Surface Modification of Au Nanoparticles with Heteroleptic Cu(I) Diimine Complexes

Abstract

Gold colloidal nanoparticles (NPs) were functionalized in acetonitrile with a Cu­(I) complex consisting of one 2,2′-bipyridine ligand possessing a lipoic acid moiety and one 2,9-dimesitylene-1,10-phenanthroline. UV electronic absorption, inductively coupled plasma-atomic emission spectroscopy, and scanning transmission electron microscopy with energy-dispersive X-ray analysis specifically targeting the Cu element were employed to confirm the grafting of the metallic complex on the Au NPs via Au–S bond formation and to probe its surface distribution and surface coverage. At the highest coverage achieved while retaining nanoparticle dispersibility, we estimate the molecular footprint of the complex at 0.71 nm2, corresponding to ∼7000 molecules over a 40 nm spherical particle. This is only four time less than what is reported for much smaller alkanethiols forming a compact self-assembled monolayer on similar gold nanoparticles. In the surface-enhanced Raman spectra (SERS), we underline a convenient marker band at ∼1000 cm–1; its frequency position is indicative of the complexation state of the surface-bound bipyridine molecules. From the analysis of the normal Raman spectra of the powders and the SERS data, the anchored tetrahedral complex is presumed to orient with the two polycyclic ligands predominantly normal to the surface and the most cumbersome substituted phenanthroline more peripherally placed.

The Molecular Footprint of Peptides on the Surface of Ultrasmall Gold Nanoparticles (2 nm) Is Governed by Steric Demand

“…They showed a decrease in ligand density with an increase in steric demand . Picardi et al demonstrated that a copper complex with a disulfide ligand (lipoic acid) can bind to the surface of 40 nm gold nanoparticles with a molecular footprint of 0.71 nm 2 . Ming et al found a molecular footprint of 0.24 nm 2 for pyrene-carrying thioesters and thiocarbonates on 12.5 nm gold particles .…”

“…77 Picardi et al demonstrated that a copper complex with a disulfide ligand (lipoic acid) can bind to the surface of 40 nm gold nanoparticles with a molecular footprint of 0.71 nm 2 . 78 Ming et al found a molecular footprint of 0.24 nm 2 for pyrene-carrying thioesters and thiocarbonates on 12.5 nm gold particles. 79 Ruks et al synthesized cysteine-functionalized ultrasmall gold nanoparticles.…”

Enhanced Visible Light Absorption in Heteroleptic Cuprous Phenanthrolines

“…Two classes of Cu­(I) bis -phenanthrolines engender either homoleptic or heteroleptic ligand topologies. Homoleptic cuprous phenanthrolines have been studied since the 1970s for their potent photoreducing capabilities, long-lived excited states, and tremendous durability to high-power laser excitation. ,,− Heteroleptic complexes using diimine- and bis -phosphine-type ligands have been growing in interest, especially for applications in dye-sensitized solar cells, − photoredox catalysis, − and the construction of supramolecular donor–acceptor architectures. ,,− The HETPHEN strategy leverages 2,9-mesityl-1,10-phenanthroline (mesPhen), ,, which is unable to form a bis -homoleptic complex but enables the binding of another suitable phenanthroline, assisted through π-interactions with the 2,9-mesityl substituents and the B-ring of the orthogonally coordinated phenanthroline. This platform facilitates a facile pathway for obtaining heteroleptic Cu­(I) complexes with the generic formula [Cu­(mesPhen)­(L)] + , where L is a second and distinct phenanthroline ligand (Chart ).…”