Hydrogen sulfide (H2S) is a highly toxic and dangerous compound, capable of causing severe health problems after prolonged exposure even at low concentrations. It is a gas, slightly solvable in water at acid pH. Nonetheless, as pH increases its labile protons are lost and it becomes the more soluble HS- ion. It appears in wastewater treatment plants and gas treatment bio-scrubbers and is still highly pollutant and hazardous. Thus, it is of critical importance to develop effective methods to monitoring H2S in biological treatment process and water systems.
Inkjet printing technology has been proven in the recent years as an economic, fast, reproducible and highly versatile method of mass-producing micro-electrodes. Those can themselves be made of a large variety of materials, from metals to polymers. Tuned with the appropriate transductors, many electrodes can become sensors for analytes of interest. Considering the hazards produced by chemicals like H2S, miniaturized systems like this are becoming the new sensing platforms for tracking pollutants.
Herein, an easy to produce, low-cost, miniaturized and inkjet-printed amperometric H2S sensor is presented. A gold electrode, coupled to a conductive track of silver, is modified with a mixture of Single-Walled Carbon Nanotubes (SWCNTs), Poly(VinylAlcohol) (PVA) and Poly(DiallylDimethylAmmonium Chloride) (PDDA). It detects HS- by oxidizing it into elemental sulfur (S0), recording the produced current from this reaction. It has an effective working pH range of 6.5-13 and a wide linear range response from 6 µM to 592 µM of HS-. Tests show that the sensor is also capable of working on complex samples, such as reactor media.
