Exploitation of thermo-effect of rhodamine B entrapped in sol–gel matrix and silica gel for temperature detection

In the present work, optical temperature sensors were prepared using a fluorescent dye, rhodamine B and different adsorbents, viz. silica gel and sol–gel. Silica gel (28–200 mesh) and a sol–gel consisting of a mixture of 3-amino-propyl-trimethoxy-silane (APTMS) and 3-glycidoxypropyl-tri-methoxy-silane (GPTMS) were used as the support matrices for the fluorescent dye. The polymerization of alkoxide silanes to produce a clear single phase sol–gel polymer at low temperature allows for the encapsulation of the fluorescence dye, and the rigidity of the silica gel prevents the movement and interaction of intermolecules, while still allowing them to retain their activity. The linear detection ranges of the fiber optic temperature sensors (FOTS) were between 10–95 °C and 0–60 °C when using silica gel and sol–gel as the support materials, respectively. The planar optic temperature sensors (POTS) showed high sensitivity in the temperature range of 25–40 °C. The interferences and life-time of the temperature sensors were also investigated.