An optical humidity sensor based on Ag nanodendrites

Cubic Ag dendritic nanostructure with ordered branches and Ag particles have been successfully prepared by soaking pretreated Zn plate into silver ammonia ion solution at 80 °C and reducing the silver ammonia ion solution with ascorbic acid in the presence of PVP, respectively. Field-emission scanning electron microscopy (FESEM) and transmission electron microscopy (TEM) images show that the overall length of the Ag nanodendrites is 3–10 μm, and the average diameter of the stems and branches are 100 nm and 50 nm, severally. The size of the Ag particles is in the range of 100–500 nm. The photoluminescence (PL) property of the samples reveals that the Ag dendritic nanostructures show stronger PL intensity than the Ag particles. A room temperature photoluminescence-type gas sensing device based on the pure Ag nanodendrites has been established to investigate their humidity sensing properties. For comparison, pure Ag particles-based sensors were also fabricated in the same condition. Compared with their counterparts, possibly due to its large surface area, Ag nanodendrites present better sensitivity, more excellent linearity and quicker recovery in a very wide humidity range at room temperature.