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意大利科学家用电纺丝纳米结构制造出新的氧化氮传感器 New look for NO2 sensors
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Metal oxides are routinely used to make gas sensors. These usually consist of a continuous thin film deposited by techniques such as thermal evaporation or sputtering onto patterned substrates. However, researchers would like to make such devices using nanostructures, which should be more sensitive than sensors made out of bulk materials. Sandro Santucci of the University of L'Aquila in Coppito and colleagues make their device using electrospinning, a technique that is simpler than thermal evaporation or sputtering and allows sub-micron features to be grown. The researchers inject a solution containing the precursor tungsten chloride and a polymer onto a silica substrate using a syringe, while applying a high voltage of around 10–20 kV between the needle and the substrate. The high electric field accelerates the solution towards the substrate, which lies about 15 cm from the needle, and the polymer chains allow a net of nanofibres of tungsten oxide to form on it (see figure). The sample is then annealed for several hours at 300 °C to allow the solvents and polymer to evaporate. To test the material, the Italian scientists deposit their nanofibres on to a silicon substrate patterned with platinum contacts and measure how the resistance of the sensor changes when exposed to nitrogen dioxide. The technique reveals that the device can detect NO2 concentrations as low as 0.11 ppm, which, considering the sensing area, is a much higher sensitivity than sensors made from continuous films. The team would now like to make aligned fibres so that they can build sensors using a single fibre. "This will allow the use of very small devices where size, weight and power can be critical," explained team member Luca Lozzi. The researchers will do this using the so-called near-field technique, where the needle–substrate distance is just a few millimetres and the voltage lower at about 1 kV. "Moving the substrate during deposition in a controlled manner would allow well ordered fibres to be formed," added Lozzi. The work was published in J. Appl. Phys. 101 124504 |
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