# DFT and QTAIM insights into C20 fullerene derivatives as advanced sensors for phencyclidine drug detection in clinical settings

## TL;DR

This paper explores using doped C20 fullerenes, especially AlC19, as advanced sensors for detecting the drug phencyclidine (PCP) in clinical settings.

## Contribution

The study introduces AlC19 as a novel multifunctional sensor material for PCP detection through theoretical modeling.

## Key findings

- AlC19 shows the strongest interaction with PCP, with an adsorption energy of -49.44 kcal/mol.
- AlC19 acts as an effective electrochemical and colorimetric sensor for PCP detection.
- QTAIM and NBO analyses confirm strong donor-acceptor interactions in the AlC19@PCP complex.

## Abstract

The unauthorized use of phencyclidine (PCP) has serious public health consequences, which prompts the need for new sensing approaches that are fast, sensitive and accessible. This study used Density Functional Theory (DFT) and the Quantum Theory of Atoms in Molecules (QTAIM) to examine pristine fullerene C20 and two doped ones (AlC19 and ZnC19) as new sensors for PCP. Geometry optimization and analyses of the molecular electrostatic potential (MEP), electronic properties (HOMO-LUMO gap; chemical potential, electrophilicity-based charge transfer), and sensing performance (adsorption energy, recovery time and electrical conductivity) were performed. Results illustrate that doping significantly changes the electronic and structural properties of the C20 framework. Although pristine C20 and ZnC19 have limited potential, AlC19 is promising as a multifunctional material. AlC19 has the strongest interaction with PCP, with an adsorption energy (Eads) of -49.44 kcal.mol-1, demonstrating excellent potential to remove PCP in adsorbed form. As an electrochemical sensor, AlC19 showed a large increase in electrical conductivity (from 2.71 × 109 in the pristine AlC19 to 2.77 × 109 in the AlC19@PCP complex) and a long recovery time after PCP binding, making it ideal for disposable sensor application (strong and irreversible binding). Furthermore, AlC₁₉ showed exceptional performance as a colorimetric sensor, exhibiting a significant shift in the UV-Vis absorption maximum (from 470 nm to 524 nm) after complexation with PCP. Both NBO and QTAIM analysis revealed that AlC19@PCP exhibits a very strong donor-acceptor interaction and a moderate hydrogen-bond-like character, which contributed to its strong performance. All of the above establishes that AlC19 is an effective disposable electrochemical sensor, a colorimetric sensor, and an effective adsorbent of PCP that can be further utilized to develop a multi-functional sensing system that could allow for detection of the drug and remediation of the environment.

The online version contains supplementary material available at 10.1038/s41598-025-29996-y.