Multiple-Sized Amphiphilic Janus Gold Nanoparticles by Ligand Exchange at Toluene/Water Interface

doi:10.1016/j.jmst.2016.06.024

Abstract

Abstract:

Amphiphilic Janus gold nanoparticles (GNPs) are prospected to encapsulate drug molecules in cancer therapy and to serve as heterogeneous catalysts at oil/water interfaces, where Janus GNPs with different sizes are required. In this work, multiple-sized precursor GNPs were synthesized by seeded growth method protected with tris(hydroxymethyl)phosphine oxide (THPO) ligand molecule, and a ligand exchange reaction with triphenylphosphine (PPh₃) at the toluene/water interface was employed to prepare amphiphilic Janus GNPs. UV-vis and transmission electron microscopy (TEM) analyses indicate that the as-prepared GNPs are nanocrystals with average diameters of 2.3?nm, 9.5?nm, 16.1?nm and 18.8?nm, respectively. Contact angle, Raman and X-ray photonic spectroscopy (XPS) analyses reveal that the self-assembled GNP films exhibit hydrophilic on one side and hydrophobic on another, owing to the adsorption of hydrophilic ligands (THPO and THP) and a similar amount of hydrophobic ligands (PPh₃ and PPh₃O). Angle-resolved XPS analysis further demonstrates that the individual GNPs actually possess hydrophilic and hydrophobic compartments on the surface, which regularly packed by supramolecular interactions at toluene/water interface to form the self-assembled GNP films.

Key words: Janus gold nanoparticles, Amphiphilic, Ligand exchange, Self-assembly

Luo Kun,Xiang Yongdong,Wang Haiming,Xiang Li,Luo Zhihong. Multiple-Sized Amphiphilic Janus Gold Nanoparticles by Ligand Exchange at Toluene/Water Interface[J]. J. Mater. Sci. Technol., 2016, 32(8): 733-737.

Figures/Tables 6

Fig. 1. UV-vis spectra of the as-synthesized colloids: (a) UV-vis absorbance of Colloid A, B, C, and D; (b) the effect of seeded growth of GNPs, curve 1 shows the absorbance with hydroxylamine hydrochloride as reducing agent in HAuCl4 solution, curve 2 is the absorbance with THPC, and curve 3 shows the reduction by hydroxylamine hydrochloride with addition of Colloid A. Inset: enlarged absorbance peak of curve 1.

Fig. 2. TEM images of GNPs obtained from Colloid A (a), Colloid B (b), Colloid C (c), and Colloid D (d).

Fig. 3. Contact angle of water on the hydrophilic (Side a) and hydrophobic surface (Side b) of films A, B, C, and D.

Fig. 4. Raman spectra of Colloid B and film B after ligand exchange.

Fig. 5. XPS spectra of Au 4f, C1s, and P 2p obtained from Colloid B (a, b, c) and self-assembled film B (d, e, f).

Fig. 6. In-depth distribution of O, C, Au, and P elements in the self-assembled film B.

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