Nucleobase-metal hybrid materials: Preparation of submicrometer-scale, spherical colloidal particles of adenine-gold(III) via a supramolecular hierarchical self-assembly approach

We report a simple and effective supramolecular route for facile synthesis of submicrometer-scale, hierarchically self-assembled spherical colloidal particles of adenine - gold(III) hybrid materials at room temperature. Simple mixture of the precursor aqueous solutions of adenine and HAuCl4 at room temperature could result in spontaneous formation of the hybrid colloidal particles. Optimization of the experimental conditions could yield uniform-sized, self-assembled products at 1:4 molar ration of adenine to HAuCl4. Transmission electron microscopy results reveal the formation of hierarchical self-assembled structure of the as-prepared colloidal particles. Concentration dependence, ratio dependence, time dependence, and kinetic measurements have been investigated. Moreover, spectroscopic evidence [i.e., Fourier transform infrared (FTIR) and UV-vis spectra and wide-angle X-ray scattering data] of the interaction motives causing the formation of the colloidal particles is also presented. The as-prepared nucleobase -metal hybrid materials exhibited hierarchical assembly as follows: the coordination interactions of Au(III) and N atoms in adenine could produce 2-3 nm small particles, these small particles could evolve into submicrometer spherical colloidal particles via noncovalent interaction (i.e., aromatic pi-pi stacking of adenine), and finally the submicrometer particles could be connected together through fusion of the fringes of every independent particle. Our work here may open up new possibilities for the fabrication of noncovalent interaction colloidal particles and for the preparation of decomposable colloidal templates.