Temperature dependent dynamics of nanoconfined water at terahertz frequencies

Abstract

The dielectric properties of water confined at the nanoscale differ markedly from those of bulk water due to limited molecular mobility and altered hydrogen-bonding networks. In this study, tera- hertz time-domain spectroscopy (THz-TDS) was employed to investigate how temperature modulates the dielectric response of water under confinement within gold nanogap structures. As temperature in- creases, pronounced changes in transmitted amplitude and resonance frequency were observed within narrower gaps, exceeding the relative variation seen in wider nanogaps that more closely resemble bulk water behavior. These results suggest that temperature can partially alleviate the effects of nanoscale confinement, promoting increased dipolar mobility. While the system does not fully recover bulk-like dynamics, the enhanced temperature sensitivity in narrower gaps points to a thermally induced loosen- ing of confinement-driven constraints. These findings highlight that the structural ordering and dipolar suppression imposed by nanoconfinement are not entirely static, but can be modulated to some extent by thermal energy.