Charge Transfer at Hybrid Interfaces: Plasmonics of Aromatic Thiol-Capped Gold Nanoparticles

Abstract

Although gold nanoparticles stabilized by organic thiols are the building blocks in a wide range of applications, the role of the ligands on the plasmon resonance of the metal core has been mostly ignored until now. Herein, a methodology based on the combination of spectroscopic ellipsometry and UV-vis spectroscopy is applied to extract dielectric functions of the different components. It is shown that aromatic thiols allow a significant charge transfer at the hybrid interface with the s and d bands of the gold core that yields "giant" red shifts of the plasmon band, up to 40 nm for spherical particles in the size range of 3-5 nm. These results suggest that hybrid nanoplasmonic devices may be designed through the suitable choice of metal core and organic components for optimized charge exchange.

Quantified Binding Scale of Competing Ligands at the Surface of Gold Nanoparticles: The Role of Entropy and Intermolecular Forces

“…The first case would be related to changes in the distribution of the ligands in the mixed SAMs upon a change in the concentration. This cause can be ruled out based on previous reports that always show similar stripy or patchy, relatively homogeneous distributions of ligands on 5‐nm nanoparticles . The second case relates to the solubility of TerPh in chloroform, which may be close to the high concentration investigated ([particle] = 10 −4 m ) and displace Equation toward TerPh binding.…”

“…Because of their similar length, DDT and TerPh should yield similar solvation layers, so that surface energies may not drive the exchange of DDT with TerPh . For the other arylthiols, as explained above, relatively homogeneous distributions of ligands are expected on 5‐nm nanoparticles for all ligands, so that surface energies of the ligand shell should be similar and should not account for the differences in partition ratios for the various ligands. Through solubility effects, the DDT/TerPh system exemplifies how the exchange ability scale developed herein (Figure b) applies for a given solvent, here chloroform.…”

“…In both cases, the main difficulty is to control the final composition of the ligand shell. In order to understand, control, and predict the properties of such very common, yet complex, hybrid nanoparticles made of an inorganic core and a bicomponent organic corona, the composition of the shell must be assessed. Various methods can unveil the composition of biligand shells, such as mass spectrometries, electron paramagnetic resonance, fluorescence, and surface enhanced Raman spectroscopies .…”

Optical Properties of Hybrid Organic‐Inorganic Materials and their Applications

“…[392,397,403,406, D. Portehault and co-workers demonstrated recently the impact of the ligand (aromatic thiolates)-to-gold particle charge transfer on the plasmon resonance position using an original approach by spectroscopic ellipsometry. [435] In the field of optics, these nanoobjects provide, under light excitation, a way to strongly affect the optical responses of optical systems in close interaction with the metallic surfaces (such as dyes or semiconductors). The control of these interactions in hybrid systems has been an important field of scientific contributions for the past ten years.…”

Evolution of the Ligand Shell Morphology during Ligand Exchange Reactions on Gold Nanoparticles

“…Thep lots of BPT coverage versus time are presented in Figure 2. As expected, [26] the increase of BPT concentration (from 10 to 50 fold) leads to alarger fraction of BPT on the particles (from 35 %t o5 5%)a fter LER. The kinetic curves were fitted with the same second-order diffusion-limited Langmuir model (fitting parameters listed in Table S2).…”