Single-Wall Carbon Nanotube-Based pH Sensor Fabricated by the Spray Method

Fabrication of carbon nanotube-based pH sensor for paper-based microfluidics

“…The average resistance before the application of the solution was 0.427 kX with the standard deviation of 0.07. Notably, the results of pH response on CNT bundles are in reasonably agreement with previous study that the CNT bundles were sprayed across the microelectrodes on silicon substrate [4]. The decrease in resistance with increase of pH is consistent with the increase of OH group-doping concentration.…”

“…Since the electrical property of CNTs is sensitive to chemicals, single CNT and CNT bundled sensors fabricated on silicon substrate have been developed to monitor the pH value of the analyte solution [4,20]. It showed that the resistance of the CNT bundles across the microelectrodes was proportional to the pH value of the analyte solution applied to the sensor.…”

“…CNT bundles can be manipulated across the microelectrodes using ac electrophoresis [3] and spray method [4] for forming a functional device. Compared to the typical atomic force microscopy (AFM) manipulation technique [22], these methods are more efficiency and low cost.…”

“…However, difficulties of processing a single CNT to be a functional device have hampered the practical realization of their excellent properties. CNT bundles have been proposed to work as an individual functional device and manipulated across the microelectrodes by ac electrophoresis [3] and spray method [4]. Thermal sensing has been demonstrated and the CNT bundled device showed very low power consumption [3].…”

Layer-by-Layer Nano Self-Assembly of pH Sensors Based on Polyelectrolytes and Carboxylated Carbon Nanotubes

“…Furthermore, there are many biochemical reactions accompanying pH changes by which the concentration of target biomolecules can be traced for bio-sensing applications. Combined with extremely sensitive electronic properties of SWNTs, pH sensors have recently been reported [8,9]. Although the pH sensing mechanism has been generally known to be protonation, it has been interpreted in different ways [7].…”