The Iranian researchers at Sharif University of Technology managed to fabricate a type of hydrogen nanosensor by sol gel method which has a sensitivity of order of 104 at room temperature.
The layers made by sol gel method had high porosity and particles with nanometric size (high surface to volume ratio) existed in their beds. Synthesized nanoparticles size is of such an order that they provide best surface to volume ratio for sensing tungsten trioxide. Samples contaminated by palladium showed very high sensitivities of orders greater than 104 against hydrogen even at low concentrations of gas at low working temperatures (room temperature).
Palladium generally increases sensitivity of metallic oxides sensors to reducing gases like hydrogen and lowers working temperature. Sensors made by sol gel method have chemical stability and short response time (less than 1 minute).
"Considering the industry movement towards using hydrogen as an alternative clean fuel, these sensors could be utilized in future vehicles and industrial applications such as fuel storage sites and stations or vehicles consuming hydrogen as a clean environmentally sustainable fuel", Ms. Somayyeh Fardindoost, one of the project researchers, said in an interview with INIC news service.
The advantages of taken sol gel method include simplicity, no need to vacuum equipments, and low costs.
Tungsten trioxide sol was produced by sol-gel method and by solving tungsten wire in oxygenated water. To contaminate by palladium, PdCl2 salt at different weight fractions of palladium was added to tungsten trioxide solution and then deposited on alumina sublayer by spin method. Samples were tested in gas system at the same conditions to analyze the sensitivity.
For more details see international journal of hydrogen Energy, volume 35, pages 854-860, 2010.