Valentina Dore

Silica nanoparticles for micro-particle imaging velocimetry: fluorosurfactant improves nanoparticle stability and brightness of immobilized iridium(III) complexes.

To establish highly luminescent nanoparticles for monitoring fluid flows, we examined the preparation of silica nanoparticles based on immobilization of a cyclometalated iridium(III) complex and an examination of the photophysical studies provided a good insight into the Ir(III) microenvironment in order to reveal the most suitable silica nanoparticles for micro particle imaging velocimetry (μ-PIV) studies. Iridium complexes covalently incorporated at the surface of preformed silica nanoparticles, [Ir-4]@Si500-Z, using a fluorinated polymer during their preparation, demonstrated better stability than those without the polymer, [Ir-4]@Si500, as well as an increase in steady state photoluminescence intensity (and therefore particle brightness) and lifetimes which are increased by 7-fold compared with nanoparticles with the same metal complex attached covalently throughout their core, [Ir-4]⊂Si500. Screening of the nanoparticles in fluid flows using epi-luminescence microscopy also confirm that the brightest, and therefore most suitable particles for microparticle imaging velocimetry (μ-PIV) measurements are those with the Ir(III) complex immobilized at the surface with fluorosurfactant, that is [Ir-4]@Si500-Z. μ-PIV studies demonstrate the suitability of these nanoparticles as nanotracers in microchannels.

Luminescent ruthenium(II) tris-bipyridyl complex caged in nanoscale silica for particle velocimetry studies in microchannels

Luminescence and imaging studies of 500 nm diameter colloidal silica stained with the transition metal complex [Ru(bpy)3Cl2], [Ru(bpy)3?SiNP], have been detailed and suggest that such particles are ideal for particle tracking velocimetry (PTV) or particle imaging velocimetry (PIV) for analysis of fluid flow in microchannels. Silica particles were synthesized using a modification to the St?ber synthesis to cage the transition metal complex within the core of the nanoscale particles. The particles [Ru(bpy)3?SiNP] exhibit luminescence at 620 nm, characteristic of the caged [Ru(bpy)3]2+?species with a lifetime of 790 ns upon excitation at 450 nm. A collection of the luminescence spectra from the images of the particles in a microchannel have the same profile as the spectra collected from solutions of [Ru(bpy)3?SiNP], confirming that the luminescence images are attributed to [Ru(bpy)3]2+?luminescence. PIV and PTV measurements from image sequences give flow velocities that match well with the theoretical velocity profile for a rectangular-sided microchannel of 100 ?m depth.