Two-dimensional Mo2B2Tx MBenes for selective sensing of disease-associated VOCs in cardiovascular diagnostics

Abstract

Cardiovascular disease is a leading cause of global mortality, driving the need for non-invasive early detection methods. Analysis of specific volatile organic compounds (VOCs) in exhaled breath, such as acetone, hexane, hexanal, isoprene, and pentane, offers a promising diagnostic pathway. However, the selective detection of these low-concentration VOC biomarkers remains a significant challenge. This study employs a combination of theoretical approaches, such as density functional theory (DFT), STM-based tunnelling model aligned with the Tersoff-Hamann approximation, and thermodynamic analysis via the Langmuir adsorption model, to assess the sensing capabilities of two-dimensional (2D) MBenes (Mo 2 B 2 T x ) monolayers toward the targeted VOCs. The results reveal that VOCs interact with the Mo 2 B 2 T x (T x = H, O, F) surface, exhibiting adsorption energies ranging from −0.18 eV to −1.00 eV, which vary with the VOC type and surface termination. This interaction alters the work function of Mo 2 B 2 T x , with sensitivity values ranging from approximately 5% to over 25%. Considerable changes in the electronic properties of Mo 2 B 2 T x are observed upon the adsorption of VOCs, which are studied through density of states, electrostatic potential, and work function analysis. Recovery times vary widely from 10 −9 s to 10 2 s at 300 K, depending on adsorption strength and surface termination, with only weakly adsorbed species exhibiting ultrafast desorption. Thermodynamic analysis using Langmuir isotherms confirmed large surface coverage of the VOCs at parts-per-million (ppm) concentrations. STM-based I-V simulations show strong VOC in Mo 2 B 2 T x , with acetone producing a clear tunnelling response, while hexane shows minimal interaction. Furthermore, the Mo 2 B 2 T x , particularly Mo 2 B 2 F 2 , retained adequate adsorption for hexanal in the presence of interfering air gases (CO 2 , NO 2 , H 2 O) and in an aqueous medium, as studied through a solvation model, providing preliminary evidence of selectivity under selected interfering gases. The results establish Mo 2 B 2 T x as a promising platform for developing high-performance nanosensors for the detection of specific VOCs related to cardiovascular disease.