Multi-resonant Raman Sensors in liquids


Funded by: Ministero dell’Università e della Ricerca  
Calls: PRIN 2022
Start date: 2023-09-28  End date: 2025-09-27
Total Budget: EUR 286.874,00  INO share of the total budget: EUR 149.077,00
Scientific manager:    and for INO is: Gagliardi Gianluca

Organization/Institution/Company main assignee: CNR – Istituto Nazionale di Ottica (INO)

other Organization/Institution/Company involved:
Università di Napoli “Federico II”

other INO’s people involved:

Abstract: Dielectric micro-resonators made from solid glasses with different geometries, such as spheres or toroids, have proven amazing devices for high sensitivity bio-chemical sensing. They exploit a strong enhancement of light-matter interaction due to light trapping by whispering-gallery mode (WGM) resonances. On the other hand, Surface-Enhanced Raman Spectroscopy (SERS) is a formidable methodology that combines the fingerprint information of the molecular Raman spectrum with the optical near-field amplification of localized surface-plasmon resonances (LSPRs) on metallic nanostructures, enabling detection of diverse compounds also in liquid matrices with unprecedented sensitivity and selectivity.
In this project, we bridge spectroscopy with photonics to devise ultra-sensitive Raman probes for analysis of chemical species of environmental interest capable to operate directly in the liquid phase in a compact setting. The sensitive elements consist of home-made silica optical microspheres whose surface is functionalized with metallic nanoparticles using chemical immobilization techniques or metallic films nanostructured by solid-state dewetting. Real-time sensing of liquid-dissolved analytes can be performed with free-space excitation of WGMs in plasmon-assisted microresonators immersed in the liquid sample: we harness the giant sensitivity of LSPR-enhanced Raman scattering from nanostructures on a microsphere excited by WGMs to detect and identify trace chemical species, with ultra-low limit of detection.The killer application will be in the direct quantification of nano-plastics in water, a rare chemical pollutant of great concern in natural reservoirs whose detection is currently unfeasible with conventional analytical techniques. We will show that this unique photonic-plasmonic resonant platform is ideally suited to exploit the potentialities of microresonators and metallic nanostructures while it opens new pathways towards disruptive sensing applications, ranging from quality control of freshwater reservoirs and monitoring of marine pollution to quantification of food contaminants and direct detection of biomarkers in biological fluids.

The Scientific Results:
1) Automatic Alignment Method for Controlled Free-Space Excitation of Whispering-Gallery Resonances