Fabrication of Ultrasensitive Bio-Nanosensor Based on Polypyrrole/Graphene Nanocomposite

 Accurate temperature measurement is of particular importance in various medical and industrial fields. Researchers have recently developed heat-sensitive sensors with the development of nanotechnology. The goal of the present research is the fabrication of an ultra-sensitive thermal nanosensor that can be applied to monitor human body temperature and industrial tasks. 

For this purpose, polypyrrole and graphene nanocomposites were synthesized with different percentages. The structural characteristics of the obtained nanocomposites were assessed by electron scanning microscopy and X-ray diffraction spectroscopy (XRD). 

The results showed that synthetic graphene and polypyrrole are in the shape of sheets and fiber with a thickness less than 100 nm and diameter of 150 nm, respectively. The XRD spectrum of the 0.5% (by wt) nanocomposite also indicated a suitable combination of graphene and polypyrrole. The thermal biosensor evaluations of samples disclosed that pure polypyrrole allocated the first rank compared to other samples in the temperature range of 25-80°C, with a sensitivity of 218 kΩ/°C, but its nonlinear behavior limited its applicability. In this temperature range, 0.5% (by wt) nanocomposite sensor showed the highest optimal performance with the sensitivity, temperature coefficient resistance (TCR), response and recovery time of 197 kΩ/°C, -1.17 %°C-1, 78 and 170 s, respectively. In the temperature range of 35-40°C, to control the human body temperature, the nanocomposite sensor with the concentration of 0.5% (by wt) has the best linear performance with a sensitivity of 20.5 kΩ/˚C, TCR of -2.26% per°C and response and recovery times of 21 and 34 s. In  comparison to similar samples, this nanocomposite has improved by 23.9 and 1.8 times, with respective to the above recovery time. In the final conclusion, the nanocomposite sensor with a concentration of 0.5% (by wt) was designated as the most ideal nanosensor that can be utilized in industrial as well as medical fields.