Dual excitation fluorescence-based sensors for pH and dissolved carbon dioxide monitoring

We report on high performance ratiometric fluorescence-based pH and dissolved carbon dioxide (dCO
₂
) sensors for use in bioprocess and environmental monitoring applications, respectively. Novel hybrid sol-gel-based sensor materials have been developed and successfully used as host matrices in pH and dCO
₂
sensing. These sensors are easy to prepare and miniaturise, low-cost in terms of fabrication, are mass-producible and when the combination of key performance parameters is considered, compare very well to similar sensor systems which have been reported in the literature in terms of resolution, stability and leaching characteristics. Both pH and dCO
₂
sensor films can be interrogated with a robust, ratiometric optical probe that combines effective fluorescence excitation and detection and thus facilitates the production of a highly-sensitive sensor system using low-cost optoelectronic components. In the probe configuration both LEDs are operated simultaneously, which represents a significant improvement over existing ratiometric systems where the light sources must by operated sequentially.