Long-Term Plasmonic Stability of Copper Nanoparticles Produced by Gas-Phase Aggregation Method Followed by UV-Ozone Treatment

Coinage metal nanoparticles (NPs) are well-known for the phenomenon of localized surface plasmon resonance (LSPR), which is widely utilized for enhanced sensing and detection. LSPR stability over time is an important issue for the practical application of nanoparticle matrices. Some metals, and copper among those, are chemically reactive in ambient atmospheric conditions that leads to degradation of plasmonic functionality. This work reports on the formation of Cu NP matrices utilizing magnetron-sputtering gas-phase aggregation, size-selection and soft-landing on a substrate. This method provides monocrystalline NPs with high purity, thus, improving chemical inertness towards ambient gases, for example, oxygen. Additionally, a simple approach of UV-ozone treatment is shown to form an oxide shell protecting the metallic core against reactions with environmental species and stabilizing the plasmonic properties for a period of over 150 days. The suggested methodology is promising to improve the competitiveness of Cu nano-matrices with those of Au and Ag in plasmonic sensing and detection

Pulse and continuous ion beam treatment of polyethylene

Polyethylene (PE) films were treated by a nitrogen ion beam with an energy of 20 keV at a quasicontinuous regimewith low current density and at a pulse-periodical regime with high current density. IR ATR spectra and UV spectrashowed significant differences in structural changes of PE treated by pulse and continuous treatment at the sameaverage current density. The changes in the molecular structure that are induced by ion beams, i.e. the appearance ofaromatic cycles, unsaturated bonds and carbonyl groups in PE, have a similar qualitative character for all types of ionbeam regimes. However, the same degree of structural changes is achieved at lower dose in the pulse regime than in thecontinuous regime. At equal treatment parameters (ion energy, dose treatment, average current density) the pulseregime leads to a higher concentration of unsaturated and oxygen-containing groups then the continuous regime. Thiseffect at the pulse regime can be explained by the high current density in the single pulse, at which a high localtemperature is generated in the ion track field of the polymer. Probably this leads to a wave of internal stress, and theseeffects additionally stimulate structural changes in the polymer at pulsed ion beam treatment