Impact of polypyrrole units (pyr*n; n=3, 5, 7, or 9) on the adsorption and excitation dynamics of enrofloxacin antibiotic interaction with hafnium-doped graphene/boron nitride (Hf@GP/BN) heterostructure: A theoretical perspective

This research work focuses on investigating on influence of pyrrole units (pyr) on the structural stability, reactivity, adsorption potential, bonding variation, and the visible-light interactions of enrofloxacin (xacin) antibiotic with hafnium-doped graphene/boron nitride (Hf@GP_BN) heterostructure within the framework of hybrid exchange-correlation functional and the Monte Carlo molecular simulations. The interaction of enrofloxacin (xacin) with the hybrid surface pyr*n_Hf@GP_BN (where n = 3, 5, 7, or 9) provided insights into the effects of changing the polypyrrole (pyr) chain length on the resulting interactions: xacin_pyr3_Hf@GP_BN, xacin_pyr5_Hf@GP_BN, and xacin_pyr7_Hf@GP_BN respectively to gain more efficient degradation capabilities and the influence of the increase polymer chain. The calculated energy gap decreases due to the increase in LUMO energy experienced upon the addition another of ring, nonetheless when the length of the polypyrrole was further adjusted to seven, the energy gap of the composite increased from 2.184 eV to 2.205 eV which is in the range of semi-conductor to support efficient electron excitation. Results of the molecular dynamic (MD) simulation reveal that while the potential energy of the system decreased for all pyr*n_Hf@GP_BN combinations, the magnitude of the potential energy reduction varied with different pyr chain lengths. Pyr3 exhibited the least reduction of 1310.899 +/- 36.119 kcal/mol, followed by 1402.128 +/- 38.678 for pyr5, 1511.129 +/- 40.494 for pyr7, and 1616.720 +/- 43.445 kcal/mol for pyr9, which displayed the most substantial reduction. Longer pyr chains (pyr7 and pyr9) seem to have stronger attractive interactions with enrofloxacin, leading to more significant energy reductions. This indicates that longer pyr chains are more effective in stabilizing the interactions between the antibiotic and the hybrid surface. While the UV-excitation analysis revealed that an increase in the polypyrrole chain length led to a decrease in the wavelength for both the adsorbent and the interactions, decreasing order of exciton binding energy is observed as: 0.602585, 0.606008, and 0.597378 for xacin_pyr3_Hf@GP_BN, xacin_pyr5_Hf@GP_BN, and axacin_pyr7_Hf@GP_BN respectively which is below the 1.9 eV benchmark of efficient materials for photodegradation. The findings could contribute to the broader field of photocatalysis, potentially informing the design of more effective photocatalytic materials. Therefore, research contributes to the development of more efficient methods for antibiotic degradation, with potential applications in environmental remediation.