Towards fluorescence-based chemical sensing devices

consisting of a free-base porphyrin with an appended quinone, is weakly fluorescent due to PET. Complexation with substituted hydroquinones induces fluorescence enhancement because of the unfavorable conditions for PET from the porphyrin to the quinone-hydroquinone entity. 

Towards fluorescence-based chemical sensing devices 

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 

Electrochemical sensors have several disadvantages with respect to optical sensors (i) they are based on electrodes and require a reference electrode (ii) the liquid-liquid junction is easily perturbed by external factors (iii) they are sensitive to electrical interferences (iv) miniaturization is not easy and their cost is relatively high. However, optical sensors also have some disadvantages (i) ambient light can interfere (ii) the range over which the concentration of an analyte can be accurately measured is often limited (iii) they have generally limited long-term stability. 

Among optical sensors, those based on fluorescence are of major interest because of their ability to use spectral and temporal information multi-wavelength measurements allow simultaneous detection of two or more analytes, and discrimination between analytes is possible by time-resolved measurements. Multiplex capabilities represent the main advantage of such sensors compared to electrochemical devices. 

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