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Multimodal Detection of Low Water Contents in Ethanol Using a Plasmon-Berreman-Enhanced Metasurface Infrared Absorber
Jhuma Pan1, Sachin Kumar Srivastava1,2
1Department of Physics, Indian Institute of Technology Roorkee, Roorkee, Haridwar, Uttarakhand 247667, India.
ACS Sensors
|June 30, 2026
Summary
A novel dual-mode metasurface absorber enhances infrared signals for detecting water impurities in ethanol. This advanced sensing technology offers high sensitivity and selectivity for quality assurance in industries.
Area of Science:
- Nanophotonics and Metasurface Technology
- Infrared Spectroscopy and Sensing
- Chemical Analysis and Material Science
Background:
- Molecular vibrational spectroscopy is crucial for chemical analysis.
- Enhancing weak signals in the infrared fingerprint region is challenging.
- Metasurface absorbers offer potential for signal enhancement through plasmon-phonon coupling.
Purpose of the Study:
- To design and demonstrate a dual-mode metasurface absorber (MSA) for enhanced infrared (IR) detection.
- To utilize the MSA for sensitive detection and quantification of water impurity in ethanol.
- To explore the capabilities of plasmon and phonon-enhanced IR absorption (SEIRA and BEIRA) for label-free sensing.
Main Methods:
- Fabrication of a periodic metasurface absorber with dual resonance modes.
- Utilizing plasmonic and Berreman (BE) modes for enhanced IR absorption.
- Investigating the plasmonic shift and thermal contrast for water quantification in ethanol.
- Evaluating selectivity against common impurities like methanol, acetone, and acetaldehyde.
Main Results:
- The MSA achieved 80% and 99.5% absorbance in the near-IR and long-wavelength IR regions, respectively.
- Successful enhancement of water's -OH bands and ethanol's C-O peak via SEIRA and BEIRA.
- Quantification of low water content (up to 1%) with a limit of detection (LOD) of 1.14 (% v/v) and high sensitivity.
- BEIRA demonstrated an LOD of 0.31 (% v/v) for water in ethanol with concentration-dependent thermal contrast.
Conclusions:
- The dual-mode MSA enables label-free visual quantification of water in ethanol with high sensitivity and selectivity.
- This multimodal sensing strategy overcomes limitations of conventional IR spectroscopy for ultra-low quantity detection.
- The developed metasurface chip offers a versatile platform for chemical analysis, process monitoring, and quality assurance.
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