TY - JOUR A1 - Stojanović, Ivan A1 - Židov, Bruno A1 - Travkova, Oksana A1 - Grigoriev, Dmitry T1 - Enhanced protective performance of waterborne, microcontainers-doped coatings in harsh environments JF - Progress in organic coatings : an international journal N2 - In this study, the corrosion inhibitors Zinc oleate and 8-Hydroxyquinoline were successfully encapsulated using an interfacial polyaddition method. As such they were dispersed at different concentrations within the waterborne coating matrix. The resulting composite coatings were applied to the low carbon steel substrates. Successful synthesis and morphological characteristics of microcontainers loaded with inhibitors were confirmed using various characterization techniques. Scanning electron microscopy, dynamic light scattering, and thermogravimetric measurements are techniques used to define the surface, dimensional, and dispersive characteristics of containers, and the share of encapsulated inhibitors. The release study defined the discharge kinetics of the corrosion inhibitor from the microcontainers dispersed freely in an aqueous medium. Electrochemical impedance spectroscopy was used to determine the anticorrosive performance of the samples continuously exposed to various corrosive environments of salt and humidity chambers and NaCl solution. Special emphasis was placed on adhesion testing and visual observations during the exposure period. Significant improvements have been noted in terms of corrosion resistance, which, however, depend on the type of inhibitor used, the concentration of the containers embedded in the coating matrix and on the characteristics of the corrosive environment. KW - Self-protecting coatings KW - Interfacial polyaddition KW - Inhibitor loaded KW - microcontainers KW - Corrosion inhibitors Y1 - 2021 U6 - https://doi.org/10.1016/j.porgcoat.2021.106273 SN - 0300-9440 SN - 1873-331X VL - 157 PB - Elsevier Science CY - Amsterdam [u.a.] ER - TY - JOUR A1 - Gahlaut, Shashank K. A1 - Pathak, Anisha A1 - Gupta, Banshi D. T1 - Recent advances in silver nanostructured substrates for plasmonic sensors JF - Biosensors : open access journal N2 - Noble metal nanostructures are known to confine photon energies to their dimensions with resonant oscillations of their conduction electrons, leading to the ultrahigh enhancement of electromagnetic fields in numerous spectroscopic methods. Of all the possible plasmonic nanomaterials, silver offers the most intriguing properties, such as best field enhancements and tunable resonances in visible-to-near infrared regions. This review highlights the recent developments in silver nanostructured substrates for plasmonic sensing with the main emphasis on surface plasmon resonance (SPR) and surface-enhanced Raman spectroscopy (SERS) over the past decade. The main focus is on the synthesis of silver nanostructured substrates via physical vapor deposition and chemical synthesis routes and their applications in each sensing regime. A comprehensive review of recent literature on various possible silver nanostructures prepared through these methodologies is discussed and critically reviewed for various planar and optical fiber-based substrates. KW - silver KW - plasmonics KW - sensors KW - surface-enhanced Raman spectroscopy KW - surface-enhanced fluorescence KW - surface-enhanced infrared spectroscopy Y1 - 2022 U6 - https://doi.org/10.3390/bios12090713 SN - 2079-6374 VL - 12 IS - 9 PB - MDPI CY - Basel ER - TY - JOUR A1 - Diehn, Sabrina Maria A1 - Schlaad, Helmut A1 - Kneipp, Janina T1 - Multivariate imaging for fast evaluation of in situ dark field microscopy hyperspectral data JF - Molecules : a journal of synthetic chemistry and natural product chemistry N2 - Dark field scattering microscopy can create large hyperspectral data sets that contain a wealth of information on the properties and the molecular environment of noble metal nanoparticles. For a quick screening of samples of microscopic dimensions that contain many different types of plasmonic nanostructures, we propose a multivariate analysis of data sets of thousands to several hundreds of thousands of scattering spectra. By using non-negative matrix factorization for decomposing the spectra, components are identified that represent individual plasmon resonances and relative contributions of these resonances to particular microscopic focal volumes in the mapping data sets. Using data from silver and gold nanoparticles in the presence of different molecules, including gold nanoparticle-protein agglomerates or silver nanoparticles forming aggregates in the presence of acrylamide, plasmonic properties are observed that differ from those of the original nanoparticles. For the case of acrylamide, we show that the plasmon resonances of the silver nanoparticles are ideally suited to support surface enhanced Raman scattering (SERS) and the two-photon excited process of surface enhanced hyper Raman scattering (SEHRS). Both vibrational tools give complementary information on the in situ formed polyacrylamide and the molecular composition at the nanoparticle surface. KW - localized surface plasmon resonances KW - gold nanoparticles KW - silver nanoparticles KW - dark field microscopy KW - acrylamide KW - hyperspectral imaging KW - non-negative matrix factorization KW - surface-enhanced Raman scattering (SERS) KW - surface-enhanced hyper Raman scattering (SEHRS) Y1 - 2022 U6 - https://doi.org/10.3390/molecules27165146 SN - 1420-3049 VL - 27 IS - 16 PB - MDPI CY - Basel ER - TY - JOUR A1 - Tarazona, Natalia A. A1 - Wei, Ren A1 - Brott, Stefan A1 - Pfaff, Lara A1 - Bornscheuer, Uwe T. A1 - Lendlein, Andreas A1 - Machatschek, Rainhard T1 - Rapid depolymerization of poly(ethylene terephthalate) thin films by a dual-enzyme system and its impact on material properties JF - Chem Catalysis N2 - Enzymatic hydrolysis holds great promise for plastic waste recycling and upcycling. The interfacial catalysis mode, and the variability of polymer specimen properties under different degradation conditions, add to the complexity and difficulty of understanding polymer cleavage and engineering better biocatalysts. We present a systemic approach to studying the enzyme-catalyzed surface erosion of poly(ethylene terephthalate) (PET) while monitoring/controlling operating conditions in real time with simultaneous detection of mass loss and changes in viscoelastic behavior. PET nanofilms placed on water showed a porous morphology and a thicknessdependent glass transition temperature (T-g) between 40 degrees C and 44 degrees C, which is >20 degrees C lower than the T-g of bulk amorphous PET. Hydrolysis by a dual-enzyme system containing thermostabilized variants of Ideonella sakaiensis PETase and MHETase resulted in a maximum depolymerization of 70% in 1 h at 50 degrees C. We demonstrate that increased accessible surface area, amorphization, and T-g reduction speed up PET degradation while simultaneously lowering the threshold for degradation-induced crystallization. Y1 - 2022 U6 - https://doi.org/10.1016/j.checat.2022.11.004 SN - 2667-1093 SN - 2667-1107 VL - 2 IS - 12 SP - 3573 EP - 3589 PB - Cell Press CY - Cambridge ER - TY - JOUR A1 - Rothe, Martin A1 - Zhao, Yuhang A1 - Halim, Henry A1 - Lu, Yan A1 - Benson, Oliver T1 - Spatial mapping of bleaching in a metal-organic plasmon converter JF - Optics continuum N2 - Hybrid nanophotonic elements, fabricated by organic and inorganic materials, are going to be key components of modern devices. Coupled systems of photoemitters with a plasmonic waveguide serve the demand for nanoscopic frequency converters. However, processes like the degradation of the photoemitters via photobleaching occur and need to be monitored and controlled, to realize future successful devices. We introduce a hybrid perylene-diimide / silver nanowire as plasmon frequency converter. A versatile method is presented to monitor and analyze the bleaching process. It is based on a time series of photoluminescence images, during the operation of a single converter. An analytical model is applied on the data and unveils that the photobleaching rate is constant and independent of the operation of the plasmon converter. Y1 - 2022 U6 - https://doi.org/10.1364/OPTCON.454911 SN - 2770-0208 VL - 1 IS - 8 SP - 1730 EP - 1740 PB - Optica Publishing Group CY - Washington ER - TY - JOUR A1 - Chemura, Sitshengisiwe A1 - Schrumpf, Tim A1 - Günter, Christina A1 - Kumke, Michael Uwe T1 - Ceria nanomaterials containing ytterbium BT - low and high concentration – luminescence analyzed in the near infrared region JF - RSC Advances : an international journal to further the chemical sciences N2 - Lanthanide based ceria nanomaterials are important practical materials due to the redox properties that are useful in the avenues pertaining to technology and life sciences. Sub 10 nm spherical and highly monodisperse Ce1−xYbxO2−y (0.04 ≤ x ≤ 0.22) nanoparticles were synthesized by thermal decomposition, annealed separately at 773 K and 1273 K for 2 hours and characterized. Elemental mapping for Yb3+ doped ceria nanoparticles shows homogeneous distribution of Yb3+ atoms in the ceria with low Yb3+ content annealed at 773 K and 1273 K for 2 hours. However, clusters are observed for 773 K annealed ceria samples with high concentration of Yb3+. These clusters are not detected in 1273 K annealed nanomaterials. Introducing small amounts of Yb3+ ions into the ceria lattice as spectroscopic probes can provide detailed information about the atomic structure and local environments allowing the monitoring of small structural changes, such as clustering. The emission spectra observed at room temperature and at 4 K have a manifold of bands that corresponds to the 2F5/2 → 2F7/2 transition of Yb3+ ions. Some small shifts are observed in the Stark splitting pattern depending on the sample and the annealing conditions. The deconvolution by PARAFAC analysis yielded luminescence decay kinetics as well as the associated luminescence spectra of three species for each of the low Yb3+ doped ceria samples annealed at 773 K and one species for the 1273 K annealed samples. However, the ceria samples with high concentration of Yb3+ annealed at the two temperatures showed only one species with lower decay times as compared to the low Yb3+ doped ceria samples. Y1 - 2023 U6 - https://doi.org/10.1039/D3RA06868D SN - 2046-2069 VL - 13 IS - 50 SP - 35445 EP - 35456 PB - RSC Publishing CY - London ER - TY - JOUR A1 - Lehnen, Anne-Catherine A1 - Kurki, Jan A. M. A1 - Hartlieb, Matthias T1 - The difference between photo-iniferter and conventional RAFT polymerization BT - high livingness enables the straightforward synthesis of multiblock copolymers JF - Polymer Chemistry N2 - Photo-iniferter (PI)-RAFT polymerization, the direct activation of chain transfer agents via light, is a fascinating polymerization technique, as it overcomes some restriction of conventional RAFT polymerization. As such, we elucidated the role of reversible deactivation in this context using a monomer-CTA pair with low chain transfer capabilities. Tests with varying targeted degrees of polymerization (DP) or monomer concentrations revealed no significant improvement of polymerization control using the PI-process. Control can however be achieved via slow monomer addition, increasing the number of activation/deactivation events per monomer addition. More importantly, the livingness of the polymerization was found to be extraordinarily high, enabling the straightforward and rapid synthesis of multiblock copolymers with up to 20 blocks and a high number of repeating units per block (DP = 25-100) maintaining an overall excellent definition (M-n = 90 300 g mol(-1), D = 1.29). This study highlights the enormous potential of PI-RAFT polymerization for the synthesis of polymeric materials. Y1 - 2022 U6 - https://doi.org/10.1039/d1py01530c SN - 1759-9954 SN - 1759-9962 VL - 13 IS - 11 SP - 1537 EP - 1546 PB - Royal Society of Chemistry CY - Cambridge ER - TY - JOUR A1 - Hermanns, Jolanda A1 - Kunold, Helen T1 - Mechanism comics as a task in a written exam in organic chemistry for pre-service chemistry teachers JF - Chemistry teacher international : best practices in chemistry education N2 - In this paper, we describe and evaluate a study on the use of mechanism comics for writing solutions to a task in a written exam for the course "Organic Chemistry I for Pre-Service Chemistry Teachers." The students had to design a reaction mechanism for a reaction that was unknown to them and write captions explaining every step of their reaction mechanism. The students' work was evaluated using the method of qualitative content analysis in four rounds by both authors. The majority of the captions were coded as "descriptive" and only a minority as "causal." This means that the students mostly described "what" happened, but seldom "why" this happened. Implicit electron movement was also described more often than explicit electron movement. The majority of the captions were technically correct. In summary, the students were capable of designing and describing a reaction mechanism for a previously unknown reaction. The quality of their reasoning could be improved, however. In the new course, the quality of students' mechanistic reasoning and then especially their explanations of "why" mechanistic steps occur will be given much clearer emphasis. KW - concepts KW - mechanistic reasoning KW - organic chemistry KW - pre-service chemistry teachers KW - writing-to-learn Y1 - 2022 U6 - https://doi.org/10.1515/cti-2021-0035 SN - 2569-3263 VL - 4 IS - 3 SP - 259 EP - 269 PB - De Gruyter CY - Berlin ER - TY - JOUR A1 - Titov, Evgenii T1 - Effect of conformational disorder on exciton states of an azobenzene aggregate JF - Physical chemistry, chemical physics : a journal of European Chemical Societies N2 - Azobenzene is a prototypical molecular photoswitch, widely used to trigger a variety of transformations at different length scales. In systems like self-assembled monolayers or micelles, azobenzene chromophores may interact with each other, which gives rise to the emergence of exciton states. Here, using first-principles calculations, we investigate how conformational disorder (induced, e.g., by thermal fluctuations) affects localization of these states, on an example of an H-type azobenzene tetramer. We find that conformational disorder leads to (partial) exciton localization on a single-geometry level, whereas ensemble-averaging results in a delocalized picture. The pi pi* and n pi* excitons at high and low temperatures are discussed. Y1 - 2022 U6 - https://doi.org/10.1039/d2cp02774g SN - 1463-9076 SN - 1463-9084 VL - 24 IS - 39 SP - 24002 EP - 24006 PB - Royal Society of Chemistry CY - Cambridge ER - TY - JOUR A1 - Sand, Patrick A1 - Schmidt, Bernd T1 - Orthogonal arylation of a diene-sulfonamide using cationic transition metal catalysts JF - European journal of organic chemistry N2 - The regioselectivity of two mechanistically distinct alkenylation reactions catalyzed by in situ-formed cationic transition metal complexes was studied using N-allyl-N-phenylethenesulfonamide as a model compound. Orthogonal selectivity was observed for the Ru-catalyzed C-H-activating alkenylation with acetanilides, which occurs preferentially at the electron deficient double bond, and for a Pd-catalyzed Heck-type coupling with arene diazonium salts, which occurs preferentially at the more electron rich double bond of the N-allyl substituent. KW - arenes KW - C-H activation KW - palladium KW - ruthenium KW - sulfonamides Y1 - 2022 U6 - https://doi.org/10.1002/ejoc.202201336 SN - 1434-193X SN - 1099-0690 VL - 2022 IS - 47 PB - Wiley-VCH CY - Weinheim ER -