Electronic and spectral characteristics of pyrrole adsorption on Al₁₂N₁₂ and Al₁₂P₁₂ nanocages: A DFT-based sensing assessment

This work presents a comprehensive Density Functional Theory (DFT) investigation of the adsorption behavior of two pyrrole derivatives (PYI and PYII) on Al12N12 and Al12P12 fullerene-like nanocages, aiming to evaluate their suitability for sensing and drug-delivery applications. Geometry optimization, adsorption energy calculations, electronic structure analysis, molecular descriptors, and solvent effects were examined using the wB97XD/SDD level of theory. Both PYI and PYII exhibit spontaneous, exothermic, and chemisorptive binding onto the nanocages, with the presence of a strong adsorption observed for PYII and for Al12P12, particularly in aqueous media. Adsorption induces pronounced charge distribution, reduction of HOMO-LUMO gaps, increase in dipole moment and polarizability, and significant modulation of frontier orbital distribution, all indicating enhanced electronic reactivity and stronger surface interactions. UV-Vis and Raman analyses further reveal marked red shifts, reduced absorption intensities, and surface-enhanced Raman scattering (SERS)-active vibrational enhancements, confirming strong coupling between the pyrroles and the nanocages. Natural Bond Orbital (NBO) and Reduced Density Gradient (RDG) analyses highlight dominant hyperconjugative interactions and mixed attractive/van der Waals contributions stabilizing the adsorbed complexes. Molecular docking with acetylcholinesterase (1EVE) demonstrates substantially improved binding affinities for the adsorbed systems compared to the isolated pyrroles, suggesting potential for targeted therapeutic delivery. Collectively, these findings, identify Al-based nanocages as promising candidates for pyrrole sensing, photocatalytic enhancement, and drug-carrier applications.