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Iodine vapor staining for atomic number contrast in backscattered electron and X-ray imaging

Boyde, A; McCorkell, F A; Taylor, G K; Bomphrey, R J; Doube, M


A Boyde

F A McCorkell

G K Taylor

R J Bomphrey

M Doube


Iodine imparts strong contrast to objects imaged with electrons and X‐rays due to its high atomic number (53), and is widely used in liquid form as a microscopic stain and clinical contrast agent. We have developed a simple technique which exploits elemental iodine's sublimation‐deposition state‐change equilibrium to vapor stain specimens with iodine gas. Specimens are enclosed in a gas‐tight container along with a small mass of solid I2. The bottle is left at ambient laboratory conditions while staining proceeds until empirically determined completion (typically days to weeks). We demonstrate the utility of iodine vapor staining by applying it to resin‐embedded tissue blocks and whole locusts and imaging them with backscattered electron scanning electron microscopy (BSE SEM) or X‐ray microtomography (XMT). Contrast is comparable to that achieved with liquid staining but without the consequent tissue shrinkage, stain pooling, or uneven coverage artefacts associated with immersing the specimen in iodine solutions. Unmineralized tissue histology can be read in BSE SEM images with good discrimination between tissue components. Organs within the locust head are readily distinguished in XMT images with particularly useful contrast in the chitin exoskeleton, muscle and nerves. Here, we have used iodine vapor staining for two imaging modalities in frequent use in our laboratories and on the specimen types with which we work. It is likely to be equally convenient for a wide range of specimens, and for other modalities which generate contrast from electron‐ and photon‐sample interactions, such as transmission electron microscopy and light microscopy.


Boyde, A., McCorkell, F. A., Taylor, G. K., Bomphrey, R. J., & Doube, M. (2014). Iodine vapor staining for atomic number contrast in backscattered electron and X-ray imaging. Microscopy Research and Technique, 77(12), 1044-1051.

Journal Article Type Article
Acceptance Date Aug 26, 2014
Publication Date Nov 24, 2014
Deposit Date Nov 11, 2014
Publicly Available Date Feb 13, 2019
Journal Microscopy Research and Technique
Print ISSN 1059-910X
Publisher Wiley
Peer Reviewed Peer Reviewed
Volume 77
Issue 12
Pages 1044-1051
Public URL
Additional Information Corporate Creators : Barts, Oxford


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