Editing Titanium dioxide (section)

==Applications==

===Pigment===
{{Main|Titanium white}}

First mass-produced in 1916,<ref>{{cite book|title=The Secret Lives of Colour|last=St. Clair|first=Kassia|publisher=John Murray|year=2016|isbn=978-1-4736-3081-9|location=London|page=40|oclc=936144129}}</ref> titanium dioxide is the most widely used white pigment because of its brightness and very high [[refractive index]], in which it is surpassed only by a few other materials (see ''[[list of indices of refraction]]''). Titanium dioxide crystal size is ideally around 220&nbsp;nm (measured by electron microscope) to optimize the maximum reflection of visible light. However, [[abnormal grain growth]] is often observed in titanium dioxide, particularly in its rutile phase.<ref name="ref1">{{cite journal| last1=Hanaor| first1=D. A. H. | last2=Xu| first2=W.|last3=Ferry|first3=M.|last4=Sorrell|first4=C. C. | title= Abnormal grain growth of rutile TiO<sub>2</sub> induced by ZrSiO<sub>4</sub>| journal= [[Journal of Crystal Growth]]| year= 2012| volume=359| pages=83–91| url= https://hal.archives-ouvertes.fr/hal-02315198/document/#page=2 | doi=10.1016/j.jcrysgro.2012.08.015|arxiv=1303.2761| bibcode=2012JCrGr.359...83H | s2cid=94096447 }}
</ref> The occurrence of abnormal grain growth brings about a deviation of a small number of crystallites from the mean crystal size and modifies the physical behaviour of TiO<sub>2</sub>. The optical properties of the finished pigment are highly sensitive to purity. As little as a few parts per million (ppm) of certain metals (Cr, V, Cu, Fe, Nb) can disturb the crystal lattice so much that the effect can be detected in quality control.<ref>{{Cite book |title=Kemira pigments quality titanium dioxide |last=Anderson |first=Bruce |year=1999 |location=Savannah, Georgia |pages=39}}</ref>{{Full citation needed|date=January 2025}} Approximately 4.6 million tons of pigmentary TiO<sub>2</sub> are used annually worldwide, and this number is expected to increase as use continues to rise.<ref name="Nano-scaled titania">{{cite book |last=Winkler |first=Jochen |title=Titanium Dioxide |year=2003 |isbn=978-3-87870-148-4 |pages=5 |publisher=Vincentz Network |location=Hannover, Germany}}</ref>

TiO<sub>2</sub> is also an effective [[opacifier]] in powder form, where it is employed as a pigment to provide whiteness and [[Opacity (optics)|opacity]] to products such as paints, coatings, plastics, papers, inks, foods, [[Dietary supplement|supplements]], medicines (i.e. pills and tablets), and most toothpastes; in 2019 it was present in two-thirds of toothpastes on the French market.<ref name=frouville>{{cite news |title=Deux dentifrices sur trois contiennent du dioxyde de titane, un colorant au possible effet cancérogène|language=fr|trans-title=Two out of three toothpastes contain titanium dioxide, a possibly carcinogenic colouring material|author=Margaux de Frouville|url=https://www.bfmtv.com/sante/deux-dentifrices-sur-trois-contiennent-du-dioxyde-de-titane-un-colorant-au-possible-effet-cancerogene-1660942.html |publisher=BFMTV.com |date=28 March 2019}}</ref> In paint, it is often referred to offhandedly as "brilliant white", "the perfect white", "the whitest white", or other similar terms. Opacity is improved by optimal sizing of the titanium dioxide particles.

===Additive for food===
Often used as color in food,<ref>{{cite book |author=<!--not stated-->|date=June 2022 |title=State of the Science of Titanium Dioxide (TiO₂) as a Food Additive |url=https://publications.gc.ca/collections/collection_2022/sc-hc/H164-341-2022-eng.pdf |publisher=Food Directorate, Health Canada |url-status=live |archive-url=https://web.archive.org/web/20240530235509/https://publications.gc.ca/site/archivee-archived.html?url=https://publications.gc.ca/collections/collection_2022/sc-hc/H164-341-2022-eng.pdf |isbn=978-0-660-44121-4 |archive-date=30 May 2024}}</ref> it is commonly found in ice creams, chocolates, all types of candy, creamers, desserts, marshmallows, chewing gum, pastries, spreads, dressings, cakes, some cheeses, and many other foods.<ref>{{cite web|url=https://healthknight.com/titanium-dioxide-e171-side-effects-benefits |title=Titanium Dioxide (E171) – Overview, Uses, Side Effects & More |date=10 April 2022 |publisher=HealthKnight |access-date=2022-06-09}}</ref> It is permitted in many countries, but was banned for use in food by the European Union in 2022. While permitted in the United States, [[Mars Inc.|Mars]] removed it from their [[Skittles (confectionery)|Skittles]] confectionery in 2025, although a class-action lawsuit against the use of titanium dioxide in Skittles had been dismissed in 2022.<ref>{{cite news| last=Sherman | first=Natalie | title=Skittles-maker Mars phases out controversial colour additive | publisher=BBC News | date=28 May 2025 | url=https://www.bbc.co.uk/news/articles/c14kp3rdreeo}}</ref>

===Thin films===
When deposited as a [[thin film]], its refractive index and colour make it an excellent reflective optical coating for [[dielectric mirror]]s; it is also used in generating decorative thin films such as found in "mystic fire topaz".{{citation needed|date=December 2024}}

Some grades of modified titanium based pigments as used in sparkly paints, plastics, finishes and cosmetics – these are man-made pigments whose particles have two or more layers of various oxides – often titanium dioxide, [[iron oxide]] or [[alumina]] – in order to have glittering, [[iridescent]] and or [[pearlescent]] effects similar to crushed [[mica]] or [[guanine]]-based products. In addition to these effects a limited colour change is possible in certain formulations depending on how and at which angle the finished product is illuminated and the thickness of the oxide layer in the pigment particle; one or more colours appear by reflection while the other tones appear due to interference of the transparent titanium dioxide layers.<ref>{{cite book|author=Koleske, J. V. |title=Paint and Coating Testing Manual|url=https://books.google.com/books?id=ri6FkY2xvgcC&pg=PA232|year=1995|publisher=ASTM International|isbn=978-0-8031-2060-0|page=232}}</ref> In some products, the layer of titanium dioxide is grown in conjunction with iron oxide by calcination of titanium salts (sulfates, chlorates) around 800&nbsp;°C<ref>{{cite book|author=Koleske, J. V. |title=Paint and Coating Testing Manual|url=https://books.google.com/books?id=ri6FkY2xvgcC&pg=PA229|year=1995|publisher=ASTM International|isbn=978-0-8031-2060-0|page=229}}</ref> One example of a pearlescent pigment is Iriodin, based on mica coated with titanium dioxide or iron (III) oxide.<ref>{{citation |url= http://pearl-effect.com/index.php?option=com_content&view=article&id=92&Itemid=62 |archive-url= https://web.archive.org/web/20120117030508/http://pearl-effect.com/index.php?option=com_content&view=article&id=92&Itemid=62 |archive-date= 17 January 2012 |title= Pearlescence with Iriodin |work= pearl-effect.com}}</ref>

The iridescent effect in these titanium oxide particles is unlike the opaque effect obtained with usual ground titanium oxide pigment obtained by mining, in which case only a certain diameter of the particle is considered and the effect is due only to scattering.

===Sunscreen and UV blocking pigments===
In cosmetic and skin care products, titanium dioxide is used as a pigment, sunscreen and a thickener. As a sunscreen, ultrafine TiO<sub>2</sub> is used, which is notable in that combined with [[Zinc oxide nanoparticle|ultrafine zinc oxide]], it is considered to be an effective sunscreen that lowers the incidence of [[Sunburn|sun burns]] and minimizes the premature [[photoaging]], [[photocarcinogenesis]] and [[immunosuppression]] associated with long term excess sun exposure.<ref>{{Citation|last1=Gabros|first1=Sarah|title=Sunscreens And Photoprotection|date=2021|url=http://www.ncbi.nlm.nih.gov/books/NBK537164/|work=StatPearls|place=Treasure Island (FL)|publisher=StatPearls Publishing|pmid=30725849|access-date=2021-03-06|last2=Nessel|first2=Trevor A.|last3=Zito|first3=Patrick M.}}</ref> Sometimes these UV blockers are combined with iron oxide pigments in sunscreen to increase visible light protection.<ref>{{Cite journal|last1=Dumbuya|first1=Hawasatu|last2=Grimes|first2=Pearl E.|last3=Lynch|first3=Stephen|last4=Ji|first4=Kaili|last5=Brahmachary|first5=Manisha|last6=Zheng|first6=Qian|last7=Bouez|first7=Charbel|last8=Wangari-Talbot|first8=Janet|date=2020-07-01|title=Impact of Iron-Oxide Containing Formulations Against Visible Light-Induced Skin Pigmentation in Skin of Color Individuals|journal=Journal of Drugs in Dermatology |volume=19|issue=7|pages=712–717|doi=10.36849/JDD.2020.5032|issn=1545-9616|pmid=32726103|doi-access=free}}</ref>

Titanium dioxide and zinc oxide are generally considered to be less harmful to [[coral reef]]s than sunscreens that include chemicals such as [[oxybenzone]], [[octocrylene]] and [[octyl methoxycinnamate|octinoxate]].<ref>{{Cite web|title=US Virgin Islands bans sunscreens harming coral reefs|url=https://www.downtoearth.org.in/news/wildlife-biodiversity/us-virgin-islands-bans-sunscreens-harming-coral-reefs-70158|access-date=2021-03-06|website=www.downtoearth.org.in|date=April 2020 |language=en}}</ref>

Nanosized titanium dioxide is found in the majority of physical sunscreens because of its strong UV light absorbing capabilities and its resistance to discolouration under [[ultraviolet]] light. This advantage enhances its stability and ability to protect the skin from ultraviolet light. Nano-scaled (particle size of 20–40&nbsp;nm)<ref>Dan, Yongbo et al. [https://www.perkinelmer.com/CMSResources/Images/44-171045APP_011990_01-NexION-350D-TiO2-NPs-in-Sunscreen.pdf Measurement of Titanium Dioxide Nanoparticles in Sunscreen using Single Particle ICP-MS] {{Webarchive|url=https://web.archive.org/web/20211206180608/https://www.perkinelmer.com/CMSResources/Images/44-171045APP_011990_01-NexION-350D-TiO2-NPs-in-Sunscreen.pdf |date=6 December 2021 }}. perkinelmer.com</ref> titanium dioxide particles are primarily used in sunscreen lotion because they scatter visible light much less than titanium dioxide pigments, and can give UV protection.<ref name="Nano-scaled titania"/> Sunscreens designed for infants or people with [[sensitive skin]] are often based on titanium dioxide and/or [[zinc oxide]], as these mineral UV blockers are believed to cause less skin irritation than other UV absorbing chemicals. Nano-TiO<sub>2</sub>, which blocks both UV-A and UV-B radiation, is used in sunscreens and other cosmetic products.

The EU Scientific Committee on Consumer Safety considered nano sized titanium dioxide to be safe for skin applications, in concentrations of up to 25 percent based on animal testing.<ref>{{Cite web|url=https://ec.europa.eu/health/scientific_committees/consumer_safety/docs/sccs_o_136.pdf|title=Health_scientific_committees}}</ref> The risk assessment of different titanium dioxide nanomaterials in sunscreen is currently evolving since nano-sized TiO<sub>2</sub> is different from the well-known micronized form.<ref name=":2">{{Cite journal|date=2010|title=Sunscreens with Titanium Dioxide (TiO<sub>2</sub>) Nano-Particles: A Societal Experiment|journal=Nanoethics|pmc=2933802|last1=Jacobs|first1=J. F.|last2=Van De Poel|first2=I.|last3=Osseweijer|first3=P.|volume=4|issue=2|pages=103–113|doi=10.1007/s11569-010-0090-y|pmid=20835397}}</ref> The rutile form is generally used in cosmetic and sunscreen products due to it not possessing any observed ability to damage the skin under normal conditions<ref>{{Cite web|last=cosmeticsdesign-europe.com|title=Scientists encourage 'safer' rutile form of TiO<sub>2</sub> in cosmetics|url=https://www.cosmeticsdesign-europe.com/Article/2013/09/26/Scientists-encourage-safer-rutile-form-of-TiO2-in-cosmetics|access-date=2021-03-06|website=cosmeticsdesign-europe.com|date=25 September 2013 |language=en-GB}}</ref> and having a higher [[UV protection|UV absorption]].<ref name=":3">{{Cite journal|date=29 March 2006|title=Characteristics of silica-coated TiO<sub>2</sub> and its UV absorption for sunscreen cosmetic applications|url=https://analyticalsciencejournals.onlinelibrary.wiley.com/doi/abs/10.1002/sia.2313|journal=Wiley Analytical Science|doi=10.1002/sia.2313|via=Wiley Online Library|last1=Jaroenworaluck|first1=A.|last2=Sunsaneeyametha|first2=W.|last3=Kosachan|first3=N.|last4=Stevens|first4=R.|volume=38|issue=4|pages=473–477|s2cid=97137064 |url-access=subscription}}</ref> In 2016 Scientific Committee on Consumer Safety (SCCS) tests concluded that the use of nano titanium dioxide (95–100% rutile, ≦5% anatase) as a UV filter can be considered to not pose any risk of adverse effects in humans post-application on healthy skin,<ref name="Eur Acad Dermatol Venereol">{{Cite journal |last1=Dréno |first1=B. |last2=Alexis |first2=A. |last3=Chuberre |first3=B. |last4=Marinovich |first4=M. |date=2019 |title=Safety of titanium dioxide nanoparticles in cosmetics |journal=Journal of the European Academy of Dermatology and Venereology |language=en |volume=33 |issue=S7 |pages=34–46 |doi=10.1111/jdv.15943 |issn=0926-9959 |pmid=31588611 |s2cid=203849903 |doi-access=free |hdl-access=free |hdl=2434/705700}}</ref> except in the case the application method would lead to substantial risk of inhalation (ie; powder or spray formulations). This safety opinion applied to nano TiO<sub>2</sub> in concentrations of up to 25%.<ref name=":4">{{Cite journal|date=7 November 2016|title=OPINION ON additional coatings for Titanium Dioxide (nano form) as UV-filter in dermally applied cosmetic products|url=https://ec.europa.eu/health/scientific_committees/consumer_safety/docs/sccs_o_202.pdf|journal=Scientific Committee on Consumer Safety|publisher=European Commission|via=ec.europa.eu}}</ref>

Initial studies indicated that nano-TiO<sub>2</sub> particles could penetrate the skin, causing concern over its use. These studies were later refuted, when it was discovered that the testing methodology couldn't differentiate between penetrated particles and particles simply trapped in hair follicles and that having a diseased or physically damaged dermis could be the true cause of insufficient barrier protection.<ref name=":2" />

SCCS research found that when nanoparticles had certain photostable coatings (e.g., [[alumina]], [[Silicon dioxide|silica]], cetyl phosphate<!--Q27292009-->, [[Silicone#Personal care|triethoxycaprylylsilane]], [[manganese dioxide]]), the photocatalytic activity was attenuated and no notable skin penetration was observed; the sunscreen in this research was applied at amounts of 10&nbsp;mg/cm2 for exposure periods of 24 hours.<ref name=":4" /> Coating TiO<sub>2</sub> with alumina, silica, [[zircon]] or various [[polymer]]s can minimize [[avobenzone]] degradation<ref>{{Cite journal|title=Preparation of rutile TiO<sub>2</sub>@avobenzone composites for the further enhancement of sunscreen performance|url=https://pubs.rsc.org/en/content/articlelanding/2016/ra/c6ra23282e#!divRelatedContent&articles|journal=RSC Advances|bibcode=2016RSCAd...6k1865W|via=Royal society of chemistry|last1=Wang|first1=Can|last2=Zuo|first2=Shixiang|last3=Liu|first3=Wenjie|last4=Yao|first4=Chao|last5=Li|first5=Xiazhang|last6=Li|first6=Zhongyu|year=2016|volume=6|issue=113|page=111865|doi=10.1039/C6RA23282E|url-access=subscription}}</ref> and enhance UV absorption by adding an additional light diffraction mechanism.<ref name=":3" />

{{Chem|Ti|O|2}} is used extensively in plastics and other applications as a white pigment or an opacifier and for its UV resistant properties where the powder disperses light – unlike organic UV absorbers – and reduces UV damage, due mostly to the particle's high refractive index.<ref>[http://www2.dupont.com/Titanium_Technologies/en_US/tech_info/literature/Plastics/PL_B_Polymers_Light_Science.pdf Polymers, Light and the Science of TiO<sub>2</sub>] {{Webarchive|url=https://web.archive.org/web/20170329071755/http://www2.dupont.com/Titanium_Technologies/en_US/tech_info/literature/Plastics/PL_B_Polymers_Light_Science.pdf |date=29 March 2017 }}, DuPont, pp. 1–2</ref>

===Other uses of titanium dioxide===
In [[ceramic glaze]]s, titanium dioxide acts as an opacifier and seeds [[crystal]] formation.

It is used as a [[tattoo]] pigment and in [[styptic pencil]]s. Titanium dioxide is produced in varying particle sizes which are both oil and water dispersible, and in certain grades for the cosmetic industry. It is also a common ingredient in toothpaste.

The exterior of the [[Saturn V]] rocket was painted with titanium dioxide; this later allowed astronomers to determine that [[J002E3]] was likely the [[S-IVB]] stage from [[Apollo 12]] and not an [[asteroid]].<ref name=Jorgensen>{{cite journal |bibcode= 2003DPS....35.3602J |last1= Jorgensen |first1= K. |last2= Rivkin |first2= A. |last3= Binzel |first3= R. |last4= Whitely |first4= R. |last5= Hergenrother |first5= C. |last6= Chodas |first6= P. |last7= Chesley |first7= S. |last8= Vilas |first8= F. |title= Observations of J002E3: Possible Discovery of an Apollo Rocket Body |journal= [[Bulletin of the American Astronomical Society]] |date= May 2003 |volume= 35 |page= 981}}</ref>

Titanium dioxide is an [[n-type semiconductor]] and is used in [[dye-sensitized solar cell]]s.<ref>{{Cite journal |last1=Aboulouard |first1=Abdelkhalk |last2=Gultekin |first2=Burak |last3=Can |first3=Mustafa |last4=Erol |first4=Mustafa |last5=Jouaiti |first5=Ahmed |last6=Elhadadi |first6=Benachir |last7=Zafer |first7=Ceylan |last8=Demic |first8=Serafettin |date=2020-03-01 |title=Dye sensitized solar cells based on titanium dioxide nanoparticles synthesized by flame spray pyrolysis and hydrothermal sol-gel methods: a comparative study on photovoltaic performances |journal=Journal of Materials Research and Technology |volume=9 |issue=2 |pages=1569–1577 |doi=10.1016/j.jmrt.2019.11.083 |issn=2238-7854|doi-access=free }}</ref> It is also used in other electronics components such as [[electrode]]s in batteries.<ref>{{Cite journal |last1=Mahmoud |first1=Zaid H. |last2=Ajaj |first2=Yathrib |last3=Kamil Ghadir |first3=Ghadir |last4=Musaad Al-Tmimi |first4=Hayder |last5=Hameed Jasim |first5=Hamza |last6=Al-Salih |first6=Moatasem |last7=Hasen shuhata Alubiady |first7=Mahmood |last8=Muzahem Al-Ani |first8=Ahmed |last9=Salih Jumaa |first9=Sally |last10=Azat |first10=Seitkhan |last11=Fadhil Smaisim |first11=Ghassan |last12=kianfar |first12=Ehsan |date=2024-01-01 |title=Carbon-doped titanium dioxide (TiO2) as Li-ion battery electrode: Synthesis, characterization, and performance |journal=Results in Chemistry |volume=7 |pages=101422 |doi=10.1016/j.rechem.2024.101422 |issn=2211-7156|doi-access=free }}</ref>