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Artificial nanofluidic channels that achieve light-driven ion transport in biological systems based on photoelectric effect have attracted significant attention for signal transduction and light energy conversion. However, the light-responsive performance is limited by the charge separation efficiency on the surface of the channels. Herein, we introduce semiconductor p–n junctions into nanofluidic channels to enhance their light-driven ion transport. The p–n junction is formed by an n-type titanium dioxide (TiO2) nanoparticles layer on an electrochemically fabricated p-type polypyrrole (PPy) membrane. The light-induced charge separation at p–n junctions increases the surface charge density of the positively charged PPy membrane. Consequently, the light-driven ion current through the nanofluidic channels is enhanced from 79.6 to 111.9 nA by 40.6% when compared with a single-component p-type PPy membrane. The proof-of-concept demonstration of enhanced light-driven ion transport by semiconductor p–n junctions provides a route toward high-performance light-responsive nanofluidic channels, which demonstrates potential applications for light-controlled mass transport, signal transduction, and energy conversion. [ABSTRACT FROM AUTHOR]

The confinement effect of biological ion channels regulates the transport of molecules and ions due to angstrom-sized pores. The structure of the potassium channel has a selection region (3-4 Å), a cavity (10 Å), and a gated region, while ZIF-8 has intrinsic pores with a 3.4 Å aperture and an 11.6 Å cavity similar to those of the potassium channel. Inspired by this, we constructed the glass/ZIF-8 hybrid membrane through an electrochemical growth process to explore the kinetics of the ion transmembrane by I - V curves and electrochemical impedance spectroscopy. These complementary approaches yield highly correlated results that show that ion transportation of the ZIF-8 membrane follows Arrhenius behavior. The rates of ions are controlled by the transmembrane activation energy, in which the ionic charge and radius play an important role.