Graphene transistors are insensitive to pH changes in solution

We observe very small gate-voltage shifts in the transfer characteristic of as-prepared graphene field-effect transistors (GFETs) when the pH of the buffer is changed. This observation is in strong contrast to Si-based ion-sensitive FETs. The low gate-shift of a GFET can be further reduced if the graphene surface is covered with a hydrophobic fluorobenzene layer. If a thin Al-oxide layer is applied instead, the opposite happens. This suggests that clean graphene does not sense the chemical potential of protons. A GFET can therefore be used as a reference electrode in an aqueous electrolyte. Our finding sheds light on the large variety of pH-induced gate shifts that have been published for GFETs in the recent literature

Data-Driven Induction of Shadowed Sets Based on Grade of Fuzziness

We propose a procedure devoted to the induction of a shadowed set through the post-processing of a fuzzy set, which in turn is learned from labeled data. More precisely, the fuzzy set is inferred using a modified support vector clustering algorithm, enriched in order to optimize the fuzziness grade. Finally, the fuzzy set is transformed into a shadowed set through application of an optimal alpha-cut. The procedure is tested on synthetic and real-world datasets

Dual gated silicon nanowire field effect transistors

Silicon Nanowire field effect transistors (SiNWFETs) are ideal candidates for basic sensing units. We report here on a top down fabrication process in SOI wafers yielding SiNWFETs. We operate the SiNWFETs in a liquid cell and control their operation with two gates: a liquid gate and a back gate. We compare the combined effects of the two gates (dual gating) on the transport characteristics in electrolytes and show that both gates are essential to perform well-defined sensing experiments

Signal-to-noise ratio in dual-gated silicon nanoribbon field-effect sensors

Recent studies on nanoscale field-effect sensors reveal the crucial importance of the low-frequency noise for determining the ultimate detection limit. In this letter, the 1/f-type noise of Si nanoribbon field-effect sensors is investigated. We demonstrate that the signal-to-noise ratio can be increased by almost two orders of magnitude if the nanoribbon is operated in an optimal gate voltage range. In this case, the additional noise contribution from the contact regions is minimized, and an accuracy of 0.5% of a pH shift in 1 Hz bandwidth can be reached. (C) 2011 American Institute of Physics. [doi:10.1063/1.3536674

Engel Expansions of q-Series By Computer Algebra

The q-Engel Expansion is an algorithm that leads to unique series expansions of q-series. Various examples related to classical partition theorems, including the Rogers-Ramanujan identities together with the elegant generalization found by Garrett, Ismail and Stanton, have been described recently. The object of this paper is to present the computer algebra package Engel, written in Mathematica, that has already played a significant role in this work. The package now is made freely available via the web and should help to intensify research in this new branch of q-series theory. Among various illustrative examples we present a new infinite Rogers-Ramanujan type family that has been discovered by using..