Coming from natural and anthropogenic sources, hydrogen sulfide gas (H₂S) is a smelly hazardous substance at the sub-ppm level, which can lead to poisoning deaths at higher concentrations. Researchers have been working for decades to design sensors with sufficient/good/robust metrological properties and good stability in order to monitor and control in real time the risk associated with this gas. Among the devices proposed, chemiresistive sensors based on conductive polymer appear as a good alternative to the most common solutions such as electrochemical and optical sensors. They present various advantages in terms of design (easy fabrication, easy tuning of physical and chemical properties, low cost, etc.) and performances (good sensitivity, good reproducibility, room temperature operation, short response time, etc.). In this review, we summarize the progresses made on conductive polymer sensors dedicated to H₂S detection, including the performance of the different materials and sensing mechanisms. Finally, we identify the limitations of these sensors and highlight the most promising approaches to enable the use of these technologies in real-world applications.

Conducting polymers such as poly(3,4-ethylenedioxythiophene) polystyrene sulfonate (PEDOT:PSS) are increasingly used to interface electronics with biology. Their wettability, however, remains poorly understood. We show that the frequently-used sessile drop technique yields results that are strongly dependent on the experimental conditions (measurement duration and relative humidity), due to the hydrogel-like behavior of PEDOT:PSS. In contrast, the captive bubble technique on a fully wet film overcomes these limitations. Dynamic wettability measurements provide hysteresis values for this polymer and clarify the physical meaning of the static contact angles measured by sessile drop and captive bubble. Finally we show that aging the films in water leads to loss of PSS chains which makes the films more hydrophobic. The addition of a crosslinker reduces and slows down these effects.

Polyaniline (PANI) is a conducting polymer, widely used in gas-sensing applications. Due to its classification as a semiconductor, PANI is also used to detect reducing ammonia gas (NH₃), which is a well-known and studied topic. However, easier, cheaper and more straightforward procedures for sensor fabrication are still the subject of much research. In the presented work, we describe a novel, more controllable, synthesis approach to creating NH₃ PANI-based receptor elements. The PANI was electrochemically deposited via cyclic voltammetry (CV) on screen-printed electrodes (SPEs). The morphology, composition and surface of the deposited PANI layer on the Au electrode were characterised with electron microscopy, Fourier-transform infrared spectroscopy and profilometry. Prior to the gas-chamber measurement, the SPE was suitably modified by Au sputtering the individual connections between the three-electrode system, thus showing a feasible way of converting a conventional three-electrode electrochemical SPE system into a two-electrode NH₃-gas detecting system. The feasibility of the gas measurements’ characterisation was improved using the gas analyser. The gas-sensing ability of the PANI-Au-SPE was studied in the range 32–1100 ppb of NH₃, and the sensor performed well in terms of repeatability, reproducibility and sensitivity.