ABSTRACT
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.
ABSTRACT
In this paper the adsorption properties of thermally sputtered calcein thin films towards water and other polar molecules vapors are studied by different characterization techniques: quartz crystal microbalance, surface plasmon resonance and visible spectroscopy. Sensitivity of calcein thin films to water vapors resulted much higher as compared with those of a number of dyes whose structure was close to that of calcein. All types of sensors with calcein coatings have demonstrated linear concentration dependences in the wide range of water vapor pressure from low concentrations up to 27,000 ppm (close to saturation). At higher concentrations of water vapor all sensors demonstrate the abrupt increase of the response (up to two orders). A theoretical model is advanced explaining the adsorption properties of calcein thin films taking into account their chemical structure and peculiarities of molecular packing. The possibility of application of thermally sputtered calcein films in sensing technique is discussed.
