Quantum simulation and experimental characterization of gold nanorods for DNA sensing applications

Abstract

DNA biosensors based on AuRD present a viable engineering solution to the problems of attaining high sensitivity, selectivity, and economical scalability for molecular diagnostics. In order to develop and optimize AuRD-DNA interactions for sensing applications, this study combines time-dependent density functional theory (TDDFT) with experimental ultraviolet–visible (UV–Vis) spectroscopy. A detection limit of 1.67 µmol/L for target DNA sequences was demonstrated experimentally by UV–Vis analysis, which showed a considerable drop in transverse (1.164 to 0.921 Å) and longitudinal (0.467 to 0.150 Å) localized surface plasmon resonance (LSPR) absorbance upon DNA binding. The sensitivity of 0.009 µmol/L rivals electrochemical techniques and outperforms traditional fluorescence-based without requiring complicated instrumentation.The rCAM-B3LYP range-separated TDDFT method provided computational insight into key electronic properties for sensor design: selective DNA-AuRD binding driven by electrostatic complementarity was revealed by molecular electrostatic potential maps, and electron transfer kinetics were improved by a reduced HOMO-LUMO gap (from 2.63 eV to 2.34–2.67 eV upon DNA binding). The nonlinear optical characteristics of AuRD, such as its redshifted λ_max and 6.33 eV vertical ionization potential, which are correlated with enhanced plasmonic responsivity, were confirmed by the combined experimental and theoretical approach. This work advances the logical design of plasmonic biosensors for quick, label-free DNA detection with sub-nanomolar sensitivity by tackling three important engineering challenges: interfacial charge transfer, signal stability, and nanomaterial monodispersity.