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This work presents an open source database with suitable retention parameters for prediction and simulation of GC separations and gives a short introduction to three common retention models. Useful computer simulations play an important role to save resources and time in method development in GC. Thermodynamic retention parameters for the ABC model and the K-centric model are determined by isothermal measurements. This standardized procedure of measurements and calculations, presented in this work, have a useful benefit for all chromatographers, analytical chemists, and method developers because it can be used in their own laboratories to simplify the method development. The main benefits as simulations of temperature-programed GC separations are demonstrated and compared to measurements. The observed deviations of predicted retention times are in most cases less than 1%. The database includes more than 900 entries with a large range of compounds such as VOCs, PAHs, FAMEs, PCBs, or allergenic fragrances over 20 different GC columns.
Several species of (poly)saccharides and organic acids can be found often simultaneously in various biological matrices, e.g., fruits, plant materials, and biological fluids. The analysis of such matrices sometimes represents a challenging task. Using Aloe vera (A. vera) plant materials as an example, the performance of several spectroscopic methods (80 MHz benchtop NMR, NIR, ATR-FTIR and UV-Vis) for the simultaneous analysis of quality parameters of this plant material was compared. The determined parameters include (poly)saccharides such as aloverose, fructose and glucose as well as organic acids (malic, lactic, citric, isocitric, acetic, fumaric, benzoic and sorbic acids). 500 MHz NMR and high-performance liquid chromatography (HPLC) were used as the reference methods.
UV-VIS data can be used only for identification of added preservatives (benzoic and sorbic acids) and drying agent (maltodextrin) and semiquantitative analysis of malic acid. NIR and MIR spectroscopies combined with multivariate regression can deliver more informative overview of A. vera extracts being able to additionally quantify glucose, aloverose, citric, isocitric, malic, lactic acids and fructose. Low-field NMR measurements can be used for the quantification of aloverose, glucose, malic, lactic, acetic, and benzoic acids. The benchtop NMR method was successfully validated in terms of robustness, stability, precision, reproducibility and limit of detection (LOD) and quantification (LOQ), respectively.
All spectroscopic techniques are useful for the screening of (poly)saccharides and organic acids in plant extracts and should be applied according to its availability as well as information and confidence required for the specific analytical goal. Benchtop NMR spectroscopy seems to be the most feasible solution for quality control of A. vera products.
While many proteins are known clients of heat shock protein 90 (Hsp90), it is unclear whether the transcription factor, thyroid hormone receptor beta (TRb), interacts with Hsp90 to control hormonal perception and signaling. Higher Hsp90 expression in mouse fibroblasts was elicited by the addition of triiodothyronine (T3). T3 bound to Hsp90 and enhanced adenosine triphosphate (ATP) binding of Hsp90 due to a specific binding site for T3, as identified by molecular docking experiments. The binding of TRb to Hsp90 was prevented by T3 or by the thyroid mimetic sobetirome. Purified recombinant TRb trapped Hsp90 from cell lysate or purified Hsp90 in pull-down experiments. The affinity of Hsp90 for TRb was 124 nM. Furthermore, T3 induced the release of bound TRb from Hsp90, which was shown by streptavidin-conjugated quantum dot (SAv-QD) masking assay. The data indicate that the T3 interaction with TRb and Hsp90 may be an amplifier of the cellular stress response by blocking Hsp90 activity.
Nanomedicine strategies were first adapted and successfully translated to clinical application for diseases, such as cancer and diabetes. These strategies would no doubt benefit unmet diseases needs as in the case of leishmaniasis. The latter causes skin sores in the cutaneous form and affects internal organs in the visceral form. Treatment of cutaneous leishmaniasis (CL) aims at accelerating wound healing, reducing scarring and cosmetic morbidity, preventing parasite transmission and relapse. Unfortunately, available treatments show only suboptimal effectiveness and none of them were designed specifically for this disease condition. Tissue regeneration using nano-based devices coupled with drug delivery are currently being used in clinic to address diabetic wounds. Thus, in this review, we analyse the current treatment options and attempt to critically analyse the use of nanomedicine-based strategies to address CL wounds in view of achieving scarless wound healing, targeting secondary bacterial infection and lowering drug toxicity.
Process-induced changes in the morphology of biodegradable polybutylene adipate terephthalate (PBAT) and polylactic acid (PLA) blends modified with various multifunctional chainextending cross-linkers (CECLs) are presented. The morphology of unmodified and modified films produced with blown film extrusion is examined in an extrusion direction (ED) and a transverse direction (TD). While FTIR analysis showed only small peak shifts indicating that the CECLs modify the molecular weight of the PBAT/PLA blend, SEM investigations of the fracture surfaces of blown extrusion films revealed their significant effect on the morphology formed during the processing. Due to the combined shear and elongation deformation during blown film extrusion, rather spherical PLA islands were partly transformed into long fibrils, which tended to decay to chains of elliptical islands if cooled slowly. The CECL introduction into the blend changed the thickness of the PLA fibrils, modified the interface adhesion, and altered the deformation behavior of the PBAT matrix from brittle to ductile. The results proved that CECLs react selectively with PBAT, PLA, and their interface. Furthermore, the reactions of CECLs with PBAT/PLA induced by the processing depended on the deformation directions (ED and TD), thus resulting in further non-uniformities of blown extrusion films.
Cathepsin K (CatK) is a target for the treatment of osteoporosis, arthritis, and bone metastasis. Peptidomimetics with a cyanohydrazide warhead represent a new class of highly potent CatK inhibitors; however, their binding mechanism is unknown. We investigated two model cyanohydrazide inhibitors with differently positioned warheads: an azadipeptide nitrile Gü1303 and a 3-cyano-3-aza-β-amino acid Gü2602. Crystal structures of their covalent complexes were determined with mature CatK as well as a zymogen-like activation intermediate of CatK. Binding mode analysis, together with quantum chemical calculations, revealed that the extraordinary picomolar potency of Gü2602 is entropically favoured by its conformational flexibility at the nonprimed-primed subsites boundary. Furthermore, we demonstrated by live cell imaging that cyanohydrazides effectively target mature CatK in osteosarcoma cells. Cyanohydrazides also suppressed the maturation of CatK by inhibiting the autoactivation of the CatK zymogen. Our results provide structural insights for the rational design of cyanohydrazide inhibitors of CatK as potential drugs.
The white ground crater by the Phiale Painter (450–440 BC) exhibited in the “Pietro Griffo” Archaeological Museum in Agrigento (Italy) depicts two scenes from Perseus myth. The vase is of utmost importance to archaeologists because the figures are drawn on a white background with remarkable daintiness and attention to detail. Notwithstanding the white ground ceramics being well documented from an archaeological and historical point of view, doubts concerning the compositions of pigments and binders and the production technique are still unsolved. This kind of vase is a valuable rarity, the use of which is documented in elitist funeral rituals. The study aims to investigate the constituent materials and the execution technique of this magnificent crater. The investigation was carried out using non-destructive and non-invasive techniques in situ. Portable X-ray fluorescence and Fourier-transform total reflection infrared spectroscopy complemented the use of visible and ultraviolet light photography to get an overview and specific information on the vase. The XRF data were used to produce false colour maps showing the location of the various elements detected, using the program SmART_scan. The use of gypsum as the material for the white ground is an important result that deserves to be further investigated in similar vases.
The synthesis and characterization of a new class of 1,2,4-oxadiazolylpyridinium as a cationic scaffold for fluorinated ionic liquid crystals is herein described. A series of 12 fluorinated heterocyclic salts based on a 1,2,4-oxadiazole moiety, connected through its C(5) or C(3) to an N-alkylpyridinium unit and a perfluoroheptyl chain, differing in the length of the alkyl chain and counterions, has been synthesized. As counterions iodide, bromide and bis(trifluoromethane)sulfonimide have been considered. The synthesis, structure, and liquid crystalline properties of these compounds are discussed on the basis of the tuned structural variables. The thermotropic properties of this series of salts have been investigated by differential scanning calorimetry and polarized optical microscopy. The results showed the existence of an enantiotropic mesomorphic smectic liquid crystalline phase for six bis(trifluoromethane)sulfonimide salts.
The molecular weight properties of lignins are one of the key elements that need to be analyzed for a successful industrial application of these promising biopolymers. In this study, the use of 1H NMR as well as diffusion-ordered spectroscopy (DOSY NMR), combined with multivariate regression methods, was investigated for the determination of the molecular weight (Mw and Mn) and the polydispersity of organosolv lignins (n = 53, Miscanthus x giganteus, Paulownia tomentosa, and Silphium perfoliatum). The suitability of the models was demonstrated by cross validation (CV) as well as by an independent validation set of samples from different biomass origins (beech wood and wheat straw). CV errors of ca. 7–9 and 14–16% were achieved for all parameters with the models from the 1H NMR spectra and the DOSY NMR data, respectively. The prediction errors for the validation samples were in a similar range for the partial least squares model from the 1H NMR data and for a multiple linear regression using the DOSY NMR data. The results indicate the usefulness of NMR measurements combined with multivariate regression methods as a potential alternative to more time-consuming methods such as gel permeation chromatography.
This study investigates the effects of four multifunctional chain-extending cross-linkers (CECL) on the processability, mechanical performance, and structure of polybutylene adipate terephthalate (PBAT) and polylactic acid (PLA) blends produced using film blowing technology. The newly developed reference compound (M·VERA® B5029) and the CECL modified blends are characterized with respect to the initial properties and the corresponding properties after aging at 50 °C for 1 and 2 months. The tensile strength, seal strength, and melt volume rate (MVR) are markedly changed after thermal aging, whereas the storage modulus, elongation at the break, and tear resistance remain constant. The degradation of the polymer chains and crosslinking with increased and decreased MVR, respectively, is examined thoroughly with differential scanning calorimetry (DSC), with the results indicating that the CECL-modified blends do not generally endure thermo-oxidation over time. Further, DSC measurements of 25 µm and 100 µm films reveal that film blowing pronouncedly changes the structures of the compounds. These findings are also confirmed by dynamic mechanical analysis, with the conclusion that tris(2,4-di-tert-butylphenyl)phosphite barely affects the glass transition temperature, while with the other changes in CECL are seen. Cross-linking is found for aromatic polycarbodiimide and poly(4,4-dicyclohexylmethanecarbodiimide) CECL after melting of granules and films, although overall the most synergetic effect of the CECL is shown by 1,3-phenylenebisoxazoline.
The analysis of used engine oils from industrial engines enables the study of engine wear and oil degradation in order to evaluate the necessity of oil changes. As the matrix composition of an engine oil strongly depends on its intended application, meaningful diagnostic oil analyses bear considerable challenges. Owing to the broad spectrum of available oil matrices, we have evaluated the applicability of using an internal standard and/or preceding sample digestion for elemental analysis of used engine oils via inductively coupled plasma optical emission spectroscopy (ICP OES). Elements originating from both wear particles and additives as well as particle size influence could be clearly recognized by their distinct digestion behaviour. While a precise determination of most wear elements can be achieved in oily matrix, the measurement of additives is performed preferably after sample digestion. Considering a dataset of physicochemical parameters and elemental composition for several hundred used engine oils, we have further investigated the feasibility of predicting the identity and overall condition of an unknown combustion engine using the machine learning system XGBoost. A maximum accuracy of 89.6% in predicting the engine type was achieved, a mean error of less than 10% of the observed timeframe in predicting the oil running time and even less than 4% for the total engine running time, based purely on common oil check data. Furthermore, obstacles and possibilities to improve the performance of the machine learning models were analysed and the factors that enabled the prediction were explored with SHapley Additive exPlanation (SHAP). Our results demonstrate that both the identification of an unknown engine as well as a lifetime assessment can be performed for a first estimation of the actual sample without requiring meticulous documentation.
Multiwalled carbon nanotubes (MWCNTs) were easily and efficiently functionalised with highly cross-linked polyamines. The radical polymerisation of two bis-vinylimidazolium salts in the presence of pristine MWCNTs and azobisisobutyronitrile (AIBN) as a radical initiator led to the formation of materials with a high functionalisation degree. The subsequent treatment with sodium borohydride gave rise to the reduction of imidazolium moieties with the concomitant formation of secondary and tertiary amino groups. The obtained materials were characterised by thermogravimetric analysis (TGA), elemental analysis, solid state 13C-NMR, Fourier-transform infrared spectroscopy (FT-IR), transmission electron microscopy (TEM), potentiometric titration, and temperature programmed desorption of carbon dioxide (CO2-TPD). One of the prepared materials was tested as a heterogeneous base catalyst in C–C bond forming reactions such as the Knoevenagel condensation and Henry reaction. Furthermore, two examples concerning a sequential one-pot approach involving two consecutive reactions, namely Knoevenagel and Michael reactions, were reported.
Development of colored surfaces by formation of nano-structured aggregates is a widely used strategy in nature to color lightweight structures (e.g. butterflies) without the use of dye pigments. The deposition of nanoscale particles mimics nature in it’s approach coloring surfaces. This work presents sol-gel modification of cellulose surfaces used to form a template for growth of Cu/Cu2O core-shell particles with defined size-distributions. Besides improving the adhesion of the deposited particulate material, the sol-gel matrix serves as a template for the control of particle sizes of the Cu/Cu2O structures, and as a consequence of particle size variation the surface color is tunable. As an example, red color was achieved with an average particle size of 35 nm, and shifts gradually to blue appearance when particles have grown to 80 nm on the sol-gel modified fabric. The copper concentration on representative fabrics is kept low to avoid modifying the textile characteristics and were all in the range of 150–170 mg per g of cellulose material. As a result of copper deposition on the surface of the material, the cellulose fabric also became electrically conductive. Remarkably, the electrical conductivity was found to be dependent on the average particle sizes of the deposits and thus related to the change in observed color. The generation of color by growth of nano-sized particles on sol-gel templates provides a highly promising approach to stain surfaces by physical effects without use of synthetic colorants, which opens a new strategy to improve environmental profile of coloration.
In dieser vorliegenden Arbeit wurde der photolytische und photokatalytische Abbau von Lignin untersucht. Eine Charakterisierung des verwendeten Photoreaktors wurde mittels Kalium-Ferrioxalat-Aktinometrie durchgeführt. Zur Analyse der abgebauten Lignine wurde eine Optimierung einer bereits bestehenden Methode zur Bestimmung des Hydroxylgehaltes erarbeitet. Die Bestimmung der Hydroxylgehalte erfolgte demnach bei Raumtemperatur nach einer Acetylierungsdauer von 72 h und zeigte eine Abnahme der Hydroxylgehalte mit andauernder UV-Bestrahlung. Selbige Beobachtung konnte mit Hilfe der ATR-IR-Spektroskopie gemacht werden. Zusätzlich konnte die Bildung von Carbonsäuren und der Abbau von aromatischen Strukturen detektiert werden. Der Abbau aromatischer Strukturen konnte ebenfalls durch UV-VIS-Spektroskopie gezeigt werden. Eine Vermutung, dass es sich bei dem Abbauprozess um einen oxidativen Mechanismus handelt, konnte mit dem Abbau von Hydroxylgruppen über eine Bildung von Carbonsäuren zu Kohlenstoffdioxid bestätigt werden. Eine Freisetzung von Kohlenstoffdioxid konnte durch eine Bestimmung des IC festgestellt werden. Die Ergebnisse der Gel-Permeations-Chromatographie zusammen mit einer TOC-Analyse zeigen einen Abbau der molaren Masse des Lignins auf. Es konnten Fragmente mit einer Molmasse ähnlich der Monomere des Lignins gefunden werden. Der eingesetzte Photokatalysator wurde via Röntgenbeugung untersucht und konnte als das hoch photokatalytisch aktive P25 von Degussa identifiziert werden. Trotz des Einsatzes verschiedener Katalysatorkonzentrationen in einem Bereich von 0-0,5 g L^(-1) konnte kein Einfluss des Photokatalysators auf den Abbauprozess des Lignins beobachtet werden.
In der vorliegenden Arbeit wurde Kraft-Lignin als Makromonomer für die Synthese von thermoplastischen Polyurethanen mit hoher molarer Masse durch acide Präzipitation aus Schwarzlauge isoliert. Die Charakterisierung des Rohstoffes bezüglich seiner Ausgangsmolmasse erfolgte mittels Gel-Permeations-Chromatographie mit Polystyren-Polymerstandard, welche sich als sehr hilfreiche Analysemethode erwies. Da das Kraft-Lignin die klassische Polyolkomponente bei der Synthese von Polyurethanen ersetzen sollte, war es notwendig, den Hydroxylgehalt des Kraft-Lignins zu bestimmen. Für diesen Zweck wurde eine bereits etablierte Prozedur zur nasschemischen Bestimmung des Hydroxylgehaltes von Polyolen für die Synthese von Polyurethanen einer Adaption unterzogen. Es wurde die Reaktionsdauer bei der Acetylierung des Kraft-Lignins variiert. Das Ergebnis war, dass die Messgenauigkeit durch eine Erhöhung der Reaktionsdauer von 1 h auf 3 h drastisch von 25,5 % auf 3,6 % reduziert werden konnte. Um abschätzen zu können, ob die erzielte Messgenauigkeit im Rahmen einer nasschemischen Prozedur mit manueller Titration liegt, wurden zusätzlich die Hydroxylgehalte von Ethandiol und Saccharose bestimmt. Diese dienten als Referenzsubstanz mit definierten und bekannten Hydroxylgehalten. Die Ermittlung der Hydroxylgehalte mit diesen Substanzen ergab für Ethandiol eine Messgenauigkeit von 2,2 % und für Saccharose eine Messgenauigkeit von 1,4 %. Eine Messgenauigkeit von 3,6 % ist in Anbetracht des Zeitaufwandes akzeptabel.
Für die Synthese von thermoplastischen Polyurethanen wurde Kraft-Lignin mit Methylendiphenyldiisocyanat in Dimethylacetamid mit Zinnoktoat als Katalysator zur Reaktion gebracht. Es wurde das NCO/OH-Verhältnis und die Reaktionsdauer variiert. Die Analyse der synthetisierten Polyurethane erfolgte mittels Ubbelohde-Kapillarviskosimetrie, Fourier-Transformations-Infrarotspektroskopie und Schmelzpunktbestimmung. Die FTIR-Spektren bestätigte eine erfolgreiche Synthese von Polyurethanen aus Kraft-Lignin und Methylendiphenyldiisocyanat und zeigte, dass die Variation des NCO/OH-Verhältnisses und der Reaktionsdauer keinerlei Einflüsse auf die chemische Grundstruktur des Polyurethans hat. Die Ubbelohde-Kapillarviskosimetrie belegte die thermoplastischen Eigenschaften des synthetisierten Polyurethans, die sich in einem thermoplastischen Nassprozess verarbeiten lassen. Sie zeigte auch die Abhängigkeit der Molmasse der synthetisierten Polyurethane von der Reaktionsdauer und vom NCO/OH-Verhältnis. So steigt die Molmasse des Polyurethans mit steigender Reaktionsdauer und sinkendem NCO/OH-Verhältnis. Letztere Beobachtung ist sogar praktisch hinsichtlich der gesundheitsgefährdenden Eigenschaft von Isocyanaten, da so der Einsatz von Isocyanaten reduziert werden kann. Um die schmelzflüssige Verarbeitbarkeit des synthetisierten Polyurethans zu untersuchen, wurden die Schmelzpunkte der Polymere bestimmt. Es konnte in einem Temperaturbereich von 25 °C-410 °C keine Aggregatzustandsänderung, sondern lediglich eine Zersetzungsreaktion beobachtet werden.
Diese Arbeit beschäftigt sich mit der Entwicklung eines, für die kontrollierte Freisetzung hydrophiler Wirkstoffe geeigneten, Verkapselungssystems mit dem Ziel die Freisetzung osteospezifischer P2-Liganden zu verzögern, um bei der Behandlung von Knochendefekten kritischer Größe die Bildung neuen Knochengewebes zu gewährleisten. Hierfür werden, unter Anwendung der immersiven Layer-by-Layer-Beschichtung, mit den Modell-Substanzen Adenosintriphosphat und Suramin versetzte, Alginat sowie κ-Carrageen-Kapseln mit Chitosan und Lignosulfonat beschichtet und auf ihr Freisetzungsverhalten hin untersucht.
Im Rahmen der Arbeit wurde Kraft-Lignin mit Natriumsulfit demethyliert, um den Gehalt an aromatischen Hydroxygruppen zu erhöhen und damit die Reaktivität des Lignins in Bezug auf Polyurethan-Synthesen zu erhöhen. Variiert wurden die Demethylierungstemperatur (72°C, 90°C) sowie der pH-Wert zur Isolierung des Kraft-Lignins (pH 2, 3, 4 und 5). Die Analyse der demethylierten Proben erfolgte mittels differentieller UV-Spektroskopie und der OH-Gehaltbestimmung via automatischer Titration (angelehnt an ISO 14900:2001(E)). Weitere Untersuchungen umfassten Löslichkeitstests sowie Strukturanalysen via FTIR- und UV/Vis-Spektroskopie.
Pozzolanic properties of Pennisetum purpureum grass ash were tested on Portland cement. Results show that the ash can be blended with cements without compromising binding strength of the cement. It was found that Portland cement could be blended with Pennisetum purpureum up to a ratio of 3:2 compromising compressive strength of mortar.Mortar with lower cement replacement took longer to set as evidenced by lower compressive strength within the 28-day aging time. Mortar with higher cement replacement had lower water absorption capacity, an indication that the test pozzolan was of smaller particulate size. XRF analysis and the FTIR spectrum showed that the ash has a higher content of silica. The XRD pattern of the ash showed that the ash was predominantly amorphous. SEM images showed that the ash produced at 600 o C had residual carbon material.
In an effort to assist researchers in choosing basis sets for quantum mechanical modeling of molecules (i.e. balancing calculation cost versus desired accuracy), we present a systematic study on the accuracy of computed conformational relative energies and their geometries in comparison to MP2/CBS and MP2/AV5Z data, respectively. In order to do so, we introduce a new nomenclature to unambiguously indicate how a CBS extrapolation was computed. Nineteen minima and transition states of buta-1,3-diene, propan-2-ol and the water dimer were optimized using forty-five different basis sets. Specifically, this includes one Pople (i.e. 6-31G(d)), eight Dunning (i.e. VXZ and AVXZ, X=2-5), twenty-five Jensen (i.e. pc-n, pcseg-n, aug-pcseg-n, pcSseg-n and aug-pcSseg-n, n=0-4) and nine Karlsruhe (e.g. def2-SV(P), def2-QZVPPD) basis sets. The molecules were chosen to represent both common and electronically diverse molecular systems. In comparison to MP2/CBS relative energies computed using the largest Jensen basis sets (i.e. n=2,3,4), the use of smaller sizes (n=0,1,2 and n=1,2,3) provides results that are within 0.11--0.24 and 0.09-0.16 kcal/mol. To practically guide researchers in their basis set choice, an equation is introduced that ranks basis sets based on a user-defined balance between their accuracy and calculation cost. Furthermore, we explain why the aug-pcseg-2, def2-TZVPPD and def2-TZVP basis sets are very suitable choices to balance speed and accuracy.
Due to global ecological and economic challenges that have been correlated to the transition from fossil-based to renewable resources, fundamental studies are being performed worldwide to replace fossil fuel raw materials in plastic production. One aspect of current research is the development of lignin-derived polyols to substitute expensive fossil-based polyol components for polyurethane and polyester production. This article describes the synthesis of bioactive lignin-based polyurethane coatings using unmodified and demethylated Kraft lignins. Demethylation was performed to enhance the reaction selectivity toward polyurethane formation. The antimicrobial activity was tested according to a slightly modified standard test (JIS Z 2801:2010). Besides effects caused by the lignins themselves, triphenylmethane derivatives (brilliant green and crystal violet) were used as additional antimicrobial substances. Results showed increased antimicrobial capacity against Staphylococcus aureus. Furthermore, the coating color could be varied from dark brown to green and blue, respectively.
Lignocellulose feedstock (LCF) provides a sustainable source of components to produce bioenergy, biofuel, and novel biomaterials. Besides hard and soft wood, so-called low-input plants such as Miscanthus are interesting crops to be investigated as potential feedstock for the second generation biorefinery. The status quo regarding the availability and composition of different plants, including grasses and fast-growing trees (i.e., Miscanthus, Paulownia), is reviewed here. The second focus of this review is the potential of multivariate data processing to be used for biomass analysis and quality control. Experimental data obtained by spectroscopic methods, such as nuclear magnetic resonance (NMR) and Fourier-transform infrared spectroscopy (FTIR), can be processed using computational techniques to characterize the 3D structure and energetic properties of the feedstock building blocks, including complex linkages. Here, we provide a brief summary of recently reported experimental data for structural analysis of LCF biomasses, and give our perspectives on the role of chemometrics in understanding and elucidating on LCF composition and lignin 3D structure.
This study presents a microindentation system which allows spatially resolved local as well as bulk viscoelastic material information to be obtained within one instrument. The microindentation method was merged with dynamic mechanical analysis (DMA) for a tungsten cone indenter. Three tungsten cone indenters were investigated: tungsten electrode, tungsten electrode + 2% lanthanum, and tungsten electrode + rare earth elements. Only the tungsten electrode + 2% lanthanum indenter showed the sinusoidal response, and its geometry remained unaffected by the repeated indentations. Complex moduli obtained from dynamic microindentation for high-density polyethylene, polybutylene terephthalate, polycarbonate, and thermoplastic polyurethane are in agreement with the literature. Additionally, by implementing a specially developed x-y-stage, this study showed that dynamic microindentation with a tungsten cone indenter was an adequate method to determine spatially resolved local viscoelastic surface properties.
Due to increased emissions of palladium nanoparticles in recent years, it is important to develop analytical techniques to characterize these particles. The synthesis of defined and stable particles plays a key role in this process, as there are not many materials commercially available yet which could act as reference materials. Polyvinylpyrrolidone- (PVP-) stabilized palladium nanoparticles were synthesized through the reduction of palladium chloride by tetraethylene glycol (TEG) in the presence of KOH. Four different methods were used for particle size analysis of the palladium nanoparticles. Palladium suspensions were analyzed by scanning electron microscopy (SEM), small angle X-ray scattering (SAXS), single-particle ICP-MS (SP-ICP-MS), and X-ray diffraction (XRD). Secondary particles between 30 nm and 130 nm were detected in great compliance with SAXS and SP-ICP-MS. SEM analysis showed that the small particulates tend to form agglomerates.