There continues to be a significant increase in the number and complexity of hydrophobic nanomaterials that are engineered for a variety of commercial purposes making human exposure a significant health concern. This study uses a combination of biophysical, biochemical and computational methods to probe potential mechanisms for uptake of C60 nanoparticles into various compartments of living immune cells. Cultures of RAW 264.7 immortalized murine macrophage were used as a canonical model of immune-competent cells that are likely to provide the first line of defense following inhalation. Modes of entry studied were endocytosis/pinocytosis and passive permeation of cellular membranes. The evidence suggests marginal uptake of C60 clusters is achieved through endocytosis/pinocytosis, and that passive diffusion into membranes provides a significant source of biologically-available nanomaterial. Computational modeling of both a single molecule and a small cluster of fullerenes predicts that low concentrations of fullerenes enter the membrane individually and produce limited perturbation; however, at higher concentrations the clusters in the membrane causes deformation of the membrane. These findings are bolstered by nuclear magnetic resonance (NMR) of model membranes that reveal deformation of the cell membrane upon exposure to high concentrations of fullerenes. The atomistic and NMR models fail to explain escape of the particle out of biological membranes, but are limited to idealized systems that do not completely recapitulate the complexity of cell membranes. The surprising contribution of passive modes of cellular entry provides new avenues for toxicological research that go beyond the pharmacological inhibition of bulk transport systems such as pinocytosis.

: We present details of the homo-epitaxial growth of Yb:YAG onto a <100> oriented YAG substrate by pulsed laser deposition. Material characterization and initial laser experiments are also reported, including the demonstration of laser action from the 15 µm-thick planar waveguide generating 11.5 W of output power with a slope efficiency of 48 %. This work indicates that under appropriate conditions, high-quality single-crystal Yb:YAG growth via pulsed laser deposition is achievable with characteristics comparable to those obtained via conventional crystal growth techniques.

Abstract:We demonstrate the first Tm-doped yttria planar waveguide laser to our knowledge, grown by pulsed laser deposition. A maximum output power of 35 mW at 1.95 µm with 9% slope efficiency was achieved from a 12 µm-thick film grown on a Y 3 Al 5 O 12 substrate.

In this paper we present a passively Q-switched Yb:Y 2 O 3 waveguide laser using evanescent-field interaction with an atmospheric-pressure-chemical-vapour deposited graphene saturable absorber. The waveguide, pumped by a broad area diode laser, produced an average output power of 456 mW at an absorbed power of 4.1 W. The corresponding pulse energy and peak power were 330 nJ and 2 W, respectively. No graphene damage was observed, demonstrating the suitability of top-deposited graphene for high-power operation.

The first, to the best of our knowledge, Q-switched operation of a pulsed-laser-deposited waveguide laser is presented. A clad Yb:Y(2)O(3) waveguide was Q-switched using an output coupling mirror coated with a single layer of graphene deposited by atmospheric pressure chemical vapor deposition. During continuous-wave operation, a maximum power of 83 mW at a slope efficiency of 25% was obtained. During Q-switched operation, pulses as short as 98 ns were obtained at a repetition rate of 1.04 MHz and a central wavelength of 1030.8 nm.