A Performance-Enhanced Bimetallic Chip for the Detection of Cadmium Ions with Surface Plasmon Resonance

We demonstrate that a designed bimetallic chip is capable of improving the performance of a surface plasmon resonance (SPR) sensor based on angular interrogation. Through a numerical simulation and a refractometry experiment, we prove that this bimetallic chip can effectively reduce the noise level by about a factor of 2 compared to the traditional SPR sensors that only use a single gold film. The bimetallic chip presents a lower refractive index resolution of 5.3 × 10⁻⁷ refractive index units. In addition, the enhancement of the electric field intensity at the surface of the configuration by a factor of 2 makes it possible to have a high sensitivity in a larger region, which promotes the biosensing applications of the chip. Through a simple and novel method for the detection of cadmium ions (Cd²⁺) based on the bimetallic configuration, a detection level for Cd²⁺ (0.01 μM or 1.12 ppb) can be realized, which compares favorably with similar studies.