Amorphization of metal nanoparticles and the quantum confinement effect

When a metal particle is reduced to several nanometers in diameter, it will exhibit an electronic structure with discrete energy levels due to the quantum confinement effect. The current－voltage (I－V) measurements based on single－electron spectroscopy show fine structures in the I－V curves of crystalline Pd nanoparticles caused by the discrete energy levels, while amorphous Pd nanoparticles of similar particle size have I-V curves with equidistant Coulomb staircases. The suppression of the quantum confinement effect in the amorphous state results from the combination of a static effect due to the disorder and a dynamic effect caused by electron－electron scattering. This indicates that the degree of the atomic order of a nanoparticle plays an equally important role as its size in determining its quantum or classical nature，and causes the suppression of quantum confinement in the amorphous particle.