Silver nanoparticle engineering via oligovaline organogels

Area of Science:

• Supramolecular Chemistry
• Materials Science
• Nanotechnology

Background:

• Oligopeptides are versatile building blocks for self-assembled soft materials.
• Previous studies have shown oligovaline peptides form ordered fibers and organogels.

Purpose of the Study:

• To investigate the gelation properties of l-Valine-based oligopeptides containing a cysteine residue.
• To explore the mineralization of these peptide-based organogels with silver nanoparticles.
• To understand how peptide composition influences silver nanoparticle formation.

Main Methods:

• Synthesis and characterization of Z-(l-Val)3-OMe and Z-(l-Val)2-l-Cys(S-Bzl)-OMe oligopeptides.
• Organogel formation studies in butanol.
• Transmission Electron Microscopy (TEM) for fiber and nanoparticle morphology.
• X-ray diffraction (XRD) for structural analysis.
• In-situ mineralization with silver nanoparticles using N,N-Dimethylformamide (DMF) as a reducing agent.

Main Results:

• Both Z-(l-Val)3-OMe and Z-(l-Val)2-l-Cys(S-Bzl)-OMe efficiently form stable organogels in butanol.
• The organogels consist of highly ordered peptide fibers with a β-sheet structure, similar to previously reported oligovaline gels.
• Mineralization with silver nanoparticles is achieved, with the sulfur-containing peptide fraction controlling nanoparticle size and shape (spherical, plate-like, raspberry-like).
• Complexation of silver ions to the sulfur atom of the thioether moiety is identified as the key interaction for controlling nanoparticle formation.

Conclusions:

• l-Valine-based oligopeptides, including those with cysteine, are effective gelators for butanol.
• The self-assembled peptide fibers serve as templates for controlled silver nanoparticle synthesis.
• The sulfur moiety in the peptide plays a crucial role in coordinating silver ions and directing nanoparticle morphology.