We present an accurate online method for the study of size-dependent evaporation of free nanoparticles allowing us to detect a size change of 0.1 nm. This method is applied to Ag nanoparticles. The linear relation between the onset temperature of evaporation and the inverse of the particle size verifies the Kelvin effect and predicts a surface energy of 7.2 J/m(2) for free Ag nanoparticles. The surface energy of nanoparticles is significantly higher as compared to that of the bulk and is essential for processes such as melting, coalescence, evaporation, growth, etc., of nanoparticles.

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Processes such as coalescence, sintering, and evaporation depend on the surface tension. We have evaluated the surface tension of free gold nanoparticles from the size-dependent evaporation data. A value of 8.78 N/m has been obtained, which is in very good agreement with other theoretical models, and the values deduced from the size-dependent lattice parameter. The value of surface tension on the sintering process of gold nanoparticles is discussed.

A velocity map imaging photoelectron spectrometer for the study of ultrafine aerosols with a table-top VUV laser and Na-doping for particle sizing applied to dimethyl ether condensation J. Chem. Phys. 138, 044202 (2013); 10.1063/1.4788620Aerosol charging and capture in the nanoparticle size range ( 6 -15 nm ) by direct photoionization and diffusion mechanismsIn the photocharging process, aerosol particles become electrically charged through interaction with high-energy photons, e.g., ultraviolet ͑UV͒ irradiation. Photon adsorption by particles leads to electron emission and, as a result, particles become positively charged. While maximum achievable charges have been described in previous studies of dependency on particle and irradiation parameters, the influence of photoemitted charges on the charging process was not taken into account. In this work it is shown that such charges interact with the particles, which heavily influences the entire process. This complex process ͑the charging of particles positively by photons and simultaneously negatively by ions͒ is described in this work by a set of differential equations. These differential equations are solved numerically and, with simplifying assumptions, analytically. Multicomponent polydisperse aerosol is considered. As was found by comparing the analytical and numerical solutions, analytical results coincide with numerical ones for a wide range of initial parameters ͑particle number concentration, diameter͒. The analytical expressions evaluated allow one to quantify the influence of guiding processes and the limits of the charging process, which is heavily influenced by the previously neglected free ions. Model results explain such phenomena as the experimentally observed decrease in particle charge through the increase in particle number concentration. As a result of this work, the particle charge distribution obtained by the photocharging process can now be considered a known function of aerosol and UV-irradiation parameters.

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