Controlled assembly of protein-protected gold nanoparticles on noncovalent functionalized carbon nanotubes

We investigated the noncovalent functionalization of multi-walled carbon nanotubes (MWCNTs) by an aromatic chemical, 1-pyrenebutyric acid N-hydroxysuccinimide ester (PANHS), and produced four protein- (fibrinogen, γ-globulin, hemoglobin, and fibronectin) protected gold nanoparticles (AuNPs) by a simple strategy. The formation of protein-protected AuNPs was evidenced by UV–vis spectra, X-ray photoelectron spectroscopy (XPS), and transmission electron microscopy (TEM), the successful chemical modification of MWCNTs with PANHS was identified by XPS and Raman spectra, and the MWCNT–AuNP hybrids were observed by TEM. We concluded that proteins can mediate the assembly of protein-protected AuNPs on PANHS-functionalized MWCNTs. Proteins, as an intermediate that can react with both MWCNTs and AuNPs, play a significant role for mediating the formation of different hybrids based on MWCNTs. This work provides a simple and potent strategy to prepare CNT–NP hybrids by using the interaction between CNTs and biomacromolecules, and on the other hand provides a potential application of protein-protected metallic NPs for preparing novel nanomaterials.