ures 1a,b, the nanotubes are in contact with each other, providing a high resistance path for electron travel. On the creation of the space charge layer due to hydrogen adsorption, these tube-to-tube contact points become highly conducting relative to the rest of the nanotube. For a bulk conductivity constant with nanotube diameter the greater the number of contact points the greater will be the resistance change upon exposure to hydrogen. Therefore, the smaller diameter tubes, with thinner walls and greater number of contact points will exhibit higher sensitivities than their larger diameter counterparts.Out results show titania nanotubes can be used as extremely sensitive, drift-free, and robust hydrogen sensors. Hydrogen sensing applications include industrial process control, combustion control, clinical use where hydrogen is an indicator of certain types of bacterial infection, and will certainly be of critical importance to a hydrogen-based fuel economy. Agreement between our experimental results and chemisorption isotherms indicate chemisorption as the fundamental mechanism of hydrogen interaction with the nanotubes. The nanoscale morphology of the nanotubes, not simply surface area, is responsible for the variation in hydrogen sensitivity with nanotube diameter as the space charge layers are significantly modified at this length scale. There is no doubt that one of the greatest challenges of modern electrochemistry is the development of high energy density, rechargeable batteries, which are composed of materials as environmentally and abandon-friendly as possible. An excellent candidate as an anode material for batteries is magnesium, which is an active metal, easily obtained in the earth's crust, and safe for handling and use. In the field of lithium batteries, [1] Major efforts are invested in the development of rechargeable polymer lithium batteries. Replacement of liquid electrolyte solutions by solid-state electrolytes should have great advantages in terms of ease of fabrication, flexibility in dimensions and geometry of the batteries (e.g., production of flat thin batteries with light plastic cases), and safety features. There are continuous attempts to develop polymers that can dissolve lithium salts, and hence, form freestanding solid matrices that can conduct lithium ions. [2,3] However, so far the most practical solid electrolytes that are being developed for lithium batteries are gel systems, which contain a polymeric matrix, lithium salt, and polar aprotic solvents (mostly cyclic alkyl carbonates), which are trapped in the matrix, solvate the lithium salts, and hence, enable high conductivity to be achieved at low temperatures. [4,5] Following the interest and achievements in the field of lithium electrochemistry, there have been attempts over the years to develop rechargeable magnesium batteries. [6] There are reports on a search for non-aqueous electrolyte systems from which magnesium can be reversibly deposited [7] and on the study of cathode materials that reversibly intercalate mag...
