Talk:Zinc oxide

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Rolled back contribution from IP: suspected copyvio from http://www.navbharat.co.in/clients.htm -- Tarquin 15:17, 9 Mar 2004 (UTC)

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[edit] Whoops

I just noticed this line in the third paragraph, "...less opaque than lithopone, but more transparent than titanium dioxide." These two phrases, "less opaque" and "more transparent", seem to mean the same thing. Clearly one is wrong, but which one? GBMorris 01:08, 8 May 2006 (UTC)

[edit] topical pharmacology?

Anybody know why this is a sunscreen? A diaper rash indication? Any relation to Calamine?


\\Yes it is related to Calamine. The ZnO in Calamine is used to absorb the urushiol from the poison ivy.

[edit] Zinc oxide plaster

A friend recently told me that the pink sticking plaster one can by - the fabric version of elastoplast/band-aid - is called zinc oxide plaster. Why's it added to sticking plaster, when sticking plaster isn't normally against the wound? (At least, I wouldn't want it directly on the wound, especially at ripping-off time. Ow.)

My understanding is that zinc oxide is weakly antiseptic, hence its traditional use in sticking plasters and nappy rash creams/ointments.

As a pigment, zinc oxide is used as a sunblock, that is as a completely opaque reflective layer. The white bands that cricketers sport across their noses is a fat based paste of fairly coarse zinc oxide powder. The pigmentary effect is based on its high reflectance - not its absorbance. If it was 100% absorbant of visible light it would be black. Zinc oxide (and more commonly titanium dioxide) are also used in a micronised form where the particle size is sufficiently low with respect to UV light to be opaque (reflective) to UV, but nearly transparent to visible light. These grades are used in many modern sunscreens - the slight blue-white sheen modern sunscreen lotions sometimes give is due to the slight visibility at the blue end of the spectrum. These pigmentary sunscreens have the advantage of not degrading over time due to absorbance of UV light, unlike most organic sunscreen agents which give much reduced protection within an hour of application.

[edit] Disputed tag

There are many obviously wrong facts in this article, somebody more experienced in inorganic chemistry should check it. Cacycle 16:50, 21 August 2006 (UTC)

Can you give some examples of obviously wrong facts, maybe I am overlooking them. --Dirk Beetstra T C 16:52, 21 August 2006 (UTC)

Please check these:

  1. "... is luminescent (it will change colour from white to yellow when heated, and back again when cooled down)
  2. "and is light sensitive"
  3. "Zinc peroxide, ZnO2 .½ H2O, is a white to yellow powder used in antiseptic ointments, like Calamine Lotion."
  4. "Because it absorbs both UVA and UVB rays of ultraviolet light,"

Cacycle 17:00, 21 August 2006 (UTC)

  1. Ah .. wrong term, luminescent is probably not the right term (or another property), the experiment describes thermochromism.
  2. See point 4 ..
  3. I think it is used in some ointments, indeed, Calamine is maybe a spam ..
"Calamine" is not a brand name, but a generic term for zinc oxide with a small amount of ferric oxide mixed in, which gives it the pink color. Hence references to calamine are NOT spam. Karlhahn 20:31, 30 September 2006 (UTC)
But the reference to H2O is entirely spurious as far as I can tell. You can call ZnO2 Zinc Oxide or Zinc Peroxide, but water isn't involved. Andrew Rodland 06:44, 22 November 2006 (UTC)
  1. If it is in a sunblock, and you apply it to your body, it should block (absorb) UVA and UVB, right? But indeed, if it is then light sensitive (point 2)...
For the last two points, Sunscreen does say that zinc oxide is one of the active components. So that sounds right to me (except .. light sensitive .. hmmm). What this article def could use, are a handful of {{reference needed}} tags or maybe even an {{unreferenced}}. I would not call it disputed, but an eye of chemist in the field of solar cells may also be a good idea .. {{expert}}?

--Dirk Beetstra T C 17:14, 21 August 2006 (UTC)

From what I remember it does not absorb UV, but a very fine suspension simply reflects it. Cacycle 18:09, 21 August 2006 (UTC) Would also make sense .. most energy is in the UV, so if it absorbs UV, how would the solar-cel work. And, if it absorbs, it warms up, so the sunblock could have strange side-effects. I hope someone kicks in who knows more about this subject. --Dirk Beetstra T C 18:32, 21 August 2006 (UTC)

Cacycle 01:49, 23 August 2006 (UTC)

I believe zinc oxide is used in sunblock because it reflects the rays. It is one of the whitest substances known. Here's a link from Cornell [1] — [Mac Davis] (talk)

The luminescent (phosphorescent) compound was zinc sulfide, wasn't it, and the energy is stored in F-centers? No idea if zinc oxide does the same. As Cacycle says, zinc oxide is a wide-bandgap semiconductor, sort of like TiO_2. Can't remember what the bandgap is, but it does absorb UV. Dr Zak 02:41, 1 September 2006 (UTC)


The applications list is all over the place. My experience is with ZnO as a semiconductor material. THere should probably be an optical-electronic property related section and a chemical property related section. Anyway, ZnO has a band gap a room temperature of about 3.2, meaning that it absorbs very strongly for photons of more than 3.2 eV energy, wich is about 387 nm wavelength. I would not expect that absorbing (instead of reflecting) UV would cause a heating sensation because, 1) your skin would regularly (without sun protection) absorb the UV and 2) less than 10% of the solar radiation energy is in the UV. ZnO powder looks so white because it has a high index of refraction. It's about n=2 in the visible range, increases a bit going from blue to violet. This is just my own memory, but I checked it here: http://www.luxpop.com/cgi-bin/calc_v1.0.0.cgi Which gives 2-2.2, dependant on wavelength. ZnO has many similarities with TiO2, like bandgap and index of refraction (TiO2 about 3.5eV and n 2.4). They are stable in sunlight and do not break down. This is why they are used in sunscreen, they both start absorbing not very far into the UV range. I am not sure which one is a better protectant. Some maker of TiO2 powders started offering very fine particle sizes (50-10 nm) for sunscreen manufacturers, but because the particles are so small, they scatter very little visible light, and appear clear. I do not know if the same sort of thing is offered in ZnO powder. As a transparent electrode material ZnO is usually deposited on glass. It is used in the same way as FTO and ITO, but I think it may have poorer conductivity for the same transparency. ZnO is used as a calalyst and being researched as a photo catalyst. 131.252.124.185 23:01, 29 September 2006 (UTC) David

According to Friends of Earth there are a wide range of products containing nano-particulate TiO2 and ZnO . http://www.foe.org/camps/comm/nanotech/nanocosmetics.pdf I am not too concerned over ZnO because it has been used in comparable size particles before without harm. ZnO is not a single molecule like C60 or carbon nanotubes, it slowly disolves in water to release Zn cations, which are a nutrient in small ammounts. Zinc Oxide health effects risk assessment. ecb.jrc.it/DOCUMENTS/Existing-Chemicals/RISK_ASSESSMENT/SUMMARY/zincoxideHHsum073.pdf 131.252.124.185 23:29, 29 September 2006 (UTC)David

[edit] Additions

I have attempted to edit the article based on discussions above and my own knowledge. Comments would be helpful.

ZnO (not the peroxide) is indeed the main "active" component of Calamine lotion. Physchim62 (talk) 07:44, 1 September 2006 (UTC)

[edit] Vandalism

Look at the first topic heading. Something is up. If anyone knows what it was originally titled, please revert it to the way it was. thanks.

[edit] Dubious

There were some dubious tags in the section about doping. I found journal references for all three cases, added them in, and removed the dubious tag. If there is another reason for this, feel free to put it back, but a note on the talk page here would be helpful. LouScheffer 06:37, 6 January 2007 (UTC)

The dubious tags were related to the misleading discussion on origins of n-typeness. It is stil an open topic in oxide community, and unresolved issues were stated as facts... I was about to add a note here, but you fixed the problem before I got that far ;-) Puel 06:48, 6 January 2007 (UTC)

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