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Dr Martin Seah, NPL, was the initiator, founder, and first chairman of the Surface Analysis Working Group (SAWG) at the Consultative Committee for Amount of Substance, Metrology in Chemistry and Biology (CCQM) at the Bureau International des Poids et Mesures (BIPM), the international organization established by the Metre Convention. This tribute letter summarizes his achievements during his chairmanship and his long-running impact on the successful work of the group after his retirement.
The visualization of index-of-refraction (IoR) distribution is one of the common methods to investigate fluid flow or pressure fields. While schlieren and shadowgraphy imaging techniques are widely accepted, their inherent limitations often lead to difficulties in elucidating the IoR distribution and extracting the true IoR information from the resulting images. While sophisticated solutions exist, the IoR-gradient-to-image was achieved by purposely introducing a commonly avoided “defect” into the optical path of a conventional coincident schlieren/shadowgraphy setup; the defect is a combination of slight defocusing and the use of non-conjugate optical components. As such, the method presented in this work is referred to as defocusing shadowgraphy, or DF-shadowgraphy. While retaining the ease of a conventional schlieren/shadowgraphy geometry, this DF approach allows direct visualization of complicated resonant acoustic fields even without any data processing. For instance, the transient acoustic fields of a common linear acoustic resonator and a two-dimensional one were directly visualized without inversion. Moreover, the optical process involved in DF-shadowgraphy was investigated from a theoretical perspective. A numerical solution of the sophisticated impulse response function was obtained, which converts the phase distortion into intensity distributions. Based on this solution, the IoRs of various gas streams (e.g., CO2 and isopropanol vapor) were determined from single images.
Cardiolipin (CL) is a major cardiac mitochondrial phospholipid maintaining regular mitochondrial morphology and function in cardiomyocytes. Cardiac CL production includes ist biosynthesis and a CL-remodeling process. Here we studied the impact of CL-biosynthesis and the enzyme Cardiolipin Synthase (CLS) on cardiac function.
CLS and cardiac CL-species were significantly downregulated in cardiomyocytes following catecholamine-induced cardiac damage in mice, accompanied by increased oxygen consumption rates, signs of oxidative stress and mitochondrial uncoupling. RNAi-mediated cardiomyocyte-specific knockdown of CLS in Drosophila melanogaster resulted in marked cardiac dilatation, severe impairment of systolic performance and slower diastolic filling velocity assessed by fluorescence-based heart imaging. Finally, we showed that CL72:8 is significantly decreased in cardiac samples from patients with heart failure with reduced ejection fraction (HFrEF). In summary, we identified CLS as a regulator of cardiac function. Considering the cardiac depletion of CL-species in HFrEF, pharmacological targeting of CLS may be a promising therapeutic approach.zeige mehrzeige weniger
Atherosclerosis is a progressive inflammatory vascular disease characterized by endothelial dysfunction and plaque burden. Extracellular matrix (ECM)-associated plasma proteins play an important role in disease development. Our magnetic resonance imaging (MRI) study investigates the feasibility of using two different molecular MRI probes for the simultaneous assessment of ECM-associated intraplaque albumin deposits caused by endothelial damage and progressive inflammation in atherosclerosis. Male apolipoprotein E-deficient (ApoE-/-)-mice were fed a high-fat diet (HFD) for 2 or 4 months. Another ApoE-/--group was treated with pravastatin and received a HFD for 4 months. T1- and T2*-weighted MRI was performed before and after albumin-specific MRI probe (gadofosveset) administration and a macrophage-specific contrast agent (ferumoxytol). Thereafter, laser ablation inductively coupled plasma mass spectrometry and histology were performed. With advancing atherosclerosis, albumin-based MRI signal enhancement and ferumoxytol-induced signal loss areas in T2*-weighted MRI increased. Significant correlations between contrast-to-noise-ratio (CNR) post-gadofosveset and albumin stain (R2 = 0.78, p < 0.05), and signal loss areas in T2*-weighted MRI with Perls’ Prussian blue stain (R2 = 0.83, p < 0.05) were observed. No interference of ferumoxytol with gadofosveset enhancement was detectable. Pravastatin led to decreased inflammation and intraplaque albumin. Multi-target MRI combining ferumoxytol and gadofosveset is a promising method to improve diagnosis and treatment monitoring in atherosclerosis.
Simvastatin (SV) is an important active pharmaceutical ingredient (API) for treatment of hyperlipidemias, which is known to exist in different crystalline and amorphous phases. It is, therefore, an interesting model to investigate how the outcome of evaporative crystallization in the contactless environment of an acoustically levitated droplet may be influenced by key experimental conditions, such as temperature, solvent properties (e.g., polarity and hygroscopicity), and dynamics of the evaporation process. Here, we describe a real-time and in situ study of simvastatin evaporative crystallization from droplets of three solvents that differ in volatility, polarity, and protic character (acetone, ethanol, and ethyl acetate). The droplet monitorization relied on synchrotron X-ray diffraction (XRD), Raman spectroscopy, imaging, and thermographic analysis. A pronounced solvent-dependent behavior was observed. In ethanol, a simvastatin amorphous gel-like material was produced, which showed no tendency for crystallization over time; in ethyl acetate, a glassy material was formed, which crystallized on storage over a two-week period to yield simvastatin form I; and in acetone, form I crystallized upon solvent evaporation without any evident presence of a stable amorphous intermediate. The XRD and Raman results further suggested that the persistent amorphous phase obtained from ethanol and the amorphous precrystallization intermediate formed in ethyl acetate were similar. Thermographic analysis indicated that the evaporation process was accompanied by a considerable temperature decrease of the droplet surface, whose magnitude and rate correlated with the solvent volatility (acetone > ethyl acetate > ethanol). The combined thermographic and XRD results also suggested that, as the cooling effect increased, so did the amount of residual water (most likely captured from the atmosphere) remaining in the droplet after the organic solvent was lost. Finally, the interpretation of the water fingerprint in the XRD time profiles was aided by molecular dynamics simulations, which also provided insights into the possible role of H2O as an antisolvent that facilitates simvastatin crystallization.
The knowledge about energy release and transient behaviour of flash lamps, used as short-term energy source in flash thermography investigations, is essential for a quantitative analysis of the results as well as for simulations regarding such experiments. Usually, only a rectangular pulse shape of a typical duration of a few milliseconds is regarded when flash lamps pulses are described. This note considers the afterglow period of a flash lamp explicitly and shows that negligence of this afterglow effect leads to a systematic underestimation of the pulse length and the related total energy release. In the reported case, the intensity transient recorded by a Silicon photo diode was transformed into a temperature transient, allowing the study of the real energy release. It turns out that approximately only 50% of the entire pulse energy were released during the usually regarded period of 2.8 ms, while the other half was released within a period of 20 ms with an exponential decay.
ISO 18516:2019 Surface chemical analysis—Determination of lateral resolution and sharpness in beam-based methods with a range from nanometres to micrometres revises ISO 18516:2006 Surface chemical analysis—Auger electron spectroscopy and X-ray photoelectron spectroscopy—Determination of lateral resolution. It implements three different methods delivering parameters useful to express the lateral resolution: (1) the straight edge method, (2) the narrow line method and (3) the grating method. The theoretical background of these methods is introduced in ISO/TR 19319:2013 Surface chemical analysis—Fundamental approaches to determination of lateral resolution and sharpness in beam-based methods. The revised International Standard ISO 18516 delivers standardized procedures for the determination of the (1) effective lateral resolution by imaging of square-wave gratings, the (2) lateral resolution expressed as the parameter D12–88 characterizing the steepness of the sigmoidal edge spread function (ESF) determined by imaging a straight edge and (3) the lateral resolution expressed as the full width of half maximum of the line spread function (LSF), wLSF, determined by imaging a narrow line. The last method also delivers information on the shape of the LSF, which characterizes an individual imaging instrument. Finally, the implementation of all three standardized methods in the field of imaging laboratory X-ray photoelectron spectroscopy (XPS) is shortly presented. This part of the letter is based on the use of a new test sample developed at ETH Zurich, Switzerland. This test sample displays a micrometre scaled pattern motivated by the resolving power of recent imaging XPS instruments.
Metal-containing nanoparticles (NP) can be characterized with inductively coupled plasma mass spectrometers (ICP-MS) in terms of their size and number concentration by using the single-particle mode of the instrument (spICP-MS). The accuracy of measurement depends on the setup, operational conditions of the instrument and specific parameters that are set by the user. The transport efficiency of the ICP-MS is crucial for the quantification of the NP and usually requires a reference material with homogenous size distribution and a known particle number concentration.
Currently, NP reference materials are available for only a few metals and in limited sizes. If particles are characterized without a reference standard, the results of both size and particle number may be biased. Therefore, a dual-inlet Setup for characterizing nanoparticles with spICP-MS was developed to overcome this problem. This setup is based on a conventional introduction system consisting of a pneumatic nebulizer (PN) for nanoparticle solutions and a microdroplet Generator (μDG) for ionic calibration solutions. A new and flexible interface was developed to facilitate the coupling of μDG, PN and the ICP-MS system. The interface consists of available laboratory components and allows for the calibration, nanoparticle (NP) characterization and cleaning of the arrangement, while the ICP-MS instrument is still running.
Three independent analysis modes are available for determining particle size and number concentration. Each mode is based on a different calibration principle.
While mode I (counting) and mode III (μDG) are known from the literature, mode II (sensitivity), is used to determine the transport efficiency by inorganic ionic Standard solutions only. It is independent of NP reference materials. The μDG based inlet system described here guarantees superior analyte sensitivities and, therefore, lower detection limits (LOD). The size dependent LODs achieved are less than 15 nm for all NP (Au, Ag, CeO2) investigated.
Thermally stable carbon nitride nanostructures have potential applications in surface coatings and automotive fields. In this work, hydrogenated nitrogen-rich carbon nitride nanoparticles have been synthesised via low-pressure low-power plasma vapour deposition technique from methane/Nitrogen gas mixture in a dry process. Thermal stability of the initially prepared hydrogenated carbon Nitride structures has been analysed by near-edge X-ray absorption fine-structure spectroscopy (NEXAFS, insitu), Raman spectroscopy, scanning and transmission electron microscopy and nuclear reaction Analysis (NRA). Thermal studies reveal the excellent stability of the material and nitrogen-rich characteristics (N/C ratio 0.5e0.2 ± 0.01). The obtained results suggest transformation of sp3-rich as-deposited carbon Nitride into sp2-carbon phase with more graphitic features upon thermal annealing. Such in-situ thermal studies of plasma deposited carbon nitrides confirm the conversion of sp3-rich phase to sp2-rich carbon phase at the critical temperature (about 450 K), without a huge loss in nitrogen content. The analysis revealed that the material is a stable plasma deposit after this critical temperature up to >1100 K. Additionally, super hydrophilic carbon nitride nanostructure transforms into a hydrophobic surface after thermal annealing.
These thermally stable hydrophobic carbon nitride nanoparticles could be used as a promising material for the hydrophobic coatings for various applications, especially for harsh conditions.
For the large-scale generation of hydrogen via water electrolysis the design of long term stable and active catalysts for the oxygen evolution reaction (OER) remains a key challenge. Most catalysts suffer from severe structural corrosion that becomes even more pronounced at fluctuating potentials. Herein, MnCo based cubic particles were prepared via a hydrothermal approach, in which the edge length of the micron-sized particles can be controlled by changing the pH value of the precursor solution. The cubes are composed of varying amounts of MnCo2O4, CoCO3 and a mixed (Mn/Co)CO3 phase. Structure–activity relationships were deduced revealing a volcano-type behavior for the intrinsic OER activity and fraction of spinel oxide phase.
A low overpotential of 0.37 V at 10 mA cm−2 and a stability of more than 25 h was achieved in 1.0 M KOH using a rotating disc electrode (RDE) setup. The best performing catalyst material was successfully tested under dynamic process conditions for 9.5 h and shows a superior catalytic activity as anode for the Overall water splitting in an electrolyser setup in 1.0 M KOH at 333 K compared to a reference NiCo-spinel catalyst.
Important chemical process of reduction of SiF4 by hydrogen is realized in laser induced dielectric breakdown (LIDB) plasma in a gas mixture of SiF4 and H2. The process may be an alternative to a method of Plasma enhanced chemical vapor deposition (PECVD) which is commonly used for production of pure and isotopically pure silicon films. The composition of laser induced plasma in gases SiF4, SiF4 + H2, SiF4 + H2 + Ar at atmospheric pressure is studied and compared to the composition of inductively coupled plasma (ICP) in the same gases but at reduced pressure of 3 Torr. The gaseous products of chemical reactions are inferred from optical emission spectroscopy (OES) and IR spectroscopy. The reaction products of silicon fluoride SiF and fluorosilanes SiHxFy (x, y = 1, 2, 3) in LIDB plasma are observed and confirmed by equilibrium chemistry calculations and simulations of plasma expansion dynamics using a fluid dynamic-chemical plasma model. It is further suggested that chemisorption of fluorinated species like SiFx (x = 1, 2) followed by the surface reaction with H-atoms lead to a formation of silicon-to‑silicon bonds on a substrate surface. A conclusion is drawn that energetic laser
induced plasma can prove efficient for one-step PECVD by hydrogen reduction of SiF4.
Mechanochemistry has become a valuable tool for the synthesis of new molecules, especially in the field of organic chemistry. In the present work, we investigate the kinetic profile of the chlorination reaction of N-3-ethyl-5,5-dimethylhydantoin (EDMH) activated and driven by ball milling. The reaction has been carried out using 2 mm, 4 mm, 5 mm, 6 mm, and 8 mm ball sizes in a new small custom-made Perspex milling jar. The Crystal structure of the starting material EDMH and the 1-chloro-3-ethyl5,5′-dimethyl hydantoin (CEDMH) chlorination product was solved by single-crystal X-ray diffraction. The reaction was monitored, in situ and in real time, by both powder X-ray diffraction (PXRD) and Raman spectroscopy. Our kinetic data show that the reaction progress to equilibrium is similar at all milling ball sizes. The induction period is very short (between 10 and 40 s) when using 4 mm, 5 mm, 6 mm, and 8 mm balls. For the reaction performed with a 2 mm ball, a significantly longer induction period of 9 min was observed. This could indicate that an initial energy accumulation and higher mixing efficiency are necessary before the reaction starts. Using different kinetic models, we found that the amount of powder affected by critical loading conditions during individual impacts is significantly dependent on the ball size used. An almost linear correlation between the rate of the chemical transformations and the ball volume is observed.
Iron-based catalysts have been reported manifold and studied as platinum group metal (PGM) free alternatives for the catalysis of the oxygen reduction reaction (ORR). However, their sustainable preparation by greener synthesis approaches is usually not discussed. In this work, we propose a new method for the sustainable preparation of such catalysts by using a mechanochemical approach, with no solvents and non-toxic chemicals. The materials obtained from low temperature carbonization (700 °C) exhibit considerable and stable catalytic performance for ORR in alkaline medium. A catalyst obtained
from iron hydroxide, tryptophan, dicyandiamide, and ammonium nitrate shows the best electrocatalytic Performance with an overpotential of 921 mV vs. RHE at 0.1 mA/cm2 and an electron transfer number of 3.4.
The molecular dynamics of addition-type poly(tricyclononenes) with Si-substituted bulky side groups has been investigated by a combination of neutron time-of-flight and neutron backscattering spectroscopy methods on a time scale from 0.1 ps to ca. 3 ns. The investigated poly(tricyclononenes) PTCNSi1 and PTCNSi2g both bear a high microporosity which makes them promising candidates for active separation layers for gas separation membranes. At least for larger gas molecules it is assumed that the pathways for diffusion require an enlargement of pre-existing micropores in terms of an activated zone. A low temperature relaxation process was found for both polymers by the performed neutron scattering experiments. This process was assigned to the methyl group rotation. It was analysed in terms of a jump diffusion in a three-fold potential. The analysis of the dependence of the elastic incoherent structure factor on the scattering vector yields the number of methyl groups which might be immobilized. For PTCNSi1 (3 methyl groups in the monomeric unit) it was found that all methyl groups take part in the methyl group rotation whereas for PTCNSi2g (6 methyl groups in monomeric unit) a considerable number of methyl groups are blocked in their rotation. This immobilization of methyl groups is due to the sterically demanding arrangement of the methyl groups in PTCNSi2g. This conclusion is further supported by the result that the activation energy for the methyl group rotation is three times higher for PTCNSi2g than that of PTCNSi1.
Layer-by-layer additive manufacturing (AM) by means of laser-powder bed Fusion (L-PBF) offers many prospects regarding the design of lattice structures used, for example, in gas turbines. However, defects such as bulk porosity, Surface roughness, and re-entrant features are exacerbated in nonvertical structures, such as tilted struts. The characterization and quantification of these kinds of
defects are essential for the correct estimation of fracture and fatigue properties.
Herein, cylindrical struts fabricated by L-PBF are investigated by means of X-ray computed tomography (XCT), with the aim of casting light on the dependence of the three kinds of defects (bulk porosity, surface roughness, and re-entrant features) on the build angle. Innovative analysis methods are proposed to correlate shape and position of pores, to determine the angular-resolved Surface roughness, and to quantify the amount of re-entrant surface features, q. A meshing of the XCT surface enables the correlation of q with the classical Surface roughness Pa. This analysis leads to the conclusion that there is a linear correlation between q and Pa. However, it is conjectured that there must be a threshold of surface roughness, below which no re-entrant features can be build.
High-resolution continuum source graphite furnace molecular absorption spectrometry (HR-CS-GF-MAS) was employed for determining adsorbable organic chlorine (AOCl) in water. Organic chlorine was indirectly quantified by monitoring the molecular absorption of the transient aluminum monochloride molecule (AlCl) around a wavelength of 261.42 nm in a graphite furnace. An aluminum solution was used as the molecularforming modifier. A zirconium coated graphite furnace, as well as Sr and Ag solutions were applied as modifiers for a maximal enhancement of the absorption signal. The pyrolysis and vaporization temperatures were 600 °C and 2300 °C, respectively. Non-spectral interferences were observed with F, Br, and I at concentrations higher than 6 mg L-1, 50 mg L-1, and 100 mg L-1, respectively. Calibration curves with NaCl, 4-chlorophenol, and trichlorophenol present the same slope and dynamic range, which indicates the chlorine atom specificity of the method. This method was evaluated and validated using synthetic water samples, following the current standard DIN EN ISO 9562:2004 for the determination of the sum parameter adsorbable organic halides (AOX) for water quality. These samples contain 4-chlorophenol as the chlorinated organic standard in an inorganic chloride matrix. Prior to analysis, organic chlorine was extracted from the inorganic matrix via solid-phase extraction with a recovery rate >95%. There were no statistically significant differences observed between measured and known values and for a t-test a confidence level of 95% was achieved. The limits of detection and characteristic mass were found to be 48 and 22 pg, respectively. The calibration curve was linear in the range 0.1–2.5 ng with a correlation coefficient R2 = 0.9986.
The neutron imaging instrument CONRAD was operated as a part of the user program of the research reactor BER‐II at Helmholtz‐Zentrum Berlin (HZB) from 2005 to 2020. The Instrument was designed to use the neutron flux from the cold source of the reactor, transported by a curved neutron guide. The pure cold neutron spectrum provided a great advantage in the use of different neutron optical components such as focusing lenses and guides, solid‐state polarizers, Monochromators and phase gratings. The flexible setup of the instrument allowed for implementation of new methods including wavelength‐selective, dark‐field, phase‐contrast and imaging with polarized neutrons. In summary, these developments helped to attract a large number of scientists and industrial customers, who were introduced to neutron imaging and subsequently contributed to the Expansion of the neutron imaging community.
The quantification of the sulphur mass fraction in pure copper and copper alloys by GDMS and LA-ICP-MS revealed a lack of traceability mainly due to a lack of suitable certified reference materials for calibrating the instruments. Within this study GDMS and LA-ICP-MS were applied as routine analytical tools to quantify sulphur in copper samples by applying reference materials as calibrators, which were characterized for their sulphur mass fraction by IDMS beforehand. Different external calibration strategies were applied including a matrix cross type calibration. Both techniques with all calibration strategies were validated by using certified reference materials (others than those used for calibration) and good agreement with the reference values was achieved except for the matrix cross type calibration, for which the agreement was slightly worse. All measurement results were accompanied by an uncertainty statement. For GDMS, the relative expanded (k = 2) measurement uncertainty ranged from 3% to 7%, while for LA-ICP-MS it ranged from 11% to 33% when applying matrix-matched calibration in the sulphur mass fraction range between 25 mg kg-1 and 1300 mg kg-1. For cross-type calibration the relative expanded (k = 2) measurement uncertainty need to be increased to at least 12% for GDMS and to at least 54% for LA-ICP-MS to yield metrological compatibility with the reference values. The so obtained measurement results are traceable to the international system of units (SI) via IDMS reference values, which is clearly illustrated by the unbroken chain of calibrations in the metrological traceability scheme.
The characterization of technical lignins is a key step for the efficient use and processing of this material into valuable chemicals and for quality control. In this study 31 lignin samples were prepared from different biomass sources (hardwood, softwood, straw, grass) and different pulping processes (sulfite, Kraft, organosolv). Each lignin was analysed by attenuated total reflectance Fourier transform infrared (ATR-FT-IR) spectroscopy. Statistical analysis of the ATR-FT-IR spectra by means of principal component analysis (PCA) showed significant differences between the lignins. Hence, the samples can be separated by PCA according to the original biomass. The differences observed in the ATR-FT-IR spectra result primarily from the relative ratios of the p-hydroxyphenyl, guaiacyl and syringyl units. Only limited influence of the pulping process is reflected by the spectral data. The spectra do not differ between samples processed by Kraft or organosolv processes. Lignosulfonates are clearly distinguishable by ATR-FT-IR from the other samples. For the classification a model was created using the k-nearest neighbor (k NN) algorithm. Different data pretreatment steps were compared for k=1…20. For validation purposes, a 5-fold cross-validation was chosen and the different quality criteria Accuracy (Acc), Error Rate (Err), Sensitivity (TPR) and specificity (TNR) were introduced. The optimized model for k=4 gives values for Acc = 98.9 %, Err = 1.1 %, TPR = 99.2 % and TNR = 99.6 %.
Annexin A5 (anxA5) is a marker for apoptosis, but has also therapeutic potential in cardiovascular diseases, cancer, and, due to apoptotic mimicry, against dangerous viruses, which is limited by the short blood circulation. An 864-amino-acid XTEN polypeptide was fused to anxA5. XTEN864-anxA5 was expressed in Escherichia coli and purified using XTEN as tag.
XTEN864-anxA5 was coupled with DTPA and indium-111. After intravenous or subcutaneous injection of 111In-XTEN864-anxA5, mouse blood samples were collected for blood half-life determination and organ samples for biodistribution using a gamma counter. XTEN864-anxA5 was labeled with 6S-IDCC to confirm binding to apoptotic cells using flow cytometry.
To demonstrate targeting of atherosclerotic plaques, XTEN864-anxA5 was labeled with MeCAT(Ho) and administered intravenously to atherosclerotic ApoE−/−mice. MeCAT(Ho)-XTEN864-anxA5 was detected together with MeCAT(Tm)-MAC-2 macrophage antibodies by imaging mass cytometry (CyTOF) of aortic root sections. The ability of anxA5 to bind apoptotic cells was not affected by XTEN864. The blood half-life of XTEN864-anxA5 was 13 h in mice after IV injection, markedly longer than the 7-min half-life of anxA5. 96 h after injection, highest amounts of XTEN864-anxA5 were found in liver, spleen, and kidney. XTEN864-anxA5 was found to target the adventitia adjacent to atherosclerotic plaques. XTEN864-anxA5 is a long-circulating fusion protein that can be efficiently produced in E. coli and potentially circulates in humans for several days, making it a promising therapeutic drug.
With the aim of identifying the origin and the manufacturer of a cement, a reliable procedure that provides unambiguous results is needed. Such procedure could resolve practical issues in damage research, liability issues and forensic investigations. A substantial number of attempts for fingerprinting of building materials, including cement, has already been carried out during the last decades. Most of them were based on concentration analysis of the main elements/components. This review provides an overview of provenance studies of cement and the main approaches commonly used. Provenance studies of cement via isotope techniques are also presented and discussed as representatives of the state-of-the-art in the field. Due to the characteristic properties and the occurrence of carefully selected isotope ratios, unique fingerprints of different kinds of materials can be provided by these methods. This property has largely been explored in various scientific fields such as geo- and cosmochemistry, food forensics, archaeology, geochronology, biomedical studies, and climate change processes. However, the potential of isotope techniques in cement and concrete research for provenance studies has barely been investigated.
Therefore, the review outlines a suitable approach using isotope ratios, which could lead to reliable provenancing of cementitious materials in the future.
To date, the destructive extraction and analysis of drilling cores is the main possibility to obtain depth information about damaging water ingress in building floors. The time- and costintensive procedure constitutes an additional burden for building insurances that already list piped water damage as their largest item. With its high sensitivity for water, a ground-penetrating radar (GPR) could provide important support to approach this problem in a non-destructive way. In this research, we study the influence of moisture damage on GPR signals at different floor constructions. For this purpose, a modular specimen with interchangeable layers is developed to vary the screed and insulation material, as well as the respective layer thickness. The obtained data set is then used to investigate suitable signal features to classify three scenarios: dry, damaged insulation, and damaged screed. It was found that analyzing statistical distributions of A-scan features inside one B-scan allows for accurate classification on unknown floor constructions. Combining the features with multivariate data analysis and machine learning was the key to achieve satisfying results. The developed method provides a basis for upcoming validations on real damage cases.
Functional nanomaterials (NM) of different size, shape, chemical composition, and surface chemistry are of increasing relevance for many key technologies of the twenty-first century. This includes polymer and silica or silica-coated nanoparticles (NP) with covalently bound surface groups, semiconductor quantum dots (QD), metal and metal oxide NP, and lanthanide-based NP with coordinatively or electrostatically bound ligands, as well as surface-coated nanostructures like micellar encapsulated NP. The surface chemistry can significantly affect the physicochemical properties of NM, their charge, their processability and performance, as well as their impact on human health and the environment. Thus, analytical methods for the characterization of NM surface chemistry regarding chemical identification, quantification, and accessibility of functional groups (FG) and surface ligands bearing such FG are of increasing importance for quality control of NM synthesis up to nanosafety. Here, we provide an overview of analytical methods for FG analysis and quantification with special emphasis on bioanalytically relevant FG broadly utilized for the covalent attachment of biomolecules like proteins, peptides, and oligonucleotides and address methodand material-related challenges and limitations. Analytical techniques reviewed include electrochemical titration methods, optical assays, nuclear magnetic resonance and vibrational spectroscopy, as well as X-ray based and thermal analysis methods, covering the last 5–10 years. Criteria for method classification and evaluation include the need for a signal-generating label, provision of either the total or derivatizable number of FG, need for expensive instrumentation, and suitability for process and production control during NM synthesis and functionalization.
MACC1 is a prognostic and predictive metastasis biomarker for more than 20 solid Cancer entities. However, its role in cancer metabolism is not sufficiently explored. Here, we report on how MACC1 impacts the use of glucose, glutamine, lactate, pyruvate and fatty acids and show the comprehensive analysis of MACC1-driven metabolic networks. We analyzed concentrationdependent changes in nutrient use, nutrient depletion, metabolic tracing employing 13C-labeled substrates, and in vivo studies. We found that MACC1 permits numerous effects on cancer
metabolism. Most of those effects increased nutrient uptake. Furthermore, MACC1 alters metabolic pathways by affecting metabolite production or turnover from metabolic substrates. MACC1 supports use of glucose, glutamine and pyruvate via their increased depletion or altered distribution within metabolic pathways. In summary, we demonstrate that MACC1 is an important regulator of metabolism in cancer cells.
Background: Prevention of metastatic invasion is one of the main challenges in the treatment of alveolar rhabdomyosarcoma. Still the therapeutic options are limited. Therefore, an anti-tumor screening was initiated focusing on the anti-metastatic and anti-invasion properties of selected medicinal plant extracts and phytoestrogens, already known to be effective in the prevention and treatment of different cancer entities.
Methods: Treatment effects were first evaluated by cell viability, migration, invasion, and colony forming assays on the alveolar rhabdomyosarcoma cell line RH-30 in comparison with healthy primary cells.
Results: Initial anti-tumor screenings of all substances analyzed in this study, identified the plant extract of Vincetoxicum arnottianum (VSM) as the most promising candidate, harboring the highest anti-metastatic potential. Those significant anti-motility properties were proven by a reduced ability for migration (60%), invasion (99%) and colony formation (61%) under 48 h exposure to 25 μg/ml VSM. The restricted motility features were due to an induction of the stabilization of the cytoskeleton – actin fibers were 2.5-fold longer and were spanning the entire cell. Decreased proliferation (PCNA, AMT, GCSH) and altered metastasis (e. g. SGPL1, CXCR4, stathmin) marker expression on transcript and protein level confirmed the significant lowered tumorigenicity under VSM treatment. Finally, significant alterations in the cell metabolism were detected for
25 metabolites, with levels of uracil, N-acetyl serine and propanoyl phosphate harboring the greatest alterations. Compared to the conventional therapy with cisplatin, VSM treated cells demonstrated a similar metabolic shutdown of the primary cell metabolism. Primary control cells were not affected by the VSM treatment.
Conclusions: This study revealed the VSM root extract as a potential, new migrastatic drug candidate for the putative treatment of pediatric alveolar rhabdomyosarcoma with actin filament stabilizing properties and accompanied by a marginal effect on the vitality of primary cells.
Lipid droplets, the dynamic organelles that store Triglycerides (TG) and cholesterol esters (CE), are highly accumulated in colon cancer cells. This work studies the TG and CE subspecies profile in colon carcinoma cell lines, SW480 derived from primary tumor, and SW620 derived from a metastasis of the same tumor. It was previously reported that the total TG and CE content is dramatically higher in SW620 cells; however, TG and CE subspecies profile has not been investigated in detail. The work presented here confirms that the total TG and CE Content is significantly higher in the SW620 cells. Moreover, the fatty acid (FA) composition of TG is significantly altered in the SW620 cells, with significant decrease in the abundance of saturated triglycerides. This resulted in a significantly decreased TG saturation index in the SW620 cells. The saturation index of CE was also significantly decreased in the SW620 cells.
Self-assembled monolayers (SAMs) on plasmonic substrates play a significant role applications of surface-enhanced Raman scattering (SERS). At the same time, localized surface plasmon resonances (LSPRs) can be employed for a broad range of plasmon-supported chemical modifications. Here, micropatterning using the derivatization of SAMs on gold nanosubstrates for rewritable SERS-based security labels or as the basis for sensing arrays functionalized with biomolecules is demonstrated using different plasmon-catalyzed reactions. The formation of 4,4′-dimercaptoazobenzene (DMAB) from p-aminothiophenol (PATP) as well as from p-nitrothiophenol (PNTP) and the reduction of PNTP to PATP are used to change the functionality of the substrate in specified positions. Employing LSPR, the reactions are started by illumination using visible laser light at a high intensity in a focal spot of a microscope objective and yield microscopic patterns of the reaction product. The obtained molecular patterns can be erased by other reactions, enabling different strategies for rewriting, encryption, or stepwise functionalization.
Laser metal deposition is a rapidly evolving method for additive manufacturing that combines high performance and simplified production routine. Quality of production depends on instrumental design and operational parameters that require constant control during the process. In this work, feasibility of using optical spectroscopy as a control method is studied via modeling and experimentally. A simplified thermal model is developed based on the time-dependent diffusion-conduction heat equation and geometrical light collection into detection optics. Intense light emitted by a laser-heated spot moving across a sample surface is collected and processed to yield the temperature and other temperature-related parameters. In a presence of surface defects the temperature field is distorted in a specific manner that depends on a shape and size of the defect. Optical signals produced by such the distorted temperature fields are simulated and verified experimentally using a 3D metal printer and a sample with artificially carved defects. Three quantities are tested as possible metrics for process monitoring: temperature, integral intensity, and correlation coefficient. The shapes of the simulated signals qualitatively agree with the experimental signals; this allows a cautious inference that optical spectroscopy is capable of detecting a defect and, possibly, predicting its character, e.g. inner or protruding.
Machine learning predictions of surface migration barriers in nucleation and non-equilibrium growth
(2021)
Machine learning is playing an increasing role in the discovery of new materials and may also facilitate the search for optimum growth conditions for crystals and thin films. Here, we perform kinetic Monte-Carlo simulations of sub-monolayer growth. We consider a generic homoepitaxial growth scenario that covers a wide range of conditions with different diffusion barriers (0.4–0.55 eV) and lateral binding energies (0.1–0.4 eV). These simulations are used as a training data set for a convolutional neural network that can predict diffusion barriers and binding energies. Specifically, a single Monte-Carlo image of the morphology is sufficient to determine the energy barriers with an accuracy of approximately 10 meV and the neural network is tolerant to images with noise and lower than atomic-scale resolution. We believe this new machine learning method will be useful for fundamental studies of growth kinetics and growth optimization through better knowledge of microscopic parameters.
The therapeutic dose of lithium (Li) compounds, which are widely used for the treatment of psychiatric and hematologic disorders, is close to its toxic level; therefore, drug monitoring protocols are mandatory. Herein, we propose a fast, simple, and low-cost analytical procedure for the traceable determination of Li concentration in human serum, based on the monitoring of the Li isotope dilution through the partially resolved isotope shift in its electronic transition around 670.80 nm using a commercially available high-resolution continuum source graphite furnace atomic absorption spectrometer. With this technique, serum samples only require acidic digestion before analysis. The procedure requires three measurements—an enriched 6Li spike, a mixture of a certified standard solution and spike, and a mixture of the sample and spike with a nominal 7Li/6Li ratio of 0.82. Lanthanum has been used as an internal spectral standard for wavelength correction. The spectra are described as the linear superposition of the contributions of the respective isotopes, each consisting of a spin-orbit doublet, which can be expressed as Gaussian components with constant spectral position and width and different relative intensity, reflecting the isotope ratio in the sample. Both the spectral constants and the correlation between isotope ratio and relative band intensity have been experimentally obtained using commercially available materials enriched with Li isotopes. The Li characteristic mass (mc) obtained corresponds to 0.6 pg. The procedure has been validated using five human serum certified reference materials. The results are metrologically comparable and compatible to the certified values. The measurement uncertainties are comparable to those obtained by the more complex and expensive technique, isotope dilution mass spectrometry.
Assembly of permanently porous metal–organic polyhedra/cages (MOPs) with bifunctional linkers leads to soft supramolecular networks featuring both porosity and processability. However, the amorphous nature of such soft materials complicates their characterization and thus limits rational structural control. Here we demonstrate that aging is an effective strategy to control the hierarchical network of supramolecular gels, which are assembled from organic ligands as linkers and MOPs as junctions. Normally, the initial gel formation by rapid gelation leads to a kinetically trapped structure with low controllability. Through a controlled post-synthetic aging process, we show that it is possible to tune the network of the linked MOP gel over multiple length scales. This process allows control on the molecular-scale rearrangement of interlinking MOPs, mesoscale fusion of colloidal particles and macroscale densification of the whole colloidal network. In this work we elucidate the relationships between the gel properties, such as porosity and rheology, and their hierarchical structures, which suggest that porosity measurement of the dried gels can be used as a powerful tool to characterize the microscale structural transition of their corresponding gels. This aging strategy can be applied in other supramolecular polymer systems particularly containing kinetically controlled structures and shows an opportunity to engineer the structure and the permanent porosity of amorphous materials for further applications.
Zeolitic imidazolate framework (ZIF) hybrid fluorescent nanoparticles and ZIF antibody conjugates have been synthesized, characterized, and employed in lateral-flow immunoassay (LFIA). The bright fluorescence of the conjugates and the possibility to tailor their mobility gives a huge potential for diagnostic assays. An enzyme-linked immunosorbent assay (ELISA) with horseradish peroxidase (HRP) as label, proved the integrity, stability, and dispersibility of the antibody conjugates, LC-MS/MS provided evidence that a covalent link was established between these metal-organic frameworks and lysine residues in IgG antibodies.
Zearalenone (ZEN), an estrogenic mycotoxin produced by several species of Fusarium fungi, is a common contaminant of cereal-based food worldwide. Due to frequent occurrences associated with high levels of ZEN, maize oil is a particular source of exposure. Although a European maximumlevel for ZEN in maize oil exists according to Commission Regulation (EC) No. 1126/2007 along with a newly developed international standard method for analysis, certified reference materials (CRM) are still not available. To overcome this lack, the first CRM for the determination of ZEN in contaminated maize germ oil (ERM®-BC715) was developed in the frame of a European Reference Materials (ERM®) project according to the requirements of ISO Guide 35. The whole process of CRM development including preparation, homogeneity and stability studies, and value assignment is presented. The assignment of the certified mass fraction was based upon an in-house study using high-performance liquid chromatography isotope dilution tandem mass spectrometry. Simultaneously, to support the in-house certification study, an interlaboratory comparison study was conducted with 13 expert laboratories using different analytical methods. The certified mass fraction and expanded uncertainty (k=2) of ERM®-BC715 (362± 22) μg kg−1 ZEN are traceable to the SI. This reference material is intended for analytical quality control and contributes to the improvement of consumer protection and food safety.
A method, based on electrothermal vaporization (ETV) coupled to inductively coupled plasma optical emission spectrometry (ICP OES), has been optimized for direct solid sampling analysis of soda-lime glass - the most common type of industrially manufactured glass. This method allows fast and reliable quantification of the main elements - Al, Ca, K, Mg, Na, and Si - and trace elements - As, Ba, Cd, Ce, Co, Cr, Cu, Fe, Mn, Mo, Ni, (P), Pb, Sb, (Se), Sn, Sr, Ti, V, Zn, and Zr. In the presented ETV-ICP OES method, calibration is performed predominantly with matrix-free synthetic samples. This metrological advantage is normally not achieved with direct solid sampling methods and is one of the goals of the present study. In a certification interlaboratory comparison for the soda-lime glass CRM BAM-S005c, 2 out of 16 laboratories employed the ETV-ICP OES method. An improved analytical performance was obtained compared with the results of laboratories that used conventional liquid ICP OES. For both methods, the average relative deviations between the laboratory results and certified values as well as the average values of relative standard deviation were with a few exceptions <10%, in most cases even <5%, which indicated high trueness and precision.
This data article presents characteristic acoustic and flow data of a fluidic ultrasonic transducer as well as acoustic data of a commercial piezoelectric ultrasonic transducer used in non-destructive testing for civil engineering. The flow data has been acquired using hot-wire anemometry and a Pitot tube. The three-dimensional acoustic data of both devices has been acquired using a calibrated microphone. The distribution of characteristic acoustic properties of both transducers are extracted and given in addition to the raw data. The data presented in the article will be a valuable source for reference and validation, both for developing fluidic and alternate ultrasound generation technologies. Furthermore, they will give additional insight into the acoustic-flow interaction phenomena of high speed switching devices. This article is accompanying the paper Experimental Analysis of the Acoustic Field of an Ultrasonic Pulse Induced by a Fluidic Switch (Bühling et al., 2021) published in The Journal of the Acoustical Society of America, where the data is interpreted in detail and the rationale for characteristic sound properties of the fluidic transducer are given.
A particle roughness analysis tool, based on electron microscopy images (SEM and TEM). The influence of various parameters on the calculated roughness was also investigated: the setting of the proper threshold, accelerating voltage, etc. The samples were gradually tilted to extend imaging information of more than only one projection. Furthermore, the measurement uncertainty of the profile roughness of particles associated to various orientations was estimated.
X-ray absorption spectroscopy (XAS), in its various modalities, has gained exponential attention and applicability in the field of biological and biomedical systems. Particularly in this field, challenges like low concentration of analyte or proneness to radiation damage have certainly settle the basis for further analytical developments, when using X-ray based methods. Low concentration calls for higher sensitivity—by increasing the detection limits (DL); while susceptibility for radiation damage requires shorter measurement times and/or cryogenic sample environment possibilities. This manuscript reviews the latest analytical possibilities that make XAS more and more adequate to investigate biological or biomedical systems in the last 5 years.
The concept of aggregation-induced emission represents a means to rationalise photoluminescence of usually nonfluorescent excimers in solid-state materials. In this publication, we study the photophysical properties of selected diaminodicyanoquinone (DADQ) derivatives in the solid state using a combined approach of experiment and theory. DADQs are a class of high-dipole organic chromophores promising for applications in non-linear optics and light-harvesting devices. Among the compounds investigated, we find both aggregation-induced emission and aggregation-caused quenching effects rationalised by calculated energy transfer rates. Analysis of fluorescence spectra and lifetime measurements provide the interesting result that (at least) two emissive species seem to contribute to the photophysical properties of DADQs. The main emission peak is notably broadened in the long-wavelength limit and exhibits a blue-shifted shoulder. We employ high-level quantum-chemical methods to validate a molecular approach to a solid-state problem and show that the complex emission features of DADQs can be attributed to a combination of H-type aggregates, monomers, and crystal structure defects.
The reconstruction of cone-beam computed tomography data using filtered back-projection algorithms unavoidably results in severe artefacts. We describe how the Direct Iterative Reconstruction of Computed Tomography Trajectories (DIRECTT) algorithm can be combined with a model of the artefacts for the reconstruction of such data. The implementation of DIRECTT results in reconstructed volumes of superior quality compared to the conventional algorithms.
Despite the growing dependence of companies on information technology and the increasingly negative impact of security incidents worldwide, there is little research on the management of information security at the company level. This paper seeks to expand knowledge on the implementation of an information security management system based on the widely used international standard ISO/IEC 27001. We present motives, experienced impacts, and obstacles related to ISO/IEC 27001 implementation using data from a survey of 125 ISO/IEC 27001 certified companies in Germany. Since adoption rates vary between ICT and non-ICT sector companies, we highlight sector-related variations. We classify the adoption of this standard as a preventive organizational innovation and apply Structural Equation Modeling to unearth explanations for the comparatively low adoption of this management system standard among companies outside the ICT sector. We, therefore, derive recommendations for policymakers, standardization, and certification bodies to foster its diffusion.
While X-ray based darkfield imaging with grating interferometers is already widely used, darkfield imaging with neutrons has still a relatively small user community focused mostly on magnetic materials. Here, we demonstrate the application of neutron darkfield imaging byTalbot-Lau type grating interferometry to fiber reinforced plastics. Common carbon and glass fiber composites have been investigated including characteristic damage structures. The darkfield images show a strong signal response caused by fiber delamination, suitable fiber direction, particles, pores and cracks. The basic principles of neutron darkfield imaging applied to fiber composites are highlighted.
A core component of energy storage systems like vanadium redox flow batteries (VRFB) is the polymer electrolyte membrane (PEM). In this work, the frequently used perfluorosulfonic-acid (PFSA) membrane Nafion™ 117 and a novel poly (vinylidene difluoride) (PVDF)-based Membrane are investigated. A well-known problem in VRFBs is the vanadium permeation through the membrane. The consequence of this so-called vanadium crossover is a severe loss of capacity. For a
better understanding of vanadium transport in membranes, the uptake of vanadium ions from electrolytes containing Vdimer(IV–V) and for comparison also V(II), V(III), V(IV), and V(V) by both membranes was studied. UV/VIS spectroscopy, X-ray absorption near edge structure spectroscopy (XANES), total reflection X-ray fluorescence spectroscopy (TXRF), inductively coupled plasma optical emission spectrometry (ICP-OES), and micro X-ray fluorescence spectroscopy (microXRF) were used to determine the vanadium concentrations and the species inside the membrane. The results strongly support that Vdimer(IV–V), a dimer formed from V(IV) and V(V), enters the nanoscopic water-body of Nafion™ 117 as such. This is interesting, because as of now, only the individual ions V(IV) and V(V) were considered to be transported through the membrane. Additionally, it was found that the Vdimer(IV–V) dimer partly dissociates to the individual ions in the novel PVDF-based membrane.
The Vdimer(IV–V) dimer concentration in Nafion™ was determined and compared to those of the other species. After three days of equilibration time, the concentration of the dimer is the lowest compared to the monomeric vanadium species. The concentration of vanadium in terms of the relative uptake λ = n(V)/n(SO3
) are as follows: V(II) [λ = 0.155] > V(III) [λ = 0.137] > V(IV) [λ = 0.124] > V(V) [λ = 0.053] > Vdimer(IV–V) [λ = 0.039]. The results show that the Vdimer(IV–V) dimer Needs to be considered in addition to the other monomeric species to properly describe the transport of vanadium through Nafion™ in VRFBs.
A modern day light microscope has evolved from a tool devoted to making primarily empirical observations to what is now a sophisticated, quantitative device that is an integral part of both physical and life science research. Nowadays, microscopes are found in nearly every experimental laboratory. However, despite their prevalent use in capturing and quantifying scientific phenomena, neither a thorough understanding of the principles underlying quantitative imaging techniques nor appropriate knowledge of how to calibrate, operate and maintain microscopes can be taken for granted. This is clearly demonstrated by the well-documented and widespread difficulties that are routinely encountered in evaluating acquired data and reproducing scientific experiments. Indeed, studies have shown that more than 70% of researchers have tried and failed to repeat another scientist’s experiments, while more than half have even failed to reproduce their own experiments1. One factor behind the reproducibility crisis of experiments published in scientific journals is the frequent underreporting of imaging methods caused by a lack of awareness and/or a lack of knowledge of the applied technique2,3. Whereas quality control procedures for some methods used in biomedical research, such as genomics (e.g., DNA sequencing, RNA-seq) or cytometry, have been introduced (e.g. ENCODE4), this issue has not been tackled for optical microscopy instrumentation and images. Although many calibration standards and protocols have been published, there is a lack of awareness and agreement on common Standards and guidelines for quality assessment and reproducibility5.
In April 2020, the QUality Assessment and REProducibility for instruments and images in Light Microscopy (QUAREP-LiMi) initiative6 was formed. This initiative comprises imaging scientists from academia and industry who share a common interest in achieving a better understanding of the performance and limitations of microscopes and improved quality control (QC) in light microscopy. The ultimate goal of the QUAREP-LiMi initiative is to establish a set of common QC standards, guidelines, metadata models7,8, and tools9,10, including detailed protocols, with the ultimate aim of improving reproducible advances in scientific research.
This White Paper 1) summarizes the major obstacles identified in the field that motivated the launch of the QUAREP-LiMi initiative; 2) identifies the urgent need to address these obstacles in a grassroots manner, through a community of Stakeholders including, researchers, imaging scientists11, bioimage analysts, bioimage informatics developers, corporate partners, Funding agencies, standards organizations, scientific publishers, and observers of such; 3) outlines the current actions of the QUAREPLiMi initiative, and 4) proposes future steps that can be taken to improve the dissemination and acceptance of the proposed guidelines to manage QC.
To summarize, the principal goal of the QUAREP-LiMi initiative is to improve the overall quality and reproducibility of light microscope image data by introducing broadly accepted standard practices and accurately captured image data metrics.
We present the synthesis and characterization of a family of regioisomerically pure pH-sensitive rosamine fluorophores consisting of xanthene fluorophore cores, which determine the dyes’ photophysical properties such as excitation/emission wavelength, fluorescence quantum yield, and fluorescence lifetime, and differently substituted phenol moieties. The hydroxyl substituent of the phenol moiety introduces a pH sensitivity of the dyes’ fluorescence exploiting a photoinduced electron transfer (PET), that leads to a protonation-induced switching ON of the rosamine emission. Rational tuning of the pKa value of the rosamine fluorescence between 4 to 9 is achieved by altering the substitution pattern and degree of bromination of the phenolic subunits. Additionally, a temperature sensitivity of the fluorescence quantum yield is introduced or suppressed based upon the degree of rigidity of the xanthene scaffold.
We present the rational design, synthesis and spectroscopic characterization of a novel dual excitation, three color emitting, pH-responsive fluorescent probe consisting of two phenanthrene and one rhodamine B units linked by click chemistry. The rhodamine moiety, excitable at λEx = 315 nm and at λEx = 560 nm in its ring-opened form, provides the pH-responsive fluorophore, while the pH-insensitive phenanthrene, excited at λEx = 315 nm, serves as inert internal reference, The presence of two phenanthrene moieties enables a blue monomer and a blueish green excimer emission at 351 nm and 500 nm, respectively. Opening of the rhodamine B spirolactam ring at an acidic pH below 5.0 (pKa = 2.59 ± 0.04) switches on its emission at 580 nm. Simultaneously, the phenanthrene excimer emission decreases caused by a change in orientation of the phenanthrene units, while the monomer emission is barely affected. This sensor design enables ratiometric measurements in the low acidic pH range utilizing the intensity ratios of the rhodamine B and phenanthrene excimer emission at 580 nm and 500 nm. Alternatively, also the intensity ratios of the rhodamine B and the phenanthrene monomer emission could be exploited or the sum of the phenanthrene monomer and excimer fluorescence. To the best of our knowledge, this is the first report of ratiometric sensing utilizing such a versatile type of tricolor emissive dyad probe bearing phenanthrene moieties and showing phenanthrene monomer and excimer emission.
Gaining chemical control over the thermodynamics and kinetics of photoexcited states is paramount to an efficient and sustainable utilization of photoactive transition metal complexes in a plethora of technologies. In contrast to energies of charge Transfer states described by spatially separated orbitals, the energies of spinflip states cannot straightforwardly be predicted as Pauli Repulsion and the nephelauxetic effect play key roles. Guided by multireference quantum chemical calculations, we report a novel highly luminescent spin-flip emitter with a quantum chemically predicted blue-shifted luminescence. The spin-flip emission band of the chromium complex [Cr(bpmp)2]3+ (bpmp = 2,6-bis(2-pyridylmethyl) pyridine) shifted to higher energy from ca. 780 nm observed for known highly emissive chromium(III) complexes to 709 nm. The photoluminescence quantum yields climb to 20%, and very long excited state lifetimes in the millisecond range are achieved at room temperature in acidic D2O solution. Partial ligand deuteration increases the quantum yield to 25%. The high excited state energy of [Cr(bpmp)2]3+ and its facile reduction to [Cr(bpmp)2]2+ result in a high excited state redox potential. The ligand’s methylene bridge acts as a Brønsted acid quenching the luminescence at high pH. Combined with a pH-insensitive chromium(III) emitter, ratiometric optical pH sensing is achieved with single wavelength excitation. The photophysical and Ground state properties (quantum yield, lifetime, redox potential, and acid/base) of this spin-flip complex incorporating an earth-abundant metal surpass those of the classical precious metal [Ru(α-diimine)3]2+ charge transfer complexes, which are commonly employed in optical sensing and photo(redox) catalysis, underlining the bright future of these molecular ruby analogues.
Electrochemical methods offer great promise in meeting the demand for user-friendly on-site devices for Monitoring important parameters. The food industry often runs own lab procedures, for example, for mycotoxin analysis, but it is a major goal to simplify analysis, linking analytical methods with smart technologies. Enzyme-linked immunosorbent assays, with photometric detection of 3,3’,5,5’-tetramethylbenzidine (TMB),form a good basis for sensitive detection. To provide a straightforward approach for the miniaturization of the detectionstep, we have studied the pitfalls of the electrochemical TMB detection. By cyclic voltammetry it was found that the TMB electrochemistry is strongly dependent on the pH and the electrode material. A stable electrode response to TMB could be achieved at pH 1 on gold electrodes. We created a smartphonebased, electrochemical, immunomagnetic assay for the detection of ochratoxin A in real samples, providing a solid basis forsensing of further analytes.
The composition of the surface layer in dependence from the distance of the polymer/air interface in thin films with thicknesses below 100 nm of miscible polymer blends in a spatial region of a few nanometers is not investigated completely. Here, thin films of the blend poly vinyl methyl ether) (PVME)/polystyrene (PS) with a composition of 25/75 wt% are investigated by Energy Resolved X-ray Photoelectron Spectroscopy (ER-XPS) at a synchrotron storage ring using excitation energies lower than 1 keV. By changing the energy of the photons the information depth is varied in the range from ca. 1 nm to 10 nm. Therefore, the PVME concentration could be estimated in dependence from the distance of the polymer/air interface for film thicknesses below 100 nm. Firstly, as expected for increasing information depth the PVME concentration decreases. Secondly, it was found that the PVME concentration at the surface has a complicated dependence on the film thickness. It increases with decreasing film thickness until 30 nm where a maximum is reached. For smaller film thicknesses the PVME concentration decreases. A simplified layer model is used to calculate the effective PVME concentration in the different spatial regions of the surface layer.
An alternative method for lithium isotope amount ratio analysis based on a combination of high-resolution atomic absorption spectrometry and spectral data analysis by machine learning (ML) is proposed herein. It is based on the well-known isotope shift of approximately 15 pm for the electronic transition 22P←22S at around the wavelength of 670.8 nm, which can be measured by the state-of-the-art high-resolution continuum source graphite furnace atomic absorption spectrometry. For isotope amount ratio analysis, a scalable tree boosting ML algorithm (XGBoost) was employed and calibrated using a set of samples with 6Li isotope amount fractions, ranging from 0.06 to 0.99 mol mol–1, previously determined by a multicollector inductively coupled plasma mass spectrometer (MC-ICP-MS). The calibration ML model was validated with two certified reference materials (LSVEC and IRMM-016). The procedure was applied toward the isotope amount ratio determination of a set of stock chemicals (Li2CO3, LiNO3, LiCl, and LiOH) and a BAM candidate reference material NMC111 (LiNi1/3Mn1/3Co1/3O2), a Li-battery cathode material. The results of these determinations were compared with those obtained by MC-ICP-MS and found to be metrologically comparable and compatible. The residual bias was −1.8‰, and the precision obtained ranged from 1.9 to 6.2‰. This precision was sufficient to resolve naturally occurring variations, as demonstrated for samples ranging from approximately −3 to +15‰. To assess its suitability to technical applications, the NMC111 cathode candidate reference material was analyzed using high-resolution continuum source atomic absorption spectrometry with and without matrix purification. The results obtained were metrologically compatible with each other.