Ion-selective nanoporous two-dimensional (2D) materials have shown extraordinary potential in energy conversion, ion separation, and nanofluidic devices; however, different applications require diverse nanochannel devices with different ion selectivity, which is limited by sample preparation and experimental techniques. Herein, we develop a heterogeneous graphene-based polyethylene terephthalate nanochannel (GPETNC) with controllable ion sieving to overcome those difficulties. Simply by adjusting the applied voltage, ion selectivity among K+, Na+, Li+, Ca2+, and Mg2+ of the GPETNC can be immediately tuned. At negative voltages, the GPETNC serves as a mono/divalent ion selective device by impeding most divalent cations to transport through; at positive voltages, it mimics a biological K+ nanochannel, which conducts K+ much more rapidly than the other ions with K+/ions selectivity up to about 4.6. Besides, the GPETNC also exhibits the promise as a cation-responsive nanofluidic diode with the ability to rectify ion currents. Theoretical calculations indicate that the voltage-dependent ion enrichment/depletion inside the GPETNC affects the effective surface charge density of the utilized graphene subnanopores and thus leads to the electrically controllable ion sieving. This work provides ways to develop heterogeneous nanochannels with tunable ion selectivity toward broad applications.
Hardness and indentation fracture toughness of La0.8Ti0.1Ga0.1Fe3CoSb12 can be improved by in situ formed Fe3Si, without sacrificing thermoelectric properties.
Mechanical properties of gallium nitride (GaN) single crystals upon carbon ion irradiation are examined using nanoindentation analysis at room temperature. Pop-in events in the load-depth curves are observed for unirradiated and irradiated GaN samples. A statistical linear relationship between the critical indentation load for the occurrence of the pop-in event and the associated displacement jump is exhibited. Both the slope of linear regression and the measured hardness increase monotonically to the ion fluence, which can be described by logistic equations. Moreover, a linear relationship between the regression slope as a micromechanical characterization and the hardness as a macroscopic mechanical property is constructed. It is also found that the maximum resolved shear stress of the irradiated samples is larger than that of the unirradiated samples, as the dislocation loops are pinned by the irradiation-induced defects. Our results indicate that the nanoindentation pop-in phenomenon combined with a statistical analysis can serve as a characterization method for the mechanical properties of ion-irradiated materials.
Proton detection has attracted immense interest recently, owing to the increasing demands for applications in physics, medicine, and space. However, the proton detectors suffer from a general problem of performance degradation caused by the proton irradiation-induced defects over long-term operation. Herein, we report a proton detector based on the methylammonium lead tribromide (MAPbBr 3 ) perovskite single crystal, which exhibits remarkable radiation tolerance. The detector can monitor the fluence rate and dose quantitatively up to a high dose of 45 kGy with a fairly low bias electric field (0.01 V μm −1 ). Further increasing the dose to 1 MGy (7.3 × 10 13 p cm −2 ) results in the detector dark current degrading gradually, but the dark current can rapidly recover at room temperature in a few hours after irradiation, showing a desirable self-healing characteristic, which can further enhance the radiation tolerance of the detector. These results show that this perovskite-based proton detector is highly promising for future applications in proton therapy, proton radiography, and so forth.
Electronic devices based on two-dimensional materials
are promising
for application in space instrumentation because of their small size
and low power consumption, and irradiation tolerance of these devices
is required because of the existence of energetic particles in aerospace
conditions. We investigate the performance degradation of graphene
field effect transistors (GFETs) with 3 MeV protons by using an in
situ irradiation facility. Our results indicate that GFET performance
degraded severely at the ion fluence of 8 × 1011 cm
–2. Surprisingly, although the performance
of the proton-irradiated GFETs is difficult to recover in vacuum,
it can nearly completely recover within hours when the GFET is moved
into an air environment, indicating that the performance change is
due to the charge accumulation in SiO2 under proton irradiation
rather than the lattice damage of graphene. Our results have great
importance for the application of 2D devices in aerospace and other
radiative environments.
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