Title

Design and Synthesis of New Ligands for the Preparation of Amphiphilic Nanoparticles

Submitter Information

Sarah SalloumFollow

Type of Proposal

Oral presentation

Start Date

24-3-2015 1:00 PM

End Date

24-3-2015 1:50 PM

Faculty

Faculty of Science

Importance of the Project

Today, there is a growing for nano-sized objects due to the rapid growth of nanotechnological applications. As a result, organic ligand protected gold nanoparticles (AuNPs) have been extensively studied over the past years due to their potential applications in electronics, catalysis, drug delivery , optical probes and biotechnology.AuNPs tend to aggregate with each other to form larger clusters. By coating the surface of AuNPs with monolayers of organic ligands, that will provide chemical stability to prevent adjacent AuNPs from aggregating. These ligands can attach to the metal surface via polar covalent thiol-metal bonds and can provide functionalization to the AuNPs to generate unique surface properties depending on the functional terminal group of the protecting ligand.Ligands are known to be able to self-assemble on metal surfaces. Similarly, hydrophobic and hydrophilic thiolated ligands attached to AuNPs will self-organize to form an amphiphilic structure, also known as Janus nanoparticles, which behave as surfactant molecules. Amphiphilic NPs contain charged, polar head groups on one side and nonpolar, uncharged groups attached to opposite side of the NP.

Existing State of Knowledge

Research has shown that two dislike thiolatedmolecules on AuNPs, will self-separate into distinct domains on the metal surface due to their immiscibility.

There exist a few methods to generate janus nanoparticles, including masking and mixing. In the masking process, one portion of a nanoparticle surface is made inaccessible so that a chemical reaction, can be carried out exclusively on the other portion of the nanoparticle surface.

Chen’s group used a Langmuir-Blodgett technique to prepare gold Janus nanoparticles. They trapped a monolayer of hydrophobic octanethiolate protected gold nanocrystals at the air—water interface, and performed a ligand exchange reaction on the lower hemisphere that is in contact with the water that what injected with hydrophilic ligands

The drawback with this method is scalability it is difficult to generate larger quantities of amphiphilic nanoparticles

The generation of Janus nanoparticles through the competitive adsorption of a mixture of ligands has high potential knowledge in this area is still limited.

Vilain et al. prepared gold Janus nanoparticles obtained by using a mixture of two ligands with little affinity for each other, resulting in a phase separation on the surface of the nanoparticles at the liquid liquid interface

Research Question

The aim of my thesis is to synthesize new hydrophobic and hydrophilic ligands in preparation of a novel amphiphilic nanoparticle in a feasible and cost effective manner, and to examine their self-organizing properties.

Methodology

The hydrophilic and hydrophibic ligands are firstly synthesized and their terminal ends are thiolated in order to attach the ligands to the metal surface. The organic ligands are subjected to numerous purification steps such as extraction drying, recrystallization and column chromotography. Next, the purity of the ligands is evaluated by NMR and IR spectroscopy.

All nanoparticles will be characterized by UV-vis spectroscopy, thermal analysis, X-ray diffraction, and transmission electron microscopy to detect the formation of mixed ligand-shell NPs.

Your Findings

So far research had led to the preparation of spherical particles with isotropic properties which does not have a certain degree of order, thus that does not offer too many possibilities in terms of achievable structures. Therefore, scientists have begun to look for ways to produce anisotropic nanoparticles that can form superstructures. This can be done by coating the NP with liquid crystalline ligands

Thus, my long-term goal is the preparation of amphiphilic AuNPs capable of self-organizing into lyotropic mesophases such as lamellar, cubic and cylindrical structures.

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Mar 24th, 1:00 PM Mar 24th, 1:50 PM

Design and Synthesis of New Ligands for the Preparation of Amphiphilic Nanoparticles