Advertisement

If you have an ACS member number, please enter it here so we can link this account to your membership. (optional)

ACS values your privacy. By submitting your information, you are gaining access to C&EN and subscribing to our weekly newsletter. We use the information you provide to make your reading experience better, and we will never sell your data to third party members.

ENJOY UNLIMITED ACCES TO C&EN

Materials

Polarized X-Rays Map Bonds Within Solids

Birefringence imaging reveals bond orientations without requiring perfectly ordered materials

by Jyllian Kemsley
June 2, 2014 | A version of this story appeared in Volume 92, Issue 22

[+]Enlarge
Credit: Kenneth D.M. Harris/Cardiff U
A portion of the ordered thiourea (top and bottom) and 1-bromoadamantane (middle) material examined by X-ray birefringence imaging.
Structure of 1-bromoadamantane molecules in a thiourea host.
Credit: Kenneth D.M. Harris/Cardiff U
A portion of the ordered thiourea (top and bottom) and 1-bromoadamantane (middle) material examined by X-ray birefringence imaging.

An X-ray version of a polarized light microscope provides a new way to selectively identify and map bonds within a material (Science 2014, DOI: 10.1126/science.1253537). The approach doesn’t require a perfectly ordered crystal to work and instead can help illuminate regions of a material that might differ from each other. Called X-ray birefringence imaging (XBI), the technique exploits the fact that the refractive index of a birefringent material depends on its orientation relative to the direction of linearly polarized radiation. XBI uses polarized X-rays at an energy near the edge of an absorption band of specific atoms to yield structural information about the bonding environment around those atoms, as demonstrated by a group led by Kenneth D. M. Harris of Cardiff University, in Wales. The researchers tested XBI on inclusion complex materials composed of bromine-containing guest molecules in a thiourea host, with X-rays tuned to an absorption edge of bromine to pick up the orientation of C–Br bonds. They were able to determine the orientation of 1-bromoadamantane molecules in one material. In another, they identified areas of different atomic alignment within a single crystal.

Article:

This article has been sent to the following recipient:

0 /1 FREE ARTICLES LEFT THIS MONTH Remaining
Chemistry matters. Join us to get the news you need.