Counterion-Mediated Humidity Modulation of Electronic Transport in Pristine MWCNT/TOCNF Composites
- 1Universidade Federal de Ouro Preto , , , ,
- 2Universidade Federal de Minas Gerais , , , ,
Abstract
Humidity-driven electrical responses in carbon-cellulose composites are commonly attributed to matrix swelling. However, in TEMPO-oxidized nanocellulose (TOCNF), water uptake also releases Na+ counterions from carboxylate residues, enabling interfacial polarization via image-charge interactions that can modulate junction-limited electronic transport. Here, we formulate aqueous inks in which TOCNF disperses pristine (nonfunctionalized) multiwalled carbon nanotubes (MWCNT) without covalent modification, yielding homogeneous, spray-processable composite films. Using DC electrical measurements under controlled relative humidity, impedance spectroscopy, scanning probe microscopy, and a mean-field electrostatic model for counterion-mediated polarization, we show that percolated TOCNF/MWCNT films exhibit reproducible resistance gains, reaching up to ∼270%, that are inconsistent with a swelling mechanism alone. To support this view, a control based on nonoxidized nanocellulose (with a negligible amount of dissociable counterions) was designed, which shows only modest changes at high humidity, thereby sustaining an important, counterion-mediated interfacial route. The impedance data indicate predominantly electronic transport and a humidity-dependent low-frequency reactive response near the percolation threshold. The DC measurements establish a reproducible steady-state behavior and within-session cycling, while intrinsic response times and long-term stability remain to be more explored. The model rationalizes how increased counterion concentration under humidification can induce polarizing charges at the nanotube surface, driving electrostatic repulsion and relative reorientation that weaken conductive CNT-CNT junctions across the network. Invoking the Derjaguin approximation, an effective, counterion-induced repulsive interaction between CNT surfaces is computed, which prevents the building-up of large connecting junctions across the network, thus reducing their ability to assemble percolating pathways. These findings establish an overlooked counterion-mediated design principle to tune mixed ionic-electronic transport in sustainable CNT/nanocellulose electronic composites operating under humid or electrolyte-adjacent conditions.
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BibTeX
@article{siqueira2026counterionmediated,
title = {{Counterion-Mediated Humidity Modulation of Electronic Transport in Pristine MWCNT/TOCNF Composites}},
author = {Andreza J. Siqueira and Wflander M. Souza and Rayssa O. Matos and Hana H. Koga and Vinicius Ornelas and Claudio Laudares and Dalila C. Sicupira and Thiago Colla and Ive Silvestre and Ana Paula M. Barboza},
journal = {ACS omega},
year = {2026},
month = oct,
doi = {10.1021/acsomega.6c04065},
url = {https://europepmc.org/article/PMC/PMC13670278},
note = {CC BY},
}
RIS
TY - JOUR
TI - Counterion-Mediated Humidity Modulation of Electronic Transport in Pristine MWCNT/TOCNF Composites
AU - Andreza J. Siqueira
AU - Wflander M. Souza
AU - Rayssa O. Matos
AU - Hana H. Koga
AU - Vinicius Ornelas
AU - Claudio Laudares
AU - Dalila C. Sicupira
AU - Thiago Colla
AU - Ive Silvestre
AU - Ana Paula M. Barboza
PY - 2026
DA - 2026/10/02
JO - ACS omega
DO - 10.1021/acsomega.6c04065
UR - https://europepmc.org/article/PMC/PMC13670278
AB - Humidity-driven electrical responses in carbon-cellulose composites are commonly attributed to matrix swelling. However, in TEMPO-oxidized nanocellulose (TOCNF), water uptake also releases Na+ counterions from carboxylate residues, enabling interfacial polarization via image-charge interactions that can modulate junction-limited electronic transport. Here, we formulate aqueous inks in which TOCNF disperses pristine (nonfunctionalized) multiwalled carbon nanotubes (MWCNT) without covalent modification, yielding homogeneous, spray-processable composite films. Using DC electrical measurements under controlled relative humidity, impedance spectroscopy, scanning probe microscopy, and a mean-field electrostatic model for counterion-mediated polarization, we show that percolated TOCNF/MWCNT films exhibit reproducible resistance gains, reaching up to ∼270%, that are inconsistent with a swelling mechanism alone. To support this view, a control based on nonoxidized nanocellulose (with a negligible amount of dissociable counterions) was designed, which shows only modest changes at high humidity, thereby sustaining an important, counterion-mediated interfacial route. The impedance data indicate predominantly electronic transport and a humidity-dependent low-frequency reactive response near the percolation threshold. The DC measurements establish a reproducible steady-state behavior and within-session cycling, while intrinsic response times and long-term stability remain to be more explored. The model rationalizes how increased counterion concentration under humidification can induce polarizing charges at the nanotube surface, driving electrostatic repulsion and relative reorientation that weaken conductive CNT-CNT junctions across the network. Invoking the Derjaguin approximation, an effective, counterion-induced repulsive interaction between CNT surfaces is computed, which prevents the building-up of large connecting junctions across the network, thus reducing their ability to assemble percolating pathways. These findings establish an overlooked counterion-mediated design principle to tune mixed ionic-electronic transport in sustainable CNT/nanocellulose electronic composites operating under humid or electrolyte-adjacent conditions.
SN - 2470-1343
ER -