Bioinspired Solid-State Nanochannel Sensors: From Ionic Current Signals, Current, and Fluorescence Dual Signals to Faraday Current Signals

Inspired from bioprotein channels of living organisms, constructing "abiotic" analogues, solid-state nanochannels, to achieve "smart" sensing towards various targets, is highly seductive. When encountered with certain stimuli, dynamic switch of terminal modified probes in terms of surface charge, conformation, fluorescence property, electric potential as well as wettability can be monitored via transmembrane ionic current, fluorescence intensity, faraday current signals of nanochannels and so on. Herein, the modification methodologies of nanochannels and targets-detecting application are summarized in ions, small molecules, as well as biomolecules, and systematically reviewed are the nanochannel-based detection means including 1) by transmembrane current signals; 2) by the coordination of current- and fluorescence-dual signals; 3) by faraday current signals from nanochannel-based electrode. The coordination of current and fluorescence dual signals offers great benefits for synchronous temporal and spatial monitoring. Faraday signals enable the nanoelectrode to monitor both redox and non-redox components. Notably, by incorporation with confined effect of tip region of a needle-like nanopipette, glorious in-vivo monitoring is conferred on the nanopipette detector at high temporal-spatial resolution. In addition, some outlooks for future application in reliable practical samples analysis and leading research endeavors in the related fantastic fields are provided.

UV-irradiation assisted functionalization and binding of Pd nanoparticles in polycarbonate membranes for hydrogen separation

For hydrogen-based energy systems development, purified hydrogen (H₂) is a basic requirement and it can be achieved by using the H₂-selective membranes. For having H₂-selective membranes, it is a decent approach to embed the H₂-sensitive materials in the polymeric membranes. Palladium (Pd) is one of the widely used materials for hydrogen-selective membranes due to its strong affinity towards H₂ absorption. In the present work, we have used Pd nanoparticles in UV-functionalized track-etched polycarbonate (PC) membranes for better selectivity and permeability of H₂ gas. In the UV-irradiation process of membranes, the photo-fries mechanism leads to the C-O bond breaking from the carbonate group of PC molecules and as a result, there is a high number of bond breaking. This phenomenon provides the more active sites for the attachment of Pd nanoparticles in comparison with the pristine PC membrane. The gas permeability of these membranes suggests that the selectivity of H₂ over nitrogen (N₂) and carbon dioxide (CO₂) is increased by the addition of uniformly distributed Pd nanoparticles in the functionalized membranes.