Recent advance in solid state nanopores modification and characterization

Nanopore, due to its advantages of modifiable, controllability and sensitivity, has made a splash in recent years in the fields of biomolecular sequencing, small molecule detection, salt differential power generation, and biomimetic ion channels, etc. In these applications, the role of chemical or biological modification is indispensable. Compared with small molecules, the modification of polymers is more difficult and the methods are more diverse. Choosing appropriate modification method directly determines the success or not of the research, therefore, it is necessary to summarize the polymer modification methods toward nanopores. In addition, it is also important to provide clear and convincing evidence that the nanopore modification is successful, the corresponding characterization methods are also indispensable. Therefore, this review will summarize the methods of polymer modification of nanopores and efficient characterization methods. And we hope that this review will provide some reference value for like-minded researchers.

Engineering a Smart Nanofluidic Sensor for High-Performance Peroxynitrite Sensing through a Spirocyclic Ring Open/Close Reaction Strategy

Peroxynitrite (ONOO^-) is an important reactive oxygen/nitrogen species that participates in a range of physiological and pathological processes by modulating ion flux through biological channels. Inspired by a ONOO^--regulated K⁺ channel in vivo, herein, we describe the construction of a smart ONOO^--driven nanosensor using a spirocyclic ring open/close reaction approach. The prepared nanosensor possessed a prominent ONOO^- selectivity and sensitivity and rapid response (∼90 s) owing to the specific reaction between ONOO^- and ligands on the nanosensor surface with a high ion rectification ratio (∼10) and ion gating ratio (∼4). Moreover, this nanosensor system also exhibits excellent stability and recyclability. Thus, these results will provide a new direction for the design of nanochannel-based sensors for future practical and biological applications.

Nanopore gates via reversible crosslinking of polymer brushes: a theoretical study

Polymer-brush-modified nanopores are synthetic structures inspired by the gated transport exhibited by their biological counterparts. This work theoretically analyzes how the reversible crosslinking of a polymer network by soluble species can be used to control transport through nanochannels and pores. The study was performed with a molecular theory that allows inhomogeneities in the three spatial dimensions and explicitly takes into account the size, shape and conformations of all molecular species, considers the intermolecular interactions between the polymers and the soluble crosslinkers and includes the presence of a translocating particle inside the pore. It is shown than increasing the concentration of the soluble crosslinkers in bulk solution leads to a gradual increase of its number within the pore until a critical bulk concentration is reached. At the critical concentration, the number of crosslinkers inside the pore increases abruptly. For long chains, this sudden transition triggers the collapse of the polymer brush to the center of the nanopore. The resulting structure increases the free-energy barrier that a translocating particle has to surmount to go across the pore and modifies the route of translocation from the axis of the pore to its walls. On the other hand, for short polymer chains the crosslinkers trigger the collapse of the brush to the pore walls, which reduces the translocation barrier.

Size and density adjustment of nanostructures in nanochannels for screening performance improvement

Biomimetic solid-state nanochannel/nanopore with flexible geometric structures, mechanical robustness and multifunctional surfaces have attracted extensive attention in separation, catalysis, drug delivery and other fields. Nanostructures have been introduced in nanoconfines to compress substances passthrough for high-efficient screening. However, precise controls of the nanostructure's growth in nanoconfines is rare. Herein, we developed a method to control size and number density of nanoparticles in nanochannels by adjusting polydopamine reducing conditions, achieving (1) particle size increasing, density increasing; (2) particle size increasing, density decreasing; (3) particle size increasing, density invariant; (4) particle size invariant, density increasing. The nanoparticles compressed the space of functional molecules decorated on them. Increasing size and density of nanoparticle enhanced the steric hinderance of functional molecules decorated on them and improved the wetting and chirality screening through nanochannels.

Asymmetric coupling of Au nanospheres on TiO2 nanochannel membranes for NIR-gated artificial ionic nanochannels

Au nanospheres are selectively formed at one tip of TiO₂ nanochannels by combining a photocatalytic reaction with limited penetration of light. The closed–open switching behavior of the temperature-responsive polymer is achieved under NIR irradiation.

pH- and light-regulated ion transport in hourglass shaped Al2O3 nanochannels patterned with N719 and APTES

An investigation of the pH- and light-regulated ion rectification properties of symmetric and asymmetric Al₂O₃ nanochannels patterned with N719 and APTES at designated positions.