Step-by-step characterization of a series of polyamidoamine dendrons on carbon nanohorn surface

Abstract

Polyamidoamine (PAMAM) dendrimers/dendrons chemically functionalized on carbon nanohorns (CNHs) have exhibited an excellent ability, especially for energy conversion and gene therapy applications. However, the main issue is its low functional group coverage, and the low reaction yield has been less understood. Here, we examine the surface state and functionalization efficiency of PAMAM dendrons on CNHs in each reaction step. The multifaceted measurements using Raman, ζ potential, and Fourier transform infrared spectroscopy (FT-IR) demonstrate that PAMAM dendrons are successfully synthesized on CNH surfaces. In addition, highly sensitive energy dispersive X-ray spectroscopy in the scanning electron microscope (SEM-EDS) enables precise evaluation of functional group coverage consistent with the chemical structure of each product. Furthermore, the detailed analysis of SEM-EDS imaging, morphology characterization, and FT-IR provides chemical information regarding the reactivity of PAMAM functionalization on CNHs. One important finding is that chemical interaction by hydrogen bonds among PAMAM/CNH molecules is a considerable possibility for low reactivity. Our results are widely beneficial for the realization of highly efficient grafting of PAMAM dendrons on various carbon nanomaterials.