Recently, there has been a great deal of interest in fluorescent and upconverting rare earth-based nanoparticles for biomedical imaging and photodynamic therapy applications. While many of the widely explored upconverting contrast agents are comprised of fluoride or oxide crystal structures, very little work has been done to investigate the up- and downconversion emission in rare earth-doped carbon nanocomposites. Of particular interest, graphene-UCNP nanocomposites and sesquicarbide nanoparticles may offer a wide range of new applications when coupled with the extraordinary optical properties of rare earth-doped systems, such as potential use as nano-transducers. Carbon-based nanocomposites and sesquicarbides doped with rare earth elements were synthesized using the microwave and solvothermal methods with additional brief high temperature heat treatments. They were then characterized by XRD, visible and NIR excitation and emission spectroscopy, as well as Raman spectrsocopy. Tuning of the emission manifold ratios was explored through different compositions and size. Also, energy transfer between the emitting ions and the electronic states of the host structure was explored. Finally, cytotoxicity was tested, and cellular uptake of these nanomaterials was performed with confocal microscopy.
Nanotechnology is impacting the future of the military and aerospace. The increasing demands for high performance
and property-specific applications are forcing the scientific world to take novel approaches in developing programs and
accelerating output. CONTACT or Consortium for Nanomaterials for Aerospace Commerce and Technology is a cooperative nanotechnology research program in Texas building on an infrastructure that promotes collaboration between universities and transitioning to industry. The participants of the program include the US Air Force Research
Laboratory (AFRL), five campuses of the University of Texas (Brownsville, Pan American, Arlington, Austin, and
Dallas), the University of Houston, and Rice University. Through the various partnerships between the intellectual
centers and the interactions with AFRL and CONTACT's industrial associates, the program represents a model that addresses the needs of the changing and competitive technological world. Into the second year, CONTACT has expanded to twelve projects that cover four areas of research: Adaptive Coatings and Surface Engineering, Nano Energetics, Electromagnetic Sensors, and Power Generation and Storage. This paper provides an overview of the CONTACT program and its projects including the research and development of new electrorheological fluids with nanoladen suspensions and composites and the potential applications.
Degradation processes in confined polymeric films, with a thickness smaller or equal to 100 nm are of particular importance for future space missions and microelectronics applications. A simplified theoretical model for the evolution of free radicals in such films is proposed. The model takes into account the dependence of the glass transition temperature (T<sub>G</sub>) on the film thickness as well as the dependence of T<sub>G</sub> on the average molecular mass of the polymer (Fox-Flory equation), by exploiting the blob concept. It is assumed that the film thickness controls blobs' size. The time and temperature evolution of free radicals is desxcribed by dividing the main physical and chemical processes into two statistically independent steps. In the first step, the reactants diffuse towards a nanometer sized reaction volume. In the second step the proper chemical reaction between reactants occurs. Two possible chemical reactions are considered: the deactiviation of free radicals through chemical reactions with small molecules or free electrons and the recombination of free radicals. It is supposed that the diffusion of free radicals is a self-diffusion process that obeys a Williams-Landel-Ferry like temperature dependence. The temperature dependence of the diffusion coefficient of small molecules was assumed to obey a simple Arrhenius like dependence. This provides a simple theoretical approach for the modeling of the physical properties thin polymeric films subjected to degradation processes within the glass transition range and may be refined to assess the lifetime of such films in extreme environments.
A parallel analysis of radiation-induced and thermal-induced degradation of polyethyleneterephtalate (PET) films is presented. The complexity of the degradation process is analyzed as a first step in a better understanding of the effect of combined temperature and radiation on PET. electron spin resonance spectrometry, DC electrical measurements, differential scanning calorimetry, and mechanical tests were used to analysze the effect of different ioninzing radiation (such as gamma, electrons, and accelerated ions) on thin films of PET. Data on the thermal analysis of PET are presented and analyzed. This study aims to a better understanding and modeling of complex degradation processes, required for a more reliable assessment of the behavior of polymers subjected to the space environment.