Optical sensing of organic vapour based on polymer cholesteric liquid crystal film

ABSTRACT

A simple, low-cost, and quickly reversible sensor based on polymer cholesteric liquid crystal film (PCLCF) for detecting organic vapour is proposed in this work. PCLCF exhibits an obvious red shift of the reflective colour in the early stages of acetone vapour diffusion and has the ability to quickly recover as vapour is released. The red shift in the transmittance spectrum is attributed to pitch swelling of the PCLCs. The acetone-induced pitch change and response time of the PCLCs, which have been quantitatively characterised, increase with the amount of the adsorbed acetone vapour. This work also revealed a strong correlation between the morphology of the PCLCF and the pitch variation of the helical configuration when subjected to organic vapour. Based on the experimental results, the proposed sensor has the potential to be used for portable and real-time monitoring of organic vapour.

GRAPHICAL ABSTRACT

KEYWORDS:

• Polymer cholesteric liquid crystal
• pitch
• vapour sensor

Acknowledgments

The authors also sincerely acknowledge BASF Taiwan Ltd. for providing the reactive mesogen and chiral dopant monomer materials.

Disclosure statement

No potential conflict of interest was reported by the authors.

Additional information

Funding

This research was supported by grants from the Ministry of Science and Technology, Taiwan [MOST 107-2221-E-239-027-].