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. 2022 Dec 3;12(23):4297.
doi: 10.3390/nano12234297.

Surface Enhancement Using Black Coatings for Sensor Applications

Martin Hruška  1 , Joris More-Chevalier  1   2 , Přemysl Fitl  1   2 , Michal Novotný  1   2 , Petr Hruška  2   3 , Dejan Prokop  2   3 , Petr Pokorný  2 , Jan Kejzlar  1   2 , Virginie Gadenne  4 , Lionel Patrone  4 , Martin Vrňata  1 , Jan Lančok  1   2
Affiliations

Surface Enhancement Using Black Coatings for Sensor Applications

Martin Hruška et al. Nanomaterials (Basel). .

Abstract

The resolution of a quartz crystal microbalance (QCM) is particularly crucial for gas sensor applications where low concentrations are detected. This resolution can be improved by increasing the effective surface of QCM electrodes and, thereby, enhancing their sensitivity. For this purpose, various researchers have investigated the use of micro-structured materials with promising results. Herein, we propose the use of easy-to-manufacture metal blacks that are highly structured even on a nanoscale level and thus provide more bonding sites for gas analytes. Two different black metals with thicknesses of 280 nm, black aluminum (B-Al) and black gold (B-Au), were deposited onto the sensor surface to improve the sensitivity following the Sauerbrey equation. Both layers present a high surface roughness due to their cauliflower morphology structure. A high response (i.e., resonant frequency shift) of these QCM sensors coated with a black metal layer was obtained. Two gaseous analytes, H2O vapor and EtOH vapor, at different concentrations, are tested, and a distinct improvement of sensitivity is observed for the QCM sensors coated with a black metal layer compared to the blank ones, without strong side effects on resonance frequency stability or mechanical quality factor. An approximately 10 times higher sensitivity to EtOH gas is reported for the QCM coated with a black gold layer compared to the blank QCM sensor.

Keywords: QCM sensors; black aluminium; black gold; evaporation depositions; nanostructured materials; sensor applications; sputtering depositions.

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Conflict of interest statement

The authors declare no conflict of interest.

Figures

Figure 1
Figure 1
Scheme of the measurement apparatus.
Figure 2
Figure 2
SEM images of black aluminum (B-Al) (a) 100 kx, (b) 500 kx, and black gold (B-Au) (c) 100 kx, (d) 500 kx.
Figure 3
Figure 3
SEM images of the B-Al layer (a,c) and the B-Au layer (b,d) deposited on QCM sensors. (c) Cross section of B-Al layer and (b) cross-section of the B-Au layer.
Figure 4
Figure 4
AFM pictures of B-Al surface layer in (a) and B-Au surface layer in (b) deposited on QCM sensors.
Figure 5
Figure 5
Impedance spectrum of QCM sensors before and after coating with B-Al layer in (a) and before and after coating with B-Au layer (b).
Figure 6
Figure 6
Response of QCM sensors with and without BMs coatings as a function of the concentration of H2O vapor in (a) and as a function of the concentration of EtOH vapor in (b).
Figure 7
Figure 7
Calibration curves and sensor sensitivity factors from sensor responses to H2O in (a) and towards vapors of EtOH in (b).
See this image and copyright information in PMC

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