Tenebrescence to measure exposure to ultraviolet radiation

We know positively that the excess of ultraviolet radiation causes cancer and eye diseases. Nothing, then, more rational than using some type of device to measure how much radiation and what type we expose at a given time. The fact that it is rational does not mean, obviously, that people do it. The rudest control, from the time that is exposed to the sun and the time of day, is something that many fans to be outdoors forget.

All in all, an ultraviolet radiation detector is very useful. In fact, today it is commonly used in photochromic glasses, those that change color by giving them ultraviolet radiation. The problem is that this effect is achieved by the presence of organic molecules, which change their chemical configuration when exposed to radiation; These changes end up accumulating failures that, after a few years, stop working properly.

Tenebrescence in a hakmenite cabochon of gemological quality. Source

Sodalite is a navy blue tectosilicate used in jewelry. A variant of the sodalite is the Hakmanite which, depending on the variety, has photochromism or the opposite property, the so-called tenebrescence, that is, it has a color in the absence of ultraviolet radiation, which disappears if it receives radiation.

A team of researchers headed by Isabella Norrbo, from the University of Turku (Finland), has developed a synthetic Hakmanite that changes color depending on the amount of ultraviolet radiation it receives. The material can be adjusted to respond to different levels of UVA, UVB or UVC radiation, as well as to the UV index of the Sun.

As the color change of the Hakmenite is not due to a change in the chemical composition but to the electronic configuration, the durability is much greater than in the organic alternatives. For this reason the color change is reversible. The nature of the components (silicates) makes the sensor also very cheap to manufacture.

The color intensity of the material correlates with the radiation dose. The detector could be used as a sticker that can be placed on a shirt, a cap or a watch. It would be enough to use an app to measure the status just before going outside taking a photo and the same app will tell us the level of exposure at any later time by making a new photo.

The utility and the health benefits are undoubted. That does not mean that they are the same ones who do not drink before driving or who do not smoke the ones that are most useful to them.

Reference:

I. Norrbo et al (2018) Solar UV index and UV dose determination with photochromic hackmanites: from the assessment of the fundamental properties to the device Materials Horizons doi: 10.1039/C8MH00308D