Study of luminol electrochemiluminescence with a planar optical waveguide for peroxide sensor application

The work presented in this paper is aiming at the development of a highly sensitive, specific, cheap and widely applicable new sensor based on the combination of optical and electrochemical techniques. In addition to the analytically valuable information of light intensity generated, the light transient resulting from a double potential step experiment contains kinetic information for both the electrochemical step as well as for the successive diffusion and chemical steps in the reaction layer. The comparison of transients due to short range waveguide-evanescent field coupling as shown in Fig. 2 and those obtained by measuring light over the full depth of the diffusion layer in Fig. 3 can be used to obtain such information

Broadband Coupling into a Single-Mode, Electroactive Integrated Optical Waveguide for Spectroelectrochemical Analysis of Surface-Confined Redox Couples

Pushing the sensitivity of spectroelectrochemical techniques to routinely monitor changes in spectral properties of thin molecular films (i.e., monolayer or submonolayer) adsorbed on an electrode surface has been a goal of many investigators since the earliest developments in this field. 1 It was initially recognized that exploiting the evanescent field generated by total internal reflection at the interface of an optically transparent electrode (such as a thin film of tin oxide or indium tin oxide (ITO) on glass or quartz) has the inherent advantage of selectively probing only the near-surface region, as opposed to bulk sampling with transmission based techniques. Furthermore, by utilizing the multiple reflections in an attenuated total reflectance (ATR) geometry, an enhancement in sensitivity can be realized, and as the thickness of the ATR element is decreased, the number of reflections increases, yielding a substantial sensitivity enhancement. [2][3][4][5][6] Itoh and Fujishima were the first to show the advantages of reducing the thickness of an ATR element overcoated with a transparent conductive oxide to the integrated optical waveguide (IOW) regime. Using a four-mode, gradient index waveguide coated with a transparent, conductive tin oxide layer, they demonstrated large sensitivity enhancements, relative to a single pass transmission experiment, for spectroelectrochemical measurements of methylene blue. 7,8 Other research groups subsequently described similar gradient index, multilayer, electroactive waveguide structures, but they did not make use of the technology to explore the spectroelectrochemistry of (sub)monolayer coverage films. [9][10][11][12][13] We recently described a single-mode, electroactive planar IOW (the EA-IOW) having a step refractive index profile. It was fabricated by sputtering a Corning 7059 glass layer (400 nm) over soda lime glass or quartz, followed by a 200-nm layer of SiO 2

Electrochemiluminescence detection of glucose-oxidase as a model for flow-injection immunoassays

Glucose oxidase was covalently attached to an aminosilanized indium tin oxide coated glass wafer with the hydroxysuccinimide ester of pyridyldithiopropionic acid. The wafer was used as the working electrode in the reaction chamber of a flow injection analyser. When a solution of glucose and luminol was passed over the electrode, glucose was oxidized enzymatically and luminol was oxidized electro-chemically. The products of these reactions generated light in proportion to the amount of glucose in the sample. When glucose was assayed in the range 0-10 mM the detection limit was 0.419 mM with a correlation coefficient of 0.9962

Detection of glucose via electrochemiluminescence in a thin-layer cell with a planar optical waveguide

Light generated by luminol electrochemiluminescence is coupled into a simple planar optical waveguide and is collected with a photomultiplier tube and a photon counter unit. The waveguide is mounted to a thin-layer cell which is connected to a flow injection analysis system. The waveguide is coated with indium tin oxide and modified with covalently attached glucose oxidase. The range of detection for glucose is 0-10 mM (correlation coefficient r = 0.9974), with a detection limit of 0.3 mM

Broadband Coupling into a Single-Mode, Electroactive Integrated Optical Waveguide for Spectroelectrochemical Analysis of Surface-Confined Redox Couples

Pushing the sensitivity of spectroelectrochemical techniques to routinely monitor changes in spectral properties of thin molecular films (i.e., monolayer or submonolayer) adsorbed on an electrode surface has been a goal of many investigators since the earliest developments in this field. 1 It was initially recognized that exploiting the evanescent field generated by total internal reflection at the interface of an optically transparent electrode (such as a thin film of tin oxide or indium tin oxide (ITO) on glass or quartz) has the inherent advantage of selectively probing only the near-surface region, as opposed to bulk sampling with transmission based techniques. Furthermore, by utilizing the multiple reflections in an attenuated total reflectance (ATR) geometry, an enhancement in sensitivity can be realized, and as the thickness of the ATR element is decreased, the number of reflections increases, yielding a substantial sensitivity enhancement. [2][3][4][5][6] Itoh and Fujishima were the first to show the advantages of reducing the thickness of an ATR element overcoated with a transparent conductive oxide to the integrated optical waveguide (IOW) regime. Using a four-mode, gradient index waveguide coated with a transparent, conductive tin oxide layer, they demonstrated large sensitivity enhancements, relative to a single pass transmission experiment, for spectroelectrochemical measurements of methylene blue. 7,8 Other research groups subsequently described similar gradient index, multilayer, electroactive waveguide structures, but they did not make use of the technology to explore the spectroelectrochemistry of (sub)monolayer coverage films. [9][10][11][12][13] We recently described a single-mode, electroactive planar IOW (the EA-IOW) having a step refractive index profile. It was fabricated by sputtering a Corning 7059 glass layer (400 nm) over soda lime glass or quartz, followed by a 200-nm layer of SiO 2