At present, it is a hot topic to develop chemical sensors that have wide application potential (Kong et al. in Science 287:622–625, 2000;Kreno et al. in Chem Rev 112:1105–1125, 2012;). For enhancing the sensing properties, the nanostructures-based sensor devices are extensively studied since they have greater surface areas than the traditional bulks (Robinson et al. in Nano Lett 6:1747–1751, 2006;Huang and Choi in Sens Actuators B 122:659–671, 2007;Yavari and Koratkar in J Phys Chem Lett 3:1746–1753, 2012;).