In this work, we report the synthesis of electrically conductive polycarbazolezirconium(IV)phosphate (PCz-ZrP) cation exchange nanocomposite as a new sensing material.Zirconium(IV)phosphate (ZrP) assisted in-situ chemical oxidative polymerization of carbazole was used for the synthesis of PCz-ZrP. Field emission scanning electron microscopy, Fourier Transform infrared spectroscopy, thermogravimetric analysis and X-ray diffraction analysis were applied to characterize the PCz-ZrP cation exchange nanocomposite. Strong interactions between inorganic particles (ZrP) and organic polymer (PCz) were observed. Thermogravimetric analysis revealed that the PCz-ZrP nanocomposite had higher thermal stability than pure PCz.Besides, the composite showed good ion-exchange capacity, electrical conductivity and isothermal stability in terms of DC electrical conductivity retention under ambient conditions below 100 o C. A nanocomposite based sensor was fabricated for the aqueous ammonia sensing at room temperature. An increase in resistivity on exposure to ammonia at room temperature was observed with a direct relationship between responses and ammonia concentration. The PCz-ZrP nanocomposite based sensor showed quick and reversible response towards aqueous ammonia. Fig. 4 (a-c) and (a'-c') shows the FE-SEM images and corresponding 3D surface maps of PCz, ZrP and PCz-ZrP nanocomposite, respectively. Granular morphologies of PCz and ZrP are shown in Fig. 4a and Fig. 4b, respectively. PCz-ZrP nanocomposite displayed a different morphology compared to the precursor components (PCz and ZrP). At ZrP surface, which possess a dense and global structure, PCz deposits are clearly visible. Hence, a clear indication that the polymerization of PCz was effectively performed on ZrP particles was confirmed by XRD, FTIR, and FE-SEM studies. Scheme 1(b) shows a graphic illustration of the formation of PCz-ZrP nanocomposite.Fig. 4. FE-SEM images of (a) PCz, (b) ZrP and (c) PCz-ZrP cation exchange nanocomposite and 3D surface area maps of (a') PCz, (b') ZrP, and (c') PCz-ZrP nanocomposite. 21 by compensation or electrical neutralization of the polymer backbone, are the two processes in operation.
Scheme: 2.A perspective view of the interaction of ball and stick models of ammonia with the energy-minimized structure of polymer created through molecular modeling by MOPAC programme of Chem Draw Ultra 3D. This interaction is supposed to be responsible for the electrical compensation of PCz with ammonia in PCz-ZrP nanocomposite. Atom colour notations are: carbon (battleship grey), hydrogen (white) and nitrogen (blue).