Photochromic molecular switches have the potential to act as colorimetric optical sensors for the real-time monitoring of toxic and poisonous heavy metal ions.

The performance of novel electrode materials and the influence of cell geometry or flow rate on capacitive water deionization (CDI) are usually described by global metrics from the analysis of the effluent electrolyte together with the electrochemical response of the system. However, these approaches cannot provide information on local variations of ion concentration and related local efficiency within an operating device. Here, a novel approach of position-resolved operando synchrotron-based X-ray transmission is introduced to determine local ion concentration changes along the flow channel from the inlet (feedwater) to the outlet (effluent water) of a working CDI cell. A specific cell design allows the independent quantification of concentration changes within the bulk electrolyte in the flow channel as well as the two oppositely charged nanoporous electrodes. Results from a 15 mM CsCl feed solution using three flow rates and two carbon materials with hierarchical porosity reveal a complex spatial-and temporal ion distribution in the system. A distinct dependence of local concentration on the flow rate is observed, with generally decreasing local desalination capacity towards the outlet of the cell, particularly for slow flow rates. It is also found that a significantly better overall performance for one of the two materials can be related to dominant counter-ion adsorption within ultramicropores, which ions cannot access in their hydrated state at no applied potential (ionophobicity). Overall, the results demonstrate the unique potential of position-resolved operando X-ray techniques to get mechanistic insight into local ion redistribution in CDI systems, allowing ultimately guiding performance optimization.

Background Solubility is a common feature of allergens. However, the causative relationship between this protein-intrinsic feature and sensitization capacity of allergens is not fully understood. This study aimed to proof the concept of solubility as a protein intrinsic feature of allergens. Methods The soluble birch pollen allergen Bet v 1 was covalently coupled to 1 μm silica particles. IgE-binding and -cross-linking capacity was assessed by inhibition ELISA and mediator release assay, respectively. Alterations in adjuvanticity by particle-loading were investigated by activation of dendritic cells, mast cells and the Toll-like receptor 4 pathway as well as by Th2 polarization in an IL-4 reporter mouse model. In BALB/c mice, particle-loaded and soluble Bet v 1 were compared in a model of allergic sensitization. Antigen uptake and presentation was analysed by restimulating human Bet v 1-specific T cell lines. Results Covalent coupling of Bet v 1 to silica particles resulted in an insoluble antigen with retained IgE-binding and -cross-linking capacity and no increase in adjuvanticity. In vivo, particle-loaded Bet v 1 induced significantly lower Bet v 1-specific (s)IgE, whereas sIgG1 and sIgG2a levels remained unaffected. The ratio of Th2 to Th1 cells was significantly lower in mice sensitized with particle-loaded Bet v 1. Particle-loading of Bet v 1 resulted in a 24-fold higher T cell activation capacity in Bet v 1-specific T cell lines, indicating more efficient uptake and presentation than of soluble Bet v 1. Conclusions Our results show that solubility is a decisive factor contributing to the sensitization capacity of allergens. The reduction in sensitization capacity of insoluble, particle-loaded antigens results from enhanced antigen uptake and presentation compared to soluble allergens.

The novel synthesis of carbon spherogels in organic solvents enables energy and solvent savings and omits supercritical drying. In addition, the resulting carbon spherogels feature excellent capacitance for energy storage in a supercapacitor setup.

Mesoporous titania thin films offer promising applications in sensors, batteries, and solar cells. The traditional soft templating methods rely on high-temperature calcination, which is energy-intensive, incompatible with thermosensitive flexible substrates, and destructive for titania structures. This work demonstrates UV irradiation as a versatile low-temperature and energy-saving alternative for mesoporous crystalline titania fabrication. Grazing incidence wide-angle X-ray scattering analysis reveals a three-stage crystallization process with increasing UV irradiation time supported by photoluminescence data. UV-irradiation-derived samples exhibit crystallinity and crystal size comparable to that of calcination. Integration with block copolymer templated sol-gel synthesis enables the creation of various morphologies, including cylindrical, ordered spherical, and hybrid structures. Characterizations via scanning electron microscopy and grazing incidence small-angle X-ray scattering confirm the homogeneity of morphology in the resulting films. The resulting films maintain similar optical properties despite morphological differences, as demonstrated by photoluminescence and UV-vis measurements. The versatility of UV irradiation extends to different titanium precursors, underscoring it as a flexible and efficient method for mesoporous titania thin film fabrication at low temperatures.

The spatial organization of metal oxide nanoparticles represents an important factor in the chemical utilization of resulting structures. For the production of networks that are composed of metal oxide nanoparticle chains, we dispersed vapor phase-grown TiO 2 and ZnO nanoparticles homogeneously in an aqueous polyvinyl alcohol solution. After electrospinning, we analyzed the sizes and diameters of the compositionally homogeneous electrospun fibers and discussed the size distribution and morphology of the nanoparticles inside. Calcination-induced polymer removal gives rise to self-supported nanoparticle-based nanofibers. Particle coarsening by a factor of ~ 2 for TiO 2 and ~ 3 for ZnO nanoparticles is observed. Graphical abstract

As a result of the global demand for sustainable products, a suitable alternative to the resorcinol-formaldehyde aerogels, which are frequently used as precursors for carbon aerogels, is searched for. In this study, the replacement of petroleum-derived formaldehyde with a natural, biobased crosslinker, namely 5-(hydroxymethyl)furfural (5-HMF) is shown, and the synthesis of renewable, monolithic tannin aerogels is demonstrated. Compared to well-known tannin-formaldehyde aerogels, this green alternative shows lower reactivity of the crosslinker associated with lower gelation times as well as lower specific surface areas at the organic stage. Nonetheless, the morphologies and synthesis-structure relationships follow similar trends for both tannin-based aerogels, e.g., the pore size is influenced by the initial pH in the same manner. The turnover to carbon aerogels by a carbothermal treatment results in enhanced high-specific surface areas of the tannin-5-HMF-based carbon aerogels, which are similar and even slightly outperform those obtained from tannin-formaldehyde aerogels. This suggests that they are a convenient alternative for carbon aerogel applications.

For electrospinning of MgO nanoparticle-based fiber architectures, we exploit the intermediate formation of layered Mg(OH)2 nanosheets that form inside polyvinylalcohol (PVA) based fibers during nanoparticle-polymer formulation. Upon calcination, Mg(OH)2 nanosheets undergo a topotactic dehydration reaction. In conjunction with polymer removal, these sheets generate staggered MgO nanoparticle ensembles that comprise flat ribbons. With methanol as a solvent and in polyvinylpyrrolidone (PVP) fibers, the MgO nanoparticles retain their crystallinity and structure inside the electrospun fibers. After calcination, they form nanoparticle threads with a cylindrical profile and particle size gradient.

The usage of a highly efficient, low-cost, and sustainable adsorbent material as an industrial wastewater treatment technique is required. Herein, the usage of the novel, fully sustainable tannin-5-(hydroxymethyl)furfural (TH) aerogels, generated via a water-based sol–gel process, as compatible biosorbent materials is presented. In particular, this study focusses on the surface modification of the tannin biosorbent with carboxyl or amino functional groups, which, hence, alters the accessible adsorption sites, resulting in increased adsorption capacity, as well as investigating the optimal pH conditions for the adsorption process. Precisely, highest adsorption capacities are acquired for the metal cations and cationic dye in an alkaline aqueous environment using a carboxyl-functionalized tannin biosorbent, whereas the anionic dye requires an acidic environment using an amino-functionalized tannin biosorbent. Under these determined optimal conditions, the maximum monolayer adsorption capacity of the tannin biosorbent ensues in the following order: Cu2+ > RB > Zn2+ > MO, with 500, 244, 192, 131 mg g−1, respectively, indicating comparable or even superior adsorption capacities compared to conventional activated carbons or silica adsorbents. Thus, these functionalized, fully sustainable, inexpensive tannin biosorbent materials, that feature high porosity and high specific surface areas, are ideal industrial candidates for the versatile adsorption process from contaminated (heavy) metal or dye solutions.

Recently, carbon spherogels have been introduced as a novel monolithic aerogel composed of hollow spheres. This material is conveniently obtained via polystyrene (PS) sphere templating. In the present study, we apply a water-soluble titania precursor (titanium(IV) bis(ammonium lactate) to the aqueous sol-gel synthesis based on resorcinol-formaldehyde (RF) to effectively encapsulate titania. In this way, a very high mass loading of up to 59 mass% of titania can be confined strictly to the inside of the hollow carbon spheres. In the final synthesis step, carbonization at 800 °C allows three simultaneous effects: Transformation of the RF coating on PS into microporous carbon, PS template removal by decomposition, and formation of titania due to precursor dissociation. A deliberate tuning of the microporous carbon shell, accessibility of the titania, titania amount, and titania’s polymorph is further demonstrated by thermal treatment. In contrast to non-tuned or TiC-containing carbon spherogels, CO2 activation of the composites results in a three orders of magnitude rise of their photocatalytic activity towards hydrogen evolution reaction, which we evaluate using flow and batch reactors. We further show that this effect is related to the partial etching of the carbonaceous shell, which renders TiO2 surface accessible to the reactants in the solution and allows for an efficient hole scavenging. Given the simplicity of the hybrid carbon spherogel (HCS) composite fabrication, the high degree of control of their morphological characteristics, and the striking effects of CO2 -activation on performance, we strongly believe that our results will interest a broad scientific community.

In situ small-angle X-ray scattering (SAXS) was employed to identify critical parameters during thermal treatment for template removal of an ordered mesoporous carbon precursor synthesized via a direct soft-templating route. The structural parameters obtained from the SAXS data as a function of time were the lattice parameter of the 2D hexagonal structure, the diameter of the cylindrical mesostructures and a power-law exponent characterizing the interface roughness. Moreover, detailed information on contrast changes and pore lattice order was obtained from analysis of the integrated SAXS intensity of the Bragg and diffuse scattering separately. Five characteristic regions during heat treatment were identified and discussed regarding the underlying dominant processes. The influence of temperature and O2/N2 ratio on the final structure was analyzed, and parameter ranges were identified for an optimized template removal without strongly affecting the matrix. The results indicate that the final structure and controllability of the process are optimum for temperatures between 260 and 300°C with a gas flow containing 2 mol% of O2.

In this study, we present a detailed comparison between a conventional supercritical drying process and an evaporative drying technique for hierarchically organized porous silica gel monoliths. These gels are based on a model system synthesized by the aqueous sol–gel processing of an ethylene-glycol-modified silane, resulting in a cellular, macroporous, strut-based network comprising anisotropic, periodically arranged mesopores formed by microporous amorphous silica. The effect of the two drying procedures on the pore properties (specific surface area, pore volume, and pore widths) and on the shrinkage of the monolith is evaluated through a comprehensive characterization by using nitrogen physisorption, electron microscopy, and small-angle X-ray scattering. It can clearly be demonstrated that for the hierarchically organized porous solids, the evaporative drying procedure can compete without the need for surface modification with the commonly applied supercritical drying in terms of the material and textural properties, such as specific surface area and pore volume. The thus obtained materials deliver a high specific surface area and exhibit overall comparable or even improved pore characteristics to monoliths prepared by supercritical drying. Additionally, the pore properties can be tailored to some extent by adjusting the drying conditions, such as temperature.

Tannin-furanic foams are a promising and biogenic alternative to oil-based porous materials. Their hydrophilic character, typically indicated by a contact angle to water of 70 & DEG;, limits some potential applications (for instance outdoor thermal insulation). To overcome this, a post-synthetic surface modification step with different fluorine-free organosilanes at 323 K was investigated with a focus on the final, hydrophobic performance. On the one side, methyltrimethoxysilane, and 3-(chloropropyl)trimethoxysi lane, which undergo self-condensation as well as bonding to the hydroxy groups of the tannin polymer, were applied. A modified surface structure and a 25 to 50 % weight increase, depending on the molecular weight of the silylation agent, were observed. Contrary, a mono-functional silane, precicely trimethylchlorosilane, shows only a slight increase in weight, yet also condenses onto the polymer surface without forming a protective surface coating layer. Contact angle measurements using water show an increase from 70 & DEG; (unmodified) up to 145 & DEG; for a silane-modified foam. Nuclear magnetic resonance and infrared spectroscopy show the formation of covalent bonds between the silane and the biogenic polymer matrix. The obtained material is less prone to absorb water from a humid atmosphere (reduction of 75 %) and is highly efficient for the removal of non-polar contaminants from water, featuring new pos-sible applications in humid surrounds.

In this work, polyvinylidene fluoride (PVDF) aerogels with a tailorable phase composition were prepared by following the crystallization-induced gelation principle. A series of PVDF wet gels (5 to 12 wt.%) were prepared from either PVDF–DMF solutions or a mixture of DMF and ethanol as non-solvent. The effects of the non-solvent concentration on the crystalline composition of the PVDF aerogels were thoroughly investigated. It was found that the nucleating role of ethanol can be adjusted to produce low-density PVDF aerogels, whereas the changes in composition by the addition of small amounts of water to the solution promote the stabilization of the valuable β and γ phases. These phases of the aerogels were monitored by FTIR and Raman spectroscopies. Furthermore, the crystallization process was followed by in-time and in situ ATR–FTIR spectroscopy. The obtained aerogels displayed specific surface areas > 150 m2 g−1, with variable particle morphologies that are dependent on the non-solvent composition, as observed by using SEM and Synchrotron Radiation Computed micro-Tomography (SR-μCT).

Sol-gel processing combined with soft templating and gelation-induced phase separation is very sensitive to the precursor sol composition. In this work we present a straightforward synthesis towards hierarchically structured, macroporous carbon/titania monoliths with ordered mesopores derived from resorcinol/formaldehyde monoliths and a glycolated titanium precursor. We demonstrate the influence of various reaction solvents, where diol-based media and the proportion of the catalyst seem to be essential in controlling spinodal decomposition, obtaining similar monolithic structures under different synthesis conditions. Based on these observations, we further homogeneously incorporated TiO2 into the carbon structure by an in situ synthesis approach, obtaining structural features similar to pure carbon materials with surface areas of about 400 m2  g-1 , periodically arranged mesopores with a mean distance of 10-11 nm and cellular macroporosity.

Tannin-silica hybrid materials are expected to feature excellent mechanic-chemical stability, large surface areas, high porosity and possess, after carbothermal reduction, high thermal stability as well as high thermal conductivity. Typically, a commercially available tetraethoxysilane is used, but in this study, a more sustainable route was developed by using a glycol-based silica precursor, tetrakis(2-hydroxyethyl)orthosilicate (EGMS), which is highly water-soluble. In order to produce highly porous, homogeneous hybrid tannin-silica aerogels in a one-pot approach, a suitable crosslinker has to be used. It was found that an aldehyde-functionalized silane (triethoxysilylbutyraldehyde) enables the covalent bonding of tannin and silica. Solely by altering the processing parameters, distinctly different tannin-silica hybrid material properties could be achieved. In particular, the amount of crosslinker is a significant factor with respect to altering the materials’ properties, e.g., the specific surface area. Notably, 5 wt% of crosslinker presents an optimal percentage to obtain a sustainable tannin-silica hybrid system with high specific surface areas of roughly 800–900 m2 g−1 as well as a high mesopore volume. The synthesized tannin-silica hybrid aerogels permit the usage as green precursor for silicon carbide materials.

Extraordinarily homogeneous, freestanding titania-loaded carbon spherogels can be obtained using Ti(acac)(2)(OiPr)(2) in the polystyrene sphere templated resorcinol-formaldehyde gelation. Thereby, a distinct, crystalline titania layer is achieved inside every hollow sphere building unit. These hybrid carbon spherogels allow capitalizing on carbon's electrical conductivity and the lithium-ion intercalation capacity of titania.

Highly porous inorganic-organic hybrid monoliths with mesopores in a macroporous network have been prepared from methyltris(2-hydroxyethoxy)silane (MeGMS) and tetrakis(2-hydroxyethoxy)silane (EGMS) in the presence of an amphiphilic block copolymer. The amount of methyltris(2-hydroxyethoxy)silane (MeGMS) in the gel has been varied from 0 to 100 %. These glycol-modified silanes have the advantage of being water-soluble and thus allowing for a direct templating of liquid-crystalline surfactant mesophases without the presence of a homogenizing organic solvent such as ethanol. The wet gels have been dried by supercritical extraction with carbon dioxide. In the present work, the sol-gel behaviour of these glycol-modified silanes is discussed especially with a focus on the formation of the meso- and macrostructure. In addition, the influences of the varying ratios of methyltris(2-hydroxyethoxy)silane on the structural features of the gels are investigated by various analytical techniques such as small angle X-ray scattering, nitrogen sorption, and scanning electron microscopy.

With increasing demand of alternatives to oil-based lightweight materials, the development of tannin-based foams is getting more and more attention. In this paper, an alternative to traditionally used solvent-evaporation in the production of tannin-foams is presented. Mixing the tannin-furanic resin with different amounts of ionic and non-ionic surfactants at high agitational speed allows for the formation of highly porous, mechanically stable tannin-foams. Investigations on the influence of surfactant type and ingredient ratios on the foaming behavior and properties of the final foams were conducted. Materials obtained via this route do present extraordinary compression resistance (about 0.8 MPa), good thermal insulation (40 mW/m·K) and are suitable as a wastewater treatment agent at the end-of-life. It was shown that during mechanical blowing, homogeneous cross-sections and almost perfectly round pores form, leading to the high compression resistance. Investigations by means of Fourier transform infrared and 13C nuclear magnetic resonance spectroscopy show that the milder reaction environment leads to more linear poly(furfuryl alcohol)-tannin chains. This new type of tannin foam allows for use in various different fields of application ranging from durable building insulation to wastewater treatment.

Organofunctional porous methyltrimethoxysilane (MTMS)-based aerogels are attractive for various adsorption purposes due to the combination of their unique properties such as low densities and high specific surface areas with tunable and accessible functional groups that can coordinate to, e.g., heavy metals and/or organic dye molecules in polar and non-polar solutions. Furthermore, the MTMS backbone gives these aerogels mechanical strength, the ability to be dried under ambient conditions and ensures their non-degradability in aqueous media and recyclability. Herein, we report the preparation of carboxylic acid-modified polysilsesquioxane aerogels via a simple and straightforward acid-base catalyzed sol-gel approach by using MTMS and the novel and stable 5-(trimethoxysilyl)pentanoic acid. In this surfactant assisted co-condensation approach, all parameters (concentration, pH, and temperature) have been carefully designed to yield porous (porosities between 82% and 53% and specific surface areas between 345 m(2).g (1) and 36 m(2).g(-1)), light (bulk densities between 1.38 g.cm(-3) and 1.16 g.cm(-3)), and hydrophobic aerogels with accessible and reactive functional carboxylic acid groups (-COOH) (accessible surface loading up to 0.19 mmol.g(-1)) for the adsorption of heavy metals ions (Zn2+ and Cu2+) and cationic dyes (methylene blue and rhodamine B). The maximum adsorption capacities obtained from Langmuir isotherms were 154 mg.g(-1), 106 mg.g(-1), 111 mg.g(-1), and 78 mg.g(-1) for RhB, MB, Zn2+, and Cu2+, respectively. An increasing content of carboxylic acid groups influences the morphology, specific surface area and adsorption behavior of the synthesized aerogels. Optimized functionalized aerogels can be dried ambiently and show high and reversible adsorption abilities of 87% over several cycles towards cationic dyes in aqueous media. Moreover, these carboxylic acid-modified aerogels demonstrate excellent adsorption selectivity by adsorbing only positively charged molecules from mixed dye solutions, making them ideal candidates for diverse adsorption processes in polar and non-polar solutions.