Intense pH Sensitivity Modulation in Carbon Nanotube-Based Field-Effect Transistor by Non-Covalent Polyfluorene Functionalization

We compare the pH sensing performance of non-functionalized carbon nanotubes (CNT) field-effect transistors (p-CNTFET) and CNTFET functionalized with a conjugated polyfluorene polymer (labeled FF-UR) bearing urea-based moieties (f-CNTFET). The devices are electrolyte-gated, PMMA-passivated, 5 µm-cha...

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Main Authors: Gookbin Cho, Eva Grinenval, Jean-Christophe P. Gabriel, Bérengère Lebental
Format: Article
Language:English
Published: MDPI AG 2023-03-01
Series:Nanomaterials
Subjects:
Online Access:https://www.mdpi.com/2079-4991/13/7/1157
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author Gookbin Cho
Eva Grinenval
Jean-Christophe P. Gabriel
Bérengère Lebental
author_facet Gookbin Cho
Eva Grinenval
Jean-Christophe P. Gabriel
Bérengère Lebental
author_sort Gookbin Cho
collection DOAJ
description We compare the pH sensing performance of non-functionalized carbon nanotubes (CNT) field-effect transistors (p-CNTFET) and CNTFET functionalized with a conjugated polyfluorene polymer (labeled FF-UR) bearing urea-based moieties (f-CNTFET). The devices are electrolyte-gated, PMMA-passivated, 5 µm-channel FETs with unsorted, inkjet-printed single-walled CNT. In phosphate (PBS) and borate (BBS) buffer solutions, the p-CNTFETs exhibit a p-type operation while f-CNTFETs exhibit p-type behavior in BBS and ambipolarity in PBS. The sensitivity to pH is evaluated by measuring the drain current at a gate and drain voltage of −0.8 V. In PBS, p-CNTFETs show a linear, reversible pH response between pH 3 and pH 9 with a sensitivity of 26 ± 2.2%/pH unit; while f-CNTFETs have a much stronger, reversible pH response (373%/pH unit), but only over the range of pH 7 to pH 9. In BBS, both p-CNTFET and f-CNTFET show a linear pH response between pH 5 and 9, with sensitivities of 56%/pH and 96%/pH, respectively. Analysis of the I–V curves as a function of pH suggests that the increased pH sensitivity of f-CNTFET is consistent with interactions of FF-UR with phosphate ions in PBS and boric acid in BBS, with the ratio and charge of the complexed species depending on pH. The complexation affects the efficiency of electrolyte gating and the surface charge around the CNT, both of which modify the I–V response of the CNTFET, leading to the observed current sensitivity as a function of pH. The performances of p-CNTFET in PBS are comparable to the best results in the literature, while the performances of the f-CNTFET far exceed the current state-of-the-art by a factor of four in BBS and more than 10 over a limited range of pH in BBS. This is the first time that a functionalization other than carboxylate moieties has significantly improved the state-of-the-art of pH sensing with CNTFET or CNT chemistors. On the other hand, this study also highlights the challenge of transferring this performance to a real water matrix, where many different species may compete for interactions with FF-UR.
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spelling doaj.art-cf57cbaf8e0b47298c7e4a83ab26e44a2023-11-17T17:16:31ZengMDPI AGNanomaterials2079-49912023-03-01137115710.3390/nano13071157Intense pH Sensitivity Modulation in Carbon Nanotube-Based Field-Effect Transistor by Non-Covalent Polyfluorene FunctionalizationGookbin Cho0Eva Grinenval1Jean-Christophe P. Gabriel2Bérengère Lebental3Laboratoire de Physique des Interfaces et des Couches Minces, LPICM, CNRS, Ecole Polytechnique, Institut Polytechnique Paris, 91128 Palaiseau, FranceLaboratoire de Physique des Interfaces et des Couches Minces, LPICM, CNRS, Ecole Polytechnique, Institut Polytechnique Paris, 91128 Palaiseau, FranceLICSEN, NIMBE (UMR CEA/CNRS 3685), Université Paris-Saclay, 91191 Gif sur Yvette, FranceIMSE, COSYS, Université Gustave Eiffel, Marne-la-Vallée Campus, 77447 Marne-La-Vallée, FranceWe compare the pH sensing performance of non-functionalized carbon nanotubes (CNT) field-effect transistors (p-CNTFET) and CNTFET functionalized with a conjugated polyfluorene polymer (labeled FF-UR) bearing urea-based moieties (f-CNTFET). The devices are electrolyte-gated, PMMA-passivated, 5 µm-channel FETs with unsorted, inkjet-printed single-walled CNT. In phosphate (PBS) and borate (BBS) buffer solutions, the p-CNTFETs exhibit a p-type operation while f-CNTFETs exhibit p-type behavior in BBS and ambipolarity in PBS. The sensitivity to pH is evaluated by measuring the drain current at a gate and drain voltage of −0.8 V. In PBS, p-CNTFETs show a linear, reversible pH response between pH 3 and pH 9 with a sensitivity of 26 ± 2.2%/pH unit; while f-CNTFETs have a much stronger, reversible pH response (373%/pH unit), but only over the range of pH 7 to pH 9. In BBS, both p-CNTFET and f-CNTFET show a linear pH response between pH 5 and 9, with sensitivities of 56%/pH and 96%/pH, respectively. Analysis of the I–V curves as a function of pH suggests that the increased pH sensitivity of f-CNTFET is consistent with interactions of FF-UR with phosphate ions in PBS and boric acid in BBS, with the ratio and charge of the complexed species depending on pH. The complexation affects the efficiency of electrolyte gating and the surface charge around the CNT, both of which modify the I–V response of the CNTFET, leading to the observed current sensitivity as a function of pH. The performances of p-CNTFET in PBS are comparable to the best results in the literature, while the performances of the f-CNTFET far exceed the current state-of-the-art by a factor of four in BBS and more than 10 over a limited range of pH in BBS. This is the first time that a functionalization other than carboxylate moieties has significantly improved the state-of-the-art of pH sensing with CNTFET or CNT chemistors. On the other hand, this study also highlights the challenge of transferring this performance to a real water matrix, where many different species may compete for interactions with FF-UR.https://www.mdpi.com/2079-4991/13/7/1157carbon nanotubesfield effect transistorelectrolyte gatingpH sensingnon covalent functionalizationpolyfluorene
spellingShingle Gookbin Cho
Eva Grinenval
Jean-Christophe P. Gabriel
Bérengère Lebental
Intense pH Sensitivity Modulation in Carbon Nanotube-Based Field-Effect Transistor by Non-Covalent Polyfluorene Functionalization
Nanomaterials
carbon nanotubes
field effect transistor
electrolyte gating
pH sensing
non covalent functionalization
polyfluorene
title Intense pH Sensitivity Modulation in Carbon Nanotube-Based Field-Effect Transistor by Non-Covalent Polyfluorene Functionalization
title_full Intense pH Sensitivity Modulation in Carbon Nanotube-Based Field-Effect Transistor by Non-Covalent Polyfluorene Functionalization
title_fullStr Intense pH Sensitivity Modulation in Carbon Nanotube-Based Field-Effect Transistor by Non-Covalent Polyfluorene Functionalization
title_full_unstemmed Intense pH Sensitivity Modulation in Carbon Nanotube-Based Field-Effect Transistor by Non-Covalent Polyfluorene Functionalization
title_short Intense pH Sensitivity Modulation in Carbon Nanotube-Based Field-Effect Transistor by Non-Covalent Polyfluorene Functionalization
title_sort intense ph sensitivity modulation in carbon nanotube based field effect transistor by non covalent polyfluorene functionalization
topic carbon nanotubes
field effect transistor
electrolyte gating
pH sensing
non covalent functionalization
polyfluorene
url https://www.mdpi.com/2079-4991/13/7/1157
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