One-pot synthesis of gold nanoparticles densely coated with nitroxide spins

Abstract

We describe a new and simple method for one-pot synthesis of gold nanoparticles of spherical shape densely coated with unpaired electrons. The gold nanoparticles have a narrow size distribution (1.90±0.54nm) and even coverage of nitroxide spins per particle and are soluble both in non-polar and polar organic solvents. The one-pot synthesis consists of direct grafting of nanoparticles by ligand substitution with an in situ generated bisnitroxide radical-containing thiol nucleophile. The obtained nanoparticles are stabilized by two types of ligands: covalently attached nitroxide radicals and tetraoctylammonium bromide ions pairs weakly bound to the gold surface. The average number of ligands per core was derived from X-ray photoelectron spectroscopy (XPS) as well as from thermogravimetric and bromine concentration analyses. The proposed procedure can be a powerful tool for the preparation of spin-labeled gold nanoparticles soluble in non-polar and polar organic solvents which should be useful for applications in various fields including biochemistry, catalysis and electrochemistry.