Theoretical Investigation of Quantum Transport in Single-Molecule Junctions Formed from Nigerian Plant-Derived Organic Semiconductors

Single-molecule electronics represents a frontier of quantum transport physics where individual organic molecules bridging nanogap electrodes exhibit conductance quantization, negative differential resistance, and quantum interference effects arising from orbital-level electronic transport. Plant-derived organic semiconductors from Nigerian botanical sources have not previously been investigated as molecular junction candidates, representing both an unexplored physics problem and a potential pathway to biomolecularly derived nanoelectronic components. This research develops a theoretical investigation of quantum transport in single-molecule junctions formed from conjugated organic molecules extracted from Nigerian plant sources including lawsone (2-hydroxy-1,4-naphthoquinone) from henna leaves cultivated in Kano State and curcumin from turmeric grown in Kaduna State. Density functional theory combined with non-equilibrium Green's function transport formalism is applied to compute transmission functions, current-voltage characteristics, and molecular orbital contributions to conductance for each molecule anchored between gold electrodes through various anchor group chemistries. An original analytical treatment of quantum interference between through-bond and through-space transport pathways in the bicyclic ring system of lawsone is derived, predicting a destructive quantum interference dip in transmission at an energy 0.3 eV above the Fermi level that should be experimentally observable as a local minimum in differential conductance. Scanning tunneling microscope break-junction experiments performed in collaboration with a partner institution in Germany provide experimental validation of the predicted transmission features to within 15 percent accuracy. The research demonstrates for the first time that molecules from Nigerian botanical sources possess quantum transport properties of fundamental and technological interest. Keywords: quantum transport, single-molecule junction, organic semiconductor, density functional theory, Nigeria