Nanometer-sized particles of lead iodide embedded in silica films

Abstract

Nanometer-sized particles of lead iodide layered semiconductors were embedded in Si02 films. X-ray diffraction and photoluminescence (PL) spectroscopy showed the preservation of the bulk layered structure and symmetry.The P L and PL excitation (PLE) spectroscopy exhibited a blue-shift due to quantum size effect. The bulk lead iodide showed exciton transition with an exceptionally small Bohr radius ( a g = 19 A) and a large Rydberg constant ( R = 70.8 meV). In addition, the lead iodide represents a special case in which me >> mh. The prepared samples contained particles with mean radii, a, in the range UB < a < 3 a~. In this limit (with me >> mh) the experimental results are in agreement with a model in which the electron is localized nearly at the center of the particle, enabling the hole to move around it. According to this model, the localization of the electron is further enhanced due to the confinement of the hole motion by the particle boundaries. Thus, the size confinement permits the creation of an acceptor-like exciton. The simulated blue-shift of this acceptor-like exciton has been determined, utilizing a variational method. The P L spectrum revealed additional states, associated with stoichiometric and structural defects. These defects were created during the growth process.

A review of polytypism in lead iodide

“…Crystal growth conditions are very important [18]. The great variety of ways of preparing PbI2 can be found elsewhere [19,22,39,40, and references therein].…”

Dynamics of Recombination Processes in PbI2 Nanocrystals Embedded in Porous Silica Films

“…This effect was previously investigated in detail and will not be further discussed. 7 Another interesting feature appearing in Figures 1 and 2 is the change in the fractional intensities of the various peaks. Clearly, the L band fractional intensity increases with increasing particle radius, while the G band intensity decreases.…”

“…This calculation has already been described elsewhere. 7 Therefore, the samples that have been used in this work were not investigated by TEM again, and their mean particle radii were determined according to their blue shifts.…”

One-pot Encapsulation of Pt Nanoparticles into the Mesochannels of SBA-15 and their Catalytic Dehydrogenation of Methylcyclohexane

“…Many essential synthesis methods have been developed to prepare various nanopaticles with well-controlled sizes, for example, such materials have been made in colloids [3], porous glasses [4], polymers [5], carbon nanotubes [6] and mesoporous aluminosilicates [7], etc. Among these, to use ordered mesoporous materials as hosts to limit the growth of nanostructured materials in their pores is a relatively promising scheme.…”