Damage-free hydrogenation of graphene via ion energy control in plasma

We proposed appropriate plasma conditions for hydrogenation of graphene without structural defect formation using ion energy analysis. Graphene sheets were exposed to plasma having H3+ ions with energies of 3.45, 5.35, and 7.45 eV. Only the specimen treated by the plasma with the lowest energy was converted back to graphene by thermal annealing, and the others showed irreversible characteristics because of the vacancy defects generated by high-energy ions. Finally, we demonstrated the reversible characteristic in graphene field-effect transistor using the plasma with appropriate ion energy and Joule heating, indicating that damage induced by plasma was negligible.

DNA hydrogel to improve solution-gate graphene field effect transistor in all-solid-state

The solution-gate graphene field effect transistor (Sg-GFET), as a popular sensing platform, its applications are still hindered by the deficiency in all-solid-state, due to the dependence on liquid-state gate-dielectric. Inspired by DNA hydrogel which can provide microporous architecture to accommodate the fluidic analyte, moreover, its combination with graphene is believed to foster electron transport in the field of electrochemistry. We are interested to take advantage of DNA hydrogel's solid-state and capability for holding solution, and investigate whether it can replace the traditional solution. So pure DNA hydrogel, their complexes with GO (GO/DNA hydrogel) and RGO (RGO/DNA hydrogel) are studied herein. Their micro-porous 3D morphologies are demonstrated, their influences on the electrical characteristics of GFETs are carefully examined and proved to be able to maintain the typical bipolarity of Sg-GFET, firstly. Then, pure DNA hydrogel and GO/DNA hydrogel are selected as the optimized gate-dielectrics, because of their renewability after dehydration. Furthermore, by using aptamer-based heavy metal ions (Pb2+ and Hg2+) detections as proof-of-concept, the strategies for building the sensing platform based on the optimized hydrogel dielectric-gated GFETs are studied. It is found, for the purpose of substituting fluidic dielectric in traditional Sg-GFET, the scheme of directly mounting aptamer on graphene channel and coating pure DNA hydrogel on it is demonstrated to be better than the strategies of using GO/DNA hydrogel and hybriding aptamer probes in hydrogel scaffold. It is explained according to surface charge sensing mechanism. At last, the performances of the sensing platform based on the proposed DNA hydrogel gated GFETs are testified by the detections and selectivity examinations for Pb2+ and Hg2+. Conclusively, pure DNA hydrogel is expected to be a promising candidate in the future all-solid-state Sg-GFET.