The Tunable Parameters of Graphene-Based Biosensors
<p>Biosensor illustration. Proposed biosensors by using different metallic substrate configurations: (<b>A</b>) gold or silver, (<b>B</b>) silver/gold, and (<b>C</b>) gold/silver.</p> "> Figure 2
<p>Reflectance (%) before adsorption. SRP curves as a function of the angle of incidence (°), increasing the number of graphene layers from L0 (no graphene layer) to L9 (nine graphene layers). (<b>A</b>) prism/gold/graphene/sensing medium, (<b>B</b>) prism/silver/gold/graphene/sensing medium, (<b>C</b>) prism/silver/graphene/sensing medium, and (<b>D</b>) prism/gold/silver/graphene/sensing medium. (<b>B</b>,<b>D</b>) correspond to the calculations by reducing the thickness of each metallic substrate by 30%.</p> "> Figure 3
<p>Reflectance (%) after adsorption. SRP curves as a function of the angle of incidence (°), increasing the number of graphene layers from L0 (no graphene layer) to L9 (nine graphene layers). (<b>A</b>) prism/gold/graphene/sensing medium, (<b>B</b>) prism/silver/gold/graphene/sensing medium, (<b>C</b>) prism/silver/graphene/sensing medium, and (<b>D</b>) prism/gold/silver/graphene/sensing medium. (<b>B</b>,<b>D</b>) correspond to the calculations by reducing the thickness of each metallic substrate by 30%. (<b>F</b>) and (<b>G</b>) SPR resonance curves before/after adsorption for the conventional sensor (L0 and L0 + Ads) and the monolayer graphene sensor (L1 and L1 + Ads), assuming a refractive index change Δ<span class="html-italic">n</span> = 0.005, for the P/Au/G/M and P/Ag/G/M sensors, respectively.</p> "> Figure 4
<p>ATR minimum (%). Reflectance intensity as a function of the number of graphene layers, considering different metallic substrate configurations. (<b>A</b>) graphene first supported on gold after adsorption and (<b>B</b>) graphene first supported on silver after adsorption.</p> "> Figure 5
<p>ATR angle (°). Angle position as a function of the number of graphene layers, considering different metallic substrate configurations. (<b>A</b>) graphene first supported on gold before adsorption, (<b>B</b>) graphene first supported on gold after adsorption, (<b>C</b>) graphene first supported on silver before adsorption, and (<b>D</b>) graphene first supported on silver after adsorption.</p> "> Figure 6
<p>Normalized Reflectance after adsorption. SRP curves as a function of the angle of incidence (°), considering one graphene layer (L1). (<b>A</b>) Graphene first supported on gold and (<b>B</b>) Graphene first supported on silver.</p> "> Figure 7
<p>Normalized Reflectance after adsorption. SRP curves as a function of the angle of incidence (°), considering ten graphene layers (L10). (<b>A</b>) Graphene first supported on gold and (<b>B</b>) Graphene first supported on silver.</p> "> Figure 8
<p>Sensitivity enhancement (%). Sensitivity variation with reference to the conventional biosensor as a function of the number of graphene layers, considering different metallic substrate configurations.</p> "> Figure 9
<p>Full width at half maximum (FWHM) analysis (°). FWHM as a function of the number of graphene layers, considering different metallic substrate configurations. (<b>A</b>,<b>B</b>) graphene first supported on gold before/after adsorption, (<b>C</b>,<b>D</b>) graphene first supported on silver before/after adsorption. Note that it only included systems with a 30% reduction in each metallic substrate.</p> "> Figure 10
<p>Sensitivity to refractive index change. Sensitivity (°/<span class="html-italic">RIU</span>) as a function of the number of graphene layers, considering different metallic substrate configurations. Note that it only included systems with a 30% reduction in each metallic substrate.</p> "> Figure 11
<p>Detection Accuracy (DA). DA (dimensionless) as a function of the number of graphene layers, considering different metallic substrate configurations. Note that it only included systems with a 30% reduction in each metallic substrate.</p> "> Figure 12
<p>Quality Factor (QF). QF (<span class="html-italic">RIU</span><sup>−1</sup>) as a function of the number of graphene layers, considering different metallic substrate configurations. Note that it only included systems with a 30% reduction in each metallic substrate.</p> ">
Abstract
:1. Introduction
2. Material and Methods
2.1. Analyzed Biosensor Configurations
- (i)
- Graphene is expected to protect the metallic substrate made of gold, silver, or a combination of both. The high chemical stability and impermeability of graphene can serve as a barrier against oxidation and other environmental factors that can degrade the performance of silver and gold substrates [34]. This protective layer could extend the lifespan and reliability of the biosensor, ensuring consistent performance over time.
- (ii)
- Graphene serves as an effective BRE, improving the interaction with target molecules. The high surface area and strong π-stacking interactions of graphene with biomolecules enhance the adsorption efficiency, leading to higher sensitivity and better detection accuracy [14,35]. This characteristic is crucial for detecting low concentrations of analytes, making graphene-enhanced SPR biosensors highly suitable for various applications.
Component | Thickness (nm) | Refractive Index | Ref. |
---|---|---|---|
Prism | - | 1.7231 | [17] |
Gold (Au) | 50.0 | 0.1726 + 3.4218 i | [17] |
Silver (Ag) | 55.0 | 0.0563 + 4.2760 i | [7] |
Graphene | 0.34 | 2.7611 + 1.6987 i | [41] |
Graphite | ∞ | 2.8366 + 1.5946 i | [42] |
Water | - | 1.332 | [43] |
2.2. Theoretical Framework
2.3. Performance Metrics of the SPR Biosensor
- The sensitivity of the biosensors (SL) is defined as the multiplication of the sensitivity to the refractive index change () and the adsorption efficiency of the target analyte (E) as:
- The sensitivity to the refractive index change can be denoted as:
- The detection accuracy (DA) or signal-to-noise ratio can be expressed in terms of angle change (Δθ) and full width at half maximum (FWHM) as:
- Finally, quality factor (QF) can be expressed in terms of S and FWHM as:
3. Results and Discussion
3.1. Reflectance
- P/Ag/Au/G/M(30%)
- P/Au/Ag/G/M(30%)
3.2. ATR Angle
3.3. Normalized SPR Curve
3.4. Sensitivity Enhancement
3.5. Full Width Half Maximum (FWHM)
3.6. Effect on Sensitivity, Detection Accuracy, and Quality Factor
4. Conclusions
Supplementary Materials
Author Contributions
Funding
Institutional Review Board Statement
Informed Consent Statement
Data Availability Statement
Acknowledgments
Conflicts of Interest
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Tene, T.; Svozilík, J.; Colcha, D.; Cevallos, Y.; Vinueza-Naranjo, P.G.; Vacacela Gomez, C.; Bellucci, S. The Tunable Parameters of Graphene-Based Biosensors. Sensors 2024, 24, 5049. https://doi.org/10.3390/s24155049
Tene T, Svozilík J, Colcha D, Cevallos Y, Vinueza-Naranjo PG, Vacacela Gomez C, Bellucci S. The Tunable Parameters of Graphene-Based Biosensors. Sensors. 2024; 24(15):5049. https://doi.org/10.3390/s24155049
Chicago/Turabian StyleTene, Talia, Jiří Svozilík, Dennys Colcha, Yesenia Cevallos, Paola Gabriela Vinueza-Naranjo, Cristian Vacacela Gomez, and Stefano Bellucci. 2024. "The Tunable Parameters of Graphene-Based Biosensors" Sensors 24, no. 15: 5049. https://doi.org/10.3390/s24155049