Thiophene structure influences plasmonic creatinine sensing through molecular interaction and surface morphology

This study investigates the influence of molecular structure on plasmonic sensing performance by comparing two thiophene-based small molecules, benzo[b]thiophene-2-carboxaldehyde (BTCA) and tetrahydrothiophene (THT), as sensing interfaces for label-free creatinine detection. Surface plasmon resonance (SPR) measurements, supported by Fourier-transform infrared spectroscopy (FTIR), field emission scanning electron microscopy (FESEM), energy-dispersive X-ray spectroscopy (EDX), and atomic force microscopy (AFM), reveal distinct differences in analyte interaction and interfacial behavior. BTCA, featuring a conjugated aromatic aldehyde structure, enables stronger hydrogen bonding and dipole-dipole interactions with creatinine, evidenced by spectral changes, vibrational mode suppression, and uniform surface morphology. These interactions contribute to a more linear and consistent SPR response (R² = 0.97) compared to THT, which exhibits weaker molecular interactions, disordered surface features, and a segmented sensing profile. This comparative analysis highlights how the molecular structure of thiophene derivatives influences interfacial interaction and sensing behavior. The findings provide experimental evidence that structural differences between BTCA and THT result in distinct surface morphologies and optical responses, offering practical guidance for selecting suitable sensing layers in plasmonic creatinine detection.