Polyaniline Films as Electrochemical-Proton Pump for Acidification of Thin Layer Samples

Abstract

Here, we provide the first experimental evidence of proton release from polyaniline (PANI) films subjected to anodic potentials at environmental pHs. We conducted an extensive characterization of unpolarized/polarized PANI filmssynthesized by traditional sequential voltammetric scanningby using spectroelectrochemistry, synchrotron radiation-X-ray photoelectron spectroscopy, near edge X-ray absorption fine structure, and potentiometric pH sensing in the vicinity of the PANI layer. This new insight enables the utilization of PANI as a proton pump, which is actively tuned through an electrochemical pulse, so as to controllably acidify well-confined thin layer samples. Furthermore, we demonstrate the analytical significance of this system by measuring the alkalinity of artificial and natural water samples by using two faced planar PANI electrodes, one working as a proton source and the other one as pH electrode. Finally, the impact of this approach is 2-fold: (i) all-solid-state electrode materials may be used with devisible consequences in miniaturized and implementable submersible probes, and (ii) rapid determination of alkalinity as compared to traditional approaches together with a versatility in pH adjustment in any kind of sample, among other applications.

Lactate Biosensing for Reliable On-Body Sweat Analysis

“…The potentiometric pH sensor was based on a conductive PANI film, as reported in previous works. 46 Figure S6a in the Supporting Information shows a calibration curve as the average of three electrodes over a pH range from 4.5 to 8.5, which covers normal pH values in sweat. A Nernstian response was observed, with a slope of 59.1 ± 0.6 mV and intercept of 387.1 ± 12 mV.…”

Dynamic Sensor Concept Combining Electrochemical pH Manipulation and Optical Sensing of Buffer Capacity

“…To enable such an approach a dynamic stimulus is used to activate the sensor or, in other words, to disrupt the equilibrium. Such a stimulus can be optical, electrochemical, , or even mechanical . Dynamic readout requires that the used stimulus can affect the equilibrium locally in the vicinity of the sensor.…”

“…The groups of Bakker and Crespo recently published several very interesting examples where proton pumps were used to modify the local environment in a thin layer in front of a sensor. ,, While these approaches are very elegant and promising, the proposed systems are rather complicated and utilize custom-made electrodes and materials. In addition, the presented methods focus on combining electrochemical methods and do not explore the possibility of combining proton pumps or other stimuli with optical sensors.…”

“…In addition, the presented methods focus on combining electrochemical methods and do not explore the possibility of combining proton pumps or other stimuli with optical sensors. The techniques were used to modulate the response of anion-selective electrodes by removing the major interfering species, hydroxide, and also to measure alkalinity. , …”

“…While both optical , and electrochemical sensors − for buffer capacity have been demonstrated, a combined approach has until now not been realized. We present an active sensor system combining optical and electrochemical techniques using only off-the-shelf components.…”