In this work, we investigate how the application of an external potentialuddifference to the sensitive gold-electrolyte interface influences the optical response of audsensor based on the surface plasmon-polariton resonance (SPPR). The SPPR resonantudangle shift was registered for an aqueous solution of sulfuric acid as an electrolyte atuddifferent potential sweep rates. From the measurements of SPPR curves versus theudapplied voltage, the potential of zero charge of the gold electrode in the electrolyteudsolution was estimated. To explain the external voltage influence on the SPPR sensorudresponse, a theoretical model was used that takes into account three factors: free electronudconcentration change in the space-charge layer (SCL) in the surface layer of gold,uddependence of the capacity of electrical double layer at the interface on the voltage, andudgold film surface roughness.
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