Photoluminescence Spectra Of Nanocrystals Research Articles

Room-Temperature Persistent Luminescence in Metal Halide Perovskite Nanocrystals for Solar-Driven CO 2 Bioreduction

Room-Temperature Persistent Luminescence in Metal Halide Perovskite Nanocrystals for Solar-Driven CO ₂ Bioreduction

Comparative studies of optical absorption, photoluminescence and EPR spectra of PbMnI2 bulk layers and nanocrystals

We report a study of the layered diluted magnetic semiconductor (DMS) 2 x x 1 I Mn Pb  in 3D bulk layers and nanocrystal form by using optical absorption, photoluminescence and electron paramagnetic resonance (EPR). The samples of the bulk 2 x x 1 I Mn Pb  crystals with x lying within the range 0 to 0.15 were grown using the Bridgman-Stockbarger technique. The composite nanostructures containing DMS nanocrystals of 2 x x 1 I Mn Pb  were prepared by cooling the boiling saturated aqueous solution to room temperature. The exciton structure of the absorption spectra of nanoparticles exhibits blue shift due to the quantum confinement effect. In photoluminescence spectra of nanocrystals, two main peaks were revealed, which are attributed to the band-edge transitions and defect states. The EPR spectra for bulk layers and nanocrystals consist of an intense broad line and several weak narrow lines that correspond to hyperfine spectra of Mn 2+ ions.

Resonant energy transfer from silicon nanocrystals to iodine molecules

The electronic excitation energy transfer between excitons in silicon nanocrystal assemblies and iodine molecules in an organic solution is studied. From the time-resolved photoluminescence the rate of the energy transfer is found to increase with approaching a wavelength region, where the photoluminescence spectrum of nanocrystals overlaps the absorption spectrum of iodine molecules, and with increasing the radiative recombination rate of nanocrystals. The energy-transfer rate is also found to depend on the concentration of iodine molecules. This dependence is well explained by F\"orster-type dipole-dipole interaction mechanism in which the diffusion of the assemblies and molecules is taken into consideration.

Photoluminescence of Ga2S3:Eu nanocrystals

The photoluminescence (PL) of Ga2S3-5 mol % Eu2O3 nanocrystals prepared by mechanical comminution of the initial compound has been studied in the temperature range from 77 to 300 K. It is established that the PL spectrum of nanocrystals, in comparison to that of a massive sample, extends over a broader wavelength interval (430–620 nm) and has two maxima (at 507 and 556 nm) instead of one. The intensity of emission from nanocrystals is significantly higher than that from the massive crystal. The halfwidth in both cases varies with the temperature in proportion to T1/2. The intensity of emission at 556 nm for nanocrystals depends on the temperature as lgI ∼ 1/T, this dependence having three linear portions corresponding to an activation energy of 0.04, 0.16, and 0.43 eV. The PL bands with maxima at 507 and 556 nm are assigned to the intracenter 4f65d4f7 transitions in Eu2+ ions.