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Pure Eu3+ ion doped BaF2 nanoparticles with tunable properties or property combinations are accessible via an ionic liquid-assisted solvothermal method. Structural parameters such as cell parameters, lattice strain, and especially morphology are judiciously tuned with calcination temperatures. For example, tensile strain is observed in samples calcined up to 400 °C; however, compressive strain appears in samples calcined at 600 °C and beyond. Larger surface area up to the sample calcined at 400 °C and observation of layer structure at higher calcinations temperature (650 °C and beyond) have been rationalized based on secondary nucleation. Three-dimensional island-like morphology with step-like layer structure caused by secondary nucleation and self-assembly are visualized and explained by scanning electron microscope analysis. Moreover, emission intensity, decay time, quantum yield, and Judd-Ofelt parameter of the Eu3+ ions increase systematically with calcination temperature to a maximum at 400 °C, above which they decrease and finally vanish at 800 °C. Our results suggest that smaller-sized nanoparticles with 3-dimensional island-like structures, generated due to secondary nucleation at higher calcinations temperature, may cause the increase of surface defects and subsequent luminescence quenching. To the best of our knowledge, the interplay between calcinations and secondary nucleation followed by drastic changes in the luminescence properties is new and previously unreported for the nanopowders. In addition, to improve the dispersibility, as-prepared nanoparticles are coated with silica and solubility of nanoparticles is measured in different solvents so that it can be useful for bioimaging applications also.

For the assessment of cardiac function, heartbeat represents one key parameter. Current methods of heartbeat measurements in the zebrafish larvae usually require larval immobilization, fluorescent transgenic strains and a confocal microscope, costly commercial software for analysis, or strong programming skills if the software is open-source. Here, we present a simple yet powerful method of heartbeat analysis using untethered, unlabeled zebrafish larva using ImageJ (open-source software), which does not require programming skills. We named it as ZebraPace for Zebrafish Precise Algorithm for Cardiac-rhythm Estimation. ZebraPace works directly with AVI videos and requires no image processing steps. ZebraPace uses pixel intensity change in a grayscale video to count the number of beats. We have validated the ZebraPace method by pharmacological alterations of the heartbeat in zebrafish larvae of 48 and 72 hpf stages. We have also determined beat-to-beat interval, which relates to rhythmicity of heartbeat. The results obtained by using ZebraPace corroborates well with the heartbeat values previously reported for similarly aged larvae as determined by using specialized software. We believe that the ZebraPace method is simple, cost-effective, and easy to grasp as it involves fewer steps. It not only reduces the manual workload but also eliminates sample preparation time and researcher subjectivity.

The nanoparticles with biomedical applications should be evaluated for its biocompatibility. Rare-earth doped nanoparticles with unique spectral properties are superior in-vivo optical probes over quantum dots and organic dyes; however,...