# An Optimized Graphene-Based Surface Plasmon Resonance Biosensor for Detecting SARS-CoV-2
## 3 Results and Discussions
### Comparison with Previous Reports  
To contextualize the performance of \(\text{Sys}_{8}\) configuration, a comparison with other reported SPR-based systems for virus detection [33; 34; 35; 36] was conducted. Table 1 presents key metrics for sensitivity, stability, linearity, responsivity, and detection limit, highlighting \(\text{Sys}_{8}\)'s competitive standing within the field of viral diagnostics. \(\text{Sys}_{8}\) demonstrated a high sensitivity of 315.91\({}^{\circ}\)/RIU, comparable to the Ag-based multilayer system developed by [PERSON] et al. [36] for SARS-CoV-2 detection, which exhibited a sensitivity of 320.50\({}^{\circ}\)/RIU. This level of sensitivity is critical for detecting low concentrations of viral particles, emphasizing \(\text{Sys}_{8}\)'s utility in applications requiring precise viral load monitoring, especially at early infection stages. Notably, \(\text{Sys}_{8}\) outperformed other  
Figure 8: (**a**) Variation angle after the adsorption of SARS-CoV-2 at different concentrations from 0 to 525 mM. Performance metrics: (**b**) sensitivity, (**c**) detection accuracy, and (**d**) figure of merit as a function of the SARS-CoV-2 concentration. configurations, such as the gold-antibody-based SPR biosensor for hepatitis A virus (HAV) by [PERSON] et al. (2020), which achieved a sensitivity of 265.00\({}^{\circ}\)/RIU. In terms of stability, \(\text{Sys}_{8}\) displayed high operational consistency, attributed to the combined use of silicon nitride and graphene layers, which provide enhanced structural and optical robustness. This stability aligns with the high stability reported by [PERSON] et al. (2020) for their gold-antibody-based system but exceeds that of the nano-layered SARS-CoV-2 sensor by [PERSON] et al. (2020), which displayed moderate stability. Such stability is crucial for sustained diagnostic applications where sensor durability under repeated measurements is essential. Regarding linearity, \(\text{Sys}_{8}\) exhibited a linear response across a concentration range of 150-400 mM, which is on par with the Ag-based multilayer sensor by [PERSON] et al. (2020) and slightly narrower than the nano-layered SPR sensor by [PERSON] et al. (2020), which reported a range of 200-500 mM. However, \(\text{Sys}_{8}\)'s linearity range covers a clinically relevant concentration spectrum, enabling accurate quantification of SARS-CoV-2 across various viral loads encountered in diagnostic settings. The responsivity of \(\text{Sys}_{8}\) was measured at 4.2\({}^{\circ}\) at 400 mM, slightly higher than the 4.1\({}^{\circ}\) achieved by [PERSON] et al. (2020) for a similar concentration. This level of responsivity highlights \(\text{Sys}_{8}\)'s capability to detect incremental changes in viral concentration, an essential feature for real-time monitoring applications. This responsivity aligns well with clinical needs, facilitating rapid response to fluctuations in viral load. Lastly, \(\text{Sys}_{8}\) demonstrated a detection limit of 150 mM, comparable to the Ag-based sensor by [PERSON] et al. (2020) and lower than the detection limit of 200 mM reported by [PERSON] et al. (2020) for their nano-layered configuration. A lower detection limit enables \(\text{Sys}_{8}\) to detect minimal viral concentrations, making it particularly suitable for early diagnostic applications where low viral loads are expected.