Local plasmon sensor with gold colloid monolayers deposited upon glass substrates

Area of Science:

• Nanotechnology
• Optical Sensing
• Materials Science

Background:

• Local plasmon resonance (LPR) in gold nanoparticles exhibits spectral shifts dependent on the surrounding medium's refractive index.
• This phenomenon is foundational for developing sensitive optical detection methods.

Purpose of the Study:

• To propose and characterize a new optical sensor based on LPR in gold colloid monolayers.
• To investigate the sensor's response to changes in refractive index for liquid samples and thin films.

Main Methods:

• Fabrication of gold colloid monolayers with controlled nanoparticle size (13.9-nm and 20.2-nm) on glass slides.
• Measurement of absorption spectra of the monolayers when immersed in liquids or coated with thin films.
• Analysis of the relationship between LPR peak characteristics (wavelength, absorbance) and refractive index/film thickness.

Main Results:

• A distinct LPR peak was observed in the visible absorption spectra of gold colloid monolayers.
• Both resonance wavelength and absorbance increased with rising refractive indices of sample liquids and increasing thin film thickness.
• Proportional constants relating resonance wavelength shift to film thickness were determined (3.6 and 5.7 for different nanoparticle sizes).

Conclusions:

• Gold colloid monolayers effectively function as optical sensors leveraging LPR.
• The sensor demonstrates sensitivity to refractive index variations, suitable for detecting liquid properties and film thicknesses.
• The observed proportional constants provide quantitative data for sensor calibration and application development.