Surface Enhancement Using Black Coatings for Sensor Applications

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.

Assessing Impedance Analyzer Data Quality by Fractional Order Calculus: A QCM Sensor Case Study

“…Given the use of the QCM sensor in different working media, it can be argued that the fractional order BVD model approach is justified for impedance spectroscopy as a measure of the degree of VIA compensation [46,[59][60][61]. Determining the correct value for the electrical parameters of the BVD model allows the calculation of the fractional order parameter of motional inductance and motional capacitance for an uncompensated VIA.…”

Microstructure and physical properties of black-aluminum antireflective films

“…2,3 The collected light comes from a volume much larger than its physical size, which occurs in localized surface plasmon resonance in multiple wavebands. The photons trapped on the surface transfer their energy into electric and/or thermal energy, allowing for various applications in solar energy harvesting, optical sensing, imaging, electrochemical sensing, [4][5][6][7][8][9] antire-ection, camouage, and cloaking. [10][11][12][13] BMs have been prepared by magnetron sputtering, 14-17 thermal evaporation, 4,18-22 electrodeposition, 6,7 deposition on a dielectric substrate with imprinted moth-eye-like nanostructures, 5 and by laser surface treatment.…”

“…7 Black or colored coating has been obtained using metals such as gold, platinum, tungsten, copper, titanium, palladium, or aluminum. 15,22,24,[27][28][29][30][31][32] Recently, black metals have been utilized to improve the sensitivity of quartz crystal microbalance sensors for gas detection, 9 and a black aluminum coating was used for converting light into electrical current by pyroelectric effect. 8 Aluminum is a promising metal for fabricating black metal coatings due to its good adhesion and its low cost, which makes it promising for industrial use.…”

“…2,3 The collected light comes from a volume much larger than its physical size, which occurs in localized surface plasmon resonance in multiple wavebands. The photons trapped on the surface transfer their energy into electric and/or thermal energy, allowing for various applications in solar energy harvesting, optical sensing, imaging, electrochemical sensing, 4–9 antireflection, camouflage, and cloaking. 10–13…”

Spurious Resonance of the QCM Sensor: Load Analysis Based on Impedance Spectroscopy

“…Quartz crystal microbalance (QCM) has a successful application in the field of label-free sensors known as a QCM sensor [ 11 , 12 , 13 , 14 ]. The electrical properties of the QCM sensor as a function of frequency can be described in the vicinity of the resonance frequency by an equivalent circuit known as the Butterworth-Van Dyke (BVD) model [ 15 , 16 ].…”