Advances in Scanning Tunneling Microscope Break Junctions for Single‐Molecule Detection: From Ion Sensing to Intelligent Analysis

Single‐molecule recognition and detection can overcome the limitations of ensemble‐averaged measurements by revealing molecular heterogeneity, transient interactions, and low‐abundance analytes at the individual‐molecule level. The scanning tunneling microscope break junction (STM‐BJ) technique enables the repeated formation of metal–molecule–metal junctions and converts molecular structures, interactions, and interfacial processes into statistically analyzable conductance signals. Therefore, STM‐BJ not only provides a powerful tool for probing single‐molecule electron transport but also offers a label‐free, low‐sample‐consumption, and ultrasensitive electrical sensing strategy. This review summarizes recent advances in STM‐BJ‐based single‐molecule sensing, focusing on ion detection, biomolecular recognition, and organic small‐molecule analysis. Representative applications involving metal ions, halide ions, pH sensing, nucleic acids, proteins, carbohydrates, explosives, pesticides, and dyes are discussed. We also highlight the integration of artificial intelligence with STM‐BJ for conductance‐trace analysis, complex signal recognition, and molecular‐scale intelligent devices. Finally, current challenges, including detection reliability, statistical standardization, complex sample adaptability, and instrument integration, are discussed, together with future perspectives on intelligent single‐molecule analysis and ultrasensitive chemical sensing.