Optode optical fiber chemical sensor

Recently, optodes (optical fiber chemical sensors) have been actively studied due to their inherent characteristics such as immunity to electrical noise, ease of miniaturization and the possibility of real time monitoring and remote sensing. For example, a change in absorption peak with humidity is observed using a Nafion membrane ion exchanged with dye, such as crystal violet305 or tri-phenylcarbinol.306 Similarly, a Nafion membrane loaded with the ruthenium complex [Ru(bpy)2(dhphen)]2 (bpy 2,2 -bipyridine, dhphen 4,7-dihydroxy-1,10-phenanthroline) has been used as an optical pH sensor.307... 

Optical (fiber) chemical sensors [1] are capable of measuring a single species in an untreated sample by simply bringing into contact sample and sensor Separation steps or addition of chemical reagents are not required This is the preferred method in case of samples where the matrix does not vary to a large extent, e g blood However, optodes also represent useful detectors for use in chromatography, flow injection analysis... 

An optode is a chemical sensor based on an optical fiber. To understand how optodes work, we first need to know a little about refraction of light. 

From a general point of view, a chemical sensor is a device capable of continuously monitoring the concentration of an analyte. The two main classes are electrochemical sensors and optical chemical sensors. The latter are based on the measurement of changes in an optical quantity refractive index, light scattering, reflectance, absorbance, fluorescence, chemiluminescence, etc. For remote sensing, an optical fiber is used, and the optical sensor is then called an optode because of... 

We can create optical sensors for specific analytes by placing a chemically sensitive layer at the end of the fiber. An optical fiber sensor is called an optode (or opt rode), derived from the words "optical and "electrode. Optodes have been designed to respond to diverse analytes such as sulfites in food, nitric oxide in cells, and explosives in groundwater.12... 

Figure 10. Basic elements for flourescent fiber optic chemical sensors a. Optode Structure Design after Lubbers and Opitz (69) b. Optode Structure Design after Hirshfeld, et al. (71).

This section attempts to present a broad review of this technique in the light of recent research on fiber-optic chemical sensors (FOCS). A discussion on the advantages and performance of pH optodes will be broached by considering the various applications planned and the resulting pH measurements, including titration and ionic strength. Sensors for low molecular weight electrolytes, particularly optodes for anions and cations in solution, are also considered. 

It was mentioned before that fiber-optic chemical and biosensors are broadly classified into two categories extrinsic- and intrinsic-type sensors. In the extrinsic-type sensors, the fiber is acting as a link connecting optical signals to (and from) the active material (medium) positioned at the end of the fiber, such as the Optode case. In the intrinsic-type sensors, the fiber is modified in different ways, through construction of the sensing component, which will be explained next. 

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