Fullerene (C20) as a potential adsorbent and sensor for the removal and detection of picric acid contaminant: DFT Studies

Picric acid is a nitrophenol environmental contaminant that has adverse effects on the environment and the health of humans. Therefore, its removal and detection are very important. In this respect, infra-red (IR), natural bond orbital (NBO) and frontier molecular orbital (FMO) computations were employed for estimating the performance of fullerene (C20) as a sensor and adsorbent for picric acid. The calculated values of adsorption energy, Gibbs free energy changes and enthalpy variations showed picric acid adsorption on the surface of fullerene is experimentally possible, exothermic and spontaneously. In the adsorption process, the specific heat capacity of fullerene increased from 152.495 to 361.224 J/Mol.K but its bandgap declined -39.039% from 7.145 (eV) to 4.356 (eV) that indicated the thermal and electrical conductivity of fullerene enhanced remarkably when picric acid was adsorbed on its surface and this nanostructure is a suitable sensing material for the construction of new thermal and electrochemical sensors. The influence of temperature was also checked out and the results showed picric acid interaction with C20 was more favorable in lower temperatures. The NBO computations showed picric acid interaction with fullerene was chemisorption. The FMO results showed the chemical hardness of picric declined after its interaction with fullerene and picric acid-C20 complexes were more reactive than pure picric acid. The electrophilicity and maximum transferred charge capacity indices demonstrated the tendency of picric acid towards electron decreased after it was adsorbed on the surface of fullerene and picric acid-fullerene complexes were less electrophile than pure picric acid. Other structural parameters were also discussed in detail.