Design and performance improvement of silver-gallium sulfide-TDMC heterostructure-based surface plasmon resonance nano biosensor for detection of fat in milk

Milk fat is an important constituent of dairy products, which strongly determines the flavor, texture, nutrition, and market price of dairy products. Determining the fat content accurately is essential for the quality control of dairy products. In this work, we investigate, numerically, the performance of a surface plasmon resonance (SPR) Nano-biosensor for milk fat detection by angular interrogation method at a wavelength of 633 nm. The proposed sensor’s design using Kretschmann configuration composed of multilayered-Sulfide-based structure targeting for enhanced effective serial detection. Silver (Ag) layer is deposited on the substrate, followed by two layers which are silver gallium sulfide (\({AgGaS}_{2}\)) and lithium gallium sulfide (\({LiGaS}_{2}\)). Moreover, hybrids nanomaterials like BlueP/\({WSe}_{2}\), BlueP/\({MoSe}_{2},\) BlueP/\({MoS}_{2}\), and BlueP/\({WS}_{2}\) are incorporated to enhance the performance. Such materials exploit surface plasmon excitations and evanescent fields for highly sensitive fat detection. The higher field intensity and further penetration into the sensing layer contributes to the larger interaction volume, hence the increase in sensitivity of the sensor. The range of the biological analytes that can be detected by the proposed sensor is as low as 1.3450 to 1.3621 refractive index. Throughout the investigation the proposed structure shows the highest maximum sensitivity (359°/RIU), quality factor (97.42 RIU⁻¹), and detection accuracy (1.66), showing a significant improvement compared with existing work.