Tumor radiation response enhancement by acoustical stimulation of the vasculature.

We have discovered that ultrasound-mediated microbubble vascular disruption can enhance tumor responses to radiation in vivo. We demonstrate this effect using a human PC3 prostate cancer xenograft model. Results indicate a synergistic effect in vivo with combined single treatments of ultrasound-stimulated microbubble vascular perturbation and radiation inducing an over 10-fold greater cell kill with combined treatments. We further demonstrate with experiments in vivo that induction of ceramide-related endothelial cell apoptosis, leading to vascular disruption, is a causative mechanism. In vivo experiments with ultrasound and bubbles permit radiation doses to be decreased significantly for comparable effect. We envisage this unique combined ultrasound-based vascular perturbation and radiation treatment method being used to enhance the effects of radiation in a tumor, leading to greater tumor eradication.

Optimizing the acquisition and analysis of confocal images for quantitative single-mobile-particle detection.

Quantification of the fluorescence properties of diffusing particles in solution is an invaluable source of information for characterizing the interactions, stoichiometry, or conformation of molecules directly in their native environment. In the case of heterogeneous populations, single-particle detection should be the method of choice and it can, in principle, be achieved by using confocal imaging. However, the detection of single mobile particles in confocal images presents specific challenges. In particular, it requires an adapted set of imaging parameters for capturing the confocal images and an adapted event-detection scheme for analyzing the image. Herein, we report a theoretical framework that allows a prediction of the properties of a homogenous particle population. This model assumes that the particles have linear trajectories with reference to the confocal volume, which holds true for particles with moderate mobility. We compare the predictions of our model to the results as obtained by analyzing the confocal images of solutions of fluorescently labeled liposomes. Based on this comparison, we propose improvements to the simple line-by-line thresholding event-detection scheme, which is commonly used for single-mobile-particle detection. We show that an optimal combination of imaging and analysis parameters allows the reliable detection of fluorescent liposomes for concentrations between 1 and 100 pM. This result confirms the importance of confocal single-particle detection as a complementary technique to ensemble fluorescence-correlation techniques for the studies of mobile particle.

Quantum junction solar cells.

Colloidal quantum dot solids combine convenient solution-processing with quantum size effect tuning, offering avenues to high-efficiency multijunction cells based on a single materials synthesis and processing platform. The highest-performing colloidal quantum dot rectifying devices reported to date have relied on a junction between a quantum-tuned absorber and a bulk material (e.g., TiO(2)); however, quantum tuning of the absorber then requires complete redesign of the bulk acceptor, compromising the benefits of facile quantum tuning. Here we report rectifying junctions constructed entirely using inherently band-aligned quantum-tuned materials. Realizing these quantum junction diodes relied upon the creation of an n-type quantum dot solid having a clean bandgap. We combine stable, chemically compatible, high-performance n-type and p-type materials to create the first quantum junction solar cells. We present a family of photovoltaic devices having widely tuned bandgaps of 0.6-1.6 eV that excel where conventional quantum-to-bulk devices fail to perform. Devices having optimal single-junction bandgaps exhibit certified AM1.5 solar power conversion efficiencies of 5.4%. Control over doping in quantum solids, and the successful integration of these materials to form stable quantum junctions, offers a powerful new degree of freedom to colloidal quantum dot optoelectronics.

Colloidal-quantum-dot photovoltaics using atomic-ligand passivation.

Colloidal-quantum-dot (CQD) optoelectronics offer a compelling combination of solution processing and spectral tunability through quantum size effects. So far, CQD solar cells have relied on the use of organic ligands to passivate the surface of the semiconductor nanoparticles. Although inorganic metal chalcogenide ligands have led to record electronic transport parameters in CQD films, no photovoltaic device has been reported based on such compounds. Here we establish an atomic ligand strategy that makes use of monovalent halide anions to enhance electronic transport and successfully passivate surface defects in PbS CQD films. Both time-resolved infrared spectroscopy and transient device characterization indicate that the scheme leads to a shallower trap state distribution than the best organic ligands. Solar cells fabricated following this strategy show up to 6% solar AM1.5G power-conversion efficiency. The CQD films are deposited at room temperature and under ambient atmosphere, rendering the process amenable to low-cost, roll-by-roll fabrication.

N-type colloidal-quantum-dot solids for photovoltaics.

N-type PbS colloidal-quantum-dot (CQD) films are fabricated using a controlled halide chemical treatment, applied in an inert processing ambient environment. The new materials exhibit a mobility of 0.1 cm(2) V(-1) s(-1) . The halogen ions serve both as a passivating agent and n-dope the films via substitution at surface chalcogen sites. The majority electron concentration across the range 10(16) to 10(18) cm(-3) is varied systematically.