Optical behaviour of pH detectors based on sol-gel technology

The optical response of the detectors was analysed by VIS absorption spectroscopy, since a change of colour took place when the detectors were submitted to different pH buffered solutions. With the aim to investigate their optical behaviour as a function of pH, several experimental measurements were undertaken: absorption intensity; maximum spectral wavelength; colour coordinates; colour purity percentages. Time response and memory effect were also studied. The detector operation conditions for monitoring environmental acidity both indoor and outdoor are discussed.