Transparent Sol-Gel-Based Coatings Reflecting Heat Radiation in the Near Infrared.

Thin, flat textile roofing offers negligible heat insulation. In warm areas, such roofing membranes are therefore equipped with metallized surfaces to reflect solar heat radiation, thus reducing the warming inside a textile building. Heat reflection effects achieved by metallic coatings are always accompanied by shading effects as the metals are non-transparent for visible light (VIS). Transparent conductive oxides (TCOs) are transparent for VIS and are able to reflect heat radiation in the infrared. TCOs are, e.g., widely used in the display industry. To achieve the perfect coatings needed for electronic devices, these are commonly applied using costly vacuum processes at high temperatures. Vacuum processes, on account of the high costs involved and high processing temperatures, are obstructive for an application involving textiles. Accepting that heat-reflecting textile membranes demand less perfect coatings, a wet chemical approach has been followed here when producing transparent heat-reflecting coatings. Commercially available TCOs were employed as colloidal dispersions or nanopowders to prepare sol-gel-based coating systems. Such coatings were applied to textile membranes as used for architectural textiles using simple coating techniques and at moderate curing temperatures not exceeding 130 °C. The coatings achieved about 90% transmission in the VIS spectrum and reduced near-infrared transmission (at about 2.5 µm) to nearly zero while reflecting up to 25% of that radiation. Up to 35% reflection has been realized in the far infrared, and emissivity values down to ε = 0.5777 have been measured.

Moving adsorption belt system for continuous bioproduct recovery utilizing composite fibrous adsorbents.

A continuous protein recovery and purification system based on the true moving bed concept is presented. A novel adsorbent material, in the form of an elastic and robust woven fabric, served as a moving belt following the general designs observed in known belt conveyors. The composite fibrous material that forms the said woven fabric showed high protein binding capacity, reaching a static binding capacity equal to 107.3 mg/g, as determined via isotherm experiments. Moreover, testing the same cation exchange fibrous material in a packed bed format resulted in excellent dynamic binding capacity values (54.5 mg/g) even when operating at high flow rates (480 cm/h). In a subsequent step, a benchtop prototype was designed, constructed, and tested. Results indicated that the moving belt system could recover a model protein (hen egg white lysozyme) with a productivity up to 0.5 mg/cm2/h. Likewise, a monoclonal antibody was directly recovered from unclarified CHO_K1 cell line culture with high purity, as judged by SDS-PAGE, high purification factor (5.8), and in a single step, confirming the suitability and selectivity of the purification procedure.

Development of Carbon-Nanodot-Loaded PLA Nanofibers and Study of Their Barrier Performance for Medical Applications.

The COVID-19 pandemic has increased the usage of personal protective equipment (PPE) all round the world and, in turn, it has also increased the waste caused by disposable PPE. This has exerted a severe environmental impact, so in our work, we propose the utilization of a sustainable electrospun nanofiber based on poly lactic acid (PLA), as it is biobased and conditionally degradable. We optimized the weight percentage of the PLA-precursor solution and found that 19% PLA produces fine nanofibers with good morphology. We also introduced carbon nanodots (CNDs) in the nanofibers and evaluated their antibacterial efficiency. We used 1, 2, 3, and 4% CNDs with 19% PLA and found increased antibacterial activity with increased concentrations of CNDs. Additionally, we also applied a spunbond-nanofiber layered assembly for the medical face masks and found that with the addition of only 0.45 mg/cm2 on the nonwoven sheet, excellent particle filtration efficiency of 96.5% and a differential pressure of 39 Pa/cm2 were achieved, meeting the basic requirements for Type I medical face masks (ASTM-F2100).

Megaporous monolithic adsorbents for bioproduct recovery as prepared on the basis of nonwoven fabrics.

Megaporous adsorbents were prepared based on nonwoven polyethylene terephthalate (PET) fabrics and functionalized by covalent modification with polyvinylamine (PVAm) or monotriazinyl-ß-cyclodextrin-substituted polyvinylamine (PVAm-MCT-ß-CD). Mechanical properties of the resulting fabrics were maintained, as judged by tensile strength tests and scanning electron microscopy. Exceptional porosity (≥82%) and preserved hydrodynamic characteristics (Pe ≥ 63) indicated excellent structural stability when packed. The performance of the constructed adsorbents was evaluated with high molecular weight (proteins) and low molecular weight (dyes) model compounds. The static binding capacity (SBC) for bovine serum albumin (BSA) was 79.7 ± 1.3 and 92.9 ± 8.2 mg/g for PVAm-modified and PVAm-MCT-ß-CD-modified fabrics, respectively. The mentioned materials also adsorbed Orange II, an acidic dye (92.4 ± 2.6 and 101.9 ± 2.6 mg/g, respectively), indicating that the hydrophobicity was a prevailing binding mechanism operating at a pH close to isoelectric point. SBC for lysozyme and toluidine blue O (TBO, a basic dye) onto PVAm-MCT-ß-CD functionalized PET was 52.7 ± 5.1 and 73.3 ± 0.6 mg/g, respectively. TBOs have also shown some affinity for PVAm functionalized PET, but this was most likely to be mediated by hydrophobicity. On the other hand, operating at a superficial velocity of 90 cm/h, dynamic binding capacity for BSA was 11.4 ± 3.5 and 2.5 ± 0.6 mg/g indicating the importance of possible aggregation mechanisms during protein binding at equilibrium. Thus, PET-based adsorbents require further functional improvement for chromatography applications. However, the easy-to-construct, scalable nonwoven adsorbents deserve further attention as a potential alternative to packed-bed-chromatography adsorbents.

Characterization and Optimization of AZO Nanoparticles as Coatings for Flexible Substrates toward High IR Reflectivity.

Energy consumption by air-conditioning is expansive and leads to the emission of millions of tons of CO2 every year. A promising approach to circumvent this problem is the reflection of solar radiation: Rooms that would not heat up by irradiation will not need to be cooled down. Especially, transparent conductive metal oxides exhibit high infrared (IR) reflectivity and are commonly applied as low-emissivity coatings (low-e coatings). Indium tin oxide (ITO) coatings are the state-of-the-art application, though indium is a rare and expensive resource. This work demonstrates that aluminum-doped zinc oxide (AZO) can be a suitable alternative to ITO for IR-reflection applications. AZO synthesized here exhibits better emissivity to be used as roofing membrane coatings for buildings in comparison to commercially available ITO coatings. AZO particles forming the reflective coating are generated via solvothermal synthesis routes and obtain high conductivity and IR reflectivity without the need of any further post-thermal treatment. Different synthesis parameters were studied, and their effects on both conductive and optical properties of the AZO nanoparticles were evaluated. To this end, a series of characterization methods, especially 27Al-nuclear magnetic resonance spectroscopy (27Al-NMR) analysis, have been conducted for a deeper insight into the particles' structure to understand the differences in conductivity and optical properties. The optimized AZO nanoparticles were coated on flexible transparent textile-based roofing membranes and tested as low-e coatings. The membranes demonstrated higher thermal reflectance compared with commercial ITO materials with an emissivity value lowered by 16%.

A recent overview on the synthesis of 1,4,5-trisubstituted 1,2,3-triazoles.

Diverse strategies for the efficient and attractive synthesis of a wide variety of relevant 1,4,5-trisubstituted 1,2,3-triazole molecules are reported. The synthesis of this category of diverse fully functionalized 1,2,3-triazoles has become a necessary and unique research subject in modern synthetic organic key transformations in academia, pharmacy, and industry. The current review aims to cover a wide literature survey of numerous synthetic strategies. Recent reports (2017-2021) in the field of 1,4,5-trisubstituted 1,2,3-triazoles are emphasized in this current review.

A Flame-Retardant Phytic-Acid-Based LbL-Coating for Cotton Using Polyvinylamine.

Phytic acid (PA), as a natural source of phosphorus, was immobilized on cotton (CO) in a layer-by-layer (LbL) approach with polyvinylamine (PVAm) as the oppositely charged electrolyte to create a partly bio-based flame-retardant finish. PVAm was employed as a synthetic nitrogen source with the highest density of amine groups of all polymers. Vertical flame tests revealed a flame-retardant behavior with no afterflame and afterglow time for a coating of 15 bilayers (BL) containing 2% phosphorus and 1.4% nitrogen. The coating achieved a molar P:N ratio of 3:5. Microscale combustion calorimetry (MCC) analyses affirmed the flame test findings by a decrease in peak heat release rate (pkHRR) by more than 60% relative to unfinished CO. Thermogravimetric analyses (TGA) and MCC measurements exhibited a shifted CO peak to lower temperatures indicating proceeding reactions to form an isolating char on the surface. Fourier transform infrared spectroscopy (FTIR) coupled online with a TGA system, allowed the identification of a decreased amount of acrolein, methanol, carbon monoxide and formaldehyde during sample pyrolysis and a higher amount of released water. Thereby the toxicity of released volatiles was reduced. Our results prove that PA enables a different reaction by catalyzing cellulosic dehydration, which results in the formation of a protective char on the surface of the burned fabric.

Hydrogel Functionalized Polyester Fabrics by UV-Induced Photopolymerization.

We address a strategy to graft hydrogels onto polyethylene terephthalate (PET) fabrics using different acrylate-based monomers. The hydrogel-modified fabrics were prepared by a two-step modification. To this end, double functional groups were firstly introduced onto the PET surface via an aminolysis reaction involving allylamine. The final grafted polymer networks were then obtained after UV-induced radical photopolymerization by varying acrylate monomer types in the presence of a cross-linker. After characterization, the resulting hydrogels showed different morphologies and abrasion resistance performances depending on their chemical nature. UV-photopolymerization is a fast and low-cost method to achieve technical fabrics with specific desired properties.

A Green Water-Soluble Cyclophosphazene as a Flame Retardant Finish for Textiles.

Poly- and cyclophosphazenes are excellent flame retardants but currently, are not used as textile finishing agents because water-soluble and permanent washing systems are missing. Here, we demonstrate for the first time, the successful usage of a water-soluble cyclotriphosphazene derivative for textile finishing for cotton, different cotton/polyester, and cotton/polyamide blend fabrics. A durable finish was achieved using a photoinduced grafting reaction. The flame retardant properties of the various fabrics were improved with a higher limiting oxygen index, a reduced heat release rate, and an exhibition of intumescent. Furthermore, the finished textiles passed several standardized flammability tests.

Electrical conductivity of silver nanoparticle doped carbon nanofibres measured by CS-AFM.

In this work, a pioneering study on the electrical properties of composite carbon nanofibres (CNFs) using current-sensitive atomic force microscopy (CS-AFM) has been demonstrated. CNFs are highly interesting materials which are usable in a wide array of applications e.g. electrode materials for biosensors, lithium ion batteries, fuel cells and supercapacitors. CNFs offer a high specific surface area and thus have a high contact area for charge transfer. CNFs can be produced using spinnable polyacrylonitrile (PAN) as a precursor for carbonisation. For the purpose of developing efficient CNFs with high conductivity and power density, silver nanoparticle (AgNPs)-containing PAN solutions were electrospun to form composite nanofibres which was followed by heat treatment. The applied voltage of the spinning setup and the content of both PAN and the silver nanoparticles in the spinning solution were varied in order to study their influence on the morphology and the electrical properties of the nanofibres. The resultant morphologies and fibre diameters were determined by scanning electron microscopy (SEM). The formation of silver nanoparticles was characterised in solution by UV-visible absorption spectroscopy and dynamic light scattering (DLS), while energy-dispersive X-ray spectroscopy (EDX) and transmission electron microscopy (TEM) were carried out to investigate the presence as well as the average diameter of the AgNPs. The electrical properties of the CNFs were investigated using CS-AFM. This technique gives us the possibility to explore the electrical properties of single fibers and hence derive relationships between the structural features and the electrical properties. Our results show that the composite CNFs have a higher electrical conductivity than the neat CNFs and both the average diameter of the fibers and the electrical conductivity increase with an increasing AgNP content.

On the Potential of Using Dual-Function Hydrogels for Brackish Water Desalination.

Although current desalination technologies are mature enough and advanced, the shortage of freshwater is still considered as one of the most pressing global issues. Therefore, there is a strong incentive to explore and investigate new potential methods with low energy consumption. We have previously reported that reversible thermally induced sorption/desorption process using polymeric hydrogels hold promise for water desalination with further development. In order to develop a more effective hydrogels architecture, polyelectrolyte moieties were introduced in this work as pendent chains and a thermally responsive polymer as network backbone using reversible addition-fragmentation chain transfer (RAFT) polymerisation. The ability of the comb-type polymeric hydrogels to desalinate water was evaluated. These hydrogels were proved to absorb water with low salinity from brine solution of 2 g L - 1 NaCl and release the absorbed water at relatively low temperature conditions of 50 ∘ C. The fraction of the grafted polyacrylic acid and the comb-chain length were varied to understand their influence on the swelling/deswelling behaviour for these hydrogels. The ionic fraction in the hydrogels and the resulting hydrophilic/hydrophobic balance are crucial for the proposed desalination process. In contrast, the comb-chain length impacted the swelling behaviour of hydrogels but showed relatively little influence on the dewatering process.

A synchrotron study of [5,10,15,20-tetrakis(3-cyanophenyl)porphyrinato-κ4N5,N10,N15,N20]copper(II) nitrobenzene trisolvate at 80†K.

Porphyrin assemblies display interesting photophysical properties and a relatively high thermal stability. Moreover, meso-functionalized porphyrins with virtually fourfold symmetry can be relatively readily synthesized from pyrrole and the appropriate aldehyde. A number of metallo derivatives of 5,10,15,20-tetrakis(4-cyanophenyl)porphyrin, where the N atom of the linear cyano group can act both as a donor for coordination bonds or as an acceptor for hydrogen bonds, have been structurally characterized by single-crystal X-ray analysis. The supramolecular and structural chemistry of the corresponding 2- and 3-cyanophenyl isomers of the parent porphyrin, however, has remained largely unexplored. The crystal structure of [5,10,15,20-tetrakis(3-cyanophenyl)porphyrinato]copper(II) (CuTCNPP) nitrobenzene trisolvate, [Cu(C48H24N8)]·3C6H5NO2, has been determined at 80 K by synchrotron single-crystal X-ray diffraction. CuTCNPP exhibits a C2h-symmetric ααßß conformation, despite an unsymmetrical crystal environment, and is situated on a crystallographic centre of symmetry. The CuII ion adopts a genuine square-planar coordination by the four pyrrole N atoms. The 24-membered porphyrin ring system shows no marked deviation from planarity. In the crystal, the CuTCNPP molecules and two nitrobenzene molecules are face-to-face stacked in an alternating fashion, resulting in corrugated layers. The remaining nitrobenzene guest molecule per CuTCNPP resides in the region between four neighbouring columnar stacks of CuTCNPP and sandwiched nitrobenzene molecules, and is disordered over four positions about a centre of symmetry.

Permanent flame retardant finishing of textiles by allyl-functionalized polyphosphazenes.

Despite their excellent flame retardant properties, polyphosphazenes are currently not used as flame retardant agents for textile finishing, because a permanent fixation on the substrate surface has failed so far. Here, we present the successful synthesis and characterization of a noncombustible and foam-forming polyphosphazene derivative, that can be immobilized durably on cotton and different cotton/polyester blended fabrics using photoinduced grafting reactions. The flame retardant properties are improved, a higher limiting oxygen index is found, and the modified textiles pass several standardized flammability tests. As flame retardant mechanism a synergistic effect between the immobilized polyphosphazene and the textile substrate was observed. The polyphosphazene finishing induces an earlier decomposition of the material with a reduced mass loss in thermogravimetric analysis. The decomposition of cotton and polyester leads to the formation of phosphorus oxynitride, which forms a protecting barrier layer on the fiber surface. In addition, the permanence of the flame retardant finishing was proven by laundry and abrasion tests.

Organotextile catalysis.

Throughout human history, textiles have been integral to daily life, but their exploration in catalysis has been rare. Herein, we show a facile and permanent immobilization of organocatalysts on the textile nylon using ultraviolet light. The catalyst and the textile material require no chemical modification for the immobilization. All of the prepared textile-immobilized organocatalysts (a Lewis basic, a Brønsted acidic, and a chiral organocatalyst) display excellent stability, activity, and recyclability for various organic transformations. Very good enantioselectivity (>95:5 enantiomeric ratio) can be maintained for more than 250 cycles of asymmetric catalysis. Practical and straightforward applications of textile organocatalysis may be beneficial for various fields by offering inexpensive and accessible functionalized catalytic materials.