Single Photon Emission from Single Perovskite Nanocrystals of Cesium Lead Bromide

The power conversion efficiency of photovoltaic devices based on semiconductor perovskites has reached ~20% after just several years of research efforts. With concomitant discoveries of other promising applications in lasers, light-emitting diodes and photodetectors, it is natural to anticipate what further excitements these exotic perovskites could bring about. Here we report on the observation of single photon emission from single CsPbBr3 perovskite nanocrystals (NCs) synthesized from a facile colloidal approach. Compared with traditional metal-chalcogenide NCs, these CsPbBr3 NCs exhibit nearly two orders of magnitude increase in their absorption cross sections at similar emission colors. Moreover, the radiative lifetime of CsPbBr3 NCs is greatly shortened at both room and cryogenic temperatures to favor an extremely fast output of single photons. The above findings have not only added a novel member to the perovskite family for the integration into current optoelectronic architectures, but also paved the way towards quantum-light applications of single perovskite NCs in various quantum information processing schemes

Role of CCR8 and Other Chemokine Pathways in the Migration of Monocyte-derived Dendritic Cells to Lymph Nodes

Studying the influence of chemokine receptors (CCRs) on monocyte fate may reveal information about which subpopulations of monocytes convert to dendritic cells (DCs) and the migration pathways that they use. First, we examined whether prominent CCRs on different monocyte subsets, CCR2 or CX3CR1, mediated migration events upstream of the accumulation of monocyte-derived DCs in lymph nodes (LNs). Monocytes were labeled and traced by uptake of latex microspheres in skin. Unexpectedly, neither CCR2 nor CX3CR1 were required. However, absence of CCR2 led to an increased labeling of the minor Gr-1int monocyte population, and the number of latex+ DCs that emigrated to LNs was correspondingly increased. Characterization of Gr-1int monocytes revealed that they selectively expressed CCR7 and CCR8 mRNA in blood. CCR7 and CCR8 pathways were used by monocyte-derived DCs during mobilization from skin to LNs. The role of CCR8 in emigration from tissues also applied to human monocyte-derived cells in a model of transendothelial trafficking. Collectively, the data suggest that Gr-1int monocytes may be most disposed to become a lymphatic-migrating DCs. When these monocyte-derived DCs exit skin to emigrate to LNs, they use not only CCR7 but also CCR8, which was not previously recognized to participate in migration to LNs

HIGH RESOLUTION LASER SPECTROSCOPY OF THE Cˉ2A1−Xˉ2A1\bar{C}^{2}A_{1} - \bar{X}^{2}A_{1} TRANSITION OF SrNH2SrNH_{2} AND Bˉ2B1−Xˉ2A1\bar{B}^{2}B_{1} - \bar{X}^{2}A_{1} TRANSITION of CaNH2CaNH_{2}

Author Institution: Center for Molecular Beams and Laser Chemistry, University of WaterlooThe high-resolution laser excitation spectrum of $\bar{C}^{2}A_{1} - \bar{X}^{2}A_{1}$ transition of $SrNH_{2}$ and $\bar{B}^{2}B_{1} - \bar{X}^{2}A_{1}$ transition of $CaNH_{2}$ were recorded. The $SrNH_{2}$ and $CaNH_{2}$ molecules were made by pulsed laser ablation of Sr and Ca metal rods follwed by reaction with $NH_{3}$- A cw dye laser was used to detect the laser induced fluorescence from a supersonic beam. The measured line positions have been fitted to give molecular constants for the electronic states

HIGH RESOLUTION SPECTROSCOPY OF SrOD RADICAL BY SUPERSONIC EXPANSION

Author Institution: University of Waterloo, Waterloo, Ontario, Canada, N2L 3GlThe high resolution spectrum of gas phase SrOD has been recorded in a supersonic beam spectrometer. The $\tilde{B}^{2}\Sigma^{+}-\tilde{X}^{2}\sigma^{+} (000)-(000)$ and (100) - (000) bands have been rotationally analyzed. The accuracy of the rotational line positions was about $0.003 cm^{-1}$, The measured line positions together with the microwave data for the ground state have been fitted to give molecular constants for both electronic states. The Q branch of the (000)-(000) band was resolved for the first time and the ratio between the perpendicular and parallcll transition dipole moments was estimated to be about 0.2