Characterization of the Antibacterial Activity of an SiO2 Nanoparticular Coating to Prevent Bacterial Contamination in Blood Products

Technological innovations and quality control processes within blood supply organizations have significantly improved blood safety for both donors and recipients. Nevertheless, the risk of transfusion-transmitted infection remains non-negligible. Applying a nanoparticular, antibacterial coating at the surface of medical devices is a promising strategy to prevent the spread of infections. In this study, we characterized the antibacterial activity of an SiO2 nanoparticular coating (i.e., the “Medical Antibacterial and Antiadhesive Coating” [MAAC]) applied on relevant polymeric materials (PM) used in the biomedical field. Electron microscopy revealed a smoother surface for the MAAC-treated PM compared to the reference, suggesting antiadhesive properties. The antibacterial activity was tested against selected Gram-positive and Gram-negative bacteria in accordance with ISO 22196. Bacterial growth was significantly reduced for the MAAC-treated PVC, plasticized PVC, polyurethane and silicone (90–99.999%) in which antibacterial activity of ≥1 log reduction was reached for all bacterial strains tested. Cytotoxicity was evaluated following ISO 10993-5 guidelines and L929 cell viability was calculated at ≥90% in the presence of MAAC. This study demonstrates that the MAAC could prevent bacterial contamination as demonstrated by the ISO 22196 tests, while further work needs to be done to improve the coating processability and effectiveness of more complex matrices.

Resolving multifrequential oscillations and nanoscale interfacet communication in single-particle catalysis

In heterogeneous catalysis research, the reactivity of the individual nanofacets of single particle is typically not resolved. We applied in situ field electron microscopy (FEM) to the apex of a curved rhodium crystal (radius of 650 nanometers), providing high spatial (~2 nanometers) and time resolution (~2 ms) of oscillatory catalytic hydrogen oxidation, imaging adsorbed species and reaction fronts on the individual facets. Using ionized water as imaging species, the active sites were directly imaged by field ion microscopy (FIM). The catalytic behavior of differently structured nanofacets and the extent of coupling between them were monitored individually. We observed limited interfacet coupling, entrainment, frequency-locking, and reconstruction-induced collapse of spatial coupling. The experimental results are backed-up by microkinetic modelling of time-dependent oxygen species coverages and oscillation frequencies.

Spontaneous and stimulated electron–photon interactions in nanoscale plasmonic near fields

The interplay between free electrons, light, and matter offers unique prospects for space, time, and energy resolved optical material characterization, structured light generation, and quantum information processing. Here, we study the nanoscale features of spontaneous and stimulated electron–photon interactions mediated by localized surface plasmon resonances at the tips of a gold nanostar using electron energy-loss spectroscopy (EELS), cathodoluminescence spectroscopy (CL), and photon-induced near-field electron microscopy (PINEM). Supported by numerical electromagnetic boundary-element method (BEM) calculations, we show that the different coupling mechanisms probed by EELS, CL, and PINEM feature the same spatial dependence on the electric field distribution of the tip modes. However, the electron–photon interaction strength is found to vary with the incident electron velocity, as determined by the spatial Fourier transform of the electric near-field component parallel to the electron trajectory. For the tightly confined plasmonic tip resonances, our calculations suggest an optimum coupling velocity at electron energies as low as a few keV. Our results are discussed in the context of more complex geometries supporting multiple modes with spatial and spectral overlap. We provide fundamental insights into spontaneous and stimulated electron-light-matter interactions with key implications for research on (quantum) coherent optical phenomena at the nanoscale.

Модификация эмиссионной поверхности науглероженного иридиевого полевого эмиттера при адсорбции атомов бария

Field electron microscopy was used to study the modification of the emission surface of a carbonized iridium field emitter when the concentration of barium atoms on the surface changes within the monolayer coating. When barium atoms are adsorbed at a temperature of T=300 K, no significant changes in the field electronic images of the emission surface are observed. The formation of barium islands on graphene in the region of the (100) iridium face at the annealing temperature T=1200 K was detected. At the annealing temperature T=1500 K, the barium island is dissolved and graphene is intercalated by barium atoms. The emission surface increases and becomes uniform in emission.

Модификация структуры градиентных покрытий Ti-Al-Si-Cu-N при механических испытаниях

The research of structural state at the indentation and scratch regions of the gradient coatings Ti-Al-Si-Cu-N was carried out with the use of dark field electron microscopy analysis method of the crystal lattice bending. It was found out that the strength properties of the substrate, which determine the degree of plastic relaxation of the applied load are significant for modifying the coating structure. The increase of the crystal lattice bending relative to undeformed state, the heterogeneity and anisotropy of its value relative to the point and axis of the load are found for the material under the indenter apex. The formation of the localized bands is shown, in which the increase of crystal sizes, decrease in the bending of the crystal lattice and residual local stresses were observed.