Evaporation of free PbS nanoparticles: evidence of the Kelvin effect.

The size-dependent evaporation of free-spherical PbS nanoparticles has been investigated by in-flight sintering of size-classified aerosols. The temperature (T(ev)) at which the particle size decreases due to evaporation is found to be size dependent and decreases with decreasing particle size. A linear relationship between the evaporation temperature and the inverse of the particle size is obtained as is the case with size-dependent melting of nanoparticles. This gives a direct evidence of the Kelvin effect and allows one to estimate the surface energy of nanoparticles. The surface energy of PbS nanoparticles has been found to be 2.45 J m(2).