Tuning Localized Excitonic States in TEA ⁺ ‐Intercalated MoS ₂ for Near‐Field Enhancement

ABSTRACT Atomically thin transition metal dichalcogenides exhibit strong excitonic effects and rich light–matter interactions, yet active control over their optical near‐field response remains challenging. Here, we demonstrate an intercalation‐enabled strategy to tune the near‐field response of MoS 2 through electrochemical insertion of tetraethylammonium ions. The resulting (TEA) x MoS 2 exhibits a markedly expanded interlayer spacing (12.17 Å) and substantial reconstruction of its electronic, dielectric, and excitonic properties. Steady‐state and ultrafast spectroscopy reveal redshifted and intensified excitonic resonances, a more pronounced monolayer‐like emission response, and prolonged excitonic bleach dynamics after intercalation. Consistently, nano‐optical imaging shows a substantially enhanced near‐field response. Combined optical analyses support an intercalation‐modified exciton‐coupled near‐field mode rather than a conventional plasmonic origin. Consequently, (TEA) x MoS 2 enables molecular detection down to 10 −9 m , establishing electrochemical intercalation as a practical route for excitonic near‐field engineering in van der Waals semiconductors.