Effect of confinement is investigated on optical phonons of different symmetries in the nanoparticles of zinc oxide with wurtzite structure using Raman spectroscopy. An optical phonon confinement model is used for calculating the theoretical line shapes, which exhibit different asymmetric broadening and shifts, depending on the symmetries of phonon and their dispersion curves. The best fit to the data is found for particle diameters consistent with those estimated using x-ray diffraction.

Cuprous oxide quantum particles as small as 2 nm (comparable to the Bohr exciton radius) were synthesized using an electrochemical route. Quantum confinement effects are evident from a blueshift in the optical absorption. The optical absorption spectra of Cu2O nanoparticles of different sizes are discussed. Structural analysis by x-ray diffraction as well as electron diffraction shows the nanoparticles to be cubic and single phased Cu2O. X-ray photoelectron spectroscopic studies indicate the presence of CuO on the surface of Cu2O core nanoparticles.

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.

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Cesium lead halide pervoskite semiconductors are being extensively studied due to unprecedentedly high luminescence efficiency and concomitant narrow emission line width. Here, we report photophysical properties of CsPbBr 3 quantum dots having different sizes. Notably 5.5 nm sized CsPbBr 3 quantum dots reveal 95% photoluminescence (PL) quantum yield at room temperature. Moreover, signature of the stimulated emission is observed at low temperature for excitation fluence as low as ∼4.16 μW (Xe lamp excitation). Even though CsPbBr 3 quantum dots reveal the red shift in band gap at low temperature, similar to the single crystal, the exciton−phonon interaction is profoundly affected by the quantum size effects. Temperature-dependent optical studies reveal an anomalous decrease in exciton-LO phonon coupling in small-sized quantum dots aside from expected higher exciton binding energy. Observed stimulated emission in low-sized CsPbBr 3 quantum dots has implications in realizing a quantum dot based laser.