Cycloaddition of CO2 to epoxides catalyzed by imidazolium-based polymeric ionic liquids

A series of cross-linked ionic polymers based on styrene-functionalized imidazolium salts with chloride, hexafluorophosphate, or tetrafluoroborate counter anions have been prepared and characterized using a range of analytical and spectroscopic techniques and electron microscopy. The polymer with the chloride anion is an efficient catalyst for the cycloaddition of carbon dioxide with epoxides to afford cyclic carbonates. The cross-linked polymer is insoluble in organic solvents and is highly stable and therefore can be easily recycled and reused.

UV-nanoimprint lithography and large area roll-to-roll texturization with hyperbranched polymer nanocomposites for light-trapping applications

Caroline Calderone, Philippe Couty, Diego Fischer, Marina Aymara González Lazo, Aïcha Hessler-Wyser, Yves Leterrier, Jan-Anders Månson, Rémy Teuscher

Light-trapping textures were produced in hyperbranched polymer (HBP) silica nanocomposites using a UV-nanoimprint lithography (UVNIL) replication method, either in batch or roll-to-roll processes. The hardness of the HBP was found to increase by a factor of 2.5 with the addition of 50 vol% of nanoparticles. A nickel master with random sub-micron pyramidal structures was used to imprint nanocomposites containing up to 20 vol% of silica on a polyethylene naphthalate (PEN) substrate. The influence of nanoparticle fraction and pressure on the texture morphology and light scattering properties of the replicas was studied using scanning electron microscopy and optical analysis. The roughness and coherence length of the textures were similar to those of the master for all investigated compositions and process pressures. Likewise, the light scattering performance of aluminum-coated texturized nanocomposites was identical to that of the metal template, with a haze of 90% over the 400–800 nm spectral range. Thin film amorphous silicon solar cells were deposited on the texturized substrates using a large-area roll-to-roll process. The photocurrent of these devices was found to be 23% higher than the reference value of a flat cell.

Elsevier2012

Integrated photonics enables continuous-beam electron phase modulation

Guanhao Huang, Tobias Kippenberg, Junqiu Liu, Jiahe Pan, Arslan Sajid Raja, Rui Ning Wang, Yujia Yang

Integrated photonics facilitates extensive control over fundamental light-matter interactions in manifold quantum systems including atoms(1), trapped ions(2,3), quantum dots(4) and defect centres(5). Ultrafast electron microscopy has recently made free-electron beams the subject of laser-based quantum manipulation and characterization(6-11), enabling the observation of free-electron quantum walks(12-14), attosecond electron pulses(10,15-17) and holographic electromagnetic imaging(18). Chip-based photonics(19,20) promises unique applications in nanoscale quantum control and sensing but remains to be realized in electron microscopy. Here we merge integrated photonics with electron microscopy, demonstrating coherent phase modulation of a continuous electron beam using a silicon nitride microresonator. The high-finesse (Q(0) approximate to 10(6)) cavity enhancement and a waveguide designed for phase matching lead to efficient electron-light scattering at extremely low, continuous-wave optical powers. Specifically, we fully deplete the initial electron state at a cavity-coupled power of only 5.35 microwatts and generate >500 electron energy sidebands for several milliwatts. Moreover, we probe unidirectional intracavity fields with microelectronvolt resolution in electron-energy-gain spectroscopy(21). The fibre-coupled photonic structures feature single-optical-mode electron-light interaction with full control over the input and output light. This approach establishes a versatile and highly efficient framework for enhanced electron beam control in the context of laser phase plates(22), beam modulators and continuous-wave attosecond pulse trains(23), resonantly enhanced spectroscopy(24-26) and dielectric laser acceleration(19,20,27). Our work introduces a universal platform for exploring free-electron quantum optics(28-31), with potential future developments in strong coupling, local quantum probing and electron-photon entanglement.

NATURE PORTFOLIO2021

A Mini-Atlas of diatom frustule electron microscopy images at different magnifications

Joris Pierre Everaerts, Chrysanthi Papadaki

Diatom algae are active and efficient photosynthesizing single cell organisms responsible for a quarter of biomass and a quarter of oxygen release on the Earth surface. Diatoms form an enormously diverse class of microorganisms possessing stiff and strong, durable exoskeletons made from hydrated amorphous silica forming neat 3D nanostructures, and displaying hierarchical organization up to the scale of tens of micrometres. In our ongoing research into the structure and properties of diatoms we observed their colonization patterns on various surfaces, including polymers (PE, PP, PC and PETF) and silicon. This process can be guided by purposeful surface patterning to introduce pits, grooves, and ledges. Guided colonization opens the prospect of assembly and harvesting diatom frustules for applications in micro- and nanoelectro-mechanical systems (MEMS and NEMS). Additionally, the wide range and specificity of diatoms opens the possibility of using them as tags and markers that are below the level of visibility by naked eye, but present specific spectroscopic fingerprints in visible light and UV ranges. Diatom `tags' can also be read using high magnification imaging using Scanning Electron Microscopy (SEM). As a contributory guidance to morphological diversity of diatoms we present a mini-atlas of diatom in the form of high resolution SEM images. (C) 2020 Elsevier Ltd. All rights reserved.

ELSEVIER2020

Integrated photonics enables continuous-beam electron phase modulation

Guanhao Huang, Tobias Kippenberg, Junqiu Liu, Jiahe Pan, Arslan Sajid Raja, Rui Ning Wang, Yujia Yang

NATURE PORTFOLIO2021