Humidity Sensitivity Enhancement Effects of Metal Nanoparticles Loaded Fullerene

Abstract

In this paper, the response characteristics of capacitive humidity sensors based on fullerene (C60) loaded with metal nanoparticles (MNPs) were investigated. Experimental results demonstrated that the humidity sensitive properties of all the sensors are significantly improved after loading MNPs. This may be related to the hydrophilicity change of fullerene composite membranes induced by MNPs, which is confirmed by the test results of water contact angle and complex impedance spectrum. Moreover, the enhancement effect of humidity sensitivity is more obvious with the increase of MNPs content, but when the MNPs content exceeds a certain value, the enhancement effect of humidity sensitivity will decrease, which may be attributed to the agglomeration of MNPs. Meanwhile, for samples loaded with different MNPs (AuNPs, AgNPs, CuNPs), the improvement effects are quite different. Among the three samples studied, the C60/Ag sample exhibit the best response characteristics with a sensitivity of 5,812.8 pF/%RH, which is more than 200 times higher than that of the unloaded sample. The C60/Cu sample has no obvious response in low relative humidity (RH), but its sensitivity at high humidity is even higher than that of the C60/Ag sample, which shows the characteristics similar to a humidity sensitive switch. The C60/Au sample is one order of magnitude more sensitive than pure C60 sample and exhibits the best stability among the three samples. The above results suggest that different MNPs can be selected to develop humidity sensors with different characteristics according to the application situations.