Tingting Fang,Zuotao Zhang,Hui Wang,Matt Rogers,Qijia Cui
The decay and distribution of bacterial pathogens in water is an important information for the health risk assessment to guide water safety management, and suspended algae might affect bacterial pathogens in water. This study established microcosms to investigate the effects of algae-related factors on the representative indicators and opportunistic pathogen species in water. We found that suspended algae increased the persistence of targeted species by 1-2 orders of magnitude of concentrations compared to microcosms without algae; and the effect of algae on microbial survival was affected by water nutrient levels (i.e., carbon, nitrogen and phosphorus), as the increased microbial persistence were correlated to the increased algae concentrations with more nutrient supplies. Moreover, decay and distribution profiles of representative species were determined. The three opportunistic pathogen species ( Pseudomonas aeruginosa, Aeromonas hydrophila and Staphylococcus aureus ) showed lower decay rates (0.82–0.98/day, 0.76–0.98/day, 0.63–0.87/day) largely affected by algae-related factors, while the enteric species ( Escherichia coli and Enterococcus faecalis ) had higher decay rates (0.94–1.31/day, 0.89–1.21/day) with little association with algae, indicating the propensity for attachment to algae is an important parameter in microbial fate. Together results suggest suspended algae played an evident role in the decay and distribution of bacterial pathogens, providing important implications regarding microbial safety in recreational water.
Room temperature phase instability of cubic CsPbI 3 perovskite nanocrystals is one of the notorious limitations for practical applications in optoelectronic fields. Herein, the incorporation of Ni 2+ ions into CsPbI 3 lattice was successfully achieved by a modified hot-injection method using nickel acetate as doping precursor. The as-prepared Ni 2+ (3.3 mol%): CsPbI 3 nanocrystals exhibited an improved, near-unity (95%~100%) photoluminescence quantum yield owing to the enhanced radiative decay rate and the decreased non-radiative decay rate. Additionally, Ni-doping was demonstrated to stabilize CsPbI 3 lattice and the Ni 2+ : CsPbI 3 film and colloidal solution can retain their red luminescence up to 15 days and 7 months in atmosphere, respectively. First-principle calculations verified that the significantly improved optical performance and stability of Ni 2+ : CsPbI 3 nanocrystals arose primarily from the increased formation energy due to the successful doping of Ni 2+ in CsPbI 3 . Benefiting from such an effective doping strategy, the as-prepared Ni 2+ -doped CsPbI 3 perovskite nanocrystals can function well as efficient red-light emitter toward the fabrication of high-performance perovskite LED with a peak external quantum efficiency of ~7%.
Photon upconversion through lanthanide-doped nanoparticles is of great significance for various applications. However, the current development of upconversion nanoparticles is hindered by the low quantum efficiency and long radiative lifetimes of lanthanide ions, restricting their applications in time-dependent nanophotonics. Herein, we report ultrafast upconversion superfluorescence with a lifetime of sub-2.5 ns in lanthanide-doped nanoparticles at room temperature. Upon excitation with an 800-nm fs-pulsed laser, we achieve a large number ( N = 912) of correlated dipoles in Nd 3+ -concentrated nanoparticles, resulting in collective coherent emission with two orders of magnitude amplification in intensity and more than three orders of magnitude improvement in the radiative decay rate. Furthermore, we demonstrate that the control of excitation power and emitting sample length enables the lifetime manipulation of upconversion emission in a wide range from μs to sub-ns, accompanied by the typical superfluorescence signature of Burnham-Chiao ringing. These findings may benefit applications in many advanced technologies such as quantum counting and high-speed super-resolution bioimaging.
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