Multidimensional imaging reveals mechanisms controlling label-free biosensing in vertical 2DM-heterostructures

TL;DR

This paper introduces a multidimensional optical imaging technique to map nanoscale strain and doping in 2D heterostructures, improving understanding and detection of biosensing mechanisms without labels.

Contribution

It develops a novel multidimensional imaging method to analyze local optical properties in 2D heterostructures, aiding biosensing device optimization.

Findings

Mapped sub-diffractional doping and strain distributions.

Demonstrated label-free detection of doxorubicin.

Linked optical variability to heterostructure properties.

Abstract

Two-dimensional materials and their van der Waals heterostructures enable a large range of applications, including label-free biosensing. Lattice mismatch and work function difference in the heterostructure material result in strain and charge transfer, often varying at nanometer scale, that influence device performance. In this work, a multidimensional optical imaging technique is developed in order to map sub-diffractional distributions for doping and strain and understand the role of those for modulation of electronic properties of the material. As an example, vertical heterostructure comprised of monolayer graphene and single layer flakes of transition metal dichalcogenide MoS$_2$ is fabricated and used for biosensing. Herein, an optical label-free detection of doxorubicin, a common cancer drug, is reported via three independent optical detection channels (photoluminescence shift, Raman shift and Graphene Enhanced Raman Scattering). Non-uniform broadening of components of multimodal signal correlates with the statistical distribution of local optical properties of the heterostructure. Multidimensional nanoscale imaging allows one to reveal the physical origin for such a local response and propose the best strategy for mitigation of materials variability and future device fabrication.