DFT-Driven SERS Insight into Epoxycyclohexane (CHO) Adsorption on Ag20, Au20 and Cu20 Nanoclusters for Sensing Applications

Epoxycyclohexane (CHO: 7-oxabicyclo[4.1.0]heptanes) is an industrially relevant epoxide, and sensitive detection of such volatile organic compounds remains an important analytical need. In this study, we used density functional theory (Gaussian16, B3LYP/def2-TZVPPD with dispersion correction) to examine how CHO interacts with pyramidal Ag[Formula: see text], Au[Formula: see text]and Cu[Formula: see text] nanoclusters and to connect the adsorption mechanism with key descriptors relevant to Surface-Enhanced Raman Scattering (SERS) and chemiresistive sensing. The calculations indicate that CHO preferentially binds through its epoxide oxygen, accompanied by charge redistribution at the interface. Adsorption is thermodynamically favorable on all three clusters, with adsorption energies of −17.53 (Ag[Formula: see text]CHO), −22.37 (Au[Formula: see text]CHO) and −25.60 kcal mol[Formula: see text] (Cu[Formula: see text]CHO), pointing to the strongest affinity for Cu[Formula: see text]. Complexation also increases dipole moments (to 4.55–5.56 D) and polarizability, consistent with stronger interfacial polarization upon binding. Frontier-orbital analysis shows modest but clear electronic softening after adsorption: the energy gaps decrease from 2.53–3.01 eV (bare clusters) to 2.24–2.81 eV (complexes), supporting improved charge-transfer propensity, an important factor for SERS enhancement and sensing response. Finally, recovery time estimates suggest that desorption can remain feasible under appropriate conditions, enabling practical sensing cycles while maintaining strong analyte-surface interactions. Overall, the results identify Cu[Formula: see text] as the most strongly interacting platform for CHO capture, while Ag[Formula: see text] and Au[Formula: see text] offer comparatively weaker binding that may benefit faster recovery.