Erik Sebastian Schneider

Polyacrylonitrile (PAN) membranes are widely used for water purification, but their susceptibility to fouling limits efficiency and lifespan. In this study, a sustainable and efficient UV-grafting process was employed to modify PAN membranes. Cationic and zwitterionic vinylbenzene- and methacrylate-based monomers, including ammonium, ammonium alcohol, N-oxide, carboxybetaine, sulfobetaine, and phosphobetaine groups, were used to graft polymers from the membrane surface using photoinitiators such as phenylbis(2,4,6-trimethylbenzoyl)phosphine oxide (BAPO) and lithium phenyl-2,4,6-trimethylbenzoylphosphinate (LAP). The modified membranes were characterized using FTIR, SEM-EDX, AFM, ζ potential analysis, permeability testing, molecular weight cutoff measurements, dye adsorption assays, porosity, and pore size analysis. Microbiological evaluation following a modified ASTM E2149-20 protocol revealed antibacterial properties for some of the grafted polymers. These findings demonstrate the potential of postfunctionalized PAN membranes for the adsorption of dyes and to mitigate fouling, both are important factors for water treatment.

Dendritic Fibrous Nanosilica (DFNS) holds great promise for applications in various biomedical fields, CO₂ capture and conversion, catalysis, environmental remediation (or water treatment), and sensor development. While the impact of primary (linear) alcohols as co-surfactants in their synthesis has been investigated, the role of other alcohols beyond linear remains unexplored to date. In this study, we investigated the impact of different alcohols as co-surfactants on the morphology, structure, and physical properties of DFNS. We employed various primary, secondary, and tertiary alcohols, as well as diols with differing chain lengths and isomers. Significant variations in the specific surface area (S_BET) and total pore volume (V_p) were revealed across the samples, accompanied by notable morphological differences observed by scanning and transmission electron microscopy and small angle X-ray scattering. The highest S_BET and V_p values were found in samples synthesized with primary or linear alcohols, while much lower values were observed for samples synthesized with branched alcohols and diols. These findings emphasize the role of alcohols in governing the final morphology and structure of DFNS.

Thin-film composite (TFC) membranes containing a metal–polyphenol network (MPN)-based selective layer were fabricated on a porous polyacrylonitrile support. The MPN layer was formed through coordination-based self-assembly between plant-based tannic acid (TA) and an Fe³⁺ ion. For the first time, we demonstrate that TFC membranes containing TA-Fe³⁺ selective layers can separate small organic solutes in aqueous media from equimolar mixtures of solutes. The effect of the assembly time on the characteristics and performance of the fabricated selective layer was investigated. An increase in the assembly time led to the formation of selective layers with smaller effective pore sizes. The tannic acid–Fe³⁺ selective layer exhibited a low rejection towards neutral solutes riboflavin and poly(ethylene glycol) while high rejections were observed for anionic dyes of orange II and naphthol green B. Permeation selectivities in the range of 2–27 were achieved between neutral and charged dyes in both single- and mixed-solute experiments, indicating the significant role of Donnan exclusion and the charge-selective nature of the membranes. The rejection efficiency improved with an increasing assembly time. Overall, this study demonstrates that the assembly time is a vital casting parameter for controlling the permeance, rejection and selectivity of thin-film composite membranes with a tannic acid–Fe³⁺ selective layer.

Ion adsorbing ultrafiltration membranes provide an interesting possibility to remove toxic ions from water. Furthermore, it is also possible to recover valuable elements. In this work, we demonstrate two easy strategies to modify polyacrylonitrile membranes with anion and cation adsorbing groups. The membranes were modified to have positively charged amine groups or negatively charged carboxyl groups. The success of the reactions was confirmed using IR spectroscopy and zeta-potential measurements. The membranes carrying negatively charged groups provided a negative zeta-potential and had an isoelectric point at pH 3.6, while the membranes carrying positively charged groups had a positive zeta-potential in the analyzed pH range. Since only the surface of the polymer was modified, the pore size and permeance of the membranes were not drastically affected. The membranes prepared by both modification strategies had a pure water permeance higher than 1000 L/(m² h bar) and a water contact angle of 44.3 and 57.2°, respectively. Therefore, the membranes can be operated at low pressures with reasonable flux. Additionally, SEM images showed that the membranes were still open-pored. Adsorption tests using a positively and a negatively charged dye as well as a toxic cation and an anion were performed to analyze the adsorption behavior. Both membranes were able to adsorb the oppositely charged dyes as well as the copper and chromate ions. Therefore, these membranes are good candidates to purify water streams containing hazardous ions.

Accomplishing on‐demand molecular separation with a high selectivity and good permeability is very desirable for pollutant removal and chemical and pharmaceutical processing. The major challenge for sub‐10 nm filtration of particles and molecules is the fabrication of high‐performance membranes with tunable pore size and designed functionality. Here, a versatile top‐down approach is demonstrated to produce such a membrane using isoporous block copolymer membranes with well‐defined pore sizes combined with growth of metal oxide using sequential infiltration synthesis and atomic layer deposition (SIS and ALD). The pore size of the membranes is tuned by controlled metal oxide growth within and onto the polymer channels, enabling up to twofold pore diameter reduction. Following the growth, the distinct functionalities are readily incorporated along the membrane nanochannels with either hydrophobic, cationic, or anionic groups via straightforward and scalable gas/liquid–solid interface reactions. The hydrophilicity/hydrophobicity of the membrane nanochannel is significantly changed by the introduction of hydrophilic metal oxide and hydrophobic fluorinated groups. The functionalized membranes exhibit a superior selectivity and permeability in separating 1–2 nm organic molecules and fractionating similar‐sized proteins based on size, charge, and hydrophobicity. This demonstrates the great potential of organic–inorganic–organic isoporous membranes for high‐performance molecular separation in numerous applications.

The receiver sensory system plays a crucial role in the evolution of new communication signals in insects. Among acoustic communicating crickets, the tribe Lebinthini (Eneopterinae) has evolved a unique communication system in that males produce exceptionally high-frequency calls and females respond with vibratory signals to guide males towards them. In this study, we describe nine species of Eneopterinae in which the sound receiving structures have undergone considerable morphological changes. We revealed that the anterior tympanal membrane (ATM) of the ear was extremely thin, as little as 0.35 µm thick, and to the best of our knowledge, this is the thinnest tympanal membrane found in crickets thus far. Measurements of tympanum vibrations obtained fromLebinthus bitaeniatusdemonstrated a strong sensitivity towards higher frequencies. The finding also coincides with the neuronal tuning of ascending neurons and the behavioural response of the Lebinthini. The morphologically specialized ATM and its mechanical sensitivity for high frequencies, therefore, may have driven the sensory exploitation of an anti-predator behaviour that led to the evolution of a new communication system known for this group of crickets. The hypothetical phylogenetic origin of the investigated tympanal ears is discussed.