Rich stochastic dynamics of co-doped Er: Yb fluorescence upconversion nanoparticles in the presence of thermal, nonconservative, harmonic and optical forces

NOME, RENE A.; SORBELLO, CECILIA; JOBBÁGY, MATÍAS; BARJA, BEATRIZ C.; SANCHES, VITOR; CRUZ, JOYCE S.; AGUIAR, VINICIUS F.

Optics InfoBase Conference Papers

OSA - The Optical Society

Lugar: San Diego, California; Año: 2017

Stochastic dynamics of individual co-doped Er:Yb upconversion nanoparticles (COEY NPs) were investigated from experiments and simulations. The COEY NPs were characterized by high-resolution scanning electron microscopy, dynamic light scattering, and zeta potential measurements. Single COEY NP measurements were performed by fluorescence upconversion micro-spectroscopy and optical trapping. The home-built apparatus was initially calibrated by performing individual trajectory measurements to determine diffusion coefficients in solution from displacement histograms, mean-squared displacement (MSD), and power spectra. MSDs from single COEY NP exhibited timedependent diffusion coefficient which was compared with Brownian dynamics simulations of a viscoelastic model of harmonically bound spheres. Experimental timedependent two-dimensional trajectories of individual COEY NP revealed correlated twodimensional nanoparticle motion. The measurements were compared with stochastic trajectories calculated in the presence of a non-conservative rotational force field. Overall, the complex interplay of COEY NP adhesion, thermal fluctuations and optical forces led to a rich stochastic behavior of these nanoparticles.