We have developed a method of measuring the growth of nanoparticles during sol-gel glass formation based on labelling the particle with a fluorescent dye and determining the multiphoton excited decay of fluorescence anisotropy due to Brownian rotation. Multiphoton excitation is shown to give a higher dynamic range of measurement than one-photon excitation. We illustrate the sub-nanometre resolution and stability of our approach by detecting a 0.8-1.1 nm silica particle hydrodynamic mean radius increase in a tetramethylorthosilicate sol at pH 2.3 labelled with rhodamine 6G and observed over ≈4 weeks and also with a stable silica colloid of radius 6 nm, pH 8.9, labelled with a 6-methoxyquinoline-type dye.
- particle metrology
- fluorescence anisotropy decay
- multiphoton excitation
Karolin, J., Geddes, C. D., Wynne, K., & Birch, D. J. S. (2001). Nanoparticle metrology in sol-gels using multiphoton excited fluorescence. Measurement Science and Technology, 13(1), 21-27. https://doi.org/10.1088/0957-0233/13/1/303