Theranostic liposomes as effective drug delivery systems for the management of infections.

The effect of the primary knock-on atom (PKA) spectrum in radiation damage and the subsequent defect structure formation and their impact in deuterium (D) trapping has been investigated using computer simulations and surrogate ion irradiation experiments. The neutron spectrum for an 'ITER-like' divertor shape and parameters has been generated using ATTILA and SPECTER codes to identify the relevant PKA energies. It has been observed that 10 MeV boron (B) produces a PKA spectrum similar to that obtained from a reactor-like neutron spectrum. Experiments have been carried out with ions of gold (Au), B, helium (He) and D with energies ranging from 0.1 MeV-80 MeV for a fluence range of 1.3 × 10 18 ions m −2 -5 × 10 21 ions m −2 , and distinctly different PKA spectra have been produced. While 80 MeV Au ions produced dense and small clusters of interstitial defects (<10 nm), B produced large dislocation loops up to 60 nm in size. At room temperature, the imprint of the cascade is well captured by the vacancies due to their low mobility, and the vacancy defects observed in Au and B irradiation showed significant differences. Molecular dynamics simulations show that at PKA energies exceeding 150 keV, the fragmentation of the cascades takes place, which tends to limit the size of individual defects in the case of 80 MeV Au irradiation. A mechanism based on the competitive capture of mobile interstitials has been proposed to explain the observed large dislocation loops as well as dislocation lines in different irradiation experiments.

We report the growth and characterization of uniform-sized nanoparticles of cobalt on n-type silicon (100) substrates by swift heavy ion (SHI) irradiation. The Co thin films of 25-nm thicknesses were grown by e-beam evaporation and irradiated with two different types of ions, 45-MeV Li3+ and 100-MeV O7+ ions with fluences ranging from 1 × 1011 to 1 × 1013 ions/cm2. SHI irradiation, with the beam rastered over the area of the film, resulted in the restructuring of the film into a dense array of Co nanostructures. Surface topography studied by atomic force microscopy revealed narrowed size distributions, with particle sizes ranging from 20 to 50 nm, formed through a self-organized process. Ion fluence-dependent changes in crystallinity of the Co nanostructures were determined by glancing angle X-ray diffraction. Rutherford backscattering spectroscopy analysis showed the absence of beam-induced mixing in this system. Surface restructuring and beam-induced crystallization are the dominant effects, with the nanoparticle size and density being dependent on the ion fluence. Results are analyzed in the context of molecular dynamics calculations of electron-lattice energy transfer.

The difference in the defect structures produced by different ion masses in a tungsten lattice is investigated using 80 MeV Au7+ ions and 10 MeV B3+ ions. The details of the defects produced by ions in recrystallized tungsten foil samples are studied using transmission electron microscopy. Dislocations of type b = 1/2[111] and [001] were observed in the analysis. While highly energetic gold ion produced small clusters of defects with very few dislocation lines, boron has produced large and sparse clusters with numerous dislocation lines. The difference in the defect structures could be due to the difference in separation between primary knock-on atoms produced by gold and boron ions.

Ion beam induced dewetting of thin metallic films has emerged as a promising way to grow metallic nanoparticles in a controlled manner. Metal films tend to dewet from non-reactive substrates upon heating, forming islands, due to the high energies of metal surfaces and interfaces. Ion beam irradiation triggers the self organized formation of nanostructures, and allows control over nanoparticle size distributions, since dewetting is initiated by highly localized (in space and time) thermal spikes along the ion track. From 25 nm cobalt films grown by e-beam evaporation, followed by irradiation with 100 keV Ar + ions, a high density array of nanostructures is formed. AFM scans show their morphological evolution as a function of ion fluence; optimum fluences for narrow particles size distribution have been identified. Glancing angle XRD and Rutherford Backscattering Spectroscopy show evidence of increased substrate exposure as dewetting proceeds. RBS indicates that within the optimal fluence range for nanostructure formation, sputtering and ion beam mixing are not the significant effects in this system. We present ion beam induced dewetting as a well controlled method of forming nanostructured catalysts from metal films.