Clusters in solution: Growth and optical properties of layered semiconductors with hexagonal and honeycombed structures

Abstract

Transmission electron microscopy and optical absorption were used to examine small clusters of the layered semiconductors, PbI2 and BiI3. In both systems, a layer of metal is sandwiched between two hexagonally closed-packed layers of iodine. We describe a simple solution preparation which gives rise to clusters corresponding to single layer sandwiches, roughly 7 Å thick, whose lateral dimensions vary from 12 to 90 Å depending on the solvent and the nature of the growing cluster interface. The cluster size distributions are markedly different for PbI2 and BiI3 reflecting the different structure in the metal planes of these systems. PbI2 cluster sizes are determined by hexagonal symmetry, with cluster growth achieved by placement of lead atoms symmetrically about a smaller cluster. In BiI3, whose metal plane has a honeycombed structure like graphite, clusters grow to be much larger with their sizes determined by the closure of six-membered rings. The optical absorption spectra of PbI2 and BiI3 can be quantitatively understood in terms of the measured cluster size distributions.

A review of polytypism in lead iodide

“…PbI2 is used to study cluster formation [1,2] and to study thin films of various molecules that can be placed between the layers (intercalation) [3][4][5]. It is a candidate for use in image recording [6].…”

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

“…1,25 In fact, all these phenomena are interconnected and the shift is always related to quantum confinement mechanisms. Normally, low-polarity solvents tend to stabilize larger colloidal particles in detriment of the smaller ones as shown by Sandroff et al, 24 but also change the dielectric constant of the medium. Small molecules can be easily intercalated into PbI 2 , once the layers are weakly held together, essentially by van der Waals interactions.…”

“…8, 2011 semi-conducting materials lead to quantum confinement of excitons in one, two or three dimensions, depending on the shape and size of the particles. [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.…”

Correction: A review of polytypism in lead iodide

“…As a reference, the I-I distance in gaseous I 2 is 0.27 nm [36]. 4 The 2H, 4H, 6H, and 6R polytypes of PbI 2 We choose four polytypes of PbI 2 as examples of the differences between polytypes. Table 1 goes up to 30H and 36R.…”

“…The references in this review are not meant to be exhaustive but contain enough recent studies to allow the reader to follow any research paper trail. PbI 2 is used to study cluster formation [1,2] and to study thin films of various molecules that can be placed between the layers (intercalation) [3][4][5]. It is a candidate for use in image recording [6].…”