Date of Thesis

5-5-2015

Thesis Type

Masters Thesis

Degree Type

Master of Science in Chemical Engineering

First Advisor

Timothy M. Raymond

Abstract

Accurate measurements of particle surface tension are required for models concerning atmospheric aerosol nucleation and activation. However, it is difficult to collect sufficiently large volumes of atmospheric aerosol for use in typical instruments that measure surface tension, such as goniometers or Wilhelmy plates. In this work, a method that measures the surface tension of collected liquid nanoparticles using atomic force microscopy is presented. A film of particles is collected via impaction and probed using nanoneedle tips with the atomic force microscope (AFM). This micro-Wilhelmy method allows for direct measurements of surface tension of small amounts of sample. The micro-Wilhelmy method was verified using liquids whose surface tensions were known. Particles of oxidized ¿-pinene were then produced, collected, and analyzed using this method. Preliminary results show that oxidized ¿-pinene particles formed in dry conditions have a surface tension similar to that of pure ¿-pinene, and particles formed in wet conditions have a surface tension that is significantly higher.

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