Visible wavelength interrogation of Kretschmann based SPR spectroscopy using polymeric ZnO quantum Dot layer for chloride detection

Applying visible-wavelength interrogation Kretschmann SPR spectroscopy technique using a polymeric ZnO-Quantum Dot PVA (pZnOQD) layer for chloride ion detection represents a significant advancement in photonic technology. This method streamlines the detection process while maintaining high sensitivity. Molecular analysis reveals subtle shifts in specific peaks of the ZnOQD spectrum after the interaction, suggesting chloride ion interaction with the active layer. Subsequent SPR analysis confirms these findings, showing wavelength shifts in SPR peaks between 630 – 660 nm across different chloride ion concentrations. This technique demonstrates exceptional sensitivity, detecting chloride ion concentrations from 1.0 to 20.0 ppm, with two distinct sensitivity ranges (1.0 – 4.0 ppm and 4.0 – 20.0 ppm) and corresponding values of 1.7221 (R² = 0.998) and 0.627 nm/ppm (R² = 0.992), respectively. These results are comparable, with a low detection limit of 0.3 ppm. Experimental data fitting well with the Sips model yields an R² value of 0.995 and a binding affinity of 3.876 × 10²M⁻¹, providing valuable insights for sensor development. This integrated analysis provides a comprehensive understanding of chloride ion interactions with the pZnOQD sensing layer, paving the way for advanced optical spectroscopy using quantum dots.