Optical absorption spectra of lead iodide nanoclusters

Abstract

Optical absorption spectra of nanoclusters of lead iodide, synthesized by the colloidal technique, have been investigated. It is shown that the absorption peaks are due to different orders of interband transitions of a nominally single size of particles rather than the first-order transitions of a number of discrete sizes of particles, as reported earlier. The model used to explain the spectra of lead iodide has also been used to account for the optical absorption peaks of colloidal mercuric iodide and bismuth tri-iodide. ͓S0163-1829͑98͒01443-X͔

Electrically Pumped White‐Light‐Emitting Diodes Based on Histidine‐Doped MoS2 Quantum Dots

“…In order to examine the effect of the lateral confinement on the optical transition energy in the pristine MoS 2 QDs due to the size‐dependent energy bandgap ( E g ), we model pristine MoS 2 QDs as a cylindrical well with infinite barrier potential. According to the effective‐mass approximation, the size dependence of the energy bandgap can be derived by the following equationwhere R is the radius of the MoS 2 QDs; E g (monolayer) is 1.80 eV, the direct bandgap of the monolayer MoS 2 ; h is the Planck constant; m e = 0.16 × m o , which is the effective mass of electron in the MoS 2 in‐plane lattice, and m o is the free‐electron mass; m h = 1.00 × m o , which is the effective mass of hole in the MoS 2 in‐plane lattice; and r nm is the n ‐th zero of the Bessel functions of order m . According to the histogram of the size distribution of the MoS 2 QDs shown in the inset of Figure a, the bandgap of the MoS 2 QDs can be obtained by Equation .…”

Synthesis of PbI2 nanoparticles by laser ablation in methanol

“…The reported results revealed particle size, shape and distribution that affecting dependence on the preparation technique [7,8]. Combined Langmuir-Blodgett and molecular deposition technique, surfactant-assisted hydrothermal method, colloidal, sol-gel, vapor deposition, reverse micelles are some methods; adopted to prepare PbI 2 nanoparticles [5,[9][10][11]. To date, synthesis of pbI 2 nanoparticles by laser ablation in liquid has not been reported.…”

Quantum confinement in PbI2 nanodisks prepared with cucurbit[7]uril

“…[21][22][23][24][25][26][27][28][29] In fact, the size affects the band-gap energy when the dimension becomes inferior to the bulk-exciton Bohr radius (ca. 1.9 nm for PbI 2 ), 21,22 although literature reveals that PbI 2 absorption edge shifts can be assigned to many other factors, from intercalation of electron-donor species between the iodide layers in few atoms clusters to ripening processes, and in low-polarity solvents. 1,25 In fact, all these phenomena are interconnected and the shift is always related to quantum confinement mechanisms.…”

“…25 Using the effective mass approximation model, it is possible to estimate the crystallite size and thickness, as did Sandroff et al 24 and others. 21,22 Thus, in such anisotropic nanomaterial, the equation governing the band-gap shifts has the form: (1) where the effective reduced masses of the electron-hole pairs in the xy plane and in the axis perpendicular to them are represented by µ xy and µ z , respectively, and L xy and L z are the dimensions of the crystallites. The reduced masses have been experimentally determined as 0.32 (µ xy ) and 1.4 (µ z ) electron mass units, according to magneto-optic experiment data.…”