Salivary Uric Acid Detection With Graphene–Gold Bilayers Surface Plasmon Resonance

This article proposes a Kretschmann configuration surface plasmon resonance (SPR) sensor setup incorporating gold and graphene quantum dot (GQD) bilayers for the detection of uric acid (UA) solution. The confirmation of the deposition of gold and GQD films onto the sensor substrate was accomplished through the utilization of a field emission scanning electron microscope (FESEM) and energy-dispersive X-ray (EDX) spectroscopy. Analysis revealed an average film thickness of 55.4 nm for the gold film and 5.8 nm for the GQD film. Different concentrations of UA solution were tested with the proposed setup and the performance was evaluated in terms of sensitivity, linearity, limit of detection (LOD), binding affinity, full width at half maximum (FWHM), detection accuracy (DA), signal-to-noise ratio (SNR), and figure of merit (FOM). The sensitivities achieved for the SPR sensors were 0.23 and 3.77 %/(mg/dL) with correlation coefficients of 0.0318 and 0.825 for gold and gold–GQD, respectively. The corresponding LODs were 32.85 and 4.74 mg/dL, with binding affinity constants of 91.87 and
$89.18\,\,\mu \text {M}^{-1}$
, respectively. Adding GQD to the gold film increased the sensitivity of the SPR sensor substantially while demonstrating excellent reproducibility, repeatability, and reusability, exalted DA and SNR, constricted FWHM, and superlative FOM. These outcomes harbor the potential to spark a proficient and modest technique that enables the detection of UA in saliva, thus expediting near-patient testing.