An All-Solid-State pH Sensor Employing Fluorine-Terminated Polycrystalline Boron-Doped Diamond as a pH-Insensitive Solution-Gate Field-Effect Transistor

Abstract

A fluorine-terminated polycrystalline boron-doped diamond surface is successfully employed as a pH-insensitive SGFET (solution-gate field-effect transistor) for an all-solid-state pH sensor. The fluorinated polycrystalline boron-doped diamond (BDD) channel possesses a pH-insensitivity of less than 3mV/pH compared with a pH-sensitive oxygenated channel. With differential FET (field-effect transistor) sensing, a sensitivity of 27 mv/pH was obtained in the pH range of 2–10; therefore, it demonstrated excellent performance for an all-solid-state pH sensor with a pH-sensitive oxygen-terminated polycrystalline BDD SGFET and a platinum quasi-reference electrode, respectively.

Deoxyribonucleic-acid-sensitive Polycrystalline Diamond Solutiongate Field-effect Transistor with a Carboxyl-terminated Borondoped Channel

“…Polycrystalline diamond SGFETs were fabricated by a process described in our previous work. 14,16,[20][21][22] Following boron-doped polycrystalline diamond film deposition, two electrical contact pads of 200-nm gold on 30-nm titanium were deposited as a source/drain electrode using an electron beam evaporator (EB evaporation Model A500; Edwards). The electrical contact pads were positioned to give a 10-mm channel length and a 500-μm channel width.…”

“…To advance the commercial viability of diamond sensors, a polycrystalline diamond with an oxygen-terminated surface was also applied in our previous work. 14,[18][19][20][21] In this study, to verify the superiority and viability of an oxygen-terminated polycrystalline diamond surface with a boron-doped layer for biosensor, a partial carboxyl-termination was introduced for the polycrystalline diamond SGFET. A ss-DNA probe was immobilized on the polycrystalline diamond surface via amino coupling.…”

Ion-Sensitive Stainless Steel Vessel for All-Solid- State pH Sensing System Incorporating pH-Insensitive Diamond Solution Gate Field-Effect Transistors

“…We have reported diamond SGFETs where the semiconductor surface was directly immersed in electrolyte solutions and the drain current was controlled by an electric double layer capacitor at the diamond surface [10]. We have also reported diamond SGFETs utilizing various functional groups including hydrogen, oxygen, nitrogen, and fluorine to achieve excellent pH sensing capabilities or complete pH insensitivity [11][12][13][14][15]. Like most ISFETs, a silver/silver chloride (Ag/AgCl) reference electrode has been commonly used as the gate electrode for diamond SGFETs.…”

Over 59 mV pH−1 Sensitivity with Fluorocarbon Thin Film via Fluorine Termination for pH Sensing Using Boron‐Doped Diamond Solution‐Gate Field‐Effect Transistors

“…[7][8][9] We have also reported pH insensitive results with fluorinated-diamond SGFETs where the diamond surface is dominated by C─F bonding. [10] Comparing with the C─F layer, fluorocarbon thin film is fabricated by layers of C─CF, C─F, C─F 2 , and C─F 3 , and can be considered as conducting polymers. Conducting polymers have recently attracted much attention in chemical sensing applications owing to their unique electrical properties.…”