Nanostructured surfaces for bio- and chemical sensors
There is currently a large interest to transfer fundamental research results to technological advances in sensors able to detect specific chemical or biological species. An obvious advantage of using nanostructures as active layers is to increase the surface available for analyte interaction. Photonic crystals, in particular three dimensional ones like opals and inverse opals, fulfil this goal since they posses a porous mesostructure. However, they provide more significant advantages related to the redistribution of the density of photonic states and other interesting properties for sensing, namely light localization effects and photoluminescence enhancement. Moreover, the possibility of localizing and enhancing light field by coupling with Surface Plasmons in metallic nanostructures has been recently explored and demonstrated.
Two research projects of our group are focussed on this kind of subjects.
Photonic enhancement in Chemical Sensors
The goal of the project is the proof of concept for a new compact, fast and low cost optical gas sensor. The sensing mechanism will be based on the variation (quenching, enhancement) of the fluorescence emission of the chemoreceptor upon chemical or physical interaction with the analyte to be monitored. Possibly, changes in reflectance will be also considered. In this project the sensing action will take place upon inclusion of the chemoreceptor in a photonic structure, where a positive perturbation of the fluorescence emission will be induced and effectively exploited during the analyte detection, which in turn could also modify the refractive index. The research work consists in I) theoretical modelling and engineering of the photonic crystals (to be prepared by a partner in Genoa); ii) investigation of the optics and photophysics of conjugated materials used as a receptor; iii) study of optics, enhancement effects and sensing properties of photonic crystal transducers.
Label free detection systems based on the Surface Plasmon Resonance
The project is focused on the development of a portable and integrated system dedicated to the multiplexed, real-time monitoring of bio agents or proteins with bio-medical or environment interest. The core technology is a Surface Plasmon Resonance Imaging (SPRi) system, based on a joint patent of the University of Pavia and the Joint Research Centre (JRC, Bioscience Unit) of the European Commission in Ispra. Such collective efforts aim at overcoming the usual SPRi limitations related to the binding events detection sensitivity using two innovative approaches (part of the mentioned patent):
- The nanostructuration of the chip surface in adhesive/non-adhesive highly organised nanoareas in order to control the interaction between proteins and surface to maximise the bio-recognition performances, and
- The nanostructration of the surface for fine tuning of the optical properties of the chip in order to generate plasmonic enhancement of the signal. To obtain this, a study of the dependence of the optical response on the structural parameters and of the interaction with plasmonic resonances is being performed.
F. Marabelli, D. Comoretto, L. Fornasari, S. Giudicatti, T. Losco, V. Morandi, M.C. Ungureanu, A. Valsesia
Fondazione Cariplo 2009-2011 "PHOtonic ENhancement In Chemical Sensors: nanomaterials for optics"
A. Valsesia, "Fabrication of nanostructured surfaces for the development of advanced Biointerfaces" (University of Pavia, 2007)
Plasmonic resonances in nanostructured gold/polymer surfaces by colloidal lithography,
S. Giudicatti, A. Valsesia, F. Marabelli, P. Colpo, and F. Rossi,
Amplified spontaneous emission from opal photonic crystals engineered with structural defects,
F. Di Stasio, L. Berti, M. Burger, F. Marabelli, S. Gardin, T. Dainese, R. Signorini, R. Bozio, and D. Comoretto,