Geometric Tailoring of Macroscale Ti₃C₂T_<i>x</i> MXene Lamellar Membrane for Logic Gate Circuits

Constructing nanofluidic diode nanochannels with an asymmetric structure for logic gate circuits has attracted extensive research interests. Currently, the preparation of a geometrically asymmetric nanochannel relies on cost-effective material-processing methods and has been hard to scale up, limiting the development of nanofluidic research. Herein, we introduce the idea of geometric tailoring to cut the MXene lamellar membrane in different shapes and investigate the ion transport behavior systematically. The ion rectification can be regulated by adjusting geometric factors such as the asymmetric ratio and height of the trapezoidal membrane. On the basis of the above-mentioned research on rectification characteristics, we further optimized the trapezoidal membrane into a triangular membrane on the macroscopic level and successfully applied it to logic circuits, realizing the logic operations of “AND” and “OR”. It is worth mentioning that the shape of a macrocut triangular membrane is exactly the same as the symbol of an electronic diode, and the conduction and cutoff directions of the ionic current are also exactly the same as those of electronic diodes. Our finding provides a facile and general strategy for fabricating a macroscale geometric asymmetry nanochannel-based two-dimensional lamellar membrane and shows the potential applications in complex highly integrated ionic circuits

Bio-inspired High-Performance Artificial Ion Pump Mediated by Subnanoscale Dehydration Hydration Effects

The energy conversion in plant chloroplast is carried out by pumping protons into the thylakoid for driving ATP synthesis. Inspired by ion active transport in living organisms, we attempted to design an artificial ion pump induced by subnanoconfinement effects. This ionic device uses two polarity functional nanoporous films as ion-selective valves at both ends and UiO-66 metal–organic framework-filled microchannels as ion storage cavities. In the charging process, ions could be pumped into the central cavities by nanovalves, which produced an ion gradient 10 to 100 times higher than the bulk, and were trapped within the subnanocages by dehydration. In the discharging process, the enriched ions were rehydrated and slowly released by the surface charge of the nanovalves, producing a sustainable ion current. The ion storage efficiency of this nanofluidic device could be improved to 60.3%, and the release time of ion current was also prolonged by 1 order of magnitude. This work combines the active and passive transport of ions to realize fast storage and slow release of ionic current, which provides an ion gradient-mediated novel energy conversion strategy

Self-Purification-Dependent Unique Photoluminescence Properties of YBO₃:Eu³⁺ Nanophosphors under VUV Excitation

A series of different concentrations of Eu3+ doping in YBO3 nanophosphors were successfully prepared by a surfactant-assisted solvothermal and heat-treatment process. Their photoluminescence (PL) properties were investigated under vacuum ultraviolet (VUV) and ultraviolet (UV) excitation. In comparison with the change trend of emission intensities in UV spectra, we found a unique phenomenon in the VUV spectra of YBO3:Eu3+ nanophosphors: the PL intensities are not sensitive to the activator doping concentrations. Although the doping concentrations were changed in a large range (2.5−25%), the PL intensities were maintained in a certain value. This phenomenon was also not observed in the bulk YBO3 phosphor. We gave a detailed explanation to this phenomenon by using the “self-purification” effect in nanosystems. It indicated that the activator in the nanophosphor is not a homogeneous distribution but tends to gather on the surface, which will also cause effective activator amounts for VUV luminescence to be very low