Development of a reusable colorimetric calcium sensor based on a calixarene-functionalized glass surface
MetadataShow full item record
A dual functional chromogenic calixarene, which contains both hydroxy azophenols and triazoles for colorimetric sensing and cationic recognition, respectively, has been synthesized. This system was further functionalized with dimethallylsilane to permit grafting to a glass surface. This grafting may be used to produce a surface modified glass slides that act as reusable ion-selective colorimetric sensors. UV/Vis spectral studies revealed that this compound is capable of binding the calcium cation in aqueous media and producing an easily detectable color change. The same is true for the modified surface setup. For the free receptor in acetonitrile solution, the absorption maximum undergoes a red shift from 390 nm to 496 nm upon exposure to calcium cations. In the case of the modified surface, exposure to acetonitrile solution of calcium perchlorate leads to a change in color from orange to red. Washing with acetone serves to remove the metal cations from the calixarene-functionalized glass and restore the original orange color. The system is then ready for reuse. Specifically, following treatment with acetone, the glass may be submerged in a metal solution once again. In the case of exposure to calcium salts, this re-exposure results in a color change analogous to what was seen for a pristine system. In accord with design expectations, this process may be repeated several times. On the basis of this reproducibility, we think this system meets the reusability requirements necessary for the development of a practical sensor device.