Recently, there have been many studies on the wide use of MOS-FET pH sensors modified with functionalized carbon nanotubes. However, no comprehensive and detailed study on the OH and N functionalization and pH sensing properties of multi-walled carbon nanotubes (MWCNT) has been found in the literature.
Pak Il Man, a section head at the General Assay Office, has studied the OH and N functionalization of MWCNTs and investigated their pH-sensing properties by modifying functionalized carbon nanotubes onto MOS-FETs.
First, he boiled MWCNTs in 63% HNO3 (analytically pure) at 120℃ for 40h, and filtered and washed them with deionized water to perform OH functionalization. Then, he carried out treatments by boiling them in 20% liquid ammonia and 0.1% gelatin solution, respectively, and by applying ultrasonic dispersion to the samples boiled in gelatin solution and conducting ultrasonic dispersion in 0.1% gelatin solution, respectively, to investigate the N functionalization properties.
He investigated the pH characteristics by modifying the MOS-FET drain with functionalized carbon nanotubes, and found that the pH-sensitive linear range of MOS-FET modified with N-functionalized carbon nanotubes was longer than that of MOS-FET modified with OH-functionalized carbon nanotubes.
As the pH sensor based on this is a strike and temperature resistant integral solid, it is possible to measure pH accurately in a coarse suspension that is stirred in a closed container or in a high temperature solution.
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