With the miniaturization of electronic devices, it is essential to achieve higher carrier density and lower operation voltage in field-effect transistors (FETs). However, this is a great challenge in conventional FETs owing to the low capacitance and electric breakdown of gate dielectrics. Recently, electric double-layer technology with ultra-high charge-carrier accumulation at the semiconductor channel/electrolyte interface has been creatively introduced into transistors to overcome this problem. Some interesting electrical transport characteristics such as superconductivity, metal-insulator transition, and tunable thermoelectric behavior have been modulated both theoretically and experimentally in electric double-layer transistors (EDLTs) with various semiconductor channel layers and electrolyte materials. The present article is a review of the recent progress in the EDLTs and the impacts of EDLT technology on modulating the charge transportation of various electronics.

Although the reversible wettability transition between hydrophobic and hydrophilic graphene under ultraviolet (UV) irradiation has been observed, the mechanism for this phenomenon remains unclear. In this work, experimental and theoretical investigations demonstrate that the H2O molecules are split into hydrogen and hydroxyl radicals, which are then captured by the graphene surface through chemical binding in an ambient environment under UV irradiation. The dissociative adsorption of H2O molecules induces the wettability transition in graphene from hydrophobic to hydrophilic. Our discovery may hold promise for the potential application of graphene in water splitting.

The discovery of graphene has inspired great research interest in two-dimensional (2D) layered nanomaterials during the past decade. As one of the newest members in 2D layered nanomaterials family, black phosphorus (BP), with puckered structure similar to graphene, has shown great potential in novel nanoelectronics owing to its thickness-dependent bandgap. Especially, the unique in-plane anisotropy and high carrier mobility enable BP to be a promising candidate for field-effect transistor (FET) applications. In addition, monolayer or few-layer BP can be combined into van de Waal heterostructures and this opens up a pathway for overcoming existing problems such as impurity scattering and surface degradation or achieving functionalities. In this article, we will review typical physical and chemical properties of BP and provide an overview of the recent development in BP-based transistors. With this review, we also discuss the current challenges in BP transistors and future research directions.2 interactions between adjacent layers. 3 For example, as a typical representative of transition metal dichaldogenides (TMDs), MoS 2 with a relatively large intrinsic bandgap of 1.8 eV shows superior on/off ratio and ultralow standby power dissipation. 4 Generally, MoS 2 exhibits n-type characteristics because of the presence of S vacancies and strong Fermi-level pinning near the conduction band, 5 and has great potential in practical electronic and optoelectronic applications. 6 However, in spite of many promising theoretical predications, the observed mobility of TMDs based device is still relatively low due to the heavy effective mass of carriers and the scattering mechanisms, especially the phonon scattering at room temperature. 7, 8 Thus, the majority of TMDs materials have not been demonstrated for high-performance radio frequency (RF) transistors. 3At the beginning of 2014, black phosphorus (BP), one of the latest members of 2D layered semiconducting materials has been rediscovered from the perspective of 2D materials for transistors. 9 Although BP was discovered a century ago, there have been only a few studies focusing on the utilization of BP due to the difficulty in synthesis. 10 Recently, it has been found that the moderate and tunable bandgap of BP provides an alternative for next generation nanoelectronic applications. Similar to graphene, single-layered or few-layered black phosphorus can be obtained by mechanical exfoliation and they exhibit unexpected properties compared with their bulk counterpart. Moreover, as a single-elemental layered material, BP possesses lower spin-orbit coupling because of relatively lighter phosphorus atom, which is more favourable for spin transport. 11The atomic structure and properties of main 2D layered materials are listed in Table 1, in which we select MoS 2 as a representative of TMDs. We also highlight hexagonal boron nitride (h-BN) as a graphite-type structured material, which a good gate insulator for 2D materials based FETs because of its ultra-flat and charged impurity-fre...