Poly-L-lysine-coated silver nanoparticles as positively charged substrates for surface-enhanced Raman scattering.

Area of Science:

• Materials Science
• Nanotechnology
• Analytical Chemistry

Background:

• Surface-enhanced Raman scattering (SERS) requires suitable substrates for sensitive analyte detection.
• Developing stable, functionalized nanoparticles is crucial for advanced SERS applications.
• Controlling nanoparticle surface charge influences analyte interaction and detection sensitivity.

Purpose of the Study:

• To synthesize positively charged nanoparticles for SERS applications.
• To investigate the use of these nanoparticles for detecting the anionic chromophore bilirubin.
• To establish a quantitative SERS method for bilirubin detection.

Main Methods:

• Coating citrate-reduced silver nanoparticles with poly-l-lysine to create positively charged substrates.
• Characterization of nanoparticle size (75 nm) and zeta potential (+62.3 mV) using dynamic light scattering and UV-vis spectrophotometry.
• Application of the functionalized nanoparticles for SERS detection of bilirubin in aqueous solutions.

Main Results:

• Stable, non-aggregated 75 nm nanoparticles with a high positive zeta potential were successfully prepared.
• The positively charged nanoparticles effectively captured anionic bilirubin molecules via electrostatic interaction.
• A linear SERS intensity response to bilirubin concentration was observed in the nanomolar range (10-200 nM).

Conclusions:

• Positively charged poly-l-lysine coated silver nanoparticles are effective SERS substrates.
• This method allows for sensitive and quantitative detection of anionic analytes like bilirubin.
• The developed nanoparticles offer a promising platform for trace analysis in various fields.