Adsorption and reorientation of nematic on nano-dimensional carbon film induced by vapor of organic solvents

Author(s):  E.A. Valetova, Belgorod National Research University, Belgorod, Russia

D.A. Kolesnikov, Belgorod National Research University, Belgorod, Russia

S.I. Kucheev, candidate of Sciences, associate Professor, Belgorod National Research University, Belgorod, Russia,

Issue:  Volume 50, №1

Rubric:  Physics

Annotation:  The effect of dimethylformamide and acetone vapor on nematic 5CB oriented on the surfaces of silicon oxide and nano-dimensional carbon films obtained by an electron beam in a vacuum chamber of a scan-ning electron microscope is investigated. A cell geometry is proposed that allows the nematic layer and accordingly carbon films to be contacted with an increasing concentration of vapors of organic solvents. It is shown that for dimethylformamide there is a transition of the director from the initial orientation to the homeotropic state and the dependence of the onset of such a transition on the thickness of the nano-dimensional carbon film is observed. The transition to the homeotropic state is associated with the ad-sorption of dimethylformamide on the surface of carbon films. For acetone vapor, there is an increase in the birefringence of the nematic layer and the influence of carbon films is not fixed. The mechanism of the action of acetone vapor is apparently associated with a change in the surface tension of the nematic under the action of acetone molecules. A long period of "sensitivity" of the oriented nematic to dime-thylformamide has been noted which will take about 40 minutes (per drop of solvent) which considerably exceeds the "sensitivity" period of the gas analyzer of the person (nose). The possibility of determining the direction of the dimethylformamide vapor source is demonstrated. The fact of realization of the ad-sorption mechanism on nano-dimensional carbon films in the nematic layer is shown experimentally

Keywords:  sensor, liquid crystals, gas, carbon film, adsorption

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