Abstract
In a variety of applications, functionalization of gold nanoparticles is needed to ensure adequate surface charge and hydrophobicity for their biodistribution, interparticle interactions, or self-organization. In the present paper, we provide an economic way for the synthesis of hydrophobized poly(ethylenimine) (PEI) capped gold nanoparticles at room temperature using sodium dodecyl sulfate (SDS). The approach is based on the controlled competition between the nucleation of gold nanophases within the PEI molecules and the SDS binding onto their amine groups. This can be achieved via utilizing the strongly irreversible nature of the association between the oppositely charged polymer and that of the surfactant molecules. Specifically, by varying the order and timing of SDS addition during the process of gold nanoassembly formation, the size distribution, the morphology, and the local hydrophobic environment of the produced Au-PEI/SDS nanohybrids can be tuned even at one composition of the system. The results may be further exploited for the preparation of noble metal nanoassemblies with controlled hydrophobicity and charge.
Highlights
The preparation and functionalization of gold nanoparticles (AuNPs) have initiated intensive research in the last two decades since they represent great potential in a variety of fields such as catalysis, optical, and spectroscopic devices as well as biomedical formulations and colorimetric sensors.[1−4] The various applications utilize a diversity of different gold nanosystems with specific requirements for the size, shape, stability, and hydrophobicity of these AuNPs
The application of the II method leads to a red shift of the surface plasmon resonance (SPR) peak; the peak becomes even wider alluding to the presence of large aggregates
We have shown that the PEI-assisted gold nanoparticle formation could be tuned at 25 °C via the controlled order and timing of sodium dodecyl sulfate (SDS) addition
Summary
The preparation and functionalization of gold nanoparticles (AuNPs) have initiated intensive research in the last two decades since they represent great potential in a variety of fields such as catalysis, optical, and spectroscopic devices as well as biomedical formulations and colorimetric sensors.[1−4] The various applications utilize a diversity of different gold nanosystems with specific requirements for the size, shape, stability, and hydrophobicity of these AuNPs. An important current requirement is related to green nanoparticle synthesis routes, i.e., excluding high temperature conditions as well as excessive usage of organic solvents and additives.[7]. Polyelectrolytes (PE) play a crucial role in the stabilization and applications of AuNPs via their controlled interactions with the preformed particles.[8−12] Among the different polyelectrolytes, polyamines offer a unique alternative for gold NP synthesis since they may simultaneously act as reducing, stabilizing, and capping agent as well. Branched polyethylenimines (PEI) are frequently utilized for gold NP synthesis due to their commercial availability, biocompatibility, and dendrimer-like structure.[13−18] Depending on the applied solvent and experimental conditions, either single gold NPs16,19 or supraparticles embedded in the PEI matrix may be formed.[17,20,21]
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