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In this work, Al2O3 ceramic coatings were prepared the surface of powder metallurgy (PM) 2024 aluminum alloy via the micro-arc oxidation (MAO) technique. The effects of the current density and the oxidation treatment time on the microstructure and properties of the MAO coatings were investigated. The results reveal that the oxide film mainly comprises the γ-Al2O3 phase, the amorphous Al2O3 phase, and a small amount of the mullite phase. There are traces of W in the coatings, which exist in the form of W, WO3, and W18O49. With increasing current density, the thickness and surface roughness of the MAO coatings prepared on the PM 2024 alloy increase, while their surface hardness first increases and then decreases. The increase in the current density promotes the transformation of the amorphous Al2O3 phase into the γ-Al2O3 phase. The maximum hardness value of 1270 HV is obtained at a current density of 20 A dm−2. The MAO coatings provide superior corrosion protection for the PM 2024 aluminum alloy, and the MAO coatings obtained at a current density of 15 A dm−2 exhibit the highest corrosion resistance. [ABSTRACT FROM AUTHOR]

Upconversion NaLuF4 nanoparticles (UCNPs) with intense visible fluorescence and good biocompatibility were successfully synthesized by the solvothermal method and subsequent surface modification, of which the upconversion emission can be tuned by Zn2+ doping. These UC fluorescent nanoprobes with oleic acid–PEG hybrid ligands can efficiently capture Rhodamine B (RhB) and sodium fluorescein (SF) in jellyfish to image their excretion in vivo and simultaneously present background-free cell morphologies and efficient luminescence resonant energy transfer (LRET) processes. The irritation of RhB and SF is assessed in jellyfish cells using NaLuF4 nanoparticles as probes and based on the combination of cell fluorescent imaging with emission spectra from LRET processes. It is clearly determined that RhB presents recoverable physical injury to the cells and SF presents unrecoverable biochemical injury to the cells. This procedure, based on surface controlled UCNPs and the LRET process, supplies background-free imaging and spectrum signals, so that the detecting limitations of conventional ultraviolet excitation are overcome and rapid optical detection of trace organic dyes becomes possible. [ABSTRACT FROM AUTHOR]