Gel Chemistry Research Articles

Cellulose nanocrystals built multiscale hydrogel electrolyte for highly reversible all-flexible zinc ion batteries

Hydrogel electrolytes are promising for flexible and stable zinc ion batteries (ZIBs), but they lack fatigue resistance and still face challenges in terms of mechanical stability and durability. Herein, inspired by the hierarchical structure of biological networks, multiscale anti-fatigue hydrogel electrolytes with high toughness, high strength, and rapid recovery are constructed by introducing nanoscale cellulose nanocrystals (CNCs) as building blocks into dual-network cross-linking hydroxypropyl chitosan (HPCS) modified polyacrylamide (PAM) hydrogel (denoted as PHC-gel). As a result, the PHC-gel achieves a high fatigue threshold up to 356 J m−2 and with a superior strength and stretchability up to 180 kPa and 3178 %, respectively. In addition, the assembled Zn//Zn cell exhibits long-term cycling stability of 1800 h at 1 mA cm−2/1 mAh cm−2 with a high Coulombic efficiency of 99.4 %. More importantly, the Zn//PHC-gel//MnO2 flexible cell shows remarkable flexibility and capacity retention under different stretching and deformation conditions. This work demonstrates a promising gel chemistry that improves anti-fatigue properties and controls zinc behavior, offering great potential for high-performance flexible and wearable ZIBs and beyond.

Bicontinuous silica-epoxy nanocomposites by aerogel infusion

Interpenetrated, bicontinuous nanocomposites are formed by fully infusing monolithic mesoporous silica (silica aerogel) with epoxy resin. The long-range connectivity of the silica network facilitates direct load transfer and enforces sample homogeneity. The silica networks are prepared using sol–gel chemistry, informed by new phase diagrams, adapted to maximise reinforcement content in the subsequent bicontinuous composite. The infusibility of the aerogels is correlated to pore characteristics determined by gas sorption, as a function of silica aerogel density. Silica reinforcement loadings of up to 22silica vol.% are fully consolidated, with only a modest reduction in glass transition temperature and no change in cure conditions. The reinforcement improves both hardness (+23 %) and reduced modulus (+17 %) of the baseline resin. These properties increase with aerogel content viaa power law relationship which demonstrates the direct role of the connected silica phase as a reinforcing network and motivates future studies to extend the applicable range.

Unraveling optical and electrical dynamics in synthesized TiO2 nanopowder through sol–gel chemistry

Unraveling optical and electrical dynamics in synthesized TiO2 nanopowder through sol–gel chemistry

Toward Simultaneous Dense Zinc Deposition and Broken Side-Reaction Loops in the Zn//V2 O5 System.

The Zn//V2 O5 system not only faces the incontrollable growth of zinc (Zn) dendrites, but also withstands the cross-talk effect of by-products produced from the cathode side to the Zn anode, inducing interelectrode talk and aggravating battery failure. To tackle these issues, we construct a rapid Zn2+ -conducting hydrogel electrolyte (R-ZSO) to achieve Zn deposition modulation and side reaction inhibition in Zn//V2 O5 full cells. The polymer matrix and BN exhibit a robust anchoring effect on SO4 2- , accelerating Zn2+ migration and enabling dense Zn deposition behavior. Therefore, the Zn//Zn symmetric cells based on the R-ZSO electrolyte can operate stably for more than 1500 h, which is six times higher than that of cells employing the blank electrolyte. More importantly, the R-ZSO hydrogel electrolyte effectively decouples the cross-talk effects, thus breaking the infinite loop of side reactions. As a result, the Zn//V2 O5 cells using this modified hydrogel electrolyte demonstrate stable operation over 1,000 cycles, with a capacity loss rate of only 0.028 % per cycle. Our study provides a promising gel chemistry, which offers a valuable guide for the construction of high-performance and multifunctional aqueous Zn-ion batteries.

Toward Simultaneous Dense Zinc Deposition and Broken Side‐Reaction Loops in the Zn//V2O5 System

AbstractThe Zn//V2O5 system not only faces the incontrollable growth of zinc (Zn) dendrites, but also withstands the cross‐talk effect of by‐products produced from the cathode side to the Zn anode, inducing interelectrode talk and aggravating battery failure. To tackle these issues, we construct a rapid Zn2+‐conducting hydrogel electrolyte (R‐ZSO) to achieve Zn deposition modulation and side reaction inhibition in Zn//V2O5 full cells. The polymer matrix and BN exhibit a robust anchoring effect on SO42−, accelerating Zn2+ migration and enabling dense Zn deposition behavior. Therefore, the Zn//Zn symmetric cells based on the R‐ZSO electrolyte can operate stably for more than 1500 h, which is six times higher than that of cells employing the blank electrolyte. More importantly, the R‐ZSO hydrogel electrolyte effectively decouples the cross‐talk effects, thus breaking the infinite loop of side reactions. As a result, the Zn//V2O5 cells using this modified hydrogel electrolyte demonstrate stable operation over 1,000 cycles, with a capacity loss rate of only 0.028 % per cycle. Our study provides a promising gel chemistry, which offers a valuable guide for the construction of high‐performance and multifunctional aqueous Zn‐ion batteries.

Thioxanthone-Based Siloxane Photosensitizer for Cationic/Radical Photopolymerization and Photoinduced Sol-Gel Reactions.

In this investigation, a multifunctional visible-light TX-based photosensitizer containing a siloxane moiety (TXS) was designed with a good overall yield of 54%. The addition of a siloxane moiety enabled the incorporation of a TX photosensitizer into a siloxane network by photoinduced sol-gel chemistry, thus avoiding its release. Both liquid 1H and solid-state 29Si NMR measurements undeniably confirmed the formation of photoacids resulting from the photolysis of the TXS/electron acceptor molecule (Iodonium salt), which promoted the photoinduced hydrolysis/condensation of the trimethoxysilane groups of TXS, with a high degree of condensation of its inorganic network. Notably, the laser flash photolysis, fluorescence, and electron paramagnetic resonance spin-trapping (EPR ST) experiments demonstrated that TXS could react with Iod through an electron transfer reaction through its excited states, leading to the formation of radical initiating species. Interestingly, the TXS/Iod was demonstrated to be an efficient photoinitiating system for free-radical (FRP) and cationic (CP) polymerization under LEDs@385, 405, and 455 nm. In particular, whatever the epoxy monomer mixtures used, remarkable final epoxy conversions were achieved up to 100% under air. In this latter case, we demonstrated that both the photoinduced sol-gel process (hydrolysis of trimethoxysilane groups) and the cationic photopolymerization occurred simultaneously.

High surface area of carbonaceous Cr2GaC composite microspheres synthesized by sol–gel chemistry

Carbonaceous Cr2GaC microspheres are synthesized by means of sol–gel chemistry and exhibit high BET surface area after pyrolysis.

A route toward fabrication of 3D printed bone scaffolds based on poly(vinyl alcohol)–chitosan/bioactive glass by sol–gel chemistry

Among different methods for the fabrication of bone scaffolds, 3D printing has created great advances in tissue engineering and regenerative medicine owing to its ability to make objects mimicking native tissues. Thanks to its abundant availability, structural features, and favorable biological properties, chitosan (CS) hydrogel was selected to be used for preparation of the bone scaffolds. However, the 3D printing of CS-based hydrogels is still under early exploration. Knowing the fact that natural polymers are not so competent at holding large amounts of water, poly(vinyl alcohol) as the second polymer was employed. The novelty of the present research lies in the concept of employing sol‐gel chemistry in order to attain proper viscosity and rheological behavior to give self-standing filaments of the polymer blends. Employing sol–gel reaction in the preparation of the hybrid hydrogels had the advantage of endowing shape fidelity to the polymer blend without any solidifying in the needle. The obtained organic-inorganic hybrids were directly printed and subsequently cross-linked. The best performance in terms of mechanical strength, cell viability, and bio-mineralization was observed for the 50:50 ratio. The in vitro cell culture and the bioactivity results showed that the printed scaffolds with this method have great potential in bone tissue engineering. Further, this method could be expandable to print other hydrogels with diverse applications such as implantable devices, soft robotics, etc.

Improving sulfate and chloride resistance in eco-friendly marine concrete: Alkali-activated slag system with mineral admixtures

This study investigates the effects of various mineral admixtures, such as fly ash, metakaolin, and limestone powder, on the mechanical, chloride, and sulfate resistance properties of alkali-activated slag (AAS). The resistance of alkali-activated concrete (AAC) to chloride and sulfate is evaluated using the rapid chloride migration (RCM), wetting-drying cycles, SEM and XRD, TG/DTG. The results reveal that introducing fly ash improves workability but degrades the strength and durability of AAS. The 15% slag substitution by metakaolin is recommended to improve durability. Incorporating 15% limestone powder increases the compressive strength and reduces porosity due to filling and nucleation effects. The replacement ratio of 30% for each mineral admixture induces a considerable Ca2+ dilution, resulting in reducing the strength and durability of AAC. Under short-term wetting-drying cycles, the continued hydration of raw materials under MgSO4 erosion and the subsequent production of gypsum, hydrotalcite, and brucite from the matrix initially increase the AAC strength. However, the continued substitution of calcium in the C-(A)-S-H gel by magnesium and precipitation of gypsum under excessive cycles adversely deteriorates the compressive strength. The chloride migration degree in AAC is closely related to the porosity. Although the porous gel N-A-S-H facilitates chlorine migration in accelerated tests, it prevents further chlorine penetration by adsorbing chloride ions in large quantities, exhibiting the dominant effect on chloride immobilization. The formation of Friedel's salt, stemming from the chemical bonding of chloride, is present only in the high-calcium specimen G100 and the highly reactive aluminum specimen G85M15. Improvements in the gel chemistry and porosity are key factors in bolstering the durability of AAC. The findings of this study contribute to advancing the application of eco-friendly AAC in marine environments.

Structural and energetic characterization of silica-alumina gels for adsorption processes

The surface chemistry of silica-alumina gels is largely determined by number and type of silanol groups present. However, until now the influence of different silanol groups on adsorption processes is largely unknown. The aim of this study is to develop a method for an energetic characterization of silica-alumina gels by combining data measured by nuclear magnetic resonance (NMR), thermogravimetric analysis (TGA) and adsorption calorimetry. The silica-alumina gels used for the studies are systematically modified by pretreating at temperatures between 200 °C and 1000 °C. To quantify number and distribution of silanol groups, complementary data from 29Si-NMR and 1H NMR and thermogravimetric measurements is combined. Adsorption measurements with the adsorptives cyclopentane (nonpolar) and pyrrolidine (polar molecule capable of hydrogen bonding) provide further information. Based on the adsorption isotherms and load-dependent heats of adsorption, it is shown that number and distribution of silanol groups have little effect on the adsorption of cyclopentane. In contrast, different energy levels are found for the heat of adsorption of pyrrolidine at ∼106 kJ mol−1, ∼95 kJ mol−1, ∼87 kJ mol−1, and ∼80 kJ mol−1 depending on pretreatment temperature. Based on the combination of all data, a model is proposed to assign the identified energy levels of adsorption to different silanol groups.

A biocompatible electrolyte enables highly reversible Zn anode for zinc ion battery

Progress towards the integration of technology into living organisms requires power devices that are biocompatible and mechanically flexible. Aqueous zinc ion batteries that use hydrogel biomaterials as electrolytes have emerged as a potential solution that operates within biological constraints; however, most of these batteries feature inferior electrochemical properties. Here, we propose a biocompatible hydrogel electrolyte by utilising hyaluronic acid, which contains ample hydrophilic functional groups. The gel-based electrolyte offers excellent anti-corrosion ability for zinc anodes and regulates zinc nucleation/growth. Also, the gel electrolyte provides high battery performance, including a 99.71% Coulombic efficiency, over 5500 hours of long-term stability, improved cycle life of 250 hours under a high zinc utilization rate of 80%, and high biocompatibility. Importantly, the Zn//LiMn2O4 pouch cell exhibits 82% capacity retention after 1000 cycles at 3 C. This work presents a promising gel chemistry that controls zinc behaviour, offering great potential in biocompatible energy-related applications and beyond.

Design and fabrication of a new sol-gel based sensor for the visual detection of oxalate and investigation of the effect of boiling on the oxalate content of some foods

Sol–gel chemistry is a unique method for constructing high-performance flexible sensors. Sol-gel silica matrices doped with a controlled amount of sensing agent (dopant) lead to the fabrication of suitable sensors. According to this knowledge, we decided to describe the development and performance characteristics of the sol-gel glasses with a nanoporous structure as the novel naked eye sensor for fast detection of oxalate based on the incorporation of indole inside pores of the silica matrix obtained by sol–gel technology. Several sols were made with different water: alkoxide ratios and pHs to design a highly sensitive and selective thin film without dopant leaching. The Field emission scanning electron microscopy (FE-SEM) technique was employed to evaluate the surface morphology and porosity growth. Also, the sol–gel films were characterized by Fourier-transform infrared (FTIR) spectroscopy. The optimum performance in terms of sensitivity, leaching, and response time was achieved using water: alkoxide ratio of 4:1, water acidity (HCl concentration) of 0.01 M, and ethanolic solution of Indole 0.01 mol L-1. The calibration plot was obtained within 0.01–6.00 μg mL−1 of oxalate with a detection limit value of 0.005 μg mL−1. Meanwhile, the prepared sensor exhibited excellent and acceptable RSDs for both inter-day and intra-day precision. The present sensor was used to measure oxalate in various samples and investigate the effects of the celeryʼs cooking time and the brewing duration of tea on oxalate content.

Water separation from diesel fuel using high surface area 3D-printed aerogel constructs

This work reports removal of emulsified water droplets from ultralow sulfur diesel (ULSD) fuel using high surface area aerogel filter media constructs. A synergistic combination of additive manufacturing and sol–gel chemistry is used for fabrication of the filter media constructs from high surface area (>200 m2/g) and high porosity (>90%) polyimide and syndiotactic polystyrene aerogels that are grown using sol–gel processes inside the load-bearing 3D-printed polymeric constructs of polyamide and high impact polystyrene respectively. This paper evaluates the roles of several factors on water separation efficiency, such as surface energy of polymer media on wetting, surfactant adsorption by the high surface area polymer media, and size exclusion of water droplets by smaller aerogel pores. The surfactant-stabilized water droplets in ULSD can be removed with a separation efficiency of up to 95% using these mechanically strong aerogel constructs.

Toluene‐Mediated Morphology Tuning of Diblock Copolymer‐Templated Porous Si/Ge/K/C Thin Films for Li‐Ion Batteries

Amphiphilic diblock copolymer poly(styrene‐b‐ethylene oxide) templating in combination with sol–gel chemistry is utilized to synthesize porous mixed silicon/germanium/potassium/carbon (Si/Ge/K/C) thin films. As a Si/Ge source, the dissolvable Zintl phase K12Si12Ge5 is used. The toluene‐mediated morphological changes in the porous mixed Si/Ge/K/C thin films are studied with scanning electron microscopy and grazing incidence small/wide‐angle X‐Ray scattering. A dichloromethane solvent vapor annealing step is applied to study the additional morphological transformation inside the films. Since Ge and Si are promising anode materials in Li‐ion batteries, CR2032 half‐cells are manufactured with the porous mixed Si/Ge/K/C thin films and characterized by cyclic voltammograms, cycling, and impedance spectroscopy.

Predicting organic structures directing agents for zeolites with conditional deep learning generative model

Organic structures directing agents (OSDAs) are important components of the synthesis of zeolites, and their molecular properties play a significant role in the design of zeolite structures. As of yet, scientists have usually used priori knowledge to select suitable OSDAs for synthesis of specific structures of zeolites. We utilize a comprehensive database of OSDAs, zeolites, and gel chemistry to develop a computationally efficient model with fewer parameters based on self-attention mechanism and Long and Short-term Memory networks (LSTM) for modeling the interactions between OSDAs, zeolite structures and gel chemistry. Our model is able to learn the simplified molecules input line-entry system (SMILES) syntax and grasp molecular physicochemical properties by comparing the custom metric and weighted holistic invariant molecular (WHIM) descriptor after dimensionality reduction. Our model is capable of producing OSDA-like molecules under the conditions of zeolite structures and chemical gels, and predicting OSDA molecules for the specific structures of zeolites.

Orthogonal Gelations to Synthesize Core-Shell Hydrogels Loaded with Nanoemulsion-Templated Drug Nanoparticles for Versatile Oral Drug Delivery.

Hydrophobic active pharmaceutical ingredients (APIs) are ubiquitous in the drug development pipeline, but their poor bioavailability often prevents their translation into drug products. Industrial processes to formulate hydrophobic APIs are expensive, difficult to optimize, and not flexible enough to incorporate customizable drug release profiles into drug products. Here, a novel, dual-responsive gelation process that exploits orthogonal thermo-responsive and ion-responsive gelations is introduced. This one-step "dual gelation" synthesizes core-shell (methylcellulose-alginate) hydrogel particles and encapsulates drug-laden nanoemulsions in the hydrogel matrices. In situ crystallization templates drug nanocrystals inside the polymeric core, while a kinetically stable amorphous solid dispersion is templated in the shell. Drug release is explored as a function of particle geometry, and programmable release is demonstrated for various therapeutic applications including delayed pulsatile release and sequential release of a model fixed-dose combination drug product of ibuprofen and fenofibrate. Independent control over drug loading between the shell and the core is demonstrated. This formulation approach is shown to be a flexible process to develop drug products with biocompatible materials, facile synthesis, and precise drug release performance. This work suggests and applies a novel method to leverage orthogonal gel chemistries to generate functional core-shell hydrogel particles.

Low Fouling Marine Coatings Based on Nitric Oxide-Releasing Polysaccharide-Based Hybrid Materials

Diethylenetriamine-modified heparin and alginates as well as unmodified polysaccharides were combined using sol–gel chemistry to construct hybrid material thin-film coatings. Due to the high density of amine groups, the hybrid material coatings are capable of binding nitric oxide when exposed to NO at elevated pressures, which were characterized by UV–Vis and ATR-FTIR spectroscopy. When exposed to aqueous environments, the hybrid material coatings showed nitrogen oxide release rates between 17 and 30 pmol·cm–2·s–1. Marine antifouling properties were tested against the marine bacterium Cobetia marina and the diatom Navicula perminuta. The diatom assays revealed a lower settlement on the nitric oxide-loaded hybrid materials compared to hybrid materials without nitrogen oxide release. All coatings readily suppressed attachment of the marine bacterium C. marina. The advantages of hybrid materials, composed purely of polysaccharides and siloxanes, are that their building blocks are environmentally friendly, biodegradable, and biocompatible. This makes them interesting candidates for environmentally benign marine protective coating applications. In particular, the binding of nitric oxide and release of nitrogen oxide species as naturally occurring signaling molecules were found to be promising mechanisms to add additional fouling inhibiting functionality to deter marine organisms from settlement.

Degradation of alkali-activated slag subjected to water immersion

In this study, the impacts of tap water immersion on the pore solution, phase assemblages, gel chemistry and structure, and pore structure of alkali-activated slag (AAS) pastes were studied. AAS degrades under such condition and the potential mechanisms can be concluded as lower reaction rates, gel decomposition and carbonation. The leaching of Na+ and OH− at early stages hinders the reaction of slag, which leads to a slower formation of reaction products. Long-term leaching can result in gel decomposition after 90 d. Coarsened gel pores and capillary pores are both identified in water-immersed samples. Additionally, the leached Ca2+ can react with the dissolved CO2 in tap water to form calcium carbonate. A calcium carbonate layer is observed surrounding the paste while the inner matrix is free of carbonation. The insights provided by this paper contribute to understanding the behaviors and durability of AAS in underwater conditions.

Starch-Directed Synthesis of Worm-Shaped Silica Microtubes

Many strategies have been adopted to prepare silica materials with highly controlled structures, typically using sol-gel chemistry. Frequently, the alkoxysilanes used in sol-gel chemistry are based on monoalcohols, e.g., Si(OEt)4. The structural control over silica synthesis achieved by these precursors is highly sensitive to pH and solvency. Alkoxysilanes derived from the sugar alcohol glycerol (diglycerylsilane) react more slowly and with much less sensitivity to pH. We report that, in the presence of cooled aqueous starch solutions, glyceroxysilanes undergo transesterification with the sugars on starch, leading to (hollow) microtubules resembling worms of about 400 nm in diameter. The tubes arise from the pre-assembly of starch bundles, which occurs only well below room temperature. It is straightforward to treat the first-formed starch/silica composite with the enzyme amylase to, in a programmed fashion, increasingly expose porosity, including the worm morphology, while washing away untethered silica and digested starch to leave an open, highly porous materials. Sintering at 600 °C completely removes the starch silane moieties.

Sol-gel derived porous aluminum oxide cryogel – Fiber composite systems

The main aim of present research was to develop a new low-cost synthesis route to produce ultralight Al2O3 cryogel – fiber composite materials for high temperature insulation. The Al2O3 fibers give the matrix in these composites, instead of the typical reinforcement phase. The synthesis of precursor systems of fiber drawing and freeze drying is based on sol–gel chemistry. The starting materials (inorganic Al salts, organic solvents, and additives) were the same for both type of porous Al2O3 systems. The length of fibers (5–10 cm) is sufficient to form a matrix in the composites. The average diameter of fibers is 10 µm; the size of cryogel particles is generally 20–30 µm in the composites. The composite systems were characterised by 2D and 3D SEM, N2 sorption analysis, FTIR spectroscopy, thermal conductivity measurements, thermo-vacuum, vibration, and satellite tests.