An Inkjet-printed amperometric H₂S sensor for environmental applications

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.