Zinc Oxide: Thermochromic Color Change

Zinc oxide is an inorganic compound with the formula ZnO. It’s a white powder that is insoluble in water, and it is widely used as an additive in numerous materials and products including rubbers, plastics, ceramics, glass, cement, lubricants, paints, ointments, adhesives, sealants, pigments,foods, batteries, ferrites, fire retardants, and first-aid tapes. It occurs naturally as the mineral zincite, but most zinc oxide is produced synthetically.

ZnO is a wide-bandgap semiconductor of the II-VI semiconductor group. The native doping of the semiconductor due to oxygen vacancies or zinc interstitials is n-type. This semiconductor has several favorable properties, including good transparency, high electron mobility, wide bandgap, and strong room-temperature luminescence. Those properties are used in emerging applications for transparent electrodes in liquid crystal displays, in energy-saving or heat-protecting windows, and in electronics as thin-film transistors and light-emitting diodes.

Crystalline zinc oxide is Thermochromic, changing from white to yellow when heated and in air reverting to white on cooling. This color change is caused by a small loss of oxygen to the environment at high temperatures to form the non-stoichiometric Zn1+xO, where at 800 °C, x = 0.00007.

Giffed from: this video
More Science and Gifs on: rudescience 


Fluorescence thermochromism of pyridine-copper-iodide complex. At room temperature it has a yellow emission, but when it is cooled with liquid nitrogen to low temperatures (-195 °C) the fluorescent color changes to blue/purple. When the ampule is removed from the nitrogen and warms up, the color changes back.

On the gifs I placed an ampule in a transparent Dewar flask with some liquid nitrogen inside it. Between the walls of the glass there is vacuum what acts as a thermal insulator and prevents the liquid nitrogen from fast evaporation. 

echoing-night  asked:

This is an odd question,but, would you consider Moodstone an actual gem?

In general, I would not, but the stone can be made of Quartz or Glass. Perhaps on Homeworld these ‘mood stones’ are experiments with Quartzs to enhance their abilities.
“A mood ring is a ring that contains a thermochromic element, such as liquid crystal, that changes colors based upon the temperature of the finger of the wearer… The mood ring was created in 1975 by two New York inventors, Josh Reynolds and Maris Ambats, who bonded liquid crystals with quartz stones set into rings… The ring is typically ornamented with a faux gemstone (usually made of quartz or glass) which is either a clear capsule filled with thermochromic liquid crystal, or has a thin sheet of liquid crystal sealed underneath.”


Thermochromic Color Changing Paint

New stamp celebrates upcoming solar eclipse with heat-reactive transformation
On Monday, August 21st, the continental US will experience its first total solar eclipse since 1979. The stamp is printed using thermochromic ink, and when rubbed using fingers or thumbs it will react to body heat, changing from an image of a total solar eclipse to a picture of the Moon. If you’ve forgotten your high school science lessons, a total solar eclipse happens when the Moon moves between the Sun and the Earth, blocking out the former’s light. Read more

This week something adorable will be posted: fluorescence thermochromism!

During the last few weeks I have prepared ~25 new, not yet described compound that have a weak or strong fluorescence thermochromism. This means they emit an other color under UV lamp at a different temperatures. Most of these compounds work at -195 °C where liquid nitrogen boils, but some of them show some effect at -100 to -70 °C. 

How do these work? Depending on the temperature the bonds in these molecules change a lot what means they can absorb and emit different wavelength. As seen on the pictures, on the first there are the compounds, each ampule contains 100 mg. When irradiated with UV light at room temperature (second pics) few of them emit some visible light, but when they are cooled down with liquid nitrogen (last pics) most of the compounds emit a different wavelength light with a different intensity. 


There are several compounds, that has a near no emission under UV light at room temperature, but when it’s cooled down with liquid nitrogen, the emission increases a lot. This phenomena is called low temperature fluorescence thermochromism.

In this case I prepared an organic compound what is a white crystalline solid at room temperature, but when it is cooled below -100 °C it emits a bright blue light when exposed to UV light.

While being irradiated with UV light, as temperature drops in the flask and the crystals reach a specific temperature, they start to emit light. It’s a quite adorable thing, since you can actually see the temperature.

How does it work? Depending on the temperature the bonds in these molecules change a lot what means they can absorb and emit different wavelength. When irradiated with UV light at room temperature, the compound emits some visible light, but when it is  cooled down with liquid nitrogen the compound emits a different wavelength light with a different intensity. 


Here is another thermofluorescent compound what I prepared recently. It’s interesting to see that at room temperature it is an off-white powder without visible fluorescence, but when it is cooled down with liquid nitrogen under UV light it first emits a bright green (1.-st gif), than a bright blue color (2.-nd gif). 

According to measurements the green fluorescence of this compound develops at -50 °C and the blue color is emitted under -140 °C. 

Science is simply adorable. 

Yesterday I posted about fluorescence thermochromism, but “normal’ thermochromism is just as interesting as the fluorescent one. 

On the gif above there is two ampule what contain silver and copper tetraiodomercurate, a complex of mercury iodide. The copper tetraiodomercurate  (left side) is bright red at room temperature, but when it is heated e.g.: in hot water, above 67 °C it turns black. On the right side there is silver tetratiodomercurate (Ag2HgI4) what is yellow at room temperature, but when it’s heated above 50 °C, it turns orange. Since the color change is reversible, when it is cooled back to room temperature, the color also changes back.



A brand new thermofluorescent compound what emits a much brighter color when cooled down to circa -100 °C. On the first pics there is a filter paper with compound A in an α and in a ß crystal form. The α form emits a yellow and the ß emith a green color. Same compound, with a similar crystal form. When it’s cooled down with a small amount of liquid nitrogen (seen on the gifs) the intensity of the emitted light increases +100 fold compared to the room temperature emission with a quite similar wavelenght. On the last picture the cooled filter papers are seen when cooled down to -100 °C.



Something really interesting: Fluorescence thermochromism of copper(I)-iodide–pyridine complex.

Pyridine with copper(I)-iodide forms an off-white complex what is highly fluorescent. The off white powder glows yellow under UV light at room temperature, but when it is cooled with liquid nitrogen the color of emission changes from yellow to orange, then to pink and at the end it glows with an intense blue/purple color when the complex reaches -195.79 °C.

The complex has a tetrahedral tetrameric structure with a Cu4Icube in it’s middle and 4 pyridine ring surrounds this little cage.