Nanocrystalline TiO2 Sensitive Layer for Plasmonic Hydrogen Sensing.

Enrico Gazzola,Laura Brigo,Alessandro Martucci,Massimo Guglielmi,Marco Angiola,Filippo Romanato,Michela Cittadini

doi:10.3390/nano10081490

Abstract

Solution processed TiO2 anatase film was used as sensitive layer for H2 detection for two plasmonic sensor configurations: A grating-coupled surface plasmon resonance sensor and a localized surface plasmon resonance sensor with gold nanoparticles. The main purpose of this paper is to elucidate the different H2 response observed for the two types of sensors which can be explained considering the hydrogen dissociation taking place on TiO2 at high temperature and the photocatalytic activity of the gold nanoparticles.

Highlights

Plasmonic gas sensors are optical sensors that exploit either propagating or localized surface plasmons to transduce an analyte concentration into an optical signal
Since surface plasmon polariton (SPP) are extremely sensitive to changes in the optical properties of the surrounding materials, they can be exploited for developing high-performance sensing devices called Surface Plasmon Resonance sensors (SPR sensors) [1,2]
The spectral position of the localized surface plasmon resonance (LSPR) of Au NPs immersed in a metal oxide supporting matrix is sensitive to both electrons exchange at the gold/matrix interface as well as the permittivity variations of the matrix; both of these effects have been exploited for developing hydrogen and carbon monoxide optical gas sensors [12,13,14]

Summary

Introduction

Plasmonic gas sensors are optical sensors that exploit either propagating or localized surface plasmons to transduce an analyte concentration into an optical signal. Buso et al and Della Gaspera et al concluded that LSPR changes from H2 reduction of TiO2-Au films at high temperature (above 250 ◦C) and of TiO2-Au-Pt films at room temperature are induced by charge transfer to the Au NPs [12,20] This conclusion was supported by the work of Carpenter et al, where the LSPR shifts of Au NPs dispersed in an yttrium-stabilized-zirconia matrix was attributed to the same H2 interaction mechanism [21]. Scope of the present study is to elucidate the interaction mechanisms of H2 with the TiO2 sensitive layer which induce different responses for the two kinds of plasmonic sensors For both sensors, we discuss the origin of the observed shift of the plasmonic resonances, which cannot be explained considering only the variation of the refractive index induced by the target gas filling the pore of the sensitive matrix. Sensors with SiO2 in place of TiO2 or without any oxide layer were tested for comparison

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Conclusion