Facile preparation of solid-state fluorescent carbon dots with high fluorescence quantum yield and application in rapid latent fingerprints detection

Due to the direct π - π interaction and excessive energy resonance transfer, it is very challenging to prepare CDs with high fluorescence quantum yield (QY) in solid state. In...

Development of Ultrasensitive and Arsenic (III) Selective Upconverting (NaYF4: Yb3+, Er3+) Platform

The development of a sensitive alpha-NaYF4:Yb3+, Er3+ solid-phase upconverting platform (UCP) has been realized using Moringa oleifera leaf extract for selective detection of arsenic (As III) contamination in drinking water. The presence of polyphenols in the leaves extract is shown to induce luminescence resonance transfer (LRET), diminishing thereby the Er3+ upconverting red and green emissions activated by 980 nm excitation. However, addition of As3+ species interrupts the LRET process and restores emission proportionately. This feature allows platform to selectively detect arsenic pollution in water below the safe limit of 10 ppt. The uniqueness of UCP lies in monitoring the As3+ contamination in samples containing heavy ions (Cd2+, Hg2+) as well, without apparent effect on the signal reproducibility. UCP is also found to be insensitive to other interfering ions like Pb2+, H2PO4-, F-, Cl-, Ca2+, Mg2+, Sn2+, Cr6+, Fe2+ and Co2+, if present.<br><br>

Development of Ultrasensitive and Arsenic (III) Selective Upconverting (NaYF4: Yb3+, Er3+) Platform

The development of a sensitive alpha-NaYF4:Yb3+, Er3+ solid-phase upconverting platform (UCP) has been realized using Moringa oleifera leaf extract for selective detection of arsenic (As III) contamination in drinking water. The presence of polyphenols in the leaves extract is shown to induce luminescence resonance transfer (LRET), diminishing thereby the Er3+ upconverting red and green emissions activated by 980 nm excitation. However, addition of As3+ species interrupts the LRET process and restores emission proportionately. This feature allows platform to selectively detect arsenic pollution in water below the safe limit of 10 ppt. The uniqueness of UCP lies in monitoring the As3+ contamination in samples containing heavy ions (Cd2+, Hg2+) as well, without apparent effect on the signal reproducibility. UCP is also found to be insensitive to other interfering ions like Pb2+, H2PO4-, F-, Cl-, Ca2+, Mg2+, Sn2+, Cr6+, Fe2+ and Co2+, if present.<br><br>

Dark matter bars in spinning haloes

ABSTRACT We study non-linear response of spinning dark matter (DM) haloes to dynamic and secular evolution of stellar bars in the embedded galactic discs, using high-resolution numerical simulations. For a sequence of haloes with the cosmological spin parameter λ = 0–0.09, and a representative angular momentum distribution, we analyse evolution of induced DM bars amplitude and quantify parameters of the response as well as trapping of DM orbits and angular momentum transfer by the main and secondary resonances. We find that (1) maximal amplitude of DM bars depends strongly on λ, while that of the stellar bars is indifferent to λ; (2) efficiency of resonance trapping of DM orbits by the bar increases with λ, and so is the mass and the volume of DM bars; (3) contribution of resonance transfer of angular momentum to the DM halo increases with λ, and for larger spin, the DM halo ‘talks’ to itself, by moving the angular momentum to larger radii – this process is maintained by resonances; and (4) prograde and retrograde DM orbits play different roles in angular momentum transfer. The ‘active’ part of the halo extends well beyond the bar region, up to few times the bar length in equatorial plane and away from this plane. (5) We model evolution of discless DM haloes and haloes with frozen discs, and found them to be perfectly stable to any Fourier modes. Finally, further studies adopting a range of mass and specific angular momentum distributions of the DM halo will generalize the dependence of DM response on the halo spin and important implications for direct detection of DM and that of the associated stellar tracers, such as streamers.