Similar current increase was observed when the conducting channel contains only multilayers of polymers 关Fig. 2共c兲 red兴. This is due to the ion mobility increase in the dehydrated multiple polymer. Current re- sponses of the multilayer polymers without ZnO NB or with ZnO NB only but without polymer are opposite to the re- sponse of polymer functionalized ZnO NBs. These experi- ments proved that neither ZnO NB nor multilayer polymers could produce the decreased current response upon exposing to vapor. Therefore, we suspect that the decreased current response come from the coupling effect of the coating poly- mer layers and the ZnO NBs