Synthesis, characterizations of chitosan-pyridoxal aldehyde polymer derivatives for ammonia sensing

Document Type : Original Article


1 Faculty of Science, Chemistry Department, Al-Azhar University, Cairo, 11884,Egypt

2 Department of Chemistry, Faculty of Science, South Valley University, Qena, 83523, Egypt.

3 Department of Chemistry, Faculty of Science, South Valley University, Qena, 83523, Egypt


In the present work, some new chitosan polymers were prepared as a potential sensor for toxic gas. Chitosan (Chs) was reacted with pyridoxal (pyr) to give the corresponding Schiff-base, which was introduced into β-Cyclodextrin (β-CD) to form the inclusion complex (pseudopolyrotaxane) Chs-Pyr/β-CD. The modification and enhancement of the synthesized Schiff-base polymer was achieved by doping with ZnO NPs to form Chs-Pyr/ZnO composite. The chemical structure of the obtained polymers was confirmed by FT-IR spectra. The phase structure, crystallinity value and crystal size of chitosan and Chs-Pyr polymers were examined by XRD technique and indicated that crystallinity was enhanced from 5 to 13 % in Chs-Pyr, and Chs-Pyr/β-CD, respectively. In addition, the morphological structure of the prepared polymers was investigated by SEM analysis. The optical analysis was studied to confirm the difference in optical properties between the polymers, as well as changes in the energy gaps. Thermal stability studies indicated enhancement of T50 values to be 271, 291, and 299.8 C for Chs-Pyr Schiff base, Chs-Pyr/-CD, and Chs-Pyr/ZnO NPs, respectively. It was noticed that the prepared Chs-Pyr/ZnO NPs composite has high sensitivity for the detection of NH3 vapor from 10 to 100 ppm due to the bulky structure of the pyridoxal molecule which produces porous structure. Also, Chs-Pyr/ZnO composite has high response and quick recovery time (589 s and 264 s) towards the detection of NH3 vapors down to 10 ppm concentration.