Apparent pH sensitivity of solution-gated graphene transistors.

Area of Science:

• Materials Science
• Nanotechnology
• Chemical Sensing

Background:

• Solution-gated graphene transistors (SGGTs) are emerging as promising candidates for pH sensing applications.
• SGGT operation is primarily attributed to the influence of hydronium and hydroxide ions on graphene's electrical properties.

Purpose of the Study:

• To investigate the impact of various ionic species, beyond hydronium and hydroxide, on the pH response of SGGTs.
• To elucidate the role of buffer composition and concentration in the observed Dirac voltage shifts in graphene transistors.

Main Methods:

• Fabrication of solution-gated graphene transistors.
• Testing device performance using a series of carefully designed pH buffer solutions with varying ionic compositions and concentrations.
• Monitoring the pH-dependent Dirac voltage (VDirac) shift as the primary sensing indicator.

Main Results:

• The magnitude and direction of the pH-dependent VDirac shift are significantly influenced by the concentration and specific ionic species present in the buffer solutions.
• Observed VDirac shifts do not solely correlate with changes in pH but are also affected by the presence of counter-ions and other buffer components.

Conclusions:

• The interpretation of pH sensing in SGGTs requires consideration of contributions from all ionic species in the solution, not just H+ and OH-.
• Buffer composition and ionic strength play a critical role in the apparent pH response of graphene-based sensors, necessitating careful selection for accurate measurements.