The first sustainable material designed for air particulate matter capture: An introduction to Azure Chemistry.

This work presents a new porous material (SUNSPACE) designed for air particulate matter (PM) capture. It was developed in answer to the European Commission request of an innovative, affordable, and sustainable solution, based on design-driven material, to reduce the concentration of air particulate matter in urban areas. SUNSPACE material was developed from by-products and low-cost materials, such as silica fume and sodium alginate. Its capability to catch ultrafine PM was evaluated by different ad-hoc tests, considering diesel exhaust fumes and incense smoke PM. Despite the fact that procedures and materials can be designed for remediation, the high impact on the environment, for example in terms of natural resources consumption and emissions, are not usually considered. Instead, we believe that the technologies must be always evaluated in terms of material embodied energy (EE) and carbon footprint (CF). We define our approach to solve environment problems by a sustainable methodology "Azure Chemistry". For the SUNSPACE synthesis, the multi-criteria decision analysis was performed to select the best sustainable solution. The emissions and the energies involved in the synthesis of SUNSPACE material were evaluated with the Azure Chemistry approach, showing that this could be the best available technology to face the problem of capturing the PM in urban area.

Nickel oxide nanowires: vapor liquid solid synthesis and integration into a gas sensing device.

In the field of advanced sensor technology, metal oxide nanostructures are promising materials due to their high charge carrier mobility, easy fabrication and excellent stability. Among all the metal oxide semiconductors, nickel oxide (NiO) is a p-type semiconductor with a wide band gap and excellent optical, electrical and magnetic properties, which has not been much investigated. Herein, we report the growth of NiO nanowires by using the vapor liquid solid (VLS) technique for gas sensing applications. Platinum, palladium and gold have been used as a catalyst for the growth of NiO nanowires. The surface morphology of the nanowires was investigated through scanning electron microscopy to find out which catalyst and growth conditions are best for the growth of nanowires. GI-XRD and Raman spectroscopies were used to confirm the crystalline structure of the material. Different batches of sensors have been prepared, and their sensing performances towards different gas species such as carbon monoxide, ethanol, acetone and hydrogen have been explored. NiO nanowire sensors show interesting and promising performances towards hydrogen.

Thermally oxidized zinc oxide nanowires for use as chemical sensors.

Zinc oxide (ZnO) mat-based conductometric devices were fabricated using a thermal oxidation technique. A metallic zinc layer was deposited on the alumina transducer and then oxidized in a controlled atmosphere, in order to obtain ZnO nanostructures. Two different batches of sensors have been prepared, and their sensing performances have been evaluated towards oxidizing and reducing gases. Functional measurements showed very good sensing performances towards ethanol and acetone at 500 °C, and NO2 at 200 °C, indirectly confirming the n-type behaviour of the material. The influence of the humidity on the response has been explored. In practical conditions the interference of humidity is very small, and could be neglected in many applications. Simultaneous measurements on different devices from the same batch confirm the high reproducibility of the response within the batch.