Improvement of the reproducibility in LIBS single levitated aerosol particle analysis based on particle size-selectivity of photophoretic optical trap

To improve the reproducibility of single particle analysis with LIBS, we study the particle size selectivity of photophoretic optical trap. Firstly, the photophoretic force is theoretically simulated and size selectivity in a Gaussian trapping beam is analyzed. Then, the particle size is statistically examined under different power of the trapping Gaussian beam. The results indicate the larger particles are selected by the trap with higher laser power, which is in good agreement with the theoretical expectation. In addition, comparing the particle size distribution of hollow beam trapping with that of Gaussian beam, we found the particle size distribution in hollow beam trapping is broader, which is due to the larger freedom of radiating area on the particle in the hollow beam. Finally, the reproducibility of single particle LIBS is testified. The results show better reproducibility can be achieved with Gaussian beam as a narrower range in particle size is obtained by the trap. This work suggest optical trap can provide a useful tool to control the freedom of particle size and therefore improve the reproducibility of single particle analysis.