Fig. 3.

How hybrid gel film thickness relates to the optical active area for sensing. a) Examples of polarized optical microscopy images obtained for the 15-μm- and 90-μm-thick films. b) The correlation between optically active area and measured thickness of the hybrid gel films (n = 3). c) Typical signals obtained from hybrid gel films with distinct thicknesses upon cycles of heptane exposure and recovery. d) Variation of signal baseline with the measured thickness of the hybrid gel films (n = 3).