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The mass transport behavior through nanoscale channels, greatly influenced by the structures and dynamics of nanoconfined water, plays an essential role in many biophysical processes. However, the dynamics of nanoconfined water under an external field and its effects are still not fully understood. Here, on the basis of molecular dynamics simulations, we theoretically show that the ionic current of [Bmim][PF6] through narrow pores in graphene membrane exhibits an ionic negative differential resistance effect—the ionic current decreases as the voltage increases over a certain threshold. This effect arises from the violation of traditional fluid dynamics as the assumption of continuity and homogeneity of fluids is no longer effective in ultrathin nanopores. The gradient of electric field around the atomic-thin layer produces a strong gradient force on the polarized water inside the nanopore. This dielectrophoretically compressed water leads to a hydrostatic force that repels ions from entering the nanopore. Our findings may advance the understanding of hydrostatic mechanism, which governs ion transport through nanopores. [ABSTRACT FROM AUTHOR]

Author(s): Jinrun Dong [sup.1] , Yuxian Lu [sup.1] , Yang Xu [sup.1] , Fanfan Chen [sup.1] , Jinmei Yang [sup.1] , Yuang Chen [sup.1] , Jiandong Feng [sup.1] Author Affiliations: [...], Chemical reactions tend to be conceptualized in terms of individual molecules transforming into products, but are usually observed in experiments that probe the average behaviour of the ensemble. Single-molecule methods move beyond ensemble averages and reveal the statistical distribution of reaction positions, pathways and dynamics.sup.1-3. This has been shown with optical traps and scanning probe microscopy manipulating and observing individual reactions at defined locations with high spatial resolution.sup.4,5, and with modern optical methods using ultrasensitive photodetectors.sup.3,6,7 that enable high-throughput single-molecule measurements. However, effective probing of single-molecule solution chemistry remains challenging. Here we demonstrate optical imaging of single-molecule electrochemical reactions.sup.7 in aqueous solution and its use for super-resolution microscopy. The method utilizes a chemiluminescent reaction involving a ruthenium complex electrochemically generated at an electrode.sup.8, which ensures minimal background signal. This allows us to directly capture single photons of the electrochemiluminescence of individual reactions, and to develop super-resolved electrochemiluminescence microscopy for imaging the adhesion dynamics of live cells with high spatiotemporal resolution. We anticipate that our method will advance the fundamental understanding of electrochemical reactions and prove useful for bioassays and cell-imaging applications. Optical imaging of single-molecule electrochemical reactions in aqueous solution enables super-resolution electrochemiluminescence microscopy, which can be used to monitor the adhesion dynamics of live cells with high spatiotemporal resolution.

Mo[S.sub.2] nanopores have already demonstrated better water-transport behaviour than graphene (13,14) owing to the enriched hydrophilic surface sites (provided by the molybdenum) that are produced following either irradiation with transmission [...], Making use of the osmotic pressure difference between fresh water and seawater is an attractive, renewable and clean way to generate power and is known as 'blue energy' (1-3). Another electrokinetic phenomenon, called the streaming potential, occurs when an electrolyte is driven through narrow pores either by a pressure gradient (4) or by an osmotic potential resulting from a salt concentration gradient (5). For this task, membranes made of two-dimensional materials are expected to be the most efficient, because water transport through a membrane scales inversely with membrane thickness (5-7). Here we demonstrate the use of single-layer molybdenum disulfide (Mo[S.sub.2]) nanopores as osmotic nanopower generators. We observe a large, osmotically induced current produced from a salt gradient with an estimated power density of up to [10.sup.6] watts per square metre--a current that can be attributed mainly to the atomically thin membrane of Mo[S.sub.2]. Low power requirements for nanoelectronic and optoelectric devices can be provided by a neighbouring nanogenerator that harvests energy from the local environment (8-11)--for example, a piezoelectric zinc oxide nanowire array (8) or single-layer Mo[S.sub.2] (ref. 12). We use our Mo[S.sub.2] nanopore generator to power a Mo[S.sub.2] transistor, thus demonstrating a self-powered nanosystem.

Comprehensive Summary: Super‐resolution microscopy (SRM) is a powerful imaging technique that overcomes the diffraction limit and allows imaging of the object structure in the nanoscale. However, SRM suffers from a tradeoff between spatial and temporal resolution, which prevents further exploration in scientific discoveries. In this review, we mainly focus on the development of improving spatiotemporal resolution of SRM, including 1) SRM based on physical and computational principles, 2) physical and computational factors affecting SRM, from which we conclude some strategies for developing new types of SRM, 3) the summary of the various types of SRM based on physical and computational principles, as well as, the analysis of the ordinary and developing SRM. Both SRMs based on physical principles and computational principles can be realized with spatial isolation and temporal isolation methods. We expect this review will offer some new ideas to improve the spatial and temporal resolution simultaneously, which may lead to more new discoveries in biology, chemistry, and materials science. [ABSTRACT FROM AUTHOR]

The sequencing of single protein molecules using nanopores is faced with a huge challenge due to the lack of resolution needed to resolve single amino acids. Here we report the direct experimental identification of single amino acids in nanopores. With atomically engineered regions of sensitivity comparable to the size of single amino acids, MoS2 nanopores provide a sub-1 Dalton resolution for discriminating the chemical group difference of single amino acids, including recognizing the amino acid isomers. This ultra-confined nanopore system is further used to detect the phosphorylation of individual amino acids, demonstrating its capability for reading post-translational modifications. Our study suggests that a sub-nanometer engineered pore has the potential to be applied in future chemical recognition and de novo protein sequencing at the single-molecule level. Protein sequencing is one of the key aims of the nanopore field. Working toward this goal, here the authors report the direct identification of single amino acids in MoS2 nanopores with sub-1 Dalton resolution, as well as the discrimination of the amino acid isomers and amino acid phosphorylation. [ABSTRACT FROM AUTHOR]

Probing proton transport is of vital importance for understanding cellular transport, surface catalysis and fuel cells. Conventional proton transport measurements rely on the use of electrochemical conductivity and do not allow for the direct visualization of proton transport pathways. The development of novel experimental techniques to spatiotemporally resolve proton transport is in high demand. Here, building upon the general conversion of aqueous proton flux into spatially resolved fluorescence signals, we optically visualize proton transport through nanopores and along hydrophilic interfaces. We observed that the fluorescence intensity increased at negative voltage due to lateral transport. Thanks to the temporal resolution of optical imaging, our technique further empowers the analysis of proton transport dynamics. [ABSTRACT FROM AUTHOR]