Talk:Zinc oxide

Copyvio

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

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)

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.

No, ZnO does not absorb the urushiol. Calamine is a treatment for the skin eruptions caused by the allergic response to the urushiol. (The urushiol must be washed off immediately, within 5-15 minutes of exposure to the poison ivy, before it sinks into the skin and binds there. After that, only some special drugs have any chance of actually protecting you from the urushiol.)-69.87.204.36 12:49, 27 April 2007 (UTC)

Zinc Oxide is a sunscreen, commonly used in congunction with titanium oxide as they both filter out UVA and UVB light to a high degree. Commonly used in Australia with it being its own brand called Zinc Cream, primarily used on the face, unfortunately Wikipedia has no information on this topic —Preceding unsigned comment added by 59.101.156.88 (talk) 01:08, 4 February 2008 (UTC)

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.

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)

• ZnO seems to absorb, not only scatter UV, e.g.: http://www.totalblock.com/tinted.html
• ZnO2 is not used in calamine lotion

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

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)

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.

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)

The discussion on n-type character of as-grown ZnO was still wrong, so I have slightly modified this discussion. For example, the referenced paper by Janotti and van de Walle definitely does not propose that oxygen vacancies lead to n-type conductivity. Currently, there is no consensus about whether oxygen vacancies (or zinc interstitials) are responsible for the n-type character, so I added a reference to a paper that discusses all the possibilities. Also, there is a recent theoretical proposal (also by Janotti and van de Walle) that substitutional hydrogen impurities are the cause, so I added this reference too. NRLer 18:25, 26 October 2007 (UTC)

As is not the leading p-type dopant. The question is still open but many papers discuss N doping and a few use P doping. I'll post more references or make a correction when I have time, here are a couple papers using N doping: http://dx.doi.org/10.1063/1.2199588, http://dx.doi.org/10.1063/1.2166686, and using P doping: http://dx.doi.org/10.1002/adma.200502633. There are many more on N doping than either As or P, this needs a little more work —Preceding unsigned comment added by 68.6.68.153 (talk) 21:28, 29 February 2008 (UTC)

"... nitrogen is the most promising acceptor for ZnO..." http://dx.doi.org/10.1002/adma.200700083 —Preceding unsigned comment added by Mthardy (talk • contribs) 05:53, 2 March 2008 (UTC)

itch

Does Zinc oxide have anti-itch properties? If so, who discovered this, when, and what are the details of operation?-69.87.204.36 12:51, 27 April 2007 (UTC)

Taste

The fumes are dangerous (death is possible), metallic taste. But how does the ordinary solid-lotion form taste? Anything put on the skin will end up in the mouth occasionally, and it would be good to be able to recognize the taste!-69.87.199.151 17:38, 7 May 2007 (UTC)

Zinc Oxide as a surge arrester

Does anyone know more information about using Zinc Oxide rods as surge arresters for high voltage power lines? I know that the resistance drops as the voltage across it gets higher, so when it's connected between a power line and the ground power doesn't flow across it, but when a lightning strike hits the line the zinc oxide rod allows the energy to pass and then returns to normal. If anyone knows more info about this maybe you could put another heading on the zinc oxide page. Cheers Mike 121.45.173.178 07:20, 3 June 2007 (UTC)

ZnO toxicity as a nanoparticle

http://www.physorg.com/news63466994.html

This article suggests that ZnO nanoparticles appear as toxic as asbestos when tested on cell cultures (although the author of the study cautions that animal testing would be required to back this up). Is it worth writing this up, and if so should it be under a heading of Toxicity or Nanoparticles? Damburger 09:33, 6 November 2007 (UTC)

Real apps vs dreams

The big app for ZnO is in rubber with smaller uses including bactericidal ointments, dental cements, dopant for ceramics, animal feed supplements, catalyst for methanol synthesis, and electronic materials. The current article mentions these reasonably. The following do not appear to be applications:

• "ZnO layers are mainly deposited ..." this is a technique, not a use.
• "Zinc oxide nanorod sensor..." not a use (yet)
• "Spintronics" not a use (yet)
• "Piezoelectricity .. in textile fibers [reported by] the Center for Nanostructure Characterization.." Not a use (a sales-pitch)

Such cutting edge stuff still mainly in the labs might be placed in a section on "research directions." Chem Abstracts lists >60,000 entries "mentioning" zinc oxide since 2000, so we need to be a highly restrained in citing literature. --Smokefoot (talk) 03:39, 15 January 2009 (UTC)

GA Review

This review is transcluded from Talk:Zinc oxide/GA1. The edit link for this section can be used to add comments to the review.

For starters, I have reviewed an article by NIMSoffice last month and find him to be a good author who tracks down many references from many sources, and masters the subject matter. I hope this article will show the same good traits.

In the introduction, I clicked the link to II-VI semiconductor, but when I searched for III-V semiconductor for comparison, it redirected to list of semiconductor materials. Though beyond the scope of this article, I suggest for the sake of consistency that Wikipedia should not have separate articles in some cases but not others where the significance is clearly identical. Probably the simplest way to handle this is to merge the content of II-VI semiconductor into the list, and replace the formatting of the list to allow section links so that we can link from this article directly to the appropriate section.

 DoneNIMSoffice (talk) 08:09, 30 January 2009 (UTC)

I will add more comments after I read through more of the article. Crystal whacker (talk) 23:44, 20 January 2009 (UTC)

I've read up to but not including "Mechanical properties." So far, so good. Crystal whacker (talk) 00:01, 21 January 2009 (UTC)

Reference formatting

This is a problem in some articles I've reviewed. Citations to journals are formatted properly, but webpages need Template:Cite web with author and date and accessdate inserted if possible. I fixed one of these, but there are others. Crystal whacker (talk) 20:30, 23 January 2009 (UTC)

I have fixed all the first-order reference formatting issues. There are some second-order issues, such as that I prefer to use Template:Cite journal and to wikilink the journal title. I did this for the first two citations before deciding it was not worthwhile. A more pedantic reviewer may wish to finish the job. It's not critical. Crystal whacker (talk) 22:53, 25 January 2009 (UTC)

Clarify?

"Measurement of p-type in "intrinsically" n-type material is also not easy because inhomogeneity results in spurious signals." What does that mean? Crystal whacker (talk) 20:22, 25 January 2009 (UTC)

It means when some microscopic regions of a crystal are p-type and some are n-type, standard, well-established measurements can give you any result (n-type or p-type). I wouldn't claim I understand why this happens, but the fact is solid. NIMSoffice (talk) 08:09, 30 January 2009 (UTC)

Citations needed

Consider there a big "citations needed" flag over the entire "production" section except for "French process." The review article apparently does not cover production, but only mentions (for this context) the tons per year ZnO produced. Obviously you didn't invent the information out of thin air, but you probably thought one source said it when in reality it was another source. This is a "no go item" and I will place the article on hold until it's fixed. Crystal whacker (talk) 22:11, 25 January 2009 (UTC)

 DoneNIMSoffice (talk) 08:09, 30 January 2009 (UTC)

Narrowly written and unbalanced citations

The article is far better than it was one month ago, but the emphasis and especially the citations focus too much on narrow primary literature (WP:PRIMARY) and are biased towards a solid state physics. The main applications of ZnO are not explained well, and the subsections do not reflect the usage of this material in industry. The relative importance of the applications is unexplained in terms of the amounts of ZnO used for each: ZnO in cigarette filters is a significant application? The use of ZnO in pigments is unexplained and the basic role of ZnO as a rubber additive is written vaguely, lacking any chemical insights. The formation of "Na2(Zn(OH)4)" is at least glib and possibly incorrect. "ZnO improves the processing time and the resistance of concrete against water" Concrete requires water to form, so this statement is mysterious. --Smokefoot (talk) 14:23, 31 January 2009 (UTC)