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The Role of the Polyethylene Glycol in the Organization of Gold Nanorods at the Air–Water and Air–Solid Interfaces

Summary

Scientists studied how to arrange tiny gold rod-shaped particles in organized patterns. By coating these particles with different lengths of a plastic-like material called polyethylene glycol, they found they could control how the particles stack and arrange themselves. The longer the coating, the more different arrangements were possible. This discovery could help create better materials for detecting specific molecules and improving various technological applications.

Background

Gold nanorods (Au-NRs) exhibit excellent physical, chemical, and biological properties due to localized surface plasmon resonance. Functionalization with thiol-terminated polyethylene glycol (PEG) enhances stability and biocompatibility, enabling formation of stable monolayers at air-water interfaces for assembly into organized films.

Objective

To investigate how different molecular weights of polyethylene glycol affect the organization and arrangement of gold nanorods at air-water and air-solid interfaces, and to understand the relationship between PEG chain conformation and nanoparticle assembly structure.

Results

PEG molecular weight significantly influenced monolayer structure and stability. PEG-2k formed liquid condensed films while PEG-5k and PEG-10k formed liquid expanded films. Higher molecular weight PEGs required additional CTAB stabilizer to form stable monolayers. Conformational changes in PEG chains induced nanorod aggregation with different structural patterns depending on transfer pressure and PEG type.

Conclusion

The arrangement of gold nanorod assemblies can be tailored using polyethylene glycol of varying molecular weights and appropriate stabilizers. PEG conformation, controlled by chain length and grafting density, determines whether monomeric or aggregated structures form at interfaces, with potential applications in optical sensing and surface-enhanced spectroscopy.
  • Published in:Langmuir,
  • Study Type:Experimental Research,
  • Source: PMID: 38961723, DOI: 10.1021/acs.langmuir.4c01427
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