INSITU DETECTION OF MONOVALENT COPPER IN AEROSOLS BY PHOTOEMISSION

In situ information on nanoparticle surface chemistry and modes of particle growth is obtained in gas suspension by the technique of photoelectric charging of particles (PCP) which depends on the surface chemical compositon as well as the electronic structure of the particles via the spectral dependence of the photoelectric yield. With CuCl particles, photoelectric charging is about 100 times more efficient compared to other divalent transition metal compounds. Therefore, particles containing monovalent Cu can be detected with extremely high sensitivity of below 10 ng/m3. In atmospheric aerosols emitted from volcanoes, the relation of solid state oxidation/reduction in Fe1-xCuxCl2 resulting in monovalent Cu for x < 0.4 is important. As an example of the PCP technique this relation is monitored in laboratory generated aerosols. The nanoparticles are also precipitated onto a substrate where their surface chemical composition is analyzed by XPS which is important for the interpretation of the results obtained by photoelectric charging.