A new type of multistimuli‐responsive hydrogels cross‐linked by metal ions and biopolymers is reported. By mixing the biopolymer chitosan (CS) with a variety of metal ions at the appropriate pH ...values, we obtained a series of transparent and stable hydrogels within a few seconds through supramolecular complexation. In particular, the CS–Ag hydrogel was chosen as the model and the gelation mechanism was revealed by various measurements. It was found that the facile association of Ag+ ions with amino and hydroxy groups in CS chains promoted rapid gel‐network formation. Interestingly, the CS–Ag hydrogel exhibits sharp phase transitions in response to multiple external stimuli, including pH value, chemical redox reactions, cations, anions, and neutral species. Furthermore, this soft matter showed a remarkable moldability to form shape‐persistent, free‐standing objects by a fast in situ gelation procedure.
Turning to jelly: A series of metal–biopolymer hydrogels is obtained by ultrafast supramolecular complexation. The hydrogels are easily prepared, have high water content, and are stable at room temperature. The multistimuli‐responsive Ag‐based hydrogel can be molded to form shape‐persistent, free‐standing objects.
We report the synthesis and Fourier Transform Infrared spectroscopy characterization results dealing with the surface modification of silica aerogels obtained via a two-step sol–gel process where ...various silicon precursors and co-precursors were used. The hydrolysis and poly-condensation steps were followed by carbon dioxide supercritical drying (
T
c
=
31.1
°C;
P
c
=
73.7
bar). The silicon precursors contain four identical hydrolysable alkoxy groups (methoxy or ethoxy), while in the co-precursors, one of the alkoxy groups is substituted by a non-hydrolysable alkyl group (methyl, ethyl,
n-propyl,
iso-butyl,
n-octyl, vinyl or phenyl). Identically, surface-functionalized silica aerogels were obtained from various silicon precursor/co-precursor combinations and their chemical structures were compared. The infrared spectroscopy revealed the existence of chemically comparable solid networks with some differences due to the nature of the silicon precursors.
In this work, hydrophobic surfaces on cotton fabrics were obtained using a sol–gel technique to produce coatings applied using a spray of precursor solution followed by drying and heat treatments. ...Different types of treatments using the sol–gel process were performed in order to assess the influence on fabric hydrophobicity, with alteration of parameters including the concentrations of citric acid and tetraethyl orthosilicate (TEOS), the number of sprays, and curing of the fabric after obtaining the hydrophobic coating. The absorption of water into material samples were tested according to the AATCC test method 79. Scanning electron microscopy, contact angle, and Fourier-transform infrared spectroscopy (FT-IR) analysis were also studied. Excellent results were obtained for the contact angle (>150°), hence characterizing all the treatments as super-hydrophobic. FT-IR analyses revealed differences according to the citric acid concentration employed. The best results were obtained for samples treated using a higher concentration of citric acid and spraying the sol–gel solution twice. Mathematical models of the contact angle and the time for water absorption by the fabric treated with TEOS and citric acid showed good agreement with the experimental data.
Highlights
A hydrophobic coating on porous materials was achieved using a simple, single-step, and inexpensive procedure employing TEOS, citric acid, and ethanol, without any fluorinated compounds.
The hydrophobic solution was applied using a spray of fine droplets released at a distance of 15 cm from the porous material.
Better resistance to washing processes was obtained using higher concentrations of citric acid for formation of the hydrophobic solution employed for the porous coating on the cotton fabric.
Silicate-based bioactive glass nanoparticles (BGN) are gaining increasing attention in various biomedical applications due to their unique properties. Controlled synthesis of BGN is critical to their ...effective use in biomedical applications since BGN characteristics, such as morphology and composition, determining the properties of BGN, are highly related to the synthesis process. In the last decade, numerous investigations focusing on BGN synthesis have been reported. BGN can mainly be produced through the conventional melt-quench approach or by sol-gel methods. The latter approaches are drawing widespread attention, considering the convenience and versatility they offer to tune the properties of BGN. In this paper, we review the strategies of sol-gel processing of BGN, including those adopting different catalysts for initiating the hydrolysis and condensation of silicate precursors as well as those combining sol-gel chemistry with other techniques. The processes and mechanism of different synthesis approaches are introduced and discussed in detail. Considering the importance of the BGN morphology and composition to their biomedical applications, strategies put forward to control the size, shape, pore structure and composition of BGN are discussed. BGN are particularly interesting biomaterials for bone-related applications, however, they also have potential for other biomedical applications, e.g. in soft tissue regeneration/repair. Therefore, in the last part of this review, recently reported applications of BGN in soft tissue repair and wound healing are presented.
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•Sol-gel based approaches for BGN synthesis reviewed•Comparison of different sol-gel based methods for BGN production•Parameters controlling size, shape, porosity and composition of BGN discussed•Overview of biomedical applications of BGN besides bone regeneration
One plausible approach to endow aerogels with specific properties while preserving their other attributes is to fine‐tune the building blocks. However, the preparation of metallic aerogels with ...designated properties, for example catalytically beneficial morphologies and transition‐metal doping, still remains a challenge. Here, we report on the first aerogel electrocatalyst composed entirely of alloyed PdNi hollow nanospheres (HNSs) with controllable chemical composition and shell thickness. The combination of transition‐metal doping, hollow building blocks, and the three‐dimensional network structure make the PdNi HNS aerogels promising electrocatalysts for ethanol oxidation. The mass activity of the Pd83Ni17 HNS aerogel is 5.6‐fold higher than that of the commercial Pd/C catalyst. This work expands the exploitation of the electrocatalysis properties of aerogels through the morphology and composition control of its building blocks.
Function follows form: Aerogel electrocatalysts consisting of alloyed PdNi hollow nanospheres (HNS) were prepared. Their chemical composition and shell thickness can be controlled based on the ratio of the Ni/Pd precursors. The mass activity of the Pd83Ni17 HNS aerogel is 5.6 times higher than that of the commercial Pd/C catalyst.
•A CTAB-assisted sol–gel route to prepare tailor-made CaO sorbents.•A remarkable development in BET surface area and total pore volume.•A significant improvement in CO2 uptake capacity as well as ...stability.•A clear relationship between structures and its performance.
The use of calcium oxide (CaO) for the CO2 looping cycle has attracted increased attention due to several potential advantages. The main drawback of this cycle in practical applications is a sharp decay subsequent to a few cycles of carbonation–calcination. In this work, we report the development of synthetic CaO sorbents via a sol–gel method. Effect of Ca2+/CTAB molar ratios on physical properties of the CaO sorbents as well as their CO2 capture performance were investigated. The presence of CTAB was found to effectively prevent an agglomeration of CaO particles, and to greatly increase BET surface area and total pore volume of the resulting CaO sorbents. Volcano-shaped trends in the BET surface area and total pore volume with respect to the increase of CTAB concentration signal an optimum Ca2+/CTAB ratio. The CaO sorbent prepared with the Ca2+/CTAB molar ratio of 10:3 achieves the highest carbonation conversion of 76.55% in the first cycle, and retains an excellent carbonation conversion of 63.28% subsequent to 20 consecutive test cycles. Furthermore, the analysis results suggest the presence of two linear relationships between: carbonation conversion at reaction stage and BET surface area, and carbonation conversion at diffusion stage and CaO crystallite size.
•Superhydrophobic coatings were achieved via sol–gel processing of fluoroalkylsilane.•A hill-like morphology similar to the microstructure of the lotus leaf was observed.•Superhydrophobic coatings ...showed water contact angle of 169° and sliding angle of 5°.•Superhydrophobic coatings showed wetting stability against water jet impact test.•Stable plastron layer on coating was observed for 8h of continuous immersion in water.
Upon contact with a dusty superhydrophobic surface, moving spherical water drops collect the dust particles and eventually flow off the surface. Herein, we report a very simple one-step approach to fabricate transparent and self-cleaning superhydrophobic coatings via the sol–gel processing of long-chain fluoroalkylsilane. The coating surface exhibited a rough, wrinkled, hill-like morphology similar to the microstructure of the lotus leaf (rough micro-scale papillae), which is promising for superhydrophobicity. The air bags trapped in the rough, hill-like structure allow the water drops to take a round shape with a contact angle of 169°. These round water drops abruptly roll off the coating surface at less than 5° of tilting. No major or minor water-drop pinning was observed during the roll off. The dust-repellent (self-cleaning) property, plastron stability, and durability against water-jet impact were examined on the superhydrophobic coatings.
In this review article the available results about application of sol–gel synthesis method for the preparation of different calcium phosphates and composite materials are summarized. The attention is ...paid to calcium phosphate-containing compounds which show the biological properties and could be used as potential phosphate bioceramics in medicine. It was demonstrated that the sol–gel synthesis method is a powerful tool for the synthesis of calcium hydroxyapatite and other phosphates, and different calcium phosphate-based composites at mild synthetic conditions resulted in high reproducibility, high phase purity, and desired morphology. Thus, the sol–gel synthesis method enables the researchers to develop biomaterials with superior features in terms of biomedical applications.
For the synthesis of calcium phosphate biomaterials an effective sol–gel chemistry approaches have been developed. KI, EG, and AK. “Sol–gel synthesis of calcium phosphate-based biomaterials—A review of environmentally benign, simple, and effective synthesis routes”.
Highlights
The sol-gel chemistry approaches for synthesis of calcium phosphate biomaterials were observed.
Calcium hydroxyapatite, different calcium phosphates, and composites are discussed.
These CP biomaterials show a high biocompatibility and increased biological behaviour.
The sol-gel synthesis method is a powerful tool for the synthesis of CP biomaterials.
High reproducibility, high phase purity and desired morphology could be achieved.
This work describes the synthesis of chitosan hydrogel/SiO2 and chitin hydrogel/SiO2 hybrid mesoporous materials obtained by the sol–gel method for their use as biosorbents. Their adsorption ...capabilities against four dyes (Remazol Black B, Erythrosine B, Neutral Red and Gentian Violet) were compared in order to evaluate chitin as a plausible replacement for chitosan considering its efficiency and lower cost. Both chitin and chitosan were used in the form of hydrogels. This allowed full compatibility with the ethanol release from tetraethoxysilane. The hybrid materials were characterized by Attenuated Total Reflectance-Fourier Transform Infrared Spectroscopy (ATR-FTIR), Scanning Electron Microscopy (SEM), Energy Dispersive X-Ray Spectroscopy (EDS), Nitrogen Adsorption Isotherms and 13C solid-state Nuclear Magnetic Resonance. Adsorption experimental data were analyzed using Langmuir, Freundlich and Dubinin–Radushkevich isotherm models along with the evaluation of adsorption energy and standard free energy (ΔG0). The adsorption was observed to be pH dependent. The main mechanism of dye adsorption was found to be a spontaneous charge associated interaction, except for EB adsorption on chitin/SiO2 matrix, which showed to involve a lower energy physical adsorption interaction. Aside from highly charged dyes the chitin containing matrix has similar or higher adsorption capacity than the chitosan one.
Carbonyl compounds are ubiquitous quality trackers that provide information about food product degradation as well as air and water pollution levels. In addition, they are used as biomarkers for ...medical diagnoses. With more user-friendly sensors, their fast detection and easy quantification are highly relevant. The synthesis, characterization, and performance assessment of a new sensor based on aniline fluorescence to monitor carbonyls in real time is reported. A cost-effective synthesis using a straightforward sol-gel process led to the construction of a nontoxic silica-based material with high porosity, which can be used with almost no sample preparation. The material exhibits a rapid (< 1 min) fluorescence decrease upon interaction with carbonyl groups. The limit of detection is as low as ca. 5 × 10−4 mol·L−1 for hexanal, while fluorescence extinction occurs at much higher concentrations (5 × 10−1 mol·L−1), which enables the sensor to be used with a very broad range of detection. Real-time monitoring is possible since the fluorescence loss correlates with the concentration of carbonyl moieties. The performance was validated in simulating as well as in real media, making this sensor suitable for use in a wide range of applications.
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-Carbonyl monitoring is crucial in many domains-The usual techniques require time, expensive equipment, and toxic compounds-New fast, user-friendly and cost-effective sensors are required-A new fluorescent sol-gel sensor for multi-analyte detection was designed-Its performance in both modeling and real media was demonstrated
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