The device was constructed in a cost-effective manner by incubating graphene sensor platforms in droplets of the ssDNA solution, where ssDNA molecules were immobilized on top of the graphene via π-π stacking interaction.
The team investigated the modulation of carrier density in the active graphene channel via electrostatic interaction with overlaying ssDNAs. They found that the single-stranded DNA-functionalized graphene (ssDNA-FG) sensors exhibit highly sensitive responses for amonia (NH3) and hydrogen sulfide (H2S) vapors, with the low detection limit of 103 ppb and 5.3 ppb, respectively, in a high relative humidity atmosphere.
These results show that the enhanced sensing ability is attributed to the effective modulation of not only the carrier density in graphene through negative-potential gating, but also the formation of an additional ion conduction path for proton hopping in the layer of H3O+ around ssDNA molecules.
By using principal component analysis (PCA), the researchers showed that ssDNA-FG sensor arrays can distinguish the halitosis and kidney disorder cancer related biomarkers, H2S and NH3 vapors, respectively.
Although this study is at a rather fundamental level, by focusing on simple cases of combinations of graphene and ssDNA molecules, the scientists succeeded in effectively demonstrating enhanced chemical vapor sensing at high humidity.
"Considering its selective vapor sensing capability in a high humidity condition, we expect that ssDNA-FG will provide a promising sensing platform for an inexpensive and noninvasive diagnostic tool to monitor halitosis and kidney disorder," the authors conclude their report..