<p>In this work, we investigate the detection of contaminants in water, including varying concentrations of sodium chloride (NaCl), using angular interrogation-based surface plasmon resonance (ASPR). The proposed sensor structure comprises a silver (Ag) thin film, a graphene/MXene heterostructure, and a sensing medium, integrated with a CaF<InlineEquation ID="IEq1"> <EquationSource Format="TEX">$_2$</EquationSource> <EquationSource Format="MATHML"><math> <mmultiscripts> <mrow /> <mn>2</mn> <mrow /> </mmultiscripts> </math></EquationSource> </InlineEquation> prism in the Kretschmann configuration. The optical response of the multilayer system is analyzed using the transfer-matrix method (TMM), and the structural parameters are optimized to achieve enhanced sensitivity and detection accuracy (DA). The optimized configuration yields a maximum angular sensitivity of 289.62<InlineEquation ID="IEq2"> <EquationSource Format="TEX">$^\circ $</EquationSource> <EquationSource Format="MATHML"><math> <mmultiscripts> <mrow /> <mrow /> <mo>∘</mo> </mmultiscripts> </math></EquationSource> </InlineEquation>/RIU and a figure of merit (FoM) of 46.86/RIU, corresponding to a refractive index (RI) variation (<InlineEquation ID="IEq3"> <EquationSource Format="TEX">$\Delta n_s$</EquationSource> <EquationSource Format="MATHML"><math> <mrow> <mi mathvariant="normal">Δ</mi> <msub> <mi>n</mi> <mi>s</mi> </msub> </mrow> </math></EquationSource> </InlineEquation>) of 0.027 and a resonance angle shift (<InlineEquation ID="IEq4"> <EquationSource Format="TEX">$\Delta \theta _{\text {SPR}}$</EquationSource> <EquationSource Format="MATHML"><math> <mrow> <mi mathvariant="normal">Δ</mi> <msub> <mi>θ</mi> <mtext>SPR</mtext> </msub> </mrow> </math></EquationSource> </InlineEquation>) of 8.1<InlineEquation ID="IEq5"> <EquationSource Format="TEX">$^\circ $</EquationSource> <EquationSource Format="MATHML"><math> <mmultiscripts> <mrow /> <mrow /> <mo>∘</mo> </mmultiscripts> </math></EquationSource> </InlineEquation>. Reflectance spectra are simulated at a wavelength of 633 nm across an RI range from 1.330 to 1.360. Results confirm the sensor’s capability to detect subtle RI changes due to low concentrations of NaCl (as low as 0.2 mg in 10 mL) and other contaminated water samples. This study demonstrates the potential of graphene/MXene-enhanced ASPR sensors as a promising platform for sensitive and label-free water quality monitoring in environmental and industrial applications.</p>

Surface Plasmon Resonance Sensor Using Graphene/MXene Heterostructure for Detection of Salinity-Induced Water Contamination

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发表日期：

2025年7月16日

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Mohan Kumar Paswan,
Rikmantra Basu

摘要

In this work, we investigate the detection of contaminants in water, including varying concentrations of sodium chloride (NaCl), using angular interrogation-based surface plasmon resonance (ASPR). The proposed sensor structure comprises a silver (Ag) thin film, a graphene/MXene heterostructure, and a sensing medium, integrated with a CaF $_2$ $_{2}$ prism in the Kretschmann configuration. The optical response of the multilayer system is analyzed using the transfer-matrix method (TMM), and the structural parameters are optimized to achieve enhanced sensitivity and detection accuracy (DA). The optimized configuration yields a maximum angular sensitivity of 289.62 $^\circ $ $^{\circ}$ /RIU and a figure of merit (FoM) of 46.86/RIU, corresponding to a refractive index (RI) variation ( $\Delta n_s$ $Δ n_{s}$ ) of 0.027 and a resonance angle shift ( $\Delta \theta _{\text {SPR}}$ $Δ θ_{SPR}$ ) of 8.1 $^\circ $ $^{\circ}$ . Reflectance spectra are simulated at a wavelength of 633 nm across an RI range from 1.330 to 1.360. Results confirm the sensor’s capability to detect subtle RI changes due to low concentrations of NaCl (as low as 0.2 mg in 10 mL) and other contaminated water samples. This study demonstrates the potential of graphene/MXene-enhanced ASPR sensors as a promising platform for sensitive and label-free water quality monitoring in environmental and industrial applications.