Performance analysis of plasmonic sensor modified with chitosan-graphene quantum dots based bilayer thin film structure for real-time detection of dopamine

The performance of surface plasmon resonance (SPR) sensor modified with chitosan-graphene quantum dots (CS-GQDs)/Au bilayer thin film for dopamine (DA) detection was evaluated in this work. The sensor’s selectivity to DA was evaluated in the presence of various interfering substances. The sensor’s stability was examined over three weeks. Additionally, the repeatability of this sensor was assessed through nine successive measurements, and its reproducibility was evaluated using six different sensor films. The sensor demonstrated excellent selectivity to DA when 1 pM of DA was introduced to a 100 pM mixture of epinephrine, ascorbic acid, and uric acid. Furthermore, the storage stability of the sensor was found to be excellent. The sensor showed good repeatability as well as reproducibility with relative standard deviation (RSD) values of 0.343% and 0.229%, respectively while detecting 1 fM of DA. The real-time DA detection showed that obtained response signals were stable after roughly 10 minutes of injection of all concentrations. By fitting the experimental data to Pseudo-first-order (PFO) kinetic model, the equilibrium SPR angular shift was 0.318◦ with adsorption rate constant of 0.240 min−1 for 1 fM DA contacting the sensor surface. AFM images revealed that DA influenced the surface morphology of the sensor film, changing its average roughness by 0.710 nm, and FTIR spectra showed changes in the spectral bands and peaks intensities. These findings showed that CS-GQDs/Au based SPR sensor is an advantageous option for rapidly and economically diagnosing DA deficiency with high selectivity and sensitivity.

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