Scopus İndeksli Yayınlar Koleksiyonu / Scopus Indexed Publications Collection

CoCrMo alloys are used as orthopedic implant materials because of their excellent mechanical and corrosion properties. However, when placed in vivo, these alloys release Co, Cr, Mo ions to host tissues, which may give rise to significant health concerns over time. Nitrogen ion implantation can be used to form protective layers on the surface of CoCrMo orthopedic alloys by modifying the near surface layers of these materials. In this study, medical grade CoCrMo alloy (IS0 5832-12) was ion implanted with 60 keV nitrogen ions to a high dose of 1.9 × 10 18 ions/cm 2 at substrate temperatures of 100, 200 and 400 °C. The N implanted layer microstructures, implanted layer phases, and thicknesses were studied by a combination of Bragg-Brentano (θ/2θ) and grazing incidence (Seeman-Bohlin) X-ray diffraction (XRD and GIXRD) and cross-sectional scanning electron microscopy (SEM). Atomic force microscopy (AFM) was used for roughness analysis of N implanted as well as as-polished surfaces. Static immersion tests were performed to investigate metal ion release into simulated body fluid (SBF) by electrothermal atomic absorption spectrometry (ETAAS) and inductively coupled plasma optical emission spectrometry (ICP-OES). XRD and SEM analyses indicated that the N implanted layers were ∼ 150-450 nm thick and composed of the (Co,Cr,Mo) 2+xN nitride phase and a high N concentration Co-based FCC phase, γ N depending on the substrate temperature. ETAAS analysis results showed that in vitro exposure of the N implanted surfaces resulted in higher levels of cobalt ion release into the simulated body fluid compared to the untreated, polished alloy. The higher Co release from the N implanted specimens is attributed to the nature of the implanted layer phases as well as to the rougher surfaces associated with the N implanted specimens compared to the relatively smooth surface of the untreated material. SEM analysis of N implanted and untreated specimens after immersion tests clearly indicated calcium phosphate formation on the as-polished CoCrMo alloy, indicating a degree of bioactivity of the untreated metal surface which is absent in the N implanted specimens.

J-aggregates of 1,1′,3,3′-tetraethyl-5,5′,6,6′- tetrachlorobenzimidazolocarbocyanine (TTBC) were deposited on a mica surface and probed by atomic force microscopy operated at tapping mode in air. Optical spectra showed that J-aggregates were formed in aqueous solutions. Atomic force microscopy images revealed that J-aggregates deposited on mica surfaces mainly present single domains with a mean height of 2.00 ± 0.25 nm and an average diameter of 100 ± 20 nm. Quantitative analysis of the morphology of images indicated that the single domain of J-aggregates exhibits very uniform height and diameter distributions with polydispersity indices of 1.02 and 1.04, respectively. Based on the results, we propose a two-dimensional nanostructure in which TTBC J-aggregates could be arranged in a monolayer.

Scopus İndeksli Yayınlar Koleksiyonu / Scopus Indexed Publications Collection

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