Low-dimensional van der Waals (vdW) materials can harness tightly confined polaritonic waves to deliver unique advantages for nanophotonic biosensing. The reduced dimensionality of vdW materials, as in the case of two-dimensional graphene, can greatly enhance plasmonic field confinement, boosting sensitivity and efficiency compared to conventional nanophotonic devices that rely on surface plasmon resonance in metallic films. Furthermore, the reduction of dielectric screening in vdW materials enables electrostatic tunability of different polariton modes, including plasmons, excitons, and phonons. One-dimensional vdW materials, particularly single-walled carbon nanotubes, possess unique form factors with confined excitons to enable single-molecule detection as well as in vivo biosensing.
Fig: Specialized applications for metal nanoplasmonic sensors: a Real-time label-free plasmonic detection of single-molecule binding events. Wide-field imaging of hundreds of single gold nanorods enables multiplex single-molecule sensing. Reprinted from permission.b Plasmonic gold nanorods coupled to a whispering gallery mode resonator were used to monitor DNA/polymerase interactions. Reprinted from permission. c Lipid nanovesicles localized inside gold nanohole plasmonic sensors can be used for studying membrane-mediated biorecognition events. Reprinted from permission. d Nanohole arrays can be used as nanofluidic channels. In this “flow-through” sensing scheme, the response time can be improved compared with the conventional “flow-over” approach. Adapted from permission. eGold nanohole array plasmonic sensor is integrated with microfluidics for in situ detection of cell-secreted molecules. f Electron micrograph of a single cell attached to the gold nanohole array. g Sideview schematic of the system. h Measured binding kinetics of cytokines secreted from a single cell inside a microfluidic chamber. Reprinted from permission.
We discuss basic sensing principles based on vdW materials, followed by technological challenges such as surface chemistry, integration, and toxicity. Finally, we highlight progress in harnessing vdW materials to demonstrate new sensing functionalities that are difficult to perform with conventional metal/dielectric sensors.
Oh, SH., Altug, H., Jin, X. et al. Nanophotonic biosensors harnessing van der Waals materials. Nat Commun 12, 3824 (2021). https://doi.org/10.1038/s41467-021-23564-4