title: A titania nanotube-array room-temperature sensor for selective detection of hydrogen at low concentrations.
abstract: A tremendous variation in electrical resistance, from the semiconductor to metallic range, has been observed in titania nanotube arrays at room temperature, approximately 25 degrees C, in the presence of < or = 1000 ppm hydrogen gas. The nanotube arrays are fabricated by anodizing titanium foil in an aqueous electrolyte solution containing hydrofluoric acid and acetic acid. Subsequently, the arrays are coated with a 10 nm layer of palladium by evaporation. Electrical contacts are made by sputtering a 2 mm diameter platinum disk atop the Pd-coated nanotube array. These sensors exhibit a resistance variation of the order of 10(4) in the presence of 100 ppm hydrogen at 25 degrees C. The sensors demonstrate complete reversibility, repeatability, high selectivity, negligible drift and wide dynamic range. The nanoscale geometry of the nanotubes, in particular the points of tube-to-tube contact, is believed to be responsible for the outstanding hydrogen gas sensitivities.
authors.affiliation: Department of Electrical Engineering, The Pennsylvania State University, University Park, Pennsylvania 16802, USA.
authors.forename: Oomman K
authors.initials: OK
authors.lastname: Varghese
authors.forename: Gopal K
authors.initials: GK
authors.lastname: Mor
authors.forename: Craig A
authors.initials: CA
authors.lastname: Grimes
authors.forename: Maggie
authors.initials: M
authors.lastname: Paulose
authors.forename: Niloy
authors.initials: N
authors.lastname: Mukherjee
mesh_terms: D019342:Acetic Acid / Q000737:chemistry; D002248:Carbon Monoxide; D017097:Electric Impedance; D004560:Electricity; D004563:Electrochemistry; D006858:Hydrofluoric Acid / Q000737:chemistry; D006859:Hydrogen / Q000032:analysis* / Q000737:chemistry; D008855:Microscopy, Electron, Scanning; D036103:Nanotechnology / Q000379:methods*; D043942:Nanotubes / Q000737:chemistry; D010165:Palladium / Q000737:chemistry; D012666:Semiconductors; D012680:Sensitivity and Specificity; D013696:Temperature; D013997:Time Factors; D014025:Titanium / Q000737:chemistry*; D014961:X-Ray Diffraction
chemical_list: C009495:titanium dioxide; D010165:Palladium; D002248:Carbon Monoxide; D006859:Hydrogen; D014025:Titanium; D019342:Acetic Acid; D006858:Hydrofluoric Acid