Signal-triggering, molecular devices

The signal-triggered functions of these molecular assemblies have to be first characterized in bulk solution. Then, extensive efforts have been directed to integrate these photoswitchable chemical assemblies with transducers in order to tailor switchable molecular devices. The redox properties of photoisomerizable mono-layers assembled on an electrode surface are employed for controlling interfadal electron transfer [16]. Specifically, electrical transduction of photonic information recorded by photosensitive monolayers on electrode supports can be used in developing monolayer optoelectronic systems [16-19]. Electrodes with receptor sites exhibiting controlled binding of photoisomerizable redox-active substrates from the solution [20] also allow the construction of molecular optoelectronic devices. 

The sensitivity of an optical biosensor depends on two main factors the capacity of the sensing layer to bind the analyte and the optical detection limit of the device (minimum amount of analyte able to trigger a signal). The first depends on the affinity of the interaction and the number of binding sites accessible to the analyte. The second depends on the molecular weight of the analyte, the signal-to-noise ratio and drift. 

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