Combined Electrochemical Surface Plasmon Resonance for Angle Spread Imaging of Multielement Electrode Arrays

Abstract

A surface plasmon resonance imaging system combined with a multielement electrode array is described. An optical system with shaping optics is used to direct a wedge of light onto a gold-coated sample. The reflected light is detected in the form of an angle-spread image of the surface, with one direction denoting a variable incident angle and the other showing a span of locations along one lateral direction of the sample surface. At the proper incident angle, the angle-spread image shows the complete surface plasmon resonance curve over a span of locations on the surface. This imaging system is combined with a sample configuration consisting of a series of gold microelectrode bands, each with independent electrochemical control. In solution, this system can be used to perform high-throughput and dynamic electrochemical experiments. Simultaneous measurement of electrochemical and surface plasmon resonance can be quantitatively performed on each of the electrode surfaces either by holding each electrode at a different potential value or by scanning the applied potential. The sensitivity of this configuration is demonstrated by monitoring oxide formation and removal at a gold electrode in an aqueous electrolyte. A second example, with the use of a thin poly(aniline) coating, illustrates the ability to monitor film changes, including thickness, dielectric properties, and associated electrochemically induced polymer oxidation/reduction on multiple electrodes. This represents a simple and compact method for combining the sensitivity of surface plasmon resonance into an array-based, high-throughput electrochemical system.

Sensitivity‐enhancement methods for surface plasmon sensors

“…The key idea is that the SPR reflectance intensity varies with the near-field refractive index of the test fluid, which in turn depends on the micro/nanofluidic scalar properties, such as concentrations, temperatures, and phases. A combined electrochemical and SPR measurements can be performed on a multielectrode sample such that a large number of electrochemical potentials and associated surface phenomena can be interrogated in a single experiment [111]. Although most of these research works are based on the SPR intensity imaging technique, phase-sensitive SPR imaging was also presented in the works of Wong et al [96] and Lee et al [97].…”

Optical and Electrochemical Combination Sensor with Poly‐Aniline Film Modified Gold Surface and Its Application for Dissolved Oxygen Detection

“…Meanwhile, the TIRIE response on the bare gold surface shows that the grayscale change in Figure 2B could be attributed to the change of the optical property of the PAn film which results from the change of the oxidation states of the PAn film during its oxidation or reduction process. The redox processes of the PAn film are also accompanied by structural transformation due to the doping and undoping processes involving protons and anions [36,37].…”

“…Clear current change is obtained from 0 mV, reflecting the ready oxidation of the polymer film. The redox couple in the CV is corresponding to the transformation between the reduced state and the oxidized state of poly-aniline [35][36][37]. The TIRIE curve also yields a similar couple of peaks at the redox potential of the PAn film.…”

Combined surface plasmon resonance and impedance spectroscopy systems for biosensing

“…Various EIS biological sensing systems have been proposed and some of them employ interdigitated electrode (IDE) arrays 8,9 fabricated by conventional microfabrication technology. These two techniques, SPR and EIS, can complement each other in the development of novel sensing platforms 10 and biochemical procedures 11 for simple, rapid and label-free detection of biomolecules with improved sensitivity and functionality. For example, electrokinetic label-free screening 12 or the integration of dielectrophoresis (DEP) with biochips 13 has the potential to advance the chip-based immunoassay methods for microbial detections in point-of-care diagnostics devices.…”