Confocal laser imaging and annealing of quantum-dot-coated silica colloidal crystals.

We demonstrate the ability to image, melt, and anneal repulsive electrostatic and attractive depletion colloidal crystals of quantum-dot-decorated SiO(2) microparticles (QDSs). QDS colloidal crystals showed increased thermal motion, melting, and convection only in the presence of CSLM imaging, which we attribute to quantum dot (QD) heating. We exploit this local heating effect to anneal a single defect-rich, polycrystalline domain.

Mobilization of colloidal particles by low-frequency dynamic stress stimulation.

Naturally occurring seismic events and artificially generated low-frequency (1 to 500 Hz) elastic waves have been observed to alter the production rates of oil and water wells, sometimes increasing and sometimes decreasing production, and to influence the turbidity of surface and well water. The decreases in production are of particular concern, especially when artificially generated elastic waves are applied as a method for enhanced oil recovery. The exact conditions that result in a decrease in production remain unknown.

Quantum dot-embedded microspheres for remote refractive index sensing.

We present a refractometric sensor based on quantum dot-embedded polystyrene microspheres. Optical resonances within a microsphere, known as whispering-gallery modes (WGMs), produce narrow spectral peaks. For sensing applications, spectral shifts of these peaks are sensitive to changes in the local refractive index.

Resonant effects in evanescent wave scattering of polydisperse colloids.

Measurements and predictions are reported to understand large variations in evanescent wave (EW) scattering intensities between different particles from the same batch of single mode, polydisperse colloids. Measured EW scattering intensity distributions are obtained for three different micrometer sized latex particles irreversibly deposited onto glass surfaces. Predicted EW scattering intensity distributions are obtained using measured particle size distributions as input in a Mie theory for the three-dimensional scattering of a sphere under EW illumination.

Interfacial colloidal sedimentation equilibrium. I. Intensity based confocal microscopy.

This paper reports confocal microscopy measurements of inhomogeneous colloidal sedimentation equilibrium profiles near planar wall surfaces for conditions when colloid dimensions are comparable to the characteristic gravitational length scale. The intensity based confocal method developed in this work enables real-space measurements of one-dimensional density profiles of Brownian colloids without identifying many single colloid centers in large imaging volumes. Measured sedimentation equilibrium profiles for single-phase interfacial fluids and for coexisting inhomogeneous fluid and solid phases are in agreement with a perturbation theory and Monte Carlo simulations within the local density approximation.

Evanescent wave excited luminescence from levitated quantum dot modified colloids.

Evanescent wave excited luminescence of quantum dot modified polystyrene (QDPS) colloids is investigated to measure potential energy profiles of QDPS colloids electrostatically levitated above a planar glass surface. Luminescence is characterized for three different-sized PS colloids modified with three different-sized QDs using confocal microscopy, emission spectra, flow cytometry, and temporal measurements of levitated and deposited colloids. Colloid-surface potential energy profiles constructed from scattering and luminescence intensity data display excellent agreement with each other, theoretical predictions, and independently measured parameters.

Measurement and interpretation of particle-particle and particle-wall interactions in levitated colloidal ensembles.

This paper reports measurements of particle-wall and particle-particle interactions in levitated colloidal ensembles using integrated total internal reflection microscopy (TIRM) and video microscopy (VM) techniques. In levitated colloidal ensembles with area fractions of phiA = 0.03-0.