Ligand Control over the Electronic Properties within the Metallic Core of Gold Nanoparticles

Abstract

The behavior of electrons within the metallic core of gold nanoparticles (AuNPs) can be controlled by the nature of the surface chemistry of the AuNPs. Specifically, the conduction electron spin resonance (CESR) spectra of AuNPs of diameter 1.8-1.9 nm are sensitive to ligand exchange of hexanethiol for 4-bromothiophenol on the surface of the nanoparticle. Chemisorption of the aromatic ligand leads to a shift in the metallic electron's g-factor toward the value expected for pure gold systems, suggesting an increase in metallic character for the electrons within the gold core. Analysis by UV/Vis absorption spectroscopy reveals a concomitant bathochromic shift of the surface plasmon resonance band of the AuNP, indicating that other electronic properties of AuNPs are also affected by the ligand exchange. In total, our results demonstrate that the chemical nature of the ligand controls the valence band structure of AuNPs.

Ultrasmall noble metal nanoparticles: Breakthroughs and biomedical implications

“…The electronic properties of UNMNPs are also impacted by their surface chemistry. Even with the same ligand binding group such as thiolate, different tail groups (alkyl vs. aromatic)[166, 167] or alkane chain length[168] can modulate the electron density of metal cores through direct charge donation from the ligand to the metal and influence the electronic properties of UNMNPs, as determined by the UV/Vis absorption spectroscopy and conduction electron spin resonance spectroscopy.…”

Nanoparticle Characterization: What to Measure?

“…Nanomaterials are defined as materials that consist of nanoparticles of which at least 50% have one or more external dimensions between 1 and 100 nm . Their small dimensions do not only allow more surface functionality in a given volume, but also lead to physical properties that often differ from their bulk counterparts in many aspects, including electronic, optical, and magnetic features . Nanoparticles possess a much higher surface‐to‐mass ratio than bulk materials and, therefore, surface atoms and surface energy strongly contribute to the material properties, e.g., leading to reduced lattice constants and lower melting points .…”

AurOrGlass: ORMOSIL Sol‐Gel Glasses Functionalized with Gold Nanoparticles for Advanced Optical Applications

“…Similarly, changes in the Au nanoparticle surface chemistry result in changes in the position of the SPR, as shown for example by the slight red‐shift of the SPR upon ligand exchange for alkanethiolate‐protected Au NPs (Figure ) …”

“…Similarly, changes in the Au nanoparticle surface chemistry result in changes in the position of the SPR, as shown for example by the slight red-shift of the SPR upon ligand exchange for alkanethiolate-protected Au NPs (Figure 3). [23] In brief, we emphasize in this study, by adding to the ligand control over the electronic properties of Au NPs, the possibility to broadly tune the composition of the organically modified glass also thanks to the presence of a co-dopant, the AurOrGlass class of NLO materials are likely to find practical application in the numerous domains (optical communications, This has been shown in 2015 by Zheng and co-workers reporting a marked improvement of the optical limiting performance of ORMOSIL glasses co-doped with graphene oxide (GO) and Au NPs obtained through hydrolysis and polycondensation of TEOS, GPTMS, and APTES in 7:2:1 molar ratio. [24] Investigated via nanosecond open-aperture Z-scan technique at 532 nm, the significantly enhanced OL performance of GO/Au-doped ORMOSIL sol-gel glass at 532 nm was ascribed to SPR of the conduction electrons in the Au NPs on the surface of GO.…”