Enhancing the Sensitivity of Nanoplasmonic Thin Films for Ethanol Vapor Detection

Abstract

Nanoplasmonic thin films, composed of noble metal nanoparticles (gold) embedded in an oxide matrix, have been a subject of considerable interest for Localized Surface Plasmon Resonance (LSPR) sensing. Ethanol is one of the promising materials for fuel cells, and there is an urgent need of a new generation of safe optical sensors for its detection. In this work, we propose the development of sensitive plasmonic platforms to detect molecular analytes (ethanol) through changes of the LSPR band. The thin films were deposited by sputtering followed by a heat treatment to promote the growth of the gold nanoparticles. To enhance the sensitivity of the thin films and the signal-to-noise ratio (SNR) of the transmittance–LSPR sensing system, physical plasma etching was used, resulting in a six-fold increase of the exposed gold nanoparticle area. The transmittance signal at the LSPR peak position increased nine-fold after plasma treatment, and the quality of the signal increased six times (SNR up to 16.5). The optimized thin films seem to be promising candidates to be used for ethanol vapor detection. This conclusion is based not only on the current sensitivity response but also on its enhancement resulting from the optimization routines of thin films’ architectures, which are still under investigation.

Gas Sensors Based on Localized Surface Plasmon Resonances: Synthesis of Oxide Films with Embedded Metal Nanoparticles, Theory and Simulation, and Sensitivity Enhancement Strategies

“…Yet, since the size distribution that can be obtained are in the range up to 40 nm, and the nanoparticles are mostly spherical, this might hinder the signal and sensitivity of the plasmonic sensor. On the other hand, this effect can be mitigated, for example, (i) by partially exposing the nanoparticles that are initially embedded in the matrix, using low vacuum plasma etching [166][167][168][169], or (ii) by developing nanostructured thin films deposited by glancing angle deposition (GLAD) [170,171], which may allow for increasing the availability of adsorption sites for analyte molecules and to produce nanoparticles with higher aspect ratios, and thus to be more sensitive [172,173].…”

“…If the thermal treatment and the working temperature do not exceed 450 • C [168], one may consider an inexpensive substrate, such as glass. This type of substrate may increase the final cost by 3% to 5%, which is a marginal difference.…”

NANOPTICS: In-depth analysis of NANomaterials for OPTICal localized surface plasmon resonance Sensing

“…Monitoring the LSPR band in the transmittance spectra can be done by observing different quantities in the optical absorbance and transmittance spectra. For example: (i) the wavelength of the transmittance minimum of the LSPR band; (ii) the area below the spectrum, (iii) the OTC, and (iv) the absorbance or transmittance at different wavelengths [12][13][14][15][16][17][18].…”

Chitosan Micro-Membranes with Integrated Gold Nanoparticles as an LSPR-Based Sensing Platform

“…These parameters also significantly affect the performance of the biosensor. Nanocomposite thin films are attractive for LSPR since they allow (i) a homogeneous distribution of metallic NSTs in the form of metallic NPs, (ii) porous media for analyte diffusion, (iii) NPs 3D dispersion, and (iv) lower thickness for optimal optical detection with in-house built LSPR systems [ 14 , 15 , 16 ]. Several “host” matrices have been explored and reported for LSPR sensing, including metallic oxides and polymeric thin films.…”