Functionalized Self-Assembled Peptide Nanotubes with Cobalt Ferrite Nanoparticles for Applications in Organic Electronics

Here, we report the functionalization of diphenylalanine (FF)-based self-assembled nanotubes with cobalt ferrite (CFO) magnetic nanoparticles. Electron microscopy images show the CFO nanoparticles to be uniformly dispersed on the peptide nanotubes. We investigate the interaction between CFO nanoparticles and FF nanotubes by optical spectroscopy, X-ray photoelectron spectroscopy (XPS), and magnetization measurements. The changes in the XPS data from pristine FF nanotubes and CFO:FF nanotubes are indicative of charge transfer from CFO to FF nanotubes, changing the electronic states of the Fe2+ and Co2+ ions. The A1g Raman peak of CFO at 675 cm–1 hardens in CFO:FF nanotubes, signaling an enhancement of the stiffness constant of the iron–oxygen bond due to charge transfer. A comparison of the magnetic characterization from CFO nanoparticles and the CFO:FF nanocomposite shows a higher saturation magnetization from the nanocomposite, which is attributed to a change in the cationic distribution in CFO upon binding with the peptide. The functionalized FF nanotubes open up applications in organic electronics, specifically in low-operating voltage pentacene field-effect transistors.