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(Reference retrieved automatically from Web of Science through information on FAPESP grant and its corresponding number as mentioned in the publication by the authors.)

Model improvement for super-Nernstian pH sensors: the effect of surface hydration

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Author(s):
Madeira, Gustavo Daniel M. [1] ; Dias Mello, Hugo Jose N. P. [1, 2] ; Faleiros, Murilo C. [1] ; Mulato, Marcelo [1]
Total Authors: 4
Affiliation:
[1] Univ Sao Paulo, Fac Philosophy Sci & Letters Ribeirao Preto, Dept Phys, BR-14040901 Ribeirao Preto, SP - Brazil
[2] Sao Paulo State Univ UNESP, Inst Chem, BR-14800900 Araraquara, SP - Brazil
Total Affiliations: 2
Document type: Journal article
Source: Journal of Materials Science; v. 56, n. 3, p. 2738-2747, JAN 2021.
Web of Science Citations: 0
Abstract

The maximum sensitivity of pH sensors is given by the Nernst equation, and its theoretical value is 59.2 mV pH(-1). However, countless sensors developed and reported in the literature have their sensitivity higher than the Nernstian limit. These are called super-Nernstian sensors. To understand the causes of this behavior, the sensitivity of polyaniline thin films was studied by evaluation of an important parameter: the hydration of the film's surface. Sensitivities were measured before and after varied heat treatments, and the sensor's parameters were associated with the amount of water lost in the process. Polyaniline thin films were fabricated by galvanostatic electrodeposition in aqueous solution, and their sensitivity was measured before and after heating of the samples. An endothermic process, typical of evaporation, was revealed by the analysis of mass loss during the heating process. A decrease in the sensitivity of the films was observed after heating process. For comparison, polyaniline thin films were also fabricated by spin coating, in the absence of water, and their sensitivity proved to be smaller than for the galvanostatically fabricated ones and it did not change significantly after the heating processes. The results indicated that the Nernst model can be adjusted using a parameter (1/r) related to the hydration of the surface of the sample, which directly affects the sensitivity of the thin films. The lowest reachable 1/r value for samples containing no water is approximately 0.9. The parameter also describes the upper limits for the sensitivity of super-Nernstian sensors. (AU)

FAPESP's process: 18/24395-8 - Fabrication of Biosensors Based on Organic FET and Architected via Organic Electronics and Electrochemistry
Grantee:Hugo José Nogueira Pedroza Dias Mello
Support Opportunities: Scholarships in Brazil - Post-Doctoral
FAPESP's process: 14/24559-0 - Multimodal array of enzymatic biosensors: potentiometric differential mode, optical and conductometric.
Grantee:Hugo José Nogueira Pedroza Dias Mello
Support Opportunities: Scholarships in Brazil - Doctorate
FAPESP's process: 18/22223-5 - Modular biosensors based on electrolyte gated organic field effect transistors with polyaniline thin films
Grantee:Murilo Calil Faleiros
Support Opportunities: Scholarships in Brazil - Scientific Initiation
FAPESP's process: 17/24201-6 - Microelectronic Platforms for Electrochemical, Piezoelectric and FETs Biosensors
Grantee:Marcelo Mulato
Support Opportunities: Regular Research Grants