Commenced in January 2007
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Apochromism of 3,3’,5,5’-Tetramethylbenzidine-Tetrasilisicfluormica Intercalation Compounds with High Selectivity for Water and Acetonitrile

Authors: Reira Kinoshita, Shin'ichi Ishimaru

Abstract:

Vapochromism is a type of chromism in which the color of a substance changes when it exposed to the vapor of volatile materials and has been investigated for the application of chemical sensors for volatile organic compounds causing sick building syndrome and health hazard in work spaces. We synthesized intercalation compounds of 3,3',5,5'-tetramethylbenzidine (TMB), and tetrasilisicfluormica (TSFM) by commonly used cation-exchange method with the cation ratio TMB²⁺/CEC of TSFM = 1.0, 2.0, 2.7 and 5.4to investigate the vapochromism of these materials. The obtained samples were characterized by powder XRD, XRF, TG-DTA, N₂ adsorption, and SEM. Vapochromism was measured for each sample under controlled atmosphere by handy reflectance spectrometer directly from the outside of the glass sample tubes. The color was yellow for all specimens vacuum-dried at 50 °C, but it turned to green under H₂O vapor exposure for the samples with TMB²⁺/CEC = 2.0, 2.7, and 5.4, and to blue under acetonitrile vapor for all cation ratios. Especially, the sample TMB2+/CEC = 2.0 showed clear chromism both for water and acetonitrile. On the other hand, no clear color change was observed for vapors of alcohols, acetone, and non-polar solvents. From these results, this material can be expected to apply for easy detection of humidity and acetonitrile vapor in the environment.

Keywords: chemical sensor, intercalation compound, tetramethylbenzidine, tetrasilisicfluormica, vapochromism, volatile organic compound

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