Photostimulated Reversible Attachment of Gold Nanoparticles on Multiwalled Carbon Nanotubes

In this study, a hybrid system of gold nanoparticles and multiwalled carbon nanotubes (MWNTs) with a switching function was successfully realized through photocontrolled host-guest interaction based on alpha-cyclodextrin (alpha-CD) and azobenzene derivatives. First, the azobenzene derivative was covalently bonded onto the surface of MWNTs by a simple and effective reaction, leading to highly water-soluble MWNTs. Then, narrowly distributed gold nanoparticles were prepared using thiolated alpha-CD as a capping agent. Because of the photochemically controlled inclusion-exclusion interaction between the azobenzene moiety and alpha-CD, the reversible attachment of gold nanoparticles onto the MWNT surface was realized. TEM observation traced and testified to this reversible process, and at the same time Raman spectra provided convincing proof of the photoisomerization process.