Detection of Chemical Compositions of Ultrafine Nanoparticles by a Vacuum Ultraviolet Photoionization Nucleation Aerosol Mass Spectrometer

A vacuum ultraviolet photoionization nucleation aerosol mass spectrometer (VUVPI-AMS) was utilized for detection of chemical compositions of ultrafine nanoparticles with size less than 100 nm. A commercial nano scanning mobility particle sizer (Nano-SMPS) was employed to size-select ultrafine nanoparticles and measure their size distribution. A special aerodynamic lens was developed to transfer and focus the ultrafine nanoparticle into the vacuum. After heated on the surface of the heater, the ultrafine nanoparticles were vaporized and changed into gas-phase molecules, followed by softly photoionization at their ionization energy thresholds by the VUV light emitted from a commercial 10.6 eV krypton discharge lamp. A home-made orthogonal acceleration reflection time-of-flight mass analyzer was adopted to measure the mass of ions. As representative examples , the dioctyl phthalate (DOP) ultrafine nanoparticles and the nucleation nanoparticles from the ozonolysis reaction of alpha-pinene with ozone were studied and their chemical compositions were obtained with molecular information.