ABSTRACT
While the dominant defects which control non-radiative recombination and long-range interstitial diffusion in CdTe correspond to Cd vacancies and Te anti-sites, the short-range diffusion of Te and Se interstitials between these defects is also of interest, since they both play a role in defect passivation. In addition, since CdTe thin films are typically polycrystalline and may also involve interfaces with materials with different lattice constants, the effects of strain are also of interest. Here we present the results of molecular dynamics (MD) simulations of Te interstitial diffusion in zincblende CdTe for values of the triaxial strain ranging from -2% (compressive) strain to +2.8% (tensile) strain. By carrying out MD simulations of Te interstitial diffusion over a range of temperatures, and then carrying out Arrhenius fits, we have determined the effective activation barrier E_a and prefactor D_0 for each value of the global strain. We find that both E_a and D_0 exhibit non-monotonic behavior, increasing with both compressive and tensile strain. We also present an analysis of the key diffusion pathways for 3 different values of the strain which explains the non-monotonic strain dependence obtained in our simulations. Our results also indicate that in each case, the diffusion of interstitial Te involves a variety of concerted events with a wide range of activation barriers. .
ABSTRACT
Detection of singlet oxygen is of great importance for a range of therapeutic applications, particularly photodynamic therapy, plasma therapy and also during photo-endosomolytic activity. Here we present a novel method of intracellular detection of singlet oxygen using biocompatible polymeric nanosensors, encapsulating the organic fluorescent dye, Singlet Oxygen Sensor Green (SOSG) within its hydrophobic core. The singlet oxygen detection efficiency of the nanosensors was quantified experimentally by treating them with a plasma source and these results were further validated by using Monte Carlo simulations. The change in fluorescence intensity of the nanosensors serves as a metric to detect singlet oxygen in the local micro-environment inside mammalian cancer cells. We used these nanosensors for monitoring singlet oxygen inside endosomes and lysosomes of cancer cells, during cold plasma therapy, using a room-temperature Helium plasma jet.
Subject(s)
Photochemotherapy , Singlet Oxygen , Animals , Fluorescent Dyes , Oxygen , Photosensitizing AgentsABSTRACT
Cementitious composites, including ferrocement and continuous fiber reinforced cement, are increasingly considered for building construction and repair. One alternative in processing of these composites is to infiltrate the reinforcement (continuous fibers or chicken mesh) with a flowable cementitious slurry. The relatively high density of cementitious binders, when compared with polymeric binders, are a setback in efforts to introduce cementitious composites as lower-cost, fire-resistant, and durable alternatives to polymer composites. Aeration of the slurry is an effective means of reducing the density of cementitious composites. This approach, however, compromises the mechanical properties of cementitious binders. An experimental program was undertaken in order to assess the potential for production of aerated slurry with a desired balance of density, mechanical performance, and barrier qualities. The potential for nondestructive monitoring of strength development in aerated cementitious slurry was also investigated. This research produced aerated slurries with densities as low as 0.9 g/cm³ with viable mechanical and barrier qualities for production of composites. The microstructure of these composites was also investigated.
