Electrical and sensing properties of a flexible humidity sensor made of polyamidoamine dendrimer-Au nanoparticles

Generation 1 amine terminated polyamidoamine (PAMAM) dendrimer (G1-NH2)-Au nanoparticles (G1-NH2-AuNPs) was coated on a polyester (PET) substrate to form a novel flexible impedance-type humidity sensor. The formation of AuNPs was characterized by UV-vis spectroscopy. The microstructure of the G1-NH2-AuNPs film was analyzed by atomic force microscope (AFM). The effect of the AuNPs on the electrical and humidity sensing properties of the G1-NH2-AuNPs films on a PET substrate was investigated. The sensor had good flexibility. This flexible humidity sensor also exhibited good sensitivity and acceptable linearity (Y = -0.045X + 7.866; R-2 = 0.9693) between logarithmic impedance (logZ) and RH in the range 30-90%RH, negligible hysteresis (within 2%RH), good response time (40 s) and recovery time (50 s), and long-term stability (39 days at least), measured at 1 V. 1 kHz and 25 degrees C. The flexible humidity sensor's linearity depended on the applied frequency. The temperature influence between 15 and 35 degrees C; found to be -0.55%RH/degrees C for 30-90%RH. The different complex impedance plots obtained at low and high relative humidity indicated that the ions dominate the conductance of the G1-NH2-AuNPs film. (C) 2012 Elsevier B.V. All rights reserved.