Effect of amino, hydroxyl, and carboxyl terminal groups of alkyl chains of self‐assembled monolayers on the adsorption pattern of gold nanoparticles

Abstract

The adsorption pattern of gold nanoparticles (AuNPs) on functionalized self‐assembled monolayers (SAMs) produced on a Au(111) surface was characterized. The Au(111) was modified with 11‐amino‐1‐undecanethiol hydrochloride (AUT), 11‐mercapto‐1‐undecanol (MUT), or 11‐mercaptoundecanoic acid (MUA) at an elevated temperature and pressure. The AuNPs aggregated on the AUT‐SAM surface, whereas they were well dispersed on the MUT‐SAM surface and localized on the MUA‐SAM surface. The results suggest that interactions between AuNPs differ according to the degree of peeling of citrate‐layer‐capped AuNPs. The degree of peeling, which is related to both the surface randomness of the SAMs and the functional characteristics of the terminal group of each SAM, was discussed on the basis of scanning tunneling microscopy observations, X‐ray photoelectron spectroscopic analyses, and contact angle measurements. Our study shows that AuNP patterns can be controlled by changing the terminal group of the alkyl thiol SAM on a Au(111) surface.

Probing Energy-Level Alignment in Molecular Multilayers by Frequency-Modulation Electrostatic Force Microscopy under Tapping-Mode-Combined Fowler–Nordheim Tunneling Spectroscopy

“…Figure d shows XPS N 1s spectra for the 6-AHT/Au and 11-AUT/Au films, where the intensities are normalized with respect to the Au 4f peak. The N 1s peak consists of two components; the peaks located at 399.8 and 401.9 eV for 6-AHT, and those located at 399.5 and 401.5 eV for 11-AUT, which can be assigned to NH 2 and NH 3 + , respectively. − It should be noted that the spectral weight of NH 2 /NH 3 + is 0.45:0.55 for 6-AHT/Au and 0.50:0.50 for 11-AUT/Au. These differences between 6-AHT and 11-AUT are attributed to the difference in their acidity constants, p K a .…”

“…A comparison of the N 1s signal intensities revealed the coverage of 11-AUT on Au(111) is 0.9 times lower than that for 6-AHT. The coverage of 11-AUT is 0.5 based on previous reports, while the coverage of 6-AHT is 0.55 according to the XPS N 1s spectra. This is in contrast to the alkanethiol SAM, where the longer alkyl chains are stabilized more tightly by the zig-zag interaction of the alkyl chains .…”

How to Use Localized Surface Plasmon for Monitoring the Adsorption of Thiol Molecules on Gold Nanoparticles?

“…The colloidal stability of citrate-AuNPs in water is ensured by the presence of charged citrate at the surface [50]. The preservation of colloidal stability by the progressive exchange of negatively charged citrate with MUDA or MHDA is possible thanks to the deprotonation of MUDA and MHDA molecules (pKa ≈ 5) in basic media (pH > 10).…”

Electromagnetically Stimuli-Responsive Nanoparticles-Based Systems for Biomedical Applications: Recent Advances and Future Perspectives

“…NIR radiation in a range of 650–1350 nm can penetrate safely in depth in human tissue [ 107 ]. This is interesting because it means that by suitably choosing the NP size and type of surface functionalization, it is possible to enhance and control the heat generated in the tissue that causes hyperthermia [ 108 ]. To obtain the LSPR in the NIR region, nanoshells are often produced with a core of SiO 2 and the outer layer of Au.…”

“…However, to enhance their compatibility with biological molecules and to use the NPs as drug carriers, they often need to be functionalized. Sulfur has a strong affinity to gold, and for this reason, thiols are often used to functionalize the Au-NP surface, which organizes themselves regularly on the NP surface, forming a self-assembled monolayer (SAM) [ 108 , 114 ]. The choice of the thiol is very important.…”