Multi-Modal Thermodynamic Characterization of Water in Individual Carbon Nanotubes Across Extended Temperature Ranges

Understanding water's behavior in single-digit nanopores remains a fundamental challenge in chemical physics, with contradictions in reported phase transition temperatures reaching 100 K across different experimental and computational approaches. We are developing an integrated characterization platform that combines optical spectroscopy (Raman and photoluminescence) with electromechanical resonance and electrothermal measurements to probe thermodynamic properties of water confined in individual carbon nanotubes. The ultimate goal is to map phase diagrams of nanoconfined water as a function of temperature and confinement diameter. This talk will present our progress in establishing this multi-modal infrastructure, addressing key instrumentation challenges in implementing complementary measurement techniques on isolated nanotubes. Recent advances include development of electrothermal methods—validated on micrometer-diameter wires across vacuum to atmospheric pressure conditions—toward implementation on individual carbon nanotubes. We will present new optical spectroscopy data from individual empty and water-filled nanotubes over an unprecedentedly broad temperature range, providing a more holistic understanding of water in individual CNTs than was previously accessible. This foundational work addresses the critical need for multi-probe experimental approaches capable of resolving ambiguities in interfacial water characterization, with broader implications for atmospheric chemistry, materials science, and astrochemical processes where confined aqueous environments play central roles.