Evaluation of form birefringence in chiral nematic mesoporous materials

We present a detailed investigation into the form birefringence of chiral nematic mesoporous materials templated by the self-assembly of cellulose nanocrystals as the potential basis to detect changes in refractive index in an optical sensor using circular dichroism (CD) spectroscopy. The behavior is in excellent agreement with a model of form birefringence in a chiral nematic structure. We characterize the variability introduced by the self-assembly of the biologically-derived cellulose nanocrystals, which can partially be accounted for through normalization to address reproducibility in thickness and helical pitch within each sample. As one potential application, we show that the refractive index performance of these materials is maintained in strongly absorbing solutions due to the chiral nature of the form birefringence.

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