. The results show clearly that when the AuNPs are smaller than 6 nm, there is a significant increase in the elasticity as the smallest nanoparticles display a twofold higher elastic modulus of ∼140 GPa compared to bulk gold. Our result provides important experimental evidence that contributes to a better understanding of the size-property relations as well as process design in AuNPs, and it also can be applied to measure the mechanical properties in a wide range of nano-objects.