Design and investigation of non-invasive lung cancer VOC biomarker detection on Ag-doped penta-PdSe₂ monolayer: A comprehensive DFT study with vDW correction

The Early screening of volatile organic compounds (VOCs) linked to lung cancer (LC) is essential for advancing non-invasive diagnostic methods. This work employs Density Functional Theory (DFT) incorporating Grimme’s DFT-D3 dispersion corrections, to study the adsorption and sensing characteristics of pristine and Ag-doped PdSe₂ monolayers toward four LC-related VOC biomarkers: isoprene (C₅H₈), acrolein (C₃H₄O), isobutyraldehyde (C₄H₈O), and propan-1-ol (C₃H₈O). Pristine PdSe₂ exhibits a 1.20 eV bandgap and strong Pd-Se orbital hybridization, while Ag substitution at Se sites reduces the bandgap to 0.68 eV, introducing localized states that enhance electrical responsiveness. Adsorption studies reveal strong affinities (-1.33 to -1.72 eV), moderate charge transfer (-0.01 to -0.13 e ), and adsorption distances of ∼2.2–2.3 Å. Notably, C₅H₈ induces a significant bandgap modulation (0.68 to 0.79 eV), highlighting its strong sensing response. Ab initio molecular dynamics (AIMD) simulations at 300 K confirm the thermal stability of both pristine and Ag-PdSe₂ monolayers. Work function (WF) analysis indicates that C₅H₈, C₄H₈O, and C₃H₈O reduce the WF, enhancing electron emission, while C₃H₄O slightly increases it, hindering transport. Current-voltage (IV) characteristics demonstrate selective detection, with C₅H₈ (74.4 %) and C₃H₈O (70.38 %) exhibiting the highest sensitivities at 1.5 V bias, whereas C₃H₄O and C₄H₈O remain below 40 %. These findings establish Ag-PdSe₂ as a robust and selective 2D material platform for Field Effect Transistor (FET)-type chemiresistive sensors, offering significant potential for non-invasive lung cancer diagnosis.