Zero-Dimensional Graphene-Core Carbon Nanodots Confined in Mesoporous Silica for π-Selective Extraction of Polycyclic Aromatic Hydrocarbons from Lipophilic Media

Abstract

A novel silica-based π-selective adsorbent decorated with graphene-core N-doped carbon nanodots (G-CNDs) was developed via an in situ confined synthesis strategy. This material was applied for solid-phase extraction (SPE) of polycyclic aromatic hydrocarbons (PAHs) from lipophilic matrices. The adsorbent was prepared by thermal treatment of ethylenediamine-modified mesoporous silica saturated with citric acid. This enabled preferential formation and covalent immobilization of G-CNDs within the silica pore network. The spatial confinement preserves the mesoporous structure, prevents nanoparticle aggregation. It provides a structurally bimodal adsorbent that combines π-active internal surfaces with a polar external silica surface. Comprehensive characterization by BET analysis, FTIR spectroscopy, SEM, AFM and X-ray photoelectron spectroscopy confirmed the formation of graphene-core carbon nanodots, their covalent binding to the silica framework, and the preservation of textural properties. The developed SiO₂/G-CNDs material exhibited pronounced selectivity toward PAHs due to strong multipoint π-π interactions, while suppressing non-specific adsorption of lipid matrix components. Under optimized SPE conditions, quantitative or near-quantitative recoveries were achieved for high-molecular-weight PAHs directly from nonpolar solvents such as hexane. In contrast conventional C18 sorbents showed negligible retention. Efficient desorption was accomplished using acetone, enabling direct GC-MS analysis. The approach allows PAH extraction from apolar and lipid-derived media without a saponification step and demonstrates the potential of 0D carbon nanomaterial-based hybrid adsorbents for selective analysis of PAHs in complex matrices. lipid-rich samples. Overall, the proposed SiO₂/G-CNDs material represents an effective π-selective SPE adsorbent and a promising strategy for the determination of PAHs in complex lipid-derived matrices. 5.