Volatile organic compounds (VOCs) such as benzene (C 6 H 6 ), methylbenzene (C 6 H 5 CH 3 ), dichloromethane (CH 2 Cl 2 ) and methyl ethyl ketone (CH 3 COCH 2 CH 3 ), are exhausted into the atmosphere from a variety of industrial processes [1]. The removals of these VOCs are required because they are responsible for many environmental problems and diseases such as ozone depletion, photochemical smog, heart disease, asthma and even cancer [1][2][3][4]. There exist a lot of traditional techniques for VOCs degradation, including adsorption, incineration and condensation [5][6][7][8]. These methods have

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Photoconductors have extraordinarily high gain in quantum efficiency, but the origin of the gain has remained in dispute for decades. In this work, we employ photo Hall effect to reveal the gain mechanisms by probing the dynamics of photogenerated charge carriers in silicon nanowire photoconductors. The results reveal that a large number of photogenerated minority electrons are localized in the surface depletion region and surface trap states. The same number of excess hole counterparts is left in the nanowire conduction channel, resulting in the fact that excess holes outnumber the excess electrons in the nanowire conduction channel by orders of magnitude. The accumulation of the excess holes broadens the conduction channel by narrowing down the depletion region, which leads to the experimentally observed high photo gain.

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