Plasma-liquid interactions: a review and roadmap

Plasma-liquid interactions represent a growing interdisciplinary area of research involving plasma science, fluid dynamics, heat and mass transfer, photolysis, multiphase chemistry and aerosol science. This review provides an assessment of the state-of-the-art of this multidisciplinary area and identifies the key research challenges. The developments in diagnostics, modeling and further extensions of cross section and reaction rate databases that are necessary to address these challenges are discussed. The review focusses on non-equilibrium plasmas

Synthesis and Reactivity of Triazaphenanthrenes

Pyridonaphthyridines (triazaphenanthrenes) were prepared in 4 steps and in 13–52% overall yield using Negishi cross-couplings between iodopicolines and 2-chloro-pyridylzinc derivatives. After chlorination, Gabriel amination and spontaneous ring-closure, the final aromatization leading to the triazaphenanthrenes was achieved with chloranil. This heterocyclic scaffold underwent a nucleophilic addition at position 6 leading to further functionalized pyridonaphthyridines. The influence of these chemical modifications on the optical properties was studied by steady-state and time-resolved optical spectroscopy. While the thiophene-substituted heterocycles exhibited the most extended absorption, the phenyl- and furan-substituted compounds showed a stronger photoluminescence, reaching above 20% quantum yield and lifetimes of several nanoseconds

Oligothiophene-Bridged Conjugated Covalent Organic Frameworks

Two-dimensional covalent organic frameworks (2D-COFs) are crystalline, porous materials comprising aligned columns of π-stacked building blocks. With a view toward the application of these materials in organic electronics and optoelectronics, the construction of oligothiophene-based COFs would be highly desirable. The realization of such materials, however, has remained a challenge, in particular with respect to laterally conjugated imine-linked COFs. We have developed a new building block design employing an asymmetric modification on an otherwise symmetric backbone that allows us to construct a series of highly crystalline quaterthiophene-derived COFs with tunable electronic properties. Studying the optical response of these materials, we have observed for the first time the formation of a charge transfer state between the COF subunits across the imine bond. We believe that our new building block design provides a general strategy for the construction of well-ordered COFs from various extended building blocks, thus greatly expanding the range of applicable molecules

Antiseptic treatment of <i>Pseudomonas aeruginosa</i> SG81 biofilms.

<p>The analytical results by the Number of samples (n), Colony reduction factor (CRF) in log₁₀ (CFU/cm²) ± Standard Deviation (SD), lower and upper 95% confidence limits (CI) after exposure to air plasma for 30–600 s treatment time respectively and 0.1% CHX after 600 s exposure time and untreated control of <i>Pseudomonas aeruginosa</i> SG81 biofilms [p-values of omnibus tests (Kruskal-Wallis) and two-sample tests (Whitney <i>U</i>); statistical significance: α = 0.05].</p>c<p>significantly different from CHX.</p>*<p>significantly different from the respective treatment time of <i>Staphylococcus epidermidis</i> RP62A.</p

Experimental setup of the SBD-B plasma source.

<p>A: Overview of the experimental setup. B: Near focus of the electrode in action mode above the discs with biofilms. C: Schematic representation of the experimental setup of SBD-B in cross section.</p

Spectrometric graph of irradiance by SBD-B generated air plasma within 300 s of exposure time between 200 and 400 nm.

<p>Spectrometric graph of irradiance by SBD-B generated air plasma within 300 s of exposure time between 200 and 400 nm.</p

Experimental setup of the SBD-A plasma source.

<p>A: Electrode and discs with biofilms on plastic flat grate. B: Configuration of the electrode in action mode. C: Schematic representation of the experimental setup of SBD-A.</p

Scanning electron micrographs of untreated and air plasma treated biofilms on polycarbonate discs.

<p>A) untreated biofilm of <i>Pseudomonas aeruginosa</i> SG81 (5000-fold), B) untreated biofilm of <i>Staphylococcus epidermidis</i> RP62A (5000-fold), C) <i>Pseudomonas aeruginosa</i> SG81 biofilms after 300 s of air plasma treatment by SBD-A (2000-fold) and D) by SBD-B (1500-fold) as well as E) <i>Staphylococcus epidermidis</i> RP62A biofilms after 300 s of air plasma treatment by SBD-A (1000-fold) and F) by SBD-B (5000-fold).</p

Cytotoxicity of 0.1% chlorhexidine digluconate solution on L929 cell line (mouse fibroblasts).

<p>Measured values of MTT-Assay after 30–600 s treatment time with 0.1% of chlorhexidine dicluconate solution (in culture media) with the Number of samples (n), mean, standard deviation (SD), and the cell viability as ratio in comparison to the control in percent.</p

Synchronized Offset Stacking: A Concept for Growing Large-Domain and Highly Crystalline 2D Covalent Organic Frameworks

Covalent organic frameworks (COFs), formed by reversible condensation of rigid organic building blocks, are crystalline and porous materials of great potential for catalysis and organic electronics. Particularly with a view of organic electronics, achieving a maximum degree of crystallinity and large domain sizes while allowing for a tightly π-stacked topology would be highly desirable. We present a design concept that uses the 3D geometry of the building blocks to generate a lattice of uniquely defined docking sites for the attachment of consecutive layers, thus allowing us to achieve a greatly improved degree of order within a given average number of attachment and detachment cycles during COF growth. Synchronization of the molecular geometry across several hundred nanometers promotes the growth of highly crystalline frameworks with unprecedented domain sizes. Spectroscopic data indicate considerable delocalization of excitations along the π-stacked columns and the feasibility of donor–acceptor excitations across the imine bonds. The frameworks developed in this study can serve as a blueprint for the design of a broad range of tailor-made 2D COFs with extended π-conjugated building blocks for applications in photocatalysis and optoelectronics