Gel Growth Research Articles

Nano-rods oxide materials for biosensor application.

Iron ions selective biosensor (Fe3+) based on zinc oxide nano-rods thin film symbolic as ZnO-(NRs)TF will be developed and prepared. The potentiometric response for ZnO-(NRs)TF deposited on conducting plastic and silicon substrates as working electrode versus reference electrode (Ag/AgCl) was found to be linear against logarithmic FeCl3 with concentration range between 10-6 M and 10-2 M. The ZnO-(NRs)TF will be grown on conducting plastic and silicon substrates using two methods (Sol - Gel and aqueous chemical growth (ACG)) by seed layers and nano-rod growth will be investigated. For fabricate an advanced extracellular iron biosensor, the ZnO-(NRs) on plastic and silicon substrates were coated with a thin layer of specific ionophore membrane to be used for iron concentration measurements in extracellular solution. The prepared sample crystallinity and microstructure will be characterized by x-ray diffraction (XRD) which, imply that ZnO-(NRs)TF sample crystallite sizes are in the nano-scale. The prepared samples morphology was characterized by Field emission scanning electron microscope (FESEM).

Fabrication of multi-compartmentalized mesoporous silica microspheres through a Pickering droplet strategy for enhanced CO2 capture and catalysis

It is a long-standing dream to fabricate micron-sized inorganic spheres that have nanocompartments enclosed by a permeable shell and thus resemble the shape of natural cells. Here, we demonstrate a novel synthesis protocol to attain this goal for the first time. This protocol unprecedentedly harnesses interfacial sol–gel growth around Pickering droplets coupled with a surfactant assembly-directed sol–gel process within droplet-confined spaces. This protocol enables us to fabricate novel mesoporous silica microspheres (MSMs) with tunable interior architectures, such as hollow MSMs, hollow nanosphere-containing MSMs (hn@MSMs), nanosphere-containing MSMs (n@MSMs), yolk-shell-structured MSMs (y@MSMs) and “solid” MSMs. The obtained multi-compartmentalized MSMs exhibit good permeability to external molecules and good mechanical strength against stress. Moreover, their structural features benefit practical applications of CO2 capture and enzymatic reactions. Due to the high dispersion of tetraethylenepentamine and enzyme in the spatially separated nanocompartments, the developed CO2 sorbents and catalysts exhibit significantly enhanced CO2 capture efficiency and catalysis efficiency. Meanwhile, owing to the encapsulation of these nanocompartments inside the hollow micron-sized spheres, these CO2 sorbents and catalysts can be packed directly in fixed-bed reactors, which is unattainable for nanoparticle materials.

Generalized Gelation Theory Describes Onset of Online Extremist Support.

We introduce a generalized form of gelation theory that incorporates individual heterogeneity and show that it can explain the asynchronous, sudden appearance and growth of online extremist groups supporting ISIS (so-called Islamic State) that emerged globally post-2014. The theory predicts how heterogeneity impacts their onset times and growth profiles and suggests that online extremist groups present a broad distribution of heterogeneity-dependent aggregation mechanisms centered around homophily. The good agreement between the theory and empirical data suggests that existing strategies aiming to defeat online extremism under the assumption that it is driven by a few "bad apples" are misguided. More generally, this generalized theory should apply to a range of real-world systems featuring aggregation among heterogeneous objects.

Process study about silica anti-reflection coatings prepared by sol–gel method for cadmium telluride solar cells

Silica (SiO2) thin films with different refractive indexes as the anti-reflection coating for cadmium telluride (CdTe) solar cells were prepared by sol–gel method in this paper. In order to obtain the preparation process of SiO2 films with suitable refractive index, the different hydrolysis processes relied on the acid-base environment as well as the ratio of reactants was studied, respectively. It mainly includes that (I) the gel growth model in hydrogen or hydroxide ion environment provided by hydrochloric and ammonia. (II) The ratio of solvent, precursor and catalyst under base catalysis. (III) The weight and amount of polyethylene glycol molecular which is an additive agent to increase the porosity of sol film under acid catalysis. Based on the results above, a monolayer SiO2 coating with optimized refractive index was applied onto the glass substrate of CdTe solar cell, and the quantum efficiency has been enhanced at the band of 400–800 nm. After that, multilayer SiO2 coatings with high–low refractive indexes were designed according to the Fresnel theory to achieve wider spectrum (390–870 nm) enhancement. The broadband anti-reflection coatings (BARCs) were deposited on CdTe solar cell. The results were not consistent with expectations, which required further study about process matching between BARCs and device manufacture.

Production of Silica from Agricultural Waste

The most common generated waste synthesized is rice husk and palm ash, which shown high silica contain as 90-98% and 45- 50%, in respectively [1,2]. Silica produced from these wastes were synthesized mainly using acid leaching treatment. In this study, we focused on the synthesized of other sources silica through sol-gel method. The source such as sugarcane bagasse, corn cob, bamboo stem, and bamboo leaf, till now is still not widely explored, hence become the basis to study the amount of silica that been extracted. Within the scope of study, it shown that several factors play a vital role in determining the silica content of the material, including the species of source material, soil content of source material, maturation etc. Sol-gel synthesis is one of the most common method of converting ash into silica gel. In this process, silica was synthesized from ash through simultaneous hydrolysis and condensation reaction where a sol of sodium silicate, silicon alkoxide or halide gels converted into a polymeric network of gel [3]. The synthesis of silica using this method, lead to silica precipitation under certain conditions like restriction of gel growth that involved coagulation and precipitation step during its preparation [4]. Silica gel synthesize through this method also known as xerogel. The purification and drying produce silica in amorphous powder form that remove any impurities or organic matter that usually contain in waste [1].

Cylindrical Couette flow of Laponite dispersions

Abstract Taylor-Couette flow of aqueous dispersions of nanometric Laponite platelets was studied by dynamic light scattering and direct observation. Despite high rotation rates, gel growth was observed starting from the stator, and filling almost the whole gap after some period of time depending on the angular velocity of the rotor. SEM microscopy observations of the flowing liquid showed the presence of spheres in the micrometer range. A mechanism for gel growth is proposed, where lumps of gel are formed in the sheared liquid and form spherical aggregates which eventually adhere to the side of the gel, with a progressing gelling front.

Steady-state crack growth in polymer gels: A linear poroelastic analysis

Based on a linear poroelastic formulation, we present an asymptotic analysis of the crack tip fields for steady-state crack growth in polymer gels. A finite element method is then developed for numerical analysis. A semi-infinite crack in a long strip specimen subject to plane-strain loading is studied in detail. The crack-tip fields from the numerical analysis agree with the asymptotic analysis with a poroelastic stress intensity factor, which is generally smaller than the stress intensity factor predicted by linear elasticity due to poroelastic shielding. Similarly, the crack-tip energy release rate calculated by a modified J-integral method is smaller than the applied energy release rate. The size of the poroelastic crack-tip field (or K-field) is characterized by a diffusion length scale that is inversely proportional to the crack speed. For relatively fast crack growth, the diffusion length is small compared to the strip thickness (small-scale diffusion), and the poroelastic K-field transitions to an elastic K-field at a distance proportional to the diffusion length. In this case, the crack-tip energy release rate decreases with increasing crack speed under the same loading condition. For relatively slow crack growth, the diffusion length is greater than the strip thickness (large-scale diffusion), and the poroelastic crack-tip field is confined and transitions to a one-dimensional diffusion zone ahead of the crack tip. In this case, the energy release rate increases with increasing crack speed. Both immersed and not-immersed crack face conditions are considered. Under the same loading conditions, the poroelastic stress intensity factor and the modified J-integral are higher for the immersed case than not-immersed, but they approach the same values at the fast and slow crack limits. In general, if the crack-tip energy release rate is taken to be the intrinsic fracture toughness of the gel, the applied energy release rate as the apparent fracture toughness is greater due to energy dissipation associated with solvent diffusion, which is referred to as poroelastic toughening. It is proposed that the modified J-integral can be used to determine the intrinsic fracture toughness of the gel in experiments, which may or may not depend on crack speed. Moreover, the present results are found to be qualitatively consistent with previous experiments on the effects of solvent viscosity and crack-tip soaking.

Medicinal Implication of Syzygium Cumini Nut on the Growth of Brushite Crystals

Brushite crystal formation and deposition is the central cause for recurrent kidney stone disease among the global population. The present study was aimed to rationalize the use of syzygium cumini nut on the brushite crystal formation invitro and to investigate the mechanism of action. Brushite crystals were grown at room temperature by single diffusion gel growth technique and the growth influencing study of these crystals in the presence of the natural product of syzygium cumini nut were carried out. The number of nucleated crystals was found to be less for the syzygium cumini nut extract added system when compared to the control system. The scanning electron micrograph images shows plate like morphology for the grown crystals. The thermal analysis shows that there is a decrease in the stability for the crystals grown in the presence of the syzygium cumini nut extract. By carefully observing the morphology and size of the crystals obtained, it is concluded that the syzygium cumini nut extract partially inhibits the growth of brushite crystals, particularly on its size. The reduction in stability may be due to the interaction of the host molecule on the surface.

Insights into gelation kinetics and gel front migration in cation-induced polysaccharide hydrogels by viscoelastic and turbidity measurements: Effect of the nature of divalent cations

Polysaccharide-based hydrogels were prepared by the diffusion of various divalent cations (X2+) into the polygalacturonate (polyGal) solution through a dialysis membrane. The diffusion of various divalent cations (Mg2+, Ca2+, Zn2+ and Ba2+) was investigated. The polyGal gel growth was studied as a function of the initial cation concentration by both viscoelastic and turbidity measurements. We have demonstrated for the first time that the determination of the spatiotemporal variation of turbidity during the gelation process allowed to study the gel front migration. For Ca-polyGal, Zn-polyGal and Ba-polyGal, the gel front migration was characterized by the presence of a peak at the sol/gel interface. This peak was not observed in the case of Mg-polyGal where the gel was not formed. The apparent diffusion coefficient of the gel front (Dapp) which was calculated from the evolution of this peak increased when the initial cation concentration was increased. Moreover, we have suggested a gelation mechanism based on the presence of a threshold molar ratio R* (=[X2+]/[Galacturonic unit]) in which some point-like crosslinks are precursors of the formation of dimers and multimers inducing the contraction of the gel and thus the formation of the gel front.

Vitamin C inhibits crystallization of struvite from artificial urine in the presence of Pseudomonas aeruginosa.

ABSTRACTBackground:Formation of struvite stones is associated with urinary tract infection by urease-producing bacteria. Biogenic crystal growth in natural and synthetic materials is regulated by the action of inhibitors, ranging from small ions, molecules to large macromolecules.Materials and Methods:We report the dynamics of in vitro crystallization of struvite in presence of vitamin C in synthetic urine using single diffusion gel growth technique. Sodium metasilicate gel of specific gravity 1.05 and the aqueous solution of ammonium dihydrogen phosphate were used as the medium for growing the struvite crystals. The crystallization process was induced by a urease positive struvite stone associated Pseudomonas aeruginosa to mimic the infection leading to stone formation. The grown crystals were characterized by ATR-FTIR and powder XRD. The surface morphology was analysed through FE-SEM for comparison between treatments.Results:We observed decrease in number, dimension, and growth rate of struvite crystals with the increasing concentrations of vitamin C. Crystals displayed well-defined faces and dendritic morphology of struvite in both control and biogenic systems.Conclusion:The results strongly suggest that, vitamin C can modulate the formation of struvite crystals in the presence of uropathogenic bacteria.

Robust Super-Repellent Anisotropic Silica Films by Emulsion-Based Sol–Gel Growth

In this paper, anisotropic SiO2 with different morphologies were synthesized through an emulsion-based one-pot method by adding various silane coupling agents. Silane coupling agents affected the growth of silica nanostructures at the oil/water interfaces. Robust super-repellent film that showed great durability under different harsh conditions were obtained by bonding the self-assembled anisotropic silica nanostructures (ASN) film to substrate by the commercial acrylic adhesive. The film switched from superhydrophobic (157.1[Formula: see text] to superhydrophilic (0[Formula: see text] after being heat-treated at 500[Formula: see text]C. Further, silane treatment with addition of acid reduced the time of modification. Meanwhile, silane grafting density was improved and superhydrophobicity of calcinated ASN films was regenerated.

3D-2D lattice dimensionality, optical Eg and PL energy variations due to organic variant in two [ZnCl4]2- based hybrid materials

Single crystal growth of two inorganic-organic compounds, Bis[2-methylpyridine tetrachlorozincate] (MPCZ) and Bis[2-amino-5-chloropyridine tetrachlorozincate] (ACPCZ) has been achieved by two different methods i.e. Gel growth and Solution growth through slow cooling process. Due to change in organic moiety, the single crystal growth of ACPCZ could not be achieved by gel growth method whereas solution growth through slow cooling process results the single crystals of ACPCZ. Different physiochemical characterization techniques like single crystal XRD, UV–Vis spectroscopy, FESEM image analysis, luminescence property, etc. shows structure stability with charge assisted secondary interactions, lattice dimensionality (3D-2D) and interweaving design of two inorganic-organic hybrid materials. In MPCZ hybrid derivative, organic moiety form 3D spreader shape pattern and the inorganic moiety link the train of spreaders along ac-plane whereas the change in organic moiety in ACPCZ has 2D shear grade pattern of inorganic-organic components along b-axis with steepness grade of 1.29 Å and angle of inclination of 49.5°. The surface study of the hybrid materials indicate the average granular size of 28 nm for MPCZ whereas the image of ACPCZ shows variation in spatial parameters of average granular size of 60 nm due to alteration of organic derivative from 2-methylpyridine to 2-amino-5-chloropyridine. The change in optical energy direct band gap value from 3.01eV for MPCZ to 3.42eV for ACPCZ indicates the role of organic compounds in optical properties of hybrid materials. The photoluminescence energies and band gap electronic transitions were investigated with Photoluminescence emission spectra presents that the excitation energy changes from 2.83 eV to 2.06 eV in MPCZ and 2.80 eV–2.14 eV in ACPCZ.

Whether do nano-particles act as nucleation sites for C-S-H gel growth during cement hydration?

In this study, three modelling experiments were designed to investigate whether nano-particles incorporated in the cement paste act as nucleation sites for CSH gel growth during cement hydration. The nano-particles with (nano-SiO2) and without (nano-TiO2) pozzolanic reactivity were used. In the first experiment, both the cement and nano-particles were dispersed in water to prepare dilute cement paste, in which the cement and nano-particles can contact each other. In the second one, the cement particles were laid inside a filter paper funnel and immersed in tap and ultrapure water with nano-particles dispersed, in order to separate the cement particles with nano-particles by using the filter paper. In the third one, large clinker particle was embedded in resin, surface-polished and then exposed upside down in ultrapure water with and without nano-particles dispersed. After hydration for 7 days, the hydration products in the paste or the nano-particle dispersion were observed by using TEM and the hydrated surface of the embedded clinkers were detected by using SEM. Based on the experimental results and the detailed discussions by using the classic nucleation theory, it was found that there may have no nucleus function of the nano-particles for the CSH gel precipitation during cement hydration, at least in the hydrating system with nano-silica and nano-TiO2 addition. It was proposed to more reasonably explain the observations in the three modelling experiments by using the topochemical reaction instead of the through-solution mechanism for the CSH gel formation.

Morphological and FTIR Studies of Barium Oxalate Single Crystals

Abstract The conditions for the gel growth of barium oxalate single crystals in silica gels were studied in this paper. We describe the growth mechanism, effect concentration of feed solution, interchanging of the reactants, the effect of temperature and detailed study of microstructures of barium oxalate single crystals. At higher concentration of feed solution dense fibers were observed. With interchanged feed solution precipitate and spherulites have been obtained. The effect of temperature on growth barium oxalate crystals showed that there was a decrease in nucleation density at higher temperature. The crystals growth were observed under the electron microscope which revealed that the crystal have needle and spherulites structures. We also report the FTIR studies of barium oxalate crystals.

Selective incorporation of foreign functionality into fibrin gels through a chemically modified DNA aptamer

We found for the first time that a thrombin-binding DNA aptamer (TBA) is selectively entrapped in fibrin gels during the gel growth reaction catalyzed by thrombin. Furthermore, using this phenomenon, we successfully demonstrated multiple incorporation of amphiphilic aliphatic groups into fibrin gels via chemically modified TBA.

Crystal Growth of High-Quality Protein Crystals under the Presence of an Alternant Electric Field in Pulse-Wave Mode, and a Strong Magnetic Field with Radio Frequency Pulses Characterized by X-ray Diffraction

The first part of this research was devoted to investigating the effect of alternate current (AC) using four different types of wave modes (pulse-wave) at 2 Hz on the crystal growth of lysozyme in solution. The best results, in terms of size and crystal quality, were obtained when protein crystals were grown under the influence of electric fields in a very specific wave mode (“breathing” wave), giving the highest resolution up to 1.34 Å in X-ray diffraction analysis compared with controls and with those crystals grown in gel. In the second part, we evaluated the effect of a strong magnetic field of 16.5 Tesla combined with radiofrequency pulses of 0.43 μs on the crystal growth in gels of tetragonal hen egg white (HEW) lysozyme. The lysozyme crystals grown, both in solution applying breathing-wave and in gel under the influence of this strong magnetic field with pulses of radio frequencies, produced the larger-in-size crystals and the highest resolution structures. Data processing and refinement statistics are very good in terms of the resolution, mosaicity and Wilson B factor obtained for each crystal. Besides, electron density maps show well-defined and distinctly separated atoms at several selected tryptophan residues for the crystal grown using the “breathing wave pulses”.

Hybrid 3D printing and electrodeposition approach for controllable 3D alginate hydrogel formation

Calcium alginate hydrogels are widely used as biocompatible materials in a substantial number of biomedical applications. This paper reports on a hybrid 3D printing and electrodeposition approach for forming 3D calcium alginate hydrogels in a controllable manner. Firstly, a specific 3D hydrogel printing system is developed by integrating a customized ejection syringe with a conventional 3D printer. Then, a mixed solution of sodium alginate and CaCO3 nanoparticles is filled into the syringe and can be continuously ejected out of the syringe nozzle onto a conductive substrate. When applying a DC voltage (∼5 V) between the substrate (anode) and the nozzle (cathode), the Ca2+ released from the CaCO3 particles can crosslink the alginate to form calcium alginate hydrogel on the substrate. To elucidate the gel formation mechanism and better control the gel growth, we can further establish and verify a gel growth model by considering several key parameters, i.e., applied voltage and deposition time. The experimental results indicate that the alginate hydrogel of various 3D structures can be formed by controlling the movement of the 3D printer. A cell viability test is conducted and shows that the encapsulated cells in the gel can maintain a high survival rate (∼99% right after gel formation). This research establishes a reliable method for the controllable formation of 3D calcium alginate hydrogel, exhibiting great potential for use in basic biology and applied biomedical engineering.

GROWTH CHARACTERIZATION OF CALCIUM HYDROGEN PHOSPHATE DIHYDRATE CRYSTALS INFLUENCED BY COSTUS IGNEUS AQUEOUS EXTRACT

Objective: To investigate the inhibitory effect of aqueous extract of leaves, stems and rhizome of Costus igneus on the growth of calcium hydrogen phosphate dihydrate (CHPD) crystals.Methods: Calcium hydrogen phosphate dihydrate (CHPD) crystals were grown by the single diffusion gel growth technique and the inhibitory effect of aqueous extracts of leaves, stems and rhizome of Costus igneus on the growth of CHPD crystals has been studied. The grown crystals were characterised by Fourier Transform Infrared Spectroscopy (FTIR), Powder X-Ray diffraction (XRD) for further confirmations.Results: With an increase in the concentration of aqueous extract of Costus igneus, the weight of the formed crystals were gradually reduced from 2.03 g to 0.06 g (leaves), 0.05 g (rhizome), 0.03 g (stem) for the CHPD crystals, respectively. The crystals harvested from the CHPD were characterised by Fourier Transform Infrared Spectroscopy (FTIR) to confirm the functional groups, and Powder X-Ray Diffraction technique (XRD) analyses to confirm the crystalline phases of the CHPD and hydroxyapatite (HAP) crystals. Results obtained indicated that Costus igneus (leaves, stems and rhizome) has the potential to inhibit the formation of calcium hydrogen phosphate dihydrate crystals.Conclusion: This study confirms that using an aqueous extract of stem and rhizome of Costus igneus can promote the formation of hydroxyapatite (HAP) crystals and reduce the nucleation rate of CHPD crystals, a major component of calcium urinary stone.

An investigation of the possibilities of ultrasound intensification of the impregnation process of porous multiple glass units using LBS-4 bakelite lacquer

In this paper, the results of an experimental investigation of the dependence of the viscosity of an LBS-4 bakelite lacquer on the conditions of ultrasound treatment (UST) are given. It is shown that the predominant factor of the decrease in the viscosity of the LBS-4 bakelite lacquer is the temperature of heating. It is determined that heating by means of UST should be preferred due to ease of exposure on the binder during the flow process. It is shown that the hangover time during impregnation should be reduced, because this results in gel formation and growth of viscosity and that the generation of gel formation using UST may reduce the time of drying of the workpiece between impregnation procedures.

Dissolution studies in few urinary type crystals

Kidney stones are hard, solid particles that form in the urinary tract. The stones were very small and can pass out of the body without any problems. Calcium containing stone, especially Calcium Oxalate Monohydrate, Calcium Oxalate Di- hydrate and basic Calcium Phosphate, Calcium Hydrogen Phosphate Di-hydrate, Struvite and are the most commonly occurring stones. Calcium Oxalate Monohydrate crystals are grown in single diffusion gel growth technique. The grown crystals are characterized by FTIR, XRD and inhibition studies. A number of medicinal plants were antiurolithiatic activity such as Tribulus terrestriis and Boerhaavia diffusa Linn were carried out. Calcium Oxalate Monohydrate crystals in the presence of the herbal extract of one of the medicinal plants Tribulus terrestris Linn. The results are discussed.