A Mass Spectrometer for Nanoparticles

摘要

Nano sized particles may be formed as unwanted by-products in combustion processes and also as useful products in innovative technologies. Besides combustion, evaporation/condensation techniques, pyrolysis and plasma processes are in use to produce nanostructured materials of pure substances as well as nanocomposites. Particle sizing is a necessary tool to investigate the particle formation process within the R&D frame and also to control the powder quality of production facilities. Further, particle detection and sizing is needed for emission control of nano sized particles, which has gained recent public attention. This short survey indicates that particle sizing is done with different intentions: For R&D purposes, a complete characterization of the particle size distribution may be required, including mass concentration, particle shape and, perhaps, chemical composition as function of size. Process control often requires an instantaneous ("online") knowledge of production rate and specific surface, while emission control focusses on mass concentration, size and long-term temporal behaviour. A systematic and complete measurement of all these quantities would require different measurement methods and tools. Mass spectrometry is a good compromise, since it provides simultaneous information on three key quantities of the particles: mass, size and their probability (i.e. distribution). Other quantities, like volume distribution and specific surface can readily be calculated from the measured data. Since the production of nano-particles is often associated with electrical charging of the particles, the application of mass spectrometry is straightforward, if the setup permits easy transportation and handling. Here we report on the development of a portable particle mass spectrometer (PMS) for charged nanoparticles in the size range 0.3 - 30 nm.