Stable green-emitting perovskite nanocrystals (NCs) with general formula APbBr 3 , exhibiting a high photoluminescence quantum yield (PLQY), narrow bandwidth, and adjustable PL in the 510−535 nm region are coveted materials for optoelectronic applications. A generic method of obtaining both hybrid and all-inorganic perovskite NCs with the desired characteristics is, however, lacking. Herein, we report a methodology for the synthesis of CsPbBr 3 , FAPbBr 3 , and MAPbBr 3 NCs employing N-bromosuccinimide as the bromide precursor. The NCs show uniform size distribution, PL maxima between 512 and 531 nm, near-unity PLQY with a fwhm of 18−22 nm, and remarkable stability in ambient conditions, in the presence of water and under UV irradiation. Not only do these exceptional characteristics of the NCs indicate their high potential in real applications, but this new methodology may also open new vistas for direct synthesis of other perovskites with high PLQY and stability without resorting to any additional postsynthesis treatment.

Studies on ultrafast dynamics of various photo-induced processes in perovskite nanocrystals and their composites, and insights obtained from them are presented in this review.

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a Ph.D. student under Prof. Anunay Samanta. His research interest is the synthesis and understanding of ultrafast photoinduced processes of highly luminescent perovskite nanocrystals.Sumanta Paul, after completing his Master's degree from the School of Chemistry, University of Hyderabad, in 2017, is working on his Ph.D. under the supervision of Prof. Anunay Samanta. His research focuses on the synthesis and study of photophysical properties of perovskite nanocrystals at the bulk and single-particle levels.

Despite their low band gap, the utility of CsPbI 3 nanocrystals (NCs) in solar photovoltaic and optoelectronic applications is rather limited because of their phase instability and photoluminescence (PL) intermittency. Herein we show that phase-pure, monodispersed, stable and highly luminescent CsPbI 3 NCs can be obtained by tweaking the conventional hot-injection method employing NH 4 I as an additional precursor. Single-particle studies show a significant suppression of PL blinking. Among all NCs studied, 60% exhibit only high-intensity ON states with a narrow distribution of intensity. The remaining 40% of NCs exhibit a much wider distribution of PL intensity with a significant contribution of low-intensity OFF states. Excellent characteristics of these CsPbI 3 NCs are shown to be the result of NH 4 + replacing some surface Cs + of an iodide-rich surface of the NCs. These phase-stable and highly luminescent CsPbI 3 NCs with significantly suppressed PL blinking can be useful single-photon emitters and promising materials for optoelectronic and solar photovoltaic applications.

The mechanism of thermal and chemical unfolding of Coccinia indica agglutinin (CIA17), a chitooligosacharide-specific phloem exudate lectin, was investigated by biophysical approaches. DSC studies revealed that the unfolding thermogram of CIA17 consists of three components (T m ∼ 98, 106, and 109 °C), which could be attributed to the dissociation of protein oligomers into constituent dimers, dissociation of the dimers into monomers, and unfolding of the monomers. Intrinsic fluorescence studies on the chemical denaturation by guanidinium thiocyanate and guanidinium chloride indicated the presence of two distinct steps in the unfolding pathway, which could be assigned to dissociation of the dimeric protein into monomers and unfolding of the monomers. Results of fluorescence correlation spectroscopic studies could be interpreted in terms of the following model: CIA17 forms oligomeric structures in a concentration dependent manner, with the protein existing as a monomer below 1 nM concentration but associating to form dimers at higher concentrations (K D ≈ 2.9 nM). The dimers associate to yield tetramers with a K D of ∼50 μM, which further associate to form higher oligomers with further increase in concentration. These results are consistent with the proposed role of CIA17 as a key player in the defense response of the plant against microbes and insects.

33) Cabane, B.; Wong, K.; Wang, T. K.; Lafuma, F.; Duplessix, R. Colloid Polvm. Sci. 1988. 266. 101. (34) Afshar-Rad, T.; Bailey, A. I.; Luckham, P. F.; Macnaughtan, W.; (35) Marra, J.; Hair, M. L. J. Phys.On the basis of percolation results of 32 water/oil microemulsion systems, a detailed analysis of the validity of the effective medium theory (EMT), EMT with dipoledipole interaction (EMTDD), and Bemasconi-Weismann (BW) theory has been made. It has been found that most of the systems obey either the EMT or the EMTDD (chain) formalism whereas a slender few follow the EMTDD (cluster) and BW formalisms. The results suggest that the internal structure of microemulsions can be either isolated, randomly dispersed spheres or spheroidal aggregates formed by dipolar interaction.

Highly luminescent cesium lead halide (CsPbX 3 , X = Cl, Br, I) perovskite nanocrystals (NCs) are promising materials for a number of optoelectronic applications like LEDs and other display technologies. However, low photoluminescence (PL) quantum yield (QY) of the large-bandgap violet-and blue-emitting CsPbCl 3 and CsPb(Cl/Br) 3 NCs is an obstacle to the development of blue-and white-emitting LEDs. In this work, we show that these NCs with high PLQY can be obtained directly by employing an appropriate halide precursor and by optimizing the Pb:X precursor ratio. Specifically, employing N-chloro-and Nbromophthalimides as halide precursors and varying the Pb:X precursor ratio, we have obtained stable and highly luminescent (PLQY 80−99%) perovskite NCs emitting in the blue-violet region extending to green by direct synthesis. Time-resolved PL and ultrafast pump−probe studies of these systems reveal the effect of Pb:X precursor ratio on the carrier recombination processes. Rapid carrier trapping is found to be the dominant process that impairs the PLQY of the NCs obtained by using a stoichiometric (1:3) Pb:X precursor ratio. This trapping of carriers is effectively alleviated by using an excess amount of the halide precursor during the preparation of the NCs. The results brighten the potential utility of these high-quality perovskite NCs emitting in the blue-violet region in optical applications.