Carcinoembryonic antigen (CEA) is a critical biomarker for diagnosing and monitoring cancers such as liver, colon, and breast cancer. This study presents a highly sensitive surface plasmon resonance (SPR) sensor incorporating 2D materials—graphene and MXene (Ti₃C₂T_X)— in a Kretschmann configuration. The sensor, comprising a BK7 prism, gold (Au), graphene, aluminum oxide (Al₂O₃), and MXene, is optimized for detecting CEA in aqueous solutions with high precision. The performance of the proposed sensor was evaluated using the finite difference time domain (FDTD) numerical method, focusing on key parameters such as sensitivity and figure of merit (FOM). Operating at a wavelength of 633 nm, the sensor achieved an exceptional sensitivity of 163.63 deg/RIU and an FOM of 17.52 RIU⁻¹, marking a significant improvement over previously reported SPR biosensors. Comparative analysis further underscores the superior performance of this design, establishing it as a cutting-edge tool for applications in biosensing, medical diagnostics, food safety, and environmental monitoring. The proposed sensor offers significant potential for real-world applications, including clinical diagnostics for early cancer detection, food safety monitoring, and environmental sensing.

This paper presents a concept to significantly improve the photocurrent of ultrathin crystalline silicon solar cells using plasmonic hemispherical dielectric-metal (core-shell) nanoparticles and backside gratings. The design of three-dimensional spherical and hemispherical arrays of nanoparticles on top of the surface of 0.8 μm crystalline silicon solar cells was simulated using finite-difference time-domain (FDTD) method. We used the FDTD results to investigate the photocurrent by solving the Poisson and drift diffusion equations. The results indicate an enhancement of between 80% and 93% in the photocurrent for cells with hemispherical Ag and Ag–SiO₂ core-shell nanoparticles, respectively, compared to a cell with spherical nanoparticles. In addition, for obtaining a higher photocurrent, triangular gratings were applied on the back side of the absorber and we obtained a photocurrent of $22\mathrm{mA}/{\mathrm{cm}}^2$. The simulated results indicate that the proposed structures increase the spectral response of thin-film crystalline silicon solar cells over a solar spectrum in the range of 400 nm–1200 nm. Finally, we investigated photocurrent as a function of incidence light angle and concluded that this approach is applicable to various thicknesses and shapes of nanoparticles.

In this paper, we propose and theoretically investigate a novel multimode refractive index (MMRI) plasmonic optical sensor for detecting various brain cancer cells, leveraging the unique capabilities of split ring resonators (SRRs). The sensor, simulated using the finite-difference time-domain (FDTD) method, exhibits dual resonance modes in its reflection spectrum within the 1500 nm to 3500 nm wavelength range, marking a significant advancement in multimode plasmonic biosensing. Through detailed parametric analysis, we optimize critical dimensional parameters to achieve superior performance. The novelty of this work lies in the dual-mode sensing mechanism, which enables robust detection by exploiting the resonance characteristics of gold, silver, and aluminum. These materials provide tunable and highly sensitive interactions with light, enhancing the sensor’s adaptability for a wide range of applications. The results reveal exceptional sensitivity values of 1778.3 nm/RIU, a limit of detection (LOD) of 0.016 RIU, and a high figure of merit (FOM) of 7 RIU⁻¹, along with a quality factor (QF) of 11.7 in the first resonance mode. The findings show that the designed optical biosensor exhibits high sensitivity, a good LOD, and an acceptable FOM in both resonance modes. So, this work paves the way for future research and development of susceptible, multimode optical sensors for medical diagnostics. The results indicate that the proposed sensor operates effectively across a range of temperatures and angles of radiant light, demonstrating its independence from these variables. This reliability in performance underscores its potential for use in diverse environments, making it a dependable tool for detecting biological samples, including brain cancer cells, irrespective of external conditions.

Nowadays, there is a great interest in discovering alternative approaches to reduce the cost per the output power of first generation crystalline silicon solar cells. Light propagation in solar cells is controlled by interaction between periodic structure filters and light. Therefore, designing ultrathin solar cells in which light is trapped in the active layer is so important to efficiently absorb the light. In the present paper, the combination of a distributed Bragg reflector (DBR) with a rectangular- or triangular-shaped grating is introduced as a photonic backside filter for both TE and TM polarizations. It is shown that by applying this DBR with a triangular grating, it is possible to enhance the efficiency of crystalline solar cells up to 20% for 2.5 μm Si cells in TE-polarized incident light. By optimizing the shape of the grating, the efficiencies can be increased to 22.1% and 23.52% in 5 μm and 7.5 μm Si solar cells for TE-polarized incident light, respectively. Similar results have been achieved for TM-polarized incident light. In addition, introducing rectangular or triangular grating structures improves light trapping over the solar spectrum from 400 to 1100 nm which is revealed by calculation of the electric field. The triangular-shaped gratings are an effective approach for light trapping in thin crystalline solar cells and will inspire low-cost high-efficiency solar cell designs. Finally, efficiency as a function of angle of incidence of light for a triangular grating has been obtained. Finding results in this work show promise for designing ultrathin solar cells with enhanced light absorption.