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==Grafting reactions==
In a potential application in [[nanotechnology]], the diazonium salts 4-chlorobenzenediazonium tetrafluoroborate very efficiently functionalizes [[Carbon nanotube|single wall nanotubes]].<ref>{{cite journal | doi = 10.1021/ja053998c | volume=127 | title=Green Chemical Functionalization of Single-Walled Carbon Nanotubes in Ionic Liquids | year=2005 | journal=Journal of the American Chemical Society | pages=14867–14870 | last1 = Price | first1 = B. Katherine| issue=42 | pmid=16231941 }}</ref> In order to [[Exfoliation (chemistry)|exfoliate]] the nanotubes, they are mixed with an [[ionic liquid]] in a [[mortar and pestle]]. The diazonium salt is added together with [[potassium carbonate]], and after grinding the mixture at [[room temperature]] the surface of the nanotubes are covered with chlorophenyl groups with an efficiency of 1 in 44 carbon atoms. These added [[substituent
It is also possible to functionalize [[silicon wafer]]s with diazonium salts forming an [[aryl]] monolayer. In one study, the silicon surface is washed with [[ammonium hydrogen fluoride]] leaving it covered with silicon–hydrogen bonds (hydride passivation).<ref>{{Cite journal | title = Direct Covalent Grafting of Conjugated Molecules onto Si, GaAs, and Pd Surfaces from Arenediazonium Salts |author1=Michael P. Stewart |author2=Francisco Maya |author3=Dmitry V. Kosynkin |author4=Shawn M. Dirk |author5=Joshua J. Stapleton |author6=Christine L. McGuiness |author7=David L. Allara |author8=James M. Tour |display-authors=3 |journal= [[J. Am. Chem. Soc.]] |doi= 10.1021/ja0383120 |year= 2004 |volume= 126 |pages= 370–8 |pmid= 14709104 |issue= 1}}</ref> The reaction of the surface with a solution of diazonium salt in [[acetonitrile]] for 2 hours in the dark is a spontaneous process through a [[free radical]] [[reaction mechanism|mechanism]]:<ref>Reaction sequence: silicon surface reaction with [[ammonium hydrogen fluoride]] creates [[hydride]] layer. An electron is transferred from the silicon surface to the diazonium salt in an [[open circuit potential]] reduction leaving a silicon [[radical cation]] and a diazonium radical. In the next step a proton and a nitrogen molecule are expelled and the two radical residues recombine creating a surface silicon to carbon bond.</ref>
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