Quantitative detection of protein using a top-gate carbon nanotube field effect transistor

High-stability sensing of proteins of pig serum albumin (PSA) was achieved using an insulator-covered carbon-nanotube field-effect transistor (CNT-FET) with a top-gate structure. The sensitivity limit of this CNT-FET PSA sensor is at least 5 nmol/L PSA solution. A layer of silicon nitride deposited on the top-gate structure provides an n-type characteristic and a highly stable CNT-FET. Since the CNT is covered with a silicon nitride layer, it is isolated from oxygen, water, and other contaminants. The equilibrium constant of the PSA/anti-PSA reaction, which indicates the strength of the binding energy between PSA and anti-PSA fixed on the Au top-gate electrode, was calculated to be 1.2 x 10(7) L/mol using the Langmuir equation fitting.