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The usefulness of seven different Tin catalysts, Bismuth subsalicylate and Titan tetra(ethoxide) for the polycondensation of ethyl L-lactate (ELA) was examined at 150 °C/6 d. Dibutyltin bis(phenoxides) proved to be particularly effective. Despite the low reactivity of ELA, weight average molecular masses (Mw) up to 12 500 were found along with partial crystallization. Furthermore, polylactides (PLAs) of similar molecular masses were prepared via ELA-initiated ROPs of L-lactide by means of the four most effective polycondensation catalysts. The crystalline linear PLAs were annealed at 140 or 160 °C in the presence of these catalysts. The consequences of the transesterification reactions in the solid PLAs were studied by means of matrix-assisted laser desorption/ionization (MALDI TOF) mass spectrometry, gel permeation chromatography (GPC) and small-angle X-ray scattering (SAXS). The results indicate that polycondensation and formation of cycles proceed in the solid state via formation of loops on the surface of the crystallites. In summary, five different transesterification reactions are required to explain all results.
The statistical tool eCerto was developed for the evaluation of measurement data to assign property values and associated uncertainties of reference materials. The analysis is based on collaborative studies of expert laboratories and was implemented using the R software environment. Emphasis was put on comparability of eCerto with SoftCRM, a statistical tool based on the certification strategy of the former Community Bureau of Reference. Additionally, special attention was directed towards easy usability from data collection through processing, archiving, and reporting. While the effects of outlier removal can be flexibly explored, eCerto always retains the original data set and any manipulation such as outlier removal is (graphically and tabularly) documented adequately in the report. As a major reference materials producer, the Bundesanstalt für Materialforschung und -prüfung (BAM) developed and will maintain a tool to meet the needs of modern data processing, documentation requirements, and emerging fields of RM activity. The main features of eCerto are discussed using previously certified reference materials.
Calcium sulfate hemihydrate (CaSO4ᐧ0.5H2O), also known as bassanite, has been used as a precursor to produce gypsum (dihydrate, CaSO4ᐧ2H2O) for various construction and decorative purposes since prehistoric times. The main route to obtain hemihydrate is a thermal treatment of gypsum at temperatures typically between 150 °C and 200 °C to remove some of the structural water.
In this contribution, we introduce (Fig. 1) a more efficient and sustainable method (T < 100 °C) that enables the direct, rapid, and reversibly conversion of gypsum to bassanite using reusable high salinity aqueous solutions (brines with c[NaCl] > 4 M). The optimum conditions for the efficientproduction of bassanite in a short time (< 5 min) involve the use of brines with c(NaCl) > 4 M and maintaining a temperature, T > 80 °C. When the solution containing bassanite crystals is cooled down to around room temperature, eventually gypsum is formed. When the temperature is raised again to T > 80 °C, bassanite is rapidly re-precipitated. This contrasts with the typical behaviour of the bassanite phase in low salt environments.
Traditionally, hemihydrate is obtained through a solid state thermal treatment because bassanite is considered to be metastable with respect to gypsum and anhydrite in aqueous solutions, and therefore gypsum-to-bassanite conversion should not occur in water. Its very occurrence actually contradicts numerical thermodynamic predictions regarding solubility of calcium sulfate phases. By following the evolution of crystalline phases with in situ and time-resolved X-ray diffraction/scattering and Raman spectroscopy, we demonstrated that the phase stability in brines at elevated temperatures is inaccurately represented in the thermodynamic databases. Most notably for c(NaCl) > 4 M, and T > 80 °C gypsum becomes readily more soluble than bassanite, which induces the direct precipitation of the latter from gypsum. The fact that these transformations are controlled by the solution provides extensive opportunities for precise manipulation of crystal formation. Our experiments confirmed that bassanite remained the sole crystalline structure for many hours before reverting into gypsum. This property is extremely advantageous for practical processing and efficient crystal extraction in industrial scenarios.
Here, we elucidate nonclassical multistep crystallization pathways of transition metal phosphates from aqueous solutions. We followed precipitation processes of M-struvites, NH4MPO4·6H2O, and M-phosphate octahydrates, M3(PO4)2·8H2O, where M = Ni, Co, or NixCo1–x, by using in situ scattering and spectroscopy-based techniques, supported by elemental mass spectrometry analyses and advanced electron microscopy. Ni and Co phosphates crystallize via intermediate colloidal amorphous nanophases, which change their complex structures while agglomerating, condensing, and densifying throughout the extended reaction times. We reconstructed the three-dimensional morphology of these precursors by employing cryo-electron tomography (cryo-ET). We found that the complex interplay between metastable amorphous colloids and protocrystalline units determines the reaction pathways. Ultimately, the same crystalline structure, such as struvite, is formed. However, the multistep process stages vary in complexity and can last from a few minutes to several hours depending on the selected transition metal(s), their concentration, and the Ni/Co ratio.
Electrocatalysis is and will continue to play a central role in the development of a new and modern sustainable economy, especially for chemicals and fuels. The storage of excess electrical energy into chemical energy by splitting water into hydrogen and oxygen is a feasible solution in this economic sector. A major drawback of electrical energy lies in the storage. Therefore, hydrogen is discussed as promising alternative. Fortunately, this issue can be effectively addressed through the implementation of chemical storage mechanisms. Due to their abundance on Earth and inherent stability in alkaline solutions, transition-metal oxides have become one of several viable alternatives to conventional noble-metal catalysts. Since FeNi oxide is one of the most active oxygen evolution reaction (OER) electrocatalysts for alkaline water electrolysis, it has been the subject of extensive research.
A series of different types of FeNi oxide nanoparticles (NPs) with atomic ratios covering a broad range, and various sizes with specific stoichiometric and non-stoichiometric iron and nickel ratios was synthesized and characterized by the combination of surface analysis techniques, such as time-of-flight secondary ion mass spectrometry (ToF-SIMS) and X-ray photoelectron spectroscopy (XPS). The morphology was studied using scanning electron microscopy (SEM) and transmission electron microscopy (TEM), which revealed the coexistence of mixed and unmixed iron and nickel NPs with comparable sizes in the range of 30–40 nm across all ratios. The synthesis technique displayed control over the iron-nickel ratio, as evidenced by energy dispersive X-ray spectroscopy (EDS) data. The presence of magnetite (Fe3O4) was detected in all samples investigated by X-ray diffraction (XRD). Furthermore, the existence of nickel ferrite (NiFe2O4) was shown in the Fe2Ni by XRD analysis. For the cyclic voltammetry (CV) measurements, the NPs were deposited onto glassy carbon electrodes using Nafion® as an ionomer, and 1 M KOH was employed as the electrolyte. Subsequently, the NPs/Nafion® electrode was transferred into the ToF-SIMS chamber to allow surface analysis and depth profiling.
The ToF-SIMS analysis revealed distinct peaks corresponding to Fe, Ni, and other peaks associated with Nafion®, whereas a straightforward correlation between the Ni.Fe ratio and the SIMS peak pattern is not possible.
The catalytic activity towards OER was evaluated through CV measurements, where the Fe2Ni3 ratio exhibited the most favorable performance, displaying a lower overpotential.
Engineered nanoparticles (NPs) with various chemical compositions and surface functionalities are routinely fabricated for industrial applications such as medical diagnostics, drug delivery, sensing, catalysis, energy conversion and storage, opto-electronics, and information storage which improve the quality of life and European prosperity. NP function, performance, interaction with biological species, and environmental fate are largely determined by their surface functionalities. Standardized repeatable surface characterization methods are therefore vital for quality control of NPs, and to meet increasing concerns regarding their safety. Therefore, industry, regulatory agencies, and policymakers need validated traceable measurement methods and reference materials. This calls for fit-for-purpose, validated, and standardized methods, and reference data and materials on the surface chemistry of engineered NPs. Here, we present a concept for the development of such standardized measurement protocols utilizing method cross-validation and interlaboratory comparisons (ILCs) with emphasis on both advanced measurement methods such as quantitative Nuclear Magnetic Resonance (qNMR), X-ray photoelectron spectroscopy (XPS) and secondary ion mass spectrometry (SIMS) and cost-efficient, non-surface specific methods like optical assays and electrochemical titration methods.
Electrocatalysis is and will continue to play a central role in the development of a new and modern sustainable economy, especially for chemicals and fuels. The storage of excess electrical energy into chemical energy by splitting water into hydrogen and oxygen is a feasible solution in this economic sector. A major drawback of electrical energy lies in the storage. Therefore, hydrogen is discussed as promising alternative. Fortunately, this issue can be effectively addressed through the implementation of chemical storage mechanisms. Due to their abundance on Earth and inherent stability in alkaline solutions, transition-metal oxides have become one of several viable alternatives to conventional noble-metal catalysts. Since FeNi oxide is one of the most active oxygen evolution reaction (OER) electrocatalysts for alkaline water electrolysis, it has been the subject of extensive research.
A series of different types of FeNi oxide nanoparticles (NPs) with atomic ratios covering a broad range, and various sizes with specific stoichiometric and non-stoichiometric iron and nickel ratios was synthesized and characterized by the combination of surface analysis techniques, such as time-of-flight secondary ion mass spectrometry (ToF-SIMS) and X-ray photoelectron spectroscopy (XPS). The morphology was studied using scanning electron microscopy (SEM) and transmission electron microscopy (TEM), which revealed the coexistence of mixed and unmixed iron and nickel NPs with comparable sizes in the range of 30–40 nm across all ratios. The synthesis technique displayed control over the iron-nickel ratio, as evidenced by energy dispersive X-ray spectroscopy (EDS) data. The presence of magnetite (Fe3O4) was detected in all samples investigated by X-ray diffraction (XRD). Furthermore, the existence of nickel ferrite (NiFe2O4) was shown in the Fe2Ni by XRD analysis. For the cyclic voltammetry (CV) measurements, the NPs were deposited onto glassy carbon electrodes using Nafion® as an ionomer, and 1 M KOH was employed as the electrolyte. Subsequently, the NPs/Nafion® electrode was transferred into the ToF-SIMS chamber to allow surface analysis and depth profiling.
The ToF-SIMS analysis revealed distinct peaks corresponding to Fe, Ni, and other peaks associated with Nafion®, whereas a straightforward correlation between the Ni.Fe ratio and the SIMS peak pattern is not possible.
The catalytic activity towards OER was evaluated through CV measurements, where the Fe2Ni3 ratio exhibited the most favorable performance, displaying a lower overpotential.
These data sets serve as models for calculating the specific surface area (BET method) using gas sorption in accordance with ISO 9277.
The present measurements were carried out with nitrogen at 77 Kelvin and argon at 87 Kelvin.
It is recommended to use the following requirements for the molecular cross-sectional area:
Nitrogen: 0.1620 nm²
Argon: 0.1420 nm²
Titanium dioxides certified with nitrogen sorption and additionally measured with argon for research purposes were used as sample material.
The resulting data sets are intended to serve as comparative data for own measurements and show the differences in sorption behaviour and evaluations between nitrogen and argon.
These data are stored in the universal AIF format (adsorption information file), which allows flexible use of the data.
There is an urgent demand for reliable data on microplastic analysis, particularly on its physico-chemical properties as well as validated methodology to obtain such data. Through interlaboratory comparisons (ILCs) it becomes possible to assess accuracy and precision of methods by involving many laboratories around the world. At BAM, my tasks focused around organisation of an ILC on physico-chemical characterisation of microplastic detection methods under the international pre-standardisation platform VAMAS (www.vamas.org/twa45/) as Project 2 “Development of standardized methodologies for characterisation of microplastics with microscopy and spectroscopy methods” under the Technical Working Area TWA 45 “Micro and Nano Plastics in the Environment”.
With a proud number of 84 participants this ILC is able to provide superior statistical results. Thermoanalytical (Py-GC/MS and TED-GC/MS) and vibrational (µ-IR and µ-Raman) methods were asked for identification and quantification of microplastic test samples according to mass or particle number. Preliminary results indicate which methods show a higher accuracy and precision and reveal some sample preparation ideas which work best for microplastics characterisation. At the end of the ILC an overall plausibility of the results will be assessed.
Lanthanide Nanocrystals as Authentication and Security Tags and Reporters for Optical Sensors
(2023)
Counterfeiting of goods has serious economic implications worldwide and can present a considerable threat to human health and national security, rendering product authentication more and more important. This led to an increasing interest in simple tags for anticounterfeiting and authentication applications for the integration into different materials and matrices that are robust enough to survive the respective production processes and can be read out in-situ with simple instrumentation.
Here we present a platform of chemically inert, multi-color luminescent lanthanide nanocrystals (LnNC) consisting of a NaYF4 matrix doped with Yb, Er, Tm, or Ho as promising candidates for such applications.
LnNC with characteristic multi-color emission patterns, composed of narrow bands of varying intensity in the ultraviolet, visible, near-infrared, and short-wave were synthesized via a thermal decomposition approach under inert conditions[1]. The tailor-made design of different emission pattern was achieved by tuning particle size, material composition, and particle surface chemistry in upscaleable syntheses.[2] Particle size and morphology were determined by dynamic light scattering and transmission electron microscopy and the optical properties were characterized by absorption and fluorescence spectroscopy as well as fluorescence lifetime measurements.
The particles were then incorporated into security inks and consumer products. In addition, microenvironment-specific changes in the emission properties of the LnNC tag were utilized to study and sense changes of physico-chemical parameters in different matrices.
Polymers with intrinsic microporosity are promising candidates for the active separation layer in gas separation membranes. These polymers are characterized by a high permeability and reasonable permselectivity. The latter point is somehow surprising because for microporous systems a more Knudson-like diffusion is expected then a size dependent temperature activated sieving process. It was argued in the framework of a random gate model that molecular fluctuations on a time scale from ps to ns are responsible for the permselectivity.
Here series of polymers of intrinsic microporosity (PIMs) as well as microporous polynorbornenes with bulky Si side groups and a rigid backbone are considered. The polymers have different microporosity characterized by high BET surface area values.
First inelastic time-of-flight neutron scattering measurements were carried out to investigate the low frequency density of state (VDOS). The measured data show the characteristic low frequency excess contribution to the VDOS above the Debye sound wave level, generally known as the Boson peak in glass-forming materials. It was found that the frequency of the maximum position of the Boson peak correlates with the BET surface area value.
Secondly elastic scans as well as quasielastic neutron scattering measurements by a combination of neutron time-of-flight and backscattering have been out. A low temperature relaxation process was found for both polymers. 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.
The neutron scattering experiments were accompanied by fast scanning calorimetry and broadband dielectric investigations as well as atomistic molecular dynamic simulations.
Counterfeiting of goods has serious economic implications worldwide and can be a threat to human health and safety. Upconversion nanoparticles (UCNPs)are ideal candidates for optical encoding of various materials. Particles with tailor-made emission patterns can be used as anti-counterfeiting markers and luminophores in security inks and to track material flows. Microenvironment-specific changes in the emission properties of the UCNP tags can be used to study, signal, and sense changes of physico-chemical parameters in different environments, e.g., building
materials.
This talk explores the intricate connections between scientists, focusing on the networking dynamics within the realm of metal-organic frameworks (MOFs). The study delves into the collaborative networks formed among scientists, shedding light on the synergistic relationships that contribute to advancements in MOF research.
Mechanochemistry has become a compelling method for producing (new) molecule s and mate-rials, but the inner workings of the milling jars remain a fascinating mystery. Advances in this field include tailor-made chemical systems and real-time revelations using techniques such as XRD and Raman spectroscopy.
This talk will discuss our recent progress in using X-ray diffraction and sophisticated spectros-copy to observe reactions in various material systems during ball milling and extrusion in real-time.
The complexity of mechanochemical reactions spans multiple scales and requires a holistic ap-proach. The categorisation of reactions by investigative methods precedes the exploration of real-time analysis that reveals macroscopic processes using synchrotron techniques.
During this exploration, one resounding realisation remains: We are on the threshold of under-standing. The complexity of mechanochemistry requires a collective effort, drawing on the ex-pertise of a diverse community. As we unravel the web of mechanochemical phenomena, we acknowledge the collaborative nature of this ongoing journey.
Synthesis of Li ion battery materials via ball milling has been a huge area of growth, leading to new high-capacity electrode materials, such as a number of promising disordered rocksalt (DRS) phases. In prior work, it was generally assumed that the synthesis was facilitated simply by local heating effects during the milling process. In this work, we show that ball milling Li2MoO4 leads to a phase transformation to the high pressure spinel polymorph and we report electrochemical data for this phase. This observation of the formation of a high pressure polymorph shows that local heating effects alone cannot explain the phase transformation observed (phenakite to spinel) and so indicates the importance of other effects. In particular, we propose that when the milling balls collide with the material, the resulting shockwaves exert a localised pressure effect, in addition to local heating. To provide further support for this, we additionally report ball milling results for a number of case studies (Li2MnO3, Li2SnO3, Nb2O5) which reinforces the conclusion that local heating alone cannot explain the phase transformations observed. The work presented thus provides greater fundamental understanding of milling as a synthetic pathway and suggests potential strategies to prepare such samples without milling (e.g., doping to create internal chemical pressure). In addition, we suggest that further research is needed into the effect of the use of milling as a route to smaller particles, since we believe that such milling may also be affecting the surface structure of the particles through the influence of the shockwaves generated.
Mechanochemistry emerges as a potent, environmentally friendly, and straightforward approach for crafting novel multicomponent crystal systems. Various milling parameters, including milling frequency, time, filling degree of the milling jar, ball diameter, vessel size, degree of milling ball filling, and material of jars, are recognized influencers on the mechanisms and rates of product formation. Despite the growing interest in mechanochemistry, there exists a gap in understanding the mechanistic aspects of mechanochemical reactivity and selectivity. To address this, diverse analytical methods and their combinations, such as powder X-ray diffraction, X-ray absorption spectroscopy, NMR, Raman spectroscopy, and thermography, have been developed for real-time, in situ monitoring of mechanochemical transformations.
This discussion centers on our recent findings, specifically investigating the formation of (polymorphic) cocrystals and metal-organic frameworks. Through these studies, we aim to unravel the impact of milling parameters and reaction sequences on the formation mechanism and kinetics. Notably, in the mechanochemical chlorination reaction of hydantoin, normalizing kinetic profiles to the volume of the milling ball unequivocally demonstrates the conservation of milling reaction kinetics. In this ball-milling transformation, physical kinetics outweigh chemical factors in determining reaction rates. Attempting to interpret such kinetics solely through chemical terms poses a risk of misinterpretation. Our results highlight that time-resolved in situ investigations of milling reactions provide a novel avenue for fine-tuning and optimizing mechanochemical processes.
Investigating the mechanism and kinetics of the mechanochemical synthesis of multi-component systems
(2023)
Mechanochemistry is a promising and environmentally friendly approach for synthesizing (novel) multicomponent crystal systems. Various milling parameters, such as milling frequency, milling time, and ball diameter have been shown to influence the mechanisms and rates of product formation. Despite increasing interest in mechanochemistry, there is still limited understanding of the underlying reactivity and selectivity mechanisms.
Various analytical techniques have been developed to gain insight into the mechanochemical transformations, including powder X-ray diffraction, X-ray adsorption spectroscopy, NMR, Raman spectroscopy and thermography. Using these techniques, we have studied the formation of (polymorphic) cocrystals, organometallic compounds and salts, and elucidated the influence of milling parameters and reaction sequences on the formation mechanism and kinetics.
For example, our study of the mechanochemical chlorination reaction of hydantoin revealed that normalisation of the kinetic profiles to the volume of the grinding ball clearly showed that physical kinetics dominate the reaction rates in a ball-milling transformation. Attempts to interpret such kinetics in purely chemical terms risk misinterpretation of the results.
Our results suggest that time-resolved in situ investigation of milling reactions is a promising way to fine-tune and optimise mechanochemical processes.
Mechanochemistry emerges as a potent, environmentally friendly, and straightforward approach for crafting novel multicomponent crystal systems. Various milling parameters, including milling frequency, time, filling degree of the milling jar, ball diameter, vessel size, degree of milling ball filling, and material of jars, are recognized influencers on the mechanisms and rates of product formation. Despite the growing interest in mechanochemistry, there exists a gap in understanding the mechanistic aspects of mechanochemical reactivity and selectivity. To address this, diverse analytical methods and their combinations, such as powder X-ray diffraction, X-ray absorption spectroscopy, NMR, Raman spectroscopy, and thermography, have been developed for real-time, in situ monitoring of mechanochemical transformations.
This discussion centers on our recent findings, specifically investigating the formation of (polymorphic) cocrystals and metal-organic frameworks. Through these studies, we aim to unravel the impact of milling parameters and reaction sequences on the formation mechanism and kinetics. Notably, in the mechanochemical chlorination reaction of hydantoin, normalizing kinetic profiles to the volume of the milling ball unequivocally demonstrates the conservation of milling reaction kinetics. In this ball-milling transformation, physical kinetics outweigh chemical factors in determining reaction rates. Attempting to interpret such kinetics solely through chemical terms poses a risk of misinterpretation. Our results highlight that time-resolved in situ investigations of milling reactions provide a novel avenue for fine-tuning and optimizing mechanochemical processes.
Use of the solvent-free mechanochemical method for a sustainable preparation of pharmaceuticals
(2023)
With the growing interest in environmental issues on the part of governments and institutions, pharmaceutical industries are asked to reduce their environmental footprint. Given the major impact related to the use of solvents, the development of methodologies less solvent demanding is nowadays even more urgent. In light of that, mechanochemistry would be a suitable solvent-free technology since it promotes the activation of the chemical reactions between (generally) solid materials via inputs of mechanical energy. Since such reactions may occur outside the kinetic and thermodynamic rules of conventional solution chemistry, the main limit of mechanochemistry is the poor mechanistic understanding of the solid-state transformations involved, which is still hindering a widespread use of the method, as well a scale-up to the industrial level. However, the development of methods for real-time monitoring of the mechanochemical reactions enables obtaining (in)accessible information on reaction intermediates, new products, or reaction time, thus getting closer to a better understanding of the mechanistic behaviour. With the rules of this chemistry becoming increasingly clear, the new reaction pathways of mechanochemistry wouldn’t represent a limit anymore, but an asset, that may lead to lot of opportunities for the pharmaceutical industry.
A crucial aspect of ensuring sustainable raw material utilization to meet global demand lies in the efficient recovery and reuse of critical elements and compounds. Phosphate, PO43-, and many transition metals e.g. Ni and Co are listed as critical raw materials (CRMs) due to their indispensable role in numerous industrial processes. However, these elements can also exert harmful environmental impacts, with phosphorus being a major contributor to anthropogenic eutrophication and transition metal ions acting as toxic pollutants, particularly in ground- and wastewaters. Typically, separate pathways have been considered to extract hazardous substances such as transition metals or phosphate, independently from each other. Here, we report the crystallization pathways of transition metal phosphate (TMP) compounds, M-struvite and M-phosphate octahydrate with M = Ni2+, Co2+, NixCo1-x2+, NH4MPO4∙6H2O, M3(PO4)2∙8H2O from aqueous solutions. The co-precipitation of these particular TMP compounds from industrial and agricultural wastewaters has high potential as a P- and 3d metal recovery route.
For efficient extraction and transformation of the TMPs, a comprehensive understanding of their nucleation and crystallization pathways from aqueous solutions is required. While the crystallization mechanisms of magnesium or calcium phosphate-bearing phases have been researched for many decades (e.g. struvite, apatite), investigations into TMP materials are relatively scarce and often focus on the adsorption of transition metals on the surface instead of their actual incorporation in minerals. In our study, we investigated in detail the precipitation process of several Co and Ni phosphates using ex- and in-situ spectroscopic-, spectrometric- and diffraction-/scattering-based techniques. We show that the crystallization behavior of TMPs, indeed deviates from a classical crystallization paradigm and follows a non-classical multi-step pathway. Our work extends the understanding of TMP crystallization by elucidating the formation of amorphous precursors preceding the final crystalline phase This time-dependent transition of the transition metal precursor phases can be observed by electron-imaging/tomography depicting a progressively changing amorphous solids until their ultimate reconfiguration to a crystal (Figure 1). Here, the two-metallic NixCo1-x-mixtures deviated anomalously in their reaction kinetics, crystallization outcome and participation of both metals from their pure endmembers. By measuring the crystallization with in-situ X-ray scattering and pH using a flow-through setup geometry, a complex prolonged interplay among nucleating entities e.g. and amorphous or crystalline solids could be observed in the metal phosphate mixtures reaching equilibrium after almost two and a half hours (Figure 2). Our results provide a holistic perspective on the crystallization behavior of transition metal phosphate phases, shedding light on their unique nucleation and growth kinetics involving structural and chemical transformations of the intermediate phases.
Bonds and local atomic environments are crucial descriptors of material properties. They have been used to create design rules and heuristics for materials. More and more frequently, they are used as features in machine learning. Implementations and algorithms (e.g., ChemEnv and LobsterEnv) for identifying these local atomic environments based on geometrical characteristics and quantum-chemical bonding analysis are nowadays available. Fully automatic workflows and analysis tools have been developed to use quantum-chemical bonding analysis on a large scale and for machine-learning approaches. The latter relates to a general trend toward automation in density functional-based materials science. The lecture will demonstrate how our tools, that assess local atomic environments, helped to test and develop heuristics and design rules and an intuitive understanding of materials.
Liaison of ISO/TC 202 Microbeam Analysis with VAMAS/TWA 37 Quantitative Microstructural Analysis
(2023)
The progress in activities on Microbeam Analysis under VAMAS/TWA 37 is reviewed. Particularly the liaison with the new projects within the ISO technical committee TC 202 is presented and discussed with respect to the identification and launching corresponding VAMAS projects. The ongoing project "FIB sample processing for TEM" is presented in detail.
Mechanochemistry is an effective, environmentally benign, and facile method for the synthesis of new multicomponent crystal systems. Different milling parameters are known to affect the mechanisms and rates of product formation: milling frequency, milling time, filling degree of the milling jar, ball diameter and vessel size, degree of milling ball filling, and material of jars. The increasing interest in mechanochemistry is contrasted by a limited mechanistic understanding of the mechanochemical reactivity and selectivity.
Different analytical methods and their combinations have been developed for the time resolved in situ monitoring of mechanochemical transformations, including powder X-ray diffraction, X-ray adsorption spectroscopy, NMR, Raman spectroscopy, and thermography.
Here we will discuss our recent results investigating the formation of (poly-morphic) cocrystals[1,3], metal-organic compounds, and salts, thereby elucidating the influence of milling parameters and reaction sequences on the formation mechanism and kinetics. For the mechanochemical chlorination reaction of hydantoin normalizing the kinetic profiles to the volume of the milling ball showed clearly that milling reaction kinetics are conserved. Here physical kinetics dominate reaction rates in a ball-milling transformation. Attempting to interpret such kinetics in purely chemical terms risk misinterpreting the results.
Our results indicate that time-resolved in situ investigation of milling reactions offer a new approach to tune and optimize mechanochemical processes.
While a lage amount of research on high entropy alloys is oriented towards mechanical properties and the microstructural improvement it is also necessary to keep an eye on the environment that potential application materials will be submitted to. The Co-Cr-Fe-Ni based high entropy family has shown great potential over the years of high entropy research and some candidate alloys are chosen for an insight into their corrosion behaviour. Several atmospheres are studied, i.e. O2, H2O, SO2 and a mix thereof in argon as well as synthetic air. Just as for classic alloys, the chromium is the most important element in terms of protection agains further corrosion. The addition of manganese, as in case of the “Cantor alloy” CrMnFeCoNi, overpasses Cr when it comes to oxygen affinity and thus counteracts the layer formation of Cr2O3. Even without Mn, a temperature chosen too high will also affect the formation of the chromium oxide layer and spall it off, annulling its protective potential. We can also observe how trace elements influence the layer formation. These effects and their mechanisms will be discussed for the alloys CrFeNi, CoCrNi, CrMnFeCoNi and variations of Al10Co25Cr8Fe15Ni36Ti6 using a combination of electron microscopy, thermodynamic calculations and x-ray diffraction.
Titanium and its alloys are known to allow the straightforward laser-based manufacturing of ordered surface nanostructures, so-called high spatial frequency laser-induced periodic surface structures (HSFL). These structures exhibit sub-100 nm spatial periods – far below the optical diffraction limit. The resulting surface functionalities are usually enabled by both, topographic and chemical alterations of the nanostructured surfaces. For exploring these effects, multi-method characterizations were performed here for HSFL processed on Ti–6Al–4V alloy upon irradiation with near-infrared ps-laser pulses (1030 nm, ≈1 ps pulse duration, 1–400 kHz) under different laser scan processing conditions, i.e., by systematically varying the pulse repetition frequency and the number of laser irradiation passes. The sample characterization involved morphological and topographical investigations by scanning electron microscopy (SEM), atomic force microscopy (AFM), tactile stylus profilometry, as well as near-surface chemical analyses hard X-ray photoelectron spectroscopy (HAXPES) and depth-profiling time-of-flight secondary ion mass spectrometry (ToF-SIMS). This provides a quantification of the laser ablation depth, the geometrical HSFL characteristics and enables new insights into the depth extent and the nature of the non-ablative laser-induced near-surface oxidation accompanying these nanostructures. This allows to answer the questions how the processing of HSFL can be industrially scaled up, and whether the latter is limited by heat-accumulation effects.
Although the use of noble metal catalysts can increase the efficiency of hydrogen evolution reaction, the process is still limited by the characteristics of the metal-hydrogen (M−H) bond, which can be too strong or too weak, depending on the metal employed. Studies revealed that the hydrogen affinity for the metal surface (i.e. H absorption/desorption) is regulated also by the potential at the metal nanoparticles. Through controlled periodic illumination (CPI) of a series of metal/TiO2 suspensions, here we demonstrated that an increase of the HER efficiency is possible for those photodeposited metals which have a Tafel slope below 125 mV. Two possible explanations are here reported, in both of them the M−H interaction and the metal covering level play a prominent role, which also depend on the prevailing HER mechanism (Volmer-Heyrovsky or Volmer-Tafel).
Liaison activities within ISO/TC 202 'Microbeam Analysis' which are relevant to ISO/TC 229 'Nanotechnologies' are reported acoording to the structure defined by ISO/TC229 Nanotechnologies Liaisons Coordination Group (NLCG): new standards/documents, coordination issues, and further detailed specific information, e.g. publications, events, comments.
The energy crisis becomes more prominent in higher altitude countries like Germany, with higher annual energy demand. Thus, the generation of higher energy density fuel like hydrogen from renewable resources become the only way to solve the zero-emission energy system while avoiding the expensive batteries as an energy storage option. Therefore, water electrolysis cells to produce hydrogen and oxygen by storing of solar/wind energy in chemical bonds is a fruitful alternative for renewable and long-term energy generation. Thus, designing inexpensive water-splitting electrocatalyst material becomes a field of research of utmost importance. High entropy metal hydroxide organic frameworks (HE-MHOFs) are composed of high entropy hydroxide layer inside MOFs, resulting in a high degree of structural complexity and diversity than conventional MOFs. The concept of ‘high entropy’ refers to multiple types of metal ions (Metal = TM) in a near equimolar ratio in the same framework, creating a high degree of disorder and many possible structural configurations. Here, the HE-MHOF successfully synthesized by a conventional solvothermal process, crystallizes in the single phase with significant lattice distortion. A special-quasi-random (SQS) structure was simulated with equimolar compositions (~20% TM = Mn, Co, Ni, Cu and Zn) and a comparison was made with the ICP-AES (inductively coupled plasma atomic emission spectroscopy), XANES (X-ray absorption near edge structure) and XAFS (X-ray absorption fine structure) observations. Further, the elemental mapping (Energy dispersive Spectroscopy) of HE-MHOF shows the presence of all five different metals in the same crystallite to substantiate the ‘high entropy’ state of the MOF. The HE-MHOF offers improved thermal stability than mono-metallic MHOF and exhibit unique properties compared to traditional monometallic (Ni2+) MOF variants. Firstly, to elucidate the effect of the multimetallic system on the catalytic performance, we have performed density functional theory (DFT) calculations to investigate pre-redox cycles involved in the catalytic activation of HE (and Ni)-MOFs. HE-MHOF is further investigated as an electrocatalyst for oxygen evolution reaction (OER) due to its special high entropy hydroxide layered structure and electronic properties. Our DFT results have examined the traditional proton-coupled electron transfer (PCET) steps involving the single transition-metal site. The scrutiny of d-band centers and their behaviour in catalytic upgradation is investigated with density of states (DOS) analysis. It exhibits outstanding performance towards oxygen evolution reaction (OER) comparable to the experimental findings, which is also comparable to state-of-the-art OER catalysts based on precious metals such as iridium oxide and platinum carbon. We have considered different electrolyte solutions to elucidate the fast kinetics oxygen evolution reaction in the presence of various external nucleophilic anions. In hydroxyl-based MOFs, electrolytes' influence can substantially enhance catalytic activities. Here, with the help of DFT simulations, we have investigated the effect of the nucleophilicity of anion on each elementary reaction involved in the PCET mechanism of OER.
Metal-organic framework-based biocomposites (MOF-biocomposites) are promising materials for biosensing, biocatalysis, and delivery of biopharmaceuticals. One of the most studied MOFs for bioapplications is ZIF-8 (zeolitic imidazolate framework 8) due to its high surface area, high thermal and chemical stability, and low cytotoxicity. The conventional synthesis of ZIF-8-biocomposites called biomimetic mineralization includes mixing selected biomolecules 2-methylimidazole, and soluble Zn2+ source in water.[3] Despite the high efficiency of the method, it does not allow for large-scale production and is restricted to hydrophilic biomolecules. Aimed at developing a scalable and versatile approach, we adapted our recently-reported ZIF-8 reactive extrusion for biocomposite production.
We selected bovine serum albumin (BSA) as an inexpensive model biomacromolecule for the preparation of biocomposites. The synthesis of BSA@ZIF-8 was performed using a twin-screw extruder ZE 12 HMI (Three-Tec Gmbh) at a mild temperature of 40 °C. Automatic volumetric feeder ZD 12B (Three-Tec GmbH) was used to supply the reagent mixture consisting of 2-methylimidazole, zinc source, and BSA. To initiate the reaction, a catalytic amount of EtOH was added using a peristaltic pump BT-L (Lead Fluid, China). Powder X-Ray diffraction (PXRD), thermogravimetric analysis (TGA), FTIR, and N2 adsorption were used to characterize the extrudates.
Highly crystalline and pure BSA@ZIF-8 with different BSA loadings was isolated after washing the extrudate with EtOH and sodium dodecyl sulfate. The EtOH feeding rate was optimized by following the protein encapsulation efficiency at a BSA mass fraction of 10%. A continuous extruder operation under optimized conditions showed good reproducibility and capability of producing biocomposites on the kilograms scale. These results provide highly valuable information for cheap and large-scale production of ZIF-8-based biocomposites. Due to the lack of restrictions on molecule size and solubility, our proof-of-concept study may significantly expand the selection of biomolecules for immobilization in ZIF-8, making the method applicable to various functional applications
We report the scale-up of a batch solid synthesis of zeolitic imidazolate framework-8 (ZIF-8) for reactive extrusion. The crystalline product forms in the extruder directly under the mixture of solid 2-methylimidazole and basic zinc carbonate in the presence of a catalytic amount of liquid. The process parameters such as temperature, liquid type, feeding rate, and linker excess were optimized using the setup specifically designed for in situ Raman spectroscopy. Highly crystalline ZIF-8 with a Brunauer–Emmett–Teller (BET) surface area of 1816 m2 g–1 was quantitatively prepared at mild temperature using a catalytic amount of ethanol and a small excess of the linker. Finally, we developed a simple and comprehensive approach to evaluating the environmental friendliness and scalability of metal–organic framework (MOF) syntheses in view of their large-scale production.
Optimizing the Green Synthesis of ZIF-8 by Reactive Extrusion Using In Situ Raman Spectroscopy
(2023)
ZIF-8 is a prominent member of the zeolitic imidazolate frameworks (ZIFs) subfamily of MOFs which possesses high thermal, chemical, and mechanical stabilities. Different routes have been explored to achieve the large-scale production of ZIF-8. However, these synthetic procedures are often inconsistent with the principles of sustainable chemical manufacturing. Aimed at developing scalable and greener production of ZIF-8, we adapted our previously reported in-batch „mix and wait“ synthesis[2] to continuous extrusion. To optimize the process, in-situ Raman spectroscopy was applied. Finally, we developed a simple and comprehensive approach to evaluating the environmental friendliness and scalability of MOF syntheses in view of their large-scale production.
The synthesis of ZIF-8 was performed using a twin-screw extruder ZE 12 HMI equipped with an automatic volumetric feeder ZD 12B (Three-Tec GmbH, Switzerland) and peristaltic pump BT-L (Lead Fluid, China). The process was monitored in six different zones using a Raman RXN1TM analyzer (Kaiser Optical Systems, France) with a non-contact probe head. PMMA screw-in parts, which are transparent to Raman laser radiation, were specially manufactured to provide the laser focus within the barrel. PXRD, TGA, N2 adsorption measurements, and SEM were used as complementary techniques to characterize the extrudates.
The batch ‘mix and wait’ synthesis of ZIF-8, consisting of bringing solid basic zinc carbonate and 2-methylimidazole in contact in a closed vial, was successfully adapted to reactive extrusion. The crystalline ZIF-8 continuously forms in the extruder under the mixing of solid reagents in the presence of a catalytic amounts of H2O or EtOH. The temperature, type of liquid, feeding rate, and excess of linker were optimized using in situ Raman spectroscopy. Pure and highly crystalline ZIF-8 was isolated at 40 °C by adding a catalytic amount of EtOH and a linker excess of 25%. The resulting material has excellent porosity with the BET surface area slightly exceeding that of the reference Basolite® Z1200 (1816 vs. 1734 m2 g–1). The reaction could yield ~ 3 kg d–1 assuming a continuous operation, with a space-time yield of ca. 67,000 kg m–3 d–1. The present method was compared to the published pathways based on Green Chemistry principles and proved to have the highest potential for large-scale production of ZIF-8.
Metal-organic framework-based biocomposites (MOF-biocomposites) are promising materials for biosensing, biocatalysis, and delivery of biopharmaceuticals. One of the most studied MOFs for bioapplications is ZIF-8 (zeolitic imidazolate framework 8) due to its high surface area, high thermal and chemical stability, and low cytotoxicity. The conventional synthesis of ZIF-8-biocomposites called biomimetic mineralization includes mixing selected biomolecules 2-methylimidazole, and soluble Zn2+ source in water. Despite the high efficiency of the method, it does not allow for large-scale production and is restricted to hydrophilic biomolecules. Aimed at developing a scalable and versatile approach, we adapted our recently-reported ZIF-8 reactive extrusion for biocomposite production.
We selected bovine serum albumin (BSA) as an inexpensive model biomacromolecule for the preparation of biocomposites. The synthesis of BSA@ZIF-8 was performed using a twin-screw extruder ZE 12 HMI (Three-Tec Gmbh) at a mild temperature of 40 °C. Automatic volumetric feeder ZD 12B (Three-Tec GmbH) was used to supply the reagent mixture consisting of 2-methylimidazole, zinc source, and BSA. To initiate the reaction, a catalytic amount of EtOH was added using a peristaltic pump BT-L (Lead Fluid, China). Powder X-Ray diffraction (PXRD), thermogravimetric analysis (TGA), FTIR, and N2 adsorption were used to characterize the extrudates.
Highly crystalline and pure BSA@ZIF-8 with different BSA loadings was isolated after washing the extrudate with EtOH and sodium dodecyl sulfate. The EtOH feeding rate was optimized by following the protein encapsulation efficiency at a BSA mass fraction of 10%. A continuous extruder operation under optimized conditions showed good reproducibility and capability of producing biocomposites on the kilograms scale. These results provide highly valuable information for cheap and large-scale production of ZIF-8-based biocomposites. Due to the lack of restrictions on molecule size and solubility, our proof-of-concept study may significantly expand the selection of biomolecules for immobilization in ZIF-8, making the method applicable to various functional applications
A cobalt(III) complex, [Co(L)3](DMF) (1) of Schiff base ligand HL, 2-((E)-(benzylimino)methyl)-4-bromophenol is prepared and single crystal X-ray structural analysis have also been performed. The structures of complex 1 showed hexa-coordinated mononuclear systems that adopt octahedral geometry. The complex has also exhibited the supramolecular networks through non-covalent interactions like H-bonding, C–Hπ stacking. Moreover, the complex 1 is very effective in the catalytic fixation of carbon dioxide in propergyl alcohols to produce α-alkylidene cyclic carbonates. The catalytic production of α-alkylidene cyclic carbonates have been carried out through carboxylative cyclization of propargyl alcohols using CO2 balloon of 1 atm pressure at 80 ◦C. Solvent free condition (green synthesis) made this catalytic protocol eco-friendly towards the environment. Utilizing various substrates of propargyl alcohols moderate to high percentage yield (62–95%) of respective α-alkylidene cyclic carbonates product have been isolated over this catalytic reaction. Besides, the theoretical calculations (DFT) was performed for the prediction of probable mechanism of the catalytic reaction
We show that mechanochemically driven polymorphic transformations can require extremely long induction periods, which can be tuned from hours to days by changing ball milling energy. The robust design and interpretation of ball milling experiments must account for this unexpected kinetics that arises from energetic phenomena unique to the solid state. Detailed thermal analysis, combined with DFT simulations, indicates that these marked induction periods are associated with processes of mechanical activation. Correspondingly, we show that the pre‐activation of reagents can also lead to marked changes in the length of induction periods. Our findings demonstrate a new dimension for exerting control over polymorphic transformations in organic crystals. We expect mechanical activation to have a much broader implication across organic solid‐state mechanochemistry.
We report the scale-up of a batch solid synthesis of zeolitic imidazolate framework-8 (ZIF-8) for reactive extrusion. The crystalline product forms in the extruder directly under the mixture of solid 2-methylimidazole and basic zinc carbonate in the presence of a catalytic amount of liquid. Highly crystalline ZIF-8 with a Brunauer−Emmett−Teller (BET) surface area of 1816 m2 g−1 was quantitatively prepared at mild temperature using a catalytic amount of ethanol and a small excess of the linker. Extruded ZIF-8 is an affordable alternative to commercial Basolite Z1200 as a reference material for H2 cryoadsorption.
An introductory lecture on the Dark Side of Science; what it is, why it exists, and what can be done to fight it. This lecture illuminates the increasing prevalence of fraudulent scientific work (e.g. faked data, manipulated images, paper mills) with plenty of examples and sources. The second section expands on the driving forces that caused this phenomenon to emerge, largely driven by pressures from management, peers and the researcher themselves. The third section expands on methods and tools that can be used to educate and arm oneself against this phenomenon. The 2023 edition includes new examples of larger fraudulent bodies of work emerging, and the problems posed by the arrival of LLMs.
Microplastics are solid polymeric particles with a size of 1-1000 μm (ISO/TR21960:2020), which can be emitted from mismanaged waste into the environment, where microplastic is now ubiquitous. What happens to the microplastics after ending up in the environment, which risks entail and what effects it has are not sufficiently clarified up to now. The most certain issue is that the plastic particles in the environment are exposed to natural ageing, are fragmenting and degrading, such that the potential risk to ecosystems and humans is increasing due to the formation of smaller and smaller particles, potentially even including nanoplastics, if these are ingested before their further degradation. Therefore, and in view of a possible registration of polymers under REACH in the future, it is necessary to investigate the degradation of thermoplastic polyurethanes (TPU) regarding hydrolysis stability to evaluate possible risks and effects to the environment.
In the present studies, one thermoplastic polyurethane – with and without hydrolysis stabilizer – is exposed to different pH buffers at 50°C for 14 days to investigate hydrolysis depending to different pH values (acid, alkali and neutral) based on OECD guideline TG111. The hydrolysis behavior of the TPUs is characterized by surface sensitive techniques and on bulk properties. First degradation effects can be detected by SEC. Hydrolysis, especially under acidic and basic conditions, leads to chain scissions to lower molecular masses. Furthermore, the degradation products which indicate the structure of the bulk material were detected by thermo-analytical methods like TGA-FTIR for the small degradation products and the thermo extraction/desorption-gaschromatography/mass spectrometry (TED-GC/MS) for bigger degradation products. Acidic and basic hydrolysis shows the same degradation behavior which is caused by a preferred scission of the ester and urethane functionalities. Surface-sensitive techniques such as XPS demonstrate less carboxylic acid formation at acidic than at alkaline pH value in the TPU without stabilator, where as the TPU with stabilator ages to the same extent in both pH ranges. Altogether, the hydrolysis of TPUs – independently of added stabilizer or not – in acid and alkali environment is accelerated compared to the neutral hydrolysis.
Due to their favorable properties and high porosity, zeolitic imidazolate frameworks (ZIFs) have recently received much limelight for key technologies such as energy storage, optoelectronics, sensorics, and catalysis. Despite widespread interest in these materials, fundamental questions regarding the zinc coordination environment remain poorly understood. By focusing on zinc(II)2-methylimidazolate (ZIF-8) and its tetrahedrally coordinated analogues with Br-, Cl-, and H-substitution in the 2-ring position, we aim to clarify how variations in the local environment of Zn impact the charge distribution and the electronic properties of these materials. Our results from densityfunctional theory confirm the presence of a Zn coordinative bond with a large polarization that is quantitatively affected by different substituents on the organic ligand. Moreover, our findings suggest that the variations in the Zn coordination induced by the functionalization have a negligible effect on the electronic structure of the considered compounds. On the other hand, halogen terminations of the ligands lead to distinct electronic contributions in the vicinity of the frontier region which ultimately reduce the band gap size by a few hundred millielectron volts. Experimental results obtained from X-ray absorption spectroscopy (Zn K-edge) confirm the trends predicted by theory and, together with them, contribute to a better understanding of the structure−property relationships that are needed to tailor ZIFs for target applications.
Laser-induced periodic surface structures (LIPSS) represent a unique route for functionalizing materials through the fabrication of surface nanostructures. Commercial AISI 316L stainless steel (SS316L) surfaces are laser treated by ultraviolet 300 ps laser pulses in a laser line scanning (LLS) approach. Processing parameters are optimized (pulse energy of 2.08 µJ, pulse repetition frequency of 300 kHz, and suitable laser scan and sample displacement rates) for the generation of low spatial frequency LIPSS over a large 25 × 25 mm2 area. Different angles of incidence of the laser radiation (0°, 30°, and 45°) and different linear laser beam polarizations (s and p) produce a plethora of rippled surface morphologies at distinct grains. Scanning electron microscopy and 2D Fourier transforms, together with calculations of the optical energy deposited at the treated surfaces using Sipe's first-principles electromagnetic scattering theory, are used to study and analyze in detail these surface morphologies. Combined with electron backscattering diffraction, analyses allow associating site-selectively various laser-induced-surface morphologies with the underlying crystalline grain orientation. Resulting grain orientation maps reveal a strong impact of the grain crystallographic orientation on LIPSS formation and point toward possible strategies, like multi-step processes, for improving the manufacturing of LIPSS and their areal coverage of polycrystalline technical materials.
Inspired by the chemistry of mussel adhesive proteins, polydopamine (PDA has been shown as one of the most versatile platforms for altering the properties and incorporating new functionalities to nearby any material surface despite its nature. Rich chemistry of PDA enables broad variety of surface modification and diverse secondary reactions that makes it extremely interesting for a wide range of application including biomedical field, e.g., drug delivery, adhesives, cell adhesion, biosensing. Despite high potential of polydopamine, the lack of deposition control and precision in existed methods limits their applications in microdevices and miniaturized functional systems like, for example, MEMS, microfluidic and sensorics.
Herein, we demonstrate a novel maskless approach for surface micropatterning with polydopamine based on Multiphoton Lithography that overcomes present limitations. Neither strong oxidants, metal ions nor adjustment of pH to alkaline is required by this technique. The spatial resolution down to 0.8 µm has been achieved which is at least an order of magnitude smaller than shown by other existed methods. We are able to control the morphology and thickness of the micropattern by altering fabrication parameters allowing structure gradient.
Apart from the glass substrate, we achieved PDA patterning at surfaces of different nature such as polychlorotrifluoroethylene, polydimethylsiloxane, polyethylene terephthalate, silicon wafers, and fluorinated glass coverslips. Post-modification of polydopamine micropatterns with protein enzyme like trypsin is demonstrated to highlight its sensing potential.
Presented in this work microfabrication technique empowers advanced applications of mussel-inspired materials in single-molecule bioassays, sensors and other complex microdevices.
Text Multiphoton lithography (MPL) has recently attracted significant research interest as a versatile tool capable of producing 2D and 3D micro- and nanoscopic features with high spatial resolution. The integrity of MPL microstructures, or their ability to respond to external stimuli, is of critical importance. However, achieving the desired properties of fabricated microcomponents for a specific application remains a challenge.
In this work, we present new MPL materials based on epoxy-acrylate interpenetrating networks (IPNs). We aim at 3D microstructures, whose properties can be easily tuned by varying the ratio of the IPN components and fabrication parameters (Figure 1). The resulting library of 3D microstructures was investigated for their thermal and mechanical properties using highly-sensitive space-resolved methods. Flash scanning calorimetry revealed the influence of both, IPN composition and fabrication parameters, on glass transition temperature and material fragility. AFM force-distance curve and intermodulation methods were used to characterize the mechanical properties with a lateral resolution of 1 micron and 4 nm, respectively. The deformation, stiffness and elastic behavior are discussed in detail in relation to the morphology. Moreover, we found that some 3D IPN microstructures exhibit fully elastic behavior. Our funding encourages the further development of IPN systems as versatile and easily tunable MPL materials.
AbstractThis work addresses the critical need for multifunctional materials and substrate‐independent high‐precision surface modification techniques that are essential for advancing microdevices and sensing elements. To overcome existing limitations, the versatility of mussel‐inspired materials (MIMs) is combined with state‐of‐the‐art multiphoton direct laser writing (DLW) microfabrication. In this way, 2D and 3D MIM microstructures of complex designs are demonstrated with sub‐micron to micron resolution and extensive post‐functionalization capabilities. This study includes polydopamine (PDA), mussel‐inspired linear, and dendritic polyglycerols (MI‐lPG and MI‐dPG), allowing their direct microstructure on the substrate of choice with the option to tailor the patterned topography and morphology in a controllable manner. The functionality potential of MIMs is demonstrated by successfully immobilizing and detecting single‐stranded DNA on MIM micropattern and nanoarray surfaces. In addition, easy modification of MIM microstructure with silver nanoparticles without the need of any reducing agent is shown. The methodology developed here enables the integration of MIMs in advanced applications where precise surface functionalization is essential.
To date, there are very few technologies available for the conversion of low-temperature waste heat into electricity. Thermomagnetic generators are one approach proposed more than a century ago. Such devices are based on a cyclic change of magnetization with temperature. This switches a magnetic flux and, according to Faraday’s law, induces a voltage.
Here we give an overview on our research, covering both materials and systems. We demonstrate that guiding the magnetic flux with an appropriate topology of the magnetic circuit improves the performance of thermomagnetic generators by orders of magnitude. Through a combination of experiments and simulations, we show that a pretzel-like topology results in a sign reversal of the magnetic flux. This avoids the drawbacks of previous designs, namely, magnetic stray fields, hysteresis and complex geometries of the thermomagnetic material.
Though magnetocaloric materials had been the first choice also for thermomagnetic generators, they require some different properties, which we illustrate with Ashby plots for materials selection. Experimentally we compare La-Fe-Co-Si and Gd plates in the same thermomagnetic generator. Furthermore, we discuss corrosion and deterioration under cyclic use is a severe problem occurring during operation. To amend this, composite plates using polymer as a matrix have been suggested previously.
Since the function of materials is controlled by properties and processes on the atomic scale, ab initio based high-throughput methods are valuable strategies in materials design. For computational efficiency, they are however often restriction to T=0K calculations, while many technologically relevant materials properties and thermodynamic stabilities change when going from low to high temperatures. On the other hand, the constantly increasing performance of digital tools for simulation and data-driven science enables more targeted material development including these kinds of finite-temperature effects. A flexible infrastructure, including data management and workflow solutions is required to make this symbiosis user-friendly efficient. Within this presentation, examples from ab initio thermodynamics for the design of phase stabilities in hard-magnetic alloys and defect-phases in advanced high-strength steels will be demonstrated. We will discuss physical concepts with a focus at the impact of magnetic excitations. At the same time, the examples will be used to derive requirements and present solutions for a digital infrastructure. An outlook will be given to current strategies with the NDFI initiative NFDI-MatWerk.