Calcein and calcein−Ag films under vapor exposure: Sensing properties and reversible film restructuring

We studied the adsorption properties of organic and organic-inorganic films based on the dye calcein. Embedding of silver nanoparticles increases film sensitivity to some analytes (in particular, sensitivity to ethanol increases by about 30%). Both films demonstrate high sensitivity to water vapor, response of about 7000 Hz for a quartz crystal microbalance sensor. Our investigations showed that essential restructuring of films and increase in their thickness occurs in the course of adsorption of water molecules. These changes are reversible: after drying, the sensor response reverts to zero and the film structure is fully restored. The value and reversibility of changes occurring because of adsorption processes at the surfaces of calcein and calcein−Ag films make these materials very promising for application not only in sensorics but also when developing nanoactuators as well.