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External magnetic fields affect various electrochemical processes and can be used to enhance the efficiency of the electrochemical water splitting reaction. However, the driving forces behind this effect are poorly understood due to the analytical challenges of the available interface-sensitive techniques. Here, we present a set-up based on magneto- and electro-optical probing, which allows to juxtapose the magnetic properties of the electrode with the electrochemical current densities in situ at various applied potentials and magnetic fields. On the example of an archetypal hydrogen evolution catalyst, Pt (in a form of Co/Pt superlattice), we provide evidence that a magnetic field acts on the electrochemical double layer affecting the local concentration gradient of hydroxide ions, which simultaneously affects the magneto-optical and magnetocurrent response.

This paper summarizes a project seminar in analytical chemistry that includes a method comparison approach and collaborative learning. In this project seminar, 12 students worked in four groups, ea...

Analytical and Bioanalytical Chemistry, 414 (11), ISSN:1618-2650, ISSN:1618-2642

Transformation studies of chlorinated paraffins (CPs) and the effects of CP transformation products on humans, biota and environment are rare. The focus here is on hydroxylation reactions. As for polyhalogenated persistent organic pollutants (POPs) in general, hydroxylation reactions convert lipophilic material to more polar compounds with increased mobility. We investigated the in-vitro transformation of single-chain CP-mixtures to hydroxylated products with the dehalogenase LinB from Sphingobium indicum. C11-, C12- and C13-single-chain CP-homologues were exposed to LinB and mono-hydroxylated (CP-ols) and di-hydroxylated (CP-diols) transformation products were formed. Liquid-chromatography coupled to mass-spectrometry (LC-MS) was used to detect hydroxylated products and separate them from the starting material. The presented data can be used to identify these CP-ol and CP-diol homologues in other samples. Hydroxylated products had lower chlorination degrees (nCl) than respective CP-starting-materials. Reactive and persistent CP-material was found in each homologue group. Reactive material is converted within hours by LinB, while more persistent CPs are transformed within days. Homologue-specific kinetic models were established to simulate the stepwise hydroxylation of persistent CPs to mono- and di-hydroxylated products. First-order rate constants for the formation of CP-ols (k1) and CP-diols (k2) were deduced for different homologues. Lower-chlorinated CP-ols did not accumulate to large extent and were transformed quickly to CP-diols, while higher-chlorinated CP-ols and -diols both accumulated. By enzymatic transformation of single-chain CPs with LinB, we synthesized unique sets of mono- and di-hydroxylated materials, which can be used as analytical standards and as starting materials for metabolic, toxicity and environmental fate studies.

Technical chlorinated paraffins (CPs) are produced via radical chlorination of n-alkane feedstocks with different carbon chain-lengths (∼C10–C30). Short-chain CPs (SCCPs, C10–C13) are classified as persistent organic pollutants (POPs) under the Stockholm Convention. This regulation has induced a shift to use longer-chain CPs as substitutes. Consequently, medium-chain (MCCPs, C14–C17) and long-chain (LCCPs, C > 17) CPs have become dominant homologues in recent environmental samples. However, no suitable LCCP-standard materials are available. Herein, we report on the chemical synthesis of single-chain C18-CP materials, starting with pure n-alkane and sulfuryl chloride (SO2Cl2). Fractionation of the crude product by normal-phase liquid-chromatography and pooling of suitable fractions yielded in four C18-CP-materials with different chlorination degrees (mCl,EA = 39–52%). In addition, polar side-products, tentatively identified as sulfite-, sulfate- and bis-sulfate-diesters, were separated from CPs. The new single-chain materials were characterized by LC-MS, 1H NMR and EA. LC-MS provided Relative retention times for different C18-CP homologues and side-products. Mathematical deconvolution of full-scan mass spectra revealed the presence of chloroparaffins (57–93%) and chloroolefins (COs, 7–26%) in the four single-chain C18-CP-materials. Homologue distributions and chlorination degrees were deduced for CPs and COs. 1H NMR revealed chemical shift ranges of mono-chlorinated (δ = 3.2–5.3 ppm) and non-chlorinated (δ = 1.0–3.2 ppm) hydrocarbon moieties. The synthesized C18 single-chain standard materials and respective spectroscopic data are useful to identify and quantify LCCPs in various materials and environmental samples. CP- and CO-distributions resemble the ones of existing SCCP and MCCP reference materials and technical mixtures. Furthermore, these materials now allow specific studies on the environmental fate and the transformation of long-chain chloroparaffins and chloroolefins.

Powder additive pulsed Nd:YAG laser (wavelength 1064 nm), with the aim of preparing AM of such material. The influence of oxygen content in the initial silicon powders on the continuous tracks morphology was investigated. It was found that the initial oxygen content of the processed powders must be lower than 0.1 wt% to produce a smooth silicon melted track. This result is explained as due to the formation of gaseous manufacturing (AM) of materials is affected by the oxygen present in the raw material, especially if they possess a native oxide. The latter influences the properties of the laser molten track. We carried out a study on the interactions between silicon fine powder (

Laser-assisted microanalysis offers the advantage of determining the spatially resolved compositions in 3D. Scanning a material with a sequence of sampling laser pulses and acquiring online the related spectra allow one to map the lateral and depth distribution of elements and molecules. However, the requirement to analyse smaller and smaller length-scales is challenged by focal diffraction as well as reduction of sensitivity at the nano-scale. Electron-based microprobes still offer unmatched spatial resolution. Disruptive improvements in laser technology are however demonstrated utilizing recently self-developed extreme ultraviolet or soft X-ray lasers. Firstly, a significant enhancement of the resolution is accomplished thanks to a much shorter wavelength, with respect to state-of-the-art commercial lasers. Furthermore, as the most innovative aspect, the sampling efficiency is enhanced using “ionizing radiation”, i.e. directly activating the target material. The high photon-energy (20–100 eV) makes the sampling process essentially single-photon, whatever bond or ionization energy. Furthermore, the analytical setup is simplified to a sampling source and detector, i.e. without the need for a secondary ionization or excitation source as in some state-of-the-art analytical systems. In this review, fundamental aspects of X-ray laser desorption and ablation are discussed, and a survey of the available literature is presented. The main objective is to convince the reader that desorption or ablation in this spectral domain is a significantly cleaner sampling process, with large potential, still requiring investigation for a complete fundamental understanding. Applications of laser microanalysis are thus entering the nano-scale era, which shrinks the gap with electron-based microprobes.

The development of extreme ultraviolet (XUV) sources for tabletop operation has enabled a range of new applications in nano-structuring and spectroscopy. The quantitative characterization of the XUV emission obtained from a pseudospark hollow cathode lamp (HCL) was carried out with a self-developed flat-field spectrometer for the λ < 25 nm spectral range. The wavelength calibration in XUV spectroscopy is challenging, because of the poor grating resolving power for ultrashort wavelengths, which propagate only in a vacuum. Among three alternative methods, flat-field calibration showed the highest accuracy over a wider range. The plasma parameters were extracted from the calibrated spectra. The electron temperatures of the discharged N2, O2 and Ar gases in the HCL are consistent in the range of 17–22 eV. The intensity of the XUV radiation decreased with the increase of working gas pressure, due to self-absorption. A self-developed one-hole HCL exhibited three orders of magnitude higher electron density (Ne = 1.5 × 1019 cm−3) compared to the state-of-the-art three-hole HCL design (Ne = 1016 cm−3), as confirmed by means of collisional-radiative modelling. These results, along with a comparable spectral fingerprint, suggest more extensive and homogeneous excitation across the entire plasma body in the own design.

Rationale Species with ionization energies beyond what is accessible using state-of-the-art lab sources are affected by poor detection limits in ordinary mass spectrometry setups, whose throughput is also often limited. Extreme ultraviolet (XUV) photoionization mass spectrometry, in combination with linear time-of-flight (TOF), is necessary for the sensitive detection of high ionization energy compounds at trace level. XUV photoionization is available at beamlines, although with limited access. A tabletop setup may fill such a gap. Methods A self-developed tabletop system, based on a plasma discharge with extreme ultraviolet emission (λ = 5-50 nm) coupled to a TOF mass spectrometer, was used in this study. Simultaneous validation measurements with a reference electron ionization quadrupole mass filter were carried out. An in-house developed hollow toroidal coil (HTC) induction detector was used for concomitant photoelectron detection. Results Straightforward XUV mass spectra without fragmentation, thanks to the single-photon ionization, were acquired. The measurements with the reference quadrupole were in agreement with the spectra acquired by XUV-TOF. The resolution obtained for N2 was at least factor of 2 higher than that measured with the reference quadrupole. Initial energy distributions of photoelectrons were retrieved by cross-correlation that gave access to the photoionization distribution. Conclusions The system allows XUV single-photon ionization of elements and molecules with IE >10 eV that are of fundamental interest e.g. for water splitting and catalysis research. The demonstrated performance is now suitable for a prototype platform.

Laser-induced breakdown spectroscopy (LIBS) is an elemental analysis method thanks to minor sample preparation, rapid analysis, and a spatially resolved sensitivity down to trace level in any kind of sample matrix. State-of-the-art LIBS is operated in the optical spectral range (UV-Vis). Unfortunately, the application of LIBS in material detection is limited by the low precision and repeatability. This is particularly critical for inhomogeneous materials and alternative methods are desirable. Light elements such as Li, as well as F, are difficult to be characterized. The dual LIBS performance was initially studied in a simpler matrix such as LiF, radially collecting simultaneously the XUV and OES spectra from the same laser shot. For the case of LiF, XUV signals proved significantly more stable than in the case of LIBS-OES. The signal of F can be also seen clearly in the spectrum. Observation of the plasma emission at even shorter wavelengths in the extreme ultraviolet (wavelength range 5-20 nm) is supposed to improve the state-of-art limitations of LIBS.

Lensless imaging requires coherent illumination, which is typically available at beamlines. A study of lensless imaging with a table-top X-ray laser is presented, comparing two alternative data-processing techniques, i.e. using the near and the far field data. In order to have a consistent comparison, a Fresnel zone plate was studied as object, because its modulated structure permits to obtain both Fresnel (near field) and Fraunhofer (far field) pattern simultaneously. Results show factor of 3 difference in imaging resolution, and a major limitation given by the degree of the illumination homogeneity.

Design and development of a compact chirped pulse amplification (CPA) laser is presented. This system will be used to generate coherent tabletop X-rays based on laser-produced plasmas (LPP) for round the clock advanced spectroscopy. The building blocks of the laser are shown and the results from the front-end are laid out. The progress on the amplification stages is presented with a scheme to extract compressed 15 J laser pulses at the output which are to be characterized and hit on rotating target for generating a plasma with enough population inversion (Ne-like or Ni-Like) as such to enable the emission of Soft X-rays. Soft X-rays laser lines from different targets will be characterized and used for different spectroscopy experiments.

The 17th International Conference on X-ray Lasers (ICXRL 2020) was a milestone in several ways. Firstly, was a milestone in this scientific community because for the first time the conference came to the participants' home, due to the outbreak of the pandemics, rather than the opposite. The organization of an online event was a challenge because was a brand new platform for both the organizers and the participants, and because it was put together in less than six months. The planned physical event in Rome, already tested with one year in advance, had to be withdrawn as it posed major risks to potential participants. ICXRL 2020 was milestone also because the increased proportion of papers on technological deployment of X-ray lasers. Of course, research on fundamentals and innovation still carried an important part of this thirtyfour year event. Finally, ICXRL 2020 was a milestone also because there were participants from all five continents, no one excluded, and some were forced to incredible efforts to stay up and present their research. A great sign of inclusion. Last but not least, ICXRL 2020 saw four best presentation "Pierre Jaegle" awards, equally split between female and male students: Adeline Kabacinski (LOA, France), Lydia Rush (CSU, USA, see ref. [33]), Felix Wiesner (FSU, BRD), Julius Reinhard (HIJ, BRD). Another great sign of inclusion.

Technical chlorinated paraffins (CPs) are produced via radical chlorination of n-alkane feedstocks with different carbon chain-lengths (∼C

Structure, reactivity and physico-chemical properties of polyhalogenated compounds determine their up-take, transport, bio-accumulation, transformation and toxicity and their environmental fate. In technical mixtures of chlorinated paraffins (CPs), these properties are distributed due to the presence of thousands of homologues. We hypothesized that roles of CP dehalogenation reactions, catalyzed by the haloalkane dehalogenase LinB, depend on structural properties of the substrates, e.g. chlorination degree and carbon-chain length. We exposed mixtures of chlorinated undecanes, dodecanes and tridecanes in-vitro to LinB from Sphingobium Indicum bacteria. These single-chain CP-materials also contain small amounts of chlorinated olefins (COs), which can be distinct by mathematical deconvolution of respective mass-spectra. With this procedure, we obtained homologue-specific transformation kinetics of substrates differing in saturation degree, chlorination degree and carbon chain-length. For all homologues, two-stage first-order kinetic models were established, which described the faster conversion of reactive material and the slower transformation of more persistent material. Half-lifes of 0.5–3.2 h and 56–162 h were determined for more reactive and more persistent CP-material. Proportions of persistent material increased steadily from 18 to 67% for lower (Cl6) to higher (Cl11) chlorinated paraffins and olefins. Conversion efficiencies decreased with increasing chlorination degree from 97 to 70%. Carbon-chain length had only minor effects on transformation rates. Hence, the conversion was faster and more efficient for lower-chlorinated material, and slower for higher-chlorinated and longer-chained CPs and COs. Current legislation has banned short-chain chlorinated paraffins (SCCPs) and forced a transition to longer-chain CPs. This may be counterproductive with regard to enzymatic transformation with LinB.

Short-chain chlorinated paraffins (SCCPs) are listed as persistent organic pollutants (POPs) under the Stockholm Convention. Such substances are toxic, bioaccumulating, transported over long distances and degrade slowly in the environment. Certain bacterial strains of the Sphingomonadacea family are able to degrade POPs, such as hexachlorocyclohexanes (HCHs) and hexabromocyclododecanes (HBCDs). The haloalkane dehalogenase LinB, expressed in certain Sphingomonadacea, is able to catalyze the transformation of haloalkanes to hydroxylated compounds. Therefore, LinB is a promising candidate for conversion of SCCPs. Hence, a mixture of chlorinated tridecanes was exposed in vitro to LinB, which was obtained through heterologous expression in Escherichia coli. Liquid chromatography mass spectrometry (LC-MS) was used to analyze chlorinated tridecanes and their transformation products. A chloride-enhanced soft ionization method, which favors the formation of chloride adducts [M+Cl]- without fragmentation, was applied. Mathematical deconvolution was used to distinguish interfering mass spectra of paraffinic, mono-olefinic and di-olefinic compounds. Several mono- and di-hydroxylated products including paraffinic, mono-olefinic and di-olefinic compounds were found after LinB exposure. Mono- (rt = 5.9-6.9 min) and di-hydroxylated (rt = 3.2-4.5 min) compounds were separated from starting material (rt = 7.7-8.5 min) by reversed phase LC. Chlorination degrees of chlorinated tridecanes increased during LinB-exposure from nCl = 8.80 to 9.07, indicating a preferential transformation of lower chlorinated (Cl

An amendment to this paper has been published and can be accessed via a link at the top of the paper.

An experimental study of temporally and spatially resolved spark-induced breakdown spectroscopy (SIBS) of methane and hydrogen-enriched methane mixtures is reported for premixed combustion in internal combustion engines. Experiments were conducted at quiescent conditions in a small constant volume chamber, varying pressure, stoichiometry and hydrogen admixture rates. Spectral emissions of hydroxyl (OH) at 306 nm, NH at 336 nm, the cyanogen (CN) band at 388 nm and the nitrogen second positive system (N2) were spatially resolved on a time-integrated setup. OH emissions were found to be strongest between the electrodes, whereas CN emissions were more pronounced at the center and ground electrode. Metal emission lines were observed, partially interfering with the radicals of interest. Energy dispersive X-ray spectroscopy showed nickel, copper and iron shares in the noble metal electrodes, confirming the origin of these metal emissions. Simultaneously to time-integrated spectra, temporally-resolved spectra at a frame rate of 100 kHz were recorded during the glow phase of the electrical discharge. Comparison of both spectra revealed a good agreement in terms of spectral characteristics and resolved species. Temporally-resolved spectra highlighted the strong dependence on the electric discharge characteristics of the inductive coil ignition system in the early phase of ignition. Ratios of CN/OH and CN/NH were found to correlate with the fuel-air equivalence ratio, but shot to shot repeatability was up to a factor 3 larger than the dependence on the mixture composition. Moreover, these ratios changed with increasing pressure at ignition timing, and with the higher pressure metal emission lines became more pronounced. Additionally, at pressures higher than 2 bar, the equilibrium position shifted to the disadvantage of the second positive system of nitrogen, suppressing this emission. Hydrogen admixture to methane of up to 50 vol% were found to not significantly alter the spectral signature between 300 and 400 nm, only marginally affecting the signal ratios of CN/OH and CN/NH.

Biofilms causing medical conditions or interfering with technical applications can prove undesirably resistant to silver nanoparticle (AgNP)-based antimicrobial treatment, whereas beneficial biofilms may be adversely affected by the released silver nanoparticles. Isolated biofilm matrices can induce reduction of silver ions and stabilization of the formed nanosilver, thus altering the exposure conditions. We thus study the reduction of silver nitrate solution in model experiments under chemically defined conditions as well as in stream biofilms. Formed silver nanoparticles are characterized by state-of-the art methods. We find that isolated biopolymer fractions of biofilm organic matrix are capable of reducing ionic Ag, whereas other isolated fractions are not, meaning that biopolymer fractions contain both reducing agent and nucleation seed sites. In all of the investigated systems, we find that silver nanoparticle–biopolymer interface is dominated by carboxylate functional groups. This suggests that the mechanism of nanoparticle formation is of general nature. Moreover, we find that glucose concentration within the biofilm organic matrix correlates strongly with the nanoparticle formation rate. We propose a simple mechanistic explanation based on earlier literature and the experimental findings. The observed generality of the extracellular polymeric substance/AgNP system could be used to improve the understanding of impact of Ag+ on aqueous ecosystems, and consequently, to develop biofilm-specific medicines and bio-inspired water decontaminants.

Direct nano-scale microanalysis is important for photovoltaic functional thin films to characterize their homogeneity and purity. This demands combining spatial resolution in the micro/nano-scale and sensitivity in the trace-level range, which is at the moment beyond state-of-the-art. As dictated by counting statistics, the reduction of the spot size degrades the detection limit. The utilization of a tabletop XUV laser at λ = 46.9 nm has shown to dramatically improve the ablation efficiency with respect to that of visible lasers, such that ablation spot of 1 μm limits. Li-doped Cu2ZnSn(S,Se)4 (so-called kesterite) thin films were irradiated across 3D ablation arrays for hyperspectral mapping by means of time-of-flight mass spectrometry. The nominal 3D data node lattices were the initialisation perceptron, filled with measured values, and for a detailed supervised learning postprocessing, the node-to-node links were analysed by means of a 2D-kernel covariance algorithm. The latter permitted to obtain robust 3D elemental distribution functions well below the measurement spacing, giving insights into the inhomogeneity and impurities.

The range of commercial techniques for high-resolution gas-chromatography-mass spectrometry (GC-MS) has been recently extended with the introduction of GC Orbitrap Fourier transform mass spectrometry (FTMS). We report on progress with quantitation performance in the analysis of persistent organic pollutants (POP), by averaging of time-domain signals (transients), from a number of GC-FTMS experiment replicates. Compared to a standard GC-FTMS measurement (a single GC-FTMS experiment replicate, mass spectra representation in reduced profile mode), for the 10 GC-FTMS technical replicates of ultratrace POP analysis, sensitivity improvement of up to 1 order of magnitude is demonstrated. The accumulation method was implemented with an external high-performance data acquisition system and dedicated data processing software to acquire the time-domain data for each GC-FTMS replicate and to average the acquired GC-FTMS data sets. Concomitantly, the increased flexibility in ion signal detection allowed the attainment of ultrahigh-mass resolution (UHR), approaching R = 700 000 at m/z = 200.

A capillary discharge X-ray laser is a tabletop coherent source, which has matured for application in microanalysis. Soft X-ray pulses were delivered onto functional materials to induce photo-ablation in the nanoscale. Such samplings were measured inline by means of mass spectrometry, and thus perform depth profile analysis. This paper discusses the complementarity or this technique to contending microanalytical techniques, to have a direct methodology for space resolved in situ thin film characterization.

Spark-induced Breakdown Spectroscopy was used for local fuel-air equivalence ratio measurements of premixed methane-air mixtures by a discharge from an inductive ignition system in a constant volume cell. Elemental emissions of hydrogen Balmer-alpha line (Hα), nitrogen (N746) and oxygen (O777) were experimentally observed in the vicinity of the electrode gap, using a lens-coupled spectrometer and an intensified camera. After optimization of the gating strategy, the spectral emission features, i.e. line intensity ratios and peaks width (full width at half maximum) ratios were analyzed and their relation with the local fuel-air equivalence ratio at the spark plug was discussed, for operating pressures ranging from 10 to 20 bar. Results showed that a change in pressure and temperature did not affect the spectral emissions' atomic peaks ratios, as long as the density was kept constant. For tests at constant temperature and at constant pressure, the peaks intensity ratios showed a linear correlation with local fuel-air equivalence ratio, while peaks width did not show noticeable changes. When pressure was varied, while keeping temperature and fuel-air equivalence ratio constant, a different behavior was observed: peaks intensity ratio were only slightly affected by pressure change, more prominently at fuel-rich conditions, while a peak broadening was clearly recognizable, as the peak width linearly increased with pressure. Moreover, an additional optical setup involving a fiber-optic spark plug was implemented with the aim to adapt the proposed diagnostic tool to engines in operando. Comparisons with the lens setup showed that the developed technique is promising as a compact and versatile tool for applications involving local fuel-air equivalence ratio measurements at different ambient conditions.