Layered Aggregation with Steric Effect: Morphology-Homogeneous Semiconductor MoS2 as an Alternative 2D Probe for Visual Immunoassay.

Liquid-phase exfoliation routes unavoidably generate 2D nanostructures with inhomogeneous morphologies. Herein, thickness-dependent sorting of exfoliated nanostructures is achieved via a treatment of differential-zone centrifugation in the surfactant aqueous phase. With this approach, homogeneous MoS2 nanosheets are obtained, and due to the intrinsic semiconducting characteristics, those 2D nanosheets are endowed with desired optical properties, rivaling classic gold nanoparticles in sensing applications. Furthermore, MoS2 nanosheets with high uniformity and chemical inertness are coupled with proteins, exhibiting high performance in stability and anti-interferences for bioanalysis. As a consequence of aggregation-induced steric effect, distinguishing running shifts of antibody-anchored conjugates in gel electrophoresis are visually responsive to those specific antigens. This assay enables the easy and fast monitoring of tumor biomarkers just according to "naked-eye" identification of band location in electrophoresis results, which are presented by an alternative visual probe of 2D MoS2 -protein conjugates. The developed visual immunoassay with the synergistic effect of gel electrophoresis techniques and 2D semiconductors pushes significant progress in "home-made" tests for disease early diagnosis.