Two-Photon Fluorescence Tracking of Colloidal Clusters
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In situ dynamics of colloidal cluster formation from nanoparticles is yet to be addressed. Using two-photon fluorescence (TPF) that has been amply used for single particle tracking, we demonstrate in situ measurement of effective three-dimensional optical trap stiffness of nanoparticles and their aggregates without using any position sensitive detector. Optical trap stiffness is an essential measure of the strength of an optical trap. TPF is a zero-background detection scheme and has excellent signal-to-noise-ratio, which can be easily extended to study the formation of colloidal cluster of nanospheres in the optical trapping regime. TPF tracking can successfully distinguish colloidal cluster from its monomer.
KeywordsOptical tweezers Fluorescence Trapping
DG thanks the support from the Wellcome Trust Senior Research Fellowship (UK) and Swarnajayanti Fellowship from DST, India for funding. DR and DM thank CSIR and UGC, India respectively for graduate fellowship. We thank Mrs. S. Goswami for language check.
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