Temperature sensor based on exfoliated graphene sheets produced by microwave assisted freezing induced volumetric expansion of carbonated water

In this report, we demonstrate the temperature sensing performance of exfoliated pristine few-layered graphene nanosheets. Fabrication of sensor material has been carried out by employing rapid, inexpensive and environmentally benign exfoliation approach based on microwave assisted freezing induced volumetric expansion of carbonated water. The structural and morphological characterization studies of as synthesized graphene nanosheets have been systematically accomplished by means of X-ray diffraction, Raman microscopic technique, scanning electron microscopy and transmission electron microscopy. The performance of assembled sensor is typically based upon resistive type temperature detection, which exhibits an exponential temperature dependence of resistance in temperature range of 28-250 degrees C. The resultant device exhibits a negative temperature coefficient resistance values of -1.41% (degrees C)(-1) and -0.53% (degrees C)(-1) in the temperature ranges of 28-45 degrees C and 50-160 degrees C respectively which are relatively higher than commercially available counterparts. The plausible underlying mechanism for temperature sensing has been explained on the basis of thermal generation of electron-hole pairs and carrier scattering by acoustic phonons. Captivatingly, the significant responsivity in temperature range of 28-45 degrees C has been obtained which makes the sensor competent for real time monitoring of body temperature. Such kind of temperature sensors may find their applications in customized health care and human-machine interface systems.