A Nanojunction pH Sensor within a Nanowire

pH sensors that are nanoscopic in all three dimensions are fabricated within a single gold nanowire. Fabrication involves the formation of a nanogap within the nanowire via electromigration, followed by electropolymerization of pH-responsive poly­(aniline) (PANI) that fills the nanogap forming the n...

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Bibliographic Details
Published in:Analytical chemistry (Washington) 2022-09, Vol.94 (35), p.12167-12175
Main Authors: Drago, Nicholas P., Choi, Eric J., Shin, Jihoon, Kim, Dong-Hwan, Penner, Reginald M.
Format: Article
Language:English
Subjects:
Aniline
Aqueous solutions
Calibration
Chemistry
Cleanrooms
Electrical impedance
Electrical junctions
Electrodes
Electromigration
Fabrication
Impedance
Impedance measurement
Nanotechnology
Nanowires
pH effects
pH sensors
Polyanilines
Polymerization
Response time
Salts
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Summary:pH sensors that are nanoscopic in all three dimensions are fabricated within a single gold nanowire. Fabrication involves the formation of a nanogap within the nanowire via electromigration, followed by electropolymerization of pH-responsive poly­(aniline) (PANI) that fills the nanogap forming the nanojunction. All fabrication steps are performed using wet chemical methods that do not require a clean room. The measured electrical impedance of the PANI nanojunction is correlated with pH from 2.0 to 9.0 with a response time of 30 s. Larger, micrometer-scale PANI junctions exhibit a slower response. The measured pH is weakly influenced by the salt concentration of the contacting aqueous solution. An impedance measurement at two frequencies (300 kHz and 1.0 Hz) enables estimation of the salt concentration and correction of the measured pH value, preserving the accuracy of the pH measurement across the entire calibration curve for salt concentrations up to 1.0 M. The result is a nanoscopic pH sensor with pH sensing performance approaching that of a conventional, macroscopic pH glass-membrane electrode.
ISSN:0003-2700
1520-6882
DOI:10.1021/acs.analchem.2c02606