From Au(i) organometallic hydrogels to well-defined Au(0) nanoparticles

Abstract

The reaction of water soluble phosphine 3,7-diacetyl-1,3,7-triaza-5-phosphabicyclo[3.3.1]nonane (DAPTA) with [Au(CC–C₅H₄N)]_n yields a luminescent water soluble phosphine gold(I) alkynyl complex [Au(4-pyridylethynyl)(DAPTA)] that leads to the formation of a luminescent hydrogel. A small variation of the phosphine structure (introduction of acetyl groups) with respect to the previously reported complex [Au(4-pyridylethynyl)(PTA)] has a clear effect on the observed properties: (i) a great increase in the hydrogel entanglement structure has been observed; (ii) the different cross-linking structures give rise to specific emission properties. The hydrogel was characterized by different techniques (¹H-NMR, absorption and emission spectroscopy, optical microscopy, fluorescent microscopy (FM) and SEM). FM together with microspectrofluorimetry measurements has determined different emissive properties that vary according to the cross-linking process. Thermal treatments of the hydrogel produce well-defined metallic gold nanoparticles with a remarkable narrow size distribution, which have been characterized by SEM, TEM and X-ray photoelectron spectroscopy (XPS). At 200 °C, Au particles measuring 1.0 ± 0.2 nm were obtained. Au nanoparticles were also formed as a result of electron beam irradiation.