Synthetic membrane technology plays an increasingly dominant role in modern industry, boasting remarkable efficiency and low carbon attributes. The ever-growing demand for molecular-level separation necessitates precise structures at the angstrom range with a concomitant low transport resistance, but it still remains a great challenge. Here, we demonstrate an enhanced separation performance towards monovalent cations of two-dimensional (2D) conjugated polymeric carbon nitride (PCN) membranes with angstrom pores, achieved through the strategic incorporation of multivalent ions. Based on the additional ions, the energy barrier of transmembrane transport for individual alkali metal ions could be effectively manipulated. Remarkably, the presence of LaCl3 substantially improves monovalent cation selectivity ratios, improving from 7 to 22 for K+/Li+ in mixtures. More importantly, under an initial concentration gradient, the transport rate of K+ was further enhanced over 1 kmol m(-2) h(-1), primarily attributed to the low ion transfer barrier.

Solid-state nanopores/nanochannels, with their high stability, tunable geometry, and controllable surface chemistry, have recently become an important tool for constructing biosensors. Compared with traditional biosensors, biosensors constructed with solid-state nanopores/nanochannels exhibit significant advantages of high sensitivity, high specificity, and high spatiotemporal resolution in the detection single entities (such as single molecules, single particles, and single cells) due to their unique nanoconfined space-induced target enrichment effect. Generally, the solid-state nanopore/nanochannel modification method is the inner wall modification, and the detection principles are the resistive pulse method and the steady-state ion current method. During the detection process, solid-state nanopore/nanochannel is easily blocked by single entities, and interfering substances easily enter the solid-state nanopore/nanochannel to generate interference signals, resulting in inaccurate measurement results. In addition, the problem of low flux in the detection process of solid-state nanopore/nanochannel, these defects limit the application of solid-state nanopore/nanochannel. In this review, we introduce the preparation and functionalization of solid-state nanopore/nanochannel, the research progress in the field of single entities sensing, and the novel sensing strategies on solving the above problems in solid-state nanopore/nanochannel single-entity sensing. At the same time, the challenges and prospects of solid-state nanopore/nanochannel for single-entity electrochemical sensing are also discussed.

Evaluating the laws of matter, life processes, and reaction kinetics from the perspective of the basic single entity elements of material, chemical, and life sciences comprises a fascinating frontier in analytical chemistry. Glass nanopipette sensing aims to detect interactions between single molecules, the physical and chemical properties of single particles, and the important roles of single cells in life systems. Currently, it is a vital branch of analytical chemistry. In this review, we introduce the preparation and characterization of glass nanopipettes, a combined detection method with a vision for a single entity, and their advances in the analysis of single molecules, single particles, and single cells.

Investigation of the heterogeneity of protein adsorption on particle surfaces has attracted enormous research attention owing to its great importance in fundamental studies and quality control. Herein we, for the first time, report a new method for label-free analysis of the heterogeneity of protein adsorption on single nanoparticles, based on particle collision events at the orifice of a nanopipette. The dwell time was strongly dependent on the amount of protein adsorbed on polystyrene particles, which could be used to analyze the heterogeneity of protein adsorption at the single particle level. This method presents a label-free, sensitive, reproducible and easily-operated way to analyze adsorption behavior at the single particle level, which opens a new approach to the study of the heterogeneity of physicochemical parameters at the surface of nanoparticles.