A versatile method for surface functionalization and hydrophobization of gold nanoparticles

• Published in: Applied surface science Vol. 546; p. 148932
• Main Authors: Ishida, Takuya, Yanaga, Yohei, Yamada, Sunao, Takahashi, Yukina
• Format: Journal Article
• Language: English
• Published: Elsevier B.V 30.04.2021
• Subjects: Enhanced photoluminescence; Functionalized Au nanoparticle; Langmuir–Blodgett method; Localized surface plasmon resonance; Surface-enhanced Raman scattering; Enhanced photoluminescence; Surface-enhanced Raman scattering; Localized surface plasmon resonance; Functionalized Au nanoparticle; Langmuir–Blodgett method
• ISSN: 0169-4332; 1873-5584
• DOI: 10.1016/j.apsusc.2021.148932

[Display omitted] •Large Au nanoparticles (AuNPs) were hydrophobidized and functionalized stably in a low-polar solvent.•Thin films of the AuNPs were obtained by Langmuir–Blodgett method.•The AuNPs showed surface-enhanced Raman scattering and enhanced photoluminescence. A convenient, one-step, approach for surface modification with hydrophobic thiol or its dye-derivative of hydrophilic citrate-capped Au nanoparticles (Cit–AuNPs) is demonstrated. This method depended on the solubility of both Cit–AuNP and thiol or its derivative in the reaction solvent. We investigated a variety of solvents for Cit–AuNPs with 15–75 nm sizes and a capping molecule, octadecanethiol (ODT) or a disulfide derivative of hydrophobic porphyrin (PC10S)2. As to ODT, surface immobilization of Cit–AuNPs with ODT was successful in 2-propanol, while N,N-dimethylformamide was best in the case of (PC10S)2. In both cases, surface modified AuNPs were redispersible even after storing under dried powder conditions. Two-dimensional monoparticle films of surface-modified AuNPs by the Langmuir–Blodgett method with ethylene glycol as subphase could be formed and exhibit surface-enhanced Raman scattering. Spectra from the porphyrin skeleton were certainly observed, with the maximum photoluminescence enhancement of 15-fold, around 50-nm size. As to AuNP with 17-nm diameter, mixed monolayer assemblies of (PC10S)2 and octanethiol with different concentration ratios were fabricated and spectroscopic enhancement effects due to localized surface plasmon resonance were investigated.