Inspired by green chlorophyll pigments in photosynthetic systems that have the inherent ability to harvest solar energy and generate electrons, a photoelectric gated nanochannel system that efficiently converts photon energy into electricity with adjustable ionic conductivity is demonstrated. The nanochannel system is achieved by grafting photoresponsive ruthenium complex molecules (N3 molecules) onto bullet shaped Al2O3 nanochannels forming an organic/inorganic composite. The bullet shaped Al2O3 nanochannels working as an asymmetric rigid scaffold allow the composite nanochannels to mimic ionic current rectification (ICR) properties. The deprotonation of free carboxylic acid moieties on the N3 molecular backbone upon increasing the pH enhanced the surface charge density of the inner walls of the channels, which contributes to pH-tunable ion rectification. Furthermore, the excited state N3 molecule has a higher value for than that of the ground state pKa, thus resulting in a better photo-responsive capability of the nanochannels at higher pH values, which are used to develop a photoelectric-and-pH cooperatively controlled ion gating switch with better performance. At pH 7 and the photon-on state, the composite channel is in the ON state, while, at pH 4 and the photon-off state, the ion current is in the OFF state. This facile and environmentally friendly stimulus-responsive system may provide a new strategy to further design and develop future photon harvesting nanochannel systems for mimicking the more comprehensive process of photosynthesis.

Biomimetic dual-ion-responsive nanochannels were developed by the principles of metal-ion-mediated base pairs of the responsive T-/C-rich single strand DNA (ssDNA). The responsive ssDNA was immobilized into the funnel-shaped alumina nanochannels, which were fabricated using the anodization technology and pore-widening process. In neutral solution, the conformation of the ssDNA changed from a loosely packed structure into a duplex structure by interacting with Hg2+ or Ag+ ions (T–Hg2+–T or C–Ag+–C complexes). The decreasing ionic currents through the nanochannels were utilized to detect concentrations of Hg2+ or Ag+ ions. The conversion of duplex-quadruplex of Ag+ ions and DNA could be triggered by changing the pH value of aqueous solutions to 4.5, whereas it did not happen in Hg2+ ions solution. Thus, the ssDNA-modified alumina nanochannels selectively responded to Hg2+ and Ag+ ions at pH 4.5 with different ionic transportation properties. The biomimetic dual-ion-responsive nanochannels promised great potential in multiplexed ion sensing.

In this work, the synthetic alumina nanochannels with bi-, tri-, and tetra-branched geometry structures exhibited ionic current rectifications with nonlinear I–V curves. Such diode performance of the branched alumina nanochannel is mainly dependent on the cooperative asymmetry of the branched structure and the surface-charge distribution on inner walls. By regulating the geometry, electrolyte pH, and solution concentration, the tunable ionic rectification properties are effectively obtained including both the rectification ratios and the rectifying direction that were deduced from the converted ion selectivity. This nanofluidic diode may open up a new opportunity for the application of the complex nanofluidic devices in contrast to previously reported channels to provide molecular analysis, controlled mass transport, drug release, and various logic gate operations.Keywords: branched alumina nanochannel; concentration; cooperative asymmetry; nanofluidic diode; pH; tunable ionic rectification;

ZnO and ZnS composited tri-crystal nanoribbons were fabricated by one-step thermal evaporation of ZnS and CuO powders. The tri-crystal nanoribbons have typical length of about 10 μm and width of 100–300 nm. The tri-crystal nanoribbon was composed of three intersected nanoribbons by 120°, which had a thickness of 50 nm with a growth direction along [10–10]. The rough nanoribbon contained several grains and the averaged elemental enrichment of Zn:O:S was 1:0.72:0.28. The tri-crystal nanoribbons exhibited three emission peaks at room temperature, which are associated to band gap and defect emissions of ZnO and ZnS. This 3D composited nanocrystal has potential applications in optoelectronics and energy-harvesting devices.

Biomimetic dual-ion-responsive nanochannels were developed by the principles of metal-ion-mediated base pairs of the responsive T-/C-rich single strand DNA (ssDNA). The responsive ssDNA was immobilized into the funnel-shaped alumina nanochannels, which were fabricated using the anodization technology and pore-widening process. In neutral solution, the conformation of the ssDNA changed from a loosely packed structure into a duplex structure by interacting with Hg2+ or Ag+ ions (T–Hg2+–T or C–Ag+–C complexes). The decreasing ionic currents through the nanochannels were utilized to detect concentrations of Hg2+ or Ag+ ions. The conversion of duplex-quadruplex of Ag+ ions and DNA could be triggered by changing the pH value of aqueous solutions to 4.5, whereas it did not happen in Hg2+ ions solution. Thus, the ssDNA-modified alumina nanochannels selectively responded to Hg2+ and Ag+ ions at pH 4.5 with different ionic transportation properties. The biomimetic dual-ion-responsive nanochannels promised great potential in multiplexed ion sensing.