Nanoarchitectonics of Biofunctionalized Hydrogen-Terminated 2D-Germanane Heterostructures as Highly Sensitive Biorecognition Transducers: The Case Study of Cocaine Drug

Hydrogen-terminated 2D-germanane (2D-GeH), as one inorganic 2D material akin to graphene, is attracting widespread interest owing to its predicted (opto)electronic properties. Nonetheless, the chemical reactivity of 2D-GeH requires further exploration to expand its real implementation. Herein, a simple and straightforward bottom-up biofunctionalization approach is reported aiming at providing the bases toward the robust design of 2D-GeH-based biorecognition systems with electrical readout. For this goal, 2D-GeH has been firstly functionalized with gold nanoparticles (Au-NPs) via an organometallic approach, followed by the covalent immobilization of a thiolated single-stranded DNA (ssDNA) aptamer via Au-S bond interactions. After an accurate material characterization, the resulting ssDNA/Au@GeH heterostructure is drop-casted on a fluorine-doped tin oxide (FTO) electrode for impedimetrically monitoring cocaine as a model drug. Interestingly, the aptamer–cocaine interactions hinder the interfacial electron-transfer process of the benchmark [Fe(CN)₆]^3−/4− redox marker with increasing concentration of the cocaine target, leading to a detection limit as low as 4.9 ± 0.1 aM, the lowest one reported in literature by far. Overall, the ssDNA/Au@GeH electrochemical biosensor exhibits outstanding selectivity, specificity, and reproducibility, demonstrating the potential use of 2D-GeH as an emerging highly sensitive transducer for biosensing applications. The reported method is general and might be simply customized by tailoring the biorecognition component.