In this paper we present a mesoscopic model of the transport and electrochemical processes inside a Lithium-O 2 battery cathode pore. The model dynamically resolves both Oxygen Reduction Reaction (ORR) thin film and solution phase mechanisms together with the transport of O 2 , Li + and LiO 2 in the electrolyte. It is supported on an extension to three dimensions of our Kinetic Monte Carlo (KMC) Electrochemical Variable Step Size Method (E-VSSM) recently published by our group in [M. A. Quiroga and A. A. Franco, J. Electrochem. Soc., 162, E73 (2015)]. The model allows predicting porosity evolution as a function of multiple operational, physical and geometrical parameters including the pore size and inlet/outlet channel size, O 2 and Li + concentration, the property of the solvent as well as the applied overpotential. The investigation of the impact of these different aspects reveals that at the mesoscale level, the overall ORR kinetics and the discharge mechanism strongly depend on a balance between the geometrical features of the pore and the transport as well as the electrochemical properties of the system. The escalating demand for energy and the depletion of fossil fuel resources create an urge to find alternative methods to convert the available energy on Earth into useful energy. Because of their ecofriendly character, renewable energy devices undergo a tremendous development.1-3 However, the intermittent nature of renewable energy harvest as well as the hourly fluctuation of energy consumption highlight the importance of developing advanced energy storage systems.4,5 Lithium Ion Batteries (LIBs) have already dominated the market of electronics, but for other applications such as electric vehicles, their further enhancement in energy density is still requested.The Li-O 2 battery, especially the non-aqueous type, attracted much attention in the last decade due to its high theoretical specific energy density. In spite of tremendous efforts, the performance of nonaqueous Li-O 2 batteries in the state-of-art is still far from expectations in view of its unsatisfactory discharge capacity, high overpotential and severe parasitic reactions. All the above deficiencies are partially, if not all, due to the insulating and insoluble nature of Li 2 O 2 formed during discharge.Johnson et al. 6 reported a two-step discharge process with a dual mechanism as shown in the following reactions:where the subscript "sol" stands for solution phase, while the star sign stands for species that are adsorbed on the electrode surface .The first step is the reduction of O 2 with the existence of Li + to form LiO 2 ion pairs (Reaction 1). Then, the LiO 2 ion pairs can either move into the electrolyte and be disproportionated, generating Li 2 O 2 of toroidal shape and O 2 (Reaction 2a), or they can stay on the electrode surface and be reduced electrochemically, forming a passivation layer (Reaction 2b). The former path is the "solution phase mechanism" but the origin of the LiO 2 solubility, whether from the high donor number solvent ...

Nanophotonics offers a promising range of applications spanning from the development of efficient solar cells to quantum communications and biosensing. However, the ability to efficiently couple fluorescent emitters with nanostructured materials requires to probe light-matter interactions at subwavelength resolution, which remains experimentally challenging. Here, we introduce an approach to perform super-resolved fluorescence lifetime measurements on samples that are densely labelled with photo-activatable fluorescent molecules. The simultaneous measurement of the position and the decay rate of the molecules provides a direct access to the local density of states (LDOS) at the nanoscale. We experimentally demonstrate the performance of the technique by studying the LDOS variations induced in the near field of a silver nanowire, and we show via a Cramér-Rao analysis that the proposed experimental setup enables a single-molecule localisation precision of 6 nm.

Single-molecule localization microscopy is a powerful technique with vast potential to study lightmatter interactions at the nanoscale. Nanostructured environments can modify the fluorescence emission of single molecules and the induced decay-rate modification can be retrieved to map the local density of optical states (LDOS). However, the modification of the emitter's point spread function (PSF) can lead to its mislocalization, setting a major limitation to the reliability of this approach. In this paper, we address this by simultaneously mapping the position and decay rate of single-molecules and by sorting events by their decay rate and PSF size. With the help of numerical simulations, we are able to infer the dipole orientation and to retrieve the real position of mislocalized emitters. We have applied our approach of single-molecule fluorescence lifetime imaging microscopy (smFLIM) to study the LDOS modification of a silver nanowire over a field of view of ~10 µm 2 with a single-molecule localization precision of ~15 nm. This is possible thanks to the combined use of an EMCCD camera and an array of single-photon avalanche diodes, enabling multiplexed and super-resolved fluorescence lifetime imaging.

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We present a direct experimental investigation of the optical field distribution around a suspended tapered optical nanofiber by means of a fluorescent scanning probe. Using a 100 nm diameter fluorescent bead as a probe of the field intensity, we study interferences made by a nanofiber (400 nm diameter) scattering a plane wave (568 nm wavelength). Our scanning fluorescence near-field microscope maps the optical field over 36 µm 2 , with λ/5 resolution, from contact with the surface of the nanofiber to a few micrometers away. Comparison between experiments and Mie scattering theory allows us to precisely determine the emitter-nanofiber distance and experimental drifts.

The development of integrated photonic devices has led to important advancements in the field of light-matter interaction at the nanoscale. One of the main focal points is the coupling between single photon emitters and optical waveguides aiming to achieve efficient optical confinement and propagation. In this work, we focus on the characterization of a hybrid dielectric/plasmonic waveguide consisting of a gold triangular nanoantenna placed on top of a TiO2 waveguide. The strong directionality of the device is experimentally demonstrated by comparing the intensity scattered by the nanotriangle to the one scattered by a SNOM tip for different illumination geometries. The ability of the plasmonic antenna to generate powerful coupling between a single emitter and the waveguide will also be highlighted through numerical simulations.

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