Synthesis of a Functionalized Carbon Nanotube Graphene Composite Enabling pH-Responsive Electrochemical Sensing for Biomedical Applications

Sensing of pH value plays an important role in many fields of studies including biology, chemistry, and biomedicine. In recent years, nanomaterials have emerged as a promising sensing element for a variety of applications. In this study, we report a high-sensitivity pH sensor synthesized by a functionalized single-wall carbon nanotube graphene (FSWCNT/G) composite. This sensor was constructed with Cr/Au electrodes and FSWCNT/G sealed in a PDMS microchannel on a glass substrate. The experiments of a field-effect transistor (FET), linear sweep voltammetry (LSV), and response time measurement all proved the superiority of the fabricated composite sensor over a pristine graphene sensor. A high potentiometric gradient of 98.75 mV/pH within the operating pH range of 4–10 was obtained in direct potentiometric measurements. The composite nanosensor can be used to monitor the pH value in cancer cell solution. Moreover, the composite nanosensor was tested for cancer cell detection, and the range of the concentration detection was from 5 × 10 6 to 2.5 × 10 5 cells/mL, showing a potential way to achieve label-free cell detection.