Nanopores that approach molecular dimensions demonstrate exotic transport behaviour and are theoretically predicted to display discontinuities in the diameter dependence of interior ion transport because of structuring of the internal fluid. No experimental study has been able to probe this diameter dependence in the 0.5-2 nm diameter regime. Here we observe a surprising fivefold enhancement of stochastic ion transport rates for single-walled carbon nanotube centered at a diameter of approximately 1.6 nm. An electrochemical transport model informed from literature simulations is used to understand the phenomenon. We also observe rates that scale with cation type as Li þ 4K þ 4Cs þ 4Na þ and pore blocking extent as K þ 4Cs þ 4Na þ 4Li þ potentially reflecting changes in hydration shell size. Across several ion types, the pore-blocking current and inverse dwell time are shown to scale linearly at low electric field. This work opens up new avenues in the study of transport effects at the nanoscale.

Planar two-dimensional (2D) materials are possibly the ideal channel candidates for future field effect transistors (FETs), due to their unique electronic properties. However, the performance of FETs based on 2D materials is yet to exceed those of conventional silicon based devices. Here we present a 2D channel thin film made from liquid phase exfoliated molybdenum oxide nanoflake inks with highly controllable sub-stoichiometric levels. The ability to induce oxygen vacancies by solar light irradiation in an aqueous environment allows the tuning of electronic properties in 2D sub-stoichiometric molybdenum oxides (MoO 3-x ). The highest mobility is found to be ~ 600 cm 2 V −1 s −1 with an estimated free electron concentration of ~ 1.610 21 cm -3 and an optimal I On /I Off ratio of >10 5 for the FETs made of 2D flakes irradiated for 30 min (x = 0.042). These values are significant and represent a real opportunity to realize the next generation of tunable electronic devices using electronic inks.

Alkanethiol (RSH) monolayers are by far the most extensively studied surface self-assembly systems due to their robustness and the opportunity to control their assembly in the dimension perpendicular to the surface. Thioethers (RSR′), a similar class of molecule, remain largely unstudied to date but may offer a similar level of assembly control parallel to the surface. Here we report the self-assembly of dibutyl sulfide, a symmetric thioether species, on a Au{111} surface using scanning tunneling microscopy. As with thiols, dibutyl sulfide forms well-ordered monolayers, but due to the slightly weaker molecule-metal bond, the coverage and temperature-dependent behavior is very different than that of alkanethiols. Adsorption is sensitive to the different regions of the Au{111} herringbone reconstruction. Dibutyl sulfide lies parallel to the surface and forms well-ordered chains in domains that preferentially bind first in fcc regions, then hcp, and finally on soliton walls. The sulfide-Au interaction is strong enough to disrupt the native herringbone reconstruction of Au; however, unlike thiols, dibutyl sulfide adsorption does not result in etch pit formation. A monolayer of dibutyl sulfide has a very low defect density as compared to thiol-SAM based systems. This low defect density hints at the possibility of using a thioether moiety as a basis for a self-assembled system free of typical defects like etch pits, which allow attack and degradation of the monolayer. Upon annealing the surface with a high molecular coverage to 575 K, dibutyl sulfide desorbs molecularly from the less energetically favorable regions of the surface first. At this reduced coverage the system returns to an intermediate-coverage structure, thereby demonstrating the reversibility of the assembly. Elevating the temperature further causes the entire monolayer to desorb, and the original herringbone structure of Au returns. We postulate that this reversibility, coupled with the high rate of concerted rearrangements, allows this system to reach a very high level of order.

It is widely recognized that an array of addressable sensors can be multiplexed for the label-free detection of a library of analytes. However, such arrays have useful properties that emerge from the ensemble, even when monofunctionalized. As examples, we show that an array of nanosensors can estimate the mean and variance of the observed dissociation constant (KD), using three different examples of binding IgG with Protein A as the recognition site, including polyclonal human IgG (KD μ = 19 μM, σ(2) = 1000 mM(2)), murine IgG (KD μ = 4.3 nM, σ(2) = 3 μM(2)), and human IgG from CHO cells (KD μ = 2.5 nM, σ(2) = 0.01 μM(2)). Second, we show that an array of nanosensors can uniquely monitor weakly affined analyte interactions via the increased number of observed interactions. One application involves monitoring the metabolically induced hypermannosylation of human IgG from CHO using PSA-lectin conjugated sensor arrays where temporal glycosylation patterns are measured and compared. Finally, the array of sensors can also spatially map the local production of an analyte from cellular biosynthesis. As an example, we rank productivity of IgG-producing HEK colonies cultured directly on the array of nanosensors itself.

The microscopic details of how metals alloy have important consequences for both their material properties and their chemical reactivity. In this study, the initial stages of alloying of Pd and Ag with Cu(111) are compared. Low-temperature scanning tunneling microscopy reveals that physical vapor deposition of Pd and Ag at or above room temperature yields remarkably different surface alloys: Pd predominantly incorporates at the nearest ascending Cu step edge, whereas Ag appears to be able to traverse step edges rather easily and alloys into terraces both above and below its initial adsorption site. Density functional theory calculations reveal that even though Pd adatoms have a lower barrier than Ag for traversing step edges, unlike Ag they bind very strongly to ascending step edges and remain there permanently. This leads to a situation in which Pd atoms have at most a very small number of attempts to leave the terrace on which they are deposited before they are incorporated into the nearest ascending step edge. Ag adatoms, however, have many opportunities to cross step edges and can alloy at positions far from their initial starting point. This direct comparison demonstrates the importance in combining theory and experiment in order to understand complicated surface alloying mechanisms and illustrates how both the kinetics and the thermodynamics of the process must be considered to fully understand experimental observations.