Strong quantum confinement in Mn-doped semiconductor nanocrystals enhances dopant–carrier exchange interactions. Here, we report the synthesis and optical properties of strongly quantum confined, quasi two-dimensional, Mn-doped CsPbCl3 nanoplatelets. A room-temperature synthesis was employed to prepare the platelets with thickness 2.2 nm (4 monolayers), which is significantly smaller than the Bohr excitonic diameter of CsPbCl3 (5 nm). Efficient transfer of excitonic energy from the host to the Mn2+ dopant ions leads to a spin-forbidden 4T1–6A1 Mn d-electron emission with the highest quantum yield of ∼20% and exhibits a long lifetime of 1.6 ms. Subsequent anion exchange reactions at room temperature lead to the formation of Mn-doped CsPbBr3 nanoplatelets, with weak Mn emission. These newly developed Mn-doped cesium lead halide nanoplatelets are suitable candidates for exploring the effects of quantum confinement on dopant–carrier exchange interaction and exhibiting interesting magneto-optic properties.

Lead bromide (PbBr 2 ,99.999%), lead iodide (PbI 2 , 99.999%), lead chloride (PbCl 2 , 98%), manganese (II) bromide (MnBr 2 , 98%), ytterbium (III) nitrate pentahydrate {Yb(NO 3) 3 .5H 2 O, 99.99%}, caesium carbonate (Cs 2 CO 3 , 99.9%), oleic acid (OA, 90%), 1-octadecene (ODE, 90%), oleylamine (OLA, 98%), trioctylphosphine (TOP, 90%), methyl acetate (MeOAc, 99.5%), N,N-dimethylformamide (DMF, 99.8%), hydrogen bromide (HBr, 43 wt%, 99.99%) were purchased from Aldrich and were used without further purification. Acetone (99.0%, SDFCL), Hexane (99.99%, Rankem), Toluene (99.5%, Rankem) solvents are used as obtained.

Charge-storage mechanism of free-standing MoS 2 /r-GO (r-GO = reduced graphene oxide) hybrid nanoflakes on molybdenum (Mo) foil in Na 2 SO 4 solution is elucidated for realizing a high-performance asymmetric supercapacitor (ASC). Thiourea that acts primarily as sulfur source also helps intercalating ammonium ions, which along with r-GO facilitate in situ exfoliation of MoS 2 , producing hierarchical MoS 2 with expanded interlayer spacing. This interlayer expansion in MoS 2 facilitates Na + -ions intercalation/deintercalation and ensures enhanced capacitance, rate capability, and cycling stability of the capacitor . Besides exhibiting attractive energy-cum-power traits, the 2 V MoS 2 /r-GO//Fe 2 O 3 /MnO 2 ASC shows compelling cycling performance for over 20 000 cycles in an aqueous electrolyte.

Bulk Cs 3 Bi 2 I 9 exhibits zero-dimensional (0-D) perovskite crystal structure at the molecular level, providing scopes for novel optical properties compared to three-dimensional perovskite structures. Here, 0-D refers to the crystal structure irrespective of the size of the crystal. We have prepared colloidal Cs 3 Bi 2 I 9 nanocrystals and elucidated the unique optical properties arising from their 0-D crystal structure. Absorption spectrum at 10 K confirms that the electronic band gap of Cs 3 Bi 2 I 9 nanocrystals is at 2.86 eV, along with a sharp excitonic peak at 2.56 eV, resulting in a very high excitonic binding energy, E b X = 300 meV. Interestingly, we observe two peaks in the photoluminescence spectra at room temperature on both sides of the excitonic absorption energy. Because E b X (300 meV) ≫ effective phonon energy (36 meV), the phonon-mediated relaxation of carriers from conduction band minimum to the excitonic state is suppressed to an extent. Consequently, two photoluminescence peaks related to both the bulk band edge and the excitonic transitions are observed. Furthermore, Rb 3 Bi 2 I 9 nanocrystals have also been synthesized, but they exhibit two-dimensional layered structure, unlike the 0-D structure of Cs 3 Bi 2 I 9 .

Herein we report the colloidal synthesis of Cs 3 Sb 2 I 9 and Rb 3 Sb 2 I 9 perovskite nanocrystals,a nd explore their potential for optoelectronic applications.D ifferent morphologies,s uch as nanoplatelets and nanorods of Cs 3 Sb 2 I 9 ,a nd spherical Rb 3 Sb 2 I 9 nanocrystals were prepared. All these samples show band-edge emissions in the yellow-red region. Exciton many-body interactions studied by femtosecond transient absorption spectroscopyofCs 3 Sb 2 I 9 nanorods reveals characteristic second-derivative-type spectral features,suggesting red-shifted excitons by as much as 79 meV.Ah igh absorption cross-section of ca. 10 À15 cm 2 was estimated. The results suggest that colloidal Cs 3 Sb 2 I 9 and Rb 3 Sb 2 I 9 nanocrystals are potential candidates for optical and optoelectronic applications in the visible region, though ab etter control of defect chemistry is required for efficient applications. Figure 1. a) Schematic representation of the relationship among the perovskitec rystal structures of i) 3D CsMI 3 (M = Pb 2+ /Sn 2+ ), ii)2D Cs 3 Sb 2 I 9 ,and iii)0DCs 2 SnI 6 .b)Schematic representation of the synthesis of Cs 3 Sb 2 I 9 NPLs and Cs 3 Sb 2 I 9 NRs. ODE = 1-octadecene, OnA = octanoic acid, OAm = oleylamine.[*] J. Pal, S. Manna, [+] A. Nag