When water is confined to nanocavities, its quantum mechanical behavior can be revealed by terahertz spectroscopy. We place H2O molecules in the nanopores of a beryl crystal lattice and observe a rich and highly anisotropic set of absorption lines in the terahertz spectral range. Two bands can be identified, which originate from translational and librational motions of the water molecule isolated within the cage; they correspond to the analogous broad bands in liquid water and ice. In the present case of well-defined and highly symmetric nanocavities, the observed fine structure can be explained by macroscopic tunneling of the H2O molecules within a six-fold potential caused by the interaction of the molecule with the cavity walls.
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ACS Photonics
December 2024
School of Physics and Astronomy, University of Birmingham, Birmingham B15 2TT, U.K.
Tightly confined plasmons in metal nanogaps are highly sensitive to surface inhomogeneities and defects due to the nanoscale optical confinement, but tracking and monitoring their location is hard. Here, we probe a 1-D extended nanocavity using a plasmonic silver nanowire (AgNW) on mirror geometry. Morphological changes inside the nanocavity are induced locally using optical excitation and probed locally through simultaneous measurements of surface enhanced Raman scattering (SERS) and dark-field spectroscopy.
View Article and Find Full Text PDFSci Adv
December 2024
Department of Materials Science and Engineering, University of Maryland, College Park, MD 20742, USA.
A fundamental requirement for photonic technologies is the ability to control the confinement and propagation of light. Widely used platforms include two-dimensional (2D) optical microcavities in which electromagnetic waves are confined in either metallic or distributed Bragg reflectors. Recently, transition metal dichalcogenides hosting tightly bound excitons with high optical quality have emerged as promising atomically thin mirrors.
View Article and Find Full Text PDFJ Chem Phys
December 2024
Yusuf Hamied Department of Chemistry, University of Cambridge, Cambridge CB2 1EW, United Kingdom.
Water confined in nanoscale cavities plays a crucial role in everyday phenomena in geology and biology, as well as technological applications at the water-energy nexus. However, even understanding the basic properties of nano-confined water is extremely challenging for theory, simulations, and experiments. In particular, determining the melting temperature of quasi-one-dimensional ice polymorphs confined in carbon nanotubes has proven to be an exceptionally difficult task, with previous experimental and classical simulation approaches reporting values ranging from ∼180 K up to ∼450 K at ambient pressure.
View Article and Find Full Text PDFNanophotonics
February 2024
State Key Laboratory of Precision Spectroscopy, School of Physics and Electronic Science, East China Normal University, Shanghai 200241, China.
By confining light into a deep subwavelength scale to match the characteristic dimension of quantum emitters, plasmonic nanocavities can effectively imprint the light emission with unique properties in terms of intensity, directionality, as well as polarization. In this vein, achiral quantum emitters can generate chiral photons through coupling with plasmonic nanocavities with either intrinsic or extrinsic chirality. As an important metric for the chiral-photon purity, the degree of circular polarization (DCP) is usually tuned by various scattered factors such as the nanocavity design, the emitter type, and the coupling strategy.
View Article and Find Full Text PDFAnal Chem
September 2024
College of Food Science and Engineering, Northwest A&F University, 22 Xinong Road, Yangling, Shaanxi 712100, China.
Efficient field enhancement effects through plasmonic chemistry for ultrasensitive biosensing still face a great challenge. Herein, nanoconfinement engineering accumulation and synergistic effects are used to develop a "plasmonic storms" strategy with a high field enhancement effect, and gold nanoparticles (AuNPs) are used as active sites for a proof of concept because of their distinctive localized surface plasmon resonance and neighborly coupled electromagnetic field. Briefly, a large number of AuNPs are selectively and accurately stacked in the confined nanocavity of the bowl-like nanostructure through an in situ-synthesized strategy, which provides a space for strong coupling of electromagnetic fields between these adjacent AuNPs, forming "plasmonic storms" with an enhanced field that is 3 orders of magnitude higher than that of free AuNPs.
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