Analytische Chemie
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Additive Manufacturing provides an important enabling technology for the digital transformation of the economy. As an emerging technology it has seen a remarkable development over the last three decades. Nevertheless, it is far from a broad adoption with several barriers to overcome yet. One of the major challenges is the lack of standards. The critical role of standardization for innovation is generally recognized, still the topic too often has been neglected in strategic roadmapping exercises for emerging technologies. Too little is known about the complex dynamics and interrelations of standardization and innovation. The anticipation of standardization needs and the timely and efficient implementation of standards is challenging. This paper aims at contributing to a better understanding of the role that standards play in the multi-dimensional system of innovation. It analyzes the trajectories of innovation in Additive Manufacturing in a systematic and holistic way, focusing on standardization activities with regard to coordination, stakeholders involved, the timing and types of standards developed. Putting standardization in context of the multi-dimensional innovation system of Additive Manufacturing the research shows where standards can support the diffusion of an emerging technology.
Leaking methane (CH4) from infrastructures, such as pipelines and landfills, is critical for the environment but can also pose a safety risk. To enable a fast detection and localization of these kind of leaks, we developed a novel robotic platform for aerial remote gas sensing. Spectroscopic measurement methods for remote sensing of selected gases lend themselves for use on mini-copters, which offer a number of advantages for inspection and surveillance over traditional methods. No direct contact with the target gas is needed and thus the influence of the aerial platform on the measured gas plume can be kept to a minimum. This allows to overcome one of the major issues with gas-sensitive mini-copters. On the other hand, remote gas sensors, most prominently Tunable Diode Laser Absorption Spectroscopy (TDLAS) sensors have been too bulky given the payload and energy restrictions of mini-copters. Here, we present the Unmanned Aerial Vehicle for Remote Gas Sensing (UAV-REGAS), which combines a novel lightweight TDLAS sensor with a 3-axis aerial stabilization gimbal for aiming on a versatile hexacopter. The proposed system can be deployed in scenarios that cannot be addressed by currently available robots and thus constitutes a significant step forward for the field of Mobile Robot Olfaction (MRO). It enables tomographic reconstruction of gas plumes and a localization of gas sources. We also present first results showing its performance under realistic conditions.
Bacterial biofilms represent a ubiquitous form of microbial life on Earth. Due to an evolved armory of protean biological responses to external stimuli, bacteria are able to adhere to, colonize and thrive on virtually all surfaces, whether natural or synthetic, even in challenging environmental conditions. In addition to significant health risks, biofilms are among the salient contributors to the deterioration of metals and their alloys, thereby causing safety risks for technical equipment. Hence, understanding the interaction mechanisms of electroactive sessile bacteria with metal surfaces is vital for facilitating the development of efficient control strategies and novel anti-fouling surfaces in various industries and technologies.
The present study focusses on a combined spectroelectrochemical approach, melding methods of surface enhanced Raman spectroscopy (SERS) and electrochemical techniques, to investigate the chemical characteristics and redox activities of electroactive bacteria during the initial stages of biofilm formation. Gold has been selected as a model substrate due to its inert character, considerably high surface enhancement factor, as well as its capability to allow surface chemistry modifications and substrate polarization in order to precisely control the surface charge. Square wave voltammetry (SWV) and cyclic voltammetry (CV) studies have been performed for quantitative determination of flavin concentration and electrochemical impedance spectroscopy (EIS) has been utilized to study the changes in electrochemical processes within biofilms during different stages of growth. Shewanella sp. have been chosen as microorganisms within this work due to their versatile exoelectrogenic respiratory behavior and their distinct ability to reduce metals via extracellular electron transfer mechanisms involving self-secreted electron shuttle redox molecules such as flavins. To further explicate the process of diffusion of flavins within biofilms, a model system has been developed to simulate the structural features of the bacterial extracellular polymeric substances typically found in biofilms. This has been achieved by creating hydrogel films comprised of calcium-cross-linked alginate. The results demonstrate an interplay of factors contributing to the initial phases of bacterial settlement and biofilm formation as a function of environmental parameters. Furthermore, the results allow insight into the diffusion of flavins, much like they would in a natural biofilm, and how their redox behavior affects the biofilm development.
Capillary electrophoresis (CE) is an analytical technique that
separates analytes based on their electrophoretic mobility with
the use of an applied voltage.
Nanoparticles separation using CE exhibits good separation and
analysis efficiency, especially for nanoparticles smaller than 30
nm. The coupling of CE with inductively coupled plasma mass
spectrometry (ICP-MS) provides the possibility to detect
nanoparticles in the concentration range of nanograms per litre
and enables the simultaneous detection of nanoparticles and its
[1][2] ionic counter parts.
Our objective is to develop a fast and reliable separation method
for differently modified nanoparticles using capillary
electrophoresis.
Inhibition of Herpes Virus by Specific and Non-specific Interactions With Graphene Conjugates
(2017)
Herpes viruses (HSV) are global, host-adapted pathogens that cause a widespread diversity of diseases. The frequency of HSV infections all over the world has amplified over the last years, making it a major concern in the area of public health. Therefore, synthesis of systems that can inhibit development of these viruses is required. Various compounds already have shown inhibition of HSV, but concentration of these inhibitors is relatively high and resistance against those drugs is challenging.
Combination of biological knowledge, about structure of the active site on the surface of HSV that is responsible for inhibition of the pathogen, with the chemistry of graphene results in 2D systems with the ability of specific and nonspecific interactions with HSV. In this work, 2D nanomaterials with picomolar IC50 against HSV are synthesized by conjugation of peptides to the surface of graphene.
2D nanomaterials are characterized by various methods, including XPS, AFM and IR. Biological evaluation showed high potency of synthesized nanomaterials to inhibit HSV and therefore underlined possibility to use such materials in future biomedical applications.
Graphene and its derivatives have recently attracted much attention for sensing and deactivating pathogens. However, mechanism of multivalent interactions at the graphene-pathogen interface are not fully understood. Since different physicochemical parameters of graphene play a role at this interface, control over graphene’s structure is necessary to study the mechanism of these interactions. In this work, zwitterionic graphene nanomaterials (ZGNMs) were synthesized with defined isoelectric points and exposure, in terms of polymer coverage and functionality. Then, the switchable interactions of ZGNMs with E. coli were investigated to study the validity of the generally proposed “trapping” mechanism for inactivating pathogens by functionalized graphene derivatives. The ZGNMs were able to controllably trap and release E. coli by crossing their isoelectric points.
Metal organic frameworks and coordination polymers play an important role in different fields of applications. Moreover, particularly fluorinated metal-organic frameworks (FMOFs) are in the focus of interest during the last years. In most cases, fluorine is implemented using perfluorinated organic linkers at the synthesis, usually performed by solvothermal synthesis. However, only few examples are known so far where fluorine is coordinated directly to the metal cation. Recently, we reported about mechanochemical syntheses and characterization of fluorine-containing coordination polymers of alkaline earth metals by milling M(OH) (M: Ca, Sr, Ba) with fluorinated benzene dicarboxylic acids 2 and we reported about mechanochemical syntheses of alkaline earth metal fluorides with ammonium fluoride. Now we are reporting about a combination of both synthesis routes. That is the first mechanochemical synthesis of coordination polymers where fluorine is coordinated directly to the metal cation.
The Cairo Geniza is an “archive” discovered in the 19th century in Ben Ezra Synagogue in Fustat, a district in Old Cairo (Egypt), located south of the center of modern Cairo. The giant collection of mostly Jewish documents that vary in genres, languages and writing supports contains a large number of early medieval Hebrew manuscripts, mostly in fragmentary form. The larger part of the Cairo Geniza is stored today in the Cambridge University Library.
The Geniza provides sources for the literary, linguistic, historical studies of the various aspects Jewish life. As the documents attest, at least two Jewish communities co-existed in Fustat up to 11th century: a so-called Babylonian and Palestinian. These communities had different leaders, different traditions and lived independently. The differences seem to manifest themselves also in the paleographical, codicological and some material properties of the manuscripts produced by each community.
My work addresses the ink composition in the documents attributed to the members of these communities. For the determination of the inks type and composition I employ reflectography and µ-XRF spectrometry, respectively. The preliminary typological studies indicate that iron-gall inks were found predominantly in the manuscripts attributed to the Palestinian community.
Accurate measurements of stable isotope abundance ratio variations are often reported using artifact based delta-scales, which rely on suitable isotopic reference materials (iRM) for their realization. For example, variations in the 26Mg/24Mg isotope abundance ratio in natural systems are typically reported as delta26Mg values that represents the relative difference between the 26Mg/24Mg ratio measured in a sample relative to its measurement preferably in an iRM. In the past, such delta26Mg measurements were referenced to NIST SRM 980, the initial zero of the delta26Mg scale. With the development of MC-ICPMS, the detection of small but measurable isotopic differences in different chips of SRM 980 became apparent. It was then replaced by a Mg solution (DSM3), the new zero of the delta26Mg scale. A potential replacement iRM for DSM3 has been developed, ERM-AE143. This iRM has also been measured for its absolute isotope amount ratios1,2 making it traceable to the SI.
The results of an delta26Mg intercomparison experiment include the Mg iRMs SRM 980, IRMM-009, ERM-AE143, AE144, AE145 standards DSM3 and Cambridge-1. The intercomparison involved 5 expert laboratories, consisting of 3 national metrological institutes (BAM, NIST, PTB) and 2 scientific research laboratories (GFZ Potsdam, UBremen).
The iRMs were measured relative to AE143 and cover a range of ≈5 ‰ in delta26Mg. IRMM-009 has the lowest delta26Mg value while DSM3 has the highest, spanning a range in values that covers natural Mg isotope variations. The 2SD reproducibilities of the individual values from the different laboratories range from 0.02 to 0.26 ‰. The mean delta26Mg values, calculated from the laboratory means however show 2SD reproducibilities varing between 0.025 and 0.093 ‰. Propagated measurement uncertainties suggest a standard uncertainty of about 0.1‰ for delta26Mg determinations.
Hepcidin-25 has attracted much attention ever since its discovery in 2001. It is widely recognized that this liver produced peptide hormone plays a major role in the regulation of iron levels in mammals and can reveal important clinical information about several pathological states in patients suffering from iron-related disorders.
With the aim to tackle the current difficulties in hepcidin quantification and improve the status of this promising biomarker in the clinical field, we developed a rapid and robust analytical strategy for the quantification of hepcidin-25 in human samples based on HPLC-MS/MS (QqQ) to be implemented in routine laboratories. The novelty of the method is the use of special HPLC vials to avoid adsorptive losses due to the basic character of the peptide that causes interaction with the silanol groups of the vial’s glass surface. Up to 90% decrease in the MS/MS signal was observed, when commercial HPLC vials were used, while vials treated with 3-(2-aminoethylamino)propylmethyl-dimethoxysilane or 1H,1H,2H,2H-perfluorooctyltriethoxysilane, leading to no significant losses in the dynamic range of physiological hepcidin-25 mean serum levels (10-20 µg/L).
Careful analytical validation was performed for determining the reproducibility, repeatability, limit of quantification (0.5 µg/L) and linearity (0.5-40 µg/L) of the method. Serum samples from 9 healthy volunteers were analyzed with a median hepcidin-25 level of 3.3 µg/L, comparable to results reported in the literature.