Transportable Mononuclear Metal Atoms as Building Blocks for Bottom-up Material Fabrication: Pt1(0) and Au1(0) Atoms in Stock Solutions

Premade and readily transportable mononuclear zero-valent metal atoms in stock solvents offer the potential capability for bottom-up designable metallic material fabrication. This work demonstrates a potentially universal and practical strategy to prepare weakly shielded mononuclear metal atoms in a volatile solvent, which also constitutes a strippable ligand to the metal atoms. Herein, M-1(0) (M=Pt, Au) atoms are prepared by reducing H2PtCl6 and HAuCl4 with ethanol in ethylene glycol diethyl ether (EGDE) under mild temperatures. The diether oxygens of EGDE, H+, and Cl- coordinating to the M-1(0) atoms, make the M-1(0) atoms stable in the solvent under low pH. However, the M-1(0) atoms can be released either by evaporation of HCl and EGDE or through neutralization of the HCl with a base. The premade M-1(0) atoms can be used as primary building blocks to construct designable materials. To demonstrate a potential application, the M-1(0) atoms are conveniently transported onto the surface of TiO2 through impregnation followed by mild heating. The atomic dispersion and reduced state of the metal atoms are well preserved, as verified by HAADF-STEM images, XPS, and DRIFT spectroscopy.