There have been many recent reports using thiol ligands as a sulfur source for semiconductor nanoparticle synthesis to give high quality products. Thiol regents yield particles of Cu2S and CuInS2 that are single crystalline and monodisperse; shells of ZnS and CdS on CdSe prepared in this manner have exceptional fluorescence yields and reduced blinking. We show evidence here that in these syntheses the final capping thiols are incorporated into the particle in high coordination number sites which greatly affects the surface chemistry and electronic structure of the particles.Strongly �crystal-bound� thiols are resistant to ligand exchange and surface modification, limiting the further application of these particles.  To circumvent this challenge, dodecyl-3-mercaptopropanoate, a molecule possessing both a thiol and an ester, was used as the sulfur source for the synthesis of Cu2S, CuInS2, and a ZnS shell around CdSe.  A post-synthesis base hydrolysis cleaves the ester, leaving a carboxylate and rendering the particles water-soluble.  In the CdSe@ZnS system, when compared to surface-bound thiols, crystal-bound thiols demonstrated increased electronic coupling to the nanoparticle core, allowing for increased efficiencies of photoinduced charge transfer to solution species.

Thiols as ligands and sulfur sources: Capping ligands that are more than skin deep

247th National Meeting (2014)

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