Humidity sensors based on ZnO Colloidal nanocrystal clusters

High pure ZnO Colloidal nanocrystal clusters (CNCs) were synthesized by a modified hydrolyzation method. The diameters of as-prepared ZnO crystalline were between 20 and 40 nm, however, the ZnO CNCs arrived at 400–800 nm. The ZnO CNCs sensor were found to have high sensitivity and fast response/recovery time to humidity, and their resistance changed approximately three orders of magnitude from about 1.58 × 109 Ω in dry air (10 RH%) to 1.65 × 106 Ω in 93 RH% air. Furthermore, the ZnO CNCs sensors were relatively stable to humidity for a long time.