Black phosphorene/graphene heterostructures as high-performance SERS platforms for ultrasensitive label-free DNA nucleotides detection

Surface-enhanced Raman scattering (SERS) based on two-dimensional materials offers a route toward ultrasensitive and non-destructive biomolecular detection; however, achieving strong and tunable enhancement remains challenging. Here, we report the first demonstration of black phosphorene (BP)-based van der Waals heterostructures, namely, BP/graphene (BP/Gr) and BP/molybdenum disulfide (BP/MoS2), as highly efficient SERS substrates for DNA nucleotide detection. Both heterostructures exhibit markedly enhanced Raman signals compared to their individual two-dimensional constituents, with BP/Gr showing the highest sensitivity. The enhancement arises from synergistic interfacial charge transfer, amplified by BP's in-plane anisotropy, which promotes molecular adsorption and dipole interactions. Hall-effect measurements with controlled molecular adsorption on graphene reveal, for the first time, a quantitative correlation between charge transfer and the SERS response, with adenine inducing n-type and thymine p-type doping. In situ Raman spectroscopy under applied electrical bias shows potential-dependent nucleotide adsorption, enabling tunable molecule-surface interactions. These findings establish BP-based heterostructures as ultrasensitive label-free biosensing platforms and clarify the role of charge-transfer mechanisms in two-dimensional systems.