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

An intrinsic ion sensitivity exceeding the Nernst-Boltzmann limit and an sp -hybridized carbon structure make graphene a promising channel material for realizing ion-sensitive field-effect transistors with a stable solid-liquid interface under biased conditions in buffered salt solutions. Here, we examine the performance of graphene field-effect transistors coated with ion-selective membranes as a tool to selectively detect changes in concentrations of Ca, K, and Na in individual salt solutions as well as in buffered Locke's solution. Both the shift in the Dirac point and transconductance could be measured as a function of ion concentration with repeatability exceeding 99.

Ion Sensing with Solution-Gated Graphene Field-Effect Sensors in the Frequency Domain.

Here, we examine the concept of frequency domain sensing with solution-gated graphene field-effect transistors, where a sine wave of primary frequency (1f) was applied at the gate and modulation of the power spectral density (PSD) of the drain-source current at 1f, 2f, and 3f was examined as the salt in the gate electrolyte was switched from KCl to CaCl, and their concentrations were varied. The PSD at 1f, 2f, and 3f increased with the concentration of KCl or CaCl, with the PSD at 1f being the most sensitive. We further correlated these changes to the shift in Dirac point.

Few-Flakes Reduced Graphene Oxide Sensors for Organic Vapors with a High Signal-to-Noise Ratio.

This paper reports our findings on how to prepare a graphene oxide-based gas sensor for sensing fast pulses of volatile organic compounds with a better signal-to-noise ratio. We use rapid acetone pulses of varying concentrations to test the sensors. First, we compare the effect of graphene oxide deposition method (dielectrophoresis versus solvent evaporation) on the sensor's response.