Eni Carbon Silicates as crystalline and mesoporous hybrids for gas sensing

Nowadays, in order to satisfy market demands, materials and devices for sensors production must be increasingly miniaturized, eco-friendly, energetically efficient, reliably multitasking, and low-cost. Then, the research in material and technological sciences has gained a huge development to reach the expectations. Moving towards these requirements, hybrid nanomaterials are a fundamental alternative choice with respect to well-established materials. The purpose of this work is to satisfy both sciences, on the one hand implementing innovative hybrid materials referred to as ECS (Eni Carbon Silicate) in gas sensors manufacturing, and on the other hand verifying their possible operation at room temperature as a technological progress. Concerning the research in materials science, it is obvious that the employment of hybrids has represented a new challenge, especially because in ECS powders, with respect to the most hybrid materials, organic and inorganic components are not only anchored but perfectly merged to each other in a complex structure. The novelty of these materials concerns in fact their structures, crystalline aluminosilicate scaffoldings with long-range 3D order, which distinguish them from the previously reported amorphous and ‘‘crystal-like’’ silica-based PMOs (periodic mesoporous organosilicas). Regarding the research in technological science, room temperature operation is an extremely valuable goal in gas sensing, due to intrinsic safety of sensors working in harsh or industrial environment; moreover it is interesting to reduce high power consumption that characterized the wide used sensors based on metal-oxides semiconductors and consequently the size of associated electronics. The research activity was divided in two parts: development of preliminary studies about the role of solvents and investigation on the suitability of ECS powders as suspensions for resulting film depositions. In the second part ECSs were used as functional material in screen-printable compositions. The samples were deposited by drop coating on glass, silicon and alumina substrates for morphological (optical and SEM microscopy), structural (XRD), and thermal (TG-DTA) or electrical (gas tests) characterizations, respectively. The measurements, carried out in a suitable test chamber with controlled atmosphere and standard electronic detection, allowed to study possible electrical and sensing properties. A significant response with sensors based on ECS 14 powders tested in humidity conditions and a calibration for an increasing RH% was obtained. Other powders showed an electrical activity, in particular ECS 13 gave a low response to acetaldehyde. The results were analyzed and compared with the literature to determine if ECSs represent an improvement in gas sensing field, and a possible interpretation of sensing mechanism was suggested. It was concluded that the electrically active films prepared with ECS powders by simple deposition technique can be employed as functional layers in gas sensors. The devices obtained with the ECS hybrids have the properties of speed, reversibility and selectivity fundamental for a good quality electrical response that makes them competitive with respect to systems currently in use. The technological advantage of room temperature operating and the selectivity are added to the novelty of the application of ECSs as active materials in gas sensing.