Ca²⁺ detection utilising AlGaN/GaN transistors with ion-selective polymer membranes

Area of Science:

• Materials Science
• Sensor Technology
• Electrochemistry

Background:

• Potentiometric ion sensors are crucial for detecting specific ions in various applications.
• Traditional ion sensors often require a reference electrode, adding complexity and cost.
• Developing reference-electrode-free sensors enhances portability and simplifies experimental setups.

Purpose of the Study:

• To demonstrate highly selective and sensitive potentiometric ion sensors for calcium ion (Ca2+) detection.
• To utilize AlGaN/GaN heterostructure-based transistors for ion sensing without a reference electrode.
• To explore the potential of these sensors for advanced multi-ion sensing applications.

Main Methods:

• Fabrication of AlGaN/GaN heterostructure-based transistor devices.
• Chemical functionalization of the gate area with poly(vinylchloride)-based (PVC) membranes selective for Ca2+.
• Potentiometric measurements of Ca2+ concentrations in various buffer solutions (KCl, NaCl, MgCl2, LiCl).

Main Results:

• Sensors exhibited stable and rapid responses to varying Ca2+ concentrations.
• Near Nernstian responses and detection limits < 10^-7 M in KCl and NaCl buffers.
• Linear response range from 10^-7 to 10^-2 M for Ca2+.
• Detection limits < 10^-6 M achieved in MgCl2 and LiCl buffers.
• Demonstrated excellent selectivity and response range for Ca2+ detection.

Conclusions:

• AlGaN/GaN-based devices offer a promising platform for highly selective and sensitive Ca2+ detection without a reference electrode.
• The developed sensors show potential for diverse applications requiring precise ion monitoring.
• This work is a significant advancement towards developing arrays of ion-selective field-effect transistor (ISFET) devices for multi-ion sensing.