Cross section measurements of the reactions induced by deuteron particles on ¹³C

Nuclear reactions induced by deuterons have been found to be an ideal analysis tool for depth profiling of light elements in the first microns of materials. In particular, the nonresonant nuclear reactions (d, p), (d, α) and (d, t) are well adapted to determine depth distributions of C and C in a single measurement. Nevertheless, only the cross section of the C(d, p)C nuclear reaction is well known for various experimental configurations. Thus, we measured the differential cross sections of the C(d, p)C, C(d, α)B, C(d, α)B and C(d, t)C nuclear reactions. A thin C foil (83 nm thick) was used and the measurements were performed at deuteron energies from 0.5 to 1.65 MeV for different laboratory angles of detection (135°, 150° and 165° with respect to the incident beam). Then, the results obtained in this work were compared to cross sections measured by Marion and Weber for a detection angle of 135°. © 2006 Elsevier B.V. All rights reserved

Simultaneous depth profiling of the ¹²C and ¹³C elements in different samples using (d,p) reactions

Nuclear reactions (d,p) are often used to perform depth profiling of light elements in solids. In particular, protons coming from C-12(d,p(0)) C-13 and C-13(d,p(0)) C-14 reactions are emitted at very different energies. Consequently these two reactions can be used to depth profile C-12 and C-13 simultaneously. Nevertheless the cross-section of C-13(d,p(0)) C-14 reaction is 10 times smaller than the C-12(d,p(0)) C-13 one. So, the geometry of detection must be judiciously chosen in order to depth profile these two elements with a high sensitivity and good resolution. In the framework of this study we have performed 400 keV C-13 ions implantation into polished copper substrates at different temperatures and implanted doses with a 2 MV Tandem accelerator. Using the reactions described above, we have studied the evolution of C-13 depth profile as a function of implanted doses and temperature. We have also determined the origin of surface contamination that appears during the implantation process

Electrical properties of Bi-implanted amorphous chalcogenide films

The impact of Bi implantation on the conductivity and the thermopower of amorphous chalcogenide films is investigated. Incorporation of Bi in Ge-Sb-Te and GeTe results in enhanced conductivity. The negative Seebeck coefficient confirms onset of the electron conductivity in GeTe implanted with Bi at a dose of 2x1016 cm-2. The enhanced conductivity is accompanied by defect accumulation in the films upon implantation as is inferred by using analysis of the space-charge limited current. The results indicate that native coordination defects in lone-pair semiconductors can be deactivated by means of ion implantation, and higher conductivity of the films stems from additional electrically active defects created by implantation of bismuth.Comment: This is an extended version of the results presented in Proc. SPIE 8982, 898213 (2014

Adsorption of titanium dioxide nanoparticles onto zebrafish eggs affects colonizing microbiota

Teleost fish embryos are protected by two acellular membranes against particulate pollutants that are present in the water column. These membranes provide an effective barrier preventing particle uptake. In this study, we tested the hypothesis that the adsorption of antimicrobial titanium dioxide nanoparticles onto zebrafish eggs nevertheless harms the developing embryo by disturbing early microbial colonization. Zebrafish eggs were exposed during their first day of development to 2, 5 and 10 mg TiO2 L-1 (NM-105). Additionally, eggs were exposed to gold nanorods to assess the effectiveness of the eggs' membranes in preventing particle uptake, localizing these particles by way of two-photon microscopy. This confirmed that particles accumulate onto zebrafish eggs, without any detectable amounts of particles crossing the protective membranes. By way of particle-induced X-ray emission analysis, we inferred that the titanium dioxide particles could cover 25-45 % of the zebrafish egg surface, where the concentrations of sorbed titanium correlated positively with concentrations of potassium and correlated negatively with concentrations of silicon. A combination of imaging and culture-based microbial identification techniques revealed that the adsorbed particles exerted antimicrobial effects, but resulted in an overall increase of microbial abundance, without any change in heterotrophic microbial activity, as inferred based on carbon substrate utilization. This effect persisted upon hatching, since larvae from particle-exposed eggs still comprised higher microbial abundance than larvae that hatched from control eggs. Notably, pathogenic aeromonads tolerated the antimicrobial properties of the nanoparticles. Overall, our results show that the adsorption of suspended antimicrobial nanoparticles on aquatic eggs can have cascading effects across different life stages of oviparous animals. Our study furthermore suggests that aggregation dynamics may occur that could facilitate the dispersal of pathogenic bacteria through aquatic ecosystems