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Iridium oxide and cobalt hydroxide microfluidic-based potentiometric pH sensor

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Abstract

Microliter volume pH determination is of great importance in the biomedical and industrial applications. The current available pH meter and measurement techniques are hard to reach the high demand of microliter volume pH determination in a repeatable, stable, and sensitivity manner. This work aims to fill the gap of microliter volume pH measurements while maintaining good sensing performance. The electrodeposited iridium oxide and cobalt hydroxide along with gold electrode served as working, counter, and reference electrode, respectively, for 10–12 μL volume pH measurements with Nernst constant of 55.9 ± 4.4 mV/pH. The electrodeposited thin film was further characterized by scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray powder diffraction (XRD), Raman spectrometry, etc. to confirm its morphology and composition. The constructed pH sensor was used for human serum sample measurements to confirm the suitability of future applications. The results show that it has only 0.80% variation compared to a commercial pH meter with a limit of detection (LOD, or resolution) of ± 0.01 pH. It holds a great potential to be used in the future for microliter volume in situ pH measurements.

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Data Availability

Data are available upon requests to the corresponding author.

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Acknowledgements

We appreciate the help and discussion regarding the XPS analysis with Dr. Graham Dawson in the Department of Chemistry at Xi’an Jiaotong-Liverpool University.

Funding

This research was supported by Research & Development Fund (Project Number: RDF-21-1-005) under Xi’an Jiaotong-Liverpool University.

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Authors and Affiliations

  1. School of Science, Department of Chemistry, Xi’an Jiaotong-Liverpool University, Ren’Ai Road No. 111, Dushu Lake Higher Education and Innovation District, Suzhou Industrial Park, Suzhou, 215123, People’s Republic of China

    Weiyu Xiao & Qiuchen Dong

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  1. Weiyu Xiao
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  2. Qiuchen Dong
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Contributions

QD designed the initial scheme of the experiments and fabricated the microelectrodes in clean room. WX designed the selectivity tests and human serum pH tests. WX carried out the SEM, XRD, Raman spectrometry, and analyzed the data of TEM, SAED, and metal mapping as well as pH sensing measurements. WX wrote the draft of the manuscript, and QD revised it. QD was responsible for the funding acquisition and supervision.

Corresponding author

Correspondence to Qiuchen Dong.

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Conflict of interest

The work related to the microfluidic-based electrodeposition, microfabrication processes, and its solid-state pH sensor has been filed with a patent (Patent applicant: Qiuchen Dong, Weiyu Xiao) supported by the Research Development Fund (Project Number: RDF-21-1-005) of Xi’an Jiaotong Liverpool University in the People’s Republic of China with the application number of 202310526544.0, which is pending for approval.

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Xiao, W., Dong, Q. Iridium oxide and cobalt hydroxide microfluidic-based potentiometric pH sensor. Microchim Acta 190, 457 (2023). https://doi.org/10.1007/s00604-023-06035-z

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