The research activities of Dr. Denis Boudreauat Université Laval and the Center for Optics, Photonics and Lasers (COPL) in Québec lie at the interface between optical sensor design, molecular electronic/vibrational spectroscopy, and luminescent and plasmonic nanomaterial synthesis for industrial, biological and environmental sensing applications.
Boudreau’s graduate students use Raman and surface-enhanced Raman spectroscopy, time-resolved and steady-state fluorescence and plasmon-enhanced fluorescence spectrometry, and darkfield/epifluorescence imaging on a daily basis.
One of the ways we use FERGIE is together with a custom-made conformal microscope to collect single-particle fluorescence and scattering data that is then correlated with electron microscopy data.
Dr. Denis Boudreau
The team’s FERGIE-facilitated research projects involve (1) surface-enhanced Raman spectrometry of metabolic biomarkers, (2) synthesis and characterization of plasmonic nanoparticles for biosensor design, and (3) optical waveguide-based optical probes for in vivo and in vitro biological sensing.
FERGIE in Action (Project 1)
Synthesis and Characterization of Plasmonic Nanoparticles for Biosensor Design
The research team of Dr. Boudreau deals in the synthesis of luminescent nanoparticles. These particles contain a plasmonic core coated with fluorophore-doped concentric dielectric layers. Fluorophores are generally sensitive to various chemical and physical stimuli. Since the core’s size and shape have a significant influence on luminescent behavior, the team used single-particle spectroscopy to ascertain design rules that will result in nanostructures with improved properties.
In concert with a customized confocal microscope, FERGIE is used for collecting single-particle fluorescence and scattering data, which is subsequently correlated with electron microscopy data. “The ease with which FERGIE can be coupled to an optical setup, either free-space or via optical fiber, makes this very easy,” noted Dr. Boudreau.
Figure 1 shows transmission electron microscopy images of [email protected]2 nanoparticles with varying silica coating thickness.
Figure 2 shows darkfield scattering spectra measured from single nanoparticles. As opposed to single particles (#1), larger particles or particle aggregates (#2–4) give rise to broader and red-shifted spectra.
Figure 3 is a photo of graduate student Adolfo Sepulvedes using the single-particle microspectroscopy instrument.
FERGIE in Action (Project 2)
Optical Waveguide-Based Optical Probes for In Vitro and In Vivo Biological Sensing
To image the evolution of key cell metabolites, species-selective nanoparticles are connected to microscope slides and allowed to come into contact with cell cultures. Likewise, to perform remote biological or chemical sensing, the same plasmonic nanomaterials are being grafted on the tip of customized optical fibers. Present applications include in vivo molecular sensing in model animals and process monitoring in water treatment plants.
“In time, this fiber sensor will integrate multichannel architectures and fluorescent sensing structures responsive to various microbial metabolites, making it a flexible tool for sensing the intestinal microbiome with unprecedented resolution,” explained graduate student Victor Azzi.
Figure 4 is a photo of graduate student Victor Azzi connecting a fiber sensor to the FERGIE spectrometer.
Figure 5 is a photo showing a fiber sensor being inserted in diluted murine feces samples. The high sensitivity and multichannel capability of the FERGIE system allow simultaneous capture of the light emitted from multiple species-selective molecular probes on the tip of the fiber.
We can switch FERGIE from the microscope to a microfluidic flow chamber to the connectorized fiber sensor in mere minutes. It’s a fantastic tool.
FERGIE in Action (Project 3)
Surface-Enhanced Raman Spectrometry of Metabolic Biomarkers
Dr. Boudreau’s team is working with other research teams on the development of methodologies based on surface-enhanced Raman spectrometry (SERS) and plasmonic nanomaterials for in situ detection and quantification of cell metabolic markers. Target applications include analyzing the acclimation of phytoplankton to variations in global climate (with Dr. C. Lovejoy, U. Laval, and J.F. Masson, U. Montreal) and also in vivo monitoring of cholic acid derivatives in the gut microbiota (O. Barbier, A. Marette, and R. Vallée, U. Laval).
Figure 6 shows scanning electron microphotography of gold nanostars.
Figure 7 is a LightField screenshot of a SERS spectrum of cholic acid on an Au nanostar-coated substrate.
Figure 8 is a photo of a laboratory-made confocal Raman microscope coupled to FERGIE via optical fiber and used for the identification of metabolic markers by SERS.
Figure 9 is a photo of graduate student Victor Azzi: “Using the wavelength and intensity calibration kit made specifically for FERGIE gives us confidence when comparing Raman data from day to day, and from substrate to substrate,” he observes.
This information has been sourced, reviewed and adapted from materials provided by Princeton Instruments.
For more information on this source, please visit Princeton Instruments.