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Photoluminescence properties of Er3+/Yb3+ doped ZrO2 coatings formed by plasma electrolytic oxidation
摘要： In the present work, down- and up-conversion photoluminescence properties of Er3+/Yb3+ doped ZrO2 coatings formed by plasma electrolytic oxidation of zirconium in electrolyte containing Er2O3 and Yb2O3 particles were investigated. Down-conversion PL analysis shows that emission spectra of ZrO2:Er3+/Yb3+ coatings excited with 280 nm radiation are composed of broad PL band related to ZrO2 host and bands assigned to f-f transitions of Er3+. The main PL emission bands of Er3+ at around 548 nm and 560 nm are related to 4S3/2→4I15/2 transition. PL excitation spectra monitored at 548 nm feature broad band in the region from 250 nm to 350 nm which is associated with the electron transfer transition from 2p orbital of O2? to 4f orbital of Er3+ and transitions of ZrO2. On the other hand, bands in PL excitation spectra ranging from 350 nm to 535 nm are related to 4f transitions of the Er3+ from the ground state 4I15/2 to higher energy levels. Down-conversion PL intensity decreases with increasing concentration of Yb3+ in coating due to energy transfer from Er3+ to Yb3+. ZrO2:Er3+/Yb3+ coatings show intense green (4S3/2→4I15/2) and red (4F9/2→4I15/2) up-conversion PL emission under the excitation with a 980 nm diode laser. With increasing Yb3+ concentration red up-conversion PL intensity increases more rapidly with respect to green emission, because red up-conversion PL intensity strongly depends on Yb3+ concentration, i.e. 4F9/2 state of Er3+ is directly excited by energy transfer from excited Yb3+.
关键词： up-conversion,Photoluminescence,Er3+/Yb3+,Down-conversion,Plasma electrolytic oxidation
更新于2025-09-23 15:23:52
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Biofunctionalization of selective laser melted porous titanium using silver and zinc nanoparticles to prevent infections by antibiotic-resistant bacteria
摘要： Antibiotic-resistant bacteria are frequently involved in implant-associated infections (IAIs), making the treatment of these infections even more challenging. Therefore, multifunctional implant surfaces that simultaneously possess antibacterial activity and induce osseointegration are highly desired in order to prevent IAIs. The incorporation of multiple inorganic antibacterial agents onto the implant surface may aid in generating synergistic antibacterial behavior against a wide microbial spectrum while reducing the occurrence of bacterial resistance. In this study, porous titanium implants synthesized by selective laser melting (SLM) were biofunctionalized with plasma electrolytic oxidation (PEO) using electrolytes based on Ca/P species as well as silver and zinc nanoparticles in ratios from 0 to 100% that were tightly embedded into the growing titanium oxide layer. After the surface bio-functionalization process, silver and zinc ions were released from the implant surfaces for at least 28 days resulting in antibacterial leaching activity against methicillin-resistant Staphylococcus aureus (MRSA). Furthermore, the biofunctionalized implants generated reactive oxygen species, thereby contributing to antibacterial contact-killing. While implant surfaces containing up to 75% silver and 25% zinc nanoparticles fully eradicated both adherent and planktonic bacteria in vitro as well as in an ex vivo experiment performed using murine femora, solely zinc-bearing surfaces did not. The minimum inhibitory and bactericidal concentrations determined for different combinations of both types of ions confirmed the presence of a strong synergistic antibacterial behavior, which could be exploited to reduce the amount of required silver ions by two orders of magnitude (i.e., 120 folds). At the same time, the zinc bearing surfaces enhanced the metabolic activity of pre-osteoblasts after 3, 7, and 11 days. Altogether, implant biofunctionalization by PEO with silver and zinc nanoparticles is a fruitful strategy for the synthesis of multifunctional surfaces on orthopedic implants and the prevention of IAIs caused by antibiotic-resistant bacteria.
关键词： Multifunctional biomaterials,silver and zinc nanoparticles,implant-associated infections,plasma electrolytic oxidation,additive manufacturing,MRSA
更新于2025-09-16 10:30:52