This study provides an overview of established processes as well as recent progress in emerging technologies for advanced oxidation processes (AOPs). In addition to a discussion of major reaction ...mechanisms and formation of by-products, data on energy efficiency were collected in an extensive analysis of studies reported in the peer-reviewed literature enabling a critical comparison of various established and emerging AOPs based on electrical energy per order (EEO) values. Despite strong variations within reviewed EEO values, significant differences could be observed between three groups of AOPs: (1) O3 (often considered as AOP-like process), O3/H2O2, O3/UV, UV/H2O2, UV/persulfate, UV/chlorine, and electron beam represent median EEO values of <1 kWh/m3, while median energy consumption by (2) photo-Fenton, plasma, and electrolytic AOPs were significantly higher (EEO values in the range of 1–100 kWh/m3). (3) UV-based photocatalysis, ultrasound, and microwave-based AOPs are characterized by median values of >100 kWh/m3 and were therefore considered as not (yet) energy efficient AOPs. Specific evaluation of 147 data points for the UV/H2O2 process revealed strong effects of operational conditions on reported EEO values. Besides water type and quality, a major influence was observed for process capacity (lab-vs. pilot-vs. full-scale applications) and, in case of UV-based processes, of the lamp type. However, due to the contribution of other factors, correlation of EEO values with specific water quality parameters such as UV absorbance and dissolved organic carbon were not substantial. Also, correlations between EEO and compound reactivity with OH-radicals were not significant (photolytically active compounds were not considered). Based on these findings, recommendations regarding the use of the EEO concept, including the upscaling of laboratory results, were derived.
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•Short summary of radical generation mechanisms and application of AOPs.•First comparison of published EEO values across different AOPs.•Critical consideration of influencing factors on reported EEO values within UV/H2O2.•Proposal for proper use of the EEO-concept.•Discussion of major oxidation by-product formation mechanisms.
Conventional water disinfection methods such as chlorination typically involve the generation of harmful disinfection byproducts and intensive chemical consumption. Emerging electroporation ...disinfection techniques using nanowire-enhanced local electric fields inactivate microbes by damaging their outer structures without byproduct formation or chemical dosing. However, this physical-based method suffers from a limited inactivation efficiency under high water flux due to an insufficient contact time. Herein, we integrate electrochlorination with nanowire-enhanced electroporation to achieve a synergistic flow-through process for efficient water disinfection targeting bacteria and viruses. Electroporation at the cathode induces sub-lethal damages on the microbial outer structures. Subsequently, electrogenerated active chlorine at the anode aggravates these electroporation-induced injuries to the level of lethal damage. This sequential flow-through disinfection system achieves complete disinfection (>6.0-log) under a very high water flux of 2.4 × 104 L/(m2 h) with an applied voltage of 2.0 V. This disinfection efficiency is 8 times faster than that of electroporation alone. Further, the specific energy consumption for the disinfection by this novel process is extremely low (8 × 10–4 kW h/m3). Our results demonstrate a promising method for rapid and energy-efficient water disinfection by coupling electroporation with electrochlorination to meet vital needs for pathogen elimination.
Black body materials are promising candidates to meet future energy demands, as they are able to harvest energy from the total bandwidth of solar radiation. Here, we report on high-absorption ...near-blackbody-like structures (>98% for a wide solar spectrum range from 220 to 2500 nm) consisting of a silica scaffold and Ag nanoparticles with a layer thickness below 10 μm, fabricated using metastable atomic layer deposition (MS-ALD). Several effects contribute collectively and in a synergistic manner to the ultrahigh absorption, including the pronounced heterogeneity of the nanoparticles in size and shape, particle plasmon hybridization, and the trapping of omnidirectionally scattered light in the 3D hierarchical hybrid structures. We propose that, in the future, MS-ALD needs to be considered as a simple and promising method to fabricate blackbody materials with excellent broadband absorption.
The discharge of wastewater effluents to a stream that is subsequently used for drinking water abstraction has been previously referred to as de facto water reuse. Where the abstraction of surface ...water for drinking water production occurs via induced bank filtration or aquifer recharge, additional site-specific factors should be considered to assess the impact of wastewater effluents on bank-filtered water. This study represents the first national reconnaissance to quantify wastewater effluent contributions in streams across Germany and consequences for indirect drinking water abstraction from these streams. An automated assessment using ArcGIS was conducted for river basins considering minimum and mean average discharge conditions of streams as well as discharge from more than 7500 wastewater facilities. In urban areas, where the natural base discharge is low, wastewater effluent contributions greater than 30–50% were determined under mean minimum discharge conditions, which commonly prevail from May to September. A conceptual model was proposed to estimate critical bank filtrate shares resulting in exceedances of monitoring trigger levels for health-relevant chemicals as a universal qualitative assessment regarding the relevance of de facto reuse conditions in surface waters used for drinking water abstraction. This approach was validated using chemical monitoring data for three case study locations.
3D single molecule localization microscopy (SMLM) is an emerging superresolution method for structural cell biology, as it allows probing precise positions of proteins in cellular structures. In ...supercritical angle localization microscopy (SALM), z-positions of single fluorophores are extracted from the intensity of supercritical angle fluorescence, which strongly depends on their distance to the coverslip. Here, we realize the full potential of SALM and improve its z-resolution by more than four-fold compared to the state-of-the-art by directly splitting supercritical and undercritical emission, using an ultra-high NA objective, and applying fitting routines to extract precise intensities of single emitters. We demonstrate nanometer isotropic localization precision on DNA origami structures, and on clathrin coated vesicles and microtubules in cells, illustrating the potential of SALM for cell biology.
Rapid and effective methods of pathogen identifications are of major interest in clinical microbiological analysis to administer timely tailored antibiotic therapy. Raman spectroscopy as a ...label-free, culture-independent optical method is suitable to identify even single bacteria. However, the low bacteria concentration in body fluids makes it difficult to detect their characteristic molecular fingerprint directly in suspension. Therefore, in this study, Raman spectroscopy is combined with dielectrophoresis, which enables the direct translational manipulation of bacteria in suspensions with spatial nonuniform electrical fields so as to perform specific Raman spectroscopic characterization. A quadrupole electrode design is used to capture bacteria directly from fluids in well-defined microsized regions. With live/dead fluorescence viability staining, it is verified, that the bacteria survive this procedure for the relevant range of field strengths. The dielectrophoretic enrichment of bacteria allows for obtaining high quality Raman spectra in dilute suspensions with an integration time of only one second. As proof-of-principle study, the setup was tested with Escherichia coli and Enterococcus faecalis, two bacterial strains that are commonly encountered in urinary tract infections. Furthermore, to verify the potential for dealing with real world samples, pathogens from patients’ urine have been analyzed. With the additional help of multivariate statistical analysis, a robust classification model could be built and allowed the classification of those two strains within a few minutes. In contrast, the standard microbiological diagnostics are based on very time-consuming cultivation tests. This setup holds the potential to reduce the crucial parameter diagnosis time by orders of magnitude.
Surface-enhanced Raman spectroscopy (SERS) enables sensitive chemical studies and materials identification, relying on electromagnetic (EM) and chemical-enhancement mechanisms. Here we introduce a ...tool for the correlative nanoimaging of EM and SERS hotspots, areas of strongly enhanced EM fields and Raman scattering, respectively. To that end, we implemented a grating spectrometer into a scattering-type scanning near-field optical microscope (s-SNOM) for mapping of both the elastically and inelastically (Raman) scattered light from the near-field probe, that is, a sharp silicon tip. With plasmon-resonant gold dimers (canonical SERS substrates) we demonstrate with nanoscale spatial resolution that the enhanced Raman scattering from the tip is strongly correlated with its enhanced elastic scattering, the latter providing access to the EM-field enhancement at the illumination frequency. Our technique has wide application potential in the correlative nanoimaging of local-field enhancement and SERS efficiency as well as in the investigation and quality control of novel SERS substrates.
CaF2 seems to be the ideal substrate material for the infrared spectroscopy of organic and biological layers, since its refractive index is very similar to that of these materials. As a consequence ...of this similarity, the baseline, i.e., the signal strength in nonabsorbing regions, is nearly flat and does not show notable interference fringes. Nevertheless, as absorption is always accompanied by changes of the refractive index, the refractive indices of substrate and layer can substantially deviate around absorption bands. As a consequence, changes in band intensity, shape, and position result, which aggravate a correct interpretation of the spectra. For layers with thicknesses between 1 and 2 μm, we show experimentally, that deviations from the Beer–Lambert law of up to ±10% occur. Calculations reveal that for thinner layers these deviations are even higher. These results suggest the application of a wave-optics based formalism to correct the deviations. We introduce such a formalism and prove that it is able to remove the errors. In addition, it also corrects band shape and position changes.
The key issue for the implementation of a metamaterial is to demonstrate the existence of collective modes corresponding to coherent oscillations of the meta-atoms. Atoms of natural materials ...interact with electromagnetic fields as quantum two-level systems. Artificial quantum two-level systems can be made, for example, using superconducting nonlinear resonators cooled down to their ground state. Here we perform an experiment in which 20 of these quantum meta-atoms, so-called flux qubits, are embedded into a microwave resonator. We observe the dispersive shift of the resonator frequency imposed by the qubit metamaterial and the collective resonant coupling of eight qubits. The realized prototype represents a mesoscopic limit of naturally occurring spin ensembles and as such we demonstrate the AC-Zeeman shift of a resonant qubit ensemble. The studied system constitutes the implementation of a basic quantum metamaterial in the sense that many artificial atoms are coupled collectively to the quantized mode of a photon field.
We report on recent experimental results deploying a continuous cryogenic hydrogen jet as a debris-free, renewable laser-driven source of pure proton beams generated at the 150 TW ultrashort pulse ...laser Draco. Efficient proton acceleration reaching cut-off energies of up to 20 MeV with particle numbers exceeding 10
particles per MeV per steradian is demonstrated, showing for the first time that the acceleration performance is comparable to solid foil targets with thicknesses in the micrometer range. Two different target geometries are presented and their proton beam deliverance characterized: cylindrical (∅ 5 μm) and planar (20 μm × 2 μm). In both cases typical Target Normal Sheath Acceleration emission patterns with exponential proton energy spectra are detected. Significantly higher proton numbers in laser-forward direction are observed when deploying the planar jet as compared to the cylindrical jet case. This is confirmed by two-dimensional Particle-in-Cell (2D3V PIC) simulations, which demonstrate that the planar jet proves favorable as its geometry leads to more optimized acceleration conditions.
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