PEO-b-PNBA in-situ functionalized mesoporous silica films and their light- and pH-controlled ionic mesopore accessibility

Multistimuli-responsive, in-situ functionalized mesoporous silica films were fabricated by evaporation-induced self-assembly through physical entrapment of the functional template poly(ethylene oxide)-b-poly(2-nitrobenzyl acrylate) (PEO-b-PNBA). The light-cleavable and pH-responsive block copolymer PEO-b-PNBA simultaneously serves as structure-directing agent and for in-situ polymer functionalization of the generated mesopore space. The use of different PEO-b-PNBA compositions results in highly filled hybrid mesoporous silica films with different pore sizes, porosity, and polymer chain sequence within the mesopores. Based on these structural variations and the polymer chain sequence the ionic permselectivity of the silica-polymer hybrid thin films is adjusted. The side chains of the template PNBA block can be deprotected upon irradiation, hereby releasing pH-responsive carboxylic acid groups. The irradiation energy and irradiation time-dependent deprotection allows gradually controlled charge regulation in mesopores. This approach of in-situ functionalization using multistimuli-responsive PEO-b-PNBA block copolymers facilitates the fabrication of multi-responsive hybrid mesoporous silica films and bears high potential for the production of complex, hierarchical, multifunctional mesoporous materials. This fabrication method including direct functionalization of mesoporous structures is of high interest for many applications based on controlled molecular transport in nanoscale pores, such as sensing, separation, or catalysis

Self-Driven Fluid Imbibition of Salt Solutions into Mesoporous Films

Fluid water imbibition into nanoscale porous materials is important in nature and technology and has been shown to follow Lucas-Washburn behavior. Looking at drop imbibition into nanoscale porous films the imbibition reaches a steady state governed by capillary imbibition and evaporation which is reflected in a constant imbibition length. This imbibition length in a steady state depends on the porous structure as well as on the material’s wettability and the fluid evaporation rate, for example. As the presence of salts affects these parameters, the imbibition length is expected to be influenced by the solutes present in the drop. Here, we show the influence of salt presence, salt concentration, and ion type on the fluid imbibition of an aqueous salt solution into mesoporous silica films. We observe, that salts affect the Lucas-Washburn imbibition occurring directly after drop positioning on mesoporous films. Interestingly, the presence of salts also causes a continuous increase of the characteristic imbibition length at longer time scales preventing the formation of a steady state after the initial Lucas-Washburn-like imbibition. We identified a self-amplified fluid pumping mechanism using mesoporous silica films. We attribute this continuous fluid pumping and thus the continuous increase of the imbibition length to the increasing osmotic pressure within mesoporous materials upon constant fluid flow and fluid evaporation. Understanding aqueous salt solution imbibition into mesoporous films is an important aspect e.g. in the context of material exchange between drops through mesoporous films

Simultaneous Bacteria Sensing and On-demand Antimicrobial Peptide Release

A material able to simultaneously sense a bacterial presence and to on-demand release antimicrobial peptides (AMP) in a tunable amount was developed. Simultaneous sensing and release were achieved by the combination of a bacteria-sensing hydrogel with antimicrobial peptide-carrying mesoporous silica particles or coatings. The mesoporous silica with a mesopore diameter of 22 nm was functionalized with a covalently grafted green light-sensitive linker to which antimicrobial peptides were covalently attached. The gelatin-based hydrogel, which contains C14R functionalized mesoporous silica particles, is designed to respond to bacteria presence as it may occur e.g. in a wound's microbiological environment. In the presence of bacteria and 0.1 % trypsin, a protease enzyme simulating bacterial presence, the hydrogel, deposited in a donut shape, undergoes a shape loss as the bacteria cleave cross-linking bonds within the hydrogel. When observing hydrogel shape loss after 2 hours as a readout of a bacterial infection subsequent irradiation triggers the release of antimicrobial peptides on demand with adjustable concentration-time profiles. The sensing and on-demand release are integrated into commercially available wound dressing fabrics demonstrating an application proof-of-concept. Characterization using ATR-IR spectroscopy, TGA, and BCA validate the successful fabrication and release. The H1.6P composite released antimicrobial agents, reaching concentrations of up to 298 μg/mL at pH 7.4 from a 300 μL sample. The efficacy of the released C14R against E. coli BL21(DE3) is illustrated. Overall, the multifunctionality of this approach presents a promising step towards on-demand wound care and thus for reducing side effects and antibiotic resistance

Shining New Light on the Mechanism of Selective Oxidation Catalysis Using Method Development in Transient Spectroscopy

Selective oxidation reactions are some of the most important chemical processes, with enormous economic and environmental contributions. Controlling the selectivity remains the greatest challenge, owing to their complexity, with both parallel and consecutive reaction pathways leading to by-products. Their mode of operation over supported and bulk oxide catalysts has been the subject of debate for decades, largely influenced by phenomenological principles. Recently, direct evidence from transient spectroscopy has provided insight into the dynamical nature of selective oxidation catalysts as well as the actively participating surface species and sites of the catalysts, while highlighting important functions of the supporting structure. This perspective presents the implications of these findings for a scientific understanding of the characteristics of selective oxidation reactions as a basis for rational catalyst design. First, the potential of the transient spectroscopic approach is illustrated based on the available literature on selective oxidation reactions. When moving from supported catalysts to bulk oxide systems with their increased level of structural complexity, additional challenges concerning the determination of structure–performance relationships emerge, but these may be tackled successfully in the future in view of current method development

Correlating spatially resolved catalysis and Raman spectroscopy during CO oxidation over Cu/CeO₂ catalysts

Spatially resolved analysis allows for the development of accurate structure–property correlations in regimes of high catalytic conversion. We report on the novel combination of a compact profile reactor with IR spectroscopy for spatially resolved gas-phase analysis and with Raman spectroscopy for spatially resolved structural analysis. The potential of this combined approach is illustrated for the CO oxidation over low-loaded Cu/CeO₂ catalysts at atmospheric pressure but the use of higher pressures is feasible. Spatially resolved operando Raman spectroscopy of Cu/CeO₂ at 150 °C reveals structural changes directly correlated with the catalytic conversion. With increasing conversion an increase in the consumption of surface lattice oxygen is observed which is accompanied by the formation of oxygen vacancies and ceria reduction. Our mechanistic findings demonstrate the participation of the ceria support in the CO oxidation over low-loaded Cu/CeO₂ catalysts at high conversions. The presented setup provides high versatility for spatially dependent mechanistic analysis of catalysts as a function of varying gas environments and their influence on the structural changes

Amorphous Doped Indium Tin Oxide Thin‐Films by Atomic Layer Deposition.Insights into Their Structural, Electronic and Device Reliability

Thin semiconducting films of magnesium doped indium‐ and tin oxide are prepared by thermal atomic layer deposition (ALD). The metal oxide films are deposited at 200 °C from the precursors trimethylindium, tetrakis(dimethylamido)tin, bis(ethylcyclopentadienyl)magnesium and water as oxidant. These thin‐films are observed to be amorphous by electron microscopy and X‐ray diffraction. However, they exhibited a near‐range atomic order with correlation lengths of up to 10 Å, as demonstrated by high energy total scattering at grazing incidence employing synchrotron radiation. Even minor alterations in composition reveal a significant impact on the thin‐film transistor (TFT) device parameters, due to magnesium's high oxygen binding capability and its ability to inhibit the formation of oxygen vacancies, resulting in a decrease of free charge carriers in the material. Stability tests indicate a device degradation after storage in ambient conditions due to water adsorption on the surface, which could be reversed by an additional annealing step which qualify the films as robust. This studie demonstrate the possibility of employing minor amounts of high band gap oxides such as MgO to manipulate and control the electric behavior of the active channel layer performance in inorganic TFT devices

Tailoring superstructure units for improved oxygen redox activity in Li-rich layered oxide battery’s positive electrodes

The high-voltage oxygen redox activity of Li-rich layered oxides enables additional capacity beyond conventional transition metal (TM) redox contributions and drives the development of positive electrode active materials in secondary Li-based batteries. However, Li-rich layered oxides often face voltage decay during battery operation. In particular, although Li-rich positive electrode active materials with a high nickel content demonstrate improved voltage stability, they suffer from poor discharge capacity. Here, via physicochemical and electrochemical measurements, we investigate the correlation between oxygen redox activity and superstructure units in Li-rich layered oxides, specifically the fractions of LiMn₆ and Ni⁴⁺-stabilized LiNiMn₅ within the TM layer. We prove that an excess of LiNiMn₅ hinders the extraction/insertion of lithium ions during Li metal coin cell charging/discharging, resulting in incomplete oxygen redox activity at a cell potential of about 3.3 V. We also demonstrate that lithium content adjustment could be a beneficial approach to tailor the superstructure units. Indeed, we report an improved oxygen redox reversibility for an optimized Li-rich layered oxide with fewer LiNiMn5 units

Vor 50 Jahren: die erste drittelparitätische Senatssitzung an der Technischen Hochschule Darmstadt

Als 1966 das Hessische Hochschulgesetz (HHG) verabschiedet wurde, brachte die Hessische Landesregierung in Darmstadt einen Stein ins Rollen, der nach turbulenten Zeiten 1970 wieder abrupt zum Stehen kam: In § 6 des HHG wurden alle hessischen Hochschulen aufgefordert, sich eine Satzung zu geben. Diese sollte unter anderem die Zusammensetzung des Senats festlegen. Unter der Leitung von Rektor Dietrich Schultz bildete sich daraufhin an der damaligen TH eine Verfassungskommission, in der neben sieben Hochschullehrern auch ein Assistent und zwei Studierende mitwirkten. Es entstand ein 50-seitiger Entwurf, der dem Senat vorgelegt und nach umfassenden Diskussionen am 28. Juni 1967 verabschiedet wurde

Mutation induced infection waves in diseases like COVID-19

After more than 6 million deaths worldwide, the ongoing vaccination to conquer the COVID-19 disease is now competing with the emergence of increasingly contagious mutations, repeatedly supplanting earlier strains. Following the near-absence of historical examples of the long-time evolution of infectious diseases under similar circumstances, models are crucial to exemplify possible scenarios. Accordingly, in the present work we systematically generalize the popular susceptible-infected-recovered model to account for mutations leading to repeatedly occurring new strains, which we coarse grain based on tools from statistical mechanics to derive a model predicting the most likely outcomes. The model predicts that mutations can induce a super-exponential growth of infection numbers at early times, which self-amplify to giant infection waves which are caused by a positive feedback loop between infection numbers and mutations and lead to a simultaneous infection of the majority of the population. At later stages—if vaccination progresses too slowly—mutations can interrupt an ongoing decrease of infection numbers and can cause infection revivals which occur as single waves or even as whole wave trains featuring alternative periods of decreasing and increasing infection numbers. This panorama of possible mutation-induced scenarios should be tested in more detailed models to explore their concrete significance for specific infectious diseases. Further, our results might be useful for discussions regarding the importance of a release of vaccine-patents to reduce the risk of mutation-induced infection revivals but also to coordinate the release of measures following a downwards trend of infection numbers

Urban megaprojects, nation-state politics and regulatory capitalism in Central and Eastern Europe: The Belgrade Waterfront project

In this paper, we explore how state-led regulatory planning is utilised to push for delivery of an urban megaproject (UMP) in the specific context of post-socialist Central and Eastern Europe. Our focus is on the large-scale brownfield redevelopment project ‘Belgrade Waterfront’ under implementation in the Serbian capital, a joint venture between the Republic of Serbia and Abu Dhabi-based investor Eagle Hills. We show this UMP to be an extreme example of state-led regulatory intervention, characterised by lack of transparency and haste in decision-making processes, all of which serve to prioritise private investors’ interests in project delivery above the principles of representative democracy. Through analysis of legislative and planning documents, expert reports and media coverage from the period between 2012 and 2017, we explore the legislative mechanisms, contractual strategies and modes of governance involved in the project’s delivery. This provides two insights: first, it reveals that, in contrast with the active role of local governments in conceiving entrepreneurial strategies that is often assumed today, in the case of Belgrade Waterfront, the national government has instead played the decisive role; second, it shows how modifications to national law were instrumental in defining public interest, in enabling certain types of contracts to become technically legal, and in minimising risks for the private investor. We conclude by highlighting the need to further conceptualise nation-state politics and autocratic rule as driving forces of urban development processes