An emitter in the vicinity of a metal nanostructure is quenched by its decay through non-radiative channels, leading to the belief in a zone of inactivity for emitters placed within <10nm of a plasmonic nanostructure. Here we demonstrate that in tightly-coupled plasmonic resonators forming nanocavities "quenching is quenched" due to plasmon mixing. Unlike isolated nanoparticles, plasmonic nanocavities show mode hybridization which massively enhances emitter excitation and decay via radiative channels. This creates ideal conditions for realizing single-molecule strong-coupling with plasmons, evident in dynamic Rabi-oscillations and experimentally confirmed by laterally dependent emitter placement through DNA-origami.The lifetime of an excited atomic state is determined by the inherent properties of the atom and its environment, first theoretically suggested by Purcell [1] followed by experimental demonstration [2]. Subsequent experiments further verified this by placing atomic emitters within various optical-field-enhancing geometries [3][4][5]. Plasmonic structures have the ability to massively enhance electromagnetic fields, and therefore dramatically alter the excitation rate of an emitter [6]. However, it is well known that placing an emitter close to a plasmonic structure (< 10nm), quenches its fluorescence [7][8][9]. Analysis by Anger et al. [6] showed this is due to the coupling of the emitter to non-radiative higher-order plasmonic modes that dissipate its energy. This 'zone of inactivity' was previously believed to quench all quantum emitters. However, recent advancements have shown that an emitter's emission rate can be enhanced with plasmonic nano-antennas [10][11][12][13][14][15][16][17].Generally a single emitter placed into near-contact with an optical antenna gives larger fluorescence since the antenna efficiently converts far-field radiation into a localized field and vice versa [10,12,13,18]. This was recently demonstrated by Hoang et al. [17] who showed that a quantum dot in a 12nm nano-gap exhibits ultrafast spontaneous emission. What however remains unclear is if this enhanced emission is strong enough to allow for single emitter strong coupling.In this Letter, we demonstrate and explain why quenching is substantially suppressed in plasmonic nanocavities, to such a degree that facilitates lightmatter strong-coupling of single-molecules, even at roomtemperature, as we recently demonstrated experimentally [19]. This is due to: (i) the dramatic increase in the emitter excitation (similar to plasmonic antennas), and (ii) the changed nature of higher-order modes that acquire a radiative component, and therefore increase the quantum yield of the emitter. Modes in plasmonic nanocavities are not a simple superposition of modes from the isolated structures, but instead are hybridplasmonic states [20][21][22][23][24]. Hence, higher-order modes that are dark for an isolated spherical nanoparticle, radiate efficiently for tightly-coupled plasmonic structures [25], significantly reducing the non-radiative...

By systematically studying the proton selectivity of free-standing graphene membranes in aqueous solutions we demonstrate that protons are transported by passing through defects. We study the current-voltage characteristics of single-layer graphene grown by chemical vapour deposition (CVD) when a concentration gradient of HCl exists across it. Our measurements can unambiguously determine that H + ions are responsible for the selective part of the ionic current. By comparing the observed reversal potentials with positive and negative controls we demonstrate that the as-grown graphene is only weakly selective for protons. We use atomic layer deposition to block most of the defects in our CVD graphene. Our results show that a reduction in defect size decreases the ionic current but increases proton selectivity.

Nanomachines capable of controlled programmable work at the nanoscale promise to revolutionize a vast range of research and eventually should impact on daily lives. Due to the ease of design and modification, DNA origami is emerging as a natural platform to build such machines. However, one essential challenge is the controlled and rapid actuation of DNA origami using an external biocompatible stimulus. Here, actuation based on temperature‐induced phase transitions of the thermo‐responsive polymer poly(N‐isopropylacrylamide) (PNIPAM) is reported. By incorporating this polymer into DNA origami structures on either side of a flexible region, a “DNA origami flexor” is created that uses the tunable PNIPAM hydrophobicity to reversibly open and close the DNA structures. Such a mechanism has the advantage of being versatile and biocompatible, and possessing strong response to temperature changes of a few degrees Kelvin.

We fabricate hetero-component 'dimers' built from a single 40 nm gold and a single 40 nm silver nanoparticle separated by sub-5 nm gaps. Successful assembly mediated by a specialized DNA origami platform is verified by scanning electron microscopy and energy-dispersive X-ray characterization. Dark-field optical scattering on individual dimers is consistent with computational simulations. Direct plasmonic coupling between each nanoparticle is observed in both experiment and theory only for these small gap sizes, as it requires the silver dipolar mode energy to drop below the energy of the gold interband transitions. A new interparticle-spacing-dependent coupling model for heterodimers is thus required. Such Janus-like nanoparticle constructs available from DNA-mediated assembly provide an effective tool for controlling symmetry breaking in collective plasmon modes.

Nonlinear field dependence of electrophoresis in high fields has been investigated theoretically, yet experimental studies have failed to reach consensus on the effect. In this work, we present a systematic study on the nonlinear electrophoresis of highly charged submicron particles in applied electric fields of up to several kV/cm. First, the particles are characterized in the low-field regime at different salt concentrations and the surface charge density is estimated. Subsequently, we use microfluidic channels and video tracking to systematically characterize the nonlinear response over a range of field strengths. Using velocity measurements on the single particle level, we prove that nonlinear effects are present at electric fields and surface charge densities that are accessible in practical conditions. Finally, we show that nonlinear behavior leads to unexpected particle trapping in channels. :1907.04278v1 [cond-mat.soft] arXiv

The translocation of double-stranded DNA through a solid-state nanopore may either decrease or increase the ionic current depending on the ionic concentration of the surrounding solution. Below a certain crossover ionic concentration, the current change inverts from a current blockade to current enhancement. In this paper, we show that the crossover concentration for bundled DNA nanostructures composed of multiple connected DNA double-helices is lower than that of double-stranded DNA.Our measurements suggest that counterion mobility in the vicinity of DNA is reduced depending on the three-dimensional structure of the molecule. We further demonstrate that introducing neutral polymers such as polyethylene glycol into the measurement solution reduces electroosmotic outflow from the nanopore, allowing translocation of large DNA structures at low salt concentrations. Our experiments contribute to an improved understanding of ion transport in confined DNA environments, which is critical for the development of nanopore sensing techniques as well as synthetic membrane channels. Our salt-dependent measurements of model DNA nanostructures will guide the development of computational models of DNA translocation through nanopores.

and readout speed, [11][12][13][14] but it is almost helpless for DNA nanostructure-based storage. Even if the sequence is decoded, it is still difficult to reproduce the whole structure accurately, which indicates the higher security of this storage method from this perspective. Additionally, hardware encryption with physical keys can further improve the security of the information saved by this strategy. [10,15] Solid-state nanopore provides us with a versatile tool to investigate the biomole cules, such as DNA, ribonucleic acid (RNA), and proteins, at the singlemolecule level. [16,17] We recently introduced a solid-state nanopore sensing platform to read bits encoded by 56 DNA hairpins on a 7.2 kb DNA carrier. [18] Readout of the structures required glass nanopores with diameters of around 5 nm. Such a small diameter complicates the fabrication process and reduces the success rates compared to easily manufactured >10 nm glass nanopores. The smaller diameter also leads to more non-specific interaction and pore clogging. [19] In further work, we used a streptavidin-labelled DNA scaffold to build a secure data storage method with binary codes. [15] While protein labels can be used with larger diameter pores, they complicate the molecular assembly and set an upper bound on the data density through their defined size. Additionally, the number of usable protein labels is limited due to the high monovalent salt concentrations required for the readout. The presence of proteins also reduces the lifetime of solid-state nanopores and hence has a detrimental effect on the viability of the readout.In this work, we replace protein barcodes with multi-way DNA junctions to address the shortcoming and limitations of our prior approaches. Inspired by the work of Wang and Seaman [20] we designed a multi-level storage architecture. Building on our established DNA carrier-based rewritable storage system with 14 nm diameter nanopores, [19] we use three DNA junction structures of different sizes (4-way junction, 6-way junction, and 12-way junction) to generate a quaternary encoding system (0-3) on the long linear DNA carrier, which increases the data density compared to classic binary encoding. Through toehold-mediated strand displacement reaction (SDR), [21][22][23] the presence of nanostructures on the carrier can be precisely controlled, allowing data reading and writing. Based on this storage system, we successfully save a grayscale image into the DNA nanostructures on 16 different carriers and read out the information in the mixture. Furthermore, using SDR the image information can be easily encrypted and decrypted.Deoxyribonucleic acid (DNA) nanostructure-based data encoding is an emerging information storage mode, offering rewritable, editable, and secure data storage. Herein, a DNA nanostructure-based storage method established on a solid-state nanopore sensing platform to save and encrypt a 2D grayscale image is proposed. DNA multi-way junctions of different sizes are attached to a double strand of DNA carriers, resulting i...

A method is established to reliably suspend graphene monolayers across glass nanopores as a simple, low cost platform to study ionic transport through graphene membranes. We systematically show that the graphene seals glass nanopore openings with areas ranging from 180 nm2 to 20 μm2, allowing detailed measurements of ionic current and transport through graphene. In combination with in situ Raman spectroscopy, we characterise the defects formed in ozone treated graphene, confirming an increase in ionic current flow with defect density. This highlights the potential of our method for studying single molecule sensing and filtration.