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Chemiresistive sensing with functionalized carbon nanotubes

Nature Reviews Methods Primers volume 3, Article number: 73 (2023) Cite this article

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Abstract

Chemical sensing has a vital role in promoting security and welfare. Functionalized carbon nanotubes (CNTs) possess unique electronic, mechanical and chemical properties, rendering them as exceptional transducers for developing highly sensitive, selective and robust chemical sensors. In this Primer, we discuss the progress and challenges associated with chemiresistive sensing using functionalized CNTs, providing an introductory overview, spanning from theoretical to experimental aspects. Various covalent and non-covalent CNT functionalization strategies that contribute to enhancing the sensitivity and selectivity of chemiresistive sensors are discussed, along with their respective merits and drawbacks. Additionally, this Primer focuses on the critical facets of experimental design, including material selection, device architecture and fabrication and best practices for sensor testing. This Primer also discusses the significance of rigorous data interpretation, analysis and reporting, ensuring reproducibility and reliability. Finally, this Primer highlights the existing limitations of CNT-based chemiresistive sensors and investigates potential strategies for enhancing sensor selectivity and sensitivity that may broaden their applicability in diverse fields, from environmental monitoring to biomedical diagnostics. By emphasizing the need to understand the molecular interactions between the sensor and target analyte to improve selectivity, this Primer aims to offer a comprehensive understanding of the current state of CNT-based chemiresistive sensing.

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Fig. 1: Structural configurations of carbon nanotubes.
Fig. 2: Schematic illustration of two single-walled carbon nanotubes bridging two electrodes.
Fig. 3: Comparison between covalent and non-covalent functionalizations of carbon nanotube.
Fig. 4: Design schemes of carbon nanotube-based chemiresistive devices.
Fig. 5: Design schemes of chemiresistive-sensing experiments.
Fig. 6: Typical characterization of sensor performance.
Fig. 7: Evaluation of sensing mechanism by Raman spectroscopy and transfer characteristics of carbon nanotube-field-effect transistor.

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Acknowledgements

The authors gratefully acknowledge the National Science Foundation (DMR-2207299).

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Authors and Affiliations

  1. Department of Chemistry, Massachusetts Institute of Technology, Cambridge, MA, USA

    Shao-Xiong Lennon Luo & Timothy M. Swager

  2. Institute for Soldier Nanotechnologies, Massachusetts Institute of Technology, Cambridge, MA, USA

    Shao-Xiong Lennon Luo & Timothy M. Swager

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Glossary

Arc discharge

A method for synthesizing carbon nanotubes through arc-vaporization of two adjacent graphite electrodes in an inert gas.

Chiral (roll-up) vector

A lattice vector in the hexagonal graphene sheet that defines the structure of a carbon nanotube by specifying the direction and distance of the rolling/wrapping of the graphene sheet.

Device hysteresis

The phenomenon in which the output of a device depends not only on its current input but also on its past inputs, resulting in a lag or variance in response.

Dosimeters

Sensors that provide an integrated measure of exposure over a time period and are ideal for applications such as monitoring cumulative exposure of an individual to toxic chemicals.

Intra-CNT interactions

Sensing mechanisms involve interactions between the analyte and individual carbon nanotubes (CNTs) or CNT bundles, which modify the number and mobility of charge carriers.

Inter-CNT interactions

Sensing mechanisms originate from the changes in the intertubular electron transfer.

Pristine CNTs

Carbon nanotubes (CNTs) in their original, unmodified state, without any functionalization or doping, often used as a baseline for comparison in sensor performance studies.

Recovery time

The time required to accomplish a 90% recovery on removal of the target analyte under the background gas or liquid.

Response time

The time needed for the sensor to achieve 90% of its maximum response.

Schottky barrier modulations

The effects on the junction between carbon nanotubes and metal electrodes to modulate the measured conductance.

Selectors

A component of a sensor system that provides specificity, enabling the sensor to distinguish between different analytes in a complex mixture.

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Luo, SX.L., Swager, T.M. Chemiresistive sensing with functionalized carbon nanotubes. Nat Rev Methods Primers 3, 73 (2023). https://doi.org/10.1038/s43586-023-00255-6

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