Proposal of Nanometer-Resolved Photoluminescence Imaging with a Single-Molecular Probe Attached to the Tip in STM-Based Plasmon Picocavity

Single-molecule fluorescence imaging has emerged as an important tool for probing molecular interactions and energy transfer mechanisms. Recent experiments have demonstrated that single-molecule probes attached to the tip in scanning tunneling microscope (STM)-based picocavities can overcome fluorescence quenching and achieve measurable emission. Motivated by the experiment, we propose to achieve photoluminescence imaging beyond the optical diffraction limit. To verify our proposal, we apply a semiclassical theory to theoretically analyze fluorescence imaging under the laser excitation with ultralow intensities (50 μW/μm2), and find that the imaging resolution is below 1.5 nm. Furthermore, we also utilized a single PTCDA molecule as a probe for the mapping of a sample. Our results first confirm the possibility of photoluminescence imaging with ultralow laser intensity, thereby enabling nondestructive detection. Our proposal establishes a new approach to achieve nanometer-resolved photoluminescence imaging aside from super-resolution fluorescence microscopy and lays the theoretical foundation for the next generation of nondestructive detection technology.