Acoustic Levitation Engineered Au‐InSe Schottky Junctions for Single‐Molecule SERS Sensing

ABSTRACT Detecting single molecules with high sensitivity and specificity is of great scientific and practical interest. Surface‐enhanced Raman scattering (SERS) is an ultrasensitive molecular detection technique for single‐molecule detection. However, the fabrication of ultrasensitive single‐molecule SERS substrates remains a key goal. Herein, we report an acoustic levitation assisted containerless strategy to construct InSe‐Au Schottky junctions with robust interfacial bonding, achieving single‐molecule detection of zeptomolar level and an EF of 10 10 . The controllable acoustic radiation pressure inside the levitated droplet induced robust interfacial coupling of InSe‐Au Schottky junctions, which was verified by HAADF‐STEM etc. The bianalyte Poisson‐binomial statistical model confirmed single molecule origin of Raman signals. Linear relationship between detection probability and ultralow Rhodamine B (RhB) concentration was established. Single molecule SERS mapping directly visualized molecular adsorption sites, identifying strongly bonded junction interface as critical signal enhancement region. The enhancement mechanism is primarily attributed to chemical enhancement, wherein the built‐in electric field facilitates multiple photoinduced charge‐transfer pathways, while the localized surface plasmon resonance of Au couples with out‐of‐plane dipole of InSe to enhance light harvesting. This strategy is material‐generalizable, as demonstrated by WSe 2 /GaSe‐Au systems with attomolar limits. This work provides new insights into engineering strongly bonded heterojunctions for single‐molecule sensing devices.