Temperature dependence of the work function of free nanoparticle agglomerates

Starting point for this study was the experimentally found unusual high charge state of free submicron particles at elevated temperatures. By employing an aerosol setup with single electron counting efficiency it is shown for Pt and TiO 2 particles that the work function decreases with increasing temperature. Sign and amount of the work function decrease agree with the results of other experiments on extended surfaces, single crystals and clusters. On the basis of the reduced work function the observed high particle charge states are quantitatively understood.