A smart chitosan-graphite molecular imprinted composite for the effective trapping and sensing of dimethyl methylphosphonate based on changes in resistance

Abstract

A molecular imprinted polymer (MIP) fabricated from a chitosan doped with graphite to create a conductive composite (CG-MIC) with the ability to trap and detect dimethyl methylphosphonate (DMMP) through a change in resistance of the material has been successfully manufactured. The GC-MIC presented a maximum trapping capacity of 96 ppm (0.096 mg g⁻¹) of DMMP. A similar non-imprinted composite made of chitosan-graphite (CG-NIC) had a surface adsorption of 48 ppm (0.048 mg g⁻¹) of DMMP. The manufacturing process was tested for consistency and there were no significant differences in resistance between batches of CG-MIC before (around 450 Ω) and after (around 70 Ω) DMMP extraction, representing a homogeneous manufacturing process. Although Atomic Force Microscopy studies revealed that the graphite was not homogenously distributed throughout the chitosan matrix, the response was consistent. The changes in the concentration of DMMP within the self-sensing material, being proportional to those in gas concentration, could be followed by the changes in resistance. The inclusion of common interferents: Acetic acid, acetone, ethanol, ammonium hydroxide and 2-propanol, equivalent in concentration to the DMMP, caused a change in the resistance of the material but did not substantially affect the specific resistance response of the composite material. Based on this data, the CG-MIC could be used as a smart material with sensing capabilities to monitor trapping levels of DMMP.