Title:	Photoinduced modulation of refractive index in Langmuir-Blodgett films of azo-based H-shaped liquid crystal molecules
Authors:	Joshi, Ashutosh Gayakwad, Akash Manjuladevi, V. Varia, Mahesh C. Kumar, Sandeep Gupta, R.K.
Keywords:	Langmuir-Blodgett (LB) films Trans–cis transformation Refractive index Surface plasmon resonance (SPR) Photoinduced
Issue Date:	15-Oct-2022
Publisher:	Elsevier B.V.
Citation:	Journal of Molecular Liquids, 2022, Vol. 364, p120071
Abstract:	The development of optically active area consisting of organic molecules are essential for the devices like optical switches and waveguides, as it can be easily maneuvered by the application of suitable electromagnetic (EM) waves. In this article, we report the development of a photoactive surface by the deposition of a single layer of Langmuir-Blodgett (LB) film of a novel H-shaped liquid crystal (HLC) molecule. The synthesized HLC molecules possess azo-groups and nitro-groups. The azo-group can be isomerized (trans–cis transformation) by irradiating them with ultraviolet (UV) light. The nitro-group can provide sufficient amphiphilicity to the HLC molecules to form a stable Langmuir monolayer at air–water interface. The Langmuir monolayer of the HLC molecules exhibited gas and liquid-like phases. A single layer of LB film of HLC molecules was deposited on a gold chip of a home-built surface plasmon resonance (SPR) instrument. The azo-groups of the molecules in LB film was excited by UV irradiation leading to a change in morphology due to trans–cis transformation. Such a change in morphology can lead to a miniscule change in refractive index (RI) of the LB film. SPR is a label free and highly sensitive optical phenomenon for the measurement of such changes in RI. In our studies, we found systematic changes in the resonance angle of the LB film of HLC molecules as a function of intensity of the UV irradiation. We measured switch-on and switch-off intensity which may suggest that the LB film of HLC molecules can find applications in optical switches or waveguides.
Description:	Restricted Access.
URI:	http://hdl.handle.net/2289/7996
ISSN:	0167-7322
Alternative Location:	https://doi.org/10.1016/j.molliq.2022.120071
Copyright:	2022 Elsevier B.V.
Appears in Collections:	Research Papers (SCM)

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