Photoprocesses in 7-hydroxy coumarins molecules in solutions and SiO2 sol-gel films - Materials for optical chemical sensorics

The paper investigates the spectral properties of protolytic forms of three substituted 7-hydroxy coumarin molecules in aqueous ethanol solutions and SiO2 films. It explains spectral-and-luminescent properties of coumarins in the produced films. It is found that in aqueous ethanol solutions and sol-gel films, upon excitation in the S1 state, there is a reaction of proton phototransfer from the О-Н group of neutral coumarins molecules to the water molecule with development of anionic forms solvated by hydroxonium ions. We studied sensory properties of compounds in the films to the ammonia gas in terms of changes in their fluorescent properties and revealed the reasons causing such changes. We demonstrated the prospects of using films with one of the investigated coumarins as the ammonia gas sensitive material of an optical chemical sensor.