Ion-Selective Membrane-Coated Graphene-Hexagonal Boron Nitride Heterostructures for Field-Effect Ion Sensing.

Area of Science:

• Materials Science
• Nanotechnology
• Biomedical Engineering

Background:

• Graphene's unique properties, including high ion sensitivity and sp-hybridized carbon structure, make it suitable for ion-sensitive field-effect transistors (ISFETs).
• Existing ISFETs face challenges in achieving stable solid-liquid interfaces and high selectivity for specific ions.

Purpose of the Study:

• To evaluate the performance of graphene field-effect transistors (GFETs) coated with ion-selective membranes for detecting Ca2+, K+, and Na+ ions.
• To compare the ion selectivity of transconductance versus Dirac voltage measurements in GFETs.
• To investigate the impact of hexagonal boron nitride (hBN) interlayers on GFET ion sensitivity and selectivity.

Main Methods:

• Fabrication of GFETs with ion-selective membranes for detecting Ca2+, K+, and Na+.
• Measurement of Dirac point shift and transconductance as a function of ion concentration in various salt solutions and buffered Locke's solution.
• Incorporation of hexagonal boron nitride (hBN) multilayers between graphene and the oxide layer.

Main Results:

• GFETs demonstrated high repeatability (>99.5%) and reproducibility (>98%) over 60 days for ion concentration detection.
• Transconductance measurements showed an order of magnitude enhancement in ion selectivity compared to Dirac voltage.
• The inclusion of an hBN interlayer significantly improved both ion sensitivity and selectivity of transconductance.

Conclusions:

• GFETs with ion-selective membranes are effective for selective ion detection, with transconductance offering superior selectivity.
• Hexagonal boron nitride interlayers enhance the performance of GFET-based sensors.
• These findings support the exploration of GFET arrays for advanced biomedical sensing applications.