Periodic Properties Illustrated by CH₃NH₃Pb(I_1–xBr_x)₃ Solid Solution Perovskite Semiconductors

Abstract

For solid solutions with the same arrangement of atoms, the size of a unit cell depends on the size of the atoms in the unit cell. The distance between nuclei also helps determine how strongly electrons are held, which changes the band gap energy. Samples of semiconductor CH 3 NH 3 Pb(I 1−x Br x ) 3 solid solutions were prepared; the unit cell size was measured by powder X-ray diffraction, and the band gap energy was measured by visible absorption spectroscopy. This use of a material with significant research and technological implications for solar cells illustrates the periodic properties relationship between composition, atomic size, and electron energy levels.

A Primer on Lattice Planes, Crystal Facets, and Nanoparticle Shape Control

“…Some available experiments introduce crystal structure and X-ray diffraction concepts using 2D colloidal crystals formed by relatively large silica or polystyrene spheres. − These larger-scale crystals make instruction accessible by using optical microscopy and visible laser light to replace X-ray techniques. Other experiments provide students with hands-on experience using powder X-ray diffraction to characterize solid-state and/or nanomaterials that they have synthesized. − By necessity, many of these classroom or laboratory activities refer to crystal planes, but none provide explicit instruction about how they are defined.…”

Estimating Quantum Dot Size with Pulsed Field Gradient NMR

“…15 One technique not typically applied to QDs in an undergraduate laboratory is NMR. Recent reports show that 1 H NMR of organic ligands on QDs can provide a wealth of information. 16−19 Pulsed field gradient (PFG) NMR experiments have been applied recently in undergraduate laboratories to measure diffusion of small molecules 20 and the viscosity of solution, 21 illustrating both the power of the technique and helping to fill a dearth of physical chemistry experiments in the area of mass transport.…”

“…Quantum-mechanical considerations can perturb material properties at such short length scales, allowing these properties to be “tuned” by controlling the QD size. This Journal has published syntheses and studies of a wide range of QDs, often with an emphasis on producing a range of colored QDs in a single synthesis or across a range of similar syntheses, − exploiting the effects of quantum confinement, − or serving as an introduction to nanotechnology. , A recent report focuses on the synthesis and extensive characterization of PbS QDs as the theme of an undergraduate senior research project designed to teach nanoparticle synthesis and provide insights with advanced instrumental techniques …”