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. Author manuscript; available in PMC: 2020 Feb 28.
Published in final edited form as: Sens Actuators B Chem. 2019;301:10.1016/j.snb.2019.127076. doi: 10.1016/j.snb.2019.127076

Figure 2.

Figure 2.

Top: UV-Vis absorption spectrum of RCP at pH 2.5 (gray) and 10 (black) with the excitation profile of the LED sources (green – 520 nm and red – 638 nm). Middle: FBG response (over time) due to light absorption by chromophores at a pH of 2.5. Left – response from red light excitation. Right – response from green light excitation. Bottom left: Absorbance value at 638 nm (solid red line) and measured FBG response (dashed red line) for the RCP solution as a function of pH. Bottom right: Absorbance value at 520 nm (solid red line) and measured FBG response (dashed red line) for the RCP solution as a function of pH.