Negative temperature coefficient behavior of graphene-silver nanocomposite films for temperature sensor applications

we are reporting the fabrication of reduced graphene oxide (RGO) - silver (Ag) nanocomposite films for temperature sensor application on the basis of negative temperature coefficient (NTC) resistive element. The nanocomposite was successfully prepared by the solution mixing of RGO nanosheets and Ag metal nanoparticles in N-Methyl-2-Pyrrolidone (NMP) using ultrasonication process. It was found that, the as-formed Ag nanoparticles were dispersed homogeneously and uniformly on the surface of the RGO nanosheets within the nanocomposite system. The as-synthesized RGO nanosheets and nanocomposite were characterized by field emission scanning electron microscope (FE-SEM) and X-ray diffraction (XRD) for their surface analysis and structural properties respectively. The fabrication of temperature sensor, the sensing film formation is carried out on the flexible kapton membrane by using drop casting method. The thickness of the sensing film is around 50 μm. It was observed that the resistivity of nanocomposite sensing film decreased with the increase of temperature resulting in NTC behavior. The measured NTC and sensitivity of the sensor were found to be -0.00187 Ω / Ω / K and 0.40472 Ω /K respectively. Therefore, the synthesized graphene- silver nanocomposite film is an attractive material for making temperature sensors. Since the output is linear with respect to temperature variation, the electronic readout circuitry will be simpler. However, the mechanism of electrical resistance change of nanocomposite films can also be used in sensing environmental parameters such as chemical, biological, moisture and mechanical for their gas, glucose, humidity and strain/pressure sensor applications respectively.