Journal articles: 'Silicic Acid Gels'

1

Arkles, Barry, Kevin King, and Keith Pannell. "Hydroxymethylsilanetriol – A Simple Analog of Silicic Acid." Silicon 5, no. 3 (2013): 187–97. https://doi.org/10.1007/s12633-013-9146-2.

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Hydroxymethyltriethoxysilane and hydroxymethyltrimethoxysilane, precursors by hydrolysis to a simple analog of silicic acid, hydroxymethylsilanetriol, were prepared. Hydroxymethyltrialkoxysilanes undergo condensation to form silmethyleneoxide oligomers and dimeric 2,2,5,5-tetraalkoxy-2,5-disila-1,4-dioxanes. Hydroxymethylsilanetriol undergoes condensation reactions similar to silicic acid and readily forms organosilicate structures by sol–gel processing techniques which may be converted at relatively low temperatures to silicon dioxide. Hydroxmethylsilanetriol derived gels were subject to less stress- cracking during drying than conventional tetraethoxysilane derived gels, suggesting that Si-O-C bond equilibration during drying provides a mechanism for stress-relief. In screening experiments, hydroxymethylsilanetriol appears to be a competitive inhibitor of the growth of the diatom C. fusiformis, a silicate dependent species, which produces silicate structures.

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Sukharev, Yu I., and V. V. Avdin. "Frequency-Diffusion Characteristics of Silicic Acid Gels." Materials Science Forum 480-481 (March 2005): 629–34. http://dx.doi.org/10.4028/www.scientific.net/msf.480-481.629.

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The discreteness of vibration frequencies of diffusion coefficients of rare - earth elements ions in the forming gel of silicon acid is considered. The existence of at least three vibration frequencies being more probable for the gel system in question is established. The agreement of these results with the experiments studying the behaviour of pacemakers in zirconium oxyhydrate gels is shown. This agreement and the frequency discreteness mentioned prove the early assumption [1] that structuring of different gels proceeds through the process of formation and interaction of stable sites in a polymer structure of a discrete size (attractor). The system of attractors is of a fractal nature. The regularities established reflect the general nature of the gelation with any types of a gelforming polymer and ions diffusing in the micellar solution.

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Benetková, Barbora, Adéla Peterová, Monika Slavíková, and Petr Kotlík. "Impact of Relative Humidity on Modified Alkoxysilane Gels." Key Engineering Materials 714 (September 2016): 95–99. http://dx.doi.org/10.4028/www.scientific.net/kem.714.95.

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Silicic acid esters have been used as stone consolidants for 50 years now. During this time they became the most popular consolidants for building materials, mainly thanks to their good properties during application. Despise all these positives, the use of alkoxysilanes brings also some drawbacks. The gel of the silicic acid esters, which is responsible for the consolidation, cracks and decays during several years after the treatment so that the consolidation has to be repeated. To suppress the cracking, the alkoxysilanes are often modified. In recent studies, we focused on modification of silicic acid ester gels by SiO2 and Al2O3 nanoparticles. Some of the prepared mixtures cracked less than the unmodified mixture under ambient condition. This work builds on these experiments and works with the selected modified mixtures. As the consolidants are widely used outdoors, it was necessary to compare the degree of cracking of modified gels under various conditions. In this experiment we focused on their cracking under different levels of relative humidity. As the objective evaluation of cracking was needed, we believe to come up with partial solution to this problem – to assort the extent of cracking to some defined category. The categories were defined according to our former experiences with observation of cracking states of the gels. We found out, that the change of relative humidity has huge impact on the way and extent to which the gels cracked. Knowing this information we may be able to prepare the modified consolidant, that better withstands outdoor conditions and thus to preserve our cultural heritage for longer time.

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Skorodumova, Olga, Olena Chebotareva, Andrey Sharshanov, and Andrey Chernukha. "Selection of precursors of safe silica-based fireproof coatings for textile materials." Problems of Emergency Situations, no. 37 (April 2023): 192–202. http://dx.doi.org/10.52363/2524-0226-2023-37-14.

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The selection of the inorganic precursor SiO2 as the main component of the simplified safe technology for obtaining flame-retardant coatings on textile materials was carried out. By thermo-graphic research of organic and inorganic SiO2 precursors, performed on an OD-102 deri-vatograph under conditions of heating at a rate of 10ºС/min in an air environment, the processes of decomposition of the coating that occur during the action of fire were investigated. Gels based on inorganic precursors produced by industry (silica sol, silica gel) and silicic acid, which was obtained by the exchange reaction of an aqueous solution of sodium silicate of liquid glass and acetic acid, were studied for the comparative characteristics of thermal destruction of coatings. As organic precursors of SiO2, gels of ethyl silicate-32 and methyltriethoxysilane were studied, which were obtained by hydrolysis of organosilicon compounds in an acidic water-alcohol medi-um with subsequent polycondensation of the hydrolysis products. The effect of temperature on the nature of thermal destruction of silica gel, silica sol, silicic acid and organosilicon gels of ethyl silicate and methylotriethoxysilane was investigated. It is shown that inorganic precursors differ favorably from organosilicon precursors in terms of the overall thermal effect during their de-composition, mass loss during heat treatment, and the rate of change of this parameter. Consider-ing that, in addition to total mass loss, the increase in mass loss during heating is less than 1 % in compositions based on inorganic precursors, it is possible to use all three types of inorganic pre-cursors, but from the point of view of acidity and safety of impregnation compositions, prefer-ence is given to silicic acid obtained by the exchange reaction of silicate sodium liquid glass with acetic acid.

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Hwang, Hae Jin, Chul Eui Kim, and Young Chul Cha. "Strengthening of Water Glass Based Aerogel by TEOS." Materials Science Forum 544-545 (May 2007): 1053–56. http://dx.doi.org/10.4028/www.scientific.net/msf.544-545.1053.

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In order to prevent the irreversible collapse of the silica aerogel backbone upon the drying of the liquid phase of silica wet gel derived from water glass based silicic acid, we tried to strengthen the aerogel back bone by aging silica wet gels in water and TEOS/ethanol solutions. Although aging of silica wet gels in water has been shown to grow the neck between silica particles of the aerogel backbone, it is hard to obtain a crack-free aerogel monolith. On the other hand, the mechanical stability of silica aerogels was improved significantly by aging the wet gel in TEOS/ethanol solutions with different TEOS content.

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6

Plško, Alfonz, Anton Lukáč, Jana Pagáčová, et al. "“Spontaneous” growth of fibrous products on the surface of silicic acid gels." Journal of Sol-Gel Science and Technology 43, no. 1 (2007): 137–43. http://dx.doi.org/10.1007/s10971-007-1542-x.

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7

Potapov, Vadim V., Angel A. Cerdan, and Denis S. Gorev. "Silicic Acid Polymerization and SiO2 Nanoparticle Growth in Hydrothermal Solution." Polymers 14, no. 19 (2022): 4044. http://dx.doi.org/10.3390/polym14194044.

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The approach of numerical simulation of orthosilicic acid OSA polymerization and SiO2 nanoparticle formation in hydrothermal solution have been developed based on the model of the homogeneous stage of nucleation and the subsequent growth of particles. The influence of surface tension on the interface of SiO2–water, the rate of molecular deposition, and Zeldovich factor Z were evaluated. Temperature dependence on time, pH, initial OSA concentration, and ionic strength are the main parameters that determine the kinetics of colloid phase formation, the final average size of SiO2 nanoparticles, and the particle size distribution and its polydispersity index. The results of the numerical simulation were verified with experimental data on OSA polymerization and measurement of nanoparticles sizes using the method of dynamic light scattering in a wide range of temperatures of 20–180 °C, pH = 3–9, SiO2 content Ct of 300–1400 mg/kg, and ionic strength Is of 0.0001–0.42 mol/kg. The results obtained can be used in the technology of hydrothermal synthesis of sols, gels, and nanopowders to regulate the kinetics of OSA polymerization and SiO2 nanoparticle growth, particle size distribution, morphology, and structure of products.

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8

Gordienko, M. G., A. M. Katalevich, S. I. Ivanov, et al. "Evaluation of the Significance of the Factors Influencing the Microstructure of Silicic Acid Gels." Glass and Ceramics 72, no. 11-12 (2016): 465–68. http://dx.doi.org/10.1007/s10717-016-9812-0.

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9

Abe, Y., N. Sugimoto, Y. Nagao, and T. Misono. "Preparation of monolithic SiO2TiO2 gels by condensation polymerization of silicic acid and titanium chelates." Journal of Non-Crystalline Solids 104, no. 2-3 (1988): 164–69. http://dx.doi.org/10.1016/0022-3093(88)90384-5.

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10

Khabadze, Zurab, Sergey Ivanov, Aleksandra Kotelnikova, Mikhail Protsky, Ekaterina Shilyaeva, and Darya Nazarova. "THEEFFECT OF SILICA GEL TO THE ADHESIVE PROTOCOL STAGES IN THETREATMENT OF CARIES AND ITS COMPLICATIO." Archiv Euromedica 12, no. 2 (2022): 124–27. http://dx.doi.org/10.35630/2199-885x/2022/12/2.31.

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The etching solution is used to remove the inert surface layer of the hard tissues of the tooth, change the wetting parameters and create conditions for micromechanical adhesion. The most commonly used gel is 37% orthophosphoric acid. However, silicic acid as a thickener in the composition of etching gels, when interacting with hydroxyapatite of the tooth, gives a precipitate in the form of silicon oxide — silica. Scanning electron microscopy makes it possible to see the accumulation of round silica nanoparticles, approximately 20–40 nm in diameter. According to studies, the formation of silica particles does not affect the quality of restoration, so there is no need to remove them from the surface of demineralized dentin. The purpose of this review article is to study scientific data on the formation of an insoluble precipitate after the interaction of inorganic acid in the form of a gel with components of the inorganic enamel matrix (hydroxyapatite), and its effect on the adhesion quality of the filling material. Materials and methods: Electronic search of articles was carried out using search engines and databases Google Scholar, Pub Med. The articles are included, the content of which concerns the topic of determining the sediment formed when etching the tooth surface with orthophosphoric gel. The publication date criterion has been selected since 2011. Results: 69 articles were reviewed during the review process. After analyzing the literature according to the inclusion criteria, the total number was 20 publications. Conclusion: When etching dentin with a solution of orthophosphoric acid in the form of a gel, a precipitate of silicon oxide is formed. This is due to the presence of a thickener in the gel in the form of silicic acid. Silicic acid, or silica gel, reacts chemically with hydroxyapatite of the tooth. As a result, silica is formed, which remains on the surface of demineralized dentin in the form of round nanoparticles with a size of 20–40 nm. According to studies, the formation of silica particles does not affect the quality of restoration, so there is no need to remove them from the surface of demineralized dentin.

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11

Lysak, Nataliia, Olga Skorodumova, Anton Chernukha, Viktoria Kochubei, and Konstantinos Sotiriadis. "Study of Gelation Processes in Flame Retardant Compositions of the SiO2 Sol System – A Phosphate-Containing Additive." Defect and Diffusion Forum 438 (February 10, 2025): 101–10. https://doi.org/10.4028/p-i2syir.

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One of the promising directions for ensuring the fire resistance of wooden building materials is the development of silicon phosphate compositions, thanks to which the formation of a protective layer is possible, which effectively prevents the spread of fire. The paper examines the possibility of using orthophosphate acid as a modifying additive for silicic acid sols. The influence of H3PO4 concentration on the rheological characteristics of the studied sols was determined. Sols with small amounts of orthophosphate acid (1–2%) lost their fluidity in the interval of 45–70 minutes. Increase of the additive content to 8% led to a sharp increase in optical density values and extended the survivability interval of the sol to 24 hours. Coatings based on gels with 1–2% orthophosphate acid were elastic, but increasing the content of the additive led to the formation of hard, inelastic coatings.According to the results of infrared (IR) spectroscopy, the effect of orthophosphate acid on the nature of polycondensation was confirmed. The degree of polycondensation was estimated by the ratio of intensity (I) and band width (d) at 1050 cm–1, which corresponds to the vibrations of Si-O-Si bonds. Based on the comparison of I/d indicator values, the formation of linear siloxane chains was confirmed in the case of the use of small H3PO4 additions. Linear polycondensation ensures greater homogeneity of the gel, which was confirmed by IR spectroscopy of gels heat-treated at 800 °C and by microscopic observations. The coating on the wood surface, based on a fire-resistant silica-containing composition with small additions of orthophosphate acid, had the most uniform and continuous structure.

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12

KASGÖZ, Ahmet, Takahisa MISONO, and Yoshimoto ABE. "Preparation of SiO2-MxOy Thin Films and Gels by Sol-Gel Method Using Silicic Acid and Metal Halides." Journal of the Ceramic Society of Japan 100, no. 1161 (1992): 763–65. http://dx.doi.org/10.2109/jcersj.100.763.

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13

Bhattacharya, Sudin, and John Kieffer. "Molecular Dynamics Simulation Study of Growth Regimes during Polycondensation of Silicic Acid: from Silica Nanoparticles to Porous Gels." Journal of Physical Chemistry C 112, no. 6 (2008): 1764–71. http://dx.doi.org/10.1021/jp073808f.

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14

Avdin, V. V., I. V. Krivtsov, A. A. Lymar, and Yu V. Matveichuk. "Structure formation of the mixed gels of zirconium oxyhydrate and silicic acid produced with different sequencing of reagents." Journal of Structural Chemistry 52, no. 6 (2011): 1172–78. http://dx.doi.org/10.1134/s0022476611060242.

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15

Abe, Y., N. Sugimoto, Y. Nagao, and T. Misono. "Preparation of monolithic gels SiO2MxOy (M = Al, Zr) by the reaction of silicic acid with metal chelate compounds." Journal of Non-Crystalline Solids 108, no. 2 (1989): 150–56. http://dx.doi.org/10.1016/0022-3093(89)90577-2.

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16

Lysak, Nataliia, Olga Skorodumova, Anton Chernukha, Yana Goncharenko, and Roman Melezhyk. "Silicophosphate fireproof coatings for building materials." Problems of Emergency Situations, no. 39 (April 24, 2024): 262–71. http://dx.doi.org/10.52363/2524-0226-2024-39-19.

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The composition of silicophosphate fire-resistant coatings for wooden building structures was developed and their properties were investigated. Fireproof compositions were obtained by mixing aqueous solutions of liquid glass and acetic acid. As a phosphate-containing additive, phosphate buffer solutions were used, which were added to the silicic acid sol in different amounts and with different ratios of the components of the buffer pair. Adjusting the ratio of the components of the buffer solution led to a change in the pH of the buffer solutions, but adding them to the sol did not change its acidity, which was in the pH range of 5.5–6. The effect of the content and ratio of the components of the buffer pair on the change in the optical density of the obtained sols over time was studied. The highest durability of the flame retardant composition was recorded when using a buffer solution with a pH of 7 at a content of 20%. The embedding of phosphate ions into the siloxane framework of experimental gels has been chemically proven, which increases their fire resistance. It is shown that the amount of free phosphate anion in the intermicellar liquid of the experimental gels is less than 5%. The mechanism of the strengthening effect of the acetate buffer solution, which is formed during the mixing of the liquid glass solution with acetic acid, on the phosphate buffer solution is proposed. Fire-retardant compositions were applied to wood samples by the bath method and dried at temperatures of 80–100 ˚С in a drying cabinet. The fire protection effect of coatings was determined during fire tests in a ceramic pipe. The effect of the content of phosphate buffer solution on the fire-retardant properties of experimental coatings was studied. It is shown that increasing the content of the phosphate buffer solution reduces mass loss during fire tests, allows to increase the fire resistance of wood and transfer it to the group of "highly flammable".

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17

Wangsa, Wangsa, Remi Ayu Pratika, Tyas Sekar Ningrum, and Karna Wijaya. "Sulfuric Acid-Activated Silica Gel as a Potential Solid Acid Catalyst." Key Engineering Materials 920 (May 16, 2022): 159–65. http://dx.doi.org/10.4028/p-3y31y4.

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The conversion of silica gels into sulfated silicas (SO4/SiO2) have been carried out. The sulfation process of the catalysts was carried out by impregnation of sulfuric acids at concentrations of 1; 2; and 3 M and calcination temperatures of 500, 600, and 700 °C. Sulfation with 2 M H2SO4 and calcination temperature of 600 °C (SS2-600) produced a catalyst with the highest acidity value (5.13 mmol NH3 g-1). XRD analysis showed the formation of amorphous SiO2 phase, whereas SSA analysis showed that the SS2-600 catalyst had a mesoporous structure with a surface area of 147.728 m2/g, a total pore volume of 0.25 mL/g and a pore diameter of 6.439 nm. Characterization results show that sulfated silica gels have potency as solid acid catalysts.

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18

S., LASKAR, and SENGUPTA B. "New Spray Reagents for the Detection of Hazardous Phenols separated by Tlc." Journal of Indian Chemical Society Vol. 66, Dec 1989 (1989): 899–901. https://doi.org/10.5281/zenodo.6024222.

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Department of Chemistry, University of Burdwan, Burdwan-713 104 Manuscript received 12 May 1988, accepted 20 July 1989 The separation pattern of 22 phenols have been studied on silica gel-G tic plates using chloroform — methanol (98 : 2) as developer. The spots were detected using 4 new spray reagents, viz. orthanilic acid, o-dianisidine and their diazotised products. Most of the phenols gave easily detectable characteristic colours and the detection limit was generally 1-5 μg, and even as low as 0.1-0.5 μg in most case for the diazotised orthanilic acid.

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Mosa, J., A. Durán, and M. Aparicio. "Membranas híbridas basadas en estireno-metacrilato-sílice y ácido fosfowolfrámico obtenidas por sol-gel para pilas de combustible de intercambio protónico (PEMFC)." Boletín de la Sociedad Española de Cerámica y Vidrio 46, no. 5 (2007): 267–72. http://dx.doi.org/10.3989/cyv.2007.v46.i5.229.

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20

Yingwei, Guo, Chen Xuedan, Yan Shiting, et al. "Efficient and Reusable Silica Gel Supported Metal Ionic Liquid Catalysts for Palmitic Acid Esterification to Biodiesel." Journal of the chemical society of pakistan 43, no. 01 (2021): 1–13. http://dx.doi.org/10.52568/000001.

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A series of silica gel (SG) supported metal ionic liquid catalysts (x[Bmim]Cl-CrCl3/SG) were synthesized and exploited for the esterification of palmitic acid (PA) with methanol (ML) to produce biodiesel efficiently. The 10%[Bmim]Cl-CrCl3/SG catalyst with high surface area and desirable acidity exhibited the best catalytic performance and reusability after six consecutive running cycles. Based on the response surface analysis, the optimal reaction conditions were obtained as follows: methanol/acid mole ratio = 11:1 mol/mol, catalyst amount = 5.3 wt%, reaction time = 65 min, as well as reaction temperature = 373 K, reaching to a biodiesel yield of 96.1%. Further kinetic studies demonstrated that the esterification of PA with ML obeyed 1.41 order kinetics for acid concentration with the activation energy of 16.88 kJ/mol.

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21

Guo Yingwei, Guo Yingwei, Chen Xuedan Chen Xuedan, Yan Shiting Yan Shiting, Zhang Zhengliang Zhang Zhengliang, Chen Yuqin Chen Yuqin, and Zheng Lina Zhu Guangqi and Han Xiaoxiang Zheng Lina Zhu Guangqi and Han Xiaoxiang. "Efficient and Reusable Silica Gel Supported Metal Ionic Liquid Catalysts for Palmitic Acid Esterification to Biodiesel." Journal of the chemical society of pakistan 43, no. 1 (2021): 1. http://dx.doi.org/10.52568/000555.

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A series of silica gel (SG) supported metal ionic liquid catalysts (x[Bmim]Cl-CrCl3/SG) were synthesized and exploited for the esterification of palmitic acid (PA) with methanol (ML) to produce biodiesel efficiently. The 10%[Bmim]Cl-CrCl3/SG catalyst with high surface area and desirable acidity exhibited the best catalytic performance and reusability after six consecutive running cycles. Based on the response surface analysis, the optimal reaction conditions were obtained as follows: methanol/acid mole ratio = 11:1 mol/mol, catalyst amount = 5.3 wt%, reaction time = 65 min, as well as reaction temperature = 373 K, reaching to a biodiesel yield of 96.1%. Further kinetic studies demonstrated that the esterification of PA with ML obeyed 1.41 order kinetics for acid concentration with the activation energy of 16.88 kJ/mol

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Guo Yingwei, Guo Yingwei, Chen Xuedan Chen Xuedan, Yan Shiting Yan Shiting, Zhang Zhengliang Zhang Zhengliang, Chen Yuqin Chen Yuqin, and Zheng Lina Zhu Guangqi and Han Xiaoxiang Zheng Lina Zhu Guangqi and Han Xiaoxiang. "Efficient and Reusable Silica Gel Supported Metal Ionic Liquid Catalysts for Palmitic Acid Esterification to Biodiesel." Journal of the chemical society of pakistan 43, no. 1 (2021): 1. http://dx.doi.org/10.52568/000555/jcsp/43.01.2021.

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A series of silica gel (SG) supported metal ionic liquid catalysts (x[Bmim]Cl-CrCl3/SG) were synthesized and exploited for the esterification of palmitic acid (PA) with methanol (ML) to produce biodiesel efficiently. The 10%[Bmim]Cl-CrCl3/SG catalyst with high surface area and desirable acidity exhibited the best catalytic performance and reusability after six consecutive running cycles. Based on the response surface analysis, the optimal reaction conditions were obtained as follows: methanol/acid mole ratio = 11:1 mol/mol, catalyst amount = 5.3 wt%, reaction time = 65 min, as well as reaction temperature = 373 K, reaching to a biodiesel yield of 96.1%. Further kinetic studies demonstrated that the esterification of PA with ML obeyed 1.41 order kinetics for acid concentration with the activation energy of 16.88 kJ/mol

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23

Guo Yingwei, Guo Yingwei, Chen Xuedan Chen Xuedan, Yan Shiting Yan Shiting, Zhang Zhengliang Zhang Zhengliang, Chen Yuqin Chen Yuqin, and Zheng Lina Zhu Guangqi and Han Xiaoxiang Zheng Lina Zhu Guangqi and Han Xiaoxiang. "Efficient and Reusable Silica Gel Supported Metal Ionic Liquid Catalysts for Palmitic Acid Esterification to Biodiesel." Journal of the chemical society of pakistan 43, no. 1 (2021): 1. http://dx.doi.org/10.52568/000014.

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A series of silica gel (SG) supported metal ionic liquid catalysts (x[Bmim]Cl-CrCl3/SG) were synthesized and exploited for the esterification of palmitic acid (PA) with methanol (ML) to produce biodiesel efficiently. The 10%[Bmim]Cl-CrCl3/SG catalyst with high surface area and desirable acidity exhibited the best catalytic performance and reusability after six consecutive running cycles. Based on the response surface analysis, the optimal reaction conditions were obtained as follows: methanol/acid mole ratio = 11:1 mol/mol, catalyst amount = 5.3 wt%, reaction time = 65 min, as well as reaction temperature = 373 K, reaching to a biodiesel yield of 96.1%. Further kinetic studies demonstrated that the esterification of PA with ML obeyed 1.41 order kinetics for acid concentration with the activation energy of 16.88 kJ/mol

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Ludeña, Huaman Michael Azael Ludeña. "Proceso Sol-Gel en la Síntesis de Dióxido de Silicio (SiO2)." Bases de la Ciencia 6, no. 2 (2021): 1–12. https://doi.org/10.5281/zenodo.7013132.

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RESUMEN En ciencia de los materiales el dióxido de silicio, también conocido como sílice, ha recibido significante atención en diferentes áreas de investigación, ganando un espacio importante y de mucho interés entre los investigadores, debido a sus diversas aplicaciones que abarcan desde la síntesis de soportes para catalizadores hasta materiales para la liberación controlada de fármacos. Es motivo por el cual, en este manuscrito se dan a conocer aspectos químicos fundamentales e importantes sobre el proceso sol-gel en la síntesis de la sílice a partir de moléculas precursoras de alcóxidos de silicio y organosilanos. Se analiza cómo el catalizador ácido/básico y el tipo de precursor afectan a las reacciones de hidrólisis y condensación, así como a la estructura y morfología del material.   Abstract In materials science, silicon dioxide has received significant attention in different research areas, gaining valuable space and interest between researchers due to its diverse applications, ranging from the synthesis of supports for catalysts to materials for controlled drug liberation. Herein we describe fundamental and important chemical aspects of the sol-gel process in the synthesis of silica, starting from precursor molecules of silicon alkoxides and organosilanes. Moreover, this review analyses how the acid/basic catalyst and the type of precursor affect the hydrolysis and condensation reaction, as well as the structure and morphology of the obtained material.

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A., Mueller, Sailer M., and Regidor P.A. "Treatment with an intravaginal gel containing siliceous dioxide, selenite, and citric acid to promote regression of ASC-US, LSIL, ASC-H, HSIL, p16/Ki67 status and improve clearance of hr-HPV in cervical specimens." Reproductive Health of Woman 4 (May 31, 2021): 48–57. https://doi.org/10.30841/2708-8731.4.2021.238162.

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Objective: An intravaginal gel containing highly dispersed silicon dioxide (SiO2) and an anti-oxidative combination of citric acid and sodium selenite was tested for its ability to promote regression of abnormal cytological findings and its influence on hr-HPV status and tumor markers p16/Ki67 (CINtec® PLUS test). Patients and methods: A control study was performed, including women (n=100) diagnosed with conspicuous cervical smears (ASC-US, LSIL, ASC-H, or HSIL). The gel was applied for 3x28 days. After three months, participants were analyzed for Pap status, hr-HPV strains, and expression of tumor markers p16/Ki67. Three months later, Pap testing and p16/Ki67 analysis were repeated. The results were compared to those of 106 women who met the same inclusion criteria but did not obtain any treatment. Results: After six months, cytological Pap findings were improved in 80.9% of the participants in the treated group, and the clearing of hr-HPV was observed in 53% of cases. Only 5.3% were tested p16/Ki67 positive after six months in comparison to 75.0% at baseline. In the comparison group, 37.1% of the Pap smears and 18.6% of the CinTec results were improved, but no hr-HPV clearance was observed. The improvements were highly significant for the treatment. Conclutions: The vaginal gel containing SiO2 sodium selenite, and citric acid may support the healing of conspicuous cytological findings and clearance of hr-HPV.

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Sharma, Himanshu, S. C. Sharma, Taruna Manchanda, and Seema Singh. "Mobility Behaviour of Amino Acids on Silica Gel-G, Starch and Titanium Tungstate Layers Using Mixed Mobile Phases Containing DMSO." Chitkara Chemistry Review 1, no. 1 (2013): 45–51. http://dx.doi.org/10.15415/ccr.2013.11003.

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27

PARTHA, S. MAJUMDAR, and S. RAY UDAY. "Extraction Chromatography of lndium(III) on Silica Gel impregnated with High Molecular Weight Carboxylic Acid and its Analytical Applications." Journal of Indian Chemical Society Vol. 68, Mar 1991 (1991): 152–53. https://doi.org/10.5281/zenodo.5990394.

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Department of Chemistry, Visva·Bbarati, Santiniketan-731 235 Manuscript received 17 September 1990, revised 26 February 1991, accepted 20 March 1991 lndium(III) was separated by extraction chromatography with Versatic 10 as a stationary phase on a column of silica gel fr,m acetic acid and sodium acetate solution (pH 4.5-6.0), The optimum condition for extraction was studied based on the critical study of the relevant factors as effects or pH, Bow rate on extraction and elution Role or stripping agents on the elution was studied. The separation or indium from a number or elements was carried out lndium(III) was separated from AIIII, GallI, TIIII, ZrIV and trivalent lanthanides which Interfere under the recommended extraction condition by exploiting the differences in their stripping behaviour.

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Lakshmichhaya, Ramkrishna Patil, Madhukar Patil Arun, and Jayantrao Shitole Sharda. "Electro-optical and thermal characterization of copper tartrate crystals grown in silica gel." World Journal of Advanced Research and Reviews 24, no. 1 (2024): 2386–94. https://doi.org/10.5281/zenodo.15062788.

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Copper Tartrate crystals were grown by Gel Growth technique by single diffusion. Silica gel of Optimum specific gravity was set with tartaric acid at optimum pH and aging period. Band gap of copper tartrate crystal is determined using UV-Visible spectroscopy to be 5.24 eV. In PL spectra broad peak is observed at nearly 367.44186 nm in the range 287 nm to 458 nm along with the sharp, intense transmission maxima peak at wavelength nearly 505.03876 nm which is characteristic of a material composition and electronic band structure. This shows the transparency in UV-visible region and material is a filter in this range .TGA analysis concluded that Copper tartrate has one half water molecule as crystalline water and is stable up to 85.02 0 C.DSC analysis assigns the temperature value 314.5 0C as melting point and apparent enthalpy of fusion determined is 10.18 mW.

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Pranesh, Chowdhury, K. Pandit Susanta, and Mandal Bhabatosh. "Solid phase extraction of Hgll ions with cross-linked poly(acrylic acid), coated on silanized silica gel." Journal of Indian Chemical Society Vol. 86, Apr 2009 (2009): 377–82. https://doi.org/10.5281/zenodo.5809971.

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Analytical Laboratory, Department of Chemistry, Visva-Bharati, Santiniketan-731 235, West Bengal, India E-mail : pranesh_02@yahoo.co.in Manuscript received 15 December 2008, accepted 24 December 2008 A selective and reliable method has been developed for the extraction and separation of HgII with high molecular mass cross-linked poly(acrylic acid) coated on silanized silica gel. The coated material acts as stationary phase for the extraction. Ion exchange and break-through capacity of the exchanger have been measured. The optimum pH range for the quantitative extraction of HgII was found to be 5.0-6.0. The elution behaviors of HgII have been investigated. A plausible mechanism for HgII extraction and elution has been suggested. HgII has been isolated quantitatively from various synthetic mixtures containing heavy metal ions (Pb2+, Cd2+, zn2+, Co2+, Ni2+ and cu2+).

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Bhabatosh, Mandai, Chowdhury Pranesh, and K. Pandit Susanta. "Extraction chromatographic studies of uranium(VI) with crosslinked poly(acrylic acid) coated on silica gel." Journal of Indian Chemical Society Vol. 85, Sep 2008 (2008): 930–35. https://doi.org/10.5281/zenodo.5820255.

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Analytical Laboratory, Department of Chemistry, Visva-Bharati, Santiniketan-731 235, West Bengal, India E-mail: bhabatosh_mandal@yahoo.co.in Manuscript received 16 October 2007, revised 12 May 2008, accepted 25 June 2008 A selective method has been developed for extraction and separation of UVI with the chemically synthesized high molecular mass crosslinked poly(acrylic acid) coated on silanized silica gel. The coated materials act as a stationary phase for the extraction chromatographic studies. The structure and thermal stability of crosslinked poly(acrylic acid) has been elucidated with the help of FTIR and TGA. The optimum pH range for quantitative extraction of uranium was found to be 4 to 6. The effects of pH and stripping agent on extraction and elution of UVI have been investigated. Ion exchange and break-through capacity of the exchanger (polymer coated on silanized silica gel) have been determined at room temperature. Surface morphology of the exchanger was studied by SEM. UVI has been separated quantitatively from various synthetic aqueous mixtures containing metal ions (VIV, ThIV, CeIV, PbII , HgII , InIII, FeIII and ZrIV) commonly pre..,ent in uranium ores and fission products. The method permits pre-concentration and sequential separation of UVI from CeVI, ThIV and ZrIV of the same analytical group. A plausible mechanism for uranium ion exchange has been suggested.

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Hakan, Duran, Sismanoglu Sedef, and Sismanoglu Tuba. "Binary biomaterials (inorganic material/natural resin): Synthesis, characterization and performance for adsorption of dyes." Journal of Indian Chemical Society Vol. 96, Sep 2019 (2019): 1245–51. https://doi.org/10.5281/zenodo.5643572.

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Department of Chemistry, Faculty of Engineering, Istanbul University-Cerrahpa S, a, Avc lar, Istanbul, Turkey Engineering Faculty, Metallurgical and Materials Engineering, Karabuk University, Karabuk, Turkey E-mail: sedefsismanoglu@karabuk.edu.tr Manuscript received online 26 April 2019, revised and accepted 20 July 2019 The sol-gel method has been reported a useful techniques for synthesizing inorganic material HSS. In this study, the sol-gel process was used in two stages. In the first step, the hydrolysis of phenyltrimethoxysilane (PTMS) was carried out under acidic conditions. In the second step, the silane condensation proceeded under basic conditions and as a result the HSS were obtained. The obtaining HSS was treated with epichlorohydrin to carry out an epoxidation process (HSEPC). Then, HSEPC was functionalized by treatment with natural resin (gum arabic) and obtained HSEPCGUM. Gum arabic has GA-GP-GA-glycoprotein, hydroxyproline glucuronic acid and polysaccharides groups. Anionic and cationic dyes were adsorbed onto HSEPCGUM and values of absorbance was measurement by UV-Visible spectrophotometers. Adsorption isotherm experiments of adsorbed dyes on HSEPCGUM were performed at 35ºC with Freundlich, Langmuir and Dubinin-Radushkevich (DR) methods. Adsorption maximum capacity of HSEPCGUM (Xmax) was obtained 100 mg/g for BB3. Before and after dye adsorption the structure characterization of adsorbent was done by SEM and FTIR analysis.

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Ichikawa, Takaaki, Takuya Takahashi, Yuki Hiramitsu, et al. "3A1358 Light induced ion conductive change in gel films which contain amino acids joined on a hydrogenated amorphous silicon film(3A Biol & Artifi memb 4: Transport, Signal transduction,The 49th Annual Meeting of the Biophysical Society of Japan)." Seibutsu Butsuri 51, supplement (2011): S106. http://dx.doi.org/10.2142/biophys.51.s106_5.

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P., L. Majumder, Bandyopadhyay (nee Guha) Saswati, and Pal (nee Ray) Suparna. "Rigidanthrin, a new dimeric phenanthrene derivative of the orchid Bulbophyllum rigidum." Journal of Indian Chemical Society Vol. 85, Nov 2008 (2008): 1116–23. https://doi.org/10.5281/zenodo.5820345.

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Department of Chemistry, University College of Science, 92, Acharya Prafulla Chandra Road, Kolkata-700 009, India E-mail : priyalalm@hotmail.com Manuscript received 15 September 2008, accepted 30 September 2008 Rigidanthrin, a new dimeric phenanthrene derivative, was isolated from the orchid Bulbophyllum rigidum which also afforded the known monomeric phenanthrenes nudol and gymnopusin and the simple aromatic compound ethyl 4-hydroxy-3-methoxycinnamate. The structure of rigidanthrin was established as 2,2', 7, 7'-tetrahydroxy-3,3' ,4,4'tetramethoxy- 1,1' -biphenanthryl from various spectral and chemical evidence. The structure of rigidanthrin was finally confirmed by regio- as well as regio- and enantio-selective biomimetic synthesis from its monomeric congener nudol (2, 7-dihydroxy-3,4-dimethoxyphenanthrene) by oxidative phenol-coupling reaction with phosphomolybdic acid (PMA) on silica gel surface and CuCI(OH).(-)-(S)-proline methyl ester, respectively, in very good yields. The optical purity of (-)-rigidanthrin obtained in the latter case was found to be 95.79%. The co-occurrence of rigidanthrin with its monomer nudol in the same orchid Bulbophyllum rigidum provides a strong circumstantial evidence in support of the proposed biogenesis of the naturally occurring biphenanthryl derivatives which are assumed to have been formed from their corresponding monomers by enzymatic oxidative phenol-coupling reaction.

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Poluianova, Aleksandra, Alexandra Robciuc, Jukka Moilanen, et al. "Tolerability of silica microparticle gels as drug delivery vehicles." Acta Ophthalmologica 102, S279 (2024). http://dx.doi.org/10.1111/aos.15858.

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Aims/Purpose: Over the past decades, polymeric particles have become widespread in the field of drug delivery. Silica microparticles (SiMPs) are biodegradable—silicic acid being the main degradation product—and can release medication sustainably for a long period of time. Our aim was to determine the effects of soluble silicic acid on in vitro models of human epithelial cells.Methods: HCE‐2 and ARPE‐19 cells were exposed to serial dilutions of silicic acid produced by dissolving silica hydrogel in PBS, and cell viability was assessed after 24, 48 and 72 h of incubation. Cell viability data were provided by AlamarBlue assay, while membrane integrity was analysed through LDH release. For more information on the silicic acid impact on cellular stress, we assayed biochemical markers, such as IL‐6, IL‐8, MCP‐1, Caspase‐3 and Hsp‐70, using specific ELISAs.Results: AlamarBlue assay did not show any statistical differences in survival rate between the control group and maximum 30 μg/mL silicic acid in all timepoints in ARPE‐19 cells (24 h 95.42 ± 4.81%, 48 h 87.55 ± 6.48% and 72 h 97.64 ± 6.38%) and HCE‐2 cells (24 h 97.38 ± 5.97%, 48 h 100.81 ± 8.32% and 72 h 101.73 ± 2.62%). Additionally, we did not detect any toxic changes in LDH release test in ARPE‐19 cells in 24, 48 and 72 h time points (30 μg/mL silicic acid: 24 h 9.0 ± 11.5%, 48 h 10.4 ± 13.4% and 72 h 13.8 ± 16.6%). The LDH release data in treated (max. 30 μg/mL) HCE‐2 cells were comparable to control cells. Assessed inflammatory markers mostly were similar as well when comparing control and treatment groups, although IL‐6, MCP‐1, Caspase‐3 and Hsp‐70 showed increased values with time.Conclusions: Our results do not show major cytotoxicity of silicic acid on the two different epithelial cell lines, nor did not induce stress or inflammatory markers. Therefore, these findings support the use of our novel SiMPs as drug delivery vehicles in the treatment of ophthalmic diseases.

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Rabinovich, E. M., and D. L. Wood. "Fluorine In Silica Gels." MRS Proceedings 73 (1986). http://dx.doi.org/10.1557/proc-73-251.

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ABSTRACTFluorine has a remarkable and diverse action in silica sols, gels and gel-derived glasses. Introduced in ionic form, it causes more rapid gelation, it reduces surface area and water adsorption of dry gels, and it helps to eliminate bubble formation during sintering and reheating of gel-derived glasses. The mechanisms for these actions of the fluoride ion are reviewed, with a more detailed discussion of the rate of gelation. Several previously held views of the way fluoride accelerates gel formation are compared with a new suggestion that it is caused by an electrostatic attraction between the proton of the OH of silicic acid and F− present as Si-F groups.

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de, la Torre Cristina, Carmen Coll, Amelia Ultimo, Félix Sancenón, Ramón Martínez-Máñez, and Eduardo Ruiz-Hernández. "In Situ-Forming Gels Loaded with Stimuli-Responsive Gated Mesoporous Silica Nanoparticles for Local Sustained Drug Delivery." Pharmaceutics 15, no. 4 (2023). https://doi.org/10.3390/pharmaceutics15041071.

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A novel combination of in situ-forming hydrogels of hyaluronic acid with gated mesoporous materials was developed to design depots for local sustained release of chemotherapeutics. The depot consists of a hyaluronic-based gel loaded with redox-responsive mesoporous silica nanoparticles loaded with safranin O or doxorubicin and capped with polyethylene glycol chains containing a disulfide bond. The nanoparticles are able to deliver the payload in the presence of the reducing agent, glutathione (GSH), that promotes the cleavage of the disulfide bonds and the consequent pore opening and cargo delivery. Release studies and cellular assays demonstrated that the depot can successfully liberate the nanoparticles to the media and, subsequently, that the nanoparticles are internalized into the cells where the high concentration of GSH induces cargo delivery. When the nanoparticles were loaded with doxorubicin, a significant reduction in cell viability was observed. Our research opens the way to the development of new depots that enhance the local controlled release of chemotherapeutics by combining the tunable properties of hyaluronic gels with a wide range of gated materials.

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Faizullaev, N.I. Rakhmatov Kh.B. Rakhmonkulov M.T. Safarov M.Dj. Matmuratov Sh.S. "CATALYTIC SYNTHESIS OF DIMETHYLPHYR FROM CARBON MONOXIDE." October 2, 2024. https://doi.org/10.5281/zenodo.13878915.

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Currently, it is relevant to obtain dimethyl ether from synthesis gas in one step. In the work, the influence of various factors on the process of direct synthesis of dimethyl ether from syngas in one step was studied in Cu2O*ZnO*ZrO2/YuKTs catalyst. As a result of studies conducted on the effect of various factors on the production of target products in the process of obtaining dimethyl ether from synthesis gas, it was found that increasing the ratio of moles of pressure, temperature, and the mole ratio of hydrogen to greenhouse gas leads to an increase in greenhouse gas conversion due to the fact that the direct synthesis reaction of dimethyl ether from synthesis gas prevails. An increase in the volume velocity reduces the conversion of the carbon monoxide, because the reaction between the reactants in the gas phase and the methanol catalyst surface does not have time to occur due to the low contact time. It has been proven that the increase in the ratio of gas to hydrogen moles leads to an increase in the yield of dimethyl ether and the conversion of gas. As a result of the research, the following optimal conditions for obtaining dimethyl ether from carbon dioxide and hydrogen in one step were determined: R=1 MPa, T=300℃, hydrogen:carbon gas=2, volume velocity 1000 hour-1. In this case, the conversion of exhaust gas does not decrease for 220 hours. At the same time, the physico-chemical and textural characteristics of the Cu2O*ZnO*ZrO2/ЮКЦ catalyst were studied. The acidity of the Cu2O*ZnO*ZrO2/ЮКЦ catalyst surface was determined by the method of thermoprogrammed desorption of ammonia. Acidity value for Cu2O*ZnO*ZrO2/ЮКЦ was 0.065 mmol NH3/gkat. The calculated value of acidity of YuKTs was 0.26 mmol NH3/gkat. When Lewis acid centers (Lewis acidity center) were determined in the presence of Cu2O*ZnO*ZrO2/ЮКЦ primary catalyst by IR-spectroscopy method, it was found that the concentration of Lewis acidity center was 49 μmol/g. The amount of Brønsted acidity centers is 56 μmol/g of the total concentration of acidity centers. The purpose of the work is to study the kinetic laws of the synthesis reaction of dimethyl ether from synthesis gas in one step and the textural characteristics of the catalyst.

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Gronow, Michael. "ANALYSIS OF LOW MOLECULAR WEIGHT THIOLS PRESENT IN A HUMAN PROSTATE CANCER CELL LINE (LNCAP) USING 4-DIMETHYLAMINOAZOBENZENE-4'-MALEIMIDE (DABMA) AS A LABELLING AGENT: APPARENT GLUTATHIONE CONTENT." International Journal of Sciences Volume 1, no. 2012-11 (2012). https://doi.org/10.5281/zenodo.3348100.

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Low molecular weight thiols play important roles in cell homeostasis, drug metabolism, cancer formation and progression. The major component in this fraction is commonly assumed to be the tripeptide glutathione but there have been reports of the presence of other unknown thiols in tumour cells. To investigate this further the composition of the non protein sulphydryl components of the acid soluble fraction (ASF) of LNCap cells (a lymph node human prostate cancer) have been investigated after labelling with 4-dimethylaminoazobenzene-4'-maleimide (DABMA) at pH 5.5.A preliminary isolation of the adducts formed was achieved using reverse phase chromatography on C-18 silica gel (ODS-AQ) giving three crude fractions. The first fraction contained the glutathione adduct and this could be separated from the other thiol adducts by flash chromatography on silica gel followed by ion exchange chromatography on a cellulose anion exchanger.The molar extinction coefficient of the glutathione derivative at the λ max of 455nm (pH5.5) was estimated by amino acid analysis to be 26,600 M-1 cm-1 (DABMA in methanol 32,000 M-1 cm-1). Using this value it was calculated that, in the total ASF, not more than 40% of the total measured thiol could be attributed to glutathione.Other thiol adducts were shown to be present in variable amounts; separation and analysis proved difficult but using HPLC and TLC techniques a number of unknown components were shown to be present. Amino acid analysis revealed that they did not contain cysteine or peptide material and UV/visible spectra ruled out the presence of nucleic acid derivatives. MS and NMR analyses indicated that unknown water soluble thiols are present which are probably lipid in nature. Further analysis of one isolated adduct indicated the presence of 5-mercapto-pentanol.Read Complete Article at ijSciences: V120121077

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Mohammad, Ali Nasiri, yosufi Azizullah, Ali Moin Bonyad, Rashid Abdulraouf, and yosif Joyan Mohammad. "Synthesis of oxindole Substituted imidazothiadiazole." May 28, 2022. https://doi.org/10.5281/zenodo.6666150.

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In this experiment a mixture of 4-Chlorophenyl acetic acid (1 eq) and thiosemicarbazide (1.5 eq) was added slowly to the round bottom flask containing concentrated H2SO4 with constant stirring in ice bath. After complete addition, ice bath was replaced by water bath and slowly heated to 70-80 ⁰C and maintained at that temperature for 7 hrs. After cooling to room temperature, the contents of the reaction were poured into ice water and made basic with ammonia and the precipitate was filtered, washed with water and recrystallized from ethanol. All work relating to analytical thin layer chromatography were performed with silica gel 60F254 aluminum plates and were visualized with UV light. Melting points were recorded on a Thomas Hoover capillary melting point apparatus and are uncorrected.  The following mobile phases were employed for TLC : hexane and ethyl acetate in different ratios. The instrumental techniques employed for the characterization of the newly synthesized compounds include 1H and 13C NMR spectroscopy. 1H and 13C NMR spectra were recorded on a (400 and 300 MHz)

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Journal articles on the topic 'Silicic Acid Gels'

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