Gold nanoparticle silica nanopeapods

Area of Science:

• Nanotechnology
• Materials Science
• Biomedical Engineering

Background:

• Gold nanoparticles (AuNPs) are crucial for plasmonic applications, but their aggregation and instability limit performance.
• Surface-enhanced Raman scattering (SERS) offers high sensitivity for molecular detection.
• Protecting nanostructures is vital for maintaining their functionality in complex environments like biological systems.

Purpose of the Study:

• To fabricate subnanometer gap-separated linear chain gold nanoparticle (AuNP) silica nanotube peapods (SNTPs).
• To investigate the self-assembly and geometrical control of AuNPs within silica nanotubes (SNTs).
• To demonstrate the potential of SNTPs as robust intracellular optical pH sensors with enhanced SERS capabilities.

Main Methods:

• Fabrication of AuNP-loaded SNTs via self-assembly using capillary force and a wet-dry process.
• Characterization using Transmission Electron Microscopy (TEM) to confirm nanogap formation.
• Finite-Dimension Time-Domain (FDTD) calculations for electric field enhancement estimation.
• Surface-enhanced Raman scattering (SERS) measurements using p-mercaptobenzoic acid (p-MBA) as a probe molecule.

Main Results:

• Successfully fabricated linear chain AuNP structures within SNTs with sub-1-nm nanogap junctions.
• Demonstrated control over AuNP arrangement (single-line or double-line) by tuning nanoparticle and nanotube dimensions.
• Achieved superior SERS spectra in vivo due to sustained nanogaps protected by the silica wall.
• Confirmed preservation of nanogaps within cellular environments after endocytosis.

Conclusions:

• SNTPs provide a robust platform for creating stable, subnanometer gap-separated AuNP structures.
• The silica encapsulation protects the nanogaps, leading to enhanced and stable SERS signals.
• SNTPs show significant promise for developing sensitive and reliable intracellular optical pH sensors.