D-shaped Surface Plasmon Resonance Research Articles

MXene (Ti3C2Tx) coated highly-sensitive D-shaped photonic crystal fiber based SPR-biosensor

In this paper, a D-shaped surface plasmon resonance (SPR) refractive index (RI) based biosensor is reported for the earlier detection of various bio-analytes. The lattice of D-shaped photonic crystal fiber (PCF) offers a modified rhombus pattern for cladding air holes. D-shaped PCF is an open channel structure that fundamentally provides ease while interacting with different bio-analytes as compared to closed channels SPRs. A nanoscale MXene (Ti3C2Tx) layer is introduced with a uniform coating that drastically enhances the sensor’s sensitivity and performance. Finite element method (FEM) is employed to determine dispersion characteristics to acquire the confinement loss spectra as a function of wavelength for various bio-analytes. SPR shifts the resonant interference dip when RI of bio-analytes changes. The proposed SPR sensor with Au/ Ti3C2Tx layer exhibits maximum RI sensitivity of 47,260 nm/RIU at an analyte refractive index of 1.42 with a detection resolution of 2.11 × 10−6 RIU, which is 1.7 times higher than that of a single Au-layer SPR sensor. Moreover, it detects a wider range of bio-analytes (i.e., 1.30–1.43) using a third-order polynomial fitting function corresponding to the wavelength shift. It covers the detection of most known bio-analytes, i.e., cancerous cervical, breast and blood cells, adrenal gland, glucose concentration, proteins, viruses or DNA/RNA, etc.

Au-strip's shape dependent performance of D-shaped SPR based sensors

D-shaped Surface Plasmon Resonance (SPR) based sensors show great promise for detecting different analytes with improved sensitivity and resolution. This work focuses on the investigation of the effect of gold (Au) strip's shape on the performance of D-shaped SPR sensor having a single mode germanium (Ge) core and microfluidic channel for analytes. Three different designs of Au strips namely, flat (design A), parabolic (design B), and combined (design C) having mixing of small flat and parabolic strips are considered here. The detailed numerical investigations are performed for all the designs using the finite element method. The highest wavelength and amplitude sensitivities are found to be 44 μm/RIU and 115.85 RIU−1, respectively at a resolution of 2.27 × 10−06 for the parabolic-shaped Au strip (i.e., design B). Alternately, design A shows reduced wavelength and amplitude sensitivities of 13 μm/RIU and 51.43 RIU−1, respectively with a resolution of 7.69 × 10−06. Similarly, design C reveals the wavelength and amplitude sensitivities of 14 μm/RIU and 45.01 RIU−1, respectively with a resolution of 7.14 × 10−06. Thus, the sensitivity of D-shaped SPR based sensors could be tuned significantly by modifying only the shape of the metal strip. This analysis would be useful in designing highly sensitive SPR based sensors.