Sol-Gel Thin Films for Plasmonic Gas Sensors.

Enrico Gaspera,Alessandro Martucci

doi:10.3390/s150716910

Enrico Gaspera, Alessandro Martucci

Open Access

https://doi.org/10.3390/s150716910

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Abstract

Plasmonic gas sensors are optical sensors that use localized surface plasmons or extended surface plasmons as transducing platform. Surface plasmons are very sensitive to dielectric variations of the environment or to electron exchange, and these effects have been exploited for the realization of sensitive gas sensors. In this paper, we review our research work of the last few years on the synthesis and the gas sensing properties of sol-gel based nanomaterials for plasmonic sensors.

Highlights

Dangerous gas detection has become in the last years a challenging task for several applications, first of all in the safety of working and living environments: toxic gases like carbon monoxide (CO) or volatile organic compounds (VOCs) like formaldehyde are commonly found in these locations, the former coming from insufficient oxygen content in the combustion of coal or gases for heating devices, the latter coming from indoor furniture, because it is commonly used in combination with urea, melamine or phenol to obtain thermosetting resins which are used in coatings, adhesives and foams
We initially developed a sol-gel protocol that enables the dispersion of functional oxide nanocrystals within a porous silica films at high concentration without any aggregation or segregation phenomena that would be detrimental for the optical quality of the nanocomposites
Colloidal NPs in ethanol/DMSO using tetramethylammonium hydroxide as a base/catalyst. Such NPs can be purified and concentrated in ethanol and eventually mixed with an ethanolic solution of PVP-capped Au NPs. The beauty of this approach is the possibility to independently synthesize and tune the properties of the prepared colloids: for example, we studied the effect of the doping of ZnO

Summary

Introduction

Dangerous gas detection has become in the last years a challenging task for several applications, first of all in the safety of working and living environments: toxic gases like CO or volatile organic compounds (VOCs) like formaldehyde are commonly found in these locations, the former coming from insufficient oxygen content in the combustion of coal or gases for heating devices, the latter coming from indoor furniture, because it is commonly used in combination with urea, melamine or phenol to obtain thermosetting resins which are used in coatings, adhesives and foams. Sensors based on propagating plasmons are intrinsically non-selective, because every analyte that can cause a variation in the electric-dielectric properties at the interface with the metal layer is, in principle, capable of altering the plasmon propagation so the specificity of these sensors is usually achieved by modifying the metal surface with a functional layer to allow specific interaction with the target analyte This strategy has been successfully applied for chemosensors and extensive reviewson the topic have been published [29,30], highlighting the possible different configurations of SPR sensors, including the attractive implementation within optical fibers. It is important to underline that, in the case of reagent-mediated optical sensors, very often the sensitive material is a thin film (such as a polymer or a metal oxide), which reacts with the target gas and the changes in its properties (chemical, electrical, etc.) are monitored using plasmonic probes, either looking at the LSPR of metal NPs or analyzing the variation in propagating plasmons at the interface of metal film-dielectric. The first part is focused on sol-gel gas sensors based on localized surface plasmons and the second on extended surface plasmons

Sol-Gel Nanomaterials for Optical Sensors Based on Localized Plasmons

In SituFormation of Plasmonic Nanoparticles

ExSituFabrication of Plasmonic Nanoparticles

Sol-Gel Nanomaterials for Optical Sensors Based on Extended Plasmons

Findings

Conclusions