Research Paper

Journal of Nanoparticle Research

, Volume 11, Issue 8, pp 1895-1903

Janus nanoparticles: reaction dynamics and NOESY characterization

  • Sulolit PradhanAffiliated withDepartment of Chemistry and Biochemistry, University of California
  • , Lauren E. BrownAffiliated withDepartment of Chemistry and Biochemistry, University of California
  • , Joseph P. KonopelskiAffiliated withDepartment of Chemistry and Biochemistry, University of California
  • , Shaowei ChenAffiliated withDepartment of Chemistry and Biochemistry, University of California Email author 

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Abstract

Janus nanoparticles were prepared by taking advantage of interfacial ligand exchange reactions of hydrophobic hexanethiolate-protected gold nanoparticles with hydrophilic 2-(2-mercaptoethoxy)ethanol (MEA). A monolayer of the particles was first formed at the air–water interface by the Langmuir technique and then deposited onto a substrate surface by the Langmuir–Blodgett method. The particle monolayer was then immersed into an aqueous solution of MEA for different periods of time. It was found that the exchange reactions occurred but were limited only to the top face of the nanoparticles and the reaction reached equilibrium in about 8 h. The resulting particles exhibited amphiphilic characters as confirmed by contact angle and UV–visible, FTIR and NMR spectroscopic measurements. Of these, the structural discrepancy between the Janus nanoparticles and bulk-exchanged particles was clearly manifested, in particular, by NOESY NMR measurements.

Keywords

Janus nanoparticles Langmuir–Blodgett Contact angle NOESY NMR Surface plasmon Exchange reactions Monolayer