Editing Colloidal gold (section)

==History==
[[File:Vintage cranberry glass.jpg|thumb|left|This [[cranberry glass]] bowl was made by adding a gold salt (probably gold chloride) to molten glass.]] 
Used since ancient times as a method of [[Stained glass|staining glass]], colloidal gold was used in the 4th-century [[Lycurgus Cup]], which changes color depending on the location of light source.<ref>{{Cite web|title = The Lycurgus Cup|url = https://www.britishmuseum.org/research/collection_online/collection_object_details.aspx?objectId=61219&partId=1&searchText=Lycurgus%2520Cup|website = British Museum|access-date = 2015-12-04}}</ref><ref>{{Cite journal|last1=Freestone|first1=Ian|last2=Meeks|first2=Nigel|last3=Sax|first3=Margaret|last4=Higgitt|first4=Catherine | name-list-style = vanc |title=The Lycurgus Cup — A Roman nanotechnology |journal=Gold Bulletin|volume=40|issue=4|pages=270–277|doi=10.1007/BF03215599 |year=2007|doi-access=free}}</ref>

During the [[Middle Ages]], soluble gold, a solution containing [[Gold salts|gold salt]], had a reputation for its curative property for various diseases. In 1618, [[Francis Anthony]], a philosopher and member of the medical profession, published a book called ''Panacea Aurea, sive tractatus duo de ipsius Auro Potabili''<ref>{{Cite book|title = Panacea aurea sive Tractatus duo de ipsius auro potabili|last = Antonii|first = Francisci| name-list-style = vanc |publisher = Ex Bibliopolio Frobeniano|year = 1618}}</ref> (Latin: gold potion, or two treatments of [[Drinking water|potable]] gold). The book introduces information on the formation of colloidal gold and its medical uses. About half a century later, English botanist [[Nicholas Culpeper|Nicholas Culpepper]] published a book in 1656, ''Treatise of Aurum Potabile'',<ref>{{Cite book|title = Mr. Culpepper's Treatise of aurum potabile Being a description of the three-fold world, viz. elementary celestial intellectual containing the knowledge necessary to the study of hermetick philosophy. Faithfully written by him in his life-time, and since his death, published by his wife.|last = Culpeper|first = Nicholas | name-list-style = vanc |year = 1657|location = London}}</ref> solely discussing the medical uses of colloidal gold.

In 1676, [[Johann von Löwenstern-Kunckel|Johann Kunckel]], a German chemist, published a book on the manufacture of stained glass. In his book ''Valuable Observations or Remarks About the Fixed and Volatile Salts-Auro and Argento Potabile, Spiritu Mundi and the Like'',<ref>{{Cite book|title = Utiles observationes sive animadversiones de salibus fixis et volatilibus, auro et argento potabili (etc.)|last = Kunckel von Löwenstern|first = Johann | name-list-style = vanc |publisher = Wilson|year = 1678|location = Austria}}</ref> Kunckel assumed that the pink color of Aurum Potabile came from small particles of metallic gold, not visible to human eyes. In 1842, [[John Herschel]] invented a photographic process called [[chrysotype]] (from the Greek {{lang|grc|χρῡσός}} meaning "gold") that used colloidal gold to record images on paper.

Modern scientific evaluation of colloidal gold did not begin until [[Michael Faraday|Michael Faraday's]] work in the 1850s.<ref name="ref2">{{cite journal | vauthors = Reddy VR | title = Gold nanoparticles: synthesis and applications. | journal = Synlett | date =  July 2006 | volume = 2006 | issue = 11 | pages = 1791–2 | doi = 10.1055/s-2006-944219 | doi-access = free }}</ref><ref name = "Faraday_1857">{{cite journal | vauthors = Faraday M |title=The Bakerian Lecture: Experimental Relations of Gold (and Other Metals) to Light |journal=Philosophical Transactions of the Royal Society of London |date=January 1857 |volume=147 |pages=145–181 |doi=10.1098/rstl.1857.0011|url=https://zenodo.org/record/1432422 |doi-access=free |bibcode=1857RSPT..147..145F }}</ref> In 1856, in a basement laboratory of [[Royal Institution]], Faraday accidentally created a ruby red solution while mounting pieces of gold leaf onto microscope slides.<ref>{{Cite web|title = Michael Faraday's gold colloids {{!}} The Royal Institution: Science Lives Here|url = http://www.rigb.org/our-history/iconic-objects/iconic-objects-list/faraday-gold-colloids|website = www.rigb.org|access-date = 2015-12-04}}</ref> Since he was already interested in the properties of light and matter, Faraday further investigated the optical properties of the colloidal gold. He prepared the first pure sample of colloidal gold, which he called 'activated gold', in 1857. He used [[phosphorus]] to [[Redox|reduce]] a solution of gold chloride. The colloidal gold Faraday made 150 years ago is still optically active. For a long time, the composition of the 'ruby' gold was unclear. Several chemists suspected it to be a gold [[tin]] compound, due to its preparation.<ref>{{cite journal | journal = Annalen der Physik | year = 1832 | volume = 101 | issue = 8 | pages = 629–630 | title = Ueber den Cassius'schen Goldpurpur | last = Gay-Lussac | doi = 10.1002/andp.18321010809 | bibcode = 1832AnP...101..629G | url = https://zenodo.org/record/1423556 }}</ref><ref>{{cite journal | journal = Annalen der Physik | volume = 98 | issue = 6 | pages = 306–308 | title = Ueber den Cassius' schen Goldpurpur | vauthors = Berzelius JJ | doi = 10.1002/andp.18310980613 | year = 1831 | bibcode = 1831AnP....98..306B | url = https://zenodo.org/record/1423548 }}</ref> Faraday recognized that the color was actually due to the miniature size of the gold particles. He noted the [[light scattering]] properties of suspended gold microparticles, which is now called [[Tyndall effect|Faraday-Tyndall effect]].<ref name = "Faraday_1857" />

In 1898, [[Richard Adolf Zsigmondy]] prepared the first colloidal gold in diluted solution.<ref>{{cite web | url = https://www.nobelprize.org/uploads/2017/03/zsigmondy-lecture.pdf | first = Richard | last = Zsigmondy | name-list-style = vanc | title = Properties of colloids | publisher = Nobel Foundation | date = December 11, 1926 | access-date = 2022-09-19}}</ref> Apart from Zsigmondy, [[Theodor Svedberg]], who invented [[ultracentrifugation]], and [[Gustav Mie]], who provided the [[Mie Scattering|theory for scattering and absorption by spherical particles]], were also interested in the synthesis and properties of colloidal gold.<ref name="ReferenceA" /><ref>{{cite journal|title=Size dependence of Au NP-enhanced surface plasmon resonance based on differential phase measurement |journal=Sensors and Actuators B: Chemical |year=2013 |doi=10.1016/j.snb.2012.09.073 |volume=176|pages=1128–1133|last1=Zeng |first1=Shuwen |last2=Yu |first2=Xia |last3=Law |first3=Wing-Cheung |last4=Zhang |first4=Yating |last5=Hu |first5=Rui |last6=Dinh |first6=Xuan-Quyen |last7=H o|first7=Ho-Pui |last8=Yong |first8=Ken-Tye |bibcode=2013SeAcB.176.1128Z | name-list-style = vanc  |url=https://www.researchgate.net/publication/268225952 }}</ref>

With advances in various analytical technologies in the 20th century, studies on gold nanoparticles has accelerated. Advanced microscopy methods, such as [[atomic force microscopy]] and [[Electron microscope|electron microscopy]], have contributed the most to nanoparticle research. Due to their comparably easy synthesis and high stability, various gold particles have been studied for their practical uses. Different types of gold nanoparticle are already used in many industries.