Editing Colloidal gold (section)

===Toxicity and hazards in synthesis===
While AuNPs themselves appear to have low or negligible toxicity,{{citation needed|date=December 2016}} and the literature shows that the toxicity has much more to do with the ligands rather than the particles themselves, the synthesis of them involves chemicals that are hazardous. [[Sodium borohydride]], a harsh reagent, is used to reduce the gold ions to gold metal.<ref>{{cite journal | vauthors = Perala SR, Kumar S | title = On the mechanism of metal nanoparticle synthesis in the Brust-Schiffrin method | journal = Langmuir | volume = 29 | issue = 31 | pages = 9863–73 | date = August 2013 | pmid = 23848382 | doi = 10.1021/la401604q }}</ref> The gold ions usually come from [[chloroauric acid]], a potent acid.<ref name="Cellular uptake"/> Because of the high toxicity and hazard of reagents used to synthesize AuNPs, the need for more “green” methods of synthesis arose.