Optimization of a surface plasmon resonance sensor through the integration of black phosphorus layers for the detection of carcinoembryonic antigen (CEA)

In this work, we theoretically investigated the enhancement of the performance of a multilayer surface plasmon resonance biosensor using black phosphorus layers. The experimental setup consisted of a BK7 prism, a gold thin film, an aluminum oxide layer, and different black phosphorus configurations (P = 0, P = 1, P = 2) for carcinoembryonic antigen detection. Using the 633 nm transfer matrix method, we systematically analyzed the effect of the number of black phosphorus layers on sensitivity, full width at half maximum, and figure of merit. The simulations demonstrated that adding black phosphorus layers enhanced sensitivity from 148.84 deg/RIU for the control sensor (P = 0) to 167.30 deg/RIU with two layers (P = 2). Although this increase in sensitivity was accompanied by an increase in full width at half maximum (FWHM), there was a slight decrease in figure of merit from 36.39 RIU − 1 (P = 0) to 34.25 RIU − 1 (P = 2) representing a 12.4% improvement in sensitivity. The theoretical limit of detection (LOD) achieved was 0.053 ng/mL (nearly 100 times lower than the clinically defined cutoff for CEA). To ensure the reliability of the results, the data were subjected to a Monte Carlo uncertainty analysis ( N = 500), which verified the robustness of the enhancement against a ± 0.5% fabrication tolerance. While the increase in sensitivity resulted in a slight decrease in FOM (36.39–34.25 RIU − 1 ); the BP-amplified architecture provides performance comparable to that of other 2D material-based designs. These results demonstrate the trade-off between sensitivity and spectral width; thus, providing a roadmap for the development of high-performance, label-free diagnostic platforms for detecting early-stage cancer.