G1 dendrimers-mediated evolution of silver nanostructures from nanoparticles to solid spheres.
With the control of G1 poly(amidoamine) (PAMAM), an evolutionary course of stable colloidal silver from discrete nanoparticles to solid spheres through ultraviolet irradiation reduction of silver nitrate solutions was observed by transmission electron microscopy (TEM). The morphologies of the products depend on the Ag+ concentration. A mechanism of globular assembly was put forward to interpret the evolution of the nanostructures. Powder X-ray diffraction (XRD), electron diffraction (ED) patterns, and X-ray photoelectron spectroscopy (XPS) indicate the presence of cubic symmetry silver. XPS and Fourier transform infrared (FT-IR) spectroscopy confirm that dendrimers have participated in the stabilization and control of Ag nanostructures. In the UV-vis spectra, the intense surface plasmons are centered at 425 and 430 nm corresponding to the shapes of dots and solid spheres, respectively. The solid spheres exhibit excellent catalytic efficiency on the reduction of 2,7-dicholoroflurescein (DCF).
Hydrogen bonding interactions between Starburst dendrimers and several molecules of biological interest
1H NMR spectroscopy was used to analyze the interactions between poly(amidoamine) (PAMAM) Starburst dendrimers (SBDs) 1–4 and several biologically important guests (pyridine, quinoline, quinazoline, nicotine and trimethadione). Association constants obtained from changes in the chemical shifts of the amide protons in the host indicate two different interaction sites inside and on the periphery of the dendrimer. Binding at the inner site is inhibited in the ester-terminated dendrimers. Copyright © 1998 John Wiley & Sons, Ltd.
Photoinduced electron-transfer reactions to probe the structure of starburst dendrimers
The photoinduced electron transfers between species adsorbed on the carboxylate-terminated starburst dendrimers demonstrate that a change in dendrimer structural features occurs about generation 3.5, in agreement with the shape transition predicted on the basis of theoretical calculations