Liquid-Phase Near-Field Infrared Nanoscopy of Ion-Exchange Reactions
Abstract
In situ monitoring of reactions with chemical specificity and nanometer-scale spatial resolution under aqueous conditions remains a long-standing experimental challenge. Here, we use thin SiC membrane-enabled liquid-phase infrared nanoimaging and nanospectroscopy to monitor Ca2+/Na+ ion exchange in a mixture of disodium terephthalate and CaCl2 solution. Beneath the membrane, we follow the formation of calcium terephthalate (CaTP), a metal-organic framework (MOF)-type coordination phase in which terephthalate ligands link Ca2+ centers. The symmetric and asymmetric carboxylate stretching modes serve as chemically specific near-field reporters of Ca2+ coordination to the terephthalate linkers. Nano-FTIR spectra reveal pronounced peak shifts and linewidth changes in these vibrational modes, indicating modification of the carboxylate coordination environment during CaTP formation. Complementary near-field nanoimaging resolves the emergence of nanoscale precipitates beneath the SiC membrane following CaCl2 injection, providing spatially resolved evidence of the formation of the CaTP coordination framework. Solid-phase nanoimaging and nanospectroscopy identify well-defined CaTP particles, providing further evidence for crystalline CaTP formation. We demonstrate that the chemistry of metal-ligand interactions can be monitored in situ via liquid-phase near-field nanoscopy. This capability could enable the study of catalytic, electrochemical, and biological processes under native aqueous conditions.
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BibTeX
@misc{takele2026liquidphase,
title = {{Liquid-Phase Near-Field Infrared Nanoscopy of Ion-Exchange Reactions}},
author = {Wassie M. Takele and Teferi Sitotaw Yallew and Mason Caron and Yohannes Abate},
howpublished = {arXiv},
year = {2026},
month = sep,
doi = {10.48550/arxiv.2609.13493},
eprint = {2609.13493},
archivePrefix = {arXiv},
url = {https://arxiv.org/abs/2609.13493},
note = {CC BY 4.0},
}
RIS
TY - UNPB
TI - Liquid-Phase Near-Field Infrared Nanoscopy of Ion-Exchange Reactions
AU - Wassie M. Takele
AU - Teferi Sitotaw Yallew
AU - Mason Caron
AU - Yohannes Abate
PY - 2026
DA - 2026/09/11
PB - arXiv
DO - 10.48550/arxiv.2609.13493
UR - https://arxiv.org/abs/2609.13493
AB - In situ monitoring of reactions with chemical specificity and nanometer-scale spatial resolution under aqueous conditions remains a long-standing experimental challenge. Here, we use thin SiC membrane-enabled liquid-phase infrared nanoimaging and nanospectroscopy to monitor Ca^2+/Na^+ ion exchange in a mixture of disodium terephthalate and CaCl_2 solution. Beneath the membrane, we follow the formation of calcium terephthalate (CaTP), a metal-organic framework (MOF)-type coordination phase in which terephthalate ligands link Ca^2+ centers. The symmetric and asymmetric carboxylate stretching modes serve as chemically specific near-field reporters of Ca^2+ coordination to the terephthalate linkers. Nano-FTIR spectra reveal pronounced peak shifts and linewidth changes in these vibrational modes, indicating modification of the carboxylate coordination environment during CaTP formation. Complementary near-field nanoimaging resolves the emergence of nanoscale precipitates beneath the SiC membrane following CaCl_2 injection, providing spatially resolved evidence of the formation of the CaTP coordination framework. Solid-phase nanoimaging and nanospectroscopy identify well-defined CaTP particles, providing further evidence for crystalline CaTP formation. We demonstrate that the chemistry of metal-ligand interactions can be monitored in situ via liquid-phase near-field nanoscopy. This capability could enable the study of catalytic, electrochemical, and biological processes under native aqueous conditions.
ER -