Sol-gel processing with inorganic metal salt precursors

DOEpatents

Hu, Zhong-Cheng

2004-10-19

Methods for sol-gel processing that generally involve mixing together an inorganic metal salt, water, and a water miscible alcohol or other organic solvent, at room temperature with a macromolecular dispersant material, such as hydroxypropyl cellulose (HPC) added. The resulting homogenous solution is incubated at a desired temperature and time to result in a desired product. The methods enable production of high quality sols and gels at lower temperatures than standard methods. The methods enable production of nanosize sols from inorganic metal salts. The methods offer sol-gel processing from inorganic metal salts.

Tantala-based sol-gel coating for capillary microextraction on-line coupled to high-performance liquid chromatography.

PubMed

Tran, MinhPhuong; Turner, Erica B; Segro, Scott S; Fang, Li; Seyyal, Emre; Malik, Abdul

2017-11-03

A sol-gel organic-inorganic hybrid sorbent, consisting of chemically integrated tantalum (V) ethoxide (TaEO) and polypropylene glycol methacrylate (PPGM), was developed for capillary microextraction (CME). The sol-gel sorbent was synthesized within a fused silica capillary through hydrolytic polycondensation of TaEO and chemical incorporation of PPGM into the evolving sol-gel tantala network. A part of the organic-inorganic hybrid sol-gel network evolving in the vicinity of the capillary walls had favorable conditions to get chemically bonded to the silanol groups on the capillary surface forming a surface-bonded coating. The newly developed sol-gel sorbent was employed to isolate and enrich a variety of analytes from aqueous samples for on-line analysis by high-performance liquid chromatography (HPLC) equipped with a UV detector. CME was performed on aqueous samples containing trace concentrations of analytes representing polycyclic aromatic hydrocarbons, ketones, alcohols, amines, nucleosides, and nucleotides. This sol-gel hybrid coating provided efficient extraction with CME-HPLC detection limits ranging from 4.41pM to 28.19 pM. Due to direct chemical bonding between the sol-gel sorbent coating and the fused silica capillary inner surface, this sol-gel sorbent exhibited enhanced solvent stability. The sol-gel tantala-based sorbent also exhibited excellent pH stability over a wide pH range (pH 0-pH 14). Furthermore, it displayed great performance reproducibility in CME-HPLC providing run-to-run HPLC peak area relative standard deviation (RSD) values between 0.23% and 3.83%. The capillary-to-capillary RSD (n=3), characterizing capillary preparation method reproducibility, ranged from 0.24% to 4.11%. The results show great performance consistency and application potential for the sol-gel tantala-PPGM sorbent in various fields including biomedical, pharmaceutical, and environmental areas. Copyright © 2017 Elsevier B.V. All rights reserved.

Sol-gel processed porous silica carriers for the controlled release of diclofenac diethylamine.

PubMed

Czarnobaj, Katarzyna; Czarnobaj, Joanna

2008-10-01

Silica xerogels doped with diclofenac diethylamine were prepared by the sol-gel method from a hydrolysed tetraethoxysilane (TEOS) solution containing diclofenac diethylamine. Two different catalysts, drying conditions and levels of water content were used to alter the microstructure of the silica xerogels. The aim of this study was to determine the rate of Diclofenac release from the silica xerogels. This in vitro study showed that the sol-gel method is useful for entrapping Diclofenac in the pores of xerogels. It also showed that, in vitro, Diclofenac is released from the silica xerogel, through the pores, by diffusion. Base-catalysed gels proved to be much more effective than acid-catalyzed gels. (c) 2008 Wiley Periodicals, Inc.

Infiltration of methylammonium metal halide in highly porous membranes using sol-gel-derived coating method

NASA Astrophysics Data System (ADS)

Kwon, Seung Lee; Jin, Young Un; Kim, Byeong Jo; Han, Man Hyung; Han, Gill Sang; Shin, Seunghak; Lee, Sangwook; Jung, Hyun Suk

2017-09-01

Organic-inorganic halide perovskites (OIHPs) has emerged as promising optoelectronic materials for solar cells and light-emitting diodes. OIHPs are usually coated on a flat surface or mesoporous scaffold for the applications. Herein, we report a facile sol-gel-derived solution route for coating methylammonium lead iodide (MAPbI3) perovskite layers onto various nanoporous structures. We found that lead-acetate solution has superior infiltration property onto surface of oxide membranes, and it can easily be converted to MAPbI3 by sequential transform to PbO, PbI2, and finally MAPbI3. Excellent pore-filling and full coverage of the nanostructures with the final MAPbI3 perovskite material are demonstrated via this sol-gel-derived solution route, using mesoporous TiO2, TiO2 nanorods, and high-aspect ratio nanopores in anodic aluminum oxide membranes. Given that this sol-gel-based method fills nanopores better than other conventional coating methods for OIHPs, this method may find wide applications in nanostructured OIHPs-based optoelectronic systems.

Graphene oxide based sol-gel stainless steel fiber for the headspace solid-phase microextraction of organophosphate ester flame retardants in water samples.

PubMed

Jin, Tingting; Cheng, Jing; Cai, Cuicui; Cheng, Min; Wu, Shiju; Zhou, Hongbin

2016-07-29

In this paper, graphene oxide was coated onto a stainless steel wire through sol-gel technique and it was used as a solid phase microextraction (SPME) fiber. The prepared fiber was characterized by scanning electron microscopy (SEM), which displayed that the fiber had crinkled surface and porous structure The application of the fiber was evaluated through the headspace SPME of nine organophosphate ester flame retardants (OPFRs) with different characteristics in water samples followed by gas chromatography and nitrogen-phosphorous detector (GC/NPD). The major factors influencing the extraction efficiency, including the extraction and desorption conditions, were studied and optimized. Under the optimum conditions, the proposed method was evaluated, and applied to the analysis of organophosphate ester flame retardants in real environmental water samples. The results demonstrated the HS-SPME method based on GO sol-gel fiber had good linearity (R>0.9928), and limits of detection (1.4-135.6ngL(-1)), high repeatability (RSD<9.8%) and good recovery (76.4-112.4%). The GO based sol-gel fiber displayed bigger extraction capability than the commercial PDMS fiber and the pure sol-gel fiber for both polar and apolar organophosphate esters, especially for the OPFRs containing benzene rings. Copyright © 2016 Elsevier B.V. All rights reserved.

A novel tantalum-based sol-gel packed microextraction syringe for highly specific enrichment of phosphopeptides in MALDI-MS applications.

PubMed

Çelikbıçak, Ömür; Atakay, Mehmet; Güler, Ülkü; Salih, Bekir

2013-08-07

A new tantalum-based sol-gel material was synthesized using a unique sol-gel synthesis pathway by PEG incorporation into the sol-gel structure without performing a calcination step. This improved its chemical and physical properties for the high capacity and selective enrichment of phosphopeptides from protein digests in complex biological media. The specificity of the tantalum-based sol-gel material for phosphopeptides was evaluated and compared with tantalum(V) oxide (Ta2O5) in different phosphopeptide enrichment applications. The tantalum-based sol-gel and tantalum(V) oxide were characterized in detail using FT-IR spectroscopy, X-ray diffraction (XRD) and scanning electron microscopy (SEM), and also using a surface area and pore size analyzer. In the characterization studies, the surface morphology, pore volume, crystallinity of the materials and PEG incorporation into the sol-gel structure to produce a more hydrophilic material were successfully demonstrated. The X-ray diffractograms of the two different materials were compared and it was noted that the broad signals of the tantalum-based sol-gel clearly represented the amorphous structure of the sol-gel material, which was more likely to create enough surface area and to provide more accessible tantalum atoms for phosphopeptides to be easily adsorbed when compared with the neat and more crystalline structure of Ta2O5. Therefore, the phosphopeptide enrichment performance of the tantalum-based sol-gels was found to be remarkably higher than the more crystalline Ta2O5 in our studies. Phosphopeptides at femtomole levels could be selectively enriched using the tantalum-based sol-gel and detected with a higher signal-to-noise ratio by matrix-assisted laser desorption/ionization-mass spectrometer (MALDI-MS). Moreover, phosphopeptides in a tryptic digest of non-fat bovine milk as a complex real-world biological sample were retained with higher yield using a tantalum-based sol-gel. Additionally, the sol-gel material was packed into a standard syringe (0.5 mL) to enhance the ease of use of the sol-gel material and for the elimination of additional mixing and separation procedures during the adsorption, washing and elution steps of the enrichment procedure. It was found that up to 28 phosphopeptides in milk digest were easily detectable by MALDI-MS at femtomole levels (around 20 fmol) using the microextraction syringe within less than one minute.

Catalytic activity of acid and base with different concentration on sol-gel kinetics of silica by ultrasonic method.

PubMed

Das, R K; Das, M

2015-09-01

The effects of both acid (acetic acid) and base (ammonia) catalysts in varying on the sol-gel synthesis of SiO2 nanoparticles using tetra ethyl ortho silicate (TEOS) as a precursor was determined by ultrasonic method. The ultrasonic velocity was received by pulsar receiver. The ultrasonic velocity in the sol and the parameter ΔT (time difference between the original pulse and first back wall echo of the sol) was varied with time of gelation. The graphs of ln[ln1/ΔT] vs ln(t), indicate two region - nonlinear region and a linear region. The time corresponds to the point at which the non-linear region change to linear region is considered as gel time for the respective solutions. Gelation time is found to be dependent on the concentration and types of catalyst and is found from the graphs based on Avrami equation. The rate of condensation is found to be faster for base catalyst. The gelation process was also characterized by viscosity measurement. Normal sol-gel process was also carried out along with the ultrasonic one to compare the effectiveness of ultrasonic. The silica gel was calcined and the powdered sample was characterized with scanning electron microscopy, energy dispersive spectra, X-ray diffractogram, and FTIR spectroscopy. Copyright © 2014 Elsevier B.V. All rights reserved.

Determination of Insulator-to-Semiconductor Transition in Sol-Gel Oxide Semiconductors Using Derivative Spectroscopy.

PubMed

Lee, Woobin; Choi, Seungbeom; Kim, Kyung Tae; Kang, Jingu; Park, Sung Kyu; Kim, Yong-Hoon

2015-12-23

We report a derivative spectroscopic method for determining insulator-to-semiconductor transition during sol-gel metal-oxide semiconductor formation. When an as-spun sol-gel precursor film is photochemically activated and changes to semiconducting state, the light absorption characteristics of the metal-oxide film is considerable changed particularly in the ultraviolet region. As a result, a peak is generated in the first-order derivatives of light absorption ( A' ) vs. wavelength (λ) plots, and by tracing the peak center shift and peak intensity, transition from insulating-to-semiconducting state of the film can be monitored. The peak generation and peak center shift are described based on photon-energy-dependent absorption coefficient of metal-oxide films. We discuss detailed analysis method for metal-oxide semiconductor films and its application in thin-film transistor fabrication. We believe this derivative spectroscopy based determination can be beneficial for a non-destructive and a rapid monitoring of the insulator-to-semiconductor transition in sol-gel oxide semiconductor formation.

Resistance of dichromated gelatin as photoresist

NASA Astrophysics Data System (ADS)

Lin, Pang; Yan, Yingbai; Jin, Guofan; Wu, Minxian

1999-09-01

Based on the photographic chemistry, chemically hardening method was selected to enhance the anti-etch capability of gelatin. With the consideration of hardener and permeating processing, formaldehyde is the most ideal option due to the smallest molecule size and covalent cross-link with gelatin. After hardened in formaldehyde, the resistance of the gelatin was obtained by etched in 1% HF solution. The result showed that anti-etch capability of the gelatin layer increased with tanning time, but the increasing rate reduced gradually and tended to saturation. Based on the experimental results, dissolving-flaking hypothesis for chemically hardening gelatin was presented. Sol-gel coatings were etched with 1% HF solution. Compared with the etching rate of gelatin layer, it showed that gelatin could be used as resist to fabricate optical elements in sol-gel coating. With the cleaving-etch method and hardening of dichromated gelatin (DCG), DCG was used as a photoresist for fabricating sol-gel optical elements. As an application, a sol-gel random phase plate was fabricated.

Hydroxyapatite, fluor-hydroxyapatite and fluorapatite produced via the sol-gel method: bonding to titanium and scanning electron microscopy.

PubMed

Tredwin, Christopher J; Georgiou, George; Kim, Hae-Won; Knowles, Jonathan C

2013-05-01

Hydroxyapatite (HA), fluor-hydroxyapatite (FHA) with varying levels of fluoride ion substitution and fluorapatite (FA) production has been characterised and optimised by the sol-gel method and the dissolution and biological properties of these materials were investigated. It was the objective of this study to investigate the potential bond strength and interaction of these materials with titanium. HA, FHA and FA were synthesised by a sol-gel method. Calcium nitrate and triethyl phosphite were used as precursors under an ethanol-water based solution. Different amounts of ammonium fluoride (NH4F) were incorporated for the preparation of the FHA and FA sol-gels. Using a spin coating technique the sol-gels were coated onto commercially pure titanium disks and crystallised at various temperatures. Using scanning electron microscopy (SEM) and elemental analysis, the surface characteristics, coating thickness and interaction of the Ti substrate and coating were investigated. The bond strengths of the coating to the Ti were investigated using an Instron Universal Load Testing Machine. Statistical analysis was performed with a two-way analysis of variance and post hoc testing with a Bonferroni correction. (1) Coating speed inversely influenced the coating thickness. (2) Increasing fluoride ion substitution and heating temperature significantly increased bond strength and (3) increasing fluoride ion substitution increased the coating thickness. FHA and FA synthesised using the sol-gel technique may offer a superior alternative to coating titanium implants with HA and plasma spraying. HA, FHA and FA materials synthesised by the sol-gel method may also have a use as bone grafting materials. Copyright © 2013 Academy of Dental Materials. Published by Elsevier Ltd. All rights reserved.

How to design cell-based biosensors using the sol-gel process.

PubMed

Depagne, Christophe; Roux, Cécile; Coradin, Thibaud

2011-05-01

Inorganic gels formed using the sol-gel process are promising hosts for the encapsulation of living organisms and the design of cell-based biosensors. However, the possibility to use the biological activity of entrapped cells as a biological signal requires a good understanding and careful control of the chemical and physical conditions in which the organisms are placed before, during, and after gel formation, and their impact on cell viability. Moreover, it is important to examine the possible transduction methods that are compatible with sol-gel encapsulated cells. Through an updated presentation of the current knowledge in this field and based on selected examples, this review shows how it has been possible to convert a chemical technology initially developed for the glass industry into a biotechnological tool, with current limitations and promising specificities.

Infrared wire-grid polarizer with sol-gel antireflection films on both sides

NASA Astrophysics Data System (ADS)

Yamada, Itsunari; Ishihara, Yoshiro

2017-12-01

We fabricated an infrared wire-grid polarizer with the high transverse magnetic (TM) polarization transmittance and high extinction ratio by soft imprint lithography, sol-gel method, and Al shadow coating processes. A zilconia film was coated on Si substrate by using sol-gel method and spin coating method. Then, sol-gel zirconia grating was formed on the back side using imprinting using a silicone mold. The polarizer was produced by depositing Al obliquely on the grating. The TM transmittance of the fabricated element was greater than 80% at a wavelength of 4.8 μm. The sol-gel zilconia films acted as antireflection films. The extinction ratio exceeded 26 dB at its wavelength.

THERMALLY STABLE NANOCRYSTALLINE TIO2 PHOTOCATALYSTS SYNTHESIZED VIA SOL-GEL METHODS MODIFIED WITH IONIC LIQUID AND SURFACTANT MOLECULES

EPA Science Inventory

Recently, sol-gel methods employing ionic liquids (ILs) have shown significant implications for the synthesis of well-defined nanostructured inorganic materials. Herein, we synthesized nanocrystalline TiO₂ particles via an alkoxide sol-gel method employing a water-immi...

Ultrasound-assisted sol-gel synthesis of ZrO2.

PubMed

Guel, Marlene Lariza Andrade; Jiménez, Lourdes Díaz; Hernández, Dora Alicia Cortés

2017-03-01

Synthesis of tetragonal ZrO 2 by both conventional sol-gel and ultrasound-assisted sol-gel methods and using a non-ionic surfactant Tween-20, was performed. A porous microstructure composed of nanometric particles was observed. Tetragonal ZrO 2 was obtained using a low heat treatment temperature of powders, 500°C by both methods. A higher crystallinity and a shorter reaction time were observed when ultrasound was used in the sol-gel method due to the cavitation phenomenon. Copyright © 2016 Elsevier B.V. All rights reserved.

Hydroxyapatite, fluor-hydroxyapatite and fluorapatite produced via the sol-gel method: dissolution behaviour and biological properties after crystallisation.

PubMed

Tredwin, Christopher J; Young, Anne M; Abou Neel, Ensanya A; Georgiou, George; Knowles, Jonathan C

2014-01-01

Hydroxyapatite (HA), fluor-hydroxyapatite (FHA) with varying levels of fluoride ion substitution and fluorapatite (FA) were synthesised by the sol-gel method as possible implant coating or bone-grafting materials. Calcium nitrate and triethyl phosphite were used as precursors under an ethanol-water based solution. Different amounts of ammonium fluoride were incorporated for the preparation of the FHA and FA sol-gels. After heating and powdering the sol-gels, dissolution behaviour was assessed using ion chromatography to measure Ca(2+) and PO4 (3-) ion release. Biological behaviour was assessed using cellular proliferation with human osteosarcoma cells and alamarBlue™ assay. Statistical analysis was performed with a two way analysis of variance and post hoc testing with a Bonferroni correction. Increasing fluoride substitution into an apatite structure decreased the dissolution rate. Increasing the firing temperature of the HA, FHA and FA sol-gels up to 1,000 °C decreased the dissolution rate. There was significantly higher cellular proliferation on highly substituted FHA and FA than on HA or Titanium. The properties of an implant coating or bone grafting material can be tailored to meet specific requirements by altering the amount of fluoride that is incorporated into the original apatite structure. The dissolution behaviour can further be altered by the temperature at which the sol-gel is fired.

Room temperature ferromagnetism of tin oxide nanocrystal based on synthesis methods

NASA Astrophysics Data System (ADS)

Sakthiraj, K.; Hema, M.; Balachandrakumar, K.

2016-04-01

The experimental conditions used in the preparation of nanocrystalline oxide materials play an important role in the room temperature ferromagnetism of the product. In the present work, a comparison was made between sol-gel, microwave assisted sol-gel and hydrothermal methods for preparing tin oxide nanocrystal. X-ray diffraction analysis indicates the formation of tetragonal rutile phase structure for all the samples. The crystallite size was estimated from the HRTEM images and it is around 6-12 nm. Using optical absorbance measurement, the band gap energy value of the samples has been calculated. It reveals the existence of quantum confinement effect in all the prepared samples. Photoluminescence (PL) spectra confirms that the luminescence process originates from the structural defects such as oxygen vacancies present in the samples. Room temperature hysteresis loop was clearly observed in M-H curve of all the samples. But the sol-gel derived sample shows the higher values of saturation magnetization (Ms) and remanence (Mr) than other two samples. This study reveals that the sol-gel method is superior to the other two methods for producing room temperature ferromagnetism in tin oxide nanocrystal.

Sol-gel chemistry-based Ucon-coated columns for capillary electrophoresis.

PubMed

Hayes, J D; Malik, A

1997-07-18

A sol-gel chemistry-based novel approach for the preparation of a Ucon-coated fused-silica capillary column in capillary electrophoresis is presented. In this approach the sol-gel process is carried out inside 25 microm I.D. fused-silica capillaries. The sol solution contained appropriate quantities of an alkoxide-based sol-gel precursor, a polymeric coating material (Ucon), a crosslinking reagent, a surface derivatizing reagent, controlled amounts of water and a catalyst dissolved in a suitable solvent system. The coating procedure involves filling a capillary with the sol solution and allowing the sol-gel process to proceed for an optimum period. Hydrolysis of the alkoxide precursor and polycondensation of the hydrolyzed products with the surface silanol groups and the hydroxy-terminated Ucon molecules lead to the formation of a surface-bonded sol-gel coating on the inner walls of the capillary. The thickness of the coated film can be controlled by varying the reaction time, coating solution composition and experimental conditions. Commercial availability of high purity sol-gel precursors (e.g., TEOS 99.999%), the ease of coating, run-to-run and column-to-column reproducibility, and long column lifetimes make sol-gel coating chemistry very much suitable for being applied in analytical microseparations column technology. Test samples of basic proteins and nucleotides were used to evaluate the column performance. These results show that the sol-gel coating scheme has allowed for the generation of bio-compatible surfaces characterized by high separation efficiencies in CE. For different types of solutes, the sol-gel coated Ucon column consistently provided migration time R.S.D. values of the order of 0.5%.

Outdoor weathering of sol-gel-treated wood

Treesearch

Mandla A Tshabalala; Ryan Libert; Nancy Ross Sutherland

2009-01-01

Outdoor weathering of wood specimens treated with sol-gel formulations based on methyltrimethoxysilane (MTMOS), hexadecyltrimethoxysilane (HDTMOS), and ferric-zirconia-titania (Fe-Zr-Ti) sol was evaluated. The sol-gel process allowed deposition of a thin film of hybrid inorganic-organic networks (gel) in the wood cell wall that resulted in improved outdoor weathering...

Fundamental electrochemiluminescence characteristics of fluorine-doped tin oxides synthesized by sol-gel combustion.

PubMed

Moon, B H; Chaoumead, A; Sung, Y M

2013-10-01

Fluorine-doped tin oxide (FTO) materials synthesized by sol-gel combustion method were investigated for electrochemical luminescence (ECL) application. Effects of sol-gel combustion conditions on the structures and morphology of the porous FTO (p-FTO) materials were studied. ECL efficiency of p-FTO-based cell was about 251 cd/m2 at 4 V bias, which is higher than the sell using only FTO electrodes (102.8 cd/m2). The highest intensity of the emitting light was obtained at the wavelength of about 610 nm. The porous FTO layer was effective for increasing ECL intensities.

All optical controlled photonic integrated circuits using azo dye functionized sol-gel material

NASA Astrophysics Data System (ADS)

Ke, Xianjun

The main focus of this dissertation is development and characterization of all-optical controllable azo dye functionized sol gel material, demonstrating a PIC fabrication technique on glass substrate using such material, and exploration and feasibility demonstration of three PIC functional devices namely optical variable attenuator, optical switches, and optical tunable filters using the material. The realization of all the devices in this dissertation are based on one material: dye functionalized sol-gel material. A photochromic sol-gel material functionalized with azo dye was synthesized and characterized. It possesses a photochromic characteristic under the control of green laser beam illumination. The material characteristics suggest the possibility of a new promising material platform candidate for the fabrication of alloptical controlled photonic integrated circuits. As the first potential application of the dye functionalized sol-gel material, an alloptical variable attenuator was designed and demonstrated. The optical variable attenuation is achieved in Mach-Zehnder interferometric configuration through all-optical modulation of sol-gel waveguide phase shifters. A 2 x 2 optical switch based on multimode interference (MMI) waveguide structure is proposed in the dissertation. The schematic configuration of the optical switch consists of a cascade of two identical MMIs with two all-optical controlled phase shifters realized by using the photochromic sol-gel material. The cross or bar switch state of the optical switch is determined by the phase difference between the two sol-gel waveguide phase shifters. An all-optical tunable filter is designed and its feasibility demonstrated by using the sol-gel photochromic material. Except for the phase change demonstrated on sol-gel waveguide phase shifters, dynamic gratings were observed on sol-gel film when exposed to two interference beams. This reveals the possibility of realizing Bragg grating-based tunable filters. The schematic configuration of proposed tunable filters consists of a single straight waveguide embedded with a sol-gel waveguide. The wavelength tuning of the tunable filters is accomplished by varying the grating period.

Sol-gel based oxidation catalyst and coating system using same

NASA Technical Reports Server (NTRS)

Leighty, Bradley D. (Inventor); Watkins, Anthony N. (Inventor); Patry, JoAnne L. (Inventor); Schryer, Jacqueline L. (Inventor); Oglesby, Donald M. (Inventor)

2010-01-01

An oxidation catalyst system is formed by particles of an oxidation catalyst dispersed in a porous sol-gel binder. The oxidation catalyst system can be applied by brush or spray painting while the sol-gel binder is in its sol state.

Production of continuous mullite fiber via sol-gel processing

NASA Technical Reports Server (NTRS)

Tucker, Dennis S.; Sparks, J. Scott; Esker, David C.

1990-01-01

The development of a continuous ceramic fiber which could be used in rocket engine and rocket boosters applications was investigated at the Marshall Space Flight Center. Methods of ceramic fiber production such as melt spinning, chemical vapor deposition, and precursor polymeric fiber decomposition are discussed and compared with sol-gel processing. The production of ceramics via the sol-gel method consists of two steps, hydrolysis and polycondensation, to form the preceramic, followed by consolidation into the glass or ceramic structure. The advantages of the sol-gel method include better homogeneity and purity, lower preparation temperature, and the ability to form unique compositions. The disadvantages are the high cost of raw materials, large shrinkage during drying and firing which can lead to cracks, and long processing times. Preparation procedures for aluminosilicate sol-gel and for continuous mullite fibers are described.

Production of Monodisperse Cerium Oxide Microspheres with Diameters near 100 µm by Internal Gelation Sol-Gel Methods

DOE Office of Scientific and Technical Information (OSTI.GOV)

Katalenich, Jeffrey A.; Kitchen, Brian B.; Pierson, Bruce

2018-05-01

Internal gelation sol-gel methods have used a variety of sphere forming methods in the past to produce metal oxide microspheres, but typically with poor control over the size uniformity at diameters near 100 µm. This work describes efforts to make and measure internal gelation, sol-gel microspheres with very uniform diameters in the 100 – 200 µm size range using a two-fluid nozzle. A custom apparatus was used to form aqueous droplets of sol-gel feed solutions in silicone oil and heat them to cause gelation of the spheres. Gelled spheres were washed, dried, and sintered prior to mounting on glass slidesmore » for optical imaging and analysis. Microsphere diameters and shape factors were determined as a function of silicone oil flow rate in a two-fluid nozzle and the size of a needle dispensing the aqueous sol-gel solution. Nine batches of microspheres were analyzed and had diameters ranging from 65.5 ± 2.4 µm for the smallest needle and fastest silicone oil flow rate to 211 ± 4.7 µm for the largest needle and slowest silicone oil flow rate. Standard deviations for measured diameters were less than 8% for all samples and most were less than 4%. Microspheres had excellent circularity with measured shape factors of 0.9 – 1. However, processing of optical images was complicated by shadow effects in the photoresist layer on glass slides and by overlapping microspheres. Based on calculated flow parameters, microspheres were produced in a simple dripping mode in the two-fluid nozzle. Using flow rates consistent with a simple dripping mode in a two-fluid nozzle configuration allows for very uniform oxide microspheres to be produced using the internal-gelation sol-gel method.« less

Characterisation of well-adhered ZrO2 layers produced on structured reactors using the sonochemical sol-gel method

NASA Astrophysics Data System (ADS)

Jodłowski, Przemysław J.; Chlebda, Damian K.; Jędrzejczyk, Roman J.; Dziedzicka, Anna; Kuterasiński, Łukasz; Sitarz, Maciej

2018-01-01

The aim of this study was to obtain thin zirconium dioxide coatings on structured reactors using the sonochemical sol-gel method. The preparation method of metal oxide layers on metallic structures was based on the synergistic combination of three approaches: the application of ultrasonic irradiation during the synthesis of Zr sol-gel based on a precursor solution containing zirconium(IV) n-propoxide, the addition of stabilszing agents, and the deposition of ZrO2 on the metallic structures using the dip-coating method. As a result, dense, uniform zirconium dioxide films were obtained on the FeCrAlloy supports. The structured reactors were characterised by various physicochemical methods, such as BET, AFM, EDX, XRF, XRD, XPS and in situ Raman spectroscopy. The results of the structural analysis by Raman and XPS spectroscopy confirmed that the metallic surface was covered by a ZrO2 layer without any impurities. SEM/EDX mapping revealed that the deposited ZrO2 covered the metallic support uniformly. The mechanical and high temperature tests showed that the developed ultrasound assisted sol-gel method is an efficient way to obtain thin, well-adhered zirconium dioxide layers on the structured reactors. The prepared metallic supports covered with thin ZrO2 layers may be a good alternative to layered structured reactors in several dynamics flow processes, for example for gas exhaust abatement.

Novel sol-gel organic-inorganic hybrid materials for drug delivery.

PubMed

Catauro, Michelina; Verardi, Duilio; Melisi, Daniela; Belotti, Federico; Mustarelli, Piercarlo

2010-01-01

The aim of the present study was to synthetize and characterize novel sol-gel organic-inorganic hybrid materials to be used for controlled drug delivery application. Organic-inorganic hybrid class I materials based on poly(epsilon-caprolactone) (PCL 6, 12, 24 and 50 wt%) and zirconia-yttria (ZrO2-5%Y2O3) were synthesized by a sol-gel method, from a multicomponent solution containing zirconium propoxide [Zr(OC2H7)4], yttrium chloride (YCl3), PCL, water and chloroform (CHCl3). The structure of the hybrids was obtained by means of hydrogen bonds between the Zr-OH group (H-donor) in the sol-gel intermediate species and the carboxylic group (H-acceptor) in the repeating units of the polymer. The presence of hydrogen bonds between organic-inorganic components of the hybrid materials was suggested by Fourier transform infrared (FTIR) analysis, and strongly supported by solid-state NMR. A single-step, sol-gel process was then used to precipitate microspheres containing ketoprofen or indomethacin for controlled drug delivery applications. Release kinetics in a simulated body fluid (SBF) were subsequently investigated. The amount of drug released was detected by UV-VIS spectroscopy. Pure anti-inflammatory agents exhibited linear release with time, in contrast drugs entrapped in the organic-inorganic hybrids were released with a logarithmic time dependence, starting with an initial burst effect followed by a gradual decrease. The synthesis of amorphous materials containing drugs, obtained by sol-gel methods, helps to devise new strategies for controlled drug delivery system design.

Sol-gel modification of wood substrates to retard weathering

Treesearch

Mandla A Tshabalala; Sam Williams

2008-01-01

Wood specimens were treated with sol-gel systems based on metalorganic precursors of silicon (Si), iron (Fe), zirconium (Zr), and titanium (Ti). The effect of these sol-gel systems on weathering properties of wood was investigated. These sol-gel systems were found to have a positive effect on surface color stability and water vapor resistance of the specimens. Under...

Development and application of a sol-gel immunosorbent-based method for the determination of isoproturon in surface water.

PubMed

Zhang, Xiuli; Martens, Dieter; Krämer, Petra M; Kettrup, Antonius A; Liang, Xinmiao

2006-01-13

An immunosorbent was fabricated by encapsulation of monoclonal anti-isoproturon antibodies in sol-gel matrix. The immunosorbent-based loading, rinsing and eluting processes were optimized. Based on these optimizations, the sol-gel immunosorbent (SG-IS) selectively extracted isoproturon from an artificial mixture of 68 pesticides. In addition to this high selectivity, the SG-IS proved to be reusable. The SG-IS was combined with liquid chromatography-tandem mass spectrometry (LC-MS-MS) to determine isoproturon in surface water, and the linear range was up to 2.2 microg/l with correlation coefficient higher than 0.99 and relative standard deviation (RSD) lower than 5% (n=8). The limit of quantitation (LOQ) for 25-ml surface water sample was 5 ng/l.

Porous alumina scaffold produced by sol-gel combined polymeric sponge method

NASA Astrophysics Data System (ADS)

Hasmaliza, M.; Fazliah, M. N.; Shafinaz, R. J.

2012-09-01

Sol gel is a novel method used to produce high purity alumina with nanometric scale. In this study, three-dimensional porous alumina scaffold was produced using sol-gel polymeric sponge method. Briefly, sol gel alumina was prepared by evaporation and polymeric sponge cut to designated sizes were immersed in the sol gel followed by sintering at 1250 and 1550°C. In order to study the cell interaction, the porous alumina scaffold was sterilized using autoclave prior to Human Mesenchymal Stem Cells (HMSCs) seeding on the scaffold and the cell proliferation was assessed by alamarBlue® assay. SEM results showed that during the 21 day period, HMSCs were able to attach on the scaffold surface and the interconnecting pores while maintaining its proliferation. These findings suggested the potential use of the porous alumina produced as a scaffold for implantation procedure.

Spectroscopic and electrochemical characterization of cytochrome c encapsulated in a bio sol-gel matrix.

PubMed

Deriu, Daniela; Pagnotta, Sara Emanuela; Santucci, Roberto; Rosato, Nicola

2008-08-01

Sol-gel technique represents a remarkably versatile method for protein encapsulation. To enhance sol-gel biocompatibility, systems envisaging the presence of calcium and phosphates in the sol-gel composition were recently prepared and investigated. Unfortunately, the low pH at which solutions were prepared (pH < 2.5) dramatically limited their application to proteins, because the acidic environment induces protein denaturation. In this paper we apply a new protocol based on the introduction of calcium nitrate to the inorganic phase, with formation of a binary bioactive system. In this case protein encapsulation results versatile and secure, being achieved at a pH close to neutrality (pH 6.0); also, the presence of calcium is expected to enhance system biocompatibility. To determine the properties of the salt-doped sol-gel and the influence exerted on entrapped biosystems, the structural and functional properties of embedded cytochrome c have been investigated. Data obtained indicate that the salt-doped sol-gel induces no significant change in the structure and the redox properties of the embedded protein; also, the matrix increases protein stability. Interestingly, the presence of calcium nitrate appears determinant for refolding of the acid-denatured protein. This is of interest in the perspective of future applications in biosensoristic area.

Infrared and Raman spectra of triacetoxyvinylsilane, aqueous sol-gel and xerogel

NASA Astrophysics Data System (ADS)

Li, Ying-Sing; Ba, Abdul; Mahmood, Maleeha S.

2009-04-01

Triacetoxyvinylsilane (TAVS) has been used as a precursor to prepare sol-gel under aqueous conditions. The sol-gel product has been applied for the surface treatment of aluminum. Infrared and Raman spectra have been collected for TAVS and for TAVS sol-gel, xerogel and sol-gel-coated aluminum. Vibrational analyses have been suggested for the recorded spectra based essentially on the group frequencies and the spectral variation with the change of the sol-gel product states and the vibrational assignments of similar molecules. From the recorded infrared and Raman spectra of the sol-gel and xerogel, it is found that the sol-gel produced in the process with TAVS is essentially the same as that prepared from vinyltriethoxysilane. Thermo-gravimetric analysis (TGA) of TAVS xerogel has been conducted, and an explanation has been given in coordination with the results obtained from IR spectroscopic study of the xerogels cured at different temperatures. The study has demonstrated the thermal effect on the condensation of the sol-gel process and on the vinyl decomposition of TAVS xerogel.

Fast and efficient proteolysis by reusable pepsin-encapsulated magnetic sol-gel material for mass spectrometry-based proteomics applications.

PubMed

Kayili, H Mehmet; Salih, Bekir

2016-08-01

Hydrophobic silicon-based material having magnetic properties was fairly synthesized by a classical sol-gel approach. Pepsin enzyme was encapsulated in the sol-gel material and the enzyme activity was evaluated in consequence of the digestion of some common proteins such as α- and β-casein, cytochrome c, myoglobin, and bovine serum albumin (BSA) both in a single protein batch and in the protein mixture. The optimum digestion time of the studied proteins using pepsin-encapsulated magnetic sol-gel material was found to be 20min. To produce the magnetic sol-gel material for convenient and easy proteomics applications, Fe3O4 was doped inside sol-gel material during the gelation step. It was observed that the activity of encapsulated pepsin was not affected by the amount of Fe3O4. Poly(ethylene glycol) was also inserted in sol-gel bulk to obtain suitable roughness and increase the hydrophilicity of the material surface to let protein molecules reach to the sol-gel material easily. The digestion of the protein mixture and non-fat bovine milk was performed with the pepsin-encapsulated magnetic sol-gel material and the digested solutions were analyzed using SDS-PAGE, MALDI-TOF-MS and LC-MS/MS for the protein identification. Reusability of the pepsin-encapsulated sol-gel material was examined and it was determined that they could be used at least 20 times. Finally, IgG digestions with a fast incubation time period were carried out using pepsin-encapsulated sol-gel material for generation of (Fab)2 product to evaluate the kinetic performance of the material. Copyright © 2016 Elsevier B.V. All rights reserved.

Generation of a mesoporous silica MSU shell onto solid core silica nanoparticles using a simple two-step sol-gel process.

PubMed

Allouche, Joachim; Dupin, Jean-Charles; Gonbeau, Danielle

2011-07-14

Silica core-shell nanoparticles with a MSU shell have been synthesized using several non-ionic poly(ethylene oxide) based surfactants via a two step sol-gel method. The materials exhibit a typical worm-hole pore structure and tunable pore diameters between 2.4 nm and 5.8 nm.

An investigation of GaN thin films on AlN on sapphire substrate by sol-gel spin coating method

NASA Astrophysics Data System (ADS)

Amin, Nur Fahana Mohd; Ng, Sha Shiong

2017-12-01

In this research, the gallium nitride (GaN) thin films were deposited on aluminium nitride on sapphire (AlN/Al2O3) substrate by sol-gel spin coating method. Simple ethanol-based precursor with the addition of diethanolamine solution was used. The structural and morphology properties of synthesized GaN thin films were characterized by using X-ray Diffraction, Field-Emission Scanning Electron Microscopy and Atomic Force Microscopy. While the elemental compositions and the lattice vibrational properties of the films were investigated by means of the Energy Dispersive X-ray spectroscopy and Raman spectroscopy. All the results revealed that the wurtzite structure GaN thin films with GaN(002) preferred orientation and smooth surface morphology were successfully grown on AlN/Al2O3 substrate by using inexpensive and simplified sol-gel spin coating technique. The sol-gel spin coated GaN thin film with lowest oxygen content was also achieved.FESEM images show that GaN thin films with uniform and packed grains were formed. Based on the obtained results, it can be concluded that wurtzite structure GaN thin films were successfully deposited on AlN/Al2O3 substrate.

Fabrication and characterization of highly transparent and conductive indium tin oxide films made with different solution-based methods

NASA Astrophysics Data System (ADS)

Xia, N.; Gerhardt, R. A.

2016-11-01

Solution-based fabrication methods can greatly reduce the cost and broaden the applications of transparent conducting oxides films, such as indium tin oxide (ITO) films. In this paper, we report on ITO films fabricated by spin coating methods on glass substrates with two different ITO sources: (1) a commercial ITO nanopowder water dispersion and (2) a sol-gel ITO solution. A simple and fast air annealing process was used to treat as-coated ITO films on a controlled temperature hot plate. Thermogravimetric analysis and x-ray diffraction showed that highly crystalline ITO films were formed after the annealing steps. The final ITO films had a good combination of optical properties and electrical properties, especially for films made from five layers of sol-gel ITO (92.66% transmittance and 8.7 × 10-3 Ω cm resistivity). The surface morphology and conducting network on the ITO films were characterized by non-contact and current atomic force microscopy. It was found that conducting paths were only partially connected for the nanoparticle ITO dispersion films, whereas the sol-gel ITO films had a more uniformly distributed conducting network on the surface. We also used the sol-gel ITO films to fabricate a simple liquid crystal display (LCD) device to demonstrate the excellent properties of our films.

Sol-gel approach to in situ creation of high pH-resistant surface-bonded organic-inorganic hybrid zirconia coating for capillary microextraction (in-tube SPME).

PubMed

Alhooshani, Khalid; Kim, Tae-Young; Kabir, Abuzar; Malik, Abdul

2005-01-07

A novel zirconia-based hybrid organic-inorganic sol-gel coating was developed for capillary microextraction (CME) (in-tube SPME). High degree of chemical inertness inherent in zirconia makes it very difficult to covalently bind a suitable organic ligand to its surface. In the present work, this problem was addressed from a sol-gel chemistry point of view. Principles of sol-gel chemistry were employed to chemically bind a hydroxy-terminated silicone polymer (polydimethyldiphenylsiloxane, PDMDPS) to a sol-gel zirconia network in the course of its evolution from a highly reactive alkoxide precursor undergoing controlled hydrolytic polycondensation reactions. A fused silica capillary was filled with a properly designed sol solution to allow for the sol-gel reactions to take place within the capillary for a predetermined period of time (typically 15-30 min). In the course of this process, a layer of the evolving hybrid organic-inorganic sol-gel polymer got chemically anchored to the silanol groups on the capillary inner walls via condensation reaction. At the end of this in-capillary residence time, the unbonded part of the sol solution was expelled from the capillary under helium pressure, leaving behind a chemically bonded sol-gel zirconia-PDMDPS coating on the inner walls. Polycyclic aromatic hydrocarbons, ketones, and aldehydes were efficiently extracted and preconcentrated from dilute aqueous samples using sol-gel zirconia-PDMDPS coated capillaries followed by thermal desorption and GC analysis of the extracted solutes. The newly developed sol-gel hybrid zirconia coatings demonstrated excellent pH stability, and retained the extraction characteristics intact even after continuous rinsing with a 0.1 M NaOH solution for 24 h. To our knowledge, this is the first report on the use of a sol-gel zirconia-based hybrid organic-inorganic coating as an extraction medium in solid phase microextraction (SPME).

Synthesis of Hollow Sphere and 1D Structural Materials by Sol-Gel Process.

PubMed

Li, Fa-Liang; Zhang, Hai-Jun

2017-08-25

The sol-gel method is a simple and facile wet chemical process for fabricating advanced materials with high homogeneity, high purity, and excellent chemical reactivity at a relatively low temperature. By adjusting the processing parameters, the sol-gel technique can be used to prepare hollow sphere and 1D structural materials that exhibit a wide application in the fields of catalyst, drug or gene carriers, photoactive, sensors and Li-ion batteries. This feature article reviewed the development of the preparation of hollow sphere and 1D structural materials using the sol-gel method. The effects of calcination temperature, soaking time, pH value, surfactant, etc., on the preparation of hollow sphere and 1D structural materials were summarized, and their formation mechanisms were generalized. Finally, possible future research directions of the sol-gel technique were outlined.

Synthesis of Hollow Sphere and 1D Structural Materials by Sol-Gel Process

PubMed Central

Li, Fa-Liang; Zhang, Hai-Jun

2017-01-01

The sol-gel method is a simple and facile wet chemical process for fabricating advanced materials with high homogeneity, high purity, and excellent chemical reactivity at a relatively low temperature. By adjusting the processing parameters, the sol-gel technique can be used to prepare hollow sphere and 1D structural materials that exhibit a wide application in the fields of catalyst, drug or gene carriers, photoactive, sensors and Li-ion batteries. This feature article reviewed the development of the preparation of hollow sphere and 1D structural materials using the sol-gel method. The effects of calcination temperature, soaking time, pH value, surfactant, etc., on the preparation of hollow sphere and 1D structural materials were summarized, and their formation mechanisms were generalized. Finally, possible future research directions of the sol-gel technique were outlined. PMID:28841188

Investigation of optical properties of anthocyanin doped into sol-gel based matrix

NASA Astrophysics Data System (ADS)

Hashim, Hasrina; Abdul Aziz, Nik Mohd Azmi Nik; Isnin, Aishah

2012-06-01

Anthocyanin dye was extracted from petal of Hibiscus rosasinensis (Bunga Raya) and doped into sol-gel based matrix to investigate an effect of pH change on its optical properties. Sol-gel matrix based on Vinyl triethoxysilene (VTES) as a precursor was prepared through Sol-gel process at pH 7. The sol was doped with 0.1% of Anthocyanin and the same amount of dye was also dissolved in ethanol as a comparative sample. Hydrochloric Acid, HCl and Tetramethylammonium Hydroxide, TMAH were used to change the pH value by adding them at various concentrations into each sample. The emission spectra and chemical structures of the samples were measured by Spectrofluorometer and Fourier Transform Infrared (FTIR) respectively. When excited at 410 nm, two emission peaks at about 492 and 574 nm were observed for Anthocyanin in acidic environment both in ethanol and VTES sol. In base environment however, only Anthocyanin dissolved in ethanol produced emission peak with a single peak at about 539 nm. The sensitivity of Anthocyanin dye toward pH changes in VTES open a possibility to use it as sensing element in which sol-gel based matrix are known to have higher mechanical strength and thermal stability.

Nanocrystal/sol-gel nanocomposites

DOEpatents

Petruska, Melissa A [Los Alamos, NM; Klimov, Victor L [Los Alamos, NM

2007-06-05

The present invention is directed to solid composites including colloidal nanocrystals within a sol-gel host or matrix and to processes of forming such solid composites. The present invention is further directed to alcohol soluble colloidal nanocrystals useful in formation of sol-gel based solid composites.

Nanocrystal/sol-gel nanocomposites

DOEpatents

Petruska, Melissa A [Los Alamos, NM; Klimov, Victor L [Los Alamos, NM

2012-06-12

The present invention is directed to solid composites including colloidal nanocrystals within a sol-gel host or matrix and to processes of forming such solid composites. The present invention is further directed to alcohol soluble colloidal nanocrystals useful in formation of sol-gel based solid composites

Production of monodisperse cerium oxide microspheres with diameters near 100 μm by internal-gelation sol–gel methods

DOE Office of Scientific and Technical Information (OSTI.GOV)

Katalenich, Jeffrey A.; Kitchen, Brian B.; Pierson, Bruce D.

Internal gelation sol-gel methods have used a variety of sphere forming methods in the past to produce metal oxide microspheres, but typically with poor control over the size uniformity at diameters near 100 µm. This work describes efforts to make and measure internal gelation, sol-gel microspheres with very uniform diameters in the 100 – 200 µm size range using a two-fluid nozzle. A custom apparatus was used to form aqueous droplets of sol-gel feed solutions in silicone oil and heat them to cause gelation of the spheres. Gelled spheres were washed, dried, and sintered prior to mounting on glass slidesmore » for optical imaging and analysis. Microsphere diameters and shape factors were determined as a function of silicone oil flow rate in a two-fluid nozzle and the size of a needle dispensing the aqueous sol-gel solution. Nine batches of microspheres were analyzed and had diameters ranging from 65.5 ± 2.4 µm for the smallest needle and fastest silicone oil flow rate to 211 ± 4.7 µm for the largest needle and slowest silicone oil flow rate. Standard deviations for measured diameters were less than 8% for all samples and most were less than 4%. Microspheres had excellent circularity with measured shape factors of 0.9 – 1. However, processing of optical images was complicated by shadow effects in the photoresist layer on glass slides and by overlapping microspheres. Based on calculated flow parameters, microspheres were produced in a simple dripping mode in the two-fluid nozzle. Using flow rates consistent with a simple dripping mode in a two-fluid nozzle configuration allows for very uniform oxide microspheres to be produced using the internal-gelation sol-gel method.« less

Cholesterol biosensor based on a plastic optical fibre with sol-gel: structural analysis and sensing properties

NASA Astrophysics Data System (ADS)

Razo-Medina, D. A.; Trejo-Durán, M.; Alvarado-Méndez, E.

2018-02-01

In this paper, we report the design and characterization of an optical fibre cholesterol biosensor by using sol-gel immobilization technique. The cholesterol enzyme is encapsulated inside of the sol-gel film onto an end of a plastic optical fibre. Two film deposition methods (Dip-Coating and Immersion) were studied. The morphology analysis and sensing properties permit us to determine the best film deposition to sense cholesterol concentration. The range of measured is 4.4-5.2 mM in real time and our results were validated by comparing them with other previously published results. The biosensor is portable, simple cheap, and easy to use.

Sol-gel derived flexible silica aerogel as selective adsorbent for water decontamination from crude oil.

PubMed

Abolghasemi Mahani, A; Motahari, S; Mohebbi, A

2018-04-01

Oil spills are the most important threat to the sea ecosystem. The present study is an attempt to investigate the effects of sol-gel parameters on seawater decontamination from crude oil by use of flexible silica aerogel. To this goal, methyltrimethoxysilane (MTMS) based silica aerogels were prepared by two-step acid-base catalyzed sol-gel process, involving ambient pressure drying (APD) method. To investigate the effects of sol-gel parameters, the aerogels were prepared under two different acidic and basic pH values (i.e. 4 and 8) and varied ethanol/MTMS molar ratios from 5 to 15. The adsorption capacity of the prepared aerogels was evaluated for two heavy and light commercial crude oils under multiple adsorption-desorption cycles. To reduce process time, desorption cycles were carried out by using roll milling for the first time. At optimum condition, silica aerogels are able to uptake heavy and light crude oils with the order of 16.7 and 13.7, respectively. Copyright © 2017 Elsevier Ltd. All rights reserved.

pH-resistant titania hybrid organic-inorganic sol-gel coating for solid-phase microextraction of polar compounds.

PubMed

Li, Xiujuan; Gao, Jie; Zeng, Zhaorui

2007-05-02

A novel titania-hydroxy-terminated silicone oil (titania-OH-TSO) sol-gel coating was developed for solid-phase microextraction of polar compounds. In general, titania-based sol-gel reaction is very fast and need to be decelerated by the use of suitable chelating agents. But in the present work, a judiciously designed sol solution ingredients was used to create the titania-OH-TSO coating without the addition of any chelating agent, which simplified the sol-gel procedure. Thanks to the variety of titania's adsorption sites and their acid-base characteristics, aromatic amines, phenols and polycyclic aromatic hydrocarbons were efficiently extracted and preconcentrated from aqueous samples followed by thermal desorption and GC analysis. The newly developed sol-gel hybrid titania coating demonstrated excellent pH stability, and retained its extraction characteristics intact even after continuous rinsing with a 3 M HCl or NaOH solution for 12 h. Furthermore, it could withstand temperatures as high as 320 degrees C. Practical application was demonstrated through the analysis of six aromatic amines in dye process wastewater. A linearity of four orders of magnitude was obtained with correlation coefficient better than 0.9982. The detection limits ranged from 0.22 to 0.84 microg L(-1) and the repeatability of the measurements was <7.0%. The recoveries of these compounds studied in the wastewater were in the ranges 83.6-101.4%, indicating the method accuracy.

Sol-gel-based biosensing applied to medicinal science.

PubMed

Moreira, Felismina T C; Moreira-Tavares, Ana P; Sales, M Goreti F

2015-01-01

Biosensors have opened new horizons in biomedical analysis, by ensuring increased assay speed and flexibility, and allowing point-of-care applications, multi-target analyses, automation and reduced costs of testing. This has been a result of many studies merging nanotechnology with biochemistry over the years, thereby enabling the creation of more suitable environments to biological receptors and their substitution by synthetic analogue materials. Sol-gel chemistry, among other materials, is deeply involved in this process. Sol-gel processing allows the immobilization of organic molecules, biomacromolecules and cells maintaining their properties and activities, permitting their integration into different transduction devices, of electrochemical or optical nature, for single or multiple analyses. Sol-gel also allows to the production of synthetic materials mimicking the activity of natural receptors, while bringing advantages, mostly in terms of cost and stability. Moreover, the biocompatibility of sol-gel materials structures of biological nature allowed the use of these materials in emerging in vivo applications. In this chapter, biosensors for biomedical applications based on sol-gel derived composites are presented, compared and described, along with current emerging applications in vivo, concerning drug delivery or biomaterials. Sol-gel materials are shown as a promising tool for current, emerging and future medical applications.

Solvent-resistant sol-gel polydimethyldiphenylsiloxane coating for on-line hyphenation of capillary microextraction with high-performance liquid chromatography.

PubMed

Segro, Scott S; Malik, Abdul

2008-09-26

A sol-gel polydimethyldiphenylsiloxane (PDMDPS) coating was developed for capillary microextraction on-line hyphenated with high-performance liquid chromatography (HPLC). This coating was created using methyltrimethoxysilane (MTMS) as the sol-gel precursor and di-hydroxy-terminated PDMDPS as the sol-gel active polymer. The methyl and phenyl groups on the sol-gel active polymer and the methyl groups on the sol-gel precursor ultimately turned into pendant groups providing the ability to extract non-polar analytes. A 40-cm segment of 0.25 mm I.D. fused silica capillary containing the sol-gel PDMDPS coating was installed as an external sampling loop in an HPLC injection port. Aqueous samples containing polycyclic aromatic hydrocarbons (PAHs), aromatic compounds, ketones, and aldehydes were passed through this capillary wherein the analytes were extracted by the sol-gel coating. The extracted analytes were then transferred to the HPLC column using isocratic or gradient elution with an acetonitrile/water mobile phase. This capillary demonstrated excellent extraction capability for non-polar (e.g., polycyclic aromatic hydrocarbons and aromatic compounds) as well as moderately polar compounds, such as aromatic amines, ketones, and aldehydes. The test results indicate that PDMDPS can be successfully immobilized into a sol-gel network and that the resulting solvent-resistant sol-gel organic-inorganic hybrid coating can be effectively used for on-line hyphenation of capillary microextraction with high-performance liquid chromatography. The test results also indicate that the sol-gel PDMDPS coated capillary is resistant to high-temperature solvents, making it suitable for applications in high-temperature HPLC. To the best of our knowledge, this is the first report on the creation of a silica-based sol-gel PDMDPS coating used in capillary microextraction on-line hyphenated to HPLC.

Fabrication of advanced electrochemical energy materials using sol-gel processing techniques

NASA Technical Reports Server (NTRS)

Chu, C. T.; Chu, Jay; Zheng, Haixing

1995-01-01

Advanced materials play an important role in electrochemical energy devices such as batteries, fuel cells, and electrochemical capacitors. They are being used as both electrodes and electrolytes. Sol-gel processing is a versatile solution technique used in fabrication of ceramic materials with tailored stoichiometry, microstructure, and properties. The application of sol-gel processing in the fabrication of advanced electrochemical energy materials will be presented. The potentials of sol-gel derived materials for electrochemical energy applications will be discussed along with some examples of successful applications. Sol-gel derived metal oxide electrode materials such as V2O5 cathodes have been demonstrated in solid-slate thin film batteries; solid electrolytes materials such as beta-alumina for advanced secondary batteries had been prepared by the sol-gel technique long time ago; and high surface area transition metal compounds for capacitive energy storage applications can also be synthesized with this method.

Functional nucleic acid entrapment in sol-gel derived materials.

PubMed

Carrasquilla, Carmen; Brennan, John D

2013-10-01

Functional nucleic acids (FNAs) are single-stranded DNA or RNA molecules, typically generated through in vitro selection, that have the ability to act as receptors for target molecules (aptamers) or perform catalysis of a chemical reaction (deoxyribozymes and ribozymes). Fluorescence-signaling aptamers and deoxyribozymes have recently emerged as promising biological recognition and signaling elements, although little has been done to evaluate their potential for solid-phase assays, particularly with species made of RNA due to their lack of chemical stability and susceptibility to nuclease attack. Herein, we present a detailed overview of the methods utilized for solid-phase immobilization of FNAs using a sol-gel entrapment method that can provide protection from nuclease degradation and impart long-term chemical stability to the FNA reporter systems, while maintaining their signaling capabilities. This article will also provide a brief review of the results of such entrapment studies involving fluorescence-signaling versions of a DNA aptamer, selected RNA-cleaving deoxyribozymes, and two different RNA aptamers in a series of sol-gel derived composites, ranging from highly polar silica to hydrophobic methylsilsesquioxane-based materials. Given the ability to produce sol-gel derived materials in a variety of configurations, particularly as thin film coatings on electrodes, optical fibers, and other devices, this entrapment method should provide a useful platform for numerous solid-phase FNA-based biosensing applications. Copyright © 2013 Elsevier Inc. All rights reserved.

Nanosilica coating for bonding improvements to zirconia.

PubMed

Chen, Chen; Chen, Gang; Xie, Haifeng; Dai, Wenyong; Zhang, Feimin

2013-01-01

Resin bonding to zirconia cannot be established from standard methods that are currently utilized in conventional silica-based dental ceramics. The solution-gelatin (sol-gel) process is a well developed silica-coating technique used to modify the surface of nonsilica-based ceramics. Here, we use this technique to improve resin bonding to zirconia, which we compared to zirconia surfaces treated with alumina sandblasting and tribochemical silica coating. We used the shear bond strength test to examine the effect of the various coatings on the short-term resin bonding of zirconia. Furthermore, we employed field emission scanning electron microscopy, energy-dispersive X-ray spectroscopy, atomic force microscopy, and Fourier transform infrared spectroscopy to characterize the zirconia surfaces. Water-mist spraying was used to evaluate the durability of the coatings. To evaluate the biological safety of the experimental sol-gel silica coating, we conducted an in vitro Salmonella typhimurium reverse mutation assay (Ames mutagenicity test), cytotoxicity tests, and in vivo oral mucous membrane irritation tests. When compared to the conventional tribochemical silica coating, the experimental sol-gel silica coating provided the same shear bond strength, higher silicon contents, and better durability. Moreover, we observed no apparent mutagenicity, cytotoxicity, or irritation in this study. Therefore, the sol-gel technique represents a promising method for producing silica coatings on zirconia.

Spatially resolved speckle-correlometry of sol-gel transition

NASA Astrophysics Data System (ADS)

Isaeva, A. A.; Isaeva, E. A.; Pantyukov, A. V.; Zimnyakov, D. A.

2018-04-01

Sol-gel transition was studied using the speckle correlometry method with a localized light source and spatial filtering of backscattered radiation. Water solutions of technical or food gelatin with added TiO2 nanoparticles were used as studied objects. Structural transformation of "sol-gel" system was studied at various temperatures from 25°C to 50°C using analysis of the correlation and structure functions of speckle intensity fluctuations. The characteristic temperatures of "sol - gel" transition were evaluated for studied systems. Obtained results can be used for various applications in biomedicine and food industry.

Spectroscopic studies of triethoxysilane sol-gel and coating process.

PubMed

Li, Ying-Sing; Ba, Abdul

2008-10-01

Silica sol-gels have been prepared under different conditions using triethoxysilane (TES) as precursor. The prepared sol-gels have been used to coat aluminum for corrosion protection. Vibrational assignments have been made for most vibration bands of TES, TES sol-gel, TES sol-gel-coated aluminum and xerogel. It has been noticed that air moisture may have helped the hydrolysis of the thin coating films. Xerogels have been obtained from the sol-gel under different temperature conditions and the resulting samples have been characterized by using infrared and Raman spectroscopic methods. IR data indicate that the sol-gel process is incomplete under the ambient conditions although an aqueous condition can have slightly improved the process. Two nonequivalent silicon atoms have been identified from the collected 29Si NMR spectra for the sol-gel, supporting the result derived from the IR data. The frequency of Si-H bending vibration has been found to be more sensitive to the skeletal structure than that of the Si-H stretching vibration. A higher temperature condition could favor the progression of hydrolysis and condensation. A temperature higher than 300 degrees C would cause sample decomposition without seriously damaging the silica network. From infrared intensity measurements and thermo-gravimetric analyses, the fractions of incomplete hydrolysis and condensation species have been estimated to be 4% and 3%, respectively. Electrochemical data have shown that the sol-gel coating significantly improves the corrosion protection properties of aluminum.

Hydrophobicity of hemp shiv treated with sol-gel coatings

NASA Astrophysics Data System (ADS)

Hussain, Atif; Calabria-Holley, Juliana; Schorr, Diane; Jiang, Yunhong; Lawrence, Mike; Blanchet, Pierre

2018-03-01

This is the first time sol-gel technology is used in the treatment of hemp shiv to develop sustainable thermal insulation building materials. The impact on the hydrophobicity of hemp shiv by depositing functionalised sol-gel coatings using hexadecyltrimethoxysilane (HDTMS) has been investigated. Bio-based materials have tendency to absorb large amounts of water due to their hydrophilic nature and highly porous structure. In this work, the influence of catalysts, solvent dilution and HDTMS loading in the silica sols on the hydrophobicity of hemp shiv surface has been reported. The hydrophobicity of sol-gel coated hemp shiv increased significantly when using acid catalysed sols which provided water contact angles of up to 118° at 1% HDTMS loading. Ethanol diluted sol-gel coatings enhanced the surface roughness of the hemp shiv by 36% as observed under 3D optical profilometer. The XPS results revealed that the surface chemical composition of the hemp shiv was altered by the sol-gel coating, blocking the hydroxyl sites responsible for hydrophilicity.

Sol-Gel Manufactured Energetic Materials

DOEpatents

Simpson, Randall L.; Lee, Ronald S.; Tillotson, Thomas M.; Hrubesh, Lawrence W.; Swansiger, Rosalind W.; Fox, Glenn A.

2005-05-17

Sol-gel chemistry is used for the preparation of energetic materials (explosives, propellants and pyrotechnics) with improved homogeneity, and/or which can be cast to near-net shape, and/or made into precision molding powders. The sol-gel method is a synthetic chemical process where reactive monomers are mixed into a solution, polymerization occurs leading to a highly cross-linked three dimensional solid network resulting in a gel. The energetic materials can be incorporated during the formation of the solution or during the gel stage of the process. The composition, pore, and primary particle sizes, gel time, surface areas, and density may be tailored and controlled by the solution chemistry. The gel is then dried using supercritical extraction to produce a highly porous low density aerogel or by controlled slow evaporation to produce a xerogel. Applying stress during the extraction phase can result in high density materials. Thus, the sol-gel method can be used for precision detonator explosive manufacturing as well as producing precision explosives, propellants, and pyrotechnics, along with high power composite energetic materials.

Sol-gel manufactured energetic materials

DOEpatents

Simpson, Randall L.; Lee, Ronald S.; Tillotson, Thomas M.; Hrubesh, Lawrence W.; Swansiger, Rosalind W.; Fox, Glenn A.

2003-12-23

Sol-gel chemistry is used for the preparation of energetic materials (explosives, propellants and pyrotechnics) with improved homogeneity, and/or which can be cast to near-net shape, and/or made into precision molding powders. The sol-gel method is a synthetic chemical process where reactive monomers are mixed into a solution, polymerization occurs leading to a highly cross-linked three dimensional solid network resulting in a gel. The energetic materials can be incorporated during the formation of the solution or during the gel stage of the process. The composition, pore, and primary particle sizes, gel time, surface areas, and density may be tailored and controlled by the solution chemistry. The gel is then dried using supercritical extraction to produce a highly porous low density aerogel or by controlled slow evaporation to produce a xerogel. Applying stress during the extraction phase can result in high density materials. Thus, the sol-gel method can be used for precision detonator explosive manufacturing as well as producing precision explosives, propellants, and pyrotechnics, along with high power composite energetic materials.

Making MgO/SiO2 Glasses By The Sol-Gel Process

NASA Technical Reports Server (NTRS)

Bansal, Narottam P.

1989-01-01

Silicon dioxide glasses containing 15 mole percent magnesium oxide prepared by sol-gel process. Not made by conventional melting because ingredients immiscible liquids. Synthesis of MgO/SiO2 glass starts with mixing of magnesium nitrate hexahydrate with silicon tetraethoxide, both in alcohol. Water added, and transparent gel forms. Subsequent processing converts gel into glass. Besides producing glasses of new composition at lower processing temperatures, sol-gel method leads to improved homogeneity and higher purity.

Solventless sol-gel chemistry through ring-opening polymerization of bridged disilaoxacyclopentanes

DOE Office of Scientific and Technical Information (OSTI.GOV)

RAHIMIAN,KAMYAR; LOY,DOUGLAS A.

2000-05-01

Ring-opening polymerization (ROP) of disilaoxacyclopentanes has proven to be an excellent approach to sol-gel type hybrid organic-inorganic materials. These materials have shown promise as precursors for encapsulation and microelectronics applications. The polymers are highly crosslinked and are structurally similar to traditional sol-gels, but unlike typical sol-gels they are prepared by an organic base or Bronsted acid (formic or triflic acid), without the use of solvents and water, they have low VOC's and show little shrinkage during processing.

Investigations on photolon-and porphyrin-doped sol-gel fiberoptic coatings for laser-assisted applications in medicine

NASA Astrophysics Data System (ADS)

Bindig, U.; Ulatowska-Jarza, A.; Kopaczynska, M.; Müller, G.; Podbielska, H.

2008-01-01

In view of laser-assisted medical applications, the construction of silica-based sol-gel fiberoptic sensors based on photolon (Ph) and protoporphyrin IX (PP IX) is discussed. Electron microscopy and AFM were used to characterize the silica sol-gel coatings. AFM measurements indicate a change in the surface porosity. The PP IX-based sensors were constructed as a one-layer optode as well as a multilayered structure. An additional hybrid sensor made up of alternate layers of PP IX-and Ph-doped sol-gel was also constructed and examined. Sol-gel matrices were prepared from silicate precursor tetraethylorthosilicate (TEOS) mixed with ethanol in acid-catalyzed hydrolysis. The carrier matrices of photosensitive dyes were produced with factor R = 20, where R denotes the ratio of solvent moles (ethanol) to the number of TEOS moles. A multilayered coating was built up using the reverse-dipping technique. The overall coating thickness was determined by electron microscopy. Doped sol-gels with different PP IX concentrations were used to produce fiberoptic coatings. The film optodes with a different number of layers were examined by fluorescence spectroscopy. It was found that photolon and protoporphyrin IX entrapped in sol-gel preserve their chemical reactivity and have contact with the external environment. The hybrid sensor demonstrated clear fluorescence and a reversible behavior in gaseous environments.

Theoretical Design of Multilayer Dental Posts Using CAD-Based Approach and Sol-Gel Chemistry.

PubMed

Maietta, Saverio; De Santis, Roberto; Catauro, Michelina; Martorelli, Massimo; Gloria, Antonio

2018-05-07

A computer-aided design (CAD)-based approach and sol-gel chemistry were used to design a multilayer dental post with a compositional gradient and a Young’s modulus varying from 12.4 to 2.3 GPa in the coronal-apical direction. Specifically, we propose a theoretical multilayer post design, consisting of titanium dioxide (TiO₂) and TiO₂/poly(ε-caprolactone) (PCL) hybrid materials containing PCL up to 24% by weight obtained using the sol-gel method. The current study aimed to analyze the effect of the designed multilayer dental post in endodontically treated anterior teeth. Stress distribution was investigated along and between the post and the surrounding structures. In comparison to a metal post, the most uniform distributions with lower stress values and no significant stress concentration were found when using the multilayer post.

Catalytic activity of calcium-based mixed metal oxides nanocatalysts in transesterification reaction of palm oil

NASA Astrophysics Data System (ADS)

Hassan, Noraakinah; Ismail, Kamariah Noor; Hamid, Ku Halim Ku; Hadi, Abdul

2017-12-01

Nowadays, biodiesel has become the forefront development as an alternative diesel fuel derived from biological sources such as oils of plant and fats. Presently, the conventional transesterification of vegetable oil to biodiesel gives rise to some technological problem. In this sense, heterogeneous nanocatalysts of calcium-based mixed metal oxides were synthesized through sol-gel method. It was found that significant increase of biodiesel yield, 91.75 % was obtained catalyzed by CaO-NbO2 from palm oil compared to pure CaO of 53.99 % under transesterification conditions (methanol/oil ratio 10:1, reaction time 3 h, catalyst concentration 4 wt%, reaction temperature 60 °C, and mixing speed of 600 rpm). The phase structure and crystallinity as well as the texture properties of the prepared catalysts were characterized by X-ray Diffraction (XRD) and the textural properties were characterized by N2 adsorption-desorption analysis. Sol-gel method has been known as versatile method in controlling the structural and chemical properties of the catalyst. Calcium-based mixed oxide synthesized from sol-gel method was found to exist as smaller crystallite size with high surface area.

Sol-gel method for encapsulating molecules

DOEpatents

Brinker, C. Jeffrey; Ashley, Carol S.; Bhatia, Rimple; Singh, Anup K.

2002-01-01

A method for encapsulating organic molecules, and in particular, biomolecules using sol-gel chemistry. A silica sol is prepared from an aqueous alkali metal silicate solution, such as a mixture of silicon dioxide and sodium or potassium oxide in water. The pH is adjusted to a suitably low value to stabilize the sol by minimizing the rate of siloxane condensation, thereby allowing storage stability of the sol prior to gelation. The organic molecules, generally in solution, is then added with the organic molecules being encapsulated in the sol matrix. After aging, either a thin film can be prepared or a gel can be formed with the encapsulated molecules. Depending upon the acid used, pH, and other processing conditions, the gelation time can be from one minute up to several days. In the method of the present invention, no alcohols are generated as by-products during the sol-gel and encapsulation steps. The organic molecules can be added at any desired pH value, where the pH value is generally chosen to achieve the desired reactivity of the organic molecules. The method of the present invention thereby presents a sufficiently mild encapsulation method to retain a significant portion of the activity of the biomolecules, compared with the activity of the biomolecules in free solution.

The Complex Sol-Gel Process for producing small ThO2 microspheres

NASA Astrophysics Data System (ADS)

Brykala, Marcin; Rogowski, Marcin

2016-05-01

Thorium based fuels offer several benefits compared to uranium based fuels thus they might be an attractive alternative to conventional fuel types. This study is devoted to the synthesis and the characterization of small thorium dioxide microspheres (Ø <50 μm). Their application involves using powder-free process, called the Complex Sol-Gel Process. The source sols used for the processes were prepared by the method where in the starting ascorbic acid solution the solid thorium nitrate was dissolved and partially neutralized by aqueous ammonia under pH control. The microspheres of thorium-ascorbate gel were obtained using the ICHTJ Process (INCT in English). Studies allowed to determine an optimal heat treatment with calcination temperature of 700 °C and temperature rate not higher than 2 °C/min which enabled us to obtain a crack-free surface of microspheres. The main parameters which have a strong influence on the synthesis method and features of the spherical particles of thorium dioxide are described in this article.

Biological influence of Ca/P ratio on calcium phosphate coatings by sol-gel processing.

PubMed

Catauro, M; Papale, F; Sapio, L; Naviglio, S

2016-08-01

The objective of this work has been to develop low temperature sol-gel glass coatings to modify the substrate surface and to evaluate their bioactivity and biocompatibility. Glasses, based on SiO2·CaO·P2O5, were synthesized by the sol-gel technique using tetraethyl orthosilicate, calcium nitrate tetrahydrate and triethyl phosphate as precursors of SiO2, CaO and P2O5, respectively. Those materials, still in the sol phase, have been used to coat substrates by means of the dip-coating technique. Attenuated total reflectance Fourier transform infrared (ATR-FTIR) has been used for characterize coatings and a microstructural analysis has been obtained using scanning electron microscopy (SEM). The potential applications of the coatings in the biomedical field were evaluated by bioactivity and biocompatibility tests. The coated substrate was immersed in simulated body fluid (SBF) for 21days and the hydroxyapatite deposition on its surface was subsequently evaluated via SEM-EDXS analysis, as an index of bone-bonding capability. In order to study the cell behavior and response to our silica based materials, prepared via the sol-gel method, with various Ca/P ratio and coating substrate, we have used the human osteoblast-like U2OS cell line. Copyright © 2016 Elsevier B.V. All rights reserved.

Selective filling for patterning in microfluidic channels and integration of chromatography in "lab-on-a-chip" devices using sol-gel technology

NASA Astrophysics Data System (ADS)

Jindal, Rohit

The last decade has seen tremendous advancement in the development of miniaturized chemical analysis system also known as "lab-on-a-chip". It is believed that the true potential of these devices will be achieved by integrating various functions such as separation, reaction, sensing, mixing, pumping, injection and detection onto a single chip. The ability to pattern different functionalities is indispensable for the development of highly integrated devices. In this work, a simple method based on the concept of selective filling is described for patterning in the microfluidic channels. It is based on the difference in the free energy of filling between an open and a covered part of the channel. This method was used for the integration of chromatography in the microfluidic devices. A chromatographic column was realized by utilizing sol-gel as an immobilization matrix for entrapping reversed phase chromatographic particles. Localization of the stationary phase was achieved using the selective filling technique. Channels were fabricated in quartz using photolithography and wet etching. Electroosmotic flow was used for manipulating fluid movement in the channels. Cross channel design was used for making a pulse injection of the solutes in the separation channel. An optical fiber setup was developed for carrying out on-chip UV absorbance detection. Stationary phase was created under different sol-gel synthesis conditions. It was established that the sol-gel synthesis carried out under acidic conditions provides the optimum synthesis conditions for creating separation column. Chromatographic performance of the stationary phase material was demonstrated by separating peptides present in a mixture. The sol-gel immobilization method was extended for the integration of micropump in the chip. The micropump enables pumping of the fluid in field free channels. Preliminary results, demonstrating the potential of carbon nanotubes as a support material in the microfluidic channels, were obtained using CVD (chemical vapor deposition) grown tubes in the channel. Results obtained in this work demonstrate the potential of selective filling technique along with sol-gel technology as a useful tool for the fabrication of multifunctional "lab-on-a-chip" devices.

Moisture sensor based on evanescent wave light scattering by porous sol-gel silica coating

DOEpatents

Tao, Shiquan; Singh, Jagdish P.; Winstead, Christopher B.

2006-05-02

An optical fiber moisture sensor that can be used to sense moisture present in gas phase in a wide range of concentrations is provided, as well techniques for making the same. The present invention includes a method that utilizes the light scattering phenomenon which occurs in a porous sol-gel silica by coating an optical fiber core with such silica. Thus, a porous sol-gel silica polymer coated on an optical fiber core forms the transducer of an optical fiber moisture sensor according to an embodiment. The resulting optical fiber sensor of the present invention can be used in various applications, including to sense moisture content in indoor/outdoor air, soil, concrete, and low/high temperature gas streams.

COLLABORATIVE RESEARCH AND DEVELOPMENT (CR&D) Delivery Order 0065: Nanostructured Dynamic Modulus Materials

DTIC Science & Technology

2008-03-01

solution-gelation (sol- gel) technique, to form hybrids of these materials with high-Tg open-cell foams so as to enhance shape memory characteristics , and...did not demonstrate the shape memory properties of the original Morthane thermoplastic due to the suppression of crystallinity following sol-gel...method. The utilization of photolatent bases to allow for improved reaction control and the combination of this system with Basotect™ open-cell foam in

Determination of Aromatic Amines Using Solid-Phase Microextraction Based on an Ionic Liquid-Mediated Sol-Gel Technique.

PubMed

Abbasi, Vajihe; Sarafraz-Yazdi, Ali; Amiri, Amirhassan; Vatani, Hossein

2016-04-01

A headspace solid-phase microextraction (HS-SPME) method was developed for isolation of monocyclic aromatic amines from water samples followed by gas chromatography-flame ionization detector (GC-FID). In this work, the effect of the presence of ionic liquid (namely, 1-hexyl-3-methyl-imidazolium hexafluorophosphate [C6MIM][PF6]) was investigated in the sol-gel coating solutions on the morphology and extraction behavior of the resulting hybrid organic-inorganic sol-gel sorbents utilized in SPME. Hydroxy-terminated poly(dimethylsiloxane) (PDMS) was used as the sol-gel active organic component for sol-gel hybrid coatings. Two different coated fibers that were prepared are PDMS and PDMS-IL ([C6MIM][PF6]) fibers. Under the optimal conditions, the method detection limits (S/N = 3) with PDMS-IL were in the range of 0.001-0.1 ng/mL and the limits of quantification (S/N = 10) between 0.005 and 0.5 ng/mL. The relative standard deviations for one fiber (n = 5) were obtained from 3.1 up to 8.5% and between fibers or batch to batch (n = 3) in the range of 5.3-10.1%. The developed method was successfully applied to real water and juice fruits samples while the relative recovery percentages obtained for the spiked water samples at 0.1 ng/mL were from 83.3 to 95.0%. © The Author 2016. Published by Oxford University Press. All rights reserved. For Permissions, please email: journals.permissions@oup.com.

3-(Triethoxysilyl)propionitrile sol-gel coating.

PubMed

Li, Ying-Sing; Xiao, Yun; Wright, Paul B; Tran, Tuan

2005-05-01

3-(Triethoxysilyl)propionitrile (TESPN) sol-gel has been prepared under different conditions. It was employed for coating the surfaces of quartz and aluminum. Infrared (IR) and Raman spectra of TESPN and TESPN sol-gels have been recorded in the study of the sol-gel process. Transmission and reflection absorption IR (RAIR) spectra of TESPN sol-gel coated quartz and aluminum have also been collected for better understanding the film formation on the substrate surfaces. Spectra collected at different temperatures indicated that the silane film on quartz decomposes at 700 degrees C. Results from thermal gravimetric analysis (TGA) supported this result. Based on the group frequencies and the spectral behavior in different states, some vibrational modes were assigned to the observed bands. The anticorrosion behavior of the sol-gel coated aluminum in comparison with the uncoated metal was evaluated by measuring the potentiodynamic polarization and electrochemical impedance spectra (EIS).

Investigation of corrosion protection performance of sol-gel surface treatments on AA2024-T3

NASA Astrophysics Data System (ADS)

Voevodin, Natalia Nikolajevna

The dissertation research project addresses the technologically important problem of replacement of chromate based coatings for corrosion protection of aircraft. A review of corrosion processes in high-strength aluminum alloys indicated that the strengthening intermetallic precipitates provide local cathodic areas, which may initiate surface pitting. The mechanisms of chromate inhibition in these localized corrosion processes were identified. The environmental hazard of chromates was also highlighted, serves as the impetus for chromate coating replacement. Sol-gel coatings are shown as an excellent alternative, based on environment compliance, flexibility in the composition control, and reasonable costs. Several sol-gel coatings were formulated and applied to the surface of an AA2024-T3 alloy. The coating composition and bonding were analyzed with XPS and FTIR, surface morphology was studied with SEM and AFM, and corrosion protection properties were tested with EIS, PDS, salt water immersion, and salt-fog exposure. The results demonstrated that epoxy-zirconate sol-gel coatings can provide excellent barrier properties. A novel SVET technique was applied for studies of local electrochemical processes in the pitting formation. This technique was further refined in model studies of aluminum surfaces with artificially created local cathodic regions, experimental studies of chromate inhibition with pit formation, and pitting development studies in sol-gel coatings with artificially introduced defects. Mechanisms of pitting development and inhibition with the pit initiation and growth kinetics were established. The Zr-epoxy coatings are subjected to the pit development and undercutting in the absence of the corrosion inhibitors. Several organic and non-organic inhibitors were evaluated in the sol-gel coating composition. Organic inhibitors had a better compliance with sol-gel chemistry and were identified for future studies. Experiments were performed to verify that sol-gel coatings can be used as barrier layers in complex coating systems. The results clearly demonstrated that Zr-epoxy sol-gel coatings are a viable replacement for the currently used chromate-based surface treatments. This work expands the fundamental knowledge of chromate coating replacement with chromate-free sol-gel coatings and identifies possible ways to implement this goal.

Electrochemical and spectroscopic characterization of surface sol-gel processes.

PubMed

Chen, Xiaohong; Wilson, George S

2004-09-28

(3-Mercaptopropyl)trimethoxysilane (MTS) forms a unique film on a platinum substrate by self-assembly and sol-gel cross-linking. The gelating and drying states of the self-assembled MTS sol-gel films were probed by use of electrochemical and spectroscopic methods. The thiol moiety was the only active group within the sol-gel network. Gold nanoparticles were employed to detect the availability of the thiol group and their interaction further indicated the physicochemical states of the sol-gel inner structure. It was found that the thiol groups in the open porous MTS aerogel matrix were accessible to the gold nanoparticles while thiol groups in the compact MTS xerogel network were not accessible to the gold nanoparticles. The characteristics of the sol-gel matrix change with time because of its own irreversible gelating and drying process. The present work provides direct evidence of gold nanoparticle binding with thiol groups within the sol-gel structures and explains the different permeability of "aerogel" and "xerogel" films of MTS on the basis of electrochemical and spectroscopic results. Two endogenous species, hydrogen peroxide and ascorbic acid, were used to test the permeability of the self-assembled sol-gel film in different states. The MTS xerogel film on the platinum electrode was extremely selective against ascorbic acid while maintaining high sensitivity to hydrogen peroxide in contrast to the relatively high permeability of ascorbic acid in the MTS aerogel film. This study showed the potential of the MTS sol-gel film as a nanoporous material in biosensor development.

Molecular receptors in metal oxide sol-gel materials prepared via molecular imprinting

DOEpatents

Sasaki, Darryl Y.; Brinker, C. Jeffrey; Ashley, Carol S.; Daitch, Charles E.; Shea, Kenneth J.; Rush, Daniel J.

2000-01-01

A method is provided for molecularly imprinting the surface of a sol-gel material, by forming a solution comprised of a sol-gel material, a solvent, an imprinting molecule, and a functionalizing siloxane monomer of the form Si(OR).sub.3-n X.sub.n, wherein n is an integer between zero and three and X is a functional group capable of reacting with the imprinting molecule, evaporating the solvent, and removing the imprinting molecule to form the molecularly imprinted metal oxide sol-gel material. The use of metal oxide sol-gels allows the material porosity, pore size, density, surface area, hardness, electrostatic charge, polarity, optical density, and surface hydrophobicity to be tailored and be employed as sensors and in catalytic and separations operations.

Application of Sol-Gel Method as a Protective Layer on a Specular Reflective Surface for Secondary Reflector in a Solar Receiver

DOE Office of Scientific and Technical Information (OSTI.GOV)

Afrin, Samia; Dagdelen, John; Ma, Zhiwen

Highly-specular reflective surfaces that can withstand elevated-temperatures are desirable for many applications including reflective heat shielding in solar receivers and secondary reflectors, which can be used between primary concentrators and heat collectors. A high-efficiency, high-temperature solar receiver design based on arrays of cavities needs a highly-specular reflective surface on its front section to help sunlight penetrate into the absorber tubes for effective flux spreading. Since this application is for high-temperature solar receivers, this surface needs to be durable and to maintain its optical properties through the usable life. Degradation mechanisms associated with elevated temperatures and thermal cycling, which include cracking,more » delamination, corrosion/oxidation, and environmental effects, could cause the optical properties of surfaces to degrade rapidly in these conditions. Protected mirror surfaces for these applications have been tested by depositing a thin layer of SiO2 on top of electrodeposited silver by means of the sol-gel method. To obtain an effective thin film structure, this sol-gel procedure has been investigated extensively by varying process parameters that affect film porosity and thickness. Endurance tests have been performed in a furnace at 150 degrees C for thousands of hours. This paper presents the sol-gel process for intermediate-temperature specular reflective coatings and provides the long-term reliability test results of sol-gel protected silver-coated surfaces.« less

Sol-gel process for the manufacture of high power switches

DOE Office of Scientific and Technical Information (OSTI.GOV)

Landingham, Richard L.; Satcher, Jr, Joe; Reibold, Robert

According to one embodiment, a photoconductive semiconductor switch includes a structure of nanopowder of a high band gap material, where the nanopowder is optically transparent, and where the nanopowder has a physical characteristic of formation from a sol-gel process. According to another embodiment, a method includes mixing a sol-gel precursor compound, a hydroxy benzene and an aldehyde in a solvent thereby creating a mixture, causing the mixture to gel thereby forming a wet gel, drying the wet gel to form a nanopowder, and applying a thermal treatment to form a SiC nanopowder.

Optical Fiber Chemical Sensor with Sol-Gel Derived Refractive Material as Transducer for High Temperature Gas Sensing in Clean Coal Technology

DOE Office of Scientific and Technical Information (OSTI.GOV)

Shiquan Tao

2006-12-31

The chemistry of sol-gel derived silica and refractive metal oxide has been systematically studied. Sol-gel processes have been developed for preparing porous silica and semiconductor metal oxide materials. Micelle/reversed micelle techniques have been developed for preparing nanometer sized semiconductor metal oxides and noble metal particles. Techniques for doping metal ions, metal oxides and nanosized metal particles into porous sol-gel material have also been developed. Optical properties of sol-gel derived materials in ambient and high temperature gases have been studied by using fiber optic spectroscopic techniques, such as fiber optic ultraviolet/visible absorption spectrometry, fiber optic near infrared absorption spectrometry and fibermore » optic fluorescence spectrometry. Fiber optic spectrometric techniques have been developed for investigating the optical properties of these sol-gel derived materials prepared as porous optical fibers or as coatings on the surface of silica optical fibers. Optical and electron microscopic techniques have been used to observe the microstructure, such as pore size, pore shape, sensing agent distribution, of sol-gel derived material, as well as the size and morphology of nanometer metal particle doped in sol-gel derived porous silica, the nature of coating of sol-gel derived materials on silica optical fiber surface. In addition, the chemical reactions of metal ion, nanostructured semiconductor metal oxides and nanometer sized metal particles with gas components at room temperature and high temperatures have also been investigated with fiber optic spectrometric methods. Three classes of fiber optic sensors have been developed based on the thorough investigation of sol-gel chemistry and sol-gel derived materials. The first group of fiber optic sensors uses porous silica optical fibers doped with metal ions or metal oxide as transducers for sensing trace NH{sub 3} and H{sub 2}S in high temperature gas samples. The second group of fiber optic sensors uses sol-gel derived porous silica materials doped with nanometer particles of noble metals in the form of fiber or coating for sensing trace H{sub 2}, NH{sub 3} and HCl in gas samples at for applications ambient temperature. The third classes of fiber optic sensors use sol-gel derived semiconductor metal oxide coating on the surface of silica optical fiber as transducers for selectively sensing H{sub 2}, CH{sub 4} and CO at high temperature. In addition, optical fiber temperature sensors use the fluorescence signal of rare-earth metal ions doped porous silica optical fiber or the optical absorption signal of thermochromic metal oxide materials coated on the surface of silica optical fibers have also been developed for monitoring gas temperature of corrosive gas. Based on the results obtained from this project, the principle of fiber optic sensor techniques for monitoring matrix gas components as well as trace components of coal gasification derived syngas has been established. Prototype sensors for sensing trace ammonia and hydrogen sulfide in gasification derived syngas have been built up in our laboratory and have been tested using gas samples with matrix gas composition similar to that of gasification derived fuel gas. Test results illustrated the feasibility of these sensors for applications in IGCC processes.« less

Ultrapure glass optical waveguide development in microgravity by the sol-gel process

NASA Technical Reports Server (NTRS)

Mukherjee, S. P.; Holman, R. A.

1981-01-01

Multicomponent, homogeneous, noncrystalline oxide gels can be prepared by the sol-gel process and these gels are promising starting materials for melting glasses in the space environment. The sol-gel process referred to here is based on the polymerization reaction of alkoxysilane with other metal alkoxy compounds or suitable metal salts. Many of the alkoxysilanes or other metal alkoxides are liquids and thus can be purified by distillation. The use of gels offers several advantages such as high purity and lower melting times and temperatures. The sol-gel process is studied for utilization in the preparation of multicomponent ultrapure glass batches for subsequent containerless melting of the batches in space to prepare glass blanks for optical waveguides.

Replication of butterfly wing and natural lotus leaf structures by nanoimprint on silica sol-gel films.

PubMed

Saison, Tamar; Peroz, Christophe; Chauveau, Vanessa; Berthier, Serge; Sondergard, Elin; Arribart, Hervé

2008-12-01

An original and low cost method for the fabrication of patterned surfaces bioinspired from butterfly wings and lotus leaves is presented. Silica-based sol-gel films are thermally imprinted from elastomeric molds to produce stable structures with superhydrophobicity values as high as 160 degrees water contact angle. The biomimetic surfaces are demonstrated to be tuned from superhydrophobic to superhydrophilic by annealing between 200 degrees C and 500 degrees C.

Optical properties of Na2O-TiO2-SiO2 glass films prepared by the sol-gel method

NASA Astrophysics Data System (ADS)

Barton, Ivo; Matejec, Vlastimil; Mrazek, Jan; Predoana, Luminita; Zaharescu, Maria

2017-12-01

Layers based on TiO2-SiO2 systems fabricated by sol-gel method have been investigated for the preparation of planar waveguides, antireflective coatings, Bragg mirrors, etc. However, at high titania contents such materials exhibit high viscosities and tendency to phase separation. In this paper we present optical properties of films containing TiO2 which are prepared via a novel approach sol-gel on the basis of ternary Na2O-TiO2-SiO2 glasses and which can exhibit lower viscosities. Films of Na2O-TiO2-SiO2 systems were prepared from input sols mixed of silica, titania and sodium oxide sols. The silica sol was prepared from tetraethyl orthosilicate (TEOS), ethanol, hydrochloric acid and water, with a TEOS c= 2 mol/l and water/alkoxide ratio 1.75. The titania sol was mixed from titanium tetraisopropoxide (TiPr), propan-2-ol, nitric acid and water, c= 0.5 mol/l, RW= 0.42. The sodium oxide sols with c= 0.474 mol/l were prepared from sodium ethoxide and ethanol. Input sols were prepared by mixing the silica and titania sols first and then the sodium sol was added. The input sols were aged for one hour. Stable input sols were obtained. The input sols were deposited on glass and silica slides by dip-coating technique at a withdrawing speeds of 200 mm/min. Applied gel layers were thermally treated at temperatures of 450 and 900°C. Layers containing sodium oxide and titania in concentration ranges of 0-20 mol.% and 0-30 mol.% respectively have been fabricated. Optical properties of layers were determined by UV-VIS-NIR transmission and reflection spectrophotometry. Refractive indices of layers were determined by spectral ellipsometry and from transmission spectra. Optical properties were correlated with results of XRD spectroscopy, optical microscopy, and atomic force microscopy. Transparent homogenous films with a maximum refractive index of 1.61 at a wavelength of 600 nm have been obtained.

Preparation of oxide glasses from metal alkoxides by sol-gel method

NASA Technical Reports Server (NTRS)

Kamiya, K.; Yoko, T.; Sakka, S.

1987-01-01

An investigation is carried out on the types of siloxane polymers produced in the course of the hydrolysis of silicon tetraethoxide, as well as the preparation of oxide glasses from metal alkoxides by the sol-gel method.

A comparative synthesis and physicochemical characterizations of Ni/Al2O3-MgO nanocatalyst via sequential impregnation and sol-gel methods used for CO2 reforming of methane.

PubMed

Aghamohammadi, Sogand; Haghighi, Mohammad; Karimipour, Samira

2013-07-01

Carbon dioxide reforming of methane is an interesting route for synthesis gas production especially over nano-sized catalysts. The present research deals with catalyst development for dry reforming of methane with the aim of reaching the most stable catalyst. Effect of preparation method, one of the most significant variables, on the properties of the catalysts was taken in to account. The Ni/Al2O3-MgO catalysts were prepared via sol-gel and sequential impregnation methods and characterized with XRD, FESEM, EDAX, BET and FTIR techniques. The reforming reactions were carried out using different feed ratios, gas hourly space velocities (GHSV) and reaction temperatures to identify the influence of operational variables. FESEM images indicate uniform particle size distribution for the sample synthesized with sol-gel method. It has been found that the sol-gel method has the potential to improve catalyst desired properties especially metal surface enrichment resulting in catalytic performance enhancement. The highest yield of products was obtained at 850 degrees C for both of the catalysts. During the 10 h stability test, CH4 and CO2 conversions gained higher values in the case of sol-gel made catalyst compared to impregnated one.

Spectroscopic characterization of zirconium(IV) and hafniumf(IV) gallate phthalocyanines in monolithic silica gels obtained by sol gel method

NASA Astrophysics Data System (ADS)

Gerasymchuk, Y. S.; Chernii, V. Ya.; Tomachynski, L. A.; Legendziewicz, J.; Radzki, St.

2005-07-01

The Zr(IV) and Hf(IV) phthalocyanines, with gallate as axial ligand coordinated to the central metal atom of phthalocyanine, were incorporated in silica gels during sol-gel process with using tetraethyl orthosilicate (TEOS) as precursor. The obtained mixed inorganic-organic composites were transparent and homogeneous. The absorption and emission properties of these materials in comparison with the spectra of the Zr(IV) and Hf(IV) phthalocyanines in various solvents were investigated. The spectra were correlated with various stage of the sol-gel process. It was established that in the gels concurrence of the monomer and dimer form is different in sol, alco-, hydro- and xerogels. The intensive 700-725 nm fluorescence emission upon relatively long-wavelength excitation and unusually large (about 45 nm) Stokes shift in the Q region, suggest that Zr(IV) and Hf(IV) phthalocyanines could be considered as photosensitizers in the PDT method (photodynamic therapy).

The incorporation of calix[6]arene and cyclodextrin derivatives into sol-gels for the preparation of stationary phases for gas chromatography.

PubMed

Delahousse, Guillaume; Peulon-Agasse, Valérie; Debray, Jean-Christophe; Vaccaro, Marie; Cravotto, Giancarlo; Jabin, Ivan; Cardinael, Pascal

2013-11-29

New polyethylene-glycol-based sol-gels containing cyclodextrin or calix[6]arene derivatives have been synthesized. An original method for sol-gel preparation and capillary column coating, which consumes smaller quantities of selectors and allows for control of their amounts in the stationary phase, is reported herein. The new stationary phases exhibited excellent column efficiencies over a large range of temperatures and thermal stability up to 280°C. The cyclodextrin derivative generally showed the best separation factors for aromatic positional isomers. The calix[6]arene derivative exhibited the best selectivity for the polychlorobiphenyl congeners and some polycyclic aromatic hydrocarbon isomers. The relationship between the structure and the chromatographic properties of the selectors is discussed. The tert-butyl groups on the upper rim of the calix[6]arene were found to possibly play an important role in the recognition of solutes. The incorporation of the cyclodextrin derivative into the sol-gel matrix did not affect its enantioselective recognition capabilities. Copyright © 2013 Elsevier B.V. All rights reserved.

Preparation of chitosan-graft-(β-cyclodextrin) based sol-gel stationary phase for open-tubular capillary electrochromatography.

PubMed

Lü, Haixia; Li, Qingyin; Yu, Xiaowei; Yi, Jiaojiao; Xie, Zenghong

2013-07-01

A novel open-tubular CEC column coated with chitosan-graft-(β-CD) (CDCS) was prepared using sol-gel technique. In the sol-gel approach, owing to the 3D network of sol-gel and the strong chemical bond between the stationary phase and the surface of capillary columns, good chromatographic characteristics and unique selectivity in separating isomers were shown. The column efficiencies of 55,000∼163,000 plates/m for the isomeric xanthopterin and phenoxy acid herbicides using the sol-gel-derived CDCS columns were achieved. Good stabilities were demonstrated that the RSD values for the retention time of thiourea and isoxanthopterin were 1.3 and 1.4% (run to run, n = 5), 1.6 and 2.0% (day to day, n = 3), 2.9 and 3.1% (column to column, n = 3), respectively. The sol-gel-coated CDCS columns have shown improved separations of isomeric xanthopterin in comparison with CDCS-bonded capillary column. © 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Material for surface-enhanced Raman spectroscopy, and SER sensors and method for preparing same

NASA Technical Reports Server (NTRS)

Farquharson, Stuart (Inventor); Nelson, Chad (Inventor); Lee, Yuan-Hsiang (Inventor)

2003-01-01

Metal-doped sol-gel materials, suitable for use as sensors for surface-enhanced Raman spectroscopic analysis for trace chemical detection, are produced by effecting gelation and solvent removal of a doped sol-gel under mild temperature conditions. At least in certain instances reaction and drying will desirably be effected in an oxygen-starved environment. The metal of the sol-gel material functions, when irradiated, to produce a plasmon field for interaction with molecules of an analyte in contact therewith, increasing by orders of magnitude Raman photons that are generate by excitation radiation, and the method allows matching of the metal and metal particle size to a wavelength of light (or incident radiation, e.g., laser radiation) to generate surface plasmons. The porosity of the sol-gel material dramatically increases the surface area, and thereby the amount of metal exposed for analyte interaction. The sensors provided may be in the form of glass vials, fiber optics, multi-well micro-sample plates, etc., having surface coatings of the doped sol-gel material, to provide sampling systems for use in a Raman instrument.

Synthesis and properties of nanostructured sol-gel sorbents for simultaneous removal of sulfur dioxide and nitrogen oxides from flue gas

NASA Astrophysics Data System (ADS)

Buelna Quijada, Genoveva

2001-07-01

Regenerative, alumina-supported, copper-based sorbent/catalysts provide a promising technique for simultaneous removal of SO2 and NO x from flue gas. These sorbents can remove over 90% of SO2 and 70+% of NOx while generating no wastes, reducing energy consumption, and producing valuable by-products. The lack of a cost-effective sorbent with low attrition rate and good reactivity has been the main hurdle to commercialization of this copper oxide process. Developing such a sorbent is the focus of this dissertation. This work examines using sol-gel techniques rather than traditional processes to produce gamma-alumina and copper coated 7-alumina granular sorbents. Important modifications to the established sol-gel synthesis process were made, which minimized generated wastes and reduced preparation time and sorbent cost. A laboratory scale semi-continuous process providing a basis for large-scale synthesis was developed. The effect of the copper content on the surface area and dispersion of the active species on sol-gel-derived sorbents coated by the one step and wet-impregnation methods was studied. The sol-gel-derived sorbents showed superior sulfation and regeneration properties than the existing commercial sorbents used in the copper oxide process in terms of sulfation capacity, fast regeneration, recovery of sorption capacity, and SO2 concentration in the regenerated effluent. The optimum temperature for NO reduction by NH3 over sol-gel-derived CuO/gamma-Al2O3 was found to be 350°C for both fresh and sulfated catalysts. This was also the optimum operating temperature for simultaneous removal of SO2 and NOx from simulated flue gas. At 350°C, the adsorption capacity of the sol-gel sorbent/catalyst was higher than UOP's sorbent, and very close to the capacity of ALCOA's sorbent, while the catalytic activity for NO reduction of the sol-gel-derived CuO/gamma-Al 2O3 sorbent fell between the commercial sorbents. The new mesoporous sol-gel-derived materials showed larger surface area, better mechanical strength, and more uniform dispersion of the copper species than existing commercially available sorbents. The superior mechanical properties, better cost effectiveness, and comparable efficiency for simultaneous removal of SO2 and NOx of the sol-gel-derived CuO/gamma-Al 2O3 sorbents with respect to the commercial ones make them a good option for use in the copper oxide process for combined removal of SO2 and NOx from flue gas.

Sol-gel derived sorbents

DOEpatents

Sigman, Michael E.; Dindal, Amy B.

2003-11-11

Described is a method for producing copolymerized sol-gel derived sorbent particles for the production of copolymerized sol-gel derived sorbent material. The method for producing copolymerized sol-gel derived sorbent particles comprises adding a basic solution to an aqueous metal alkoxide mixture for a pH.ltoreq.8 to hydrolyze the metal alkoxides. Then, allowing the mixture to react at room temperature for a precalculated period of time for the mixture to undergo an increased in viscosity to obtain a desired pore size and surface area. The copolymerized mixture is then added to an immiscible, nonpolar solvent that has been heated to a sufficient temperature wherein the copolymerized mixture forms a solid upon the addition. The solid is recovered from the mixture, and is ready for use in an active sampling trap or activated for use in a passive sampling trap.

Mechanical compatibility of sol-gel annealing with titanium for orthopaedic prostheses.

PubMed

Greer, Andrew I M; Lim, Teoh S; Brydone, Alistair S; Gadegaard, Nikolaj

2016-01-01

Sol-gel processing is an attractive method for large-scale surface coating due to its facile and inexpensive preparation, even with the inclusion of precision nanotopographies. These are desirable traits for metal orthopaedic prostheses where ceramic coatings are known to be osteoinductive and the effects may be amplified through nanotexturing. However there are a few concerns associated with the application of sol-gel technology to orthopaedics. Primarily, the annealing stage required to transform the sol-gel into a ceramic may compromise the physical integrity of the underlying metal. Secondly, loose particles on medical implants can be carcinogenic and cause inflammation so the coating needs to be strongly bonded to the implant. These concerns are addressed in this paper. Titanium, the dominant material for orthopaedics at present, is examined before and after sol-gel processing for changes in hardness and flexural modulus. Wear resistance, bending and pull tests are also performed to evaluate the ceramic coating. The findings suggest that sol-gel coatings will be compatible with titanium implants for an optimum temperature of 500 °C.

Three-phase molecularly imprinted sol-gel based hollow fiber liquid-phase microextraction combined with liquid chromatography-tandem mass spectrometry for enrichment and selective determination of a tentative lung cancer biomarker.

PubMed

Moein, Mohammad Mahdi; Javanbakht, Mehran; Karimi, Mohammad; Akbari-Adergani, Behrouz; Abdel-Rehim, Mohamed

2015-07-15

In the present study, the modification of a polysulfone hollow fiber membrane with in situ molecularly imprinted sol-gel process (as a novel and one-step method) was prepared and investigated. 3-(propylmethacrylate)trimethoxysilane (3PMTMOS) as an inorganic precursor was used for preparation of molecularly imprinted sol-gel. The modified molecularly imprinted sol-gel hollow fiber membrane (MSHM) was used for the liquid-phase microextraction (LPME) of hippuric acid (HA) in human plasma and urine samples. MSHM as a selective, robust, and durable tool was used for at least 50 extractions without significant decrease in the extraction efficiency. The non-molecularly imprinted sol-gel hollow fiber membrane (NSHM) as blank hollow fiber membrane was prepared by the same process, only without HA. To achieve the best condition, influential parameters on the extraction efficiency were thoroughly investigated. The capability of this robust, green, and simple method for extraction of HA was successfully accomplished with LC/MS/MS. The limits of detection (LOD) and quantification (LOQ) in human plasma and urine samples were 0.3 and 1.0nmolL(-1), respectively. The standard calibration curves were obtained within the concentration range 1-2000nmolL(-1) for HA in human plasma and urine. The coefficients of determination (r(2)) were ≥0.998. The obtained data exhibited recoveries were higher than 89% for the extraction of HA in human plasma and urine samples. Copyright © 2015 Elsevier B.V. All rights reserved.

Preparation and Optoelectrical Properties of p-CuO/n-Si Heterojunction by a Simple Sol-Gel Method

NASA Astrophysics Data System (ADS)

He, Bo; Xu, Jing; Ning, Huanpo; Zhao, Lei; Xing, Huaizhong; Chang, Chien-Cheng; Qin, Yuming; Zhang, Lei

The Cuprous oxide (CuO) thin film was prepared on texturized Si wafer by a simple sol-gel method to fabricate p-CuO/n-Si heterojunction photoelectric device. The novel sol-gel method is very cheap and convenient. The structural, optical and electrical properties of the CuO film were studied by X-ray diffraction (XRD), Scanning Electron Microscope (SEM), X-ray photoelectron spectroscopy (XPS), UV-Vis spectrophotometer and Hall effect measurement. A good nonlinear rectifying behavior is obtained for the p-CuO/n-Si heterojunction. Under reverse bias, good photoelectric behavior is obtained.

A copper ion-selective electrode with high selectivity prepared by sol-gel and coated wire techniques.

PubMed

Mazloum Ardakani, M; Salavati-Niasari, M; Khayat Kashani, M; Ghoreishi, S M

2004-03-01

A sol-gel electrode and a coated wire ion-selective poly(vinyl chloride) membrane, based on thiosemicarbazone as a neutral carrier, were successfully developed for the detection of Cu (II) in aqueous solutions. The sol-gel electrode and coated electrode exhibited linear response with Nernstian slopes of 29.2 and 28.1 mV per decade respectively, within the copper ion concentration ranges 1.0 x 10(-5) - 1.0 x 10(-1) M and 6.0 x 10(-6) - 1.0 x 10(-1) M for coated and sol-gel sensors. The coated and sol-gel electrodes show detection limits of 3.0 x 10(-6) and 6.0 x 10(-6) M respectively. The electrodes exhibited good selectivities for a number of alkali, alkaline earth, transition and heavy metal ions. The proposed electrodes have response times ranging from 10-50 s to achieve a 95% steady potential for Cu2+ concentration. The electrodes are suitable for use in aqueous solutions over a wide pH range (4-7.5). Applications of these electrodes for the determination of copper in real samples, and as an indicator electrode for potentiometric titration of Cu2+ ion using EDTA, are reported. The lifetimes of the electrodes were tested over a period of six months to investigate their stability. No significant change in the performance of the sol-gel electrode was observed over this period, but after two months the coated wire copper-selective electrode exhibited a gradual decrease in the slope. The selectivity of the sol-gel electrode was found to be better than that of the coated wire copper-selective electrode. Based on these results, a novel sol-gel copper-selective electrode is proposed for the determination of copper, and applied to real sample assays.

Sol-gel chemistry by ring-opening polymerization

DOE Office of Scientific and Technical Information (OSTI.GOV)

RAHIMIAN,KAMYAR; LOY,DOUGLAS A.

2000-02-07

Sol-gel processing of materials is plagued by shrinkage during polymerization of the alkoxide monomers and processing (aging and drying) of the resulting gels. The authors have developed a new class of hybrid organic-inorganic materials based on the solventless ring-opening polymerization (ROP) of monomers bearing the 2,2,5,5-tetramethyl-2,5-disilaoxacyclopentyl group, which permits them to drastically reduce shrinkage in sol-gel processed materials. Because the monomers are polymerized through a chain growth mechanism catalyzed by base rather than the step growth mechanism normally used in sol-gel systems, hydrolysis and condensation products are entirely eliminated. Furthermore, since water is not required for hydrolysis, an alcohol solventmore » is not necessary. Monomers with two disilaoxacyclopentyl groups, separated by a rigid phenylene group or a more flexible alkylene group, were prepared through disilylation of the corresponding diacetylenes, followed by ring closure and hydrogenation. Anionic polymerization of these materials, either neat or with 2,2,5,5-tetramethyl-2,5-disila-1-oxacyclopentane as a copolymer, affords thermally stable transparent gels with no visible shrinkage. These materials provide an easy route to the introduction of sol-gel type materials in encapsulation of microelectronics, which they have successfully demonstrated.« less

Preparation of long alumina fibers by sol-gel method using tartaric acid

NASA Astrophysics Data System (ADS)

Tan, Hong-Bin

2011-12-01

Long alumina fibers were prepared by sol-gel method. The spinning sol was obtained by mixing aluminum nitrate, tartaric acid, and polyvinylpyrrolidone with a mass ratio of 10:3:1.5. Thermogravimetry-differential scanning calorimetry (TG-DSC), Fourier transform infrared (FT-IR) spectra, X-ray diffraction (XRD), and scanning electron microscopy (SEM) were used to characterize the properties of the gel and ceramic fibers. A little of α-Al2O3 phase is observed in the alumina precursor gel fibers sintered at 1273 K. The fibers with a uniform diameter can be obtained when sintered at 1473 K, and its main phase is also indentified as α-Al2O3.

Athermal silicon optical add-drop multiplexers based on thermo-optic coefficient tuning of sol-gel material.

PubMed

Namnabat, Soha; Kim, Kyung-Jo; Jones, Adam; Himmelhuber, Roland; DeRose, Christopher T; Trotter, Douglas C; Starbuck, Andrew L; Pomerene, Andrew; Lentine, Anthony L; Norwood, Robert A

2017-09-04

Silicon photonics has gained interest for its potential to provide higher efficiency, bandwidth and reduced power consumption compared to electrical interconnects in datacenters and high performance computing environments. However, it is well known that silicon photonic devices suffer from temperature fluctuations due to silicon's high thermo-optic coefficient and therefore, temperature control in many applications is required. Here we present an athermal optical add-drop multiplexer fabricated from ring resonators. We used a sol-gel inorganic-organic hybrid material as an alternative to previously used materials such as polymers and titanium dioxide. In this work we studied the thermal curing parameters of the sol-gel and their effect on thermal wavelength shift of the rings. With this method, we were able to demonstrate a thermal shift down to -6.8 pm/°C for transverse electric (TE) polarization in ring resonators with waveguide widths of 325 nm when the sol-gel was cured at 130°C for 10.5 hours. We also achieved thermal shifts below 1 pm/°C for transverse magnetic (TM) polarization in the C band under different curing conditions. Curing time compared to curing temperature shows to be the most important factor to control sol-gel's thermo-optic value in order to obtain an athermal device in a wide temperature range.

Luminescent and scintillation properties of composites based on sol-gel SiO2 matrices and organic scintillators

NASA Astrophysics Data System (ADS)

Vyagin, O. G.; Bespalova, I. I.; Masalov, A. A.; Zelenskaya, O. V.; Tarasov, V. A.; Malyukin, Yu. V.

2014-11-01

Luminescent composites based on SiO2 matrices synthesized using the sol-gel method and organic scintillators PPO and o-POPOP are produced, and their optical, luminescent, and scintillation characteristics are studied. It is shown that these composites generate an intense photoluminescence signal, possess a nanosecond decay time, and have a transparency in the range of 400-700 nm of no less than 70%. The absolute light output during excitation by α radiation with an energy of 5.46 MeV is 4400-5100 photon/MeV, and the amplitude resolution is 27-32%.

Sol-Gel Application for Consolidating Stone: An Example of Project-Based Learning in a Physical Chemistry Lab

ERIC Educational Resources Information Center

de los Santos, Desiree´ M.; Montes, Antonio; Sa´nchez-Coronilla, Antonio; Navas, Javier

2014-01-01

A Project Based Learning (PBL) methodology was used in the practical laboratories of the Advanced Physical Chemistry department. The project type proposed simulates "real research" focusing on sol-gel synthesis and the application of the obtained sol as a stone consolidant. Students were divided into small groups (2 to 3 students) to…

Photocatalytic degradation of methylene blue dye by zinc oxide nanoparticles obtained from precipitation and sol-gel methods.

PubMed

Balcha, Abebe; Yadav, Om Prakash; Dey, Tania

2016-12-01

Zinc oxide (ZnO) nanoparticles were synthesized by precipitation and sol-gel methods. The aim of this study was to understand how different synthetic methods can affect the photocatalytic activity of ZnO nanoparticles. As-synthesized ZnO nanoparticles were characterized by X-ray diffraction (XRD) and UV-Visible spectroscopic techniques. XRD patterns of ZnO powders synthesized by precipitation and sol-gel methods revealed their hexagonal wurtzite structure with crystallite sizes of 30 and 28 nm, respectively. Their photocatalytic activities were evaluated by photocatalytic degradation of methylene blue, a common water pollutant, under UV radiation. The effects of operational parameters such as photocatalyst load and initial concentration of the dye on photocatalytic degradation of methylene blue were investigated. While the degradation of dye decreased over the studied dye concentration range of 20 to 100 mg/L, an optimum photocatalyst load of 250 mg/L was needed to achieve dye degradation as high as 81 and 92.5 % for ZnO prepared by precipitation and sol-gel methods, respectively. Assuming pseudo first-order reaction kinetics, this corresponded to rate constants of 8.4 × 10 -3 and 12.4 × 10 -3  min -1 , respectively. Hence, sol-gel method is preferred over precipitation method in order to achieve higher photocatalytic activity of ZnO nanostructures. Photocatalytic activity is further augmented by better choice of capping ligand for colloidal stabilization, starch being more effective than polyethylene glycol (PEG).

Macroporous ceramics by colloidal templating

NASA Astrophysics Data System (ADS)

Subramaniam, G.; Pine, David J.

2000-04-01

We describe a novel method of fabricating macroporous ceramics employing colloidal dispersion of ultrafine ceramic particles with latex particles as the templates. The colloidal particles form a particulate gel on drying and fill the voids of the ordered latex templates. Subsequent removal of the template by calcination results in the formation of an ordered macroporous ceramic. The process has significant advantages over the traditional sol-gel process employing alkoxide precursors. Most importantly, the much lower shrinkage compared to the sol-gel process enabled us to produce larger pieces of the sample. The larger shrinkage involved in the sol-gel process often results in small and fragile pieces of the macroporous material which has to be subsequently heat treated to induce crystallization. The ability to choose crystalline colloidal particles in our method obviates the need for heat treatment to achieve crystallinity. We have synthesized a variety of materials such as macroporous silica, titania, alumina and recently have also extended the approach to macroporous silicon which is not amenable to the sol-gel process.

Sol-gel deposition of buffer layers on biaxially textured metal substances

DOEpatents

Shoup, Shara S.; Paranthamam, Mariappan; Beach, David B.; Kroeger, Donald M.; Goyal, Amit

2000-01-01

A method is disclosed for forming a biaxially textured buffer layer on a biaxially oriented metal substrate by using a sol-gel coating technique followed by pyrolyzing/annealing in a reducing atmosphere. This method is advantageous for providing substrates for depositing electronically active materials thereon.

STUDY ON SYNTHESIS AND EVOLUTION OF NANOCRYSTALLINE Mg4Ta2O9 BY AQUEOUS SOL-GEL PROCESS

NASA Astrophysics Data System (ADS)

Wu, H. T.; Yang, C. H.; Wu, W. B.; Yue, Y. L.

2012-06-01

Nanosized and highly reactive Mg4Ta2O9 were successfully synthesized by aqueous sol-gel method compared with conventional solid-state method. Ta-Mg-citric acid solution was first formed and then evaporated resulting in a dry gel for calcination in the temperature ranging from 600°C to 800°C for crystallization in oxygen atmosphere. The crystallization process from the gel to crystalline Mg4Ta2O9 was identified by thermal analysis and phase evolution of powders was studied using X-ray diffraction (XRD) technique during calcinations. Particle size and morphology were examined by transmission electron microscopy (TEM) and high resolution scanning electron microscopy (HR-SEM). The results revealed that sol-gel process showed great advantages over conventional solid-state method and Mg4Ta2O9 nanopowders with the size of 20-30 nm were obtained at 800°C.

Preparation of Flame Retardant Polyacrylonitrile Fabric Based on Sol-Gel and Layer-by-Layer Assembly

PubMed Central

Ren, Yuanlin; Huo, Tongguo; Qin, Yiwen; Liu, Xiaohui

2018-01-01

This paper aims to develop a novel method, i.e., sol-gel combined with layer-by-layer assembly technology, to impart flame retardancy on polyacrylonitrile (PAN) fabrics. Silica-sol was synthesized via the sol-gel process and acted as cationic solution, and phytic acid (PA) was used as the anionic medium. Flame-retardant-treated PAN fabric (FR-PAN) could achieve excellent flame retardancy with 10 bilayer (10BL) coating through layer-by-layer assembly. The structure of the fabrics was characterized by X-ray photoelectron spectroscopy (XPS) and Fourier transform infrared spectroscopy (FTIR). The thermal stability and flame retardancy were evaluated by thermogravimetric (TG) analysis, cone calorimetry (CC) and limiting oxygen index (LOI). The LOI value of the coated fabric was up to 33.2 vol % and the char residue at 800 °C also increased to 57 wt %. Cone calorimetry tests revealed that, compared to the control fabric, the peak of heat release rate (PHRR) and total heat release (THR) of FR-PAN decreased by 66% and 73%, respectively. These results indicated that sol-gel combined with layer-by-layer assembly technique could impart PAN fabric with satisfactory flame-retardant properties, showing an efficient flame retardant strategy for PAN fabric. PMID:29570646

Preparation of Flame Retardant Polyacrylonitrile Fabric Based on Sol-Gel and Layer-by-Layer Assembly.

PubMed

Ren, Yuanlin; Huo, Tongguo; Qin, Yiwen; Liu, Xiaohui

2018-03-23

This paper aims to develop a novel method, i.e., sol-gel combined with layer-by-layer assembly technology, to impart flame retardancy on polyacrylonitrile (PAN) fabrics. Silica-sol was synthesized via the sol-gel process and acted as cationic solution, and phytic acid (PA) was used as the anionic medium. Flame-retardant-treated PAN fabric (FR-PAN) could achieve excellent flame retardancy with 10 bilayer (10BL) coating through layer-by-layer assembly. The structure of the fabrics was characterized by X-ray photoelectron spectroscopy (XPS) and Fourier transform infrared spectroscopy (FTIR). The thermal stability and flame retardancy were evaluated by thermogravimetric (TG) analysis, cone calorimetry (CC) and limiting oxygen index (LOI). The LOI value of the coated fabric was up to 33.2 vol % and the char residue at 800 °C also increased to 57 wt %. Cone calorimetry tests revealed that, compared to the control fabric, the peak of heat release rate (PHRR) and total heat release (THR) of FR-PAN decreased by 66% and 73%, respectively. These results indicated that sol-gel combined with layer-by-layer assembly technique could impart PAN fabric with satisfactory flame-retardant properties, showing an efficient flame retardant strategy for PAN fabric.

Graphene oxide-enhanced sol-gel transition sensitivity and drug release performance of an amphiphilic copolymer-based nanocomposite

PubMed Central

Hu, Huawen; Wang, Xiaowen; Lee, Ka I; Ma, Kaikai; Hu, Hong; Xin, John H.

2016-01-01

We report the fabrication of a highly sensitive amphiphilic copolymer-based nanocomposite incorporating with graphene oxide (GO), which exhibited a low-intensity UV light-triggered sol-gel transition. Non-cytotoxicity was observed for the composite gels after the GO incorporation. Of particular interest were the microchannels that were formed spontaneously within the GO-incorporated UV-gel, which expedited sustained drug release. Therefore, the present highly UV-sensitive, non-cytotoxic amphiphilic copolymer-based composites is expected to provide enhanced photothermal therapy and chemotherapy by means of GO’s unique photothermal properties, as well as through efficient passive targeting resulting from the sol-gel transition characteristic of the copolymer-based system with improved sensitivity, which thus promises the enhanced treatment of patients with cancer and other diseases. PMID:27539298

Photonic devices on planar and curved substrates and methods for fabrication thereof

DOEpatents

Bartl, Michael H.; Barhoum, Moussa; Riassetto, David

2016-08-02

A versatile and rapid sol-gel technique for the fabrication of high quality one-dimensional photonic bandgap materials. For example, silica/titania multi-layer materials may be fabricated by a sol-gel chemistry route combined with dip-coating onto planar or curved substrate. A shock-cooling step immediately following the thin film heat-treatment process is introduced. This step was found important in the prevention of film crack formation--especially in silica/titania alternating stack materials with a high number of layers. The versatility of this sol-gel method is demonstrated by the fabrication of various Bragg stack-type materials with fine-tuned optical properties by tailoring the number and sequence of alternating layers, the film thickness and the effective refractive index of the deposited thin films. Measured optical properties show good agreement with theoretical simulations confirming the high quality of these sol-gel fabricated optical materials.

Chitosan-doped-hybrid/TiO2 nanocomposite based sol-gel coating for the corrosion resistance of aluminum metal in 3.5% NaCl medium.

PubMed

J, Balaji; M G, Sethuraman

2017-11-01

The study outlines the role of chitosan, a biopolymer on corrosion behavior of Hy/nano-TiO 2 based sol-gel coating over aluminum metal. In this study organic-inorganic hybrid sols were synthesized through hydrolysis and condensation of 3-glycidoxypropyltrimethoxy silane (GPTMS), tetraethoxysilane (TEOS) and titanium (IV) isopropoxide (TIP) in acidic solution. Chitosan was doped into sol-gel matrix and self-assembled over aluminum substrate. The resultant chitosan-doped-Hy/nano-TiO 2 sol-gel coating was characterized by Fourier Transform Infrared (FT-IR) spectra, Raman spectroscopy, X-ray photoelectron spectroscopy (XPS), Scanning Electron Microscopy (SEM), Atomic Force Microscopy (AFM) and Energy-Dispersive X-ray Spectroscopy (EDX) analyses. The as-tailored aluminum substrate was evaluated for corrosion resistance in neutral medium. The protection ability of these coatings was evaluated by electrochemical impedance studies (EIS) and potentiodynamic polarization (PP) measurements in 3.5% NaCl medium. The EIS and PP results showed that chitosan-doped- Hy/nano-TiO 2 sol-gel coating exhibited better protection from corrosion than the undoped Hy/TiO 2 nanocomposite coating. Copyright © 2017 Elsevier B.V. All rights reserved.

Sol-Gel Matrices For Direct Colorimetric Detection Of Analytes

DOEpatents

Charych, Deborah H.; Sasaki, Darryl; Yamanaka, Stacey

2002-11-26

The present invention relates to methods and compositions for the direct detection of analytes using color changes that occur in immobilized biopolymeric material in response to selective binding of analytes to their surface. In particular, the present invention provides methods and compositions related to the encapsulation of biopolymeric material into metal oxide glass using the sol-gel method.

Sol-gel matrices for direct colorimetric detection of analytes

DOEpatents

Charych, Deborah H.; Sasaki, Darryl; Yamanaka, Stacey

2000-01-01

The present invention relates to methods and compositions for the direct detection of analytes using color changes that occur in immobilized biopolymeric material in response to selective binding of analytes to their surface. In particular, the present invention provides methods and compositions related to the encapsulation of biopolymeric material into metal oxide glass using the sol-gel method.

Vibrational spectroscopic studies of (3-mercaptopropyl)trimethoxylsilane sol-gel and its coating.

PubMed

Li, Ying-Sing; Wang, Yu; Tran, Tuan; Perkins, Anshion

2005-10-01

Organosilane sol-gels have been prepared under different conditions from mercaptopropyltrimethoxysilane (MPTMS) and mercaptopropyltriethoxysilane (MPTES). These sol-gels were applied for the thin film coating on aluminum. Vibrational spectroscopy has been employed to trace and to study the proceeding of the sol-gel formation and the curing of the coated films on Al. Based on the group frequencies as well as their spectral behavior under different conditions, vibrational assignments have been made for most of the observed bands. Surface enhanced Raman scattering has revealed the chemical adsorption of MPTMS sol-gel on silver particles. Recorded reflection and absorption infrared (RAIR) spectra of coated tiles cured at different temperatures have indicated that surface reaction may occur at high temperature. The anticorrosion characters of the coated metals have been evaluated with the measured electrochemical data. Results from cyclic voltammographs have indicated that each layer of sol-gel coating would reduce the redox current across the electrode/electrolyte solution interface. Tafel plots have shown that the anodic current of the coated electrode decreases significantly and the corrosion potentials shift to the positive side.

Enhancement of Ce/Cr Codopant Solubility and Chemical Homogeneity in TiO2 Nanoparticles through Sol-Gel versus Pechini Syntheses.

PubMed

Chen, Wen-Fan; Mofarah, Sajjad S; Hanaor, Dorian Amir Henry; Koshy, Pramod; Chen, Hsin-Kai; Jiang, Yue; Sorrell, Charles Christopher

2018-06-18

Ce/Cr codoped TiO 2 nanoparticles were synthesized using sol-gel and Pechini methods with heat treatment at 400 °C for 4 h. A conventional sol-gel process produced well-crystallized anatase, while Pechini synthesis yielded less-ordered mixed-phase anatase + rutile; this suggests that the latter method enhances Ce solubility and increases chemical homogeneity but destabilizes the TiO 2 lattice. Greater structural disruption from the decomposition of the Pechini precursor formed more open agglomerated morphologies, while the lower levels of structural disruption from pyrolysis of the dried sol-gel precursor resulted in denser agglomerates of lower surface areas. Codoping and associated destabilization of the lattice reduced the binding energies in both powders. Cr 4+ formation in sol-gel powders and Cr 6+ formation in Pechini powders suggest that these valence changes derive from synergistic electron exchange from intervalence and/or multivalence charge transfer. Since Ce is too large to allow either substitutional or interstitial solid solubility, the concept of integrated solubility is introduced, in which the Ti site and an adjacent interstice are occupied by the large Ce ion. The photocatalytic performance data show that codoping was detrimental owing to the effects of reduced crystallinity from lattice destabilization and surface area. Two regimes of mechanistic behavior are seen, which are attributed to the unsaturated solid solutions at lower codopant levels and supersaturated solid solutions at higher levels. The present work demonstrates that the Pechini method offers a processing technique that is superior to sol-gel because the former facilitates solid solubility and consequent chemical homogeneity.

Holographic sol-gel monoliths: optical properties and application for humidity sensing

NASA Astrophysics Data System (ADS)

Ilatovskii, Daniil A.; Milichko, Valentin; Vinogradov, Alexander V.; Vinogradov, Vladimir V.

2018-05-01

Sol-gel monoliths based on SiO2, TiO2 and ZrO2 with holographic colourful diffraction on their surfaces were obtained via a sol-gel synthesis and soft lithography combined method. The production was carried out without any additional equipment at near room temperature and atmospheric pressure. The accurately replicated wavy structure with nanoscale size of material particles yields holographic effect and its visibility strongly depends on refractive index (RI) of materials. Addition of multi-walled carbon nanotubes (MWCNTs) in systems increases their RI and lends absorbing properties due to extremely high light absorption constant. Further prospective and intriguing applications based on the most successful samples, MWCNTs-doped titania, were investigated as reversible optical humidity sensor. Owing to such property as reversible resuspension of TiO2 nanoparticles while interacting with water, it was proved that holographic xerogels can repeatedly act as humidity sensors. Materials which can be applied as humidity sensors in dependence on holographic response were discovered for the first time.

Low Concentration Fe-Doped Alumina Catalysts Using Sol-Gel and Impregnation Methods: The Synthesis, Characterization and Catalytic Performance during the Combustion of Trichloroethylene.

PubMed

Maldonado, Carolina Solis; De la Rosa, Javier Rivera; Lucio-Ortiz, Carlos J; Hernández-Ramírez, Aracely; Barraza, Felipe F Castillón; Valente, Jaime S

2014-03-12

The role of iron in two modes of integration into alumina catalysts was studied at 0.39 wt% Fe and tested in trichloroethylene combustion. One modified alumina was synthesized using the sol-gel method with Fe added in situ during hydrolysis; another modification was performed using calcined alumina, prepared using the sol-gel method and impregnated with Fe. Several characterization techniques were used to study the level of Fe modification in the γ-Al₂O₃ phase formed and to correlate the catalytic properties during trichloroethylene (TCE) combustion. The introduction of Fe in situ during the sol-gel process influenced the crystallite size, and three iron species were generated, namely, magnetite, maghemite and hematite. The impregnated Fe-alumina formed hematite and maghemite, which were highly dispersed on the γ-Al₂O 3 surface. The X-ray photoelectron spectra (XPS), FT-IR and Mössbauer spectroscopy analyses revealed how Fe interacted with the γ-Al₂O₃ lattice in both catalysts. The impregnated Fe-catalyst showed the best catalytic performance compared to the catalyst that was Fe-doped in situ by the sol-gel method; both had better catalytic activity than pure alumina. This difference in activity was correlated with the accessibility of the reactants to the hematite iron species on the surface. The chlorine poisoning for all three catalysts was less than 1.8%.

Robust aptamer sol-gel solid phase microextraction of very polar adenosine from human plasma.

PubMed

Mu, Li; Hu, Xiangang; Wen, Jianping; Zhou, Qixing

2013-03-01

Conventional solid phase microextraction (SPME) has a limited capacity to extract very polar analytes, such as adenosine. To solve this problem, aptamer conjugating sol-gel methodology was coupled with an SPME fiber. According to the authors' knowledge, this is the first reported use of aptamer SPME. The fiber of aptamer sol-gel SPME with a mesoporous structure has high porosity, large surface area, and small water contact angle. Rather than employing direct entrapment, covalent immobilization was the dominant method of aptamer loading in sol-gel. Aptamer sol-gel fiber captured a specified analyte from among the analog molecules, thereby, exhibiting an excellent selective property. Compared with commercial SPME fibers, this aptamer fiber was suitable for extracting adenosine, presenting an extraction efficiency higher than 20-fold. The values of repeatability and reproducibility expressed by relative standard deviation were low (9.4%). Interestingly, the sol-gel network enhanced the resistance of aptamer SPME to both nuclease and nonspecific proteins. Furthermore, the aptamer sol-gel fiber was applied in human plasma with LOQ 1.5 μg/L, which is an acceptable level. This fiber also demonstrates durability and regeneration over 20-cycles without significant loss of efficiency. Given the various targets (from metal ions to biomacromolecules and cells) of aptamers, this methodology will extend the multi-domain applications of SPME. Copyright © 2013 Elsevier B.V. All rights reserved.

Preparation and characterization of conductive and transparent ruthenium dioxide sol-gel films.

PubMed

Allhusen, John S; Conboy, John C

2013-11-27

RuO2 conductive thin films were synthesized using the sol-gel method and deposited onto transparent insulating substrates. The optical transmission, film thickness, surface morphology and composition, resistivity, and spectroelectrochemical performance have been characterized. The optical transmission values of these films ranged from 70 to 89% in the visible region and from 56 to 88% in the infrared region. Resistivity values of the RuO2 sol-gel films varied from 1.02 × 10(-3) to 1.13 Ω cm and are highly dependent on the initial solution concentration of RuO2 in the sol-gel. The RuO2 sol-gel films were used as electrodes for the electrochemical oxidation and reduction of ferrocenemethanol. The electrochemical behavior of our novel RuO2 sol-gel films was compared to that of a standard platinum disk electrode and showed no appreciable differences in the half-wave potential (E1/2). The mechanical and chemical stability of the coatings was tested by physical abrasion and exposure to highly acidic, oxidizing Piranha solution. Repeated exposure to these extreme conditions did not result in any appreciable decline in electrochemical performance. Finally, the use of the novel RuO2 sol-gel conductive and transparent films was demonstrated in a spectroelectrochemistry experiment in which the oxidation and reduction of ferrocenemethanol was monitored via UV-vis spectroscopy as the applied potential was cycled.

Study on the Effect of Various Sol-Gel Concentration to the Electrical, Structural and Optical Properties of the Nanostructured Titanium Dioxide Thin Films

NASA Astrophysics Data System (ADS)

Ahmad, M. K.; Rusop, M.

2009-06-01

Nanostructured Titanium Dioxide (TiO2) thin film with various sol-gel concentration has been successfully prepared using sol-gel spin coating method. The sol-gel concentration of nanostructured TiO2 thin films are varied at 0.1 M, 0.2 M, 0.3 M and 0.4 M, respectively. The effects of different sol-gel concentration of nanostructured TiO2 thin film structural, electrical and optical properties have been studied. The effects of these properties were characterized using X-Ray Diffractometer (XRD), 2-point probe I-V measurement and UV-Vis-NIR Spectrophotometer. For electrical properties, 0.2 M of sol-gel concentration gives the lowest sheet resistance among other concentrated sol-gels. As for structural properties, 0.1 M of concentration gives very weak peak, and continues stronger as in comes to 0.2 M until 0.4 M. It is due to amount of solute (i.e Titanium Isopropoxide) increases in the solution and therefore the intensity of (101) planes become higher. The optical transmission in the visible region (450-1000 nm) for 0.1 M and 0.2 M are the highest (>80%), indicating that the films are transparent in the visible region. The transmission decreases sharply near the ultraviolet region due to the band gap absorption.

Amoeba-like self-oscillating polymeric fluids with autonomous sol-gel transition

PubMed Central

Onoda, Michika; Ueki, Takeshi; Tamate, Ryota; Shibayama, Mitsuhiro; Yoshida, Ryo

2017-01-01

In the field of polymer science, many kinds of polymeric material systems that show a sol-gel transition have been created. However, most systems are unidirectional stimuli-responsive systems that require physical signals such as a change in temperature. Here, we report on the design of a block copolymer solution that undergoes autonomous and periodic sol-gel transition under constant conditions without any on–off switching through external stimuli. The amplitude of this self-oscillation of the viscosity is about 2,000 mPa s. We also demonstrate an intermittent forward motion of a droplet of the polymer solution synchronized with the autonomous sol-gel transition. This polymer solution bears the potential to become the base for a type of slime-like soft robot that can transform its shape kaleidoscopically and move autonomously, which is associated with the living amoeba that moves forward by a repeated sol-gel transition. PMID:28703123

Amoeba-like self-oscillating polymeric fluids with autonomous sol-gel transition

NASA Astrophysics Data System (ADS)

Onoda, Michika; Ueki, Takeshi; Tamate, Ryota; Shibayama, Mitsuhiro; Yoshida, Ryo

2017-07-01

In the field of polymer science, many kinds of polymeric material systems that show a sol-gel transition have been created. However, most systems are unidirectional stimuli-responsive systems that require physical signals such as a change in temperature. Here, we report on the design of a block copolymer solution that undergoes autonomous and periodic sol-gel transition under constant conditions without any on-off switching through external stimuli. The amplitude of this self-oscillation of the viscosity is about 2,000 mPa s. We also demonstrate an intermittent forward motion of a droplet of the polymer solution synchronized with the autonomous sol-gel transition. This polymer solution bears the potential to become the base for a type of slime-like soft robot that can transform its shape kaleidoscopically and move autonomously, which is associated with the living amoeba that moves forward by a repeated sol-gel transition.

Optical pH detector based on LTCC and sol-gel technologies

NASA Astrophysics Data System (ADS)

Tadaszak, R. J.; Łukowiak, A.; Golonka, L. J.

2013-01-01

This paper presents an investigation on using sol-gel thin film as a material for sensors application in LTCC (Low Temperature Co-fired Ceramics) technology. This material gives the opportunity to make new, low-cost highly integrated optoelectronic devices. Sensors with optical detection are a significant part of these applications. They can be used for quick and safe diagnostics of some parameters. Authors present a pH detector with the optical detection system made of the LTCC material. The main part of the device is a flow channel with the chamber and sol-gel active material. The silica sol-gel with bromocresol green indicator was used. As the absorbance of sol-gel layer changes with the pH value of a measured medium, the transmitted light power was measured. The pH detector was integrated with the electronic components on the LTCC substrate.

Solid-phase microfibers based on polyethylene glycol modified single-walled carbon nanotubes for the determination of chlorinated organic carriers in textiles.

PubMed

Zhang, Wei-Ya; Sun, Yin; Wang, Cheng-Ming; Wu, Cai-Ying

2011-09-01

Based on polyethylene glycol modified single-walled carbon nanotubes, a novel sol-gel fiber coating was prepared and applied to the headspace microextraction of chlorinated organic carriers (COCs) in textiles by gas chromatography-electron capture detection. The preparation of polyethylene glycol modified single-walled carbon nanotubes and the sol-gel fiber coating process was stated and confirmed by infrared spectra, Raman spectroscopy, and scanning electron microscopy. Several parameters affecting headspace microextraction, including extraction temperature, extraction time, salting-out effect, and desorption time, were optimized by detecting 11 COCs in simulative sweat samples. Compared with the commercial solid-phase microextraction fibers, the sol-gel polyethylene glycol modified single-walled carbon nanotubes fiber showed higher extraction efficiency, better thermal stability, and longer life span. The method detection limits for COCs were in the range from 0.02 to 7.5 ng L(-1) (S/N = 3). The linearity of the developed method varied from 0.001 to 50 μg L(-1) for all analytes, with coefficients of correlation greater than 0.974. The developed method was successfully applied to the analysis of trace COCs in textiles, the recoveries of the analytes indicated that the developed method was considerably useful for the determination of COCs in ecological textile samples.

Microwave-Assisted Synthesis of High Dielectric Constant CaCu3Ti4O12 from Sol-Gel Precursor

NASA Astrophysics Data System (ADS)

Ouyang, Xin; Cao, Peng; Huang, Saifang; Zhang, Weijun; Huang, Zhaohui; Gao, Wei

2015-07-01

CaCu3Ti4O12 (CCTO) powders derived from sol-gel precursors were calcined and sintered via microwave radiation. The obtained CCTO powders were compared with that obtained via a conventional heating method. For microwave heating, 89.1 wt.% CCTO was achieved from the sol-gel precursor, after only 17 min at 950°C. In contrast, the conventional calcination method required 3 h to generate 87.6 wt.% CCTO content at 1100°C. In addition, the CCTO powders prepared through 17 min of microwave calcination exhibited a small particle size distribution of D50 = 3.826 μm. It was found that a lengthy hold time of 1 h by microwave sintering is required to obtain a high dielectric constant (3.14 × 103 at 102 Hz) and a reasonably low dielectric loss (0.161) in the sintered CCTO ceramic. Based upon the distinct microstructures, the dielectric responses of the CCTO samples sintered by different methods are attributed to space charge polarization and internal barrier layer capacitor mechanism.

A review of photocatalysts prepared by sol-gel method for VOCs removal.

PubMed

Tseng, Ting Ke; Lin, Yi Shing; Chen, Yi Ju; Chu, Hsin

2010-05-28

The sol-gel process is a wet-chemical technique (chemical solution deposition), which has been widely used in the fields of materials science, ceramic engineering, and especially in the preparation of photocatalysts. Volatile organic compounds (VOCs) are prevalent components of indoor air pollution. Among the approaches to remove VOCs from indoor air, photocatalytic oxidation (PCO) is regarded as a promising method. This paper is a review of the status of research on the sol-gel method for photocatalyst preparation and for the PCO purification of VOCs. The review and discussion will focus on the preparation and coating of various photocatalysts, operational parameters, and will provide an overview of general PCO models described in the literature.

The thickness correction of sol-gel coating using ion-beam etching in the preparation of antireflection coating

NASA Astrophysics Data System (ADS)

Dong, Siyu; Xie, Lingyun; He, Tao; Jiao, Hongfei; Bao, Ganghua; Zhang, Jinlong; Wang, Zhanshan; Cheng, Xinbin

2017-09-01

For the sol-gel method, it is still challenging to achieve excellent spectral performance when preparing antireflection (AR) coating by this way. The difficulty lies in controlling the film thickness accurately. To correct the thickness error of sol-gel coating, a hybrid approach that combined conventional sol-gel process with ion-beam etching technology was proposed in this work. The etching rate was carefully adjusted and calibrated to a relatively low value for removing the redundant material. Using atomic force microscope (AFM), it has been demonstrated that film surface morphology will not be changed in this process. After correcting the thickness error, an AR coating working at 1064 nm was prepared with transmittance higher than 99.5%.

Systematic study of inorganic functionalization of ZnO nanorods by Sol-Gel method

NASA Astrophysics Data System (ADS)

Gamarra, J. K.; Solano, C.; Piñeres, I.; Gómez, H.; Mass, J.; Montenegro, D. N.

2017-01-01

A systematic study of the inorganic surface functionalization of ZnO nanostructures by sol-gel method is shown. We have emphasized on the evolution of morphology properties of samples as a function of functionalization parameters. In addition, the effects on thermal stability and some optical properties of samples are discussed.

Nanostructured aluminium titanate (Al{sub 2}TiO{sub 5}) particles and nanofibers: Synthesis and mechanism of microstructural evolution

DOE Office of Scientific and Technical Information (OSTI.GOV)

Azarniya, Abolfazl, E-mail: abolfazl_azarniya@mehr.sharif.ir; Azarniya, Amir, E-mail: a.azarnia91@gmail.com; Hosseini, Hamid Reza Madaah, E-mail: madaah@sharif.ir

In this study, aluminium titanate (AT) particles and nanofibers were synthesized through citrate sol gel and sol gel-assisted electrospinning methods in both nanostructured powder and nanofiber forms. The results of X-ray diffraction analysis, field-emission scanning electron microscopy and differential thermal analysis showed that the synthetic products benefit a nanostructured nature with a grain size less than 70 nm. The optimal values for time and temperature at which a roughly pure AT is attained were determined as 2 h and 900 °C, respectively. It was found that the sol gel precursor bears an amorphous structure till 700 °C and begins tomore » be crystallized to alumina, anatase and AT at higher temperatures. Moreover, AT tends to decompose into rutile and alumina at temperatures higher than 900 °C and its degradation rate reaches a maximum at temperatures near to 1100 °C. In this synthesis, citric acid was used as a chelating agent for Al{sup 3} {sup +} and Ti{sup 4} {sup +} ions and it was shown that a low citric acid-to-metal cation ratio leads to larger numbers of nuclei during crystallization and smaller grain size. Finally, a model was suggested to describe the microstructural evolution of AT compound based on a nucleation and growth regime. - Graphical abstract: Display Omitted - Highlights: • We synthesized aluminium titanate ceramic in both powder and nanofiber forms. • The methods in use were citrate sol gel and sol gel-assisted electrospinning. • Powders and nanofibers bear a nanostructured nature with a grain size less than 70 nm. • A model is suggested to describe microstructural evolution of synthetic products.« less

Innovative Sol-Gel Routes for the Bottom-up Preparation of Heterogeneous Catalysts.

PubMed

Debecker, Damien P

2017-12-11

Heterogeneous catalysts can be prepared by different methods offering various levels of control on the final properties of the solid. In this account, we exemplify bottom-up preparation routes that are based on the sol-gel chemistry and allow to tailor some decisive properties of solid catalysts. First, an emulsion templating strategy is shown to lead to macrocellular self-standing monoliths with a macroscopic 3D structure. The latter can be used as catalyst or catalyst supports in flow chemistry, without requiring any subsequent shaping step. Second, the aerosol-assisted sol-gel process allows for the one-step and continuous production of porous mixed oxides. Tailored textural properties can be obtained together with an excellent control on composition and homogeneity. Third, the application of non-hydrolytic sol-gel routes, in the absence of water, leads to mixed oxides with outstanding textural properties and with peculiar surface chemistry. In all cases, the resulting catalytic performance can be correlated with the specificities of the preparation routes presented. This is exemplified in catalytic reactions in the fields of biomass conversion, petro chemistry, enantioselective organic synthesis, and air pollution mitigation. © 2017 The Chemical Society of Japan & Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

A Sol-gel Integrated Dual-readout Microarray Platform for Quantification and Identification of Prostate-specific Antigen.

PubMed

Lee, SangWook; Lee, Jong Hyun; Kwon, Hyuck Gi; Laurell, Thomas; Jeong, Ok Chan; Kim, Soyoun

2018-01-01

Here, we report a sol-gel integrated affinity microarray for on-chip matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOF-MS) that enables capture and identification of prostate?specific antigen (PSA) in samples. An anti-PSA antibody (H117) was mixed with a sol?gel, and the mixture was spotted onto a porous silicon (pSi) surface without additional surface modifications. The antibody easily penetrates the sol-gel macropore fluidic network structure, making possible high affinities. To assess the capture affinity of the platform, we performed a direct assay using fluorescein isothiocyanate-labeled PSA. Pure PSA was subjected to on-chip MALDI-TOF-MS analysis, yielding three clear mass peptide peaks (m/z = 1272, 1407, and 1872). The sol-gel microarray platform enables dual readout of PSA both fluorometric and MALDI-TOF MS analysis in biological samples. Here we report a useful method for a means for discovery of biomarkers in complex body fluids.

A Urea Biosensor from Stacked Sol-Gel Films with Immobilized Nile Blue Chromoionophore and Urease Enzyme

PubMed Central

Alqasaimeh, Muawia Salameh; Heng, Lee Yook; Ahmad, Musa

2007-01-01

An optical urea biosensor was fabricated by stacking several layers of sol-gel films. The stacking of the sol-gel films allowed the immobilization of a Nile Blue chromoionophore (ETH 5294) and urease enzyme separately without the need of any chemical attachment procedure. The absorbance response of the biosensor was monitored at 550 nm, i.e. the deprotonation of the chromoionophore. This multi-layer sol-gel film format enabled higher enzyme loading in the biosensor to be achieved. The urea optical biosensor constructed from three layers of sol-gel films that contained urease demonstrated a much wider linear response range of up to 100 mM urea when compared with biosensors that constructed from 1-2 layers of films. Analysis of urea in urine samples with this optical urea biosensor yielded results similar to that determined by a spectrophotometric method using the reagent p-dimethylaminobenzaldehyde (R2 = 0.982, n = 6). The average recovery of urea from urine samples using this urea biosensor is approximately 103%.

Sol gel method for synthesis of semiconducting ferrite and the study of FTIR, DTA, SEM and CV

NASA Astrophysics Data System (ADS)

Alva, Sagir; Hua, Tang Ing; Kalmar Nizar, Umar; Wahyudi, Haris; Sundari, Rita

2018-03-01

In this study, a sol gel method using citric acid as anionic surfactant is used for synthesis of magnesium ferrite. Calcinations of magnesium ferrite at temperature (300°C, 600°C and 800°C) have been conducted after sol gel process. Characterization study of the prepared magnesium ferrite related to calcinations using Fourier transform infrared spectrometry (FTIR), Differential thermogravic analysis (DTA), and Scanning electron microscope (SEM) has been discussed. The study of Cyclic voltammetry (CV) of the prepared magnesium ferrite has been examined to assay the semiconducting behavior of magnesium ferrite in relation to its electrochemical behavior.

Neutron detector using sol-gel absorber

DOEpatents

Hiller, John M.; Wallace, Steven A.; Dai, Sheng

1999-01-01

An neutron detector composed of fissionable material having ions of lithium, uranium, thorium, plutonium, or neptunium, contained within a glass film fabricated using a sol-gel method combined with a particle detector is disclosed. When the glass film is bombarded with neutrons, the fissionable material emits fission particles and electrons. Prompt emitting activated elements yielding a high energy electron contained within a sol-gel glass film in combination with a particle detector is also disclosed. The emissions resulting from neutron bombardment can then be detected using standard UV and particle detection methods well known in the art, such as microchannel plates, channeltrons, and silicon avalanche photodiodes.

Sol-Gel Synthesis and Crystallization of Magnesium and Calcium Rich Silicate Dust Analogs

NASA Astrophysics Data System (ADS)

Gillot, J.; Roskosz, M.; Depecker, C.; Roussel, P.; Leroux, H.

2009-03-01

A new sol-gel method optimized to synthesize amorphous and porous silicate dust analogs is proposed. The crystallization of such analogs is metastable and polyphasic. Their high reactivity is probably due to high surface/volume ratio.

Chemistry of surface nanostructures in lead precursor-rich PbZr0.52Ti0.48O3 sol-gel films

NASA Astrophysics Data System (ADS)

Gueye, I.; Le Rhun, G.; Gergaud, P.; Renault, O.; Defay, E.; Barrett, N.

2016-02-01

We present a study of the chemistry of the nanostructured phase at the surface of lead zirconium titanate PbZr0.52Ti0.48O3 (PZT) films synthesized by sol-gel method. In sol-gel synthesis, excess lead precursor is used to maintain the target stoichiometry. Surface nanostructures appear at 10% excess whereas 30% excess inhibits their formation. Using the surface-sensitive, quantitative X-ray photoelectron spectroscopy and glancing angle X-ray diffraction we have shown that the chemical composition of the nanostructures is ZrO1.82-1.89 rather than pyrochlore often described in the literature. The presence of a possibly discontinuous layer of wide band gap ZrO1.82-1.89 could be of importance in determining the electrical properties of PZT-based metal-insulator-metal heterostructures.

Sol-gel niobia sorbent with a positively charged octadecyl ligand providing enhanced enrichment of nucleotides and organophosphorus pesticides in capillary microextraction for online HPLC analysis.

PubMed

Kesani, Sheshanka; Malik, Abdul

2018-04-01

A niobia-based sol-gel organic-inorganic hybrid sorbent carrying a positively charged C 18 ligand (Nb 2 O 5 -C 18 (+ve)) was synthesized to achieve enhanced enrichment capability in capillary microextraction of organophosphorus compounds (which include organophosphorus pesticides and nucleotides) before their online analysis by high-performance liquid chromatography. The sorbent was designed to simultaneously provide three different types of molecular level interactions: electrostatic, Lewis acid-base, and van der Waals interactions. To understand relative contributions of various molecular level analyte-sorbent interactions in the extraction process, two other sol-gel niobia sorbents were also created: (a) a purely inorganic sol-gel niobia sorbent (Nb 2 O 5 ) and (b) an organic-inorganic hybrid sol-gel niobia sorbent carrying an electrically neutral-bonded octadecyl ligand (Nb 2 O 5 -C 18 ). The extraction efficiency of the created sol-gel niobia sorbent (Nb 2 O 5 -C 18 (+ve)) was compared with that of analogously designed and synthesized titania-based sol-gel sorbent (TiO 2 -C 18 (+ve)), taking into consideration that titania-based sorbents present state-of-the-art extraction media for organophosphorus compounds. In capillary microextraction with high-performance liquid chromatography analysis, Nb 2 O 5 -C 18 (+ve) had shown 40-50% higher specific extraction values (a measure of extraction efficiency) over that of TiO 2 -C 18 (+ve). Compared to TiO 2 -C 18 (+ve), Nb 2 O 5 -C 18 (+ve) also provided superior analyte desorption efficiency (96 vs. 90%) during the online release of the extracted organophosphorus pesticides from the sorbent coating in the capillary microextraction capillary to the chromatographic column using reversed-phase high-performance liquid chromatography mobile phase. © 2017 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Process for preparing energetic materials

DOEpatents

Simpson, Randall L [Livermore, CA; Lee, Ronald S [Livermore, CA; Tillotson, Thomas M [Tracy, CA; Hrubesh, Lawrence W [Pleasanton, CA; Swansiger, Rosalind W [Livermore, CA; Fox, Glenn A [Livermore, CA

2011-12-13

Sol-gel chemistry is used for the preparation of energetic materials (explosives, propellants and pyrotechnics) with improved homogeneity, and/or which can be cast to near-net shape, and/or made into precision molding powders. The sol-gel method is a synthetic chemical process where reactive monomers are mixed into a solution, polymerization occurs leading to a highly cross-linked three dimensional solid network resulting in a gel. The energetic materials can be incorporated during the formation of the solution or during the gel stage of the process. The composition, pore, and primary particle sizes, gel time, surface areas, and density may be tailored and controlled by the solution chemistry. The gel is then dried using supercritical extraction to produce a highly porous low density aerogel or by controlled slow evaporation to produce a xerogel. Applying stress during the extraction phase can result in high density materials. Thus, the sol-gel method can be used for precision detonator explosive manufacturing as well as producing precision explosives, propellants, and pyrotechnics, along with high power composite energetic materials.

Effect of Sol Concentration, Aging and Drying Process on Cerium Stabilization Zirconium Gel Produced by External Gelation

NASA Astrophysics Data System (ADS)

Sukarsono, R.; Rachmawati, M.; Susilowati, S. R.; Husnurrofiq, D.; Nurwidyaningrum, K.; Dewi, A. K.

2018-02-01

Cerium Stabilized Zirconium gel has been prepared using external gelation process. As the raw materials was used ZrO(NO3)2 and Ce(NO3)4 nitrate salt which was dissolved with water into Zr-Ce nitrate mixture. The concentration of the nitrate salt mixture in the sol solution was varied by varying the concentration of zirconium and cerium nitrate in the sol solution and the addition of PVA and THFA to produce a sol with a viscosity of 40-60 cP. The viscosity range of 40-60cP is the viscosity of the sol solution that was easy to produce a good gel in the gelation apparatus. Sol solution was casted in a gelation column equipped with following tools: a 1 mm diameter drip nozzle which was vibrated to adjust the best frequency and amplitude of vibration, a flow meter to measure the flow rate of sol, flowing of NH3 gas to presolidification process. Gelation column was contained NH4OH solution as gelation medium and gel container to collect gel product. Gel obtained from the gelation process than processed with ageing, washing, drying and calcinations to get round gel and not broken at calcinations up to 500°C. The parameters observed in this research are variation of Zr nitrate concentration, Ce nitrate concentration, ratio of Zr and Ce in the sol and ageing and drying process method which was appropriate to get a good gel. From the gelation processes that has been done, it can be seen that with the presolidification process can be obtained a round gel and without presolidification process, produce not round gel. In the process of ageing to get not broken gel, ageing was done on the rotary flask so that during the ageing, gels rotate in gelation media. Gels, then be washed by dilute ammonium nitrate, demireralized water and iso prophyl alcohol. The washed gel was then dried by vacuum drying to form pores on the gel which become the path for the gases resulting from decomposition of the gel to exit the gel. Vacuum drying can prevent cracking because the pores allow the gel to release the decomposition of the material during heating. Larger the concentration of nitric metal in sol solution, yields a gel with a larger diameter of gels. This research allows us to plan the diameter of the sintered particles to be made.

Preparation and characterization of silica xerogels as carriers for drugs.

PubMed

Czarnobaj, K

2008-11-01

The aim of the present study was to utilize the sol-gel method to synthesize different forms of xerogel matrices for drugs and to investigate how the synthesis conditions and solubility of drugs influence the change of the profile of drug release and the structure of the matrices. Silica xerogels doped with drugs were prepared by the sol-gel method from a hydrolyzed tetraethoxysilane (TEOS) solution containing two model compounds: diclofenac diethylamine, (DD)--a water-soluble drug or ibuprofen, (IB)--a water insoluble drug. Two procedures were used for the synthesis of sol-gel derived materials: one-step procedure (the sol-gel reaction was carried out under acidic or basic conditions) and the two-step procedure (first, hydrolysis of TEOS was carried out under acidic conditions, and then condensation of silanol groups was carried out under basic conditions) in order to obtain samples with altered microstructures. In vitro release studies of drugs revealed a similar release profile in two steps: an initial diffusion-controlled release followed by a slower release rate. In all the cases studied, the released amount of DD was higher and the released time was shorter compared with IB for the same type of matrices. The released amount of drugs from two-step prepared xerogels was always lower than that from one-step base-catalyzed xerogels. One-step acid-catalyzed xerogels proved unsuitable as the carriers for the examined drugs.

High-speed, Low Voltage, Miniature Electro-optic Modulators Based on Hybrid Photonic-Crystal/Polymer/Sol-Gel Technology

DTIC Science & Technology

2012-02-01

code) 01/02/2012 FINAL 15/11/2008 - 15/11/2011 High-speed, Low Voltage, Miniature Electro - optic Modulators Based on Hybrid Photonic-Crystal/Polymer... optic modulator, silicon photonics, integrated optics, electro - optic polymer, avionics, optical communications, sol-gel, nanotechnology U U U UU 25...2011 Program Manager: Dr. Charles Y-C Lee High-speed, Low Voltage, Miniature Electro - optic Modulators Based on Hybrid Photonic-Crystal/Polymer/Sol

Use of CdSe/ZnS luminescent quantum dots incorporated within sol-gel matrix for urea detection.

PubMed

Duong, Hong Dinh; Rhee, Jong Il

2008-09-19

In this work, urea detection techniques based on the pH sensitivity of CdSe/ZnS QDs were developed using three types of sol-gel membranes: a QD-entrapped membrane, urease-immobilized membrane and double layer consisting of a QD-entrapped membrane and urease-immobilized membrane. The surface morphology of the sol-gel membranes deposited on the wells in a 24-well microtiter plate was investigated. The linear detection range of urea was in the range of 0-10mM with the three types of sol-gel membranes. The urea detection technique based on the double layer consisting of the QD-entrapped membrane and urease-immobilized membrane resulted in the highest sensitivity to urea due to the Michaelis-Menten kinetic parameters. That is, the Michaelis-Menten constant (K(m)=2.0745mM) of the free urease in the QD-entrapped membrane was about 4-fold higher than that (K(m)=0.549mM) of the immobilized urease in the urease-immobilized membrane and about 12-fold higher than that (K(m)=0.1698mM) of the immobilized urease in the double layer. The good stability of the three sol-gel membranes for urea sensing over 2 months showed that the use of sol-gel membranes immobilized with QDs or an enzyme is suitable for biomedical and environmental applications.

Fabrication of a novel nanocomposite based on sol-gel process for hollow fiber-solid phase microextraction of aflatoxins: B1 and B2, in cereals combined with high performane liquid chromatography-diode array detection.

PubMed

Es'haghi, Zarrin; Sorayaei, Hoda; Samadi, Fateme; Masrournia, Mahboubeh; Bakherad, Zohreh

2011-10-15

The new pre-concentration technique, hollow fiber-solid phase microextraction based on carbon nanotube reinforced sol-gel and liquid chromatography-photodiode array detection was applied to determination of aflatoxins B(1), B(2) (AFB(1), AFB(2)) in rice, peanut and wheat samples. This research provides an overview of trends related to synthesis of solid phase microextraction (SPME) sorbnents that improves the assay of aflatoxins as the semi-polar compounds in several real samples. It mainly includes summary and a list of the results for a simple carbon nanotube reinforced sol-gel in-fiber device. This device was used for extraction, pre-concentration and determination of aflatoxins B1, B2 in real samples. In this technique carbon nanotube reinforced sol was prepared by the sol-gel method via the reaction of phenyl trimethoxysilane (PTMS) with a basic catalyst (tris hydroxymethyl aminomethan). The influences of microextraction parameters such as pH, ageing time, carbon nanotube contents, desorption conditions, desorption solvent and agitation speed were investigated. Optimal HPLC conditions were: C(18) reversed phase column for separation, water-acetonitril-methanol (35:10:55) as the mobile phase and maximum wavelength for detection was 370 nm. The method was evaluated statistically and under optimized conditions, the detection limits for the analytes were 0.074 and 0.061 ng/mL for B1 and B2 respectively. Limit of quantification for B1 and B2 was 0.1 ng/mL too (n=7). The precisions were in the range of 2.829-2.976% (n=3), and linear ranges were within 0.1 and 400 ng/mL. The method was successfully applied to the analysis of cereals (peanut, wheat, rice) with the relative recoveries from 47.43% to 106.83%. Copyright © 2011 Elsevier B.V. All rights reserved.

The sol-gel route: A versatile process for up-scaling the fabrication of gas-tight thin electrolyte layers

NASA Astrophysics Data System (ADS)

Viazzi, Céline; Rouessac, Vincent; Lenormand, Pascal; Julbe, Anne; Ansart, Florence; Guizard, Christian

2011-03-01

Sol-gel routes are often investigated and adapted to prepare, by suitable chemical modifications, submicronic powders and derived materials with controlled morphology, which cannot be obtained by conventional solid state chemistry paths. Wet chemistry methods provide attractive alternative routes because mixing of species occurs at the atomic scale. In this paper, ultrafine powders were prepared by a novel synthesis method based on the sol-gel process and were dispersed into suspensions before processing. This paper presents new developments for the preparation of functional materials like yttria-stabilized-zirconia (YSZ, 8% Y2O3) used as electrolyte for solid oxide fuel cells. YSZ thick films were coated onto porous Ni-YSZ substrates using a suspension with an optimized formulation deposited by either a dip-coating or a spin-coating process. The suspension composition is based on YSZ particles encapsulated by a zirconium alkoxide which was added with an alkoxide derived colloidal sol. The in situ growth of these colloids increases significantly the layer density after an appropriated heat treatment. The derived films were continuous, homogeneous and around 20 μm thick. The possible up-scaling of this process has been also considered and the suitable processing parameters were defined in order to obtain, at an industrial scale, homogeneous, crack-free, thick and adherent films after heat treatment at 1400 °C.

ELISA AND SOL-GEL BASED IMMUNOAFFINITY PURIFICATION OF THE PYRETHROID BIOALLETHRIN IN FOOD AND ENVIRONMENTAL SAMPLES

EPA Science Inventory

The peer-reviewed article describes the development of a new sol-gel based immunoaffinity purification procedure and an immunoassay for the pyrethroid bioallethrin. The immunoaffinity chromatography procedure was applied to food samples providing an efficient cleanup prior to im...

A new sol-gel synthesis of 45S5 bioactive glass using an organic acid as catalyst.

PubMed

Faure, J; Drevet, R; Lemelle, A; Ben Jaber, N; Tara, A; El Btaouri, H; Benhayoune, H

2015-02-01

In this paper a new sol-gel approach was explored for the synthesis of the 45S5 bioactive glass. We demonstrate that citric acid can be used instead of the usual nitric acid to catalyze the sol-gel reactions. The substitution of nitric acid by citric acid allows to reduce strongly the concentration of the acid solution necessary to catalyze the hydrolysis of silicon and phosphorus alkoxides. Two sol-gel powders with chemical compositions very close to that of the 45S5 were obtained by using either a 2M nitric acid solution or either a 5mM citric acid solution. These powders were characterized and compared to the commercial Bioglass®. The surface properties of the two bioglass powders were assessed by scanning electron microscopy (SEM) and by Brunauer-Emmett-Teller method (BET). The Fourier transformed infrared spectroscopy (FTIR) and the X-ray diffraction (XRD) revealed a partial crystallization associated to the formation of crystalline phases on the two sol-gel powders. The in vitro bioactivity was then studied at the key times during the first hours of immersion into acellular Simulated Body Fluid (SBF). After 4h immersion into SBF we clearly demonstrate that the bioactivity level of the two sol-gel powders is similar and much higher than that of the commercial Bioglass®. This bioactivity improvement is associated to the increase of the porosity and the specific surface area of the powders synthesized by the sol-gel process. Moreover, the nitric acid is efficiently substituted by the citric acid to catalyze the sol-gel reactions without alteration of the bioactivity of the 45S5 bioactive glass. Copyright © 2014 Elsevier B.V. All rights reserved.

Characterization of SrCo1.5Ti1.5Fe9O19 hexagonal ferrite synthesized by sol-gel combustion and solid state route

NASA Astrophysics Data System (ADS)

Vinaykumar, R.; Mazumder, R.; Bera, J.

2017-05-01

Co-Ti co-substituted SrM hexagonal ferrite (SrCo1.5Ti1.5Fe9O19) was synthesized by sol-gel combustion and solid state route. The effects of sources of TiO2 raw materials; titanium tetra-isopropoxide (TTIP) and titanyl nitrate (TN) on the phase formation behavior and properties of the ferrite were studied. The thermal decomposition behavior of the gel was studied using TG-DSC. The phase formation behavior of the ferrite was studied by using X-ray powder diffraction and FTIR analysis. Phase formation was comparatively easier in the TN-based sol-gel process. The morphology of powder and sintered ferrite was investigated using scanning electron microscope. Magnetic properties like magnetization, coercivity, permeability, tan δμ and dielectric properties were investigated. The ferrite synthesized by sol-gel based chemical route showed higher saturation magnetization, permeability and permittivity compared to the ferrite synthesized by solid state route.

A Review of Photocatalysts Prepared by Sol-Gel Method for VOCs Removal

PubMed Central

Tseng, Ting Ke; Lin, Yi Shing; Chen, Yi Ju; Chu, Hsin

2010-01-01

The sol-gel process is a wet-chemical technique (chemical solution deposition), which has been widely used in the fields of materials science, ceramic engineering, and especially in the preparation of photocatalysts. Volatile organic compounds (VOCs) are prevalent components of indoor air pollution. Among the approaches to remove VOCs from indoor air, photocatalytic oxidation (PCO) is regarded as a promising method. This paper is a review of the status of research on the sol-gel method for photocatalyst preparation and for the PCO purification of VOCs. The review and discussion will focus on the preparation and coating of various photocatalysts, operational parameters, and will provide an overview of general PCO models described in the literature. PMID:20640156

A review on development of solid phase microextraction fibers by sol-gel methods and their applications.

PubMed

Kumar, Ashwini; Gaurav; Malik, Ashok Kumar; Tewary, Dhananjay Kumar; Singh, Baldev

2008-03-03

Solid phase microextraction (SPME) is an innovative, solvent free technology that is fast, economical and versatile. SPME is a fiber coated with a liquid (polymer), a solid (sorbent) or a combination of both. The fiber coating takes up the compounds from the sample by absorption in the case of liquid coatings or adsorption in the case of solid coatings. The SPME fiber is then transferred with the help of a syringe like device into the analytical instrument for desorption and analysis of the target analytes. The sol-gel process provides a versatile method to prepare size, shape and charge selective materials of high purity and homogeneity by means of preparation techniques different from the traditional ones, for the chemical analysis. This review is on the current state of the art and future trends in the developments of solid phase microextraction (SPME) fibers using sol-gel method. To achieve more selective determination of different compound classes, the variety of different coating material for SPME fibers has increased. Further developments in SPME as a highly efficient extraction technique, will greatly depend on new breakthroughs in the area of new coating material developments for the SPME fibers. In sol-gel approach, appropriate sol-gel precursors and other building blocks can be selected to create a stationary phase with desired structural and surface properties. This approach is efficient in integrating the advantageous properties of organic and inorganic material systems and thereby increasing and improving the extraction selectivity of the produced amalgam organic-inorganic stationary phases. This review is mainly focused on recent advanced developments in the design, synthesis, characterisation, properties and application of sol-gel in preparation of coatings for the SPME fibers.

Low Concentration Fe-Doped Alumina Catalysts Using Sol-Gel and Impregnation Methods: The Synthesis, Characterization and Catalytic Performance during the Combustion of Trichloroethylene

PubMed Central

Maldonado, Carolina Solis; De la Rosa, Javier Rivera; Lucio-Ortiz, Carlos J.; Hernández-Ramírez, Aracely; Castillón Barraza, Felipe F.; Valente, Jaime S.

2014-01-01

The role of iron in two modes of integration into alumina catalysts was studied at 0.39 wt% Fe and tested in trichloroethylene combustion. One modified alumina was synthesized using the sol-gel method with Fe added in situ during hydrolysis; another modification was performed using calcined alumina, prepared using the sol-gel method and impregnated with Fe. Several characterization techniques were used to study the level of Fe modification in the γ-Al2O3 phase formed and to correlate the catalytic properties during trichloroethylene (TCE) combustion. The introduction of Fe in situ during the sol-gel process influenced the crystallite size, and three iron species were generated, namely, magnetite, maghemite and hematite. The impregnated Fe-alumina formed hematite and maghemite, which were highly dispersed on the γ-Al2O3 surface. The X-ray photoelectron spectra (XPS), FT-IR and Mössbauer spectroscopy analyses revealed how Fe interacted with the γ-Al2O3 lattice in both catalysts. The impregnated Fe-catalyst showed the best catalytic performance compared to the catalyst that was Fe-doped in situ by the sol-gel method; both had better catalytic activity than pure alumina. This difference in activity was correlated with the accessibility of the reactants to the hematite iron species on the surface. The chlorine poisoning for all three catalysts was less than 1.8%. PMID:28788556

Method for fabrication of ceramic dielectric films on copper foils

DOEpatents

Ma, Beihai; Narayanan, Manoj; Dorris, Stephen E.; Balachandran, Uthamalingam

2015-03-10

The present invention provides a method for fabricating a ceramic film on a copper foil. The method comprises applying a layer of a sol-gel composition onto a copper foil. The sol-gel composition comprises a precursor of a ceramic material suspended in 2-methoxyethanol. The layer of sol-gel is then dried at a temperature up to about 250.degree. C. The dried layer is then pyrolyzed at a temperature in the range of about 300 to about 450.degree. C. to form a ceramic film from the ceramic precursor. The ceramic film is then crystallized at a temperature in the range of about 600 to about 750.degree. C. The drying, pyrolyzing and crystallizing are performed under a flowing stream of an inert gas. In some embodiments an additional layer of the sol-gel composition is applied onto the ceramic film and the drying, pyrolyzing and crystallizing steps are repeated for the additional layer to build up a thicker ceramic layer on the copper foil. The process can be repeated one or more times if desired.

Sol-Gel-Based Titania-Silica Thin Film Overlay for Long Period Fiber Grating-Based Biosensors.

PubMed

Chiavaioli, Francesco; Biswas, Palas; Trono, Cosimo; Jana, Sunirmal; Bandyopadhyay, Somnath; Basumallick, Nandini; Giannetti, Ambra; Tombelli, Sara; Bera, Susanta; Mallick, Aparajita; Baldini, Francesco

2015-12-15

An evanescent wave optical fiber biosensor based on titania-silica-coated long period grating (LPG) is presented. The chemical overlay, which increases the refractive index (RI) sensitivity of the sensor, consists of a sol-gel-based titania-silica thin film, deposited along the sensing portion of the fiber by means of the dip-coating technique. Changing both the sol viscosity and the withdrawal speed during the dip-coating made it possible to adjust the thickness of the film overlay, which is a crucial parameter for the sensor performance. After the functionalization of the fiber surface using a methacrylic acid/methacrylate copolymer, an antibody/antigen (IgG/anti-IgG) assay was carried out to assess the performance of sol-gel based titania-silica-coated LPGs as biosensors. The analyte concentration was determined from the wavelength shift at the end of the binding process and from the initial binding rate. This is the first time that a sol-gel based titania-silica-coated LPG is proposed as an effective and feasible label-free biosensor. The specificity of the sensor was validated by performing the same model assay after spiking anti-IgG into human serum. With this structured LPG, detection limits of the order of tens of micrograms per liter (10(-11) M) are attained.

Development of a functionalized coating for inhibition of marine corrosion and biofouling

NASA Astrophysics Data System (ADS)

Gittens, Jeanette Elizabeth

The financial loss incurred by corrosion of metals in the marine environment has led to a need to develop effective, economic and environmentally friendly methods of protection. Traditional methods of counteracting the development of surface biofilms and biofouling within aqueous environments have involved implementing chemical biocides, often with a deleterious effect on non-target organisms. Sol gel coating technology offers a convenient route for immobilizing functional additives, such as inhibitors or, in the case of this study, biologically active microorganisms. Paenibacillus polymyxa biofilms inhibit the corrosion of metal substrates and this strain has the advantage of forming endospores can withstand the solvent and acid concentrations required in sol-gel formulation. Encapsulation of viable P. polymyxa endospores within the sol-gel matrix allowed germination on exposure to nutrients, when germinating endospores and vegetative cells were seen after fluorescence microscopy to be distributed throughout the coating. Laboratory electrochemical impedance tests were used to characterize the corrosion behaviour of the endospore-containing (biotic) sol-gel coating in comparison to an abiotic (no endospores) sol-gel only coating and one containing non-viable (killed) endospores. The technology enabled manipulation of the sol-gel formulation and the method of application to produce biotic sol-gel with enhanced corrosion inhibition properties on aluminium alloy. Field trials in a marine environment confirmed the corrosion protecting properties of the biotic coating and that the biotic coatings inhibited macroscopic biofouling for at least 29 weeks relative to the controls without encapsulated live endospores. Production of polymyxin by the encapsulated bacteria, which was proposed as a mechanism by which they inhibit MIC, was less than 1 mug per ml and below the threshold of detection by liquid chromatography mass spectrometry and antimicrobial bioassay. Microcosm experiments were used to study differences in the corrosion of abiotic and biotic coatings in the presence of a corrosion-causing sulphate-reducing bacterium. Scanning electrochemical microscopy was developed as a technique to study electrochemical processes on the coating surface and showed differences in the distribution of copper ions on the surface of abiotic and biotic coatings.The results of the experimental work in this thesis show the potential of encapsulating metabolically active bacterial cells within a sol-gel coating on metals for the control of marine corrosion and biofouling.

Electrochemiluminescence detection of NADH and ethanol based on partial sulfonation of sol-gel network with gold nanoparticles.

PubMed

Deng, Liu; Zhang, Lihua; Shang, Li; Guo, Shaojun; Wen, Dan; Wang, Fuan; Dong, Shaojun

2009-03-15

We developed a stable, sensitive electrochemiluminescence (ECL) biosensor based on the synthesis of a new sol-gel material with the ion-exchange capacity sol-gel to coimmobilize the Ru(bpy)(3)(2+) and enzyme. The partial sulfonated (3-mercaptopropyl)-trimethoxysilane sol-gel (PSSG) film acted as both an ion exchanger for the immobilization of Ru(bpy)(3)(2+) and a matrix to immobilize gold nanoparticles (AuNPs). The AuNPs/PSSG/Ru(bpy)(3)(2+) film modified electrode allowed sensitive the ECL detection of NADH as low as 1 nM. Such an ability of AuNPs/PSSG/Ru(bpy)(3)(2+) film to promote the electron transfer between Ru(bpy)(3)(2+) and the electrode suggested a new, promising biocompatible platform for the development of dehydrogenase-based ECL biosensors. With alcohol dehydrogenase (ADH) as a model, we then constructed an ethanol biosensor, which had a linear range of 5 microM to 5.2 mM with a detection limit of 12nM.

Sol-gel based optical sensor for determination of Fe (II): a novel probe for iron speciation.

PubMed

Samadi-Maybodi, Abdolraouf; Rezaei, Vida; Rastegarzadeh, Saadat

2015-02-05

A highly selective optical sensor for Fe (II) ions was developed based on entrapment of a sensitive reagent, 2,4,6-tri(2-pyridyl)-s-triazine (TPTZ), in a silica sol-gel thin film coated on a glass substrate. The thin films fabricated based on tetraethoxysilane (TEOS) as precursor, sol-gel pH∼3, water:alkoxyde ratio of 4:1 and TPTZ concentration of 0.112 mol L(-1). The influence of sol-gel parameters on sensing behavior of the fabricated sensor was also investigated. The fabricated sensor can be used for determination of Fe (II) ion with an outstanding high selectivity over a dynamic range of 5-115 ng mL(-1) and a detection limit of 1.68 ng mL(-1). It also showed reproducible results with relative standard deviation of 3.5% and 1.27% for 10 and 90 ng mL(-1) of Fe (II), respectively, along with a fast response time of ∼120 s. Total iron also was determined after reduction of Fe (III) to Fe (II) using ascorbic acid as reducing agent. Then, the concentration of Fe (III) was calculated by subtracting the concentration of Fe (II) from the total iron concentration. Interference studies showed a good selectivity for Fe (II) with trapping TPTZ into sol-gel matrix and appropriately adjusting the structure of doped sol-gel. The sensor was compared with other sensors and was applied to determine iron in different water samples with good results. Copyright © 2014 Elsevier B.V. All rights reserved.

The effect of silica-coating by sol-gel process on resin-zirconia bonding.

PubMed

Lung, Christie Ying Kei; Kukk, Edwin; Matinlinna, Jukka Pekka

2013-01-01

The effect of silica-coating by sol-gel process on the bond strength of resin composite to zirconia was evaluated and compared against the sandblasting method. Four groups of zirconia samples were silica-coated by sol-gel process under varied reagent ratios of ethanol, water, ammonia and tetraethyl orthosilicate and for different deposition times. One control group of zirconia samples were treated with sandblasting. Within each of these five groups, one subgroup of samples was kept in dry storage while another subgroup was aged by thermocycling for 6,000 times. Besides shear bond testing, the surface topography and surface elemental composition of silica-coated zirconia samples were also examined using scanning electron microscopy and X-ray photoelectron spectroscopy. Comparison of silica coating methods revealed significant differences in bond strength among the Dry groups (p<0.001) and Thermocycled groups (p<0.001). Comparison of sol-gel deposition times also revealed significant differences in bond strength among the Dry groups (p<0.01) and Thermocycled groups (p<0.001). Highest bond strengths were obtained after 141-h deposition: Dry (7.97±3.72 MPa); Thermocycled (2.33±0.79 MPa). It was concluded that silica-coating of zirconia by sol-gel process resulted in weaker resin bonding than by sandblasting.

Highly porous solid-phase microextraction fiber coating based on poly(ethylene glycol)-modified ormosils synthesized by sol-gel technology.

PubMed

da Costa Silva, Raquel Gomes; Augusto, Fabio

2005-04-22

The preparation and characteristics of solid-phase microextraction (SPME) fibers coated with Carbowax 20M ormosil (organically modified silica) are described here. Raw fused silica fibers were coated with Carbowax 20M-modified silica using sol-gel process. Scanning electron micrographs of fibers revealed a highly porous, sponge-like coating with an average thickness of (8 +/- 1) microm. The sol-gel Carbowax fibers were compared to commercial fibers coated with 100 microm polydimethylsiloxane (PDMS) and 65 microm Carbowax-divinylbenzene (DVB). Shorter equilibrium times were possible with the sol-gel Carbowax fiber: for headspace extraction of the test analytes, they ranged from less than 3 min for benzene to 15 min for o-xylene. Extraction efficiencies of the sol-gel Carbowax fiber were superior to those of conventional fibers: for o-xylene, the extracted masses were 230 and 540% of that obtained with 100 microm PDMS and 65 microm Carbowax-DVB fibers, respectively.

Development of flame retardant cotton fabric based on ionic liquids via sol-gel technique.

NASA Astrophysics Data System (ADS)

Bentis, A.; Boukhriss, A.; Boyer, D.; Gmouh, S.

2017-10-01

In this study, flame retardant cotton fabrics were developed by the sol-gel method, in order to enhance their flame retardant proprieties. For this aim, seven sols were prepared using tetraethylorthosilicate (TEOS) and different ionic liquids (ILs) consist on pyridinium and Methylimidazolium cations with different anions such as: PF6-, CH3COO-, and Br-. Those sols were applied separately to the cotton fabrics by a pad-dry-cure process. The flame retardant properties of functionalized cotton fabrics before and after washing were determined by the vertical flame tests according to ISO6940:2004(F) standard. The effects of anions have been thoroughly investigated, aiming at the optimization of the targeted properties. Thermogravimetric and mechanical according to NF EN ISO 13934-1:2013standard, analyses have been also investigated. The results showed that flame retardancy, thermal stability and mechanical properties of treated fabrics were enhanced by using ionic liquids.

Matrix molecularly imprinted mesoporous sol-gel sorbent for efficient solid-phase extraction of chloramphenicol from milk.

PubMed

Samanidou, Victoria; Kehagia, Maria; Kabir, Abuzar; Furton, Kenneth G

2016-03-31

Highly selective and efficient chloramphenicol imprinted sol-gel silica based inorganic polymeric sorbent (sol-gel MIP) was synthesized via matrix imprinting approach for the extraction of chloramphenicol in milk. Chloramphenicol was used as the template molecule, 3-aminopropyltriethoxysilane (3-APTES) and triethoxyphenylsilane (TEPS) as the functional precursors, tetramethyl orthosilicate (TMOS) as the cross-linker, isopropanol as the solvent/porogen, and HCl as the sol-gel catalyst. Non-imprinted sol-gel polymer (sol-gel NIP) was synthesized under identical conditions in absence of template molecules for comparison purpose. Both synthesized materials were characterized by Scanning Electron Microscopy (SEM), Fourier Transform Infrared Spectroscopy (FT-IR) and nitrogen adsorption porosimetry, which unambiguously confirmed their significant structural and morphological differences. The synthesized MIP and NIP materials were evaluated as sorbents for molecularly imprinted solid phase extraction (MISPE) of chloramphenicol in milk. The effect of critical extraction parameters (flow rate, elution solvent, sample and eluent volume, selectivity coefficient, retention capacity) was studied in terms of retention and desorption of chloramphenicol. Competition and cross reactivity tests have proved that sol-gel MIP sorbent possesses significantly higher specific retention and enrichment capacity for chloramphenicol compared to its non-imprinted analogue. The maximum imprinting factor (IF) was found as 9.7, whereas the highest adsorption capacity of chloramphenicol by sol-gel MIP was 23 mg/g. The sol-gel MIP was found to be adequately selective towards chloramphenicol to provide the necessary minimum required performance limit (MRPL) of 0.3 μg/kg set forth by European Commission after analysis by LC-MS even without requiring time consuming solvent evaporation and sample reconstitution step, often considered as an integral part in solid phase extraction work-flow. Intra and inter-assay RSD values were less than 13% and accuracy expressed as relative recovery ranged from 85 to 106%. Copyright © 2016 Elsevier B.V. All rights reserved.

Water-based sol-gel synthesis of hydroxyapatite: process development.

PubMed

Liu, D M; Troczynski, T; Tseng, W J

2001-07-01

Hydroxyapatite (HA) ceramics were synthesized using a sol-gel route with triethyl phosphite and calcium nitrate as phosphorus and calcium precursors, respectively. Two solvents, water and anhydrous ethanol, were used as diluting media for HA sol preparation. The sols were stable and no gelling occurred in ambient environment for over 5 days. The sols became a white gel only after removal of the solvents at 60 degrees C. X-ray diffraction showed that apatitic structure first appeared at a temperature as low as 350 degrees C. The crystal size and the HA content in both gels increase with increasing calcination temperature. The type of initial diluting media (i.e., water vs. anhydrous ethanol) did not affect the microstructural evolution and crystallinity of the resulting HA ceramic. The ethanol-based sol dip-coated onto a Ti substrate, followed by calcination at 450 degrees C, was found to be porous with pore size ranging from 0.3 to 1 microm. This morphology is beneficial to the circulation of physiological fluid when the coating is used for biomedical applications. The satisfactory adhesion between the coating and substrate suggests its suitability for load-bearing uses.

Blue light emission from trivalent cerium doped in sol-gel silica glass

NASA Astrophysics Data System (ADS)

Tokumitsu, Seika; Murakami, Yukon; Oda, Hisaya; Kawabe, Yutaka

2017-02-01

Rare earths in glass matrices are promising for active optical devices as amplifiers and lasers. Emission originating from d-f transitions in sol-gel glass has not been studied very often, while those based on f-f transitions were widely utilized. However, d-f emission in rare earths is very important because of their strong oscillator strength and broad emission widths suitable for the application to scintillators and solid-state lasers. Co-doping of aluminum in sol-gel synthesis was known to be effective for the emission enhancement of trivalent terbium and europium. Recently, we applied aluminum co-doping to cerium and europium systems in sol-gel glass to succeed in the observation of strong blue light emission originating from d-f transitions. Glass samples were prepared with conventional sol-gel process where tetramethylorthosilicate was hydrolyzed in the mixture of water, ethanol and dimethylformamide with nitric acid catalyst. After adding cerium nitrate and aluminum nitrate, the solution experienced drying followed by calcination at 1,050°C under air environment. When molar ratio of cerium to silicon was adjusted at 0.1% and Al concentration was varied in 0.1 2.0%, transparent glass products showed bright and broad blue photoluminescence under UV illumination. The fluorescence lifetimes were found to be about 50 90 ns, indicating that the emission was due to d-f transitions. Considering the simplicity of the process, blue phosphors based on sol-gel glass will be very promising for future applications.

Separation of oligopeptides, nucleobases, nucleosides and nucleotides using capillary electrophoresis/electrochromatography with sol-gel modified inner capillary wall.

PubMed

Svobodová, Jana; Kofroňová, Olga; Benada, Oldřich; Král, Vladimír; Mikšík, Ivan

2017-09-29

The aim of this article is to study the modification of an inner capillary wall with sol-gel coating (pure silica sol-gel or silica sol-gel containing porphyrin-brucine conjugate) and determine its influence on the separation process using capillary electrophoresis/electrochromatography method. After modification of the inner capillary surface the separation of analytes was performed using two different phosphate buffers (pH 2.5 and 9.0) and finally the changes in electrophoretic mobilities of various samples were calculated. To confirm that the modification of the inner capillary surface was successful, the parts of the inner surfaces of capillaries were observed using scanning electron microscopy. The analytes used as testing samples were oligopeptides, nucleosides, nucleobases and finally nucleotides. Copyright © 2017 Elsevier B.V. All rights reserved.

Growth and Characterization of CuO Nanostructures on Si for the Fabrication of CuO/p-Si Schottky Diodes

PubMed Central

Çetinkaya, S.; Çetinkara, H. A.; Bayansal, F.; Kahraman, S.

2013-01-01

CuO interlayers in the CuO/p-Si Schottky diodes were fabricated by using CBD and sol-gel methods. Deposited CuO layers were characterized by SEM and XRD techniques. From the SEM images, it was seen that the film grown by CBD method is denser than the film grown by sol-gel method. This result is compatible with XRD results which show that the crystallization in CBD method is higher than it is in sol-gel method. For the electrical investigations, current-voltage characteristics of the diodes have been studied at room temperature. Conventional I-V and Norde's methods were used in order to determine the ideality factor, barrier height, and series resistance values. It was seen that the morphological and structural analysis are compatible with the results of electrical investigations. PMID:23766670

Administration of a Sol-Gel Formulation of Phenylephrine Using Low-Temperature Hollow Microneedle for Treatment of Intermittent Fecal Incontinence.

PubMed

Lee, Hyunji; Park, Jung-Hwan; Park, Jung Ho

2017-12-01

A low temperature hollow microneedle system was devised to deliver sol-gel transition formulation near the surface of the skin for extended release and local delivery of drug by a non-invasive method. This new system can improve treatment of intermittent fecal incontinence. The low-temperature system was integrated with a hollow microneedle to maintain the low temperature of the sol formulation. Various sol-gel formulations using Pluronic F-127 (PF-127) and Hydroxy-propyl-methyl-cellulose (HPMC) were prepared, and their gelation temperature, flow property, and diffusion retardation were observed. Resting anal sphincter pressure in response to a phenylephrine (PE) sol-gel formulation was measured using an air-charged catheter. The biocompatibility of the sol-gel PE formulation was evaluated by observing the immunological response. When the PF-127 25%, HPMC 1% and PE formulation (PF25-HPMC1-PE) was injected through the peri-anal skin of the rat in vivo, the highest pressure on the anal sphincter muscle occurred at 6-8 h and anal pressure increased and lasted twice as long as with the phosphate-buffered saline (PBS)-PE formulation. There was no significant difference in the number of mast cells after administration into the rat in vivo between the PF25-HPMC1-PE formulation and the PBS-PE formulation. The combination of a low-pain hollow microneedle system and an injectable sol-gel formulation improved the efficacy of treatment of intermittent fecal incontinence. A low-temperature hollow microneedle system using a sol-gel formulation has many applications in medical treatments that require depot effect, local targeting, and pain control.

Coating and curing apparatus and methods

DOEpatents

Brophy, Brenor L; Maghsoodi, Sina; Neyman, Patrick J; Gonsalves, Peter R; Hirsch, Jeffrey G; Yang, Yu S

2015-02-24

Disclosed are coating apparatus including flow coating and roll-coating that may be used for uniform sol-gel coating of substrates such as glass, solar panels, windows or part of an electronic display. Also disclosed are methods for substrate preparation, flow coating and roll coating. Lastly systems and methods for skin curing sol-gel coatings deposited onto the surface of glass substrates using a high temperature air-knife are disclosed.

Nonhydrolytic sol-gel approach to facile creation of surface-bonded zirconia organic-inorganic hybrid coatings for sample preparation. Ι. Capillary microextraction of catecholamine neurotransmitters.

PubMed

Alhendal, Abdullah; Mengis, Stephanie; Matthews, Jacob; Malik, Abdul

2016-10-14

Nonhydrolytic sol-gel (NHSG) route was used for the creation of novel zirconia-polypropylene oxide (ZrO 2 -PPO) sol-gel hybrid sorbents in the form of surface coatings for the extraction and preconcentration of catecholamine neurotransmitters and molecules structurally related to their deaminated metabolites. In comparison to other sorbents made of inorganic transition metal oxides, the presented hybrid organic-inorganic sorbents facilitated reversible sorption properties that allowed for efficient desorption of the extracted analytes by LC-MS compatible mobile phases. The presented sol-gel hybrid sorbents effectively overcame the major drawbacks of traditional silica- or polymer-based sorbents by providing superior pH stability (pH range: 0-14), and a variety of intermolecular interactions. Nonaqueous sol-gel treatment of PPO with ZrCl 4 was employed for the derivatization of the terminal hydroxyl groups on PPO, providing zirconium trichloride-containing end groups characterized by enhanced sol-gel reactivity. NHSG ZrO 2 -PPO sorbent provided excellent microextraction performance for catecholamines, low detection limits (5.6-9.6pM), high run-to-run reproducibility (RSD 0.6-5.1%), high desorption efficiency (95.0-99.5%) and high enrichment factors (∼1480-2650) for dopamine and epinephrine, respectively, extracted from synthetic urine samples. The presented sol-gel sorbents provided effective alternative to conventional extraction media providing unique physicochemical characteristics and excellent extraction capability. Copyright © 2016 Elsevier B.V. All rights reserved.

Optical Sensors for Biomolecules Using Nanoporous Sol-Gel Materials

NASA Technical Reports Server (NTRS)

Fang, Jonathan; Zhou, Jing C.; Lan, Esther H.; Dunn, Bruce; Gillman, Patricia L.; Smith, Scott M.

2004-01-01

An important consideration for space missions to Mars is the ability to detect biosignatures. Solid-state sensing elements for optical detection of biological entities are possible using sol-gel based biologically active materials. We have used these materials as optical sensing elements in a variety of bioassays, including immunoassays and enzyme assays. By immobilizing an appropriate biomolecule in the sol-gel sensing element, we have successfully detected analytes such as amino acids and hormones. In the case of the amino acid glutamate, the enzyme glutamate dehydrogenase was the immobilized molecule, whereas in the case of the hormone cortisol, an anti-cortisol antibody was immobilized in the sensing element. In this previous work with immobilized enzymes and antibodies, excellent sensitivity and specificity were demonstrated in a variety of formats including bulk materials, thin films and fibers. We believe that the sol-gel approach is an attractive platform for bioastronautics sensing applications because of the ability to detect a wide range of entities such as amino acids, fatty acids, hopanes, porphyrins, etc. The sol-gel approach produces an optically transparent 3D silica matrix that forms around the biomolecule of interest, thus stabilizing its structure and functionality while allowing for optical detection. This encapsulation process protects the biomolecule and leads to a more "rugged" sensor. The nanoporous structure of the sol-gel matrix allows diffusion of small target molecules but keeps larger, biomolecules immobilized in the pores. We are currently developing these biologically active sol-gel materials into small portable devices for on-orbit cortisol detection

A thermosensitive hydrogel based on biodegradable amphiphilic poly(ethylene glycol) polycaprolactone poly(ethylene glycol) block copolymers

NASA Astrophysics Data System (ADS)

Gong, Chang Yang; Qian, Zhi Yong; Liu, Cai Bing; Juan Huang, Mei; Gu, Ying Chun; Wen, Yan Jun; Kan, Bing; Wang, Ke; Dai, Mei; Li, Xing Yi; Gou, Ma Ling; Tu, Ming Jing; Wei, Yu Quan

2007-06-01

A series of low molecular weight poly(ethylene glycol)-polycaprolactone-poly(ethylene glycol) (PEG-PCL-PEG) biodegradable block copolymers were successfully synthesized using isophorone diisocyanate (IPDI) as the coupling agent, and were characterized using 1H NMR and Fourier transform infrared spectroscopy. The aqueous solutions of the PEG-PCL-PEG copolymers displayed a special thermosensitive gel-sol transition when the concentration was above the corresponding critical gel concentration. Gel-sol phase diagrams were recorded using the test-tube-inversion method; they depended on the hydrophilic/hydrophobic balance in the macromolecular structure, as well as some other factors, including the heating history, volume, and the ageing time of the copolymer aqueous solutions and dissolution temperature of the copolymers. As a result, the gel-sol transition temperature range could be altered, which might be very useful for application in injectable drug delivery systems. This work was financially supported by the Chinese Key Basic Research Program (2004CB518800 and 2004CB518807), and the Sichuan Key Project of Science and Technology (06(05SG022-021-02)).

Sol-gel processing to form doped sol-gel monoliths inside hollow core optical fiber and sol-gel core fiber devices made thereby

NASA Technical Reports Server (NTRS)

Shaw, Harry C. (Inventor); Ott, Melanie N. (Inventor); Manuel, Michele V. (Inventor)

2002-01-01

A process of fabricating a fiber device includes providing a hollow core fiber, and forming a sol-gel material inside the hollow core fiber. The hollow core fiber is preferably an optical fiber, and the sol-gel material is doped with a dopant. Devices made in this manner includes a wide variety of sensors.

Sol-gel layers for ceramic microsystems application

NASA Astrophysics Data System (ADS)

Czok, Mateusz; Golonka, Leszek

2016-11-01

This paper describes research on sol-gel solutions preparation process. Utilize of a sol-gel layers in the LTCC technology for reduction of surface roughness and influence on the ceramics properties is examined and described. The influence of sol-gel layer on possible sedimentation of dyes or biological substances in channels, mixers or chambers of ceramic microfluidic structures was investigated. Moreover, properties of sol-gel coated surfaces have been precisely examined and described. Finally, positive results of conducted experiments made it possible to design and manufacture a simple microfluidic ceramic structure, with embedded protective layer of sol-gel, for fluorescence measurements.

Novel capsule phase microextraction in combination with liquid chromatography-tandem mass spectrometry for determining personal care products in environmental water.

PubMed

Lakade, Sameer S; Borrull, Francesc; Furton, Kenneth G; Kabir, Abuzar; Marcé, Rosa Maria; Fontanals, Núria

2018-05-01

A novel sample preparation technique named capsule phase microextraction (CPME) is presented here. The technique utilizes a miniaturized microextraction capsule (MEC) as the extraction medium. The MEC consists of two conjoined porous tubular polypropylene membranes, one of which encapsulates the sorbent through sol-gel technology, while the other encapsulates a magnetic metal rod. As such, MEC integrates both the extraction and stirring mechanisms into a single device. The aim of this article is to demonstrate the application potential of CPME as sample preparation technique for the extraction of a group of personal care products (PCPs) from water matrices. Among the different sol-gel sorbent materials (UCON ® , poly(caprolactone-dimethylsiloxane-caprolactone) (PCAP-DMS-CAP) and Carbowax 20M (CW-20M)) evaluated, CW-20M MEC demonstrated the best extraction performance for the selected PCPs. The extraction conditions for sol-gel CW-20M MEC were optimized, including sample pH, stirring speed, addition of salt, extraction time, sample volume, liquid desorption solvent, and time. Under the optimal conditions, sol-gel CW-20M MEC provided recoveries, ranging between 47 and 90% for all analytes, except for ethylparaben, which showed a recovery of 26%. The method based on CPME with sol-gel CW-20M followed by liquid chromatography-tandem mass spectrometry was developed and validated for the extraction of PCPs from river water and effluent wastewater samples. When analyzing different environmental samples, some analytes such as 2,4-dihydroxybenzophenone, 2,2-dihydroxy-4-4 methoxybenzophenone and 3-benzophenone were found at low ng L -1 .

Soft nanoimprint lithography on SiO2 sol-gel to elaborate sensitive substrates for SERS detection

NASA Astrophysics Data System (ADS)

Hamouda, Frédéric; Bryche, Jean-François; Aassime, Abdelhanin; Maillart, Emmanuel; Gâté, Valentin; Zanettini, Silvia; Ruscica, Jérémy; Turover, Daniel; Bartenlian, Bernard

2017-12-01

This paper presents a new alternative fabrication of biochemical sensor based on surface enhanced Raman scattering (SERS) by soft nanoimprint lithography (S-NIL) on SiO2 sol-gel. Stabilization of the sol-gel film is obtained by annealing which simplifies the manufacturing of these biosensors and is compatible with mass production at low cost. This detector relies on a specific pattern of gold nanodisks on a thin gold film to obtain a better sensitivity of molecules' detection. Characterizations of SERS devices were performed on a confocal Raman microspectrophotometer after a chemical functionalization. We report a lateral collapse effect on poly(diméthylsiloxane) (PDMS) stamp for specific nanostructure dimensions. This unintentional effect is used to evaluate S-NIL resolution in SiO2 sol-gel.

Production and characterization of europium doped sol-gel yttrium oxide

NASA Astrophysics Data System (ADS)

Krebs, J. K.; Hobson, Christopher; Silversmith, Ann

2004-03-01

Sol-gel produced materials have recently gained attention for their use in producing nanoscale dielectric materials for confinement studies. Lanthanide impurities in the dielectric enable experimenters to optically probe the structure and dynamic properties of the nanoparticle hosts. We report on an alkoxide sol-gel production method used to produce trivalent europium doped yttrium oxide. Our process follows the standard hydrolysis of an alkoxide precursor with water containing the lanthanide ions. The sol is then aged and calcined at 800 ^oC to produce the powder samples. X-ray diffraction confirms the structure of the powder is that of Y_2O_3. The emission and excitation of the europium impurities is consistent with that of europium doped single crystal yttrium oxide, where it is known that the europium ions substitute for yttrium in the lattice. We therefore conclude that the sol-gel process enables the incorporation of europium ions into the yttrium oxide structure at temperatures far below the melting temperature. The results of preliminary dynamics measurements will also be discussed.

Synthesis of phthalocyanine doped sol-gel materials

NASA Technical Reports Server (NTRS)

Dunn, Bruce

1993-01-01

The synthesis of sol-gel silica materials doped with three different types of metallophthalocyanines has been studied. Homogeneous materials of good optical quality were prepared and the first optical limiting measurements of dyes in sol-gel hosts were carried out. The properties of these solid state limiters are similar to limiters based on phthalocyanine (Pc) in solution. Sol-gel silica materials containing copper, tin and germanium phthalocyanines were investigated. The initial step in all cases was to prepare silica sols by the sonogel method using tetramethoxy silane (TMOS), HCl and distilled water. Thereafter, the synthesis depended upon the specific Pc and its solubility characteristics. Copper phthalocyanine tetrasulfonic acid tetra sodium salt (CuPc4S) is soluble in water and various doping levels (1 x 10 (exp -4) M to 1 x 10 (exp -5) M) were added to the sol. The group IV Pc's, SnPc(OSi(n-hexyl)3)2 and GePc(OSi(n-hexyl)3)2, are insoluble in water and the process was changed accordingly. In these cases, the compounds were dissolved in THF and then added to the sol. The Pc concentration in the sol was 2 x 10(exp -5)M. The samples were then aged and dried in the standard method of making xerogel monoliths. Comparative nanosecond optical limiting experiments were performed on silica xerogels that were doped with the different metallophthalocyanines. The ratio of the net excited state absorption cross section (sigma(sub e)) to the ground state cross section (sigma(sub g)) is an important figure of merit that is used to characterize these materials. By this standard the SnPc sample exhibits the best limiting for the Pc doped sol-gel materials. Its cross section ratio of 19 compares favorably with the value of 22 that was measured in toluene. The GePc materials appear to not be as useful as those containing SnPc. The GePc doped solids exhibit a higher onset energy (2.5 mj and lower cross section ratio, 7. The CuPc4S sol-gel material has a still lower cross section ratio, 4, however, the tetrasulfonate groups make the dye soluble in water which greatly facilitates its incorporation into the sol-gel matrix. The nonlinear transmission of CuPc4S in a pH 2 buffer solution and in a silica xerogel were compared. It is evident that the CuPc4S preserves its optical limiting behavior in the sol-gel matrix, indicating that the fundamental excited state absorption process is essentially the same for a molecule in solution or in the solid state. Although the spectroscopic details of energy level lifetimes are unknown, the significance is that passive optical limiting has been achieved in the solid state via incorporation of a dye into an inorganic host. The only compromise occurs at the extremely high energy regime where photobleaching is observed. This is a result of the limited mobility of the dye molecules in the solid silica host relative to a liquid host. The effects of photodegradation in the xerogel are additive, whereas the solution provides a supply of fresh molecules that are free to enter the active volume between pulses.

Evaluation of cost-effective sol-gel-based sensor for monitoring of formaldehyde in workplace environment and cancer risk assessment.

PubMed

Bunkoed, Opas; Thavarungkul, Panote; Thammakhet, Chongdee; Kanatharana, Proespichaya

2013-01-01

Formaldehyde was monitored in the workplace environment of an adhesive manufacturer producing formaldehyde and urea-formaldehyde resin using a cost-effective sol-gel-based sensor. The sensor was first evaluated by comparing its performance to the conventional 2,4-dinitrophynylhydrazine-devivatization method (2,4-DNPH) followed by high-performance liquid chromatography coupled to a UV detector. The formaldehyde concentrations obtained by both techniques were not significantly different. The cost-effective sol-gel-based sensor was then used for monitoring formaldehyde levels in the laboratories, production areas and storage room. Formaldehyde concentrations in this adhesive manufacturer workplace environment were lower than the limit value of, 0.75 ppm for an 8-h time weight average and 2 ppm for a short-term exposure (15 min). However, the cancer risk for employees who worked in the laboratories, (1.7±0.7)×10(-4)-(5±2)×10(-4), were higher than the acceptable cancer risk recommended by the US EPA (10(-6)). Therefore, some precaution should be taken to reduce the risk, such as an increase of ventilation to dilute the levels of formaldehyde and use air cleaners to remove formaldehyde.

Radiation hardening in sol-gel derived Er{sup 3+}-doped silica glasses

DOE Office of Scientific and Technical Information (OSTI.GOV)

Hari Babu, B., E-mail: hariphy2012@gmail.com, E-mail: matthieu.lancry@u-psud.fr; León Pichel, Mónica; Institut de Chimie Moléculaire et des Matériaux d'Orsay, UMR CNRS-UPSud 8182, Université Paris Sud, 91405 Orsay

2015-09-28

The aim of the present paper is to report the effect of radiation on the Er{sup 3+}-doped sol-gel silica glasses. A possible application of these sol-gel glasses could be their use in harsh radiation environments. The sol-gel glasses are fabricated by densification of erbium salt-soaked nanoporous silica xerogels through polymeric sol-gel technique. The radiation-induced attenuation of Er{sup 3+}-doped sol-gel silica is found to increase with erbium content. Electron paramagnetic resonance studies reveal the presence of E′{sub δ} point defects. This happens in the sol-gel aluminum-silica glass after an exposure to γ-rays (kGy) and in sol-gel silica glass after an exposuremore » to electrons (MGy). The concentration levels of these point defects are much lower in γ-ray irradiated sol-gel silica glasses. When the samples are co-doped with Al, the exposure to γ-ray radiation causes a possible reduction of the erbium valence from Er{sup 3+} to Er{sup 2+} ions. This process occurs in association with the formation of aluminum oxygen hole centers and different intrinsic point defects.« less

Coating and curing apparatus and methods

DOEpatents

Brophy, Brenor L.; Gonsalves, Peter R.; Maghsoodi, Sina; Colson, Thomas E.; Yang, Yu S.; Abrams, Ze'ev R.

2016-04-19

Disclosed is a coating apparatus including flow coating and roll-coating that may be used for uniform sol-gel coating of substrates such as glass, solar panels, windows or part of an electronic display. Also disclosed are methods for substrate preparation, flow coating and roll coating. Lastly, systems and methods for curing sol-gel coatings deposited onto the surface of glass substrates using high temperature air-knives, infrared emitters and direct heat applicators are disclosed.

Quantitative determination of Escherichia coli based on the electrochemical measurement of bacterial catalase activity using H2O2-selective organic/inorganic-hybrid sol-gel film-modified Pt electrode.

PubMed

Hasebe, Yasushi; Fukuzawa, Michiru; Matsuhisa, Hironori

2009-01-01

Quantitative determination of Escherichia coli (E. coli) concentration was achieved by measuring the intrinsic catalase activity of E. coli using novel H2O2-selective organic/inorganic-hybrid sol-gel film-modified platinum (Pt) wire electrode. This hybrid sol-gel film is composed of three kinds of organosilanes and two biopolymers (i.e., chitosan and bovine serum albumin), and exhibited an excellent permselectivity toward H2O2 based on a size-exclusive mechanism. The steady-state anodic current for 100 [xmol/L H2O2 at +0.6 V (vs. Ag/AgCl) in 0.1 mol/L phosphate buffer (pH 6.5) solution was apparently diminished by the addition of E. coli samples, due to the decomposition of H2O2 by intrinsic catalase activity of E. coli. The time-dependent decrease in current (-AI/At) was significantly dependent on the E. coli concentration. The -AI/At was enhanced by the permeabilization pretreatment of E. coli samples with the mixed solution of polymyxin B and lysozyme. This H2O2-selective organic/inorganic-hybrid sol-gel film-modified platinum (Pt) wire electrode allowed quantitative determination of E. coli concentration ranging from 10(6) to 10(9) CFU/mL within 30 min. This method required no label and complicated procedure, and allowed rapid, simple and cost-effective quantitative electrochemical determination of catalase-positive bacteria.

The role of temperature in forming sol-gel biocomposites containing polydopamine.

PubMed

Dyke, Jason Christopher; Hu, Huamin; Lee, Dong Joon; Ko, Ching-Chang; You, Wei

2014-11-28

To further improve the physical strength and biomedical applicability of bioceramicsbuilt on hydroxyapatite-gelatin (HAp-Gel) and siloxane sol-gel reactions, we incorporated mussel adhesive inspired polydopamine (PD) into our original composite based on HAp-Gel cross-linked with siloxane. Surprisingly, with the addition of PD, we observed that the processing conditions and temperatures play an important role in the structure and performance of these materials. A systematic study to investigate this temperature dependence behavior discloses that the rate of crosslinking of silane during the sol-gel process is significantly influenced by the temperature, whereas the polymerization of the dopamine only shows minor temperature dependence. With this discovery, we report an innovative thermal process for the design and application of these biocomposites.

The role of temperature in forming sol-gel biocomposites containing polydopamine

PubMed Central

Dyke, Jason Christopher; Hu, Huamin; Lee, Dong Joon; Ko, Ching-Chang; You, Wei

2014-01-01

To further improve the physical strength and biomedical applicability of bioceramicsbuilt on hydroxyapatite-gelatin (HAp-Gel) and siloxane sol-gel reactions, we incorporated mussel adhesive inspired polydopamine (PD) into our original composite based on HAp-Gel cross-linked with siloxane. Surprisingly, with the addition of PD, we observed that the processing conditions and temperatures play an important role in the structure and performance of these materials. A systematic study to investigate this temperature dependence behavior discloses that the rate of crosslinking of silane during the sol-gel process is significantly influenced by the temperature, whereas the polymerization of the dopamine only shows minor temperature dependence. With this discovery, we report an innovative thermal process for the design and application of these biocomposites. PMID:25485111

3D Printed PEG-Based Hybrid Nanocomposites Obtained by Sol-Gel Technique.

PubMed

Chiappone, Annalisa; Fantino, Erika; Roppolo, Ignazio; Lorusso, Massimo; Manfredi, Diego; Fino, Paolo; Pirri, Candido Fabrizio; Calignano, Flaviana

2016-03-02

In this work, three-dimensional (3D) structured hybrid materials were fabricated combining 3D printing technology with in situ generation of inorganic nanoparticles by sol-gel technique. Those materials, consisting of silica nanodomains covalently interconnected with organic polymers, were 3D printed in complex multilayered architectures, incorporating liquid silica precursors into a photocurable oligomer in the presence of suitable photoinitiators and exposing them to a digital light system. A post sol-gel treatment in acidic vapors allowed the in situ generation of the inorganic phase in a dedicated step. This method allows to build hybrid structures operating with a full liquid formulation without meeting the drawbacks of incorporating inorganic powders into 3D printable formulations. The influence of the generated silica nanoparticle on the printed objects was deeply investigated at macro- and nanoscale; the resulting light hybrid structures show improved mechanical properties and, thus, have a huge potential for applications in a variety of advanced technologies.

Investigation of phase evolution of CaCu3Ti4O12 (CCTO) by in situ synchrotron high-temperature powder diffraction

NASA Astrophysics Data System (ADS)

Ouyang, Xin; Huang, Saifang; Zhang, Weijun; Cao, Peng; Huang, Zhaohui; Gao, Wei

2014-03-01

In situ synchrotron X-ray powder diffraction was used to study the high-temperature phase evolution of CaCu3Ti4O12 (CCTO) precursors prepared via solid-state and sol-gel methods. After the precursors are heated to 1225 °C, the CCTO phase is the main phase observed in the calcined powder, with the presence of some minor impurities. Comparing the two precursors, we found that the onset temperature for the CCTO phase formation is 800 °C in the sol-gel precursor, lower than that in the solid-state precursor (875 °C). Intermediate phases were only observed in the sol-gel precursor. Both precursors are able to be calcined to sub-micrometric sized powders. Based on the synchrotron data along with differential scanning calorimetry (DSC) and thermal gravimetric analysis (TGA), the phase formation sequence and mechanism during calcination are proposed in this study.

Spectrofluorimetric assessment of hydrochlorothiazide using optical sensor nano-composite terbium ion doped in sol-gel matrix.

PubMed

Youssef, A O

2012-05-01

A new, simple, sensitive and selective spectrofluorimetric method for the determination of Hydrochlorothiazide was developed in acetonitrile at pH 6.2. The Hydrochlorothiazide can remarkably enhance the luminescence intensity of the Tb(3+) ion doped in sol-gel matrix at λ(ex) = 370 nm. The intensity of the emission band of Tb(3+) ion doped in sol-gel matrix was increased due to the energy transfer from the triplet excited state of Hydrochlorothiazide to ((5)D(4)) excited energy state of Tb(3) ion. The enhancement of the emission band of Tb(3+) ion doped in sol-gel matrix at ((5)D(4)→(7)F(5)) 545 nm was directly proportion to the concentration of Hydrochlorothiazide with a dynamic ranges of 5.0 × 10(-10)-5.0 × 10(-6) mol L(-1) and detection limit of 2.2 × 10(-11) mol L(-1).

Highly sensitive and selective spectrofluorimetric determination of metoclopramide hydrochloride in pharmaceutical tablets and serum samples using Eu3+ ion doped in sol-gel matrix.

PubMed

Attia, M S; Aboaly, M M

2010-06-30

A simple, sensitive and selective spectrofluorimetric method for the determination of Metoclopramide hydrochloride (MCP) is developed. The MCP can remarkably enhances the luminescence intensity of the Eu(3+) ion doped in sol-gel matrix at lambda(ex)=380 nm in DMSO at pH 8.7. The intensity of the emission band of Eu(3+) ion doped in sol-gel matrix increases due to energy transfer from MCP to Eu(3+) in the excited state. The enhancement of the emission band of Eu(3+) ion doped in sol-gel matrix at 617 nm was found to be directly proportional to the concentration of MCP with a dynamic range of 5 x 10(-9) - 1.0 x 10(-6) mol L(-1) and detection limit of 2.2 x10(-11) mol L(-1). Copyright 2010 Elsevier B.V. All rights reserved.

A new sol-gel process for producing Na(2)O-containing bioactive glass ceramics.

PubMed

Chen, Qi-Zhi; Li, Yuan; Jin, Li-Yu; Quinn, Julian M W; Komesaroff, Paul A

2010-10-01

The sol-gel process of producing SiO(2)-CaO bioactive glasses is well established, but problems remain with the poor mechanical properties of the amorphous form and the bioinertness of its crystalline counterpart. These properties may be improved by incorporating Na(2)O into bioactive glasses, which can result in the formation of a hard yet biodegradable crystalline phase from bioactive glasses when sintered. However, production of Na(2)O-containing bioactive glasses by sol-gel methods has proved to be difficult. This work reports a new sol-gel process for the production of Na(2)O-containing bioactive glass ceramics, potentially enabling their use as medical implantation materials. Fine powders of 45S5 (a Na(2)O-containing composition) glass ceramic have for the first time been successfully synthesized using the sol-gel technique in aqueous solution under ambient conditions, with the mean particle size being approximately 5 microm. A comparative study of sol-gel derived S70C30 (a Na(2)O-free composition) and 45S5 glass ceramic materials revealed that the latter possesses a number of features desirable in biomaterials used for bone tissue engineering, including (i) the crystalline phase Na(2)Ca(2)Si(3)O(9) that couples good mechanical strength with satisfactory biodegradability, (ii) formation of hydroxyapatite, which may promote good bone bonding and (iii) cytocompatibility. In contrast, the sol-gel derived S70C30 glass ceramic consisted of a virtually inert crystalline phase CaSiO(3). Moreover, amorphous S70C30 largely transited to CaCO(3) with minor hydroxyapatite when immersed in simulated body fluid under standard tissue culture conditions. In conclusion, sol-gel derived Na(2)O-containing glass ceramics have significant advantages over related Na(2)O-free materials, having a greatly improved combination of mechanical capability and biological absorbability. 2010 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.

Tuning of thermally induced sol-to-gel transitions of moderately concentrated aqueous solutions of doubly thermosensitive hydrophilic diblock copolymers poly(methoxytri(ethylene glycol) acrylate)-b-poly(ethoxydi(ethylene glycol) acrylate-co-acrylic acid).

PubMed

Jin, Naixiong; Zhang, Hao; Jin, Shi; Dadmun, Mark D; Zhao, Bin

2012-03-15

We report in this article a method to tune the sol-to-gel transitions of moderately concentrated aqueous solutions of doubly thermosensitive hydrophilic diblock copolymers that consist of two blocks exhibiting distinct lower critical solution temperatures (LCSTs) in water. A small amount of weak acid groups is statistically incorporated into the lower LCST block so that its LCST can be tuned by varying solution pH. Well-defined diblock copolymers, poly(methoxytri(ethylene glycol) acrylate)-b-poly(ethoxydi(ethylene glycol) acrylate-co-acrylic acid) (PTEGMA-b-P(DEGEA-co-AA)), were prepared by reversible addition-fragmentation chain transfer polymerization and postpolymerization modification. PTEGMA and PDEGEA are thermosensitive water-soluble polymers with LCSTs of 58 and 9 °C, respectively, in water. A 25 wt % aqueous solution of PTEGMA-b-P(DEGEA-co-AA) with a molar ratio of DEGEA to AA units of 100:5.2 at pH = 3.24 underwent multiple phase transitions upon heating, from a clear, free-flowing liquid (<15 °C) to a clear, free-standing gel (15-46 °C) to a clear, free-flowing hot liquid (47-56 °C), and a cloudy mixture (≥57 °C). With the increase of pH, the sol-to-gel transition temperature (T(sol-gel)) shifted to higher values, while the gel-to-sol transition (T(gel-sol)) and the clouding temperature (T(clouding)) of the sample remained essentially the same. These transitions and the tunability of T(sol-gel) originated from the thermosensitive properties of two blocks of the diblock copolymer and the pH dependence of the LCST of P(DEGEA-co-AA), which were confirmed by dynamic light scattering and differential scanning calorimetry studies. Using the vial inversion test method, we mapped out the C-shaped sol-gel phase diagrams of the diblock copolymer in aqueous buffers in the moderate concentration range at three different pH values (3.24, 5.58, and 5.82, all measured at ~0 °C). While the upper temperature boundaries overlapped, the lower temperature boundary shifted upward and the critical gelation concentration increased with the increase of pH. The AA content in PTEGMA-b-P(DEGEA-co-AA) was found to have a significant effect on the pH dependence of T(sol-gel). For PTEGMA-b-P(DEGEA-co-AA) with a molar ratio of DEGEA to AA units of 100:10, the T(sol-gel) of its 25 wt % aqueous solution increased faster with the increase of pH than that of PTEGMA-b-P(DEGEA-co-AA) with a DEGEA-to-AA molar ratio of 100:5.2. © 2012 American Chemical Society

The application of silicon sol-gel technology to forensic blood substitute development: Mimicking aspects of whole human blood rheology.

PubMed

Stotesbury, Theresa; Illes, Mike; Wilson, Paul; Vreugdenhil, Andrew J

2017-01-01

Solution-gelation chemistry has promising applications in forensic synthetic blood substitute development. This research offers a silicon-based sol-gel approach to creating stable materials that share similar rheological properties to that of whole human blood samples. Room temperature, high water content, silicon sol-gels were created using the organosilane precursors 3-glycidoxypropyltrimethoxysilane and tetraethylorthosilicate along with various concentrations of filler and pigment. Shear-thinning non-Newtonian properties were observed within most formulations of the presented materials. The effects of colloidal concentration, temperature, age and filler addition on the viscosity of the sol-gels were investigated. SEM-EDS analysis was used to identify the behavior of the fillers within the film and support their inclusion for basic bloodstain pattern simulation. A final proposed candidate sol-gel was assessed using a previously reported passive drip simulation test on a hard, dry surface and passed. This works represents encouraging development in providing safe material alternatives to using whole human blood for forensic training and research. Copyright © 2016 Elsevier Ireland Ltd. All rights reserved.

Molecularly imprinted sol-gel nanofibers based solid phase microextraction coupled on-line with high performance liquid chromatography for selective determination of acesulfame.

PubMed

Moein, Mohammad Mahdi; Javanbakht, Mehran; Karimi, Mohammad; Akbari-Adergani, Behrouz

2015-03-01

Sol-gel based molecularly imprinted polymer (MIP) nanofiber was successfully fabricated by electrospinning technique on the surface of a stainless steel bar. The manufactured tool was applied for on-line selective solid phase microextraction (SPME) and determination of acesulfame (ACF) as an artificial sweetener with high performance liquid chromatography (HPLC). The selective ability of method for the extraction of ACF was investigated in the presence of some selected sweeteners such as saccharine (SCH), aspartame (ASP) and caffeine (CAF). Electrospinning of MIP sol-gel solution on the stainless steel bar provided an unbreakable sorbent with high thermal, mechanical, and chemical stability. Moreover, application of the MIP-SPME tool revealed a unique approach for the selective microextraction of the analyte in beverage samples. In this work, 3-(triethoxysilyl)-propylamine (TMSPA) was chosen as a precursor due to its ability to imprint the analyte by hydrogen bonding, Van der Walls, and dipole-dipole interactions. Nylon 6 was also added as a backbone and support for the precursor in which sol could greatly growth during the sol-gel process and makes the solution electrospinable. Various effective parameters in the extraction efficiency of the MIP-SPME tool such as loading time, flow rate, desorption time, selectivity, and the sample volume were evaluated. The linearity for the ACF in beverage sample was in the range of 0.78-100.5 ng mL(-1). Limit of detection (LOD) and quantification (LOQ) were 0.23 and 0.78 ng mL(-1) respectively. The RSD values (n=5) were all below 3.5%at the 20 ng mL(-1) level. Copyright © 2014 Elsevier B.V. All rights reserved.

Synthesis and characterization of nanosized MgxMn1-xFe2O4 ferrites by both sol-gel and thermal decomposition methods

NASA Astrophysics Data System (ADS)

De-León-Prado, Laura Elena; Cortés-Hernández, Dora Alicia; Almanza-Robles, José Manuel; Escobedo-Bocardo, José Concepción; Sánchez, Javier; Reyes-Rdz, Pamela Yajaira; Jasso-Terán, Rosario Argentina; Hurtado-López, Gilberto Francisco

2017-04-01

This work reports the synthesis of MgxMn1-xFe2O4 (x=0-1) nanoparticles by both sol-gel and thermal decomposition methods. In order to determine the effect of synthesis conditions on the crystal structure and magnetic properties of the ferrites, the synthesis was carried out varying some parameters, including composition. By both methods it was possible to obtain ferrites having a single crystalline phase with cubic inverse spinel structure and a behavior near to that of superparamagnetic materials. Saturation magnetization values were higher for materials synthesized by sol-gel. Furthermore, in both cases particles have a spherical-like morphology and nanometric sizes (11-15 nm). Therefore, these materials can be used as thermoseeds for the treatment of cancer by magnetic hyperthermia.

Reagentless D-sorbitol biosensor based on D-sorbitol dehydrogenase immobilized in a sol-gel carbon nanotubes-poly(methylene green) composite.

PubMed

Wang, Zhijie; Etienne, Mathieu; Urbanova, Veronika; Kohring, Gert-Wieland; Walcarius, Alain

2013-04-01

A reagentless D-sorbitol biosensor based on NAD-dependent D-sorbitol dehydrogenase (DSDH) immobilized in a sol-gel carbon nanotubes-poly(methylene green) composite has been developed. It was prepared by durably immobilizing the NAD(+) cofactor with DSDH in a sol-gel thin film on the surface of carbon nanotubes functionalized with poly(methylene green). This device enables selective determination of D-sorbitol at 0.2 V with a sensitivity of 8.7 μA mmol(-1) L cm(-2) and a detection limit of 0.11 mmol L(-1). Moreover, this biosensor has excellent operational stability upon continuous use in hydrodynamic conditions.

Epidemic models for phase transitions: application to a physical gel

NASA Astrophysics Data System (ADS)

Bilge, A. H.; Pekcan, O.; Kara, S.; Ogrenci, A. S.

2017-09-01

Carrageenan gels are characterized by reversible sol-gel and gel-sol transitions under cooling and heating processes and these transitions are approximated by generalized logistic growth curves. We express the transitions of carrageenan-water system, as a representative of reversible physical gels, in terms of a modified Susceptible-Infected-Susceptible epidemic model, as opposed to the Susceptible-Infected-Removed model used to represent the (irreversible) chemical gel formation in the previous work. We locate the gel point Tc of sol-gel and gel-sol transitions and we find that, for the sol-gel transition (cooling), Tc > Tsg (transition temperature), i.e. Tc is earlier in time for all carrageenan contents and moves forward in time and gets closer to Tsg as the carrageenan content increases. For the gel-sol transition (heating), Tc is relatively closer to Tgs; it is greater than Tgs, i.e. later in time for low carrageenan contents and moves backward as carrageenan content increases.

Infrared and Raman spectroscopic studies of tris-[3-(trimethoxysilyl)propyl] isocyanurate, its sol-gel process, and coating on aluminum and copper.

PubMed

Li, Ying-Sing; Church, Jeffrey S; Woodhead, Andrea L; Vecchio, Nicolas E; Yang, Johnny

2014-11-11

Tris-[3-(trimethoxysilyl)propyl] isocyanurate (TTPI) has been used as a precursor to prepare a sol using ethanol as the solvent under acidic conditions. The sol-gel was applied for the surface treatment of aluminum and copper. Infrared and Raman spectra have been recorded for pure TTPI and the TTPI sol, xerogel and TTPI sol-gel coated metals. From the vibrational spectra, TTPI is likely to have the C1 point group. Vibrational assignments are suggested based on group frequencies, the expected reactions in the sol-gel process and the vibrational studies of some related molecules. From the experimental infrared spectra of xerogels annealed at different temperatures and from the thermal-gravimetric analysis, it is found that the TTPI xerogel decomposes at around 450°C with silica being the major decomposition product. A cyclic voltammetric study of the metal electrodes coated with different concentrations of TTPI ranging from 5% to 42% (v/v) has shown that the films with high concentrations of sol would provide better corrosion protection for aluminum and copper. Copyright © 2014 Elsevier B.V. All rights reserved.

Sol-gel applications for ceramic membrane preparation

NASA Astrophysics Data System (ADS)

Erdem, I.

2017-02-01

Ceramic membranes possessing superior properties compared to polymeric membranes are more durable under severe working conditions and therefore their service life is longer. The ceramic membranes are composed of some layers. The support is the layer composed of coarser ceramic structure and responsible for mechanical durability under filtration pressure and it is prepared by consolidation of ceramic powders. The top layer is composed of a finer ceramic micro-structure mainly responsible for the separation of components present in the fluid to be filtered and sol-gel method is a versatile tool to prepare such a tailor-made ceramic filtration structure with finer pores. Depending on the type of filtration (e.g. micro-filtration, ultra-filtration, nano-filtration) aiming separation of components with different sizes, sols with different particulate sizes should be prepared and consolidated with varying precursors and preparation conditions. The coating of sol on the support layer and heat treatment application to have a stable ceramic micro-structure are also important steps determining the final properties of the top layer. Sol-gel method with various controllable parameters (e.g. precursor type, sol formation kinetics, heat treatment conditions) is a practical tool for the preparation of top layers of ceramic composite membranes with desired physicochemical properties.

Ultrapure glass optical waveguide: Development in microgravity by the sol gel process

NASA Technical Reports Server (NTRS)

Mukherjee, S. P.; Debsikdar, J. C.; Beam, T.

1983-01-01

The sol-gel process for the preparation of homogeneous gels in three binary oxide systems was investigated. The glass forming ability of certain compositions in the selected oxide systems (SiO-GeO2, GeO2-PbO, and SiO2-TiO2) were studied based on their potential importance in the design of optical waveguide at longer wavelengths.

Enhance the pyroelectricity of polyvinylidene fluoride by graphene-oxide doping.

PubMed

Hu, Yuh-Chung; Hsu, Wei-Li; Wang, Yi-Ta; Ho, Cheng-Tao; Chang, Pei-Zen

2014-04-16

The high quality properties and benefits of graphene-oxide have generated an active area of research where many investigations have shown potential applications in various technological fields. This paper proposes a methodology for enhancing the pyro-electricity of PVDF by graphene-oxide doping. The PVDF film with graphene-oxide is prepared by the sol-gel method. Firstly, PVDF and graphene-oxide powders are dispersed into dimethylformamide as solvent to form a sol solution. Secondly, the sol solution is deposited on a flexible ITO/PET substrate by spin-coating. Thirdly, the particles in the sol solution are polymerized through baking off the solvent to produce a gel in a state of a continuous network of PVDF and graphene-oxide. The final annealing process pyrolyzes the gel and form a β-phase PVDF film with graphene-oxide doping. A complete study on the process of the graphene oxide doping of PVDF is accomplished. Some key points about the process are addressed based on experiments. The solutions to some key issues are found in this work, such as the porosity of film, the annealing temperature limitation by the use of flexible PET substrate, and the concentrations of PVDF and graphene-oxide.

Thermodynamic analysis of sol-gel transition of gelatin in terms of water activity in various solutions.

PubMed

Miyawaki, Osato; Omote, Chiaki; Matsuhira, Keiko

2015-12-01

Sol-gel transition of gelatin was analyzed as a multisite stoichiometric reaction of a gelatin molecule with water and solute molecules. The equilibrium sol-gel transition temperature, Tt , was estimated from the average of gelation and melting temperature measured by differential scanning calorimetry. From Tt and the melting enthalpy, ΔHsol , the equilibrium sol-to-gel ratio was estimated by the van't Hoff equation. The reciprocal form of the Wyman-Tanford equation, which describes the sol-to-gel ratio as a function of water activity, was successfully applied to obtain a good linear relationship. From this analysis, the role of water activity on the sol-gel transition of gelatin was clearly explained and the contributions of hydration and solute binding to gelatin molecules were separately discussed in sol-gel transition. The general solution for the free energy for gel-stabilization in various solutions was obtained as a simple function of solute concentration. © 2015 Wiley Periodicals, Inc.

Sol-gel open tubular ODS columns with reversed electroosmotic flow for capillary electrochromatography.

PubMed

Hayes, J D; Malik, A

2001-03-01

Sol-gel chemistry was successfully used for the fabrication of open tubular columns with surface-bonded octadecylsilane (ODS) stationary-phase coating for capillary electrochromatography (OT-CEC). Following column preparations, a series of experiments were performed to investigate the performance of the sol-gel coated ODS columns in OT-CEC. The incorporation of N-octadecyldimethyl[3-(trimethoxysilyl)propyl]ammonium chloride as one of the sol-gel precursors played an important role in the electrochromatographic performance of the prepared columns. This chemical reagent possesses a chromatographically favorable, bonded ODS moiety, in conjunction with three methoxy groups allowing for sol-gel reactivity. In addition, a positively charged nitrogen atom is present in the molecular structure of this reagent and provides a positively charged capillary surface responsible for the reversed electroosmotic flow (EOF) in the columns during CEC operation. Comparative studies involving the EOF within such sol-gel ODS coated and uncoated capillaries were performed using acetonitrile and methanol as the organic modifiers in the mobile phase. The use of a deactivating reagent, phenyldimethylsilane, in the sol-gel solution was evaluated. Efficiency values of over 400,000 theoretical plates per meter were achieved in CEC on a 64 cm x 25 microm i.d. sol-gel ODS open tubular column. Test mixtures of polycyclic aromatic hydrocarbons, benzene derivatives, and aromatic aldehydes and ketones were used to evaluate the CEC performances of both nondeactivated and deactivated open tubular sol-gel columns. The effects of mobile-phase organic modifier contents and pH on EOF in such columns were evaluated. The prepared sol-gel ODS columns are characterized by switchable electroosmotic flow. A pH value of approximately 8.5 was found correspond to the isoelectric point for the prepared sol-gel ODS coatings.

Increasing the activity and enantioselectivity of lipases by sol-gel immobilization: further advancements of practical interest

NASA Astrophysics Data System (ADS)

Tielmann, Patrick; Kierkels, Hans; Zonta, Albin; Ilie, Adriana; Reetz, Manfred T.

2014-05-01

The entrapment of lipases in hydrophobic silicate matrices formed by sol-gel mediated hydrolysis of RSi(OCH3)3/Si(OCH3)4 as originally reported in 1996 has been improved over the years by a number of modifications. In the production of second-generation sol-gel lipase immobilizates, a variety of additives during the sol-gel process leads to increased activity and enhanced stereoselectivity in esterifying kinetic resolution. Recent advances in this type of lipase immobilization are reviewed here, in addition to new results regarding the sol-gel entrapment of the lipase from Burkholderia cepacia. It constitutes an excellent heterogeneous biocatalyst in the acylating kinetic resolution of two synthetically and industrially important chiral alcohols, rac-sulcatol and rac-trans-2-methoxycyclohexanol. The observation that the catalyst can be used 10 times in recycling experiments without losing its significant activity or enantioselectivity demonstrates the practical viability of the sol-gel approach.The entrapment of lipases in hydrophobic silicate matrices formed by sol-gel mediated hydrolysis of RSi(OCH3)3/Si(OCH3)4 as originally reported in 1996 has been improved over the years by a number of modifications. In the production of second-generation sol-gel lipase immobilizates, a variety of additives during the sol-gel process leads to increased activity and enhanced stereoselectivity in esterifying kinetic resolution. Recent advances in this type of lipase immobilization are reviewed here, in addition to new results regarding the sol-gel entrapment of the lipase from Burkholderia cepacia. It constitutes an excellent heterogeneous biocatalyst in the acylating kinetic resolution of two synthetically and industrially important chiral alcohols, rac-sulcatol and rac-trans-2-methoxycyclohexanol. The observation that the catalyst can be used 10 times in recycling experiments without losing its significant activity or enantioselectivity demonstrates the practical viability of the sol-gel approach. Dedicated to the pioneer of sol-gel enzyme immobilization, Professor David Avnir, on the occasion of his 65th birthday.

Structural and morphological characterization of anatase TiO 2 coating on χ-Alumina scale fiber fabricated by sol-gel dip-coating method

NASA Astrophysics Data System (ADS)

Nguyen, Hue Thi; Miao, Lei; Tanemura, Sakae; Tanemura, Masaki; Toh, Shoichi; Kaneko, Kenji; Kawasaki, Masahiro

2004-10-01

Anatase TiO 2 coatings 0.4 μm thick have been successfully fabricated by sol-gel dip-coating process on χ-Al 2O 3 fibers 100 μm by 10 cm long with a surface fish-scale. This was achieved by adjustment of the sol-gel parameters such as molar ratio of the precursors in TiO 2-sols, dip-coating time, drying duration in air, heating processes and number of cyclical repetitions of the process. Two samples were prepared using two sols containing different molar ratios of precursors. XRD, TEM, EDS and SEM characterization confirmed: (1) the similarity of the growth of anatase-TiO 2 from two sols under the optimal sol-gel parameters, (2) that the coatings are composed of aggregated crystallites of 10-25 nm in diameter, (3) the good compositional uniformity of Ti in the fabricated anatase-TiO 2 crystallites, (4) a surface covering ratio of anatase-TiO 2 around the fiber of at least 90%, and (5) that there is a good adherence of the fabricated anatase-TiO 2 layer on alumina fiber as evidenced by the lack of cracking and peeling off traces around the boundary between the coating and the fiber.

Method for fabrication of ceramic dielectric films on copper foils

DOEpatents

Ma, Beihai; Narayanan, Manoj; Dorris, Stephen E.; Balachandran, Uthamalingam

2017-06-14

The present invention provides copper substrate coated with a lead-lanthanum-zirconium-titanium (PLZT) ceramic film, which is prepared by a method comprising applying a layer of a sol-gel composition onto a copper foil. The sol-gel composition comprises a precursor of a ceramic material suspended in 2-methoxyethanol. The layer of sol-gel is then dried at a temperature up to about 250.degree. C. The dried layer is then pyrolyzed at a temperature in the range of about 300 to about 450.degree. C. to form a ceramic film from the ceramic precursor. The ceramic film is then crystallized at a temperature in the range of about 600 to about 750.degree. C. The drying, pyrolyzing and crystallizing are performed under a flowing stream of an inert gas.

Development of novel sol-gel coatings by chemically bonded ionic liquids for stir bar sorptive extraction--application for the determination of NSAIDS in real samples.

PubMed

Fan, Wenying; Mao, Xiangju; He, Man; Chen, Beibei; Hu, Bin

2014-11-01

In this work, a novel ionic liquid (IL) chemically bonded sol-gel coating was prepared for stir bar sorptive extraction (SBSE) of nonsteroidal anti-inflammatory drugs (NSAIDs) followed by high-performance liquid chromatography-ultraviolet detection (HPLC-UV). By using γ-(methacryloxypropyl)trimethoxysilane (KH-570) as a bridging agent, 1-allylimidazolium tetrafluoroborate ([AIM][BF4]) was chemically bonded onto the bare stir bar, and the prepared IL-bonded sol-gel stir bar coating showed higher extraction efficiency and better adsorption/desorption kinetics for target NSAIDs over other polydimethylsiloxane (PDMS)-based or monolithic stir bar coatings. The mechanical strength and durability (chemical/thermal stability) of the prepared IL-bonded sol-gel coating were excellent. The influencing factors of SBSE, such as sample pH, salt effect, stirring rate, extraction time, desorption solvent, and desorption time, were optimized, and the analytical performance of the developed SBSE-HPLC-UV method was evaluated under the optimized conditions. The limits of detection (LODs) of the proposed method for three NSAIDs were in the range of 0.23-0.31 μg L(-1), and the enrichment factors (EFs) were in the range of 51.6-56.3 (theoretical enrichment factor was 100). The reproducibility was also investigated at concentrations of 5, 20, and 100 μg L(-1), and the relative standard deviations (RSDs) were found to be less than 9.5, 7.5, and 7.6 %, respectively. The proposed method was successfully applied for the determination of NSAIDs in environmental water, urine, and milk samples.

Mimicking nature: Self-strengthening properties in a dental adhesive.

PubMed

Song, Linyong; Ye, Qiang; Ge, Xueping; Misra, Anil; Spencer, Paulette

2016-04-15

Chemical and enzymatic hydrolysis provoke a cascade of events that undermine methacrylate-based adhesives and the bond formed at the tooth/composite interface. Infiltration of noxious agents, e.g. enzymes, bacteria, and so forth, into the spaces created by the defective bond will ultimately lead to failure of the composite restoration. This paper reports a novel, synthetic resin that provides enhanced hydrolytic stability as a result of intrinsic reinforcement of the polymer network. The behavior of this novel resin, which contains γ-methacryloxyproyl trimethoxysilane (MPS) as its Si-based compound, is reminiscent of self-strengthening properties found in nature. The efforts in this paper are focused on two essential aspects: the visible-light irradiation induced (photoacid-induced) sol-gel reaction and the mechanism leading to intrinsic self-strengthening. The FTIR band at 2840cm(-1) corresponding to CH3 symmetric stretch in -Si-O-CH3 was used to evaluate the sol-gel reaction. Results from the real-time FTIR indicated that the newly developed resin showed a limited sol-gel reaction (<5%) during visible-light irradiation, but after 48h dark storage, the reaction was over 65%. The condensation of methoxysilane mainly occurred under wet conditions. The storage moduli and glass transition temperature of the copolymers increased in wet conditions with the increasing MPS content. The cumulative amounts of leached species decreased significantly when the MPS-containing adhesive was used. The results suggest that the polymethacrylate-based network, which formed first as a result of free radical initiated polymerization, retarded the photoacid-induced sol-gel reaction. The sol-gel reaction provided a persistent, intrinsic reinforcement of the polymer network in both neutral and acidic conditions. This behavior led to enhanced mechanical properties of the dental adhesives under conditions that simulate the wet, oral environment. A self-strengthening dental adhesive system was developed through a dual curing process, which involves the free radical photopolymerization followed by slow hydrolysis and condensation (photoacid-induced sol-gel reaction) of alkoxylsilane groups. The concept of "living" photoacid-induced sol-gel reaction with visible-light irradiation was confirmed in the polymer. The sol-gel reaction was retarded by the polymethacrylate network, which was generated first; the network extended the life and retained the activity of silanol groups. The self-strengthening behavior was evaluated by monitoring the mechanical properties of the hybrid copolymers under wet conditions. The present research demonstrates the sol-gel reaction in highly crosslinked network as a potentially powerful strategy to prolong the functional lifetime of engineered biomaterials in wet environments. Copyright © 2016 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.

Microporous alumina ceramic membranes

DOEpatents

Anderson, M.A.; Guangyao Sheng.

1993-05-04

Several methods are disclosed for the preparation microporous alumina ceramic membranes. For the first time, porous alumina membranes are made which have mean pore sizes less than 100 Angstroms and substantially no pores larger than that size. The methods are based on improved sol-gel techniques.

Microporous alumina ceramic membranes

DOEpatents

Anderson, Marc A.; Sheng, Guangyao

1993-01-01

Several methods are disclosed for the preparation microporous alumina ceramic membranes. For the first time, porous alumina membranes are made which have mean pore sizes less than 100 Angstroms and substantially no pores larger than that size. The methods are based on improved sol-gel techniques.

The low temperature synthesis, characterization and properties of ferroelectrics

NASA Astrophysics Data System (ADS)

Xu, Jie

2000-10-01

PZT 50:50 xerogels prepared by two different sol-gel routes crystallized in a similar fashion to give a mixture of tetragonal and rhombohedral at high temperature (1000°C). Both the diffraction and EXAFS data suggest that the compositional inhomogeneity of the samples prepared by the two routes is similar. The crystallization of CZT gels is complicated. Crystalline CaCO 3 was always detected in the dry gels regardless of the sample composition and preparation methods. At intermediate temperatures a fluorite related phase was always formed and it transformed to perovskite at higher temperatures. The EXAFS data suggest that perovskite CZT samples prepared using alkoxide sol-gel chemistry may not be random solid solutions. All the solution processed ZrTiO4 materials crystallized in the range 600--700°C. The KTN samples prepared using a conventional alkoxide sol-gel route crystallized completely to perovskite at lower temperatures than those prepared using prehydrolyzed precursors. The EXAFS data for the KTN samples prepared using a conventional alkoxide sol-gel route are consistent with a random distribution of tantalum and niobium in the solid solution. However, materials prepared using the inhomogeneous sol-gel route and by the direct reaction of mixed oxides were shown to be compositionally inhomogeneous. The heterogeneity could not be removed by regrinding and heating the mixed oxide samples several times. K2Ta4-xNbxO11 (x = 0, 2, 4) samples were prepared using alkoxide sol-gel chemistry and their crystallization was examined by powder X-ray diffraction. A Rietveld structure analysis of the pyrochlore formed from a gel with bulk composition K2Ta 2Nb2O11 indicated that it was rich in potassium relative to the bulk sample. On heating to high temperatures tetragonal tungsten bronzes were formed. A Rietveld analysis was also performed for K2Ta 2Nb2O11 with tetragonal tungsten bronze structure. The defect pyrochlores "AgTaO3" and GaTaO 3 were synthesized by ion-exchange using pyrochlore KTaO3 as a starting material. The structures of the pyrochlores were examined using the Rietveld method. The pyrochlore-to-perovskite transformations were also explored.

Sol-Gel deposition of inorganic alkoxides on wood surfaces to enhance their durability under exposure to sunlight and moisture

Treesearch

Mandla A. Tshabalala

2005-01-01

Wood specimens were coated with sol-gel deposits of aluminum isopropoxide, titanium isopropoxide, or zirconium propoxide in the presence of methytrimethoxysilane. Both zirconium propoxide and titanium isopropoxide sol-gel deposits reduced water sorption, whereas aluminum isopropoxide sol-gel deposit increased water sorption, compared with uncoated wood specimens. There...

A new strategy for surface modification of polysulfone membrane by in situ imprinted sol-gel method for the selective separation and screening of L-Tyrosine as a lung cancer biomarker.

PubMed

Moein, Mohammad Mahdi; Javanbakht, Mehran; Karimi, Mohammad; Akbari-adergani, Behrouz; Abdel-Rehim, Mohamed

2015-03-21

In this work, a novel method based on in situ molecularly imprinted sol-gel for the surface modification of a polysulfone membrane (PSM) was developed. A modified molecularly imprinted sol-gel polysulfone membrane (MSM) was placed in a homemade plastic tube and coupled on-line with LC/MS/MS for the selective extraction and screening of l-Tyrosine (Tyr) as a tentative lung cancer biomarker in human plasma samples. The existence of molecularly imprinted sol-gel layers on both sides of a PSM was examined using scanning electron microscopy (SEM). To evaluate the role of precursor in the extraction performance, repeatability, and selectivity of developed method, three precursors, 3-(propylmethacrylate) trimethoxysilane (P1), 3-(triethoxysilyl)-propylamine (P2), tetraethyl orthosilicate (P3), individually and together were used for treatment of PSM. Our investigation showed that a single precursor's route is more repeatable, straightforward, precise, accurate, and selective for the extraction of Tyr in plasma samples. Moreover, to achieve the best conditions and extraction efficiency, the effect of influential parameters, including the conditioning, washing, and elution of solvents, sample flow rate, loading time, desorption time, loading sample volume, salt effect, pH, and adsorption capacity for the most efficiently prepared membranes were truly investigated. The non-molecularly imprinted sol-gel polysulfone membrane (NSM) was prepared as a blank via the same process but in the absence of the Tyr. The LOD (S/N = 3/1) was 0.1 nmol L(-1) and the LOQ (S/N = 10/1) was 0.34 nmol L(-1) for Tyr in the plasma samples. The linearity for the Tyr was in the range of 0.34-2000 nmol L(-1) in the plasma samples. The coefficients of determination values were ≥0.998 for all runs. The extraction recovery was between 80%-85% for Tyr in the plasma samples. In addition, MSM could be used for up to 50 extractions without a significant change in recovery percentage.

Agar/gelatin bilayer gel matrix fabricated by simple thermo-responsive sol-gel transition method.

PubMed

Wang, Yifeng; Dong, Meng; Guo, Mengmeng; Wang, Xia; Zhou, Jing; Lei, Jian; Guo, Chuanhang; Qin, Chaoran

2017-08-01

We present a simple and environmentally-friendly method to generate an agar/gelatin bilayer gel matrix for further biomedical applications. In this method, the thermally responsive sol-gel transitions of agar and gelatin combined with the different transition temperatures are exquisitely employed to fabricate the agar/gelatin bilayer gel matrix and achieve separate loading for various materials (e.g., drugs, fluorescent materials, and nanoparticles). Importantly, the resulting bilayer gel matrix provides two different biopolymer environments (a polysaccharide environment vs a protein environment) with a well-defined border, which allows the loaded materials in different layers to retain their original properties (e.g., magnetism and fluorescence) and reduce mutual interference. In addition, the loaded materials in the bilayer gel matrix exhibit an interesting release behavior under the control of thermal stimuli. Consequently, the resulting agar/gelatin bilayer gel matrix is a promising candidate for biomedical applications in drug delivery, controlled release, fluorescence labeling, and bio-imaging. Copyright © 2017 Elsevier B.V. All rights reserved.

Anisotropic growth and formation mechanism investigation of 1D ZnO nanorods in spin-coating sol-gel process.

PubMed

Song, Yijian; Zheng, Maojun; Ma, Li; Shen, Wenzhong

2010-01-01

ZnO nanorods are fabricated on glass substrate by spin-coating sol-gel process using non-basic aged solution and annealing. Sample solutions reserved in room temperature for different time (one day, one month, two months and four months) are prepared for the experiment. The morphology study indicates that the aging time has direct influence on the final products. This is verified by the Transmission Electron Microscopy and Photon Correlation Spectroscopy study. Small crystalline nanoparticles would gradually nucleate and aggregate in the sol during the aging process. They act as nucleation site for the secondary crystal growth into nanorods during anneal. Both the size of crystalline particles in the sol and the size of nanorods will grow bigger as the aging time increases. The products' structure and optical property are further studied by X-ray diffraction spectroscopy, Photoluminescence and Raman spectroscopy. This work also helps to further clarify the formation mechanism of ZnO nanorods by solution-based method.

Sol-gel preparation of hydrophobic silica antireflective coatings with low refractive index by base/acid two-step catalysis.

PubMed

Cai, Shuang; Zhang, Yulu; Zhang, Hongli; Yan, Hongwei; Lv, Haibing; Jiang, Bo

2014-07-23

Hydrophobic antireflective coatings with a low refractive index were prepared via a base/acid-catalyzed two-step sol-gel process using tetraethylorthosilicate (TEOS) and methyltriethoxysilane (MTES) as precursors, respectively. The base-catalyzed hydrolysis of TEOS leads to the formation of a sol with spherical silica particles in the first step. In the second step, the acid-catalyzed MTES hydrolysis and condensation occur at the surface of the initial base-catalyzed spherical silica particles, which enlarge the silica particle size from 12.9 to 35.0 nm. By a dip-coating process, this hybrid sol gives an antireflective coating with a refractive index of about 1.15. Moreover, the water contact angles of the resulted coatings increase from 22.4 to 108.7° with the increases of MTES content, which affords the coatings an excellent hydrophobicity. A "core-shell" particle growth mechanism of the hybrid sol was proposed and the relationship between the microstructure of silica sols and the properties of AR coatings was investigated.

Sol-gel processing of bioactive glass nanoparticles: A review.

PubMed

Zheng, Kai; Boccaccini, Aldo R

2017-11-01

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. Copyright © 2017 Elsevier B.V. All rights reserved.

Magnetic response of gelatin ferrogels across the sol-gel transition: the influence of high energy crosslinking on thermal stability.

PubMed

Wisotzki, Emilia I; Eberbeck, Dietmar; Kratz, Harald; Mayr, Stefan G

2016-05-07

As emerging responsive materials, ferrogels have demonstrated significant potential for applications in areas of engineering to regenerative medicine. Promising techniques to study the behavior of magnetic nanoparticles (MNPs) in such matrices include magnetic particle spectroscopy (MPS) and magnetorelaxometry (MRX). This work investigated the magnetic response of gelatin-based ferrogels with increasing temperatures, before and after high energy crosslinking. The particle response was characterized by the nonlinear magnetization using MPS and quasistatic magnetization measurements as well as MRX to discriminate between Néel and Brownian relaxation mechanisms. The effective magnetic response of MNPs in gelatin was suppressed, indicating that the magnetization of the ferrogels was strongly influenced by competing dipole-dipole interactions. Significant changes in the magnetic behavior were observed across the gelatin sol-gel transition, as influenced by the matrix viscosity. These relaxation processes were modeled by Fourier transformation of the Langevin function, combined with a Debye term for the nonlinear magnetic response, for single core MNPs embedded in matrices of changing viscosities. Using high energy electron irradiation as a crosslinking method, modified ferrogels exhibited thermal stability on a range of timescales. However, MRX relaxation times revealed a slight softening around the gelatin sol-gel transition felt by the smallest particles, demonstrating a high sensitivity to observe local changes in the viscoelasticity. Overall, MPS and MRX functioned as non-contact methods to observe changes in the nanorheology around the native sol-gel transition and in crosslinked ferrogels, as well as provided an understanding of how MNPs were integrated into and influenced by the surrounding matrix.

Detection of Hydrofluoric Acid by a SiO2 Sol-Gel Coating Fiber-Optic Probe Based on Reflection-Based Localized Surface Plasmon Resonance

PubMed Central

Chen, I-Cherng; Lin, Shiu-Shiung; Lin, Tsao-Jen; Du, Je-Kang

2011-01-01

A novel fiber-optic probe based on reflection-based localized surface plasmon resonance (LSPR) was developed to quantify the concentration of hydrofluoric acid (HF) in aqueous solutions. The LSPR sensor was constructed with a gold nanoparticle-modified PMMA fiber, integrated with a SiO2 sol-gel coating. This fiber-sensor was utilized to assess the relationship between HF concentration and SiO2 sol-gel layer etching reduction. The results demonstrated the LSPR sensor was capable of detecting HF-related erosion of hydrofluoric acid solutions of concentrations ranging from 1% to 5% using Relative RI Change Rates. The development of the LSPR sensor constitutes the basis of a detector with significant sensitivity for practical use in monitoring HF solution concentrations. PMID:22319388

Sol-Gel Synthesis of Non-Silica Monolithic Materials

PubMed Central

Gaweł, Bartłomiej; Gaweł, Kamila; Øye, Gisle

2010-01-01

Monolithic materials have become very popular because of various applications, especially within chromatography and catalysis. Large surface areas and multimodal porosities are great advantages for these applications. New sol-gel preparation methods utilizing phase separation or nanocasting have opened the possibility for preparing materials of other oxides than silica. In this review, we present different synthesis methods for inorganic, non-silica monolithic materials. Some examples of application of the materials are also included.

Microwave sintering of sol-gel derived abrasive grain

DOEpatents

Plovnick, Ross; Celikkaya, Ahmet; Blake, Rodger D.

1997-01-01

A method is provided for making microwave-sintered, free flowing alpha alumina-based ceramic abrasive grain, under conditions effective to couple microwaves with calcined alpha alumina-based abrasive gain precursor and sinter it at a temperature of at least about 1150.degree. C.

Sintering and microstructure of silicon carbide ceramic with Y3Al5O12 added by sol-gel method*

PubMed Central

Guo, Xing-zhong; Yang, Hui

2005-01-01

Silicon carbide (SiC) ceramic with YAG (Y3Al5O12) additive added by sol-gel method was liquid-phase sintered at different sintering temperatures, and the sintering mechanism and microstructural characteristics of resulting silicon carbide ceramics were analyzed by X-ray diffraction (XRD), scanning electron microscopy (SEM) and elemental distribution of surface (EDS). YAG (yttrium aluminum garnet) phase formed before the sintering and its uniform distribution in the SiC/YAG composite powder decreased the sintering temperature and improved the densification of SiC ceramic. The suitable sintering temperature was 1860 °C with the specimen sintered at this temperature having superior sintering and mechanical properties, smaller crystal size and fewer microstructure defects. Three characteristics of improved toughness of SiC ceramic with YAG added by sol-gel method were microstructural densification, main-crack deflection and crystal ‘bridging’. PMID:15682507

Synthesis and Microstructure of Highly Oriented PbTiO3 Thin Films Prepared by a Sol-Gel Method

DTIC Science & Technology

1989-06-01

lead acetate with titanium isopropoxide * in 2-methoxyethanol,* in a method similar to that reported by Gurkovitch and Blum." The resulting yellow-gold...orientation by a sol-gel processing method. EXPERIMENTAL Precursor Solution Preparation Stock solutions of complex Pb-Ti alkoxide were prepared by reacting... solution had an equivalent PbTiO 3 concentration of approximately 66 wt%. The alkoxide solutions were handled as moisture-sensitive reagents and, as

Oxide Ceramic Fibers by the Sol-Gel Methods

DTIC Science & Technology

1989-02-10

AFWAL-TR-88-4199 OXIDE CERAMIC FIBERS BY THE SOL-GEL METHOD J . D. Mackenzie If) K. Ono The Regents of the University of California (Los Angeles) V...METHOD 12. PERSONAL AUTHOR(S) J . D. MACKENZIE, K. ONO 13a. TYPE OF REPORT 13b. TIME COVERED 114. DATE OF REPORT (Year,Month, Day) 15. PAGE COUNT...to Mary Colby who performed, under the direction of J . D. Mackenzie, the bulk of the experimental studies and contributed extensively to the

Comparative study of RF reactive magnetron sputtering and sol-gel deposition of UV induced superhydrophilic TiOx thin films

NASA Astrophysics Data System (ADS)

Vrakatseli, V. E.; Amanatides, E.; Mataras, D.

2016-03-01

TiOx and TiOx-like thin films were deposited on PEEK (Polyether ether ketone) substrates by low-temperature RF reactive magnetron sputtering and the sol-gel method. The resulting films were compared in terms of their properties and photoinduced hydrophilicity. Both techniques resulted in uniform films with good adhesion that can be switched to superhydrophilic after exposure to UVA radiation for similar time periods. In addition, the sputtered films can also be activated and switched to superhydrophilic by natural sunlight due to the higher absorption in the visible spectrum compared to the sol-gel films. On the other hand, the as deposited sol-films remain relatively hydrophilic for a longer time in dark compared to the sputtered film due to the differences in the morphology and the porosity of the two materials. Thus, depending on the application, either method can be used in order to achieve the desirable TiOx properties.

Improvement of the titanium implant biological properties by coating with poly (ε-caprolactone)-based hybrid nanocomposites synthesized via sol-gel

DOE Office of Scientific and Technical Information (OSTI.GOV)

Catauro, Michelina; Bollino, Flavia; Papale, Ferdinando

When bioactive coatings are applied to medical implants by means of sol-gel dip coating technique, the biological proprieties of the implant surface can be modified to match the properties of the surrounding tissues. In this study organo-inorganic nanocomposites materials were synthesized via sol-gel. They consisted of an inorganic zirconium-based and silica-based matrix, in which a biodegradable polymer (the poly-ε-caprolactone, PCL) was incorporated in different weight percentages. The synthesized materials, in sol phase, were used to dip-coat a substrate of commercially pure titanium grade 4 (CP Ti gr. 4) in order to improve its biological properties. A microstructural analysis of themore » obtained films was carried out by scanning electron microscopy (SEM) and attenuated total reflectance (ATR) Fourier transform infrared spectroscopy (FT-IR). Biological proprieties of the coated substrates were investigated by means of in vitro tests.« less

Low temperature and UV curable sol-gel coatings for long lasting optical fiber biosensors

NASA Astrophysics Data System (ADS)

Otaduy, D.; Villar, A.; Gomez-Herrero, E.; Goitandia, A. M.; Gorritxategi, E.; Quintana, I.

2010-04-01

The use of optical fibers as sensing element is increasing in clinical, pharmaceutical and industrial applications. Excellent light delivery, long interaction length, low cost and ability not only to excite the target molecules but also to capture the emitted light from the targets are the hallmarks of optical fiber as biosensors. In biosensors based on fiber optics the interaction with the analyte can occur within an element of the optical fiber. One of the techniques for this kind of biosensors is to remove the fiber optic cladding and substitute it for biological coatings that will interact with the parameter to sensorize. The deposition of these layers can be made by sol-gel technology. The sol-gel technology is being increasingly used mainly due to the high versatility to tailor their optical features. Incorporation of suitable chemical and biochemical sensing agents have allowed determining pH, gases, and biochemical species, among others. Nonetheless, the relatively high processing temperatures and short lifetime values mean severe drawbacks for a successful exploitation of sol-gel based coated optical fibres. With regard to the latter, herein we present the design, preparation and characterization of novel sol-gel coated optical fibres. Low temperature and UV curable coating formulations were optimized to achieve a good adhesion and optical performance. The UV photopolymerizable formulation was comprised by glycidoxypropyltrimethoxysilane (GLYMO), Tetraethylorthosilicate (TEOS) and an initiator. While the thermoset coating was prepared by using 3-aminopropyltrimethoxysilane, GLYMO, and TEOS as main reagents. Both curable sol-gel coated fibres were analysed by FTIR, SEM and optical characterization. Furthermore, in the present work a new technique for silica cladding removal has been developed by ultra-short pulses laser processing, getting good dimensional accuracy and surface integrity.

rhEGF-containing thermosensitive and mucoadhesive polymeric sol-gel for endoscopic treatment of gastric ulcer and bleeding.

PubMed

Maeng, Jin Hee; So, Jung Won; Kim, Jungju; Kim, In Ae; Jung, Ji Hoon; Min, Kyunghyun; Lee, Don Haeng; Yang, Su-Geun

2014-03-01

Gastrointestinal endoscopy is a standard diagnostic tool for gastrointestinal ulcers and cancer. In this study, we have developed recombinant human epidermal growth factor-containing ulcer-coating polymeric sol-gel for endoscopic application. Chitosan and pluronic F127 were employed for their thermoresponsive and bioadhesive properties. At temperatures below 21, polymeric sol-gel remains liquid during endoscopic application and transforms to gel at body temperature after application on ulcers. In an in vitro cellular wounding assay, recombinant human epidermal growth factor sol-gel significantly enhanced the cell migration and decreased the wounding area (68%) compared to nontreated, recombinant human epidermal growth factor solution, and sol-gel without recombinant human epidermal growth factor (42, 49, and 32 % decreased at day 1). The in vivo ulcer-healing study was performed in an acetic acid-induced gastric ulcer rat model and proved that our recombinant human epidermal growth factor endoscopic sol-gel facilitated the ulcer-healing process more efficiently than the other treatments. Ulcer sizes in the recombinant human epidermal growth factor sol-gel group were decreased 2.9- and 2.1-fold compared with those in the nontreated group on days 1 and 3 after ulceration, respectively. The mucosal thickness in the recombinant human epidermal growth factor sol-gel group was significantly increased compared to that in the nontreated group (3.2- and 6.9-fold on days 1 and 3 after ulceration, respectively). In a gastric retention study, recombinant human epidermal growth factor sol-gel stayed on the gastric mucosa more than 2 h after application. The present study suggests that recombinant human epidermal growth factor sol-gel is a prospective candidate for treating gastric ulcers via endoscopic application.

Controlled release of vancomycin from thin sol-gel films on implant surfaces successfully controls osteomyelitis.

PubMed

Adams, Christopher S; Antoci, Valentin; Harrison, Gerald; Patal, Payal; Freeman, Terry A; Shapiro, Irving M; Parvizi, Javad; Hickok, Noreen J; Radin, Shula; Ducheyne, Paul

2009-06-01

Peri-prosthetic infection remains a serious complication of joint replacement surgery. Herein, we demonstrate that a vancomycin-containing sol-gel film on Ti alloy rods can successfully treat bacterial infections in an animal model. The vancomycin-containing sol-gel films exhibited predictable release kinetics, while significantly inhibiting S. aureus adhesion. When evaluated in a rat osteomyelitis model, microbiological analysis indicated that the vancomycin-containing sol-gel film caused a profound decrease in S. aureus number. Radiologically, while the control side showed extensive bone degradation, including abscesses and an extensive periosteal reaction, rods coated with the vancomycin-containing sol-gel film resulted in minimal signs of infection. MicroCT analysis confirmed the radiological results, while demonstrating that the vancomycin-containing sol-gel film significantly protected dense bone from resorption and minimized remodeling. These results clearly demonstrate that this novel thin sol-gel technology can be used for the targeted delivery of antibiotics for the treatment of periprosthetic as well as other bone infections. Copyright 2008 Orthopaedic Research Society

Porosity and Variations in Microgravity Aerogel Nano-Structures. 2; New Laser Speckle Characterization Methods

NASA Technical Reports Server (NTRS)

Hunt, A. J.; Ayers, M. R.; Sibille, L.; Smith, D. D.

2001-01-01

The transition from sol to gel is a process that is critical to the properties of engineered nanomaterials, but one with few available techniques for observing the dynamic processes occurring during the evolution of the gel network. Specifically, the observation of various cluster aggregation models, such as diffusion-limited and reaction-limited cluster growth can be quite difficult. This can be rather important as the actual aggregation model can dramatically influence the mechanical properties of gels, and is significantly affected by the presence of convective flows, or their absence in microgravity. We have developed two new non-intrusive optical methods for observing the aggregation processes within gels in real time. These make use of the dynamic behavior of laser speckle patterns produced when an intense laser source is passed through a gelling sol. The first method is a simplified time-correlation measurement, where the speckle pattern is observed using a CCD camera and information on the movement of the scattering objects is readily apparent. This approach is extremely sensitive to minute variations in the flow field as the observed speckle pattern is a diffraction-based image, and is therefore sensitive to motions within the sol on the order of the wavelength of the probing light. Additionally, this method has proven useful in determining a precise time for the gel-point, an event often difficult to measure. Monitoring the evolution of contrast within the speckle field is another method that has proven useful for studying aeration. In this case, speckle contrast is dependent upon the size (correlation length) and number of scattering centers, increasing with increasing size, and decreasing with increasing numbers. The dynamic behavior of cluster growth in gels causes both of these to change simultaneously with time, the exact rate of which is determined by the specific aggregation model involved. Actual growth processes can now be observed, and the effects of varying gravity fields on the growth processes qualitatively described. Results on preliminary ground-based measurements have been obtained.

Hybrid Thin Film Organosilica Sol-Gel Coatings To Support Neuronal Growth and Limit Astrocyte Growth.

PubMed

Capeletti, Larissa Brentano; Cardoso, Mateus Borba; Dos Santos, João Henrique Zimnoch; He, Wei

2016-10-07

Thin films of silica prepared by a sol-gel process are becoming a feasible coating option for surface modification of implantable neural sensors without imposing adverse effects on the devices' electrical properties. In order to advance the application of such silica-based coatings in the context of neural interfacing, the characteristics of silica sol-gel are further tailored to gain active control of interactions between cells and the coating materials. By incorporating various readily available organotrialkoxysilanes carrying distinct organic functional groups during the sol-gel process, a library of hybrid organosilica coatings is developed and investigated. In vitro neural cultures using PC12 cells and primary cortical neurons both reveal that, among these different types of hybrid organosilica, the introduction of aminopropyl groups drastically transforms the silica into robust neural permissive substrate, supporting neuron adhesion and neurite outgrowth. Moreover, when this organosilica is cultured with astrocytes, a key type of glial cells responsible for glial scar response toward neural implants, such cell growth promoting effect is not observed. These findings highlight the potential of organo-group-bearing silica sol-gel to function as advanced coating materials to selectively modulate cell response and promote neural integration with implantable sensing devices.

Innovative Formulation Combining Al, Zr and Si Precursors to Obtain Anticorrosion Hybrid Sol-Gel Coating.

PubMed

Genet, Clément; Menu, Marie-Joëlle; Gavard, Olivier; Ansart, Florence; Gressier, Marie; Montpellaz, Robin

2018-05-10

The aim of our study is to improve the aluminium alloy corrosion resistance with Organic-Inorganic Hybrid (OIH) sol-gel coating. Coatings are obtained from unusual formulation with precursors mixing: glycidoxypropyltrimethoxysilane (GPTMS), zirconium (IV) propoxide (TPOZ) and aluminium tri-sec-butoxide (ASB). This formulation was characterized and compared with sol formulations GPTMS/TPOZ and GPTMS/ASB. In each formulation, a corrosion inhibitor, cerium (III) nitrate hexahydrate, is employed to improve the corrosion performance. Coatings obtained from sol based on GPTMS/TPOZ/ASB have good anti-corrosion performances with Natural Salt Spray (NSS) resistance of 500 h for a thickness lower than 4 µm. Contact angle measurement showed a coating hydrophobic behaviour. To understand these performances, nuclear magnetic resonance (NMR) analyses were performed, results make sol-gel coating condensation evident and are in very good agreement with previous results.

Electrochemical Study and Characterization of an Amperometric Biosensor Based on the Immobilization of Laccase in a Nanostructure of TiO₂ Synthesized by the Sol-Gel Method.

PubMed

Romero-Arcos, Mariana; Garnica-Romo, Ma Guadalupe; Martínez-Flores, Héctor Eduardo

2016-07-07

Laccase amperometric biosensors were developed to detect the catechol compound. The laccase enzyme (LAC) immobilization was performed on nanostructures of (a) titania (TiO₂); (b) titania/Nafion (TiO₂/NAF) (both immobilized by the sol-gel method) and a third nanostructure, which consisted of a single biosensor composite of Nafion and laccase enzyme denoted as NAF/LAC. The Nafion was deposited on a graphite electrode and used to avoid "cracking" on the matrix. The TiO₂ particle size was an average of 66 nm. FTIR spectroscopy vibration modes of different composites were determined. The electrochemical behavior of the biosensor was studied using electrochemical spectroscopy (EIS) and cyclic voltammetry (CV). The biosensor based on TiO₂/NAF/LAC presented the best electro-chemical properties with regard to sensitivity, stability and detection limit after a period of 22 days.

Resistive switching memory devices composed of binary transition metal oxides using sol-gel chemistry.

PubMed

Lee, Chanwoo; Kim, Inpyo; Choi, Wonsup; Shin, Hyunjung; Cho, Jinhan

2009-04-21

We describe a novel and versatile approach for preparing resistive switching memory devices based on binary transition metal oxides (TMOs). Titanium isopropoxide (TIPP) was spin-coated onto platinum (Pt)-coated silicon substrates using a sol-gel process. The sol-gel-derived layer was converted into a TiO2 film by thermal annealing. A top electrode (Ag electrode) was then coated onto the TiO2 films to complete device fabrication. When an external bias was applied to the devices, a switching phenomenon independent of the voltage polarity (i.e., unipolar switching) was observed at low operating voltages (about 0.6 VRESET and 1.4 VSET). In addition, it was confirmed that the electrical properties (i.e., retention time, cycling test and switching speed) of the sol-gel-derived devices were comparable to those of vacuum deposited devices. This approach can be extended to a variety of binary TMOs such as niobium oxides. The reported approach offers new opportunities for preparing the binary TMO-based resistive switching memory devices allowing a facile solution processing.

Synthesis and Study of Gel Calcined Cd-Sn Oxide Nanocomposites

NASA Astrophysics Data System (ADS)

De, Arijit; Kundu, Susmita

2016-07-01

Cd-Sn oxide nanocomposites were synthesized by sol-gel method from precursor sol containing Cd:Sn = 2:1 and 1:1 mol ratio. Instead of coprecipitation, a simple novel gel calcination route was followed. Cd (NO3)2. 4H2O and SnCl4. 5H2O were used as starting materials. Gel was calcined at 1050 °C for 2 h to obtain nanocomposites. XRD analysis reveals the presence of orthorhombic, cubic Cd2SnO4 along with orthorhombic, hexagonal CdSnO3 phases in both the composites. SEM and TEM studies indicate the development of nanocomposites of different shapes suggesting different degrees of polymerization in precursor sol of different composition. UV-Vis absorption spectra show a blue shift for both the composites compared to bulk values. Decrease of polarization with frequency, dipole contribution to the polarization, and more sensitivity to ethanol vapor were observed for the nanocomposite derived from precursor sol containing Cd:Sn = 2:1 mol ratio.

Sol-gel titania-coated needles for solid phase dynamic extraction-GC/MS analysis of desomorphine and desocodeine.

PubMed

Su, Chi-Ju; Srimurugan, Sankarewaran; Chen, Chinpiao; Shu, Hun-Chi

2011-01-01

Novel sol-gel titania film coated needles for solid-phase dynamic extraction (SPDE)-GC/MS analysis of desomorphine and desocodeine are described. The high thermal stability of titania film permits efficient extraction and analysis of poorly volatile opiate drugs. The influences of sol-gel reaction time, coating layer, extraction and desorption time and temperature on the SPDE needle performance were investigated. The deuterium labeled internal standard was introduced either during the extraction of analyte or directly injected to GC after the extraction process. The latter method was shown to be more sensitive for the analysis of water and urine samples containing opiate drugs. The proposed conditions provided a wide linear range (from 5-5000 ppb), and satisfactory linearity, with R(2) values from 0.9958 to 0.9999, and prominent sensitivity, LOQs (1.0-5.0 ng/g). The sol-gel titania film coated needle with SPDE-GC/MS will be a promising technique for desomorphine and desocodeine analysis in urine.

Development of novel biocompatible hybrid nanocomposites based on polyurethane-silica prepared by sol gel process.

PubMed

Rashti, Ali; Yahyaei, Hossein; Firoozi, Saman; Ramezani, Sara; Rahiminejad, Ali; Karimi, Roya; Farzaneh, Khadijeh; Mohseni, Mohsen; Ghanbari, Hossein

2016-12-01

Due to high biocompatibility, polyurethane has found many applications, particularly in development of biomedical devices. A new nanocomposite based on thermoset polyurethane and silica nanoparticles was synthesized using sol-gel method. Sol-gel process was fulfilled in two acidic and basic conditions by using tetraethylorthosilicate (TEOS) and trimethoxyisocyanatesilane as precursors. The hybrid films characterized for mechanical and surface properties using tensile strength, contact angle, ATR-FTIR and scanning electron microscopy. Biocompatibility and cytotoxicity of the hybrids were assessed using standard MTT, LDH and TUNEL assays. The results revealed that incorporation of silica nanoparticles was significantly improved tensile strength and mechanical properties of the hybrids. Based on the contact angle results, silica nanoparticles increased hydrophilicity of the hybrids. Biocompatibility by using human lung epithelial cell line (MRC-5) demonstrated that the hybrids were significantly less cytotoxic compared to pristine polymer as tested by MTT and LDH assays. TUNEL assay revealed no signs of apoptosis in all tested samples. The results of this study demonstrated that incorporation of silica nanoparticles into polyurethane lead to the enhancement of biocompatibility, indicating that these hybrids could potentially be used in biomedical field in particular as a new coating for medical implants. Copyright © 2016 Elsevier B.V. All rights reserved.

The gelation influence on diffusion and conductivity enhancement effect in renewable ionic gels based on a LMWG.

PubMed

Bielejewski, M; Rachocki, A; Kaszyńska, J; Tritt-Goc, J

2018-02-21

This paper reports the interdisciplinary study on molecular dynamics, ionic interactions and electrical conductivity in a quaternary ammonium salt (TMABr) ionogel based on a low molecular weight gelator (LMWG) in a wide range of electrolyte molar concentrations. The thermal scanning conductometry (TSC) was used to investigate the electric properties of the ionogels. The prepared TMABr/H 2 O/LMWG ionogel exhibits better ion transport properties than the dissociated TMA + cation in solution. The enhanced ionic conductivity effect (EICE) was observed in the concentration range of the TMABr salt up to 1 M. To investigate the transport properties of the TMA + cation and solvent molecules in the gel and sol phase, the NMR diffusiometry method was used. The field-cycling relaxometry method (FFC NMR) was applied to study the local motions of the electrolyte at the surface of the gelator matrix. On the basis of the obtained data, the higher ionic conductivity observed in the gel phase has been related to the microstructure of the gel matrix. The possible explanation for the origin of this effect has been given. The investigated system is a thermally reversible physical gel, all registered data were reproducible upon transforming the sample from gel to sol and back to the gel state, confirming the enhancement effect as a permanent property of the investigated ionogels. Therefore, the EICE has been proposed to be used as an internal sensor to monitor the condition of the ionogel phase, thus making them smart materials.

Ultrapure glass optical waveguide development in microgravity by the sol-gel process

NASA Technical Reports Server (NTRS)

1982-01-01

Containerless melting of glasses in space for the preparation of ultrapure homogeneous glass for optical waveguides is discussed. The homogenization of the glass using conventional raw materials is normally achieved on Earth either by the gravity induced convection currents or by the mechanical stirring of the melt. Because of the absence of gravity induced convection currents, the homogenization of glass using convectional raw materials is difficult in the space environment. Multicomponent, homogeneous, noncrystalline oxide gels can be prepared by the sol-gel process and these gels are promising starting materials for melting glasses in the space environment. The sol-gel process is based on the polymerization reaction of alkoxysilane with other metal alkoxy compounds or suitable metal salts. Many of the alkoxysilanes or other metal alkoxides are liquids and thus can be purified by distillation.

Investigation of Annealing Temperature on Copper Oxide Thin Films Using Sol-Gel Spin Coating Technique

NASA Astrophysics Data System (ADS)

Hashim, H.; Samat, S. F. A.; Shariffudin, S. S.; Saad, P. S. M.

2018-03-01

Copper (II) Oxide or cupric oxide (CuO) is one of the well-known materials studied for thin films applications. This paper was studied on the effect of annealing temperature to CuO thin films using sol-gel method and spin coating technique. The solution was prepared by sol-gel method and the thin films were synthesized at various temperatures from 500°C to 700°C that deposited onto the quartz substrates. After the annealing process, the thin films were uniform and brownish black in colour. The measurements were performed by atomic force microscopy (AFM), surface profiler (SP), two-point probe and Ultraviolet-visible (UV-Vis-NIR) spectrometer. From the optical measurement, the band gap was estimated to be 1.44eV for sample annealed at 550°C.

Solventless sol-gel chemistry through ring-opening polymerization of bridged disilaoxacyclopentanes

DOE Office of Scientific and Technical Information (OSTI.GOV)

RAHIMIAN,KAMYAR; LOY,DOUGLAS A.

2000-04-04

Disilaoxacyclopentanes have proven to be excellent precursors to sol-gel type materials. These materials have shown promise as precursors for encapsulation and microelectronics applications. The polymers are highly crosslinked and are structurally similar to traditional sol-gels, but unlike typical sol-gels they are prepared without the use of solvents and water, they have low VOC's and show little shrinkage during processing.

Ionogel Electrolytes through Sol-Gel Processing

NASA Astrophysics Data System (ADS)

Horowitz, Ariel I.

Electrical energy needs have intensified due to the ubiquity of personal electronics, the decarbonization of energy services through electrification, and the use of intermittent renewable energy sources. Despite developments in mechanical and thermal methods, electrochemical technologies are the most convenient and effective means of storing electrical energy. These technologies include both electrochemical cells, commonly called batteries, and electrochemical double-layer capacitors, or "supercapacitors", which store energy electrostatically. Both device types require an ion-conducting electrolyte. Current devices use solutions of complex salts in organic solvents, leading to both toxicity and flammability concerns. These drawbacks can be avoided by replacing conventional electrolytes with room-temperature molten salts, known as ionic liquids (ILs). ILs are non-volatile, non-flammable, and offer high conductivity and good electrochemical stability. Device mass can be reduced by combining ILs with a solid scaffold material to form an "ionogel," further improving performance metrics. In this work, sol-gel chemistry is explored as a means of forming ionogel electrolytes. Sol-gel chemistry is a solution-based, industrially-relevant, well-studied technique by which solids such as silica can be formed in situ. Previous works used a simple acid-catalyzed sol-gel reaction to create brittle, glassy ionogels. Here, both the range of products that can be accomplished through sol-gel processing and the understanding of interactions between ILs and the sol-gel reaction network are greatly expanded. This work introduces novel ionogel materials, including soft and compliant silica-supported ionogels and PDMS-supported ionogels. The impacts of the reactive formulation, IL identity, and casting time are detailed. It is demonstrated that variations in formulation can lead to rapid gelation and open pore structures in the silica scaffold or slow gelation and more dense silica morphologies. The IL identity is shown to have an impact on the apparent strength of the acid catalyst, leading to significant shifts in gelation time. Delayed casting is proven to be an optimal technique for avoiding pore blockage when combining ionogels with high surface area electrodes for supercapacitor applications. Finally, a simple recycling process is proposed, establishing that ILs can be easily reclaimed from silica-supported ionogels and reused, thereby validating the reputation of ILs as "green" materials.

Sol-gel-graphene-based fabric-phase sorptive extraction for cow and human breast milk sample cleanup for screening bisphenol A and residual dental restorative material before analysis by HPLC with diode array detection.

PubMed

Samanidou, Victoria; Filippou, Olga; Marinou, Eirini; Kabir, Abuzar; Furton, Kenneth G

2017-06-01

Fabric-phase sorptive extraction has already been recognized as a simple and green alternative to the conventional sorbent-based sorptive microextraction techniques, using hybrid organic-inorganic sorbent coatings chemically bonded to a flexible fabric surface. Herein, we have investigated the synergistic combination of the advanced material properties offered by sol-gel graphene sorbent and the simplicity of Fabric phase sorptive extraction approach in selectively extracting bisphenol A and residual monomers including bisphenol A glycerolatedimethacrylate, urethane dimethacrylate, and triethylene glycol dimethacrylate derived dental restorative materials from cow and human breast milk samples. Different coatings were evaluated. Final method development employed sol-gel graphene coated media. The main experimental parameters influencing extraction of the compounds, such as sorbent chemistry used, sample loading conditions, elution solvent, sorption stirring time, elution time, impact of protein precipitation, amount of sample, and matrix effect, were investigated and optimized. Absolute recovery values from standard solutions were 50% for bisphenol A, 78% for T triethylene glycol dimethacrylate, 110% for urethane dimethacrylate, and 103% for bisphenol A glycerolatedimethacrylate, while respective absolute recovery values from milk were 30, 52, 104, and 42%. Method validation was performed according to European Decision 657/2002/EC in terms of selectivity, sensitivity, linearity, accuracy, and precision. © 2017 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Effect of complexing agents on the electrochemical performance of LiFePO4/C prepared by sol-gel method

PubMed Central

2012-01-01

LiFePO4/C is synthesized via sol-gel method using Fe3+ as iron sources and different complexing agents, followed by sintering at high temperature for crystallization. The amount of carbon in these composites is less than 6.8 wt.%, and the X-ray diffraction experiment confirms that all samples are pure single phase indexed with the orthorhombic Pnma space group. The particle size of the LiFePO4/C synthesized by acetic acid as a complexing agent is very fine with a size of 200 nm. The electrochemical performance of this material, including reversible capacity, cycle number, and charge-discharge characteristics, is better than those of LiFePO4/C synthesized by other complexing agents. The cell of this sample can deliver a discharge capacity of 161.1 mAh g-1 at the first cycle. After 30 cycles, the capacity decreases to 157.5 mAh g-1, and the capacity fading rate is 2.2%. The mechanism is studied to explain the effect of a complexing agent on the synthesis of LiFePO4/C by sol-gel method. The results show that the complexing agent with a low stability constant may be proper for the synthetic process of LiFePO4/C via sol-gel method. PMID:22221711

Effect of complexing agents on the electrochemical performance of LiFePO4/C prepared by sol-gel method

NASA Astrophysics Data System (ADS)

Yang, Rong; Kang, Erwei; Jiang, Bailing; Ahn, Jou-Hyeon

2012-01-01

LiFePO4/C is synthesized via sol-gel method using Fe3+ as iron sources and different complexing agents, followed by sintering at high temperature for crystallization. The amount of carbon in these composites is less than 6.8 wt.%, and the X-ray diffraction experiment confirms that all samples are pure single phase indexed with the orthorhombic Pnma space group. The particle size of the LiFePO4/C synthesized by acetic acid as a complexing agent is very fine with a size of 200 nm. The electrochemical performance of this material, including reversible capacity, cycle number, and charge-discharge characteristics, is better than those of LiFePO4/C synthesized by other complexing agents. The cell of this sample can deliver a discharge capacity of 161.1 mAh g-1 at the first cycle. After 30 cycles, the capacity decreases to 157.5 mAh g-1, and the capacity fading rate is 2.2%. The mechanism is studied to explain the effect of a complexing agent on the synthesis of LiFePO4/C by sol-gel method. The results show that the complexing agent with a low stability constant may be proper for the synthetic process of LiFePO4/C via sol-gel method.

Antibacterial modification of an injectable, biodegradable, non-cytotoxic block copolymer-based physical gel with body temperature-stimulated sol-gel transition and controlled drug release.

PubMed

Wang, Xiaowen; Hu, Huawen; Wang, Wenyi; Lee, Ka I; Gao, Chang; He, Liang; Wang, Yuanfeng; Lai, Chuilin; Fei, Bin; Xin, John H

2016-07-01

Biomaterials are being extensively used in various biomedical fields; however, they are readily infected with microorganisms, thus posing a serious threat to the public health care. We herein presented a facile route to the antibacterial modification of an important A-B-A type biomaterial using poly (ethylene glycol) methyl ether (mPEG)- poly(ε-caprolactone) (PCL)-mPEG as a typical model. Inexpensive, commercial bis(2-hydroxyethyl) methylammonium chloride (DMA) was adopted as an antibacterial unit. The effective synthesis of the antibacterial copolymer mPEG-PCL-∼∼∼-PCL-mPEG (where ∼∼∼ denotes the segment with DMA units) was well confirmed by FTIR and (1)H NMR spectra. At an appropriate modification extent, the DMA unit could render the copolymer mPEG-PCL-∼∼∼-PCL-mPEG highly antibacterial, but did not largely alter its fascinating intrinsic properties including the thermosensitivity (e.g., the body temperature-induced sol-gel transition), non-cytotoxicity, and controlled drug release. A detailed study on the sol-gel-sol transition behavior of different copolymers showed that an appropriate extent of modification with DMA retained a sol-gel-sol transition, despite the fact that a too high extent caused a loss of sol-gel-sol transition. The hydrophilic and hydrophobic balance between mPEG and PCL was most likely broken upon a high extent of quaternization due to a large disturbance effect of DMA units at a large quantity (as evidenced by the heavily depressed PCL segment crystallinity), and thus the micelle aggregation mechanism for the gel formation could not work anymore, along with the loss of the thermosensitivity. The work presented here is highly expected to be generalized for synthesis of various block copolymers with immunity to microorganisms. Light may also be shed on understanding the phase transition behavior of various multiblock copolymers. Copyright © 2016 Elsevier B.V. All rights reserved.

Low temperature synthesis of CaO-SiO2 glasses having stable liquid-liquid immiscibility by sol-gel process

NASA Technical Reports Server (NTRS)

Bansal, Narottam P.

1990-01-01

Calcium silicate glass compositions lying within the liquid-liquid immiscibility dome of the phase diagram, which could not have been prepared by the conventional melting method, were synthesized by the sol-gel process. Hydrolysis and polycondensation of tetraethyl orthosilicate (TEOS) solutions containing up to 20 mol percent calcium nitrate resulted in the formation of clear and transparent gels. The gel formation time decreased with increase in water:TEOS mole ratio, calcium content, and the reaction temperature. Smaller values of gel times in the presence of calcium nitrate are probably caused by lowering of the ionic charge on the sol particles by the salt present. The gelation activation energy, E(sub gel), was evaluated from temperature dependence of the gel time. Presence of Ca(2+) ions or the water:TEOS mole ratio did not have an appreciable effect on the value of E(sub gel). Presence of glycerol in the solution helped in the formation of crack-free monolithic gel specimens. Chemical and structural changes occurring in the gels, as a function of the heat treatments, have been monitored using DTA, TGA, IR-spectroscopy, x ray diffraction, surface area and pore size distribution measurements.

Low temperature synthesis of CaO-SiO2 glasses having stable liquid-liquid immiscibility by the sol-gel process

NASA Technical Reports Server (NTRS)

Bansal, N. P.

1992-01-01

Calcium silicate glass compositions lying within the liquid-liquid immiscibility dome of the phase diagram, which could not have been prepared by the conventional melting method, were synthesized by the sol-gel process. Hydrolysis and polycondensation of tetraethyl orthosilicate (TEOS) solutions containing up to 20 mol percent calcium nitrate resulted in the formation of clear and transparent gels. The gel formation time decreased with increase in water: TEOS mole ratio, calcium content, and the reaction temperature. Smaller values of gel times in the presence of calcium nitrate are probably caused by lowering of the ionic charge on the sol particles by the salt present. The gelation activation energy, E(sub gel), was evaluated from temperature dependence of the gel time. Presence of Ca(2+) ions or the water:TEOS mole ratio did not have an appreciable effect on the value of E(sub gel). Presence of glycerol in the solution helped in the formation of crack-free monolithic gel specimens. Chemical and structural changes occurring in the gels, as a function of the heat treatments, have been monitored using DTA, TGA, IR-spectroscopy, X-ray diffraction, surface area and pore size distribution measurements.

Strength of interactions between immobilized dye molecules and sol-gel matrices.

PubMed

Ismail, Fanya; Schoenleber, Monika; Mansour, Rolan; Bastani, Behnam; Fielden, Peter; Goddard, Nicholas J

2011-02-21

In this paper we present a new theory to re-examine the immobilization technique of dye doped sol-gel films, define the strength and types of possible bonds between the immobilized molecule and sol-gel glass, and show that the immobilized molecule is not free inside the pores as was previously thought. Immobilizing three different pH sensitive dyes with different size and functional groups inside the same sol-gel films revealed important information about the nature of the interaction between the doped molecule and the sol-gel matrix. The samples were characterized by means of ultraviolet-visible spectrophotometer (UV-VIS), thermal gravimetric analysis (TGA), mercury porosimetry (MP), nuclear magnetic resonance spectroscopy ((29)Si NMR) and field-emission environmental scanning electron microscopy (ESEM-FEG). It was found that the doped molecule itself has a great effect on the strength and types of the bonds. A number of factors were identified, such as number and types of the functional groups, overall charge, size, pK(a) and number of the silanol groups which surround the immobilized molecule. These results were confirmed by the successful immobilization of bromocresol green (BCG) after a completely polymerized sol-gel was made. The sol-gel consisted of 50% tetraethoxysilane (TEOS) and 50% methyltriethoxysilane (MTEOS) (w/w). Moreover, the effect of the immobilized molecule on the structure of the sol-gel was studied by means of a leaky waveguide (LW) mode for doped films made before and after polymerization of the sol-gel.

Bactericidal micron-thin sol-gel films prevent pin tract and periprosthetic infection.

PubMed

Qu, Haibo; Knabe, Christine; Burke, Megan; Radin, Shula; Garino, Jonathan; Schaer, Thomas; Ducheyne, Paul

2014-08-01

Orthopedic injuries constitute the majority of wounds sustained by U.S. soldiers in recent conflicts. The risk of infection is considerable with fracture fixation devices. In this pilot study, we examined the use of unique bactericidal micron-thin sol-gel films on fracture fixation devices and their ability to prevent and eradicate infections. External fixation was studied with micron-thin sol-gel coated percutaneous pins releasing triclosan and inserted medially into rabbit tibiae. A total of 11 rabbits received percutaneous pins that were either uncoated or sol-gel/triclosan coated. Internal fracture fixation was also studied using sol-gel coated intramedullary (IM) nails releasing vancomycin in the intramedullary tibiae. Six sheep received IM nails that were coated with a sol-gel film that either contained vancomycin or did not contain vancomycin. All animals were challenged with Staphylococcus aureus around the implant. Animals were euthanized at 1 month postoperative. Rabbits receiving triclosan/sol-gel coated percutaneous pins did not show signs of infection. Uncoated percutaneous pins had a significantly higher infection rate. In the sheep study, there were no radiographic signs of osteomyelitis with vancomycin/sol-gel coated IM nails, in contrast to the observations in the control cohort. Hence, the nanostructured sol-gel controlled release technology offers the promise of a reliable and continuous delivery system of bactericidals from orthopedic devices to prevent and treat infection. Reprint & Copyright © 2014 Association of Military Surgeons of the U.S.

Electrochemical and In Vitro Behavior of Nanostructure Sol-Gel Coated 316L Stainless Steel Incorporated with Rosemary Extract

NASA Astrophysics Data System (ADS)

Motalebi, Abolfazl; Nasr-Esfahani, Mojtaba

2013-06-01

The corrosion resistance of AISI 316L stainless steel for biomedical applications, was significantly enhanced by means of hybrid organic-inorganic sol-gel thin films deposited by spin-coating. Thin films of less than 100 nm with different hybrid characters were obtained by incorporating rosemary extract as green corrosion inhibitor. The morphology, composition, and adhesion of hybrid sol-gel coatings have been examined by SEM, EDX, and pull-off test, respectively. Addition of high additive concentrations (0.1%) did not disorganize the sol-gel network. Direct pull-off test recorded a mean coating-substrate bonding strength larger than 21.2 MPa for the hybrid sol-gel coating. The effect of rosemary extract, with various added concentrations from 0.012 to 0.1%, on the anticorrosion properties of sol-gel films have been characterized by electrochemical impedance spectroscopy (EIS) and potentiodynamic polarization tests in simulated body fluid (SBF) solution and has been compared to the bare metal. Rosemary extract additions (0.05%) have significantly increased the corrosion protection of the sol-gel thin film to higher than 90%. The in vitro bioactivity of prepared films indicates that hydroxyapatite nuclei can form and grow on the surface of the doped sol-gel thin films. The present study shows that due to their excellent anticorrosion properties, bioactivity and bonding strength to substrate, doped sol-gel thin films are practical hybrid films in biomedical applications.

Sol-gel derived CaCu{sub 3}Ti{sub 4}O{sub 12} ceramics: Synthesis, characterization and electrical properties

DOE Office of Scientific and Technical Information (OSTI.GOV)

Liu Laijun; Fan Huiqing; Fang Pinyang

2008-07-01

The giant dielectric constant material CaCu{sub 3}Ti{sub 4}O{sub 12} (CCTO) has been synthesized by sol-gel method, for the first time, using nitrate and alkoxide precursor. The electrical properties of CCTO ceramics, showing an enormously large dielectric constant {epsilon} {approx} 60,000 (100 Hz at RT), were investigated in the temperature range from 298 to 358 K at 0, 5, 10, 20, and 40 V dc. The phases, microstructures, and impedance properties of final samples were characterized by X-ray diffraction, scanning electron microscopy, and precision impedance analyzer. The dielectric permittivity of CCTO synthesized by sol-gel method is at least three times ofmore » magnitude larger than that synthesized by other low-temperature method and solid-state reaction method. Furthermore, the results support the internal barrier layer capacitor (IBLC) model of Schottky barriers at grain boundaries between semiconducting grains.« less

Synthesis of polymeric fluorinated sol-gel precursor for fabrication of superhydrophobic coating

NASA Astrophysics Data System (ADS)

Li, Qianqian; Yan, Yuheng; Yu, Miao; Song, Botao; Shi, Suqing; Gong, Yongkuan

2016-03-01

A fluorinated polymeric sol-gel precursor (PFT) is synthesized by copolymerization of 2,3,4,5,5,5-hexafluoro-2,4-bis(trifluorinated methyl)pentyl methacrylate (FMA) and 3-methacryloxypropyltrimethoxysilane (TSMA) to replace the expensive long chain fluorinated alkylsilanes. The fluorinated silica sol is prepared by introducing PFT as co-precursor of tetraethyl orthosilicate (TEOS) in the sol-gel process with ammonium hydroxide as catalyst, which is then used to fabricate superhydrophobic coating on glass substrate through a simple dip-coating method. The effects of PFT concentrations on the chemical structure of the formed fluorinated silica, the surface chemical composition, surface morphology, wetting and self-cleaning properties of the resultant fluorinated silica coatings were studied by using X-ray powder diffraction (XRD), Fourier transform infrared spectrometer (FTIR), X-ray photoelectron spectrophotometer (XPS), scanning electron microscopy (SEM) and water contact angle measurements (WCA). The results show that the fluorinated silica sols are successfully obtained. The size and size distribution of the fluorinated silica particles are found greatly dependent on the concentration of PFT, which play a crucial role in the surface morphology of the corresponding fluorinated silica coatings. The suitable PFT concentration added in the sol-gel stage, i.e. for F-sol-1 and F-sol-2, is helpful to achieve both the low surface energy and multi-scaled microstructures, leading to the formation of the superhydrophobic coatings with bio-mimicking self-cleaning property similar to lotus leaves.

Titanium (IV) sol-gel chemistry in varied gravity environments

NASA Astrophysics Data System (ADS)

Hales, Matthew; Martens, Wayde; Steinberg, Theodore

Sol-gel synthesis in reduced gravity is a relatively new topic in the literature and further inves-tigation is essential to realise its potential and application to other sol-gel systems. The sol-gel technique has been successfully applied to the synthesis of silica systems of varying porosity for many diverse applications [1-5]. It is proposed that current methods for the synthesis of silica sol-gels in reduced gravity may be applied to titanium sol-gel processing in order to enhance desirable physical and chemical characteristics of the final materials. The physical and chemical formation mechanisms for titanium alkoxide based sol-gels, to date, is not fully understood. However, various authors [6-9] have described potential methods to control the hydrolysis and condensation reactions of titanium alkoxides through the use of chemical inhibitors. A preliminary study of the reaction kinetics of titanium alkoxide sol-gel reaction in normal gravity was undertaken in order to determine reactant mixtures suitable for further testing under varied gravity conditions of limited duration. Through the use of 1H Nuclear Magnetic Resonance spectroscopy (NMR) for structural analysis of precursor materials, Ultra-Violet-Visible spectroscopy (UV-VIS) and viscosity measurements, it was demonstrated that not only could the rate of the chemical reaction could be controlled, but directed linear chain growth within the resulting gel structure was achievable through the use of increased inhibitor concentrations. Two unique test systems have been fabricated to study the effects of varied gravity (reduced, normal, high) on the formation of titanium sol-gels. Whilst the first system is to be used in conjunction with the recently commissioned drop tower facility at Queensland University of Technology in Brisbane, Australia to produce reduced gravity conditions. The second system is a centrifuge capable of providing high gravity environments of up to 70 G's for extended periods of time. The test systems and experimental results obtained will be presented. 1. Okubo, T., Tsuchida, A., Okuda, T., Fujitsuna, K., Ishikawa, M., Morita, T., Tada, T. , Kinetic Analyses of Colloidal Crystallization in Microgravity -Aircraft Experiments. . Colloids and Surfaces A: Physicochemical and Engineering Aspects, 1999. 153: p. 515-524. 2. Okubo, T., Tsuchida, A., Kobayashi, K., Kuno, A., Morita, T., Fujishima, M., Kohno, Y., Kinetic Study of the Formation Reaction of Colloidal Silica Spheres in Microgravity Using Aircraft. Colloid Polymer Science, 1999. 277(5): p. 474-478. 3. Pienaar, C.L., Chiffoleau, G. J. A., Follens, L. R. A., Martens, J. A., Kirschhock, C. E. A., Steinberg, T. A., Effect of Gravity on the Gelation of Silica Sols. Chem. Mater., 2007. 19(4): p. 660-664. 4. Smith, D.D., et al., Effect of Microgravity on the Growth of Silica Nanostructures. Langmuir, 2000. 16(26): p. 10055-10060. 5. Zhang, X., Johnson, D.P., Manerbino, A.R., Moore, J.J., Schowengerdt, F. , Recent Mi-crogravity Results in the Synthesis of Porous Materials. AIP Conference Proceedings (Space Technology and Applications International Forum-1999, Pt. 1), 1999. 458: p. 88-93. 6. Dunbar, P.B., Bendzko, N.J.,, 1H and 13C NMR observation of the reaction of acetic acid with titanium isopropoxide. Materials Chemistry and Physics, 1999. 59: p. 26-35. 7. Krunks, M., Oja, I., T˜nsuaadu, K., Es-Souni, M., Gruselle, M., Niinistü,. L, Thermoanalytical study of acetylacetonate-modified titanium (iv) isopropoxide as precursor for TiO2 films. Journal of Thermal Analysis and Calorimetry, 2005: p. 483-488. 8. Moran, P.D., Bowmaker, G. A., Cooney, R. P., Vibrational Spectra and Molecular Associa-tion of Titanium Tetraisopropoxide. Inorg. Chem., 1998. 37(1): p. 2741-2748. 9. Somogyvari, A., Serpone, N.,, Evidence for five-coordination in titanium(1V) complexes. A nuclear magnetic resonance investigation. Canadian Journal of Chemistry, 1977. 56: p. 316-319.

Surface modification of quartz fibres for dental composites through a sol-gel process.

PubMed

Wang, Yazi; Wang, Renlin; Habib, Eric; Wang, Ruili; Zhang, Qinghong; Sun, Bin; Zhu, Meifang

2017-05-01

In this study, quartz fibres (QFs) surface modification using a sol-gel method was proposed and dental posts reinforced with modified QFs were produced. A silica sol (SS) was prepared using tetraethoxysilane (TEOS) and 3-methacryloxypropyltrimethoxysilane (γ-MPS) as precursors. The amount of γ-MPS in the sol-gel system was varied from 0 to 24wt.% with a constant molar ratio of TEOS, ethanol, deionized water, and HCl. Thermogravimetric analysis (TGA), Fourier transform infrared spectroscopy (FT-IR), and contact angle (CA) measurements were used to characterize the modified QFs, which confirmed that SS had successfully coated the surface of QFs. SEM images showed good interfacial bonding between the modified QFs and the resin matrix. The results of three-point bending tests of the fibre reinforced composite (FRC) posts showed that the QFs modified by SS with 12wt.% γ-MPS presented the best mechanical properties, demonstrating improvements of 108.3% and 89.6% for the flexural strength and flexural modulus, respectively, compared with untreated QFs. Furthermore, the sorption and solubility of the prepared dental posts were also studied by immersing the posts in artificial saliva (AS) for 4weeks, and yielded favourable results. This sol-gel surface modification method promises to resolve interfacial bonding issues of fibres with the resin matrix, and produce FRC posts with excellent properties. Copyright © 2017. Published by Elsevier B.V.

Sol-to-Gel Transition in Fast Evaporating Systems Observed by in Situ Time-Resolved Infrared Spectroscopy.

PubMed

Innocenzi, Plinio; Malfatti, Luca; Carboni, Davide; Takahashi, Masahide

2015-06-22

The in situ observation of a sol-to-gel transition in fast evaporating systems is a challenging task and the lack of a suitable experimental design, which includes the chemistry and the analytical method, has limited the observations. We synthesise an acidic sol, employing only tetraethylorthosilicate, SiCl4 as catalyst and deuterated water; the absence of water added to the sol allows us to follow the absorption from the external environment and the evaporation of deuterated water. The time-resolved data, obtained by attenuated total reflection infrared spectroscopy on an evaporating droplet, enables us to identify four different stages during evaporation. They are linked to specific hydrolysis and condensation rates that affect the uptake of water from external environment. The second stage is characterized by a decrease in hydroxyl content, a fast rise of condensation rate and an almost stationary absorption of water. This stage has been associated with the sol-to-gel transition. © 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Surface analysis and biocorrosion properties of nanostructured surface sol-gel coatings on Ti6Al4V titanium alloy implants.

PubMed

Advincula, Maria C; Petersen, Don; Rahemtulla, Firoz; Advincula, Rigoberto; Lemons, Jack E

2007-01-01

Surfaces of biocompatible alloys used as implants play a significant role in their osseointegration. Surface sol-gel processing (SSP), a variant of the bulk sol-gel technique, is a relatively new process to prepare bioreactive nanostructured titanium oxide for thin film coatings. The surface topography, roughness, and composition of sol-gel processed Ti6Al4V titanium alloy coatings was investigated by atomic force microscopy (AFM) and X-ray electron spectroscopy (XPS). This was correlated with corrosion properties, adhesive strength, and bioreactivity in simulated body fluids (SBF). Electroimpedance spectroscopy (EIS) and polarization studies indicated similar advantageous corrosion properties between sol-gel coated and uncoated Ti6Al4V, which was attributed to the stable TiO2 composition, topography, and adhesive strength of the sol-gel coating. In addition, inductive coupled plasma (ICP) and scanning electron microscopy with energy dispersive spectrometry (SEM-EDS) analysis of substrates immersed in SBF revealed higher deposition of calcium and phosphate and low release rates of alloying elements from the sol-gel modified alloys. The equivalent corrosion behavior and the definite increase in nucleation of calcium apatite indicate the potential of the sol-gel coating for enhanced bioimplant applications. 2006 Wiley Periodicals, Inc.

Surface Modification of Zirconia Substrate by Calcium Phosphate Particles Using Sol-Gel Method.

PubMed

Jin, So Dam; Um, Sang Cheol; Lee, Jong Kook

2015-08-01

Surface modification with a biphasic composition of hydroxyapatite (HA) and tricalcium phosphate (TCP) was performed on a zirconia substrate using a sol-gel method. An initial calcium phosphate sol was prepared by mixing a solution of Ca(NO3)2 · 4H20 and (C2H5O)3P(O), while both porous and dense zirconia were used as substrates. The sol-gel coating was performed using a spin coater. The coated porous zirconia substrate was re-sintered at 1350 °C 2 h, while coated dense zirconia substrate was heat-treated at 750 °C 1 h. The microstructure of the resultant HA/TCP coatings was found to be dependent on the type of zirconia substrate used. With porous zirconia as a starting substrate, numerous isolated calcium phosphate particles (TCP and HA) were uniformly dispersed on the surface, and the particle size and covered area were dependent on the viscosity of the calcium phosphate sol. Conversely, when dense zirconia was used as a starting substrate, a thick film of nano-sized HA particles was obtained after heat treatment, however, substantial agglomeration and cracking was also observed.

Silver/hydroxyapatite composite coatings on porous titanium surfaces by sol-gel method.

PubMed

Qu, Jie; Lu, Xiong; Li, Dan; Ding, Yonghui; Leng, Yang; Weng, Jie; Qu, Shuxin; Feng, Bo; Watari, Fumio

2011-04-01

Hydroxyapatite (HA) coatings loaded with nanosilver particles is an attractive method to impart the HA coating with antibacterial properties. Producing Ag/HA coatings on porous Ti substrates have been an arduous job since commonly used line-of-sight techniques are not able to deposit uniform coatings on the inner pore surfaces of the porous Ti. In this study, porous Ti scaffolds with high porosity and interconnected structures were prepared by polymer impregnating method. A sol-gel process was used to produce uniform Ag/HA composite coatings on the surfaces of porous Ti substrates. Ca(NO(3) )(2) ·4H(2) O and P(2) O(5) in an ethyl alcohol based system was selected to prepare the sol, which ensured the homogeneous distribution of Ag in the sol. The characterization revealed that silver particles uniformly distributed in the coatings without agglomeration. High antibacterial ratio (>95%), against E. coli and S. albus was expressed by the silver-containing coatings (Ag/HA 0.8 and 1.6 wt %). The biocompatibility of the Ag/HA 0.8 surfaces was as good as that of pure HA surface, as revealed by culturing osteoblasts on them. The results indicated that Ag/HA 0.8 had the good balance between the biocompatibility and antibacterial properties of the coatings. Copyright © 2011 Wiley Periodicals, Inc.

The sol-gel template synthesis of porous TiO2 for a high performance humidity sensor

NASA Astrophysics Data System (ADS)

Wang, Zhuyi; Shi, Liyi; Wu, Fengqing; Yuan, Shuai; Zhao, Yin; Zhang, Meihong

2011-07-01

This research develops a simple template assisted sol-gel process for preparing porous TiO2 for a high performance humidity sensor. Tetraethyl orthosilicate (TEOS) as a template was directly introduced into TiO2 sol formed by the hydrolysis and condensation of titanium alkoxide; the following calcination led to the formation of TiO2-SiO2 composite, and the selective removal of SiO2 by dilute HF solution led to the formation of porous structure in TiO2. The resulting porous TiO2-based sensor exhibits high sensitivity and linear response in the wide relative humidity (RH) range of 11%-95%, with an impedance variation of four orders of magnitude to humidity change. Moreover, it exhibits a rapid and highly reversible response characterized by a very small hysteresis of < 1% RH and a short response-recovery time (5 s for adsorption and 8 s for desorption), and a 30-day stability test also confirms its long-term stability. Compared with pure TiO2 prepared by the conventional sol-gel method, our product shows remarkably improved performance and good prospect for a high performance humidity sensor. The complex impedance spectra were used to elucidate its humidity sensing mechanism in detail.

Sol-gel technique for the preparation of beta-cyclodextrin derivative stationary phase in open-tubular capillary electrochromatography.

PubMed

Wang, Y; Zeng, Z; Guan, N; Cheng, J

2001-07-01

A novel open-tubular capillary electrochromatography (OT-CEC) column coated with 2,6-dibutyl-beta-cyclodextrin (DB-beta-CD) was prepared using sol-gel technique. In the sol-gel approach, owing to the three-dimensional network of sol-gel and the strong chemical bond between the stationary phase and the surface of capillary columns, good chromatographic characteristics and unique selectivity in separating isomers were shown. We achieved high efficiencies of 5-14 x 10(4) plates/m for the isomeric nitrophenols using the sol-gel-derived DB-beta-CD columns. The migration time reproducibility of the separation of the isomeric nitrophenols was better than 2.2% over five runs and 4.5% from column to column. These sol-gel-coated DB-beta-CD columns have shown improved separations of isomeric aminophenols, isomeric dihydroxybenzenes and isomeric nitrophenols, in comparison with the sol-gel matrix capillary column. The influences of buffer pH and methanol solvent on separation were investigated. The chiral resolution of enantiomers such as ibuprofen and binaphthol was explored primarily.

Sol-gel immobilized short-chain poly(ethylene glycol) coating for capillary microextraction of underivatized polar analytes.

PubMed

Kulkarni, Sameer; Shearrow, Anne M; Malik, Abdul

2007-12-07

Sol-gel coating with covalently bonded low-molecular-weight (MW<300 Da) poly(ethylene glycol) (PEG) chains was developed for capillary microextraction (CME). The sol-gel chemistry proved effective in the immobilization of low-molecular-weight PEGs thanks to the formation of chemical bonds between the organic-inorganic hybrid sol-gel PEG coating and the fused silica capillary inner surface. This chemical anchorage provided excellent thermal and solvent stability to the created sol-gel PEG coating as is evidenced by its high upper limit of allowable conditioning temperature (340 degrees C) and its practically identical performance before and after rinsing with various solvents. The prepared sol-gel PEG coating provided simultaneous extraction of moderately polar and highly polar analytes from aqueous samples without requiring derivatization, pH adjustment or salting-out procedures. Detection limits on the order of nanogram per liter (ng/L) were achieved in CME-GC-flame ionization detection experiments designed for the preconcentration and trace analysis of both highly polar and moderately polar compounds extracted directly from aqueous media using sol-gel short-chain PEG coated microextraction capillaries.

Evolution of heterogeneity accompanying sol-gel transitions in a supramolecular hydrogel.

PubMed

Matsumoto, Yuji; Shundo, Atsuomi; Ohno, Masashi; Tsuruzoe, Nobutomo; Goto, Masahiro; Tanaka, Keiji

2017-10-18

When a peptide amphiphile is dispersed in water, it self-assembles into a fibrous network, leading to a supramolecular hydrogel. When the gel is physically disrupted by shaking, it transforms into a sol state. After aging at room temperature for a while, it spontaneously returns to the gel state, called sol-gel transition. However, repeating the sol-gel transition often causes a change in the rheological properties of the gel. To gain a better understanding of the sol-gel transition and its reversibility, we herein examined the thermal motion of probe particles at different locations in a supramolecular hydrogel. The sol obtained by shaking the gel was heterogeneous in terms of the rheological properties and the extent decreased with increasing aging time. This time course of heterogeneity, or homogeneity, which corresponded to the sol-to-gel transition, was observed for the 1st cycle. However, this was not the case for the 2nd and 3rd cycles; the heterogeneity was preserved even after aging. Fourier-transform infrared spectroscopy, small-angle X-ray scattering, and atomic force and confocal laser scanning microscopies revealed that, although the molecular aggregation states of amphiphiles both in the gel and sol remained unchanged with the cycles, the fibril density diversified to high and low density regions even after aging. The tracking of particles with different sizes indicated that the partial mesh size in the high density region and the characteristic length scale of the density fluctuation were smaller than 50 nm and 6 μm, respectively.

Electrospinning of ceramic nanofibers

NASA Astrophysics Data System (ADS)

Eick, Benjamin M.

Silicon Carbide (SiC) nanofibers of diameters as low as 20 nm are fabricated. The fibers were produced through the electrostatic spinning of the preceramic poly(carbomethylsilane) with pyrolysis to ceramic. A new technique was used where the preceramic was blended with polystyrene (PS) and, subsequent to electrospinning, was exposed to UV to crosslink the PS and prevent fibers flowing during pyrolysis. Electrospun SiC fibers were characterized by FTIR, TGA-DTA, SEM, TEM, XRD, and SAED. Fibers were shown to be polycrystalline and nanograined with alpha-SiC 15R polytype being dominant, where commercial fiber production methods form beta-SiC 3C. Pyrolysis of the bulk polymer blend to SiC produced alpha-SiC 15R as the dominant polytype with larger grains showing that electrospinning nanofibers affects resultant crystallinity. Fibers produced were shown to have a core-shell structure of an oxide scale that was variable by pyrolysis conditions. Metal oxide powders (chromium oxide, cobalt oxide, iron oxide, silicon oxide, tantalum oxide, titanium oxide, tungsten oxide, vanadium oxide, and zirconium oxide), were converted to metal carbide powders and metal nitride powders by the process of carbothermal reduction (CTR). Synthetic pitch was explored as an alternative to graphite which is a common carbon source for CTR. It was shown via characterization with XRD that pitch performs as well and in some cases better than graphite and is therefore a viable alternative in CTR. Conversion of metal oxide powders with pitch led to conversion of sol-gel based metal oxide nanofibers produced by electrospinning. Pitch was soluble in the solutions xv that were electrospun allowing for intimate contact between the sol-gel and the carbon source for CTR. This method became a two step processing method to produce metal carbide and nitride nanofibers: first electrospin sol-gel based metal oxide nanofibers and subsequently pyrolize them in the manner of CTR to transform them. Results indicate that this method was capable of transforming hafnium, niobium, tantalum, titanium, vanadium, and zirconium sol-gel nanofibers to metal carbides and nitrides.

Incorporating silica into cyanate ester-based network by sol-gel method: Structure and properties of subnano- and nanocomposites

NASA Astrophysics Data System (ADS)

Bershtein, V.; Fainleib, A.; Kirilenko, D.; Yakushev, P.; Gusakova, K.; Lavrenyuk, N.; Ryzhov, V.

2016-05-01

A series of Cyanate Ester Resins (CER)-based composites containing 0.01-10 wt. % silica, introduced by sol-gel method, was synthesized using tetraethoxysilane (TEOS) and γ-aminopropyltrimethoxysilane (APTMS), and their nanostructure and properties were characterized by means of STEM/EDXS, Far-IR spectroscopy, DMA and DSC methods. It was revealed that the most substantial positive impact on CER dynamics, thermal and mechanical properties is attained at ultra-low silica contents, e.g., at 0.1 wt. % silica where Tg and modulus increase, respectively, by 50° and 60%. In this case, silica nanoclusters are absent in the composite, and only chemically incorporated silica junctions of subnanometric size in the densely-crosslinked CER network could be implied. These composites can be designated as "polymer subnanocomposites". Contrarily, formation of silica nanoclusters and especially their aggregates of hundreds nanometers in size at silica contents of 2-10 wt. % led to the distinct negative impact on the matrix properties.

Environmentally benign sol-gel antifouling and foul-releasing coatings.

PubMed

Detty, Michael R; Ciriminna, Rosaria; Bright, Frank V; Pagliaro, Mario

2014-02-18

Biofouling on ships and boats, characterized by aquatic bacteria and small organisms attaching to the hull, is an important global issue, since over 80000 tons of antifouling paint is used annually. This biofilm, which can form in as little as 48 hours depending on water temperature, increases drag on watercraft, which greatly reduces their fuel efficiency. In addition, biofouling can lead to microbially induced corrosion (MIC) due to H2S formed by the bacteria, especially sulfate-reducing bacteria. When the International Maritime Organization (IMO) international convention banned the use of effective but environmentally damaging coatings containing tributyl tin in 2008, the development of clean and effective antifouling systems became more important than ever. New nonbiocidal coatings are now in high demand. Scientists have developed new polymers, materials, and biocides, including new elastomeric coatings that they have obtained by improving the original silicone (polydimethylsiloxane) formulation patented in 1975. However, the high cost of silicones, especially of fluoropolymer-modified silicones, has generally prevented their large-scale diffusion. In 2009, traditional antifouling coatings using cuprous oxide formulated in copolymer paints still represented 95% of the global market volume of anti-fouling paints. The sol-gel nanochemistry approach to functional materials has emerged as an attractive candidate for creating low fouling surfaces due to the unique structure and properties of silica-based coatings and of hybrid inorganic-organic silicas in particular. Sol-gel formulations easily bind to all types of surfaces, such as steel, fiberglass, aluminum, and wood. In addition, they can cure at room temperature and form thin glassy coatings that are markedly different from thick silicone elastomeric foul-releasing coatings. Good to excellent performance against biofouling, low cure temperatures, enhanced and prolonged chemical and physical stability, ease of application, and the waterborne nature of sol-gel coatings all support the diffusion of these paints to efficiently reduce the accumulation of fouling layers on valued surfaces immersed in marine or fluvial waters. Furthermore, sol-gel glassy coatings are transparent and can be effectively applied to optical devices, windows, and solar panels used in lake, fluvial, or marine environments. Sol-gel technology is eminently versatile, and the first generation sol-gel paints have already shown good performance. Even so, vast opportunities still exist for chemists to develop novel sol-gel derived coatings to both prevent biofouling and enhance the hydrodynamic properties of boat and ship hulls. Moreover, researchers have prepared and applied multifunctional sol-gel coatings providing protection against both biofouling and corrosion. They have tested these in the marine environment with good preliminary results. In this Account, we discuss some of our new strategies for the controlled functionalization of surfaces for the development of efficient antifouling and foul-releasing systems and summarize the main achievements with biocidal and nonbiocidal sol-gel coatings. We conclude by giving insight into the marine coatings and sol-gel products markets, providing arguments to justify our conclusion that the sol-gel coatings technology is now a mature platform for the development of economically viable and environmentally friendly antifouling and foul-release formulations of enhanced performance.

Processing of non-oxide ceramics from sol-gel methods

DOEpatents

Landingham, Richard; Reibold, Robert A.; Satcher, Joe

2014-12-12

A general procedure applied to a variety of sol-gel precursors and solvent systems for preparing and controlling homogeneous dispersions of very small particles within each other. Fine homogenous dispersions processed at elevated temperatures and controlled atmospheres make a ceramic powder to be consolidated into a component by standard commercial means: sinter, hot press, hot isostatic pressing (HIP), hot/cold extrusion, spark plasma sinter (SPS), etc.

Synthesis of nano-sized lithium cobalt oxide via a sol-gel method

NASA Astrophysics Data System (ADS)

Li, Guangfen; Zhang, Jing

2012-07-01

In this study, nano-structured LiCoO2 thin film were synthesized by coupling a sol-gel process with a spin-coating method using polyacrylic acid (PAA) as chelating agent. The optimized conditions for obtaining a better gel formulation and subsequent homogenous dense film were investigated by varying the calcination temperature, the molar mass of PAA, and the precursor's molar ratios of PAA, lithium, and cobalt ions. The gel films on the silicon substrate surfaces were deposited by multi-step spin-coating process for either increasing the density of the gel film or adjusting the quantity of PAA in the film. The gel film was calcined by an optimized two-step heating procedure in order to obtain regular nano-structured LiCoO2 materials. Both atomic force microscopy (AFM) and scanning electron microscopy (SEM) were utilized to analyze the crystalline and the morphology of the films, respectively.

Polyethylene glycol assisted growth of Sn-doped ZnO nanorod arrays prepared via sol-gel immersion method

NASA Astrophysics Data System (ADS)

Ismail, A. S.; Mamat, M. H.; Malek, M. F.; Saidi, S. A.; Yusoff, M. M.; Mohamed, R.; Sin, N. D. Md; Suriani, A. B.; Rusop, M.

2018-05-01

Tin-doped zinc oxide (SZO) nanorod films at different concentrations of polyethylene glycol (PEG) were successfully deposited on zinc oxide (ZnO) seeded layer catalyst using sol-gel immersion method. The morphology of the samples were characterized using field emission scanning electron microscopy (FESEM), optical properties using UV-Vis spectrophotometer and electrical properties using I-V measurement system. The current-voltage (I-V) characteristics displayed that 5 wt % sample produced the highest conductivity.

Electrophoretically active sol-gel processes to backfill, seal, and/or densify porous, flawed, and/or cracked coatings on electrically conductive material

DOEpatents

Panitz, Janda K.; Reed, Scott T.; Ashley, Carol S.; Neiser, Richard A.; Moffatt, William C.

1999-01-01

Electrophoretically active sol-gel processes to fill, seal, and/or density porous, flawed, and/or cracked coatings on electrically conductive substrates. Such coatings may be dielectrics, ceramics, or semiconductors and, by the present invention, may have deposited onto and into them sol-gel ceramic precursor compounds which are subsequently converted to sol-gel ceramics to yield composite materials with various tailored properties.

Reconstruction of active regular motion in amoeba extract: dynamic cooperation between sol and gel states.

PubMed

Nishigami, Yukinori; Ichikawa, Masatoshi; Kazama, Toshiya; Kobayashi, Ryo; Shimmen, Teruo; Yoshikawa, Kenichi; Sonobe, Seiji

2013-01-01

Amoeboid locomotion is one of the typical modes of biological cell migration. Cytoplasmic sol-gel conversion of an actomyosin system is thought to play an important role in locomotion. However, the mechanisms underlying sol-gel conversion, including trigger, signal, and regulating factors, remain unclear. We developed a novel model system in which an actomyosin fraction moves like an amoeba in a cytoplasmic extract. Rheological study of this model system revealed that the actomyosin fraction exhibits shear banding: the sol-gel state of actomyosin can be regulated by shear rate or mechanical force. Furthermore, study of the living cell indicated that the shear-banding property also causes sol-gel conversion with the same order of magnitude as that of shear rate. Our results suggest that the inherent sol-gel transition property plays an essential role in the self-regulation of autonomous translational motion in amoeba.

Novel route for rapid sol-gel synthesis of hydroxyapatite, avoiding ageing and using fast drying with a 50-fold to 200-fold reduction in process time.

PubMed

Ben-Arfa, Basam A E; Salvado, Isabel M Miranda; Ferreira, José M F; Pullar, Robert C

2017-01-01

We have developed an innovative, rapid sol-gel method of producing hydroxyapatite nanopowders that avoids the conventional lengthy ageing and drying processes (over a week), being 200 times quicker in comparison to conventional aqueous sol-gel preparation, and 50 times quicker than ethanol based sol-gel synthesis. Two different sets of experimental conditions, in terms of pH value (5.5 and 7.5), synthesis temperature (45 and 90°C), drying temperature (60 and 80°C) and calcination temperature (400 and 700°C) were explored. The products were characterised by X-ray diffraction (XRD) Fourier-transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM) and specific surface area (SSA) measurements. Pure hydroxyapatite (Ca 10 (PO 4 ) 6 (OH) 2 , HAp) was obtained for the powders synthesised at pH7.5 and calcined at 400°C, while biphasic mixtures of HAp/β-tricalcium phosphate (β-Ca 3 (PO 4 ) 2 , TCP) were produced at pH5.5 and (pH7.5 at elevated temperature). The novel rapid drying was up to 200 times faster than conventional drying, only needing 1h with no prior ageing step, and favoured the formation of smaller/finer nanopowders, while producing pure HAp or phase mixtures virtually identical to those obtained from the slow conventional drying method, despite the absence of a slow ageing process. The products of this novel rapid process were actually shown to have smaller crystallite sizes and larger SSA, which should result in increased bioactivity. Copyright © 2016 Elsevier B.V. All rights reserved.

Sol concentration effect on ZnO nanofibers photocatalytic activity synthesized by sol-gel dip coating method

NASA Astrophysics Data System (ADS)

Toubane, M.; Tala-Ighil, R.; Bensouici, F.; Bououdina, M.; Souier, M.; Liu, S.; Cai, W.; Iratni, A.

2017-03-01

ZnO thin films were deposited onto glass substrate by sol-gel dip coating method. The initial sol concentrations were varied from 0.2 to 0.5 M. Zinc acetate dihydrate, ethanol and Diethanolamine (DEA) were used as staring material, solvent and stabilizer respectively. The evolution of structural, optical properties and methylene blue (MB) photodegradation of the as-deposited films on sol concentration was investigated. Rietveld refinements of x-ray patterns reveal that all the as-prepared thin films have a Zincite-type structure with grain orientation along to c-axis. The strongest sol concentration is favorable for the highest crystallization quality. However, the high preferred orientation factor (POF) occurs for 0.3 M sol concentration. The field emission scanning electron microscopy observations reveals nanofibrous morphology with different lengths. The nanofibers density increases with increasing sols concentrations until forming a flower-like morphology. The EDS analysis confirms the high purity of the as-deposited ZnO films. It is found that all films present good transparency greater than 95% in the visible range; the optical band gap is slightly reduced with the increase in sol concentration. The photocatalytic degradation is enhanced by 90% with the sol concentration. The K app rate reaction increased with increasing sol concentration. The films stability is found to slightly decrease after the third cycle, especially for 0.5 M sol concentration.

Hydrogen permeation through steel coated with erbium oxide by sol-gel method

NASA Astrophysics Data System (ADS)

Yao, Zhenyu; Suzuki, Akihiro; Levchuk, Denis; Chikada, Takumi; Tanaka, Teruya; Muroga, Takeo; Terai, Takayuki

2009-04-01

Er 2O 3 coating is formed on austenitic stainless steel 316ss by sol-gel method. The results showed good crystallization of coating by baking in high purity flowing-argon at 973 K, and indicated that a little oxygen in baking atmosphere is necessary to crystallization of coating. The best baking temperature could be thought as 973 K, to get good crystallization of coating and avoid strong oxidation of steel substrate. The deuterium permeation test was performed for coated and bare 316ss, to evaluate the property of Er 2O 3 sol-gel coating as a potential tritium permeation barrier. In this study, the deuterium permeability of coated 316ss is about 1-2 orders of magnitude lower than that of bare 316ss, and is about 2-3 orders of magnitude than the referred data of bare Eurofer97 and F82H martensitic steel.

Physically incorporated extraction phase of solid-phase microextraction by sol-gel technology.

PubMed

Liu, Wenmin; Hu, Yuan; Zhao, Jinghong; Xu, Yuan; Guan, Yafeng

2006-01-13

A sol-gel method for the preparation of solid-phase microextraction (SPME) fiber was described and evaluated. The extraction phase of poly(dimethysiloxane) (PDMS) containing 3% vinyl group was physically incorporated into the sol-gel network without chemical bonding. The extraction phase itself is then partly crosslinked at 320 degrees C, forming an independent polymer network and can withstand desorption temperature of 290 degrees C. The headspace extraction of BTX by the fiber SPME was evaluated and the detection limit of o-xylene was down to 0.26 ng/l. Extraction and determination of organophosphorus pesticides (OPPs) in water, orange juice and red wine by the SPME-GC thermionic specified detector (TSD) was validated. Limits of detection of the method for OPPs were below 10 ng/l except methidathion. Relative standard deviations (RSDs) were in the range of 1-20% for pesticides being tested.

Spectroscopic studies of trimetoxypropylsilane and bis(trimethoxysilyl)ethane sol-gel coatings on aluminum and copper.

PubMed

Li, Ying-Sing; Tran, Tuan; Xu, Yue; Vecchio, Nicolas E

2006-11-01

Trimethoxypropylsilane (TMPS) and bis(trimethoxysilyl)ethane (BTMSE) were used as surface modifiers of metal vie the sol-gel process and dip coating. In addition to the single coating of Al, Cu and Sn, double treatments of Al were also conducted by combining coatings with these sol-gels in different sequences. Reflection and absorption infrared spectroscopy (RAIR) was employed to characterize and to trace the proceeding of the sol-gel process of the films. It was found that the silanol condensation occurs in the coating films on Al and the covalent linkage exists between the TMPS film and copper surface. From the assigned vibration modes, two conformers were identified in pure TMPS, TMPS sol-gel and coated film. A series of dip coating experiments with different concentrations of TMPS sol-gel was conducted, and the results from the collected RAIR spectra of the coated samples suggested that the coated Cu consistently has a better RAIR spectrum than that of the coated Al. The TMPS sol-gel appeared to have a better affinity to Cu than to Al. The temperature effect and the aging effect in the coating films were studied. X-ray photoelectronic spectroscopy (XPS) was employed to characterize the coated film, and the XPS data confirm the formation of the siloxane film from the silane coupling agents (SCA). Electrochemical impedance spectra (EIS) have been collected for bare Al and Cu, BTMSE sol-gel coated Al, and TMPS sol-gel coated Cu in 0.15M NaCl solution. The corresponding electronic circuit parameters have been determined to match the experimental EIS data.

Investigation of novel sol-gel hydrophobic surfaces for desorption electrospray ionization-mass spectrometry analysis.

PubMed

Penna, Andrea; Elviri, Lisa; Careri, Maria; Mangia, Alessandro; Predieri, Giovanni

2011-05-01

Sol-gel-based materials were synthesized, characterized and finally tested as solid supports for desorption electrospray ionization-mass spectrometry (DESI-MS) analysis of a mixture of compounds of different polarity. Films with thickness in the 2-4 μm range were obtained by a dip-coating process using tetraethoxysilane (TEOS) and octyltriethoxysilane (OTES) as sol-gel precursors. Three types of surface with different hydrophobic character were obtained by varying the TEOS/OTES ratio in the sol-gel mixture. Each coating was characterized by atomic force microscopy investigations, gaining insight into homogeneity, smoothness and thickness of the obtained films. To study hydrophobicity of each surface, surface free energy measurements were performed. Different DESI-MS responses were observed when different solvent mixture deposition procedures and solvent spray compositions were investigated. Results were finally compared to those obtained by using commercial polytetrafluoroethylene-coated slides. It was found that surface free energy plays an important role in the desorption/ionization process as a function of the polarity of analytes.

Sol-Gel Chemistry for Carbon Dots.

PubMed

Malfatti, Luca; Innocenzi, Plinio

2018-03-14

Carbon dots are an emerging class of carbon-based nanostructures produced by low-cost raw materials which exhibit a widely-tunable photoluminescence and a high quantum yield. The potential of these nanomaterials as a substitute of semiconductor quantum dots in optoelectronics and biomedicine is very high, however they need a customized chemistry to be integrated in host-guest systems or functionalized in core-shell structures. This review is focused on recent advances of the sol-gel chemistry applied to the C-dots technology. The surface modification, the fine tailoring of the chemical composition and the embedding into a complex nanostructured material are the main targets of combining sol-gel processing with C-dots chemistry. In addition, the synergistic effect of the sol-gel precursor combined with the C-dots contribute to modify the intrinsic chemo-physical properties of the dots, empowering the emission efficiency or enabling the tuning of the photoluminescence over a wide range of the visible spectrum. © 2018 The Chemical Society of Japan & Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

Highly efficient up-conversion and bright white light in RE co-doped KYF4 nanocrystals in sol-gel silica matrix

NASA Astrophysics Data System (ADS)

Méndez-Ramos, J.; Yanes, A. C.; Santana-Alonso, A.; del-Castillo, J.

2013-01-01

Transparent nano-glass-ceramics comprising Yb3+, Er3+ and Tm3+ co-doped KYF4 nanocrystals have been developed from sol-gel method. A structural analysis by means of X-ray diffraction confirmed the precipitation of cubic KYF4 nanocrystals into a silica matrix. Visible luminescence has been analyzed as function of treatment temperature of precursor sol-gel glasses. Highly efficient up-conversion emissions have been obtained under 980 nm excitation and studied by varying the doping level, processing temperature and pump power. Color tuneability has been quantified in terms of CIE diagram and in particular, a white-balanced overall emission has been achieved for a certain doping level and thermal treatment.

Phospho-silicate and silicate layers modified by hydroxyapatite particles

NASA Astrophysics Data System (ADS)

Rokita, M.; Brożek, A.; Handke, M.

2005-06-01

Common used metal materials do not ensure good connection between an implant and biological neighbourhood. Covering implants by thin silicate or phosphate layers enable to improve biological properties of implants and create conditions for producing the non-concrete bonding between the implant and tissue. The project includes preparing silicate sols of different concentrations and proper (powder) fraction of synthetic as well as natural ox hydroxyapatite, depositing the sol mixed with hydroxyapatite onto the base material (metal, ceramic carbon) and heat treatment. Our work includes also preparation of phospho-silicate layers deposited onto different base materials using sol-gel method. Deposited sols were prepared regarding composition, concentration and layer heat treatment conditions. The prepared layers are examined to determine their phase composition (XRD, IR spectroscopy methods), density and continuity (scanning microscopy with EDX methods). Biological activity of layers was evaluated by means of estimation of their corrosive resistance in synthetic body fluids ('in vitro' method) and of bone cells growth on the layers surface. Introducing hydroxyapatite to the layer sol should improve connection between tissue and implant as well as limit the disadvantageous, corrosive influence of implant material (metal) on the tissue.

Synthesis and characterization of TiC nanopowders via sol-gel and subsequent carbothermal reduction process

NASA Astrophysics Data System (ADS)

Chen, Xu; Fan, Jinglian; Lu, Qiong

2018-06-01

TiC nanocrystalline powders were synthesized by in-situ carbothermic reduction of Ti-O-C precursor under vacuum atmosphere. And the Ti-O-C precursor was formed by sol-gel method from titanium butyrate (TBOT) and sucrose. To obtain stable sol, TBOT was directly added into mixed solution which contains water, sucrose, acetic acid (AcOH) and acetylacetone (ACAC). This procedure is more convenient and economical because it avoids the use of alcohol which is used as solvent in most reports of alkoxide hydrolysis sol-gel method. TG-DSC, XRD, FTIR and SEM/TEM were employed to analyze and characterize the product during the entire process. The phase composition and crystalline structure parameters of powders with different C/Ti molar ratio were investigated by Rietveld refinement method, and elemental quantitative analysis of the samples were performed. Furthermore, the optimal parameters of carbothermal reduction were obtained and the grain growth mechanism was demonstrated. The results show that TiC nanocrystalline powders (C/Ti molar ratio is 3.5 in the precursor) were synthesized at 1300 °C for 2 h, which have near standard lattice parameter, well crystallinity and fine average grain size ( 37.4 nm).

Electrophoretically active sol-gel processes to backfill, seal, and/or densify porous, flawed, and/or cracked coatings on electrically conductive material

DOEpatents

Panitz, J.K.; Reed, S.T.; Ashley, C.S.; Neiser, R.A.; Moffatt, W.C.

1999-07-20

Electrophoretically active sol-gel processes to fill, seal, and/or density porous, flawed, and/or cracked coatings on electrically conductive substrates. Such coatings may be dielectrics, ceramics, or semiconductors and, by the present invention, may have deposited onto and into them sol-gel ceramic precursor compounds which are subsequently converted to sol-gel ceramics to yield composite materials with various tailored properties. 6 figs.

Antimicrobial Activity of Thin Solid Films of Silver Doped Hydroxyapatite Prepared by Sol-Gel Method

PubMed Central

Iconaru, Simona Liliana; Chapon, Patrick; Le Coustumer, Philippe; Predoi, Daniela

2014-01-01

In this work, the preparation and characterization of silver doped hydroxyapatite thin films were reported and their antimicrobial activity was characterized. Silver doped hydroxyapatite (Ag:HAp) thin films coatings substrate was prepared on commercially pure Si disks by sol-gel method. The silver doped hydroxyapatite thin films were characterized by various techniques such as Scanning electron microscopy (SEM) with energy Dispersive X-ray attachment (X-EDS), Fourier transform infrared spectroscopy (FT-IR), and glow discharge optical emission spectroscopy (GDOES). These techniques have permitted the structural and chemical characterisation of the silver doped hydroxyapatite thin films. The antimicrobial effect of the Ag:HAp thin films on Escherichia coli and Staphylococcus aureus bacteria was then investigated. This is the first study on the antimicrobial effect of Ag:HAp thin films obtained by sol-gel method. The results of this study have shown that the Ag:HAp thin films with x Ag = 0.5 are effective against E. coli and S. aureus after 24 h. PMID:24523630

Tubular structured hierarchical mesoporous titania material derived from natural cellulosic substances and application as photocatalyst for degradation of methylene blue

DOE Office of Scientific and Technical Information (OSTI.GOV)

Huang, Haiqing; Liu, Xiaoyan; Huang, Jianguo, E-mail: jghuang@zju.edu.cn

Graphical abstract: Bio-inspired, tubular structured hierarchical mesoporous titania material with high photocatalytic activity under UV light was fabricated employing natural cellulosic substance (cotton) as hard template and cetyltrimethylammonium bromide (CTAB) surfactant as soft template using a one-pot sol-gel method. Highlights: {yields} Tubular structured mesoporous titania material was fabricated by sol-gel method. {yields} The titania material faithfully recorded the hierarchical structure of the template substrate (cotton). {yields} The titania material exhibited high photocatalytic activity in decomposition of methylene blue. -- Abstract: Bio-inspired, tubular structured hierarchical mesoporous titania material was designed and fabricated employing natural cellulosic substance (cotton) as hard template andmore » cetyltrimethylammonium bromide (CTAB) surfactant as soft template by one-pot sol-gel method. The tubular structured hierarchical mesoporous titania material processes large specific surface area (40.23 m{sup 2}/g) and shows high photocatalytic activity in the photodegradation of methylene blue under UV light irradiation.« less

Antimicrobial activity of thin solid films of silver doped hydroxyapatite prepared by sol-gel method.

PubMed

Iconaru, Simona Liliana; Chapon, Patrick; Le Coustumer, Philippe; Predoi, Daniela

2014-01-01

In this work, the preparation and characterization of silver doped hydroxyapatite thin films were reported and their antimicrobial activity was characterized. Silver doped hydroxyapatite (Ag:HAp) thin films coatings substrate was prepared on commercially pure Si disks by sol-gel method. The silver doped hydroxyapatite thin films were characterized by various techniques such as Scanning electron microscopy (SEM) with energy Dispersive X-ray attachment (X-EDS), Fourier transform infrared spectroscopy (FT-IR), and glow discharge optical emission spectroscopy (GDOES). These techniques have permitted the structural and chemical characterisation of the silver doped hydroxyapatite thin films. The antimicrobial effect of the Ag:HAp thin films on Escherichia coli and Staphylococcus aureus bacteria was then investigated. This is the first study on the antimicrobial effect of Ag:HAp thin films obtained by sol-gel method. The results of this study have shown that the Ag:HAp thin films with x(Ag) = 0.5 are effective against E. coli and S. aureus after 24 h.

Iron specificity of a biosensor based on fluorescent pyoverdin immobilized in sol-gel glass

PubMed Central

2011-01-01

Two current technologies used in biosensor development are very promising: 1. The sol-gel process of making microporous glass at room temperature, and 2. Using a fluorescent compound that undergoes fluorescence quenching in response to a specific analyte. These technologies have been combined to produce an iron biosensor. To optimize the iron (II or III) specificity of an iron biosensor, pyoverdin (a fluorescent siderophore produced by Pseudomonas spp.) was immobilized in 3 formulations of porous sol-gel glass. The formulations, A, B, and C, varied in the amount of water added, resulting in respective R values (molar ratio of water:silicon) of 5.6, 8.2, and 10.8. Pyoverdin-doped sol-gel pellets were placed in a flow cell in a fluorometer and the fluorescence quenching was measured as pellets were exposed to 0.28 - 0.56 mM iron (II or III). After 10 minutes of exposure to iron, ferrous ion caused a small fluorescence quenching (89 - 97% of the initial fluorescence, over the range of iron tested) while ferric ion caused much greater quenching (65 - 88%). The most specific and linear response was observed for pyoverdin immobilized in sol-gel C. In contrast, a solution of pyoverdin (3.0 μM) exposed to iron (II or III) for 10 minutes showed an increase in fluorescence (101 - 114%) at low ferrous concentrations (0.45 - 2.18 μM) while exposure to all ferric ion concentrations (0.45 - 3.03 μM) caused quenching. In summary, the iron specificity of pyoverdin was improved by immobilizing it in sol-gel glass C. PMID:21554740

Relationship between sol-gel conditions and enzyme stability: a case study with β-galactosidase/silica biocatalyst for whey hydrolysis.

PubMed

Escobar, Sindy; Bernal, Claudia; Mesa, Monica

2015-01-01

The sol-gel process has been very useful for preparing active and stable biocatalysts, with the possibility of being reused. Especially those based on silica are well known. However, the study of the enzyme behavior during this process is not well understood until now and more, if the surfactant is involved in the synthesis mixture. This work is devoted to the encapsulation of β-galactosidase from Bacillus circulans in silica by sol-gel process, assisted by non-ionic Triton X-100 surfactant. The correlation between enzyme activity results for the β-galactosidase in three different environments (soluble in buffered aqueous reference solution, in the silica sol, and entrapment on the silica matrix) explains the enzyme behavior under stress conditions offered by the silica sol composition and gelation conditions. A stable β-galactosidase/silica biocatalyst is obtained using sodium silicate, which is a cheap source of silica, in the presence of non-ionic Triton X-100, which avoids the enzyme deactivation, even at 40 °C. The obtained biocatalyst is used in the whey hydrolysis for obtaining high value products from this waste. The preservation of the enzyme stability, which is one of the most important challenges on the enzyme immobilization through the silica sol-gel, is achieved in this study.

Effects of inorganic acids and divalent hydrated metal cations (Mg(2+), Ca(2+), Co(2+), Ni(2+)) on γ-AlOOH sol-gel process.

PubMed

Zhang, Jian; Xia, Yuguo; Zhang, Li; Chen, Dairong; Jiao, Xiuling

2015-11-07

In-depth understanding of the sol-gel process plays an essential role in guiding the preparation of new materials. Herein, the effects of different inorganic acids (HCl, HNO3 and H2SO4) and divalent hydrated metal cations (Mg(2+), Ca(2+), Co(2+), Ni(2+)) on γ-AlOOH sol-gel process were studied based on experiments and density functional theory (DFT) calculations. In these experiments, the sol originating from the γ-AlOOH suspension was formed only with the addition of HCl and HNO3, but not with H2SO4. Furthermore, the DFT calculations showed that the strong adsorption of HSO4(-) on the surface of the γ-AlOOH particles, and the hydrogen in HSO4(-) pointing towards the solvent lead to an unstable configuration of electric double layer (EDL). In the experiment, the gelation time sequence of γ-AlOOH sol obtained by adding metal ions changed when the ionic strength was equal to or greater than 0.198 mol kg(-1). The DFT calculations demonstrated that the adsorption energy of hydrated metal ions on the γ-AlOOH surface can actually make a difference in the sol-gel process.

Exploring encapsulation mechanism of DNA and mononucleotides in sol-gel derived silica.

PubMed

Kapusuz, Derya; Durucan, Caner

2017-07-01

The encapsulation mechanism of DNA in sol-gel derived silica has been explored in order to elucidate the effect of DNA conformation on encapsulation and to identify the nature of chemical/physical interaction of DNA with silica during and after sol-gel transition. In this respect, double stranded DNA and dAMP (2'-deoxyadenosine 5'-monophosphate) were encapsulated in silica using an alkoxide-based sol-gel route. Biomolecule-encapsulating gels have been characterized using UV-Vis, 29 Si NMR, FTIR spectroscopy and gas adsorption (BET) to investigate chemical interactions of biomolecules with the porous silica network and to examine the extent of sol-gel reactions upon encapsulation. Ethidium bromide intercalation and leach out tests showed that helix conformation of DNA was preserved after encapsulation. For both biomolecules, high water-to-alkoxide ratio promoted water-producing condensation and prevented alcoholic denaturation. NMR and FTIR analyses confirmed high hydraulic reactivity (water adsorption) for more silanol groups-containing DNA and dAMP encapsulated gels than plain silica gel. No chemical binding/interaction occurred between biomolecules and silica network. DNA and dAMP encapsulated silica gelled faster than plain silica due to basic nature of DNA or dAMP containing buffer solutions. DNA was not released from silica gels to aqueous environment up to 9 days. The chemical association between DNA/dAMP and silica host was through phosphate groups and molecular water attached to silanols, acting as a barrier around biomolecules. The helix morphology was found not to be essential for such interaction. BET analyses showed that interconnected, inkbottle-shaped mesoporous silica network was condensed around DNA and dAMP molecules.

Fabrication of highly uniform and porous MgF2 anti-reflective coatings by polymer-based sol-gel processing on large-area glass substrates.

PubMed

Raut, Hemant Kumar; Dinachali, Saman Safari; Ansah-Antwi, Kwadwo Konadu; Ganesh, V Anand; Ramakrishna, Seeram

2013-12-20

Despite recent progress in the fabrication of magnesium fluoride (MgF2) anti-reflective coatings (ARCs), simple, effective and scalable sol-gel fabrication of MgF2 ARCs for large-area glass substrates has prospective application in various optoelectronic devices. In this paper, a polymer-based sol-gel route was devised to fabricate highly uniform and porous MgF2 ARCs on large-area glass substrates. A sol-gel precursor made of polyvinyl acetate and magnesium trifluoroacetate assisted in the formation of uniformly mesoporous MgF2 ARCs on glass substrates, leading to the attainment of a refractive index of ~1.23. Systematic optimization of the thickness of the ARC in the sub-wavelength regime led to achieving ~99.4% transmittance in the case of the porous MgF2 ARC glass. Precise control of the thickness of porous MgF2 ARC glass also resulted in a mere ~0.1% reflection, virtually eliminating reflection off the glass surface at the target wavelength. Further manipulation of the thickness of the ARC on either side of the glass substrate led to the fabrication of relatively broadband, porous MgF2 ARC glass.

A Sol-Gel-Modified Poly(methyl methacrylate) Electrophoresis Microchip with a Hydrophilic Channel Wall

DOE Office of Scientific and Technical Information (OSTI.GOV)

Chen, Gang; Xu, Xuejiao; Lin, Yuehe

2007-07-27

A sol-gel method was employed to fabricate a poly(methyl methacrylate) (PMMA) electrophoresis microchip that contains a hydrophilic channel wall. To fabricate such a device, tetraethoxysilane (TEOS) was injected into the PMMA channel and was allowed to diffuse into the surface layer for 24 h. After removing the excess TEOS, the channel was filled with an acidic solution for 3 h. Subsequently, the channel was flushed with water and was pretreated in an oven to obtain a sol-gel-modified PMMA microchip. The water contact angle for the sol-gel-modified PMMA was 27.4° compared with 66.3° for the pure PMMA. In addition, the electro-osmoticmore » flow increased from 2.13×10-4 cm2 V-1 s-1 for the native-PMMA channel to 4.86×10-4 cm2 V-1 s-1 for the modified one. The analytical performance of the sol-gel-modified PMMA microchip was demonstrated for the electrophoretic separation of several purines, coupled with amperometric detection. The separation efficiency of uric acid increased to 74 882.3 m-1 compared with 14 730.5 m-1 for native-PMMA microchips. The result of this simple modification is a significant improvement in the performance of PMMA for microchip electrophoresis and microfluidic applications.« less

Sol-gel chemical sensors for surface-enhanced Raman spectroscopy

NASA Astrophysics Data System (ADS)

Lee, Vincent Y.; Farquharson, Stuart; Kwon, Hueong-Chan; Shahriari, Mahmoud R.; Rainey, Petrie M.

1999-02-01

Surface-enhanced Raman spectroscopy (SERS) promises to be one of the most sensitive methods for chemical detection. Unfortunately, the inability of SERS to perform quantitative chemical analysis has slowed its general use in laboratories. This is largely due to the difficulty of manufacturing either active surfaces that yield reproducible enhancements, or surfaces that are capable of reversible chemical adsorption, or both. In an effort to meet this need, we have developed metal-doped sol-gels that provide surface-enhancement of Raman scattering. The porous silica network offers a unique environment for stabilizing SER active metal particles and the high surface area increases the interaction between the analyte and metal particles. This eliminates the need to concentrate the analyte on the surface by evaporating the solvent. The sol-gel is easily coated on a variety of surfaces, such as fiber optics, glass slides, or glass tubing, and can be designed into sample flow systems. Here we present the development of both gold- and silver-doped sol-gels, which have been used to coat the inside walls of glass sample vials for SERS applications. The performance of the metal-doped sol-gels was evaluated using p-aminobenzoic acid, to establish enhancement factors, detection limits, dynamic response range, reversibility, reproducibility, and suitability to commercial spectrometers. Measurements of trace chemicals, such as adenine and cocaine, are also presented.

KOH catalysed preparation of activated carbon aerogels for dye adsorption.

PubMed

Ling, Sie King; Tian, H Y; Wang, Shaobin; Rufford, Thomas; Zhu, Z H; Buckley, C E

2011-05-01

Organic carbon aerogels (CAs) were prepared by a sol-gel method from polymerisation of resorcinol, furfural, and hexamethylenetetramine catalysed by KOH at around pH 9 using ambient pressure drying. The effect of KOH in the sol-gel on CA synthesis was studied. It was found that addition of KOH prior to the sol-gel polymerisation process improved thermal stability of the gel, prevented the crystallinity of the gel to graphite, increased the microporosity of CA and promoted activation of CA. The CAs prepared using the KOH catalyst exhibited higher porosity than uncatalysed prepared samples. Activation in CO(2) at higher temperature also enhanced the porosity of CAs. Adsorption tests indicated that the CAs were effective for both basic and acid dye adsorption and the adsorption increased with increasing surface area and pore volume. The kinetic adsorption of dyes was diffusion control and could be described by the second-order kinetic model. The equilibrium adsorption of dyes was higher than activated carbon. Copyright © 2011 Elsevier Inc. All rights reserved.

Production of Monodisperse Cerium Oxide Microspheres with Diameters near 100 µm by Internal-Gelation Sol-Gel Methods

DOE Office of Scientific and Technical Information (OSTI.GOV)

Katalenich, Jeffrey A.; Kitchen, Brian B.; Pierson, Bruce

Cerium dioxide microspheres with uniform diameters between 65 – 211 µm were fabricated using internal gelation sol-gel methods. Although uniform microspheres are produced for nuclear fuel applications with diameters above 300 µm, sol-gel microspheres with diameters of 50 - 200 µm have historically been made by emulsion techniques and had poor size uniformity [1, 2]. An internal gelation, sol-gel apparatus was designed and constructed to accommodate the production of small, uniform microspheres whereby cerium-containing solutions were dispersed into flowing silicone oil and heated in a gelation column to initiate solidification [3, 4]. Problems with premature feed gelation and microsphere coalescencemore » were overcome by equipment modifications unique among known internal gelation setups. Microspheres were fabricated and sized in batches as a function of dispersing needle diameter and silicone oil flow rate in the two-fluid nozzle in order to determine the range of sizes possible and corresponding degree of monodispersity. Initial experiments with poor size uniformity were linked to microsphere coalescence in the gelation column prior to solidification as well as excessive flow rates for the cerium feed solution. Average diameter standard deviations as low as 2.23% were observed after optimization of flow rates and minimization of coalescence reactions.« less

Ultra-small dye-doped silica nanoparticles via modified sol-gel technique

NASA Astrophysics Data System (ADS)

Riccò, R.; Nizzero, S.; Penna, E.; Meneghello, A.; Cretaio, E.; Enrichi, F.

2018-05-01

In modern biosensing and imaging, fluorescence-based methods constitute the most diffused approach to achieve optimal detection of analytes, both in solution and on the single-particle level. Despite the huge progresses made in recent decades in the development of plasmonic biosensors and label-free sensing techniques, fluorescent molecules remain the most commonly used contrast agents to date for commercial imaging and detection methods. However, they exhibit low stability, can be difficult to functionalise, and often result in a low signal-to-noise ratio. Thus, embedding fluorescent probes into robust and bio-compatible materials, such as silica nanoparticles, can substantially enhance the detection limit and dramatically increase the sensitivity. In this work, ultra-small fluorescent silica nanoparticles (NPs) for optical biosensing applications were doped with a fluorescent dye, using simple water-based sol-gel approaches based on the classical Stöber procedure. By systematically modulating reaction parameters, controllable size tuning of particle diameters as low as 10 nm was achieved. Particles morphology and optical response were evaluated showing a possible single-molecule behaviour, without employing microemulsion methods to achieve similar results. [Figure not available: see fulltext.

Fabrication and characterization of sol-gel derived 45S5 Bioglass®-ceramic scaffolds.

PubMed

Chen, Qi-Zhi; Thouas, George A

2011-10-01

Although Bioglass® has existed for nearly half a century its ability to trigger bone formation and tuneable degradability is vastly superior to other bioceramics, such as SiO(2)-CaO bioactive glasses. The sol-gel process of producing glass foams is well established for SiO(2)-CaO compositions, but not yet established for 45S5 composites containing Na(2)O. In this work the sol-gel derived 45S5 Bioglass® has for the first time been foamed into highly porous three-dimensional scaffolds using a surfactant, combined with vigorous mechanical stirring and subsequent sintering at 1000°C for 2 h. It was found that the mechanical strength of the sintered sol-gel derived Bioglass® scaffolds was significantly improved, attributable to the small fraction of material on the pore walls. More importantly, the compressive strength of the three-dimensional scaffolds produced by this surfactant foaming method could be predicted using Gibson and Ashby's closed cell model of porous networks. A comparative experiment revealed that ion release from the sol-gel derived Bioglass® foams was faster than that of counterparts produced by the replication technique. In vitro evaluation using osteoblast-like cells demonstrated that the sol-gel derived 45S5 Bioglass foams supported the proliferation of viable cell populations on the surface of the scaffolds, although few cells were observed to migrate into the virtually closed pores within the foams. Further work should be focused on modifications of the reaction conditions or alternative foaming techniques to improve pore interconnection. Copyright © 2011 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.

Functionalizable Sol-Gel Silica Coatings for Corrosion Mitigation.

PubMed

Gąsiorek, Jolanta; Szczurek, Anna; Babiarczuk, Bartosz; Kaleta, Jerzy; Jones, Walis; Krzak, Justyna

2018-01-26

Corrosion is constantly a major problem of the world economy in the field of metal products, metal processing and other areas that utilise metals. Previously used compounds utilizing hexavalent chromium were amongst the most effective materials for corrosion protection but regulations have been recently introduced that forbid their use. Consequently, there is a huge drive by engineers, technologists and scientists from different disciplines focused on searching a new, more effective and environmentally-friendly means of corrosion protection. One novel group of materials with the potential to solve metal protection problems are sol-gel thin films, which are increasingly interesting as mitigation corrosion barriers. These environmentally-friendly and easy-to-obtain coatings have the promise to be an effective alternative to hexavalent chromium compounds using for anti-corrosion industrial coatings. In this review the authors present a range of different solutions for slow down the corrosion processes of metallic substrates by using the oxides and doped oxides obtained by the sol-gel method. Examples of techniques used to the sol-gel coating examinations, in terms of anti-corrosion protection, are also presented.

Effects of sol-gel processing parameters on the phases and microstructures of HA films.

PubMed

Wang, Diangang; Chen, Chuanzhong; Liu, Xiuna; Lei, Tingquan

2007-06-15

Bioactive hydroxyapatite (HA) films were fabricated by a sol-gel method and triethylphosphate and calcium nitrate were used as the phosphorus and calcium precursors, respectively. The effects of the heat treatment temperature, pH level and substrate materials on the phases and microstructures of HA films were studied by X-ray diffraction (XRD), scanning electronic microscopy (SEM) and electronic probe microanalysis (EPMA) and so on. The results show that all the sol-gel films are composed of the phases of HA, CaO, TiO(2) and CaTiO(3). With increasing the calcining temperature, the crystallinity of the films increases, the structure becomes more compact and changes from granular and lamellar to cellular structure, and the Ca/P ratio increases slightly because of the loss of P in the films. The addition of ammonia (adjusting the pH level to be about 7.5) can increase the HA content in the films, and the difference of substrate materials only has a little influence on the microstructure of the sol-gel films.

Functionalizable Sol-Gel Silica Coatings for Corrosion Mitigation

PubMed Central

Gąsiorek, Jolanta; Babiarczuk, Bartosz; Kaleta, Jerzy; Jones, Walis; Krzak, Justyna

2018-01-01

Corrosion is constantly a major problem of the world economy in the field of metal products, metal processing and other areas that utilise metals. Previously used compounds utilizing hexavalent chromium were amongst the most effective materials for corrosion protection but regulations have been recently introduced that forbid their use. Consequently, there is a huge drive by engineers, technologists and scientists from different disciplines focused on searching a new, more effective and environmentally-friendly means of corrosion protection. One novel group of materials with the potential to solve metal protection problems are sol-gel thin films, which are increasingly interesting as mitigation corrosion barriers. These environmentally-friendly and easy-to-obtain coatings have the promise to be an effective alternative to hexavalent chromium compounds using for anti-corrosion industrial coatings. In this review the authors present a range of different solutions for slow down the corrosion processes of metallic substrates by using the oxides and doped oxides obtained by the sol-gel method. Examples of techniques used to the sol-gel coating examinations, in terms of anti-corrosion protection, are also presented. PMID:29373540

Method of making particles from an aqueous sol

DOEpatents

Rankin, G.W.; Hooker, J.R.

1973-07-24

A process for preparing gel particles from an aqueous sol by forming the sol into droplets in a liquid system wherein the liquid phase contains a liquid organic solvent and a barrier agent. The barrier agent prevents dehydration from occurring too rapidly and permits surface tension effects to form sol droplets into the desired spheroidal shape. A preferred barrier agent is mineral oil. (Official Gazette)

Sol gel derived hydroxyapatite coatings on titanium and its alloy Ti6Al4V

NASA Astrophysics Data System (ADS)

Stoch, A.; Jastrzebski, W.; Długoń, E.; Lejda, W.; Trybalska, B.; Stoch, G. J.; Adamczyk, A.

2005-06-01

Titanium has been used for many medical and dental applications; however, its joining to a living bone is not satisfactorily good or the implant integration with bone tissue takes several months.The aim of this work is to produce hydroxyapatite (HAP) coatings on titanium and its alloy for facilitating and shortening the processes towards osseointegration. HAP coatings were obtained by sol-gel method with sol solutions prepared from calcium nitrate tetrahydrate and triammonium phosphate trihydrate as the calcium and phosphorous sources. Two types of gelatine were added to the sol: agar-agar or animals gelatine. Both were found to enhance the formation and stability of amorphous HAP using soluble salts as the sources of calcium and phosphate. HAP coatings were deposited from HAP-GEL sol using dip-withdrawal technique, then the plates were dried and annealed at temperatures 460-750 °C. FTIR spectroscopy and XRD analysis were used to study the phase composition of phosphate coatings. Morphology and chemical analysis of HAP layers was performed using a scanning electron microscope equipped with an energy dispersive X-ray analyser (SEM+EDX). The biological activity of sol-gel phosphate coatings was observed during thermostatic held in simulated body fluid (SBF). It was found that chemical composition and structure of HAP coatings depends on pH and final thermal treatment of the layer.

Fabrication of silica ceramic membrane via sol-gel dip-coating method at different nitric acid amount

NASA Astrophysics Data System (ADS)

Kahlib, N. A. Z.; Daud, F. D. M.; Mel, M.; Hairin, A. L. N.; Azhar, A. Z. A.; Hassan, N. A.

2018-01-01

Fabrication of silica ceramics via the sol-gel method has offered more advantages over other methods in the fabrication of ceramic membrane, such as simple operation, high purity homogeneous, well defined-structure and complex shapes of end products. This work presents the fabrication of silica ceramic membrane via sol-gel dip-coating methods by varying nitric acid amount. The nitric acid plays an important role as catalyst in fabrication reaction which involved hydrolysis and condensation process. The tubular ceramic support, used as the substrate, was dipped into the sol of Tetrethylorthosilicate (TEOS), distilled water and ethanol with the addition of nitric acid. The fabricated silica membrane was then characterized by (Field Emission Scanning Electron Microscope) FESEM and (Fourier transform infrared spectroscopy) FTIR to determine structural and chemical properties at different amount of acids. From the XRD analysis, the fabricated silica ceramic membrane showed the existence of silicate hydrate in the final product. FESEM images indicated that the silica ceramic membrane has been deposited on the tubular ceramic support as a substrate and penetrate into the pore walls. The intensity peak of FTIR decreased with increasing of amount of acids. Hence, the 8 ml of acid has demonstrated the appropriate amount of catalyst in fabricating good physical and chemical characteristic of silica ceramic membrane.

Thermostability of glucose oxidase in silica gel obtained by sol-gel method and in solution studied by fluorimetric method.

PubMed

Przybyt, Małgorzata; Miller, Ewa; Szreder, Tomasz

2011-04-04

The thermostability of glucose oxidase entrapped in silica gel obtained by sol-gel method was studied by thermostimulated fluorescence of FAD at pH 5 and 7 and compared with that of the native enzyme in the solution and at the presence of ethanol. The unfolding temperatures were found to be lower for the enzyme immobilised in gel as compared with the native enzyme but higher as for the enzyme at the presence of ethanol. In gel, the thermal denaturation of glucose oxidase is independent on pH while in solution the enzyme is more stable at pH 5. The investigation the enzyme in different environment by steady-state fluorescence of FAD and tryptophan, synchronous fluorescence and time-resolved fluorescence of tryptophan indicates that the state of the molecule (tertiary structure and molecular dynamics) is different in gel and in solution. The ethanol produced during gel precursor hydrolysis is not the main factor influencing the thermostability of the enzyme but more important are interactions of the protein with the gel lattice. Copyright © 2011 Elsevier B.V. All rights reserved.

Synthesis and characterization of thick PZT films via sol-gel dip coating method

NASA Astrophysics Data System (ADS)

Shakeri, Amid; Abdizadeh, Hossein; Golobostanfard, Mohammad Reza

2014-09-01

Thick films of lead zirconate titanate (PZT) offer possibilities for micro-electro-mechanical systems such as high frequency ultrasonic transducers. In this paper, crack-free thick films of PZT have been prepared up to 45 μm thickness via modified sol-gel dip coating method. In this procedure, acetic acid-alcoholic based sol is used by applying diethanolamine (DEA) and deionized water as additives. The effects of DEA and water on the crystal structure and surface morphology of the films are investigated. The mechanisms of acetic acid and DEA complexations are introduced by using FTIR spectrometer which illustrates suitable substitution of complexing agents with alkoxide groups. DEA/(Ti + Zr) = 0.5 or water/(Ti + Zr) = 0.5 are determined as the optimum molar ratio of additives, which lead to the formation of almost pure perovskite phase with the tetragonal lattice parameters of ct = 4.16 Ǻ and at = 4.02 Ǻ and a distortion of 2%. Values of remanent polarization and dielectric constant of 7.8 μC cm-2 and 1630 were obtained for 45 μm thick films, respectively.

Mimicking Nature: Self-strengthening Properties in a Dental Adhesive

PubMed Central

Song, Linyong; Ye, Qiang; Ge, Xueping; Misra, Anil; Spencer, Paulette

2016-01-01

Chemical and enzymatic hydrolysis provoke a cascade of events that undermine methacrylate-based adhesives and the bond formed at the tooth/composite interface. Infiltration of noxious agents, e.g. enzymes, bacteria, and so forth, into the spaces created by the defective bond will ultimately lead to failure of the composite restoration. This paper reports a novel, synthetic resin that provides enhanced hydrolytic stability as a result of intrinsic reinforcement of the polymer network. The behavior of this novel resin, which contains γ-methacryloxyproyl trimethoxysilane (MPS) as its Si-based compound, is reminiscent of self-strengthening properties found in nature. The efforts in this paper are focused on two essential aspects: the visible-light irradiation induced (photoacid-induced) sol-gel reaction and the mechanism leading to intrinsic self-strengthening. The FTIR band at 2840 cm−1 corresponding to CH3 symmetric stretch in −Si−O−CH3 was used to evaluate the sol-gel reaction. Results from the real-time FTIR indicated that the newly developed resin showed a limited sol-gel reaction (<5%) during visible-light irradiation, but after 48h dark storage, the reaction was over 65%. The condensation of methoxysilane mainly occurred under wet conditions. The storage moduli and glass transition temperature of the copolymers increased in wet conditions with the increasing MPS content. The cumulative amounts of leached species decreased significantly when the MPS-containing adhesive was used. The results suggest that the polymethacrylate-based network, which formed first as a result of free radical initiated polymerization, retarded the photoacid-induced sol-gel reaction. The sol-gel reaction provided a persistent, intrinsic reinforcement of the polymer network in both neutral and acidic conditions. This behavior led to enhanced mechanical properties of the dental adhesives under conditions that simulate the wet, oral environment. PMID:26883773

Layer-by-Layer Self-Assembling Gold Nanorods and Glucose Oxidase onto Carbon Nanotubes Functionalized Sol-Gel Matrix for an Amperometric Glucose Biosensor.

PubMed

Wu, Baoyan; Hou, Shihua; Miao, Zhiying; Zhang, Cong; Ji, Yanhong

2015-09-18

A novel amperometric glucose biosensor was fabricated by layer-by-layer self-assembly of gold nanorods (AuNRs) and glucose oxidase (GOD) onto single-walled carbon nanotubes (SWCNTs)-functionalized three-dimensional sol-gel matrix. A thiolated aqueous silica sol containing SWCNTs was first assembled on the surface of a cleaned Au electrode, and then the alternate self-assembly of AuNRs and GOD were repeated to assemble multilayer films of AuNRs-GOD onto SWCNTs-functionalized silica gel for optimizing the biosensor. Among the resulting glucose biosensors, the four layers of AuNRs-GOD-modified electrode showed the best performance. The sol-SWCNTs-(AuNRs- GOD)₄/Au biosensor exhibited a good linear range of 0.01-8 mM glucose, high sensitivity of 1.08 μA/mM, and fast amperometric response within 4 s. The good performance of the proposed glucose biosensor could be mainly attributed to the advantages of the three-dimensional sol-gel matrix and stereo self-assembly films, and the natural features of one-dimensional nanostructure SWCNTs and AuNRs. This study may provide a new facile way to fabricate the enzyme-based biosensor with high performance.

One pot synthesis of exchange coupled Nd2Fe14B/alpha-Fe by pechini type sol-gel method.

PubMed

Hussain, Abid; Jadhav, Abhijit P; Baek, Yeon Kyung; Choi, Hul Jin; Lee, Jaeho; Kang, Young Soo

2013-11-01

In this work, a combination of nanoparticles of Nd2Fe14B hard magnetic phase and alpha-Fe soft magnetic phase were synthesized by one pot chemical synthesis technique using sol-gel method. A gel of Nd-Fe-B was prepared using NdCl3 x 6H2O, FeCl3 x 6H2O, H3BO3, citric acid, and ethylene glycol by pechini type sol-gel method. The gel was subsequently calcined and annealed to obtain the mixed oxide powders. The produced metal oxide particles were identified with XRD, SEM, TEM to obtain the crystal structure, shape and domain structure of them. The nanoparticles of mixed phase of Nd2Fe14B/alpha-Fe were obtained from these oxides by a process of reduction-diffusion in vacuum by employing CaH2 as reducing agent. During this process it was optimized by controlling temperature, reaction time and concentration of the reducing agent (CaH2). The phase formation of Nd2Fe14B was resulted by the direct diffusion of NdH2, Fe and B. The magnetic property of produced hard and soft phases was successfully identified with vibrating sample magnetometer (VSM). The mixed domains of the hard and soft phases were identified with selected area electron diffraction method (SAED) patterns.

Raman study of TiO2 coatings modified by UV pulsed laser

NASA Astrophysics Data System (ADS)

Belka, Radosław; Keczkowska, Justyna; Sek, Piotr

2016-12-01

The TiO2 coatings were prepared by simple sol-gel method and modified by UV pulsed laser. TiO2, also know as titania, is a ceramic compound, existing in numerous polymorphic forms, mainly as tetragonal rutile and anatase, and rhomboidal brookite. Rutile is the most stable form of titanium dioxide, whereas anatase is a metastable form, created in lower temperatures than rutile. Anatase is marked with higher specific surface area, porosity and a higher number of surface hydroxyl groups as compared to rutile. The unique optical and electronic properties of TiO2 results in its use as semiconductors dielectric mirrors, sunscreen and UV-blocking pigments and especially as photocatalyst. In this paper, the tetraisopropoxide was used as Ti precursor according to sol-gel method. An organic base was applied during sol preparation. Prepared gel was coated on glass substrates and calcined in low temperature to obtain amorphous phase of titania. Prepared coatings were modified by UV picosecond pulse laser with different pulse repetition rate and pulse power. Physical modification of the coatings using laser pulses was intended in order change the phase content of the produced material. Raman spectroscopy (RS) method was applied to studies of modified coatings as it is one of the basic analytical techniques, supporting the identification of compounds and obtaining information about the structure. Especially, RS is a useful method for distinguishing the anatase and rutile phases. In these studies, anatase to rutile transformation was observed, depending on laser parameters.

Comparing nanostructured hydroxyapatite coating on AZ91 alloy samples via sol-gel and electrophoretic deposition for biomedical applications.

PubMed

Rojaee, Ramin; Fathi, Mohammadhossein; Raeissi, Keyvan

2014-12-01

Magnesium is one of the most critical elements in hard tissues regeneration and therefore causes speeding up the restoration of harmed bones, while high deterioration rate of magnesium in body fluid restricts it to be used as biodegradable implants. Alloying magnesium with some relatively nobler metals such as aluminium, zinc, rare earth elements, magnesium-bioceramics composites, and surface modification techniques are some of the routes to control magnesium corrosion rate. In this study AZ91 magnesium alloy had been coated by nanostructured hydroxyapatite via sol-gel dip coating and electrophoretical methods to survey the final barricade properties of the obtained coatings. In order to perform electrophoretic coating, powders were prepared by sol-gel method, and then the powders deposited on substrates utilizing direct current electricity. Zeta potentials of the electrophoresis suspensions were measured to determine a best mode for good quality coatings. Transmission Electron Microscopy (TEM), and Scanning Electron Microscopy (SEM) were used to confirm nanoscale dimension, and the uniformity of the nanostructured hydroxyapatite coating, respectively. Fourier Transform-Infrared and X-ray diffraction analysis were utilized for functional group and phase structure evaluation of the prepared coatings, correspondingly. Electrochemical corrosion tests were performed in SBF at 37±1 (°)C which revealed considerable increase in corrosion protection resistivity and corrosion current density for electrophoretic coated specimens versus sol-gel coated specimens. Results showed that both sol-gel and electrophoretical techniques seem to be suitable to coat magnesium alloys for biomedical applications but electrophoretic coating technique is a better choice due to the more homogeneity and more crystalline structure of the coating.

Solid-state NMR study of geopolymer prepared by sol-gel chemistry

DOE Office of Scientific and Technical Information (OSTI.GOV)

Tsai, Yi-Ling; Hanna, John V.; Lee, Yuan-Ling, E-mail: yuanlinglee@ntu.edu.t

2010-12-15

Geopolymers are a new class of materials formed by the condensation of aluminosilicates and silicates obtained from natural minerals or industrial wastes. In this work, the sol-gel method is used to synthesize precursor materials for the preparation of geopolymers. The geopolymer samples prepared by our synthetic route have been characterized by a series of physical techniques, including Fourier-transform infrared, X-ray diffraction, and multinuclear solid-state NMR. The results are very similar to those obtained for the geopolymers prepared from natural kaolinite. We believe that our synthetic approach can offer a good opportunity for the medical applications of geopolymer. -- Graphical abstract:more » Geopolymer prepared by the sol-gel route has the same spectroscopic properties as the sample prepared from the natural kaolinite. Display Omitted« less

Rational construction of gel-based supramolecular logic gates by using a functional gelator with multiple-stimuli responsive properties.

PubMed

Fan, Kaiqi; Yang, Jun; Wang, Xiaobo; Song, Jian

2014-11-07

A gelator containing a sorbitol moiety and a naphthalene-based salicylideneaniline group exhibits macroscopic gel-sol behavior in response to four complementary input stimuli: temperature, UV light, OH(-), and Cu(2+). On the basis of its multiple-stimuli responsive properties, we constructed a rational gel-based supramolecular logic gate that performed OR and INH types of reversible stimulus responsive gel-sol transition in the presence of various combinations of the four stimuli when the gel state was defined as an output. Moreover, a combination two-output logic gate was obtained, owing to the existence of the naked eye as an additional output. Hence, gelator 1 could construct not only a basic logic gate, but also a two-input-two-output logic gate because of its response to multiple chemical stimuli and multiple output signals, in which one input could erase the effect of another input.

Preparation of nickel oxide thin films at different annealing temperature by sol-gel spin coating method

DOE Office of Scientific and Technical Information (OSTI.GOV)

Abdullah, M. A. R., E-mail: ameerridhwan89@gmail.com; Mamat, M. H., E-mail: hafiz-030@yahoo.com; Ismail, A. S., E-mail: kyrin-samaxi@yahoo.com

2016-07-06

Preparation of NiO thin films at different annealing temperature by sol-gel method was conducted to synthesize the quality of the surface thin films. The effects of annealing temperature on the surface topology were systematically investigated. Our studies confirmed that the surface roughness of the thin films was increased whenever annealing temperature was increase. NiO thin films morphology structure analysis was confirmed by field emission scanning electron microscope. Surface roughness of the thin films was investigated by atomic force microscopy.

Method and apparatus for controlled size distribution of gel microspheres formed from aqueous dispersions. [Patent application

DOEpatents

Ryon, A.D.; Haas, P.A.; Vavruska, J.S.

1982-01-19

The present invention is directed to a method and apparatus for making a population of dense, closely size-controlled microspheres by sol-gel procedures wherein said microspheres are characterized by a significant percentage of said population being within a predetermined, relatively narrow size range. This is accomplished by subjecting aqueous dispersions of a sol, within a water-immiscible organic liquid to a turbulent flow. Microsphere populations thus provided are useful in vibratory-packed processes for nuclear fuels to be irradiated in LWR- and FBR-type nuclear reactors.

Switchable vanadium oxide films by a sol-gel process

NASA Astrophysics Data System (ADS)

Partlow, D. P.; Gurkovich, S. R.; Radford, K. C.; Denes, L. J.

1991-07-01

Thin polycrystalline films of VO2 and V2O3 were deposited on a variety of substrates using a sol-gel process. The orientation, microstructure, optical constants, and optical and electrical switching behavior are presented. These films exhibited sharp optical switching behavior even on an amorphous substrate such as fused silica. The method yields reproducible results and is amenable to the coating of large substrates and curved surfaces such as mirrors and lenses.

Effect of carrier properties on surface characteristics of sorbents modified with acetylacetonates Ni (II), Cu (II)

NASA Astrophysics Data System (ADS)

Faustova, Zhanna; Matveeva, Tatiana; Slizhov, Yuriy

2017-11-01

Sorbents based on Chromaton N-AW with layers of mesoporous silica gel modified with acetylacetonate nickel (II) and copper (II) were obtained. The porous structure of sorbents based on synthesized silica gel and industrial samples of Chromaton N, Silipore 075, Silochrom C-120 was studied. All studied samples are mesoporous. For sorbents based on commercially available Chromaton N, Silipore 075, and Silochrome 120, the mesopore dimensions vary in a wide range from 10 to 50 nm. For synthesized silica gel and chelate-containing sorbents, a narrower pore distribution is observed in the range of 5-15 nm, which indicates the uniformity of its surface. A comparative analysis of the effect of carrier properties on the acid-base properties of the surface of chelate-containing sorbents is carried out. The acid-base nature of the modifier is more pronounced in the case of synthesized silica gel by the sol-gel method.

Thermosensitive In Situ Gel Based on Solid Dispersion for Rectal Delivery of Ibuprofen.

PubMed

Liu, Yangdan; Wang, Xin; Liu, Youping; Di, Xin

2018-01-01

The objective of this study was to develop a thermosensitive in situ gel based on solid dispersions (SDs) for rectal delivery of ibuprofen (IBU). Thermosensitive (poloxamer 407) and mucoadhesive (hydroxypropylmethyl cellulose E5 and sodium alginate) polymers were used to prepare the in situ gel and the sol-gel transition temperature (T sol-gel ) and gel strength were optimized. The in vitro release performance and in vivo pharmacokinetic properties of the in situ gel after their rectal administration to rabbits were investigated. Compared with the solid suppository, the cumulative release of the IBU SDs loaded in situ gel was significantly increased. The in vivo pharmacokinetics indicated that in situ gel had a higher peak plasma concentration (C max ) and area under the curve (AUC (0-∞) ) in plasma than the solid suppositories. Histopathology results showed that the IBU in situ gel given at a dose of 15 mg/kg did not produce any irritation. In conclusion, this study suggested that the in situ gel could be an effective rectal formulation for IBU.

Peri-tumor administration of 5-fluorouracil sol-gel using a hollow microneedle for treatment of gastric cancer.

PubMed

Jung, Yoon Suk; Koo, Dong-Hoe; Yang, Jeong-Yoon; Lee, Hee-Young; Park, Jung-Hwan; Park, Jung Ho

2018-11-01

The aim of this study was to investigate the effectiveness of treating gastric cancer by injecting a pluronic F-127 sol-gel formulation of 5-fluorouracil (5-FU) into normal tissue surrounding the tumor using a hollow microneedle. The MTS tetrazolium assay was performed to assess the cytotoxicity of 5-FU after application to gastric cancer cells at different concentrations for 1, 5 and 10 h. Gastric cancer cells were inoculated subcutaneously into 30 male nude mice (CrjBALB/c-nu/nu mice, male); the inoculated mouse were divided into three groups. One group received no treatment, whereas the two other groups received free 5-FU gel (40 mg/kg) and 5-FU gel (40 mg/kg) for 4 days, respectively. Mean tumor volume, apoptotic index (TUNEL) and proliferative index (Ki 67) were evaluated in all groups. Cell viability was 77.3% when 1.22 g of free 5-FU was administered, whereas cell viability was 37.4% and 43.5% when 0.122 g of free 5-FU was administered per hour for 10 h and 0.244 g of free 5-FU was administered for 5 h (p < .01). The 5-FU sol-gel induced apoptosis and significantly inhibited cell proliferation compared to the free 5-FU (p < .01). In addition, xenografted tumor growth was significantly suppressed by administration of the 5-FU sol-gel formulation to inoculated mice (p < .01), and 71% (5/7) of xenografted tumors disappeared after 4 weeks. In conclusion, peri-tumor injection of a 5-FU sol-gel formulation into normal tissue surrounding the tumor mass using a hollow microneedle is an effective method for treating gastric cancer.

Brilliant molecular nanocrystals emerging from sol-gel thin films: towards a new generation of fluorescent biochips.

PubMed

Dubuisson, E; Monnier, V; Sanz-Menez, N; Boury, B; Usson, Y; Pansu, R B; Ibanez, A

2009-08-05

To develop highly sensitive biosensors, we made directly available to biological aqueous solutions organic nanocrystals previously grown in the pores of sol-gel films. Through the controlled dissolution of the sol-gel surface, we obtained emerging nanocrystals that remained strongly anchored to the sol-gel coating for good mechanical stability of the final sensing device. We demonstrated that in the presence of a solution of DNA functionalized with a molecular probe, the nanocrystal fluorescence is strongly quenched by Förster resonance energy transfer thus opening the way towards very sensitive fluorescent biosensors through biomolecules grafted onto fluorescent nanocrystals. Finally, this controlled dissolution, involving weak concentrated NaOH solution, is a generic process that can be used for the thinning of any kind of sol-gel layer.

Evaluation of sol-gel based magnetic 45S5 bioglass and bioglass-ceramics containing iron oxide.

PubMed

Shankhwar, Nisha; Srinivasan, A

2016-05-01

Multicomponent oxide powders with nominal compositions of (45-x)·SiO2·24.5CaO·24.5Na2O·6P2O5xFe2O3 (in wt.%) were prepared by a modified sol-gel procedure. X-ray diffraction (XRD) patterns and high resolution transmission electron microscope images of the sol-gel products show fully amorphous structure for Fe2O3 substitutions up to 2 wt.%. Sol-gel derived 43SiO2·24.5CaO·24.5Na2O·6P2O5·2Fe2O3 glass (or bioglass 45S5 with SiO2 substituted with 2 wt.% Fe2O3), exhibited magnetic behavior with a coercive field of 21 Oe, hysteresis loop area of 33.25 erg/g and saturation magnetization of 0.66 emu/g at an applied field of 15 kOe at room temperature. XRD pattern of this glass annealed at 850 °C for 1h revealed the formation of a glass-ceramic containing sodium calcium silicate and magnetite phases in nanocrystalline form. Temperature dependent magnetization and room temperature electron spin resonance data have been used to obtain information on the magnetic phase and distribution of iron ions in the sol-gel glass and glass-ceramic samples. Sol-gel derived glass and glass-ceramic exhibit in-vitro bioactivity by forming a hydroxyapatite surface layer under simulated physiological conditions and their bio-response is superior to their melt quenched bulk counterparts. This new form of magnetic bioglass and bioglass ceramics opens up new and more effective biomedical applications. Copyright © 2016 Elsevier B.V. All rights reserved.

Transparent Glass-Ceramics Produced by Sol-Gel: A Suitable Alternative for Photonic Materials.

PubMed

Gorni, Giulio; Velázquez, Jose J; Mosa, Jadra; Balda, Rolindes; Fernández, Joaquin; Durán, Alicia; Castro, Yolanda

2018-01-30

Transparent glass-ceramics have shown interesting optical properties for several photonic applications. In particular, compositions based on oxide glass matrices with fluoride crystals embedded inside, known as oxyfluoride glass-ceramics, have gained increasing interest in the last few decades. Melt-quenching is still the most used method to prepare these materials but sol-gel has been indicated as a suitable alternative. Many papers have been published since the end of the 1990s, when these materials were prepared by sol-gel for the first time, thus a review of the achievements obtained so far is necessary. In the first part of this paper, a review of transparent sol-gel glass-ceramics is made focusing mainly on oxyfluoride compositions. Many interesting optical results have been obtained but very little innovation of synthesis and processing is found with respect to pioneering papers published 20 years ago. In the second part we describe the improvements in synthesis and processing obtained by the authors during the last five years. The main achievements are the preparation of oxyfluoride glass-ceramics with a much higher fluoride crystal fraction, at least double that reported up to now, and the first synthesis of NaGdF₄ glass-ceramics. Moreover, a new SiO₂ precursor was introduced in the synthesis, allowing for a reduction in the treatment temperature and favoring hydroxyl group removal. Interesting optical properties demonstrated the incorporation of dopant ions in the fluoride crystals, thus obtaining crystal-like spectra along with higher efficiencies with respect to xerogels, and hence demonstrating that these materials are a suitable alternative for photonic applications.

Modified thermoresponsive Poloxamer 407 and chitosan sol-gels as potential sustained-release vaccine delivery systems.

PubMed

Kojarunchitt, Thunjiradasiree; Baldursdottir, Stefania; Dong, Yao-Da; Boyd, Ben J; Rades, Thomas; Hook, Sarah

2015-01-01

Thermoresponsive, particle-loaded, Poloxamer 407 (P407)-Pluronic-R® (25R4) or chitosan-methyl cellulose (MC) formulations were developed as single-dose, sustained release vaccines. The sol-gels, loaded either with a particulate vaccine (cubosomes) or soluble antigen (ovalbumin) and adjuvants (Quil A and monophosphoryl lipid A), were free-flowing liquids at room temperature and formed stable gels at physiological temperatures. Rheological results showed that both systems meet the criteria of being thermoresponsive gels. The P407-25R4 sol-gels did not significantly sustain the release of antigen in vivo while the chitosan-MC sol-gels sustained the release of antigen up to at least 14 days after administration. The chitosan-MC sol-gels stimulated both cellular and humoral responses. The inclusion of cubosomes in the sol-gels did not provide a definitive beneficial effect. Further analysis of the formulations with small-angle X-ray scattering (SAXS) revealed that while cubosomes were stable in chitosan-MC gels they were not stable in P407-25R4 formulations. The reason for the mixed response to cubosome-loaded vehicles requires more investigation, however it appears that the cubosomes did not facilitate synchronous vaccine release and may in fact retard release, reducing efficacy in some cases. From these results, chitosan-MC sol-gels show potential as sustained release vaccine delivery systems, as compared to the P407-25R4 system that had a limited ability to sustain antigen release. Copyright © 2014 Elsevier B.V. All rights reserved.

PREPARATION OF HIGH-DENSITY, COMPACTIBLE THORIUM OXIDE PARTICLES

DOEpatents

McCorkle, K.H.; Kleinsteuber, A.T.; Schilling, C.E.; Dean, O.C.

1962-05-22

A method is given for preparing millimeter-size, highdensity thorium oxide particles suitable for fabrication into nuclear reactor feel elements by means of vibratory compaction. A thorium oxide gel containing 3.7 to 7 weight per cent residual volatile nitrate and water is prepared by drying a thorium oxide sol. The gel is then slowly heated to a temperature of about 450DEC, and the resulting gel fragments are calcined. The starting sol is prepared by repeated dispersion of oxalate-source thorium oxide in a nitrate system or by dispersion of steam-denitrated thorium oxide in water. (AEC)

Near-infrared luminescence from Y2O3:Eu3+, Yb3+ prepared by sol-gel method.

PubMed

Xie, Ying; Xiao, Lin J; Yan, Feng Q; Chen, Yong J; Li, Wen Z; Geng, Xiu J

2014-06-01

Eu3+ and Yb3+ codoped Y2O3 phosphors were synthesized by the sol-gel method. The phosphors possess absorption in the region of 300-550 nm, exhibiting an intense NIR emission of Yb3+ around 1000 nm, which is suitable for matching the maximum spectral response of c-Si solar cells. The optimum composition of Eu3+ and Yb3+ codoped Y2O3 was (Y1.94Yb0.04Eu0.02)2O3. It is observed that two-step energy transfer occurs from the 5D2 level of Eu3+ situated around (466 nm) exciting two neighboring Yb3+ ions to the 2F5/2 level (1000 nm). The down-conversion material based on Eu(3+)- Yb3+ couple may have great potential applications in c-Si solar cells to enhance their photovoltaic conversion efficiency via spectral modification.

A proton-exchange membrane prepared by the radiation grafting of styrene and silica into polytetrafluoroethylene films

NASA Astrophysics Data System (ADS)

Yu, Hongyan; Shi, Jianheng; Zeng, Xinmiao; Bao, Mao; Zhao, Xinqing

2009-07-01

A polytetrafluoroethylene (PTFE) based organic-inorganic hybrid proton-exchange membrane was prepared from simultaneous radiation grafting of styrene (St) into porous PTFE membrane with the in situ sol-gel reaction of tetraethoxysilane (TEOS) followed by sulfonation in fuming sulfonic acid. The effect of radiation on the sol-gel reaction was studied. The results show that radiation promotes the sol-gel reaction with the help of St at room temperature. Incorporated silica gel helps to produce higher degree of grafting (DOG). SEM analysis was conducted to confirm that the inorganic silicon oxide was introduced to produce hybrid membrane in this work. The proton conductivity of membrane evaluated using electrochemical impedance spectroscopy is much higher (14.3×10 -2 S cm -1) than that of Nafion ® 117 at temperature of 80 °C with acceptable water uptake 51 wt%.

[pH sensors based on rubbery ormosils preparation and their spectrum studies].

PubMed

Chen, Xi; Dai, Yuan-jing; Li, Wei; Zhuang, Zhi-xia; Wang, Xiao-ru

2002-02-01

A new type of methyl substituted ormosils as a matrix for bromophenol blue (BPhB) and bromocresol green (BCG) is described. The new ormosils combine features of classical TEOS sol-gel material such as solvability in organic solvent and those of sol-gel glasses such as transparent and a porous structure, the ormosils also make a good mechanical stability. The influence of the conditions during the polymerisation process on the photochemical properties of BPhB and BCG has been studied. This sol-gel material was wed to immobilize pH-sensitive absorption dyes, bromothymol blue and bromocresol green, to prepare pH sensing films. The several aspects of the sensing films, including the leaching of the dye from gel, response time to different pH buffer solution, absorption spectra and the improvement of the immobilization of the dyes to filmo, were also discussed.

Synthesis of hybrid cellulose nanocomposite bonded with dopamine SiO2/TiO2 and its antimicrobial activity

NASA Astrophysics Data System (ADS)

Ramesh, Sivalingam; Kim, Gwang-Hoon; Kim, Jaehwan; Kim, Joo-Hyung

2015-04-01

Organic-inorganic hybrid material based cellulose was synthesized by the sol-gel approach. The explosion of activity in this area in the past decade has made tremendous progress in industry or academic both fundamental understanding of sol-gel process and applications of new functionalized hybrid materials. In this present research work, we focused on cellulose-dopamine functionalized SiO2/TiO2 hybrid nanocomposite by sol-gel process. The cellulose-dopamine hybrid nanocomposite was synthesized via γ-aminopropyltriethoxysilane (γ-APTES) coupling agent by in-situ sol-gel process. The chemical structure of cellulose-amine functionalized dopamine bonding to cellulose structure with covalent cross linking hybrids was confirmed by FTIR spectral analysis. The morphological analysis of cellulose-dopamine nanoSiO2/TiO2 hybrid nanocomposite materials was characterized by XRD, SEM and TEM. From this different analysis results indicate that the optical transparency, thermal stability, control morphology of cellulose-dopamine-SiO2/TiO2 hybrid nanocomposite. Furthermore cellulose-dopamine-SiO2/TiO2 hybrid nanocomposite was tested against pathogenic bacteria for antimicrobial activity.

Optical Constants of Crystallized TiO2 Coatings Prepared by Sol-Gel Process

PubMed Central

Wang, Xiaodong; Wu, Guangming; Zhou, Bin; Shen, Jun

2013-01-01

Titanium oxide coatings have been deposited by the sol-gel dip-coating method. Crystallization of titanium oxide coatings was then achieved through thermal annealing at temperatures above 400 °C. The structural properties and surface morphology of the crystallized coatings were studied by micro-Raman spectroscopy and atomic force microscopy, respectively. Characterization technique, based on least-square fitting to the measured reflectance and transmittance spectra, is used to determine the refractive indices of the crystallized TiO2 coatings. The stability of the synthesized sol was also investigated by dynamic light scattering particle size analyzer. The influence of the thermal annealing on the optical properties was then discussed. The increase in refractive index with high temperature thermal annealing process was observed, obtaining refractive index values from 1.98 to 2.57 at He-Ne laser wavelength of 633 nm. The Raman spectroscopy and atomic force microscopy studies indicate that the index variation is due to the changes in crystalline phase, density, and morphology during thermal annealing. PMID:28811410

Optical Constants of Crystallized TiO₂ Coatings Prepared by Sol-Gel Process.

PubMed

Wang, Xiaodong; Wu, Guangming; Zhou, Bin; Shen, Jun

2013-07-12

Titanium oxide coatings have been deposited by the sol-gel dip-coating method. Crystallization of titanium oxide coatings was then achieved through thermal annealing at temperatures above 400 °C. The structural properties and surface morphology of the crystallized coatings were studied by micro-Raman spectroscopy and atomic force microscopy, respectively. Characterization technique, based on least-square fitting to the measured reflectance and transmittance spectra, is used to determine the refractive indices of the crystallized TiO₂ coatings. The stability of the synthesized sol was also investigated by dynamic light scattering particle size analyzer. The influence of the thermal annealing on the optical properties was then discussed. The increase in refractive index with high temperature thermal annealing process was observed, obtaining refractive index values from 1.98 to 2.57 at He-Ne laser wavelength of 633 nm. The Raman spectroscopy and atomic force microscopy studies indicate that the index variation is due to the changes in crystalline phase, density, and morphology during thermal annealing.

Electrospun Polyhydroxybutyrate/Poly(ε-caprolactone)/58S Sol-Gel Bioactive Glass Hybrid Scaffolds with Highly Improved Osteogenic Potential for Bone Tissue Engineering.

PubMed

Ding, Yaping; Li, Wei; Müller, Teresa; Schubert, Dirk W; Boccaccini, Aldo R; Yao, Qingqing; Roether, Judith A

2016-07-13

Electrospinning of biopolymer and inorganic substances is one of the efficient ways to combine various advantageous properties in one single fibrous structure with potential for tissue engineering applications. In the present study, to integrate the high stiffness of polyhydroxybutyrate (PHB), the flexibility of poly(ε-caprolactone) (PCL) and the bioactivity of 58S bioactive glass, PHB/PCL/58S sol-gel bioactive glass hybrid scaffolds were fabricated using combined electrospinning and sol-gel method. Physical features such as fiber diameter distribution, mechanical strength and Young's modulus were characterized thoroughly. FTIR analysis demonstrated the successful incorporation of 58S bioactive glass into the blend polymers, which greatly improved the hydrophilicity of PHB/PCL fibermats. The primary biological response of MG-63 osteoblast-like cells on the prepared fibrous scaffolds was evaluated, proving that the 58S glass sol containing hybrid scaffold were not only favorable to MG-63 cell adhesion but also slightly enhanced cell viability and significantly increased alkaline phosphate activity .

Study of the sodium phenytoin effect on the formation of sol-gel SiO 2 nanotubes by TEM

NASA Astrophysics Data System (ADS)

López, T.; Asomoza, M.; Picquart, M.; Castillo-Ocampo, P.; Manjarrez, J.; Vázquez, A.; Ascencio, J. A.

2005-04-01

Microencapsulation is a versatile technology that allows controlling the release of different active molecules. Recently the sol-gel process has emerged like a promising method to immobilization and stabilization of biologically active compounds like enzymes, antigens, microorganisms and drugs. Porous silica and titanium dioxide materials made by low temperature sol-gel processes are promising host matrixes for encapsulation of biological molecules. The preparation of a low-temperature silica sol followed by gelation to neutral pH with water for injection containing the antiepileptic drug is reported here. The structure is very important so the analysis of the new developed material is also reported. Particularly interesting is the presence of nanotubes and microtubes, produced in the inorganic matrix in the presence of the sodium phenytoin. The use of transmission electron microscopy and quantum mechanics molecular simulation allows determining a micelle-like effect during the synthesis of these materials, which controls the size, structure and stability of them.

Sol gel-derived hydroxyapatite films over porous calcium polyphosphate substrates for improved tissue engineering of osteochondral-like constructs.

PubMed

Lee, Whitaik David; Gawri, Rahul; Pilliar, Robert M; Stanford, William L; Kandel, Rita A

2017-10-15

Integration of in vitro-formed cartilage on a suitable substrate to form tissue-engineered implants for osteochondral defect repair is a considerable challenge. In healthy cartilage, a zone of calcified cartilage (ZCC) acts as an intermediary for mechanical force transfer from soft to hard tissue, as well as an effective interlocking structure to better resist interfacial shear forces. We have developed biphasic constructs that consist of scaffold-free cartilage tissue grown in vitro on, and interdigitated with, porous calcium polyphosphate (CPP) substrates. However, as CPP degrades, it releases inorganic polyphosphates (polyP) that can inhibit local mineralization, thereby preventing the formation of a ZCC at the interface. Thus, we hypothesize that coating CPP substrate with a layer of hydroxyapatite (HA) might prevent or limit this polyP release. To investigate this we tested both inorganic or organic sol-gel processing methods, asa barrier coating on CPP substrate to inhibit polyP release. Both types of coating supported the formation of ZCC in direct contact with the substrate, however the ZCC appeared more continuous in the tissue formed on the organic HA sol gel coated CPP. Tissues formed on coated substrates accumulated comparable quantities of extracellular matrix and mineral, but tissues formed on organic sol-gel (OSG)-coated substrates accumulated less polyP than tissues formed on inorganic sol-gel (ISG)-coated substrates. Constructs formed with OSG-coated CPP substrates had greater interfacial shear strength than those formed with ISG-coated and non-coated substrates. These results suggest that the OSG coating method can modify the location and distribution of ZCC and can be used to improve the mechanical integrity of tissue-engineered constructs formed on porous CPP substrates. Articular cartilage interfaces with bone through a zone of calcified cartilage. This study describes a method to generate an "osteochondral-like" implant that mimics this organization using isolated deep zone cartilage cells and a sol-gel hydroxyapatite coated bone substitute material composed of calcium polyphosphate (CPP). Developing a layer of calcified cartilage at the interface should contribute to enhancing the success of this "osteochondral-like" construct following implantation to repair cartilage defects. Copyright © 2017 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.

Uniform thin films of CdSe and CdSe(ZnS) core(shell) quantum dots by sol-gel assembly: enabling photoelectrochemical characterization and electronic applications.

PubMed

Korala, Lasantha; Wang, Zhijie; Liu, Yi; Maldonado, Stephen; Brock, Stephanie L

2013-02-26

Optoelectronic properties of quantum dot (QD) films are limited by (1) poor interfacial chemistry and (2) nonradiative recombination due to surface traps. To address these performance issues, sol-gel methods are applied to fabricate thin films of CdSe and core(shell) CdSe(ZnS) QDs. High-angle annular dark-field scanning transmission electron microscopy (HAADF-STEM) imaging with chemical analysis confirms that the surface of the QDs in the sol-gel thin films are chalcogen-rich, consistent with an oxidative-induced gelation mechanism in which connectivity is achieved by formation of dichalcogenide covalent linkages between particles. The ligand removal and assembly process is probed by thermogravimetric, spectroscopic, and microscopic studies. Further enhancement of interparticle coupling via mild thermal annealing, which removes residual ligands and reinforces QD connectivity, results in QD sol-gel thin films with superior charge transport properties, as shown by a dramatic enhancement of electrochemical photocurrent under white light illumination relative to thin films composed of ligand-capped QDs. A more than 2-fold enhancement in photocurrent, and a further increase in photovoltage can be achieved by passivation of surface defects via overcoating with a thin ZnS shell. The ability to tune interfacial and surface characteristics for the optimization of photophysical properties suggests that the sol-gel approach may enable formation of QD thin films suitable for a range of optoelectronic applications.

Uniform Thin Films of CdSe and CdSe(ZnS) Core(shell) Quantum Dots by Sol-Gel Assembly: Enabling Photoelectrochemical Characterization and Electronic Applications

PubMed Central

Korala, Lasantha; Wang, Zhijie; Liu, Yi; Maldonado, Stephen; Brock, Stephanie L.

2013-01-01

Optoelectronic properties of quantum dot (QD) films are limited by (1) poor interfacial chemistry and (2) non-radiative recombination due to surface traps. To address these performance issues, sol-gel methods are applied to fabricate thin films of CdSe and core(shell) CdSe(ZnS) QDs. High-angle annular dark-field scanning transmission electron microscopy (HAADF-STEM) imaging with chemical analysis confirms that the surface of the QDs in the sol-gel thin films are chalcogen-rich, consistent with an oxidative-induced gelation mechanism in which connectivity is achieved by formation of dichalcogenide covalent linkages between particles. The ligand removal and assembly process is probed by thermogravimetric, spectroscopic and microscopic studies. Further enhancement of inter-particle coupling via mild thermal annealing, which removes residual ligands and reinforces QD connectivity, results in QD sol-gel thin films with superior charge transport properties, as shown by a dramatic enhancement of electrochemical photocurrent under white light illumination relative to thin films composed of ligand-capped QDs. A more than 2-fold enhancement in photocurrent, and a further increase in photovoltage can be achieved by passivation of surface defects via overcoating with a thin ZnS shell. The ability to tune interfacial and surface characteristics for the optimization of photophysical properties suggests that the sol-gel approach may enable formation of QD thin films suitable for a range of optoelectronic applications. PMID:23350924

Organization versus frustration: low temperature transitions in a gelatine-based gel

NASA Astrophysics Data System (ADS)

Philipp, M.; Müller, U.; Sanctuary, R.; Baller, J.; Krüger, J. K.

2008-09-01

A commercial physical gel composed of gelatine, water and glycerol shows a sol-gel transition which has been resolved by optical rotation measurements by step-wise heating the gel. This transition is not observable in the longitudinal acoustic mode measured at hypersonic frequencies with Brillouin spectroscopy. Depending on the thermal treatment of the investigated material during the sol-gel transition and within the gel state, Brillouin spectroscopy reflects tremendously different hypersonic dynamics. These distinct dynamics are responsible for the formation of different glassy states at low temperatures including that of a glass-ceramic. The large variety of super-cooled and glassy states is attributed to distinct distributions of the gel's constituents within the samples. Surprisingly, the same gel state can be produced either by annealing the gel over months or by the non-equilibrium effect of thermo-diffusion (Soret effect) in the course of some minutes.

Mayenite Synthesized Using the Citrate Sol-Gel Method

DOE Office of Scientific and Technical Information (OSTI.GOV)

Ude, Sabina N; Rawn, Claudia J; Meisner, Roberta A

2014-01-01

A citrate sol-gel method has been used to synthesize mayenite (Ca12Al14O33). X-ray powder diffraction data show that the samples synthesized using the citrate sol-gel method contained CaAl2O4 and CaCO3 along with mayenite when fired ex-situ in air at 800 C but were single phase when fired at 900 C and above. Using high temperature x-ray diffraction, data collected in-situ in air at temperatures of 600 C and below showed only amorphous content; however, data collected at higher temperatures indicated the first phase to crystallize is CaCO3. High temperature x-ray diffraction data collected in 4% H2/96% N2 does not show themore » presence of CaCO3, and Ca12Al14O33 starts to form around 850 C. In comparison, x-ray powder diffraction data collected ex-situ on samples synthesized using traditional solid-state synthesis shows that single phase was not reached until samples were fired at 1350 C. DTA/TGA data collected either in a nitrogen environment or air on samples synthesized using the citrate gel method suggest the complete decomposition of metastable phases and the formation of mayenite at 900 C, although the phase evolution is very different depending on the environment. Brunauer-Emmett-Teller (BET) measurements showed a slightly higher surface area of 7.4 0.1 m2/g in the citrate gel synthesized samples compared to solid-state synthesized sample with a surface area of 1.61 0.02 m2/g. SEM images show a larger particle size for samples synthesized using the solid-state method compared to those synthesized using the citrate gel method.« less

Architectural optimization of an epoxy-based hybrid sol-gel coating for the corrosion protection of a cast Elektron21 magnesium alloy

NASA Astrophysics Data System (ADS)

Murillo-Gutiérrez, N. V.; Ansart, F.; Bonino, J.-P.; Kunst, S. R.; Malfatti, C. F.

2014-08-01

An epoxy-based hybrid sol-gel coating was prepared in various architectural configurations has been studied for the corrosion protection of a cast Elektron21 magnesium alloy. The creation of a single layer of this coating presents defects consisting of macro-pores and protuberances, which opens access for corrosive species to reach the metallic substrate. These defects are suspected to result from the high reactivity of the substrate, as well as to the irregular topography of the substrate disrupted by the microstructure of the own magnesium alloy. Hence, a sol-gel coating in bilayer architecture is proposed, where the first layer would “inert” the surface of the magnesium substrate, and the second layer would cover the defects of the first layer and also thickening the coating. The morphological characteristics of the sol-gel coatings were analyzed by scanning electron microscopy (SEM), and their corrosion behavior was evaluated by OCP (open circuit potential) monitoring and electrochemical impedance spectroscopy (EIS) in chloride media. It is shown that both the architectural arrangement and the individual thickness of the first and second layers have an important influence on the anticorrosion performances of the protective system, just as much as its global thickness.

Chitosan-based thermosensitive hydrogel as a promising ocular drug delivery system: preparation, characterization, and in vivo evaluation.

PubMed

Chen, Xingwei; Li, Xinru; Zhou, Yanxia; Wang, Xiaoning; Zhang, Yanhui; Fan, Yating; Huang, Yanqing; Liu, Yan

2012-11-01

The purpose of this study was to evaluate the feasibility of in situ thermosensitive hydrogel based on chitosan in combination with disodium α-d-Glucose 1-phosphate (DGP) for ocular drug delivery system. Aqueous solution of chitosan/DGP underwent sol-gel transition as temperature increased which was flowing sol at room temperature and then turned into non-flowing hydrogel at physiological temperature. The properties of gels were characterized regarding gelation time, gelation temperature, and morphology. The sol-to-gel phase transition behaviors were affected by the concentrations of chitosan, DGP and the model drug levocetirizine dihydrochloride (LD). The developed hydrogel presented a characteristic of a rapid release at the initial period followed by a sustained release and remarkably enhanced the cornea penetration of LD. The results of ocular irritation demonstrated the excellent ocular tolerance of the hydrogel. The ocular residence time for the hydrogel was significantly prolonged compared with eye drops. The drug-loaded hydrogel produced more effective anti-allergic conjunctivitis effects compared with LD aqueous solution. These results showed that the chitosan/DGP thermosensitive hydrogel could be used as an ideal ocular drug delivery system in terms of the suitable sol-gel transition temperature, mild pH environment in the hydrogel as well as the organic solvent free.

Microstructural changes in NiFe2O4 ceramics prepared with powders derived from different fuels in sol-gel auto-combustion technique

NASA Astrophysics Data System (ADS)

Chauhan, Lalita; Bokolia, Renuka; Sreenivas, K.

2016-05-01

Structural properties of Nickel ferrite (NiFe2O4) ceramics prepared from powders derived from sol gel auto-combustion method using different fuels (citric acid, glycine and Dl-alanine) are compared. Changes in the structural properties at different sintering temperatures are investigated. X-ray diffraction (XRD) confirms the formation of single phase material with cubic structure. Ceramics prepared using the different powders obtained from different fuels show that that there are no significant changes in lattice parameters. However increasing sintering temperatures show significant improvement in density and grain size. The DL-alanine fuel is found to be the most effective fuel for producing NIFe2O4 powders by the sol-gel auto combustion method and yields highly crystalline powders in the as-burnt stage itself at a low temperature (80 °C). Subsequent use of the powders in ceramic manufacturing produces dense NiFe2O4 ceramics with a uniform microstructure and a large grain size.

Two-Step Sintering Behavior of Sol-Gel Derived Dense and Submicron-Grained YIG Ceramics

NASA Astrophysics Data System (ADS)

Chen, Ruoyuan; Zhou, Jijun; Zheng, Liang; Zheng, Hui; Zheng, Peng; Ying, Zhihua; Deng, Jiangxia

2018-04-01

In this work, dense and submicron-grain yttrium iron garnet (YIG, Y3Fe5O12) ceramics were fabricated by a two-step sintering (TSS) method using nano-size YIG powder prepared by a citrate sol-gel method. The densification, microstructure, magnetic properties and ferromagnetic resonance (FMR) linewidth of the ceramics were investigated. The sample prepared at 1300°C in T 1, 1225°C in T 2 and 18 h holding time has a density higher than 98% of the theoretical value and exhibits a homogeneous microstructure with fine grain size (0.975 μm). In addition, the saturation magnetization ( M S) of this sample reaches 27.18 emu/g. High density and small grain size can also achieve small FMR linewidth. Consequently, these results show that the sol-gel process combined with the TSS process can effectively suppress grain-boundary migration while maintaining active grain-boundary diffusion to obtain dense and fine-grained YIG ceramics with appropriate magnetic properties.

Biocatalysis with Sol-Gel Encapsulated Acid Phosphatase

ERIC Educational Resources Information Center

Kulkarni, Suhasini; Tran, Vu; Ho, Maggie K.-M.; Phan, Chieu; Chin, Elizabeth; Wemmer, Zeke; Sommerhalter, Monika

2010-01-01

This experiment was performed in an upper-level undergraduate biochemistry laboratory course. Students learned how to immobilize an enzyme in a sol-gel matrix and how to perform and evaluate enzyme-activity measurements. The enzyme acid phosphatase (APase) from wheat germ was encapsulated in sol-gel beads that were prepared from the precursor…

Thermal stability and degradation kinetics of kenaf/sol-gel silica hybrid

NASA Astrophysics Data System (ADS)

Yusof, F. A. M.; Hashim, A. S.; Tajudin, Z.

2017-12-01

Thermal stability and degradation kinetics of kenaf/sol-gel silica hybrid materials was investigated by thermogravimetric analysis (TGA). Model-free iso-conversion Flynn-Wall-Ozawa (FWO) and Coats-Redfern-modified (CRm) were chosen to evaluate the activation energy of the kenaf (KF) and kenaf/sol-gel silica (KFS) at heating rates (β) of 10, 20, 30 and 40 °C/min. The results shows that an apparent activation energy was increased for the kenaf/sol-gel silica hybrid (211.59 kJ/mol for FWO and 191.55 kJ/mol for CRm) as compared to kenaf fiber (202.84 kJ/mol for FWO and 186.20 kJ/mol for CRm). Other parameters such as integral procedure decomposition temperature (IPDT), final residual weight (Rf), temperature of maximum degradation rate (Tmax) and residual at maximum temperature (RTmax) were obtained from TGA curves, additionally confirmed the thermal stability of the kenaf/sol-gel silica hybrid. These activation energy values and other findings developed the simplified approach in order to understand the thermal stability and degradation kinetics behavior of kenaf/sol-gel silica hybrid materials.

Passive and active sol-gel materials and devices

NASA Astrophysics Data System (ADS)

Andrews, Mark P.; Najafi, S. Iraj

1997-07-01

This paper examines sol-gel materials for photonics in terms of partnerships with other material contenders for processing optical devices. The discussion in four sections identifies semiconductors, amorphous and crystalline inorganic dielectrics, and amorphous and crystalline organic dielectrics as strategic agents in the rapidly evolving area of materials and devices for data communications and telecommunications. With Zyss, we trace the hierarchical lineage that connects molecular hybridization (chemical functionality), through supramolecular hybridization (collective properties and responses), to functional hybridization (device and system level constructs). These three concepts thread their way through discussions of the roles sol-gel glasses might be anticipated to assume in a photonics marketplace. We assign a special place to glass integrated optics and show how high temperature consolidated sol-gel derived glasses fit into competitive glass fabrication technologies. Low temperature hybrid sol-gel glasses that combine attractive features of organic polymers and inorganic glasses are considered by drawing on examples of our own new processes for fabricating couplers, power splitters, waveguides and gratings by combining chemical synthesis and sol-gel processing with simple photomask techniques.

Preparation and characterization of strontium-fluorapatite nanopowders by sol-gel method

NASA Astrophysics Data System (ADS)

Kamaei, Maryam; Fathi, Mohammad Hossein

2018-01-01

Biomaterials based on calcium orthophosphate are especially attractive for use in medicine, for bone and teeth implants due to their biological properties, such as biocompatibility and bioactivity. Among them, hydroxyapatite (HAP; Ca10(PO4)6(OH)2) is used particularly because of its similarities to the inorganic component of bone. Hydroxyapatite has been widely used for biomedical applications. Despite desirable properties such as bioactivity, biocompatibility, solubility and adsorption, synthetic HA is limited in application due to poor thermostability and poor mechanical properties. Properties of HA can be tailored over a wide range by incorporating different ions into HA lattice. Use of the sol-gel technique is technically simple, cost effective and beneficial for fabrication biomaterials. This research aimed to prepare and characterize Sr-doped FA nanopowders (Sr-FA). Sr-FA with different Sr contents was prepared by sol-gel method. The designated degree of substitution of Ca by Sr in the mixture was determined by the x value in the general formula of (Ca10-x Srx(PO4)6F2), where x=0,0.5,1. X-ray diffraction (XRD) and Fourier transform infrared spectroscopy (FTIR) techniques were utilized to characterize the obtained nano powders. Results showed that Sr ions entered into the fluorapatite lattice and occupied Ca sites. The incorporation of Sr ions into the fluorapatite resulted in the increase of the lattice parameters.

Planar waveguide sensor of ammonia

NASA Astrophysics Data System (ADS)

Rogoziński, Roman; Tyszkiewicz, Cuma; Karasiński, Paweł; Izydorczyk, Weronika

2015-12-01

The paper presents the concept of forming ammonia sensor based on a planar waveguide structure. It is an amplitude sensor produced on the basis of the multimode waveguide. The technological base for this kind of structure is the ion exchange method and the sol-gel method. The planar multimode waveguide of channel type is produced in glass substrate (soda-lime glass of Menzel-Glaser company) by the selective Ag+↔Na+ ion exchange. On the surface of the glass substrate a porous (~40%) silica layer is produced by the sol-gel method. This layer is sensitized to the presence of ammonia in the surrounding atmosphere by impregnation with Bromocresol Purple (BCP) dye. Therefore it constitutes a sensor layer. Spectrophotometric tests carried out showed about 50% reduction of cross-transmission changes of such sensor layer for a wave λ=593 nm caused by the presence of 25% ammonia water vapor in its ambience. The radiation source used in this type of sensor structure is a light emitting diode LED. The gradient channel waveguide is designed for frontal connection (optical glue) with a standard multimode telecommunications waveguide 62.5/125μm.

A sol-gel based solid phase microextraction fiber for the analysis of aliphatic alcohols in apple juices.

PubMed

Farhadi, Khalil; Maleki, Ramin; Tahmasebi, Raheleh

2010-01-01

A new fiber based on titania-chitin sol-gel coated on a silver wire for the headspace solid phase microextraction of aliphatic alcohols from apple juice samples was developed. The influences of fiber coating composition and microextraction conditions (extraction temperature, extraction time, and ionic strength of the sample matrix) on the fiber performance were investigated. Also, the influence of temperature and time on desorption of analytes from fiber were studied. Under the optimized conditions, a porous fiber with a high extraction capacity and good thermal stability (up to 250 degrees C) was obtained. The proposed headspace solid-phase microextraction-GC method was successfully used for the analysis of aliphatic alcohols in apple juice and concentrate samples. The recovery values were from 92.8 to 98.6%. The RSD (n=5) for all analytes were below 7.8%.

Combining inkjet printing and sol-gel chemistry for making pH-sensitive surfaces.

PubMed

Orsi, Gianni; De Maria, Carmelo; Montemurro, Francesca; Chauhan, Veeren M; Aylott, Jonathan W; Vozzi, Giovanni

2015-01-01

Today biomedical sciences are experiencing the importance of imaging biological parameters with luminescence methods. Studying 2D pH distribution with those methods allows building knowledge about complex cellular processes. Immobilizing pH sensitive nanoparticles inside hydrogel matrixes, in order to guarantee a proper SNR, could easily make stable and biocompatible 2D sensors. Inkjet printing is also well known as tool for printing images onto porous surfaces. Recently it has been used as a free-form fabrication method for building three-dimensional parts, and now is being explored as a way of printing electrical and optical devices. Inkjet printing was used either as a rapid prototyping method for custom biosensors. Sol-gel method is naturally bound with inkjet, because the picoliter-sized ink droplets evaporate quickly, thus allowing quick sol-gel transitions on the printed surface. In this work will be shown how to merge those technologies, in order to make a nanoparticles doped printable hydrogel, which could be used for making 2D/3D smart scaffolds able to monitor cell activities. An automated image analysis system was developed in order to quickly have the pH measurements from pH nanosensors fluorescence images.

Effect of SiN x diffusion barrier thickness on the structural properties and photocatalytic activity of TiO2 films obtained by sol-gel dip coating and reactive magnetron sputtering.

PubMed

Ghazzal, Mohamed Nawfal; Aubry, Eric; Chaoui, Nouari; Robert, Didier

2015-01-01

We investigate the effect of the thickness of the silicon nitride (SiN x ) diffusion barrier on the structural and photocatalytic efficiency of TiO2 films obtained with different processes. We show that the structural and photocatalytic efficiency of TiO2 films produced using soft chemistry (sol-gel) and physical methods (reactive sputtering) are affected differentially by the intercalating SiN x diffusion barrier. Increasing the thickness of the SiN x diffusion barrier induced a gradual decrease of the crystallite size of TiO2 films obtained by the sol-gel process. However, TiO2 obtained using the reactive sputtering method showed no dependence on the thickness of the SiN x barrier diffusion. The SiN x barrier diffusion showed a beneficial effect on the photocatalytic efficiency of TiO2 films regardless of the synthesis method used. The proposed mechanism leading to the improvement in the photocatalytic efficiency of the TiO2 films obtained by each process was discussed.

Sol-Gel Derived Hafnia Coatings

NASA Technical Reports Server (NTRS)

Feldman, Jay D.; Stackpoole, Mairead; Blum, Yigal; Sacks, Michael; Ellerby, Don; Johnson, Sylvia M.; Venkatapathy, Ethiras (Technical Monitor)

2002-01-01

Sol-gel derived hafnia coatings are being developed to provide an oxidation protection layer on ultra-high temperature ceramics for potential use in turbine engines (ultra-efficient engine technology being developed by NASA). Coatings using hafnia sol hafnia filler particles will be discussed along with sol synthesis and characterization.

Preparation of titanium dioxide films by sol-gel route for gas sensors

NASA Astrophysics Data System (ADS)

Schiopu, Vasilica; Matei, Alina; Cernica, Ileana; Podaru, Cecilia

2009-01-01

Semiconductor oxides such as SnO2, TiO2, WO3, ZnO2 etc. have been shown to be useful as gas sensor materials for monitoring various pollutant gases like H2S, NOx, NH3 etc. In this work, we would like to present the preparation of titanium dioxide films for gas sensor application, via the sol-gel technique. The coating solution was prepared by using titanium isopropoxide precursor, which was hydrolyzed with distilled water under the catalytic effect of different acids (HNO3, HCl or CH3COOH). Titanium dioxide films have been deposited using spin coating method and then synthesized at different temperatures. Fourier transform infrared spectroscopy observation has been used to analyze the sol-gel process. The morphology and the structure of the thin films were analyzed.

Photoluminescence from trivalent-cerium-doped silica glass prepared by sol-gel method with aluminum co-dopant

NASA Astrophysics Data System (ADS)

Tokumitsu, Seika; Murakami, Yukon; Oda, Hisaya; Kawabe, Yutaka

2018-01-01

Trivalent cerium is an important luminescent center giving light emission in short wavelength region depending on host materials. Sol-gel formed silica glass is an ideal matrix due to its high transparency, robustness, and low-temperature processability, but the emission from cerium in silica matrix is often mixed up with that from defects in the matrix, making it difficult to obtain well-determined characteristics. Bright emission from Ce ions peaking at about 400 nm was observed in sol-gel silica glasses synthesized with aluminum co-dopant. From luminescence decay time, the origin was confirmed to be d-f transition in trivalent Ce. From dependence of emission characteristics and UV absorbance on aluminum concentration, it was found that the co-dopant plays an important role to convert the optically inactive tetravalent ions to emissive trivalent state.

A fluorescence study of liposomes entrapped in sol-gel materials

DOE Office of Scientific and Technical Information (OSTI.GOV)

Yamanaka, S.A.; Singh, S.; Sasaki, D.Y.

1997-12-31

Liposomes of phosphatidylcholine lipids were successfully entrapped in silicates using the sol-gel method with complete retention of the molecular aggregates over long periods in aqueous solution. Fluorescent studies of the small unilamellar vesicles of 5% pyrene labeled lipid PSIDA with DSPC remobilized in the gel found significant lipid reorganization upon aging in aqueous solutions. Monitoring of pyrene excimer (470 nm) to monomer (375 nm) ratios in the bilayer reveals that the silicate matrix tends to disperse PSIDA lipid aggregates from that observed in free solution. On an interesting note, the liposomes in the gel at pH 7.5. The PSIDA/DSPC liposomes,more » sensitive to heavy metal ions in free solution, maintain similar sensitivity in the gel yet the sensor material can not be recycled.« less

Layer-by-Layer Self-Assembling Gold Nanorods and Glucose Oxidase onto Carbon Nanotubes Functionalized Sol-Gel Matrix for an Amperometric Glucose Biosensor

PubMed Central

Wu, Baoyan; Hou, Shihua; Miao, Zhiying; Zhang, Cong; Ji, Yanhong

2015-01-01

A novel amperometric glucose biosensor was fabricated by layer-by-layer self-assembly of gold nanorods (AuNRs) and glucose oxidase (GOD) onto single-walled carbon nanotubes (SWCNTs)-functionalized three-dimensional sol-gel matrix. A thiolated aqueous silica sol containing SWCNTs was first assembled on the surface of a cleaned Au electrode, and then the alternate self-assembly of AuNRs and GOD were repeated to assemble multilayer films of AuNRs-GOD onto SWCNTs-functionalized silica gel for optimizing the biosensor. Among the resulting glucose biosensors, the four layers of AuNRs-GOD-modified electrode showed the best performance. The sol-SWCNTs-(AuNRs-GOD)4/Au biosensor exhibited a good linear range of 0.01–8 mM glucose, high sensitivity of 1.08 μA/mM, and fast amperometric response within 4 s. The good performance of the proposed glucose biosensor could be mainly attributed to the advantages of the three-dimensional sol-gel matrix and stereo self-assembly films, and the natural features of one-dimensional nanostructure SWCNTs and AuNRs. This study may provide a new facile way to fabricate the enzyme-based biosensor with high performance. PMID:28347080

Preparation of fullerene/glass composites

DOEpatents

Mattes, Benjamin R.; McBranch, Duncan W.; Robinson, Jeanne M.; Koskelo, Aaron C.; Love, Steven P.

1995-01-01

Synthesis of fullerene/glass composites. A direct method for preparing solid solutions of C.sub.60 in silicon dioxide (SiO.sub.2) glass matrices by means of sol-gel chemistry is described. In order to produce highly concentrated fullerene-sol-gel-composites it is necessary to increase the solubility of these "guests" in a delivery solvent which is compatible with the starter sol (receiving solvent). Sonication results in aggregate disruption by treatment with high frequency sound waves, thereby accelerating the rate of hydrolysis of the alkoxide precursor, and the solution process for the C.sub.60. Depending upon the preparative procedure, C.sub.60 dispersed within the glass matrix as microcrystalline domains, or dispersed as true molecular solutions of C.sub.60 in a solid glass matrix, is generated by the present method.

Preparation of fullerene/glass composites

DOEpatents

Mattes, B.R.; McBranch, D.W.; Robinson, J.M.; Koskelo, A.C.; Love, S.P.

1995-05-30

Synthesis of fullerene/glass composites is described. A direct method for preparing solid solutions of C{sub 60} in silicon dioxide (SiO{sub 2}) glass matrices by means of sol-gel chemistry is described. In order to produce highly concentrated fullerene-sol-gel-composites it is necessary to increase the solubility of these ``guests`` in a delivery solvent which is compatible with the starter sol (receiving solvent). Sonication results in aggregate disruption by treatment with high frequency sound waves, thereby accelerating the rate of hydrolysis of the alkoxide precursor, and the solution process for the C{sub 60}. Depending upon the preparative procedure, C{sub 60} dispersed within the glass matrix as microcrystalline domains, or dispersed as true molecular solutions of C{sub 60} in a solid glass matrix, is generated by the present method.

Silicon-based microfabricated tin oxide gas sensor incorporating use of Hall effect measurement

NASA Astrophysics Data System (ADS)

Hammond, Joseph Wilson

2000-10-01

Characterization of a microfabricated sol-gel derived nano-particle tin oxide thin film on a silicon substrate, through simultaneous measurement of conductivity, Hall mobility and electron density, had not been accomplished before this study. Conductivity is a function of carrier density and Hall mobility. Therefore, a full understanding of the sensing mechanism of tin oxide requires knowledge of the sensor conductivity, electron density and Hall mobility. A tin oxide thin film (1100A thick), derived by the sol-gel method, was deposited on a Si/SiO2 substrate by means of spin coating method. The sol-gel method produces films of porous interconnected nano-sized particles and is relatively inexpensive and easy to produce compared to existing methods of tin oxide thin film deposition. A goal of this study was to determine the compatibility of sol-gel derived tin oxide thin films with silicon based microfabrication procedures. It was determined that conductivity sensitivity is strongly dependant on electron density level and shows very weak dependence on Hall mobility. Lack of Hall mobility sensitivity to H2 concentration suggests that conduction is grain control limited. In this regime, in which the grain size (D) is less than twice the characteristic Debye length (LD), a change in reducing gas concentration results in a nearly simultaneous change in carrier density throughout the entire grain, while the Hall mobility remains unchanged. The sensor calcined at 500°C and operated at 250°C showed maximum conductivity sensitivity to H2 in air. The sensor exhibited a high conductivity sensitivity of 10.6 to 100ppm H2 in air with response time of (˜1) minute and recovery time of (˜4) minutes. Images of the thin film surface, obtained by SEM, were used to study the effects of calcination temperature and operating conditions on the tin oxide structure. Sensitivity decreased as average grain size increased from 7.7nm to 14.7nm, with increasing calcination temperature from 500°C to 800°C. The sensors displayed slight drift in long term baseline stability and good long term sensitivity stability (14 days). Long term operation (30 days) at elevated temperatures had no noticeable effect on the thin film structure.

Method for producing nanostructured metal-oxides

DOEpatents

Tillotson, Thomas M.; Simpson, Randall L.; Hrubesh, Lawrence W.; Gash, Alexander

2006-01-17

A synthetic route for producing nanostructure metal-oxide-based materials using sol-gel processing. This procedure employs the use of stable and inexpensive hydrated-metal inorganic salts and environmentally friendly solvents such as water and ethanol. The synthesis involves the dissolution of the metal salt in a solvent followed by the addition of a proton scavenger, which induces gel formation in a timely manner. Both critical point (supercritical extraction) and atmospheric (low temperature evaporation) drying may be employed to produce monolithic aerogels and xerogels, respectively. Using this method synthesis of metal-oxide nanostructured materials have been carried out using inorganic salts, such as of Fe.sup.3+, Cr.sup.3+, Al.sup.3+, Ga.sup.3+, In.sup.3+, Hf.sup.4+, Sn.sup.4+, Zr.sup.4+, Nb.sup.5+, W.sup.6+, Pr.sup.3+, Er.sup.3+, Nd.sup.3+, Ce.sup.3+, U.sup.3+ and Y.sup.3+. The process is general and nanostructured metal-oxides from the following elements of the periodic table can be made: Groups 2 through 13, part of Group 14 (germanium, tin, lead), part of Group 15 (antimony, bismuth), part of Group 16 (polonium), and the lanthanides and actinides. The sol-gel processing allows for the addition of insoluble materials (e.g., metals or polymers) to the viscous sol, just before gelation, to produce a uniformly distributed nanocomposites upon gelation. As an example, energetic nanocomposites of Fe.sub.xO.sub.y gel with distributed Al metal are readily made. The compositions are stable, safe, and can be readily ignited to thermitic reaction.

Direct nanopatterning of 100 nm metal oxide periodic structures by Deep-UV immersion lithography.

PubMed

Stehlin, Fabrice; Bourgin, Yannick; Spangenberg, Arnaud; Jourlin, Yves; Parriaux, Olivier; Reynaud, Stéphanie; Wieder, Fernand; Soppera, Olivier

2012-11-15

Deep-UV lithography using high-efficiency phase mask has been developed to print 100 nm period grating on sol-gel based thin layer. High efficiency phase mask has been designed to produce a high-contrast interferogram (periodic fringes) under water immersion conditions for 244 nm laser. The demonstration has been applied to a new developed immersion-compatible sol-gel layer. A sol-gel photoresist prepared from zirconium alkoxides caped with methacrylic acids was developed to achieve 50 nm resolution in a single step exposure. The nanostructures can be thermally annealed into ZrO(2). Such route considerably simplifies the process for elaborating nanopatterned surfaces of transition metal oxides, and opens new routes for integrating materials of interest for applications in the field of photocatalysis, photovoltaic, optics, photonics or microelectronics.

Hydrogen Production by Steam Reforming of Ethanol over Nickel Catalysts Supported on Sol Gel Made Alumina: Influence of Calcination Temperature on Supports

PubMed Central

Yaakob, Zahira; Bshish, Ahmed; Ebshish, Ali; Tasirin, Siti Masrinda; Alhasan, Fatah H.

2013-01-01

Selecting a proper support in the catalyst system plays an important role in hydrogen production via ethanol steam reforming. In this study, sol gel made alumina supports prepared for nickel (Ni) catalysts were calcined at different temperatures. A series of (Ni/AlS.G.) catalysts were synthesized by an impregnation procedure. The influence of varying the calcination temperature of the sol gel made supports on catalyst activity was tested in ethanol reforming reaction. The characteristics of the sol gel alumina supports and Ni catalysts were affected by the calcination temperature of the supports. The structure of the sol gel made alumina supports was transformed in the order of γ → (γ + θ) → θ-alumina as the calcination temperature of the supports increased from 600 °C to 1000 °C. Both hydrogen yield and ethanol conversion presented a volcano-shaped behavior with maximum values of 4.3 mol/mol ethanol fed and 99.5%, respectively. The optimum values were exhibited over Ni/AlS.G800 (Ni catalyst supported on sol gel made alumina calcined at 800 °C). The high performance of the Ni/AlS.G800 catalyst may be attributed to the strong interaction of Ni species and sol gel made alumina which lead to high nickel dispersion and small particle size. PMID:28809270

Enzymatic liquefaction of agarose above the sol-gel transition temperature using a thermostable endo-type β-agarase, Aga16B.

PubMed

Kim, Jung Hyun; Yun, Eun Ju; Seo, Nari; Yu, Sora; Kim, Dong Hyun; Cho, Kyung Mun; An, Hyun Joo; Kim, Jae-Han; Choi, In-Geol; Kim, Kyoung Heon

2017-02-01

The main carbohydrate of red macroalgae is agarose, a heterogeneous polysaccharide composed of D-galactose and 3,6-anhydro-L-galactose. When saccharifying agarose by enzymes, the unique physical properties of agarose, namely the sol-gel transition and the near-insolubility of agarose in water, limit the accessibility of agarose to the enzymes. Due to the lower accessibility of agarose to enzymes in the gel state than to the sol state, it is important to prevent the sol-gel transition by performing the enzymatic liquefaction of agarose at a temperature higher than the sol-gel transition temperature of agarose. In this study, a thermostable endo-type β-agarase, Aga16B, originating from Saccharophagus degradans 2-40 T , was characterized and introduced in the liquefaction process. Aga16B was thermostable up to 50 °C and depolymerized agarose mainly into neoagarooligosaccharides with degrees of polymerization 4 and 6. Aga16B was applied to enzymatic liquefaction of agarose at 45 °C, which was above the sol-gel transition temperature of 1 % (w/v) agarose (∼35 °C) when cooling agarose. This is the first systematic demonstration of enzymatic liquefaction of agarose, enabled by determining the sol-gel temperature of agarose under specific conditions and by characterizing the thermostability of an endo-type β-agarase.

Hydrogen Production by Steam Reforming of Ethanol over Nickel Catalysts Supported on Sol Gel Made Alumina: Influence of Calcination Temperature on Supports.

PubMed

Yaakob, Zahira; Bshish, Ahmed; Ebshish, Ali; Tasirin, Siti Masrinda; Alhasan, Fatah H

2013-05-30

Selecting a proper support in the catalyst system plays an important role in hydrogen production via ethanol steam reforming. In this study, sol gel made alumina supports prepared for nickel (Ni) catalysts were calcined at different temperatures. A series of (Ni/Al S.G. ) catalysts were synthesized by an impregnation procedure. The influence of varying the calcination temperature of the sol gel made supports on catalyst activity was tested in ethanol reforming reaction. The characteristics of the sol gel alumina supports and Ni catalysts were affected by the calcination temperature of the supports. The structure of the sol gel made alumina supports was transformed in the order of γ → (γ + θ) → θ-alumina as the calcination temperature of the supports increased from 600 °C to 1000 °C. Both hydrogen yield and ethanol conversion presented a volcano-shaped behavior with maximum values of 4.3 mol/mol ethanol fed and 99.5%, respectively. The optimum values were exhibited over Ni/Al S.G800 (Ni catalyst supported on sol gel made alumina calcined at 800 °C). The high performance of the Ni/Al S.G800 catalyst may be attributed to the strong interaction of Ni species and sol gel made alumina which lead to high nickel dispersion and small particle size.

A neutral branched platinum-acetylide complex possessing a tetraphenylethylene core: preparation of a luminescent organometallic gelator and its unexpected spectroscopic behaviour during sol-to-gel transition.

PubMed

Ren, Yuan-Yuan; Wu, Nai-Wei; Huang, Junhai; Xu, Zheng; Sun, Dan-Dan; Wang, Cui-Hong; Xu, Lin

2015-10-21

A neutral branched platinum-acetylide complex TPA possessing a tetraphenylethylene core was successfully prepared, which was found to form luminescent organometallic gels in ethyl acetate. Stimulated by temperature or F(-), the reversible gel-sol transition was realized. More interestingly, TPA exhibited an unexpected blue shift of the emission during the sol-to-gel transition.

A new sol-gel processing routine without chelating agents for preparing highly transparent solutions and nanothin films: engineering the role of chemistry to design the process

NASA Astrophysics Data System (ADS)

Ashiri, Rouholah

2015-01-01

The great sensitivity of titanium alkoxides to hydrolysis makes their sol-gel transformation very fast and thus difficult to control. A method was proposed to alleviate this drawback. Preparation of highly transparent solutions and nanothin films is another objective of the present research. Employing nanoemulsion method and optimizing the processing conditions, a clear solution of well-dispersed nanosized particles was obtained. With the proposed process BaTiO3 precursor sols and nanothin films with enhanced optical transparency towards the visible were prepared. The optimal formulation of the sol consists of acetic acid, barium acetate, 2-propanol, TTIP and deionized water with 6:1:1:1:150 M ratios, respectively. It was found that the reduction of the temperature in the initial stage of mixing of precursors controls the size of the forming species and accordingly improves the stability and transparency of the sol. The results also showed that the applied modifications and optimizations significantly downsize the particles within the sol to the nanometric scale and accordingly result in a significant improvement in the optical response of the products.

Forming foam structures with carbon foam substrates

DOEpatents

Landingham, Richard L.; Satcher, Jr., Joe H.; Coronado, Paul R.; Baumann, Theodore F.

2012-11-06

The invention provides foams of desired cell sizes formed from metal or ceramic materials that coat the surfaces of carbon foams which are subsequently removed. For example, metal is located over a sol-gel foam monolith. The metal is melted to produce a metal/sol-gel composition. The sol-gel foam monolith is removed, leaving a metal foam.

Accelerated weathering of wood surfaces coated with multifunctional allkoxysilanes by sol-gel deposition

Treesearch

Mandla A. Tshabalala; John E. Gangstad

2003-01-01

Accelerated weathering of wood surfaces coated with hexadecyltrimethoxysilane (HDTMOS) in the presence of methyltrimethoxysilane (MTMOS) by the sol-gel process was investigated. The sol-gel process allowed the deposition of a covalently bound thin layer of polysiloxane networks on the wood surface that was resistant to water sorption and water leaching. The rate of...

One-step synthesis of bioactive glass by spray pyrolysis

NASA Astrophysics Data System (ADS)

Shih, Shao-Ju; Chou, Yu-Jen; Chien, I.-Chen

2012-12-01

Bioactive glasses (BGs) have recently received more attention from biologists and engineers because of their potential applications in bone implants. The sol-gel process is one of the most popular methods for fabricating BGs, and has been used to produce BGs for years. However, the sol-gel process has the disadvantages of discontinuous processing and a long processing time. This study presented a one-step spray pyrolysis (SP) synthesis method to overcome these disadvantages. This SP method has synthesized spherical bioactive glass (SBG) and mesoporous bioactive glass (MBG) particles using Si-, Ca- and P-based precursors. This study used transmission electron microscopy, selected area electron diffraction and X-ray dispersive spectroscopy to characterize the microstructure, crystallographic structure, and chemical composition for the BG particles. In addition, in vitro bioactive tests showed the formation of hydroxyl apatite layers on SBG and MBG particles after immersion in simulated body fluid for 5 h. Experimental results show the SP formation mechanisms of SBG and MBG particles.

Luminescence properties of Lu2O3: Tb film prepared by Pechini sol-gel method

NASA Astrophysics Data System (ADS)

Shen, Siqing; Wang, Jian; Xu, Zhibin; Xie, Jianjun; Shi, Ying

2010-10-01

Uniform and crack free Tb3+ doped lutetium oxide (Lu2O3:Tb) films were prepared by Pechini sol-gel method combined with the spin-coating technique. The influence of the different substrate (monocrystalline silicon (111) and silica glass) and atmosphere (N2 and Air) on the luminescence properties of films was investigated. According to the emission spectra, we found that the luminous intensity was higher on silica glass substrate. Moreover, it was found that the luminous intensity calcined in N2 was higher almost twice as that calcined in air.

Luminescence properties of Lu2O3: Tb film prepared by Pechini sol-gel method

NASA Astrophysics Data System (ADS)

Shen, Siqing; Wang, Jian; Xu, Zhibin; Xie, Jianjun; Shi, Ying

2011-02-01

Uniform and crack free Tb3+ doped lutetium oxide (Lu2O3:Tb) films were prepared by Pechini sol-gel method combined with the spin-coating technique. The influence of the different substrate (monocrystalline silicon (111) and silica glass) and atmosphere (N2 and Air) on the luminescence properties of films was investigated. According to the emission spectra, we found that the luminous intensity was higher on silica glass substrate. Moreover, it was found that the luminous intensity calcined in N2 was higher almost twice as that calcined in air.

Sol Gel-Derived SBA-16 Mesoporous Material

PubMed Central

Rivera-Muñoz, Eric M.; Huirache-Acuña, Rafael

2010-01-01

The aim of this article is to review current knowledge related to the synthesis and characterization of sol gel-derived SBA-16 mesoporous silicas, as well as a review of the state of the art in this issue, to take stock of knowledge about current and future applications. The ease of the method of preparation, the orderly structure, size and shape of their pores and control, all these achievable through simple changes in the method of synthesis, makes SBA-16 a very versatile material, potentially applicable in many areas of science and molecular engineering of materials. PMID:20957080

The Preparation of TiO₂ Film by the Sol-Gel Method and Evaluation of Its Self-Cleaning Property.

PubMed

Liang, Yu; Sun, Sijia; Deng, Tongrong; Ding, Hao; Chen, Wanting; Chen, Ying

2018-03-19

TiO₂ sol was produced by the sol-gel method through the hydrolysis and the aging of tetrabutyl titanate and the TiO₂ film was obtained by dipping and uniform lifting of the acid-treated and ultrasound-treated clean glass slides into the TiO₂ sol followed by aging, drying, and calcination. The effect of the hydrolysis control agents to the formed sol was researched and the crystalline state, the morphology, and the photocatalytic properties of the products after calcination were characterized. The structural morphology, the contact angles before and after illumination, and the self-cleaning properties of the TiO₂ film were characterized as well. The results showed that by using acetylacetone as the hydrolysis control agent, the formed TiO₂ sol had relatively high stability. The product after the calcination of the TiO₂ sol was of single anatase type with crystalline size of 18-20 nm and it could degrade nearly 100% of methylene blue after 90 min illumination. The formed TiO₂ film is compact, continuous, smooth, and had the properties of super-hydrophilicity (after 30 min illumination due to its contact angle decreasing from 21° to nearly 0°) and anti-fogging capability, which indicated its excellent self-cleaning property.

Sol-gel derived C-SiC composites and protective coatings for sustained durability in the space environment

NASA Astrophysics Data System (ADS)

Haruvy, Yair; Liedtke, Volker

2003-09-01

Composites and coatings were produced via the fast sol-gel process of a mixture of alkoxysilane precursors. The composites were comprised of carbon fibers, fabrics, or their precursors as reinforcement, and sol-gel-derived silicon carbide as matrix, aiming at high-temperature stable ceramics that can be utilized for re-entry structures. The protective coatings were comprised of fluorine-rich sol-gel derived resins, which exhibit high flexibility and coherence to provide sustained ATOX protection necessary for LEO space-exposed elements. For producing the composites, the sol-gel-derived resin is cast onto the reinforcement fibers/fabrics mat (carbon or its precursors) to produce a 'green' composite that is being cured. The 'green' composite is converted into a C-SiC composite via a gradual heat-pressure process under inert atmosphere, during which the organic substituents on the silicon atoms undergo internal oxidative pyrolysis via the schematic reaction: (SiRO3/2)n -> SiC + CO2 + H2O. The composition of the resultant silicon-oxi-carbide is tailorable via modifying the composition of the sol-gel reactants. The reinforcement, when made of carbon precursors, is converted into carbon during the heat-and-pressure processing as well. The C-SiC composites thus derived exhibit superior thermal stability and comparable thermal conductivity, combined with good mechanical strength features and failure resistance, which render them greatly applicable for re-entry shielding, heat-exchange pipes, and the like. Fluorine rich sol-gel derived coatings were developed as well, via the use of HF rich sol-gel process. These coatings provide oxidation-protection via the silica formation process, together with flexibility that allows 18,000 repetitive folding of the coating without cracking.

Sol-gel encapsulation for controlled drug release and biosensing

NASA Astrophysics Data System (ADS)

Fang, Jonathan

The main focus of this dissertation is to investigate the use of sol-gel encapsulation of biomolecules for controlled drug release and biosensing. Controlled drug release has advantages over conventional therapies in that it maintains a constant, therapeutic drug level in the body for prolonged periods of time. The anti-hypertensive drug Captopril was encapsulated in sol-gel materials of various forms, such as silica xerogels and nanoparticles. The primary objective was to show that sol-gel silica materials are promising drug carriers for controlled release by releasing Captopril at a release rate that is within a therapeutic range. We were able to demonstrate desired release for over a week from Captopril-doped silica xerogels and overall release from Captopril-doped silica nanoparticles. As an aside, the antibiotic Vancomycin was also encapsulated in these porous silica nanoparticles and desired release was obtained for several days in-vitro. The second part of the dissertation focuses on immobilizing antibodies and proteins in sol-gel to detect various analytes, such as hormones and amino acids. Sol-gel competitive immunoassays on antibody-doped silica xerogels were used for hormone detection. Calibration for insulin and C-peptide in standard solutions was obtained in the nM range. In addition, NASA-Ames is also interested in developing a reagentless biosensor using bacterial periplasmic binding proteins (bPBPs) to detect specific biomarkers, such as amino acids and phosphate. These bPBPs were doubly labeled with two different fluorophores and encapsulated in silica xerogels. Ligand-binding experiments were performed on the bPBPs in solution and in sol-gel. Ligand-binding was monitored by fluorescence resonance energy transfer (FRET) between the two fluorophores on the bPBP. Titration data show that one bPBP has retained its ligand-binding properties in sol-gel.

Slow Release of Plant Volatiles Using Sol-Gel Dispensers.

PubMed

Bian, L; Sun, X L; Cai, X M; Chen, Z M

2014-12-01

The black citrus aphid, also known as the tea aphid, (Toxoptera aurantii Boyer) attacks economically important crops, including tea (Camellia sinensis (L.) O. Kuntze). In the current study, silica sol-gel formulations were screened to find one that could carry and release C. sinensis plant volatiles to lure black citrus aphids in a greenhouse. The common plant volatile trans-2-hexen-1-al was used as a model molecule to screen for suitable sol-gel formulations. A zNose (Electronic Sensor Technology, Newbury Park, CA) transportable gas chromatograph was used to continuously monitor the volatile emissions. A sol-gel formulation containing tetramethyl orthosilicate and methyltrimethoxysilane in an 8:2 (vol:vol) ratio was selected to develop a slow-release dispenser. The half-life of trans-2-hexen-1-al in the sol-gel dispenser increased slightly with the volume of this compound in the dispenser. Ten different volatiles were tested in the sol-gel dispenser. Alcohols of 6-10 carbons had the longest half-lives (3.01-3.77 d), while esters of 6-12 carbons had the shortest (1.53-2.28 d). Release of these volatiles from the dispensers could not be detected by the zNose after 16 d (cis-3-hexenyl acetate) to 26 d (3,7-dimethylocta-1,6-dien-3-ol). In greenhouse experiments, trans-2-hexen-1-al and cis-3-hexen-1-ol released from the sol-gel dispensers attracted aphids for ≍17 d, and release of these volatiles could not be detected by the zNose after ≍24 d. The sol-gel dispensers performed adequately for the slow release of plant volatiles to trap aphids in the greenhouse. © 2014 Entomological Society of America.

Hybrid sol-gel optical materials

DOEpatents

Zeigler, J.M.

1993-04-20

Hybrid sol-gel materials comprise silicate sols cross-linked with linear polysilane, polygermane, or poly(silane-germane). The sol-gel materials are useful as optical identifiers in tagging and verification applications and, in a different aspect, as stable, visible light transparent non-linear optical materials. Methyl or phenyl silicones, polyaryl sulfides, polyaryl ethers, and rubbery polysilanes may be used in addition to the linear polysilane. The linear polymers cross-link with the sol to form a matrix having high optical transparency, resistance to thermooxidative aging, adherence to a variety of substrates, brittleness, and a resistance to cracking during thermal cycling.

Hybrid sol-gel optical materials

DOEpatents

Zeigler, John M.

1993-01-01

Hybrid sol-gel materials comprise silicate sols cross-linked with linear polysilane, polygermane, or poly(silane-germane). The sol-gel materials are useful as optical identifiers in tagging and verification applications and, in a different aspect, as stable, visible light transparent non-linear optical materials. Methyl or phenyl silicones, polyaryl sulfides, polyaryl ethers, and rubbery polysilanes may be used in addition to the linear polysilane. The linear polymers cross-link with the sol to form a matrix having high optical transparency, resistance to thermooxidative aging, adherence to a variety of substrates, brittleness, and a resistance to cracking during thermal cycling.

Hybrid sol-gel optical materials

DOEpatents

Zeigler, John M.

1992-01-01

Hybrid sol-gel materials comprise silicate sols cross-linked with linear polysilane, polygermane, or poly(silane-germane). The sol-gel materials are useful as optical identifiers in tagging and verification applications and, in a different aspect, as stable, visible light transparent non-linear optical materials. Methyl or phenyl silicones, polyaryl sulfides, polyaryl ethers, and rubbery polysilanes may be used in addition to the linear polysilane. The linear polymers cross-link with the sol to form a matrix having high optical transparency, resistance to thermooxidative aging, adherence to a variety of substrates, brittleness, and a resistance to cracking during thermal cycling.

Meeting the Challenge of Environmental Regulations in Europe and North America

DTIC Science & Technology

2011-02-08

salts • Electrolytic • Trivalent chromium • Rare earth salts • Sol Gel Socomor Finishing Technologies 24 Ce document et les informations qu’il contient...l’autorisation préalable et écrite de Safran. ASETS DEFENSE 2011 CHROMATE C.C. REPLACEMENT (3) TRIVALENT CHROMIUM • SUITABLE ONLY TO 1000, 3000, 5000...REPLACEMENT(4) ) - TRIVALENT CHROMIUM + TOP COAT - TRIVALENT CHROMIUM + INHIBITORS - OTHER CHEMISTRY BASED - SOL GEL Socomor Finishing Technologies

Ring-Resonator/Sol-Gel Interferometric Immunosensor

NASA Technical Reports Server (NTRS)

Bearman, Gregory; Cohen, David

2007-01-01

A proposed biosensing system would be based on a combination of (1) a sensing volume containing antibodies immobilized in a sol-gel matrix and (2) an optical interferometer having a ring resonator configuration. The antibodies would be specific to an antigen species that one seeks to detect. In the ring resonator of the proposed system, light would make multiple passes through the sensing volume, affording greater interaction length and, hence, greater antibody- detection sensitivity.

Study of Different Sol-Gel Coatings to Enhance the Lifetime of PDMS Devices: Evaluation of Their Biocompatibility.

PubMed

Aymerich, María; Gómez-Varela, Ana I; Álvarez, Ezequiel; Flores-Arias, María T

2016-08-25

A study of PDMS (polydimethylsiloxane) sol-gel-coated channels fabricated using soft lithography and a laser direct writing technique is presented. PDMS is a biocompatible material that presents a high versatility to reproduce several structures. It is widely employed in the fabrication of preclinical devices due to its advantages but it presents a rapid chemical deterioration to organic solvents. The use of sol-gel layers to cover the PDMS overcomes this problem since it provides the robustness of glass for the structures made with PDMS, decreasing its deterioration and changing the biocompatibility of the surface. In this work, PDMS channels are coated with three different kinds of sol-gel compositions (60MTES/40TEOS, 70MTES/30TISP and 80MTES/20TISP). The endothelial cell adhesion to the different coated devices is evaluated in order to determine the most suitable sol-gel preparation conditions to enhance cellular adhesion.

Surfactant-Templated Mesoporous Metal Oxide Nanowires

DOE PAGES

Luo, Hongmei; Lin, Qianglu; Baber, Stacy; ...

2010-01-01

We demore » monstrate two approaches to prepare mesoporous metal oxide nanowires by surfactant assembly and nanoconfinement via sol-gel or electrochemical deposition. For example, mesoporous Ta 2 O 5 and zeolite nanowires are prepared by block copolymer Pluronic 123-templated sol-gel method, and mesoporous ZnO nanowires are prepared by electrodeposition in presence of anionic surfactant sodium dodecyl sulfate (SDS) surfactant, in porous membranes. The morphologies of porous nanowires are studied by scanning electron microscopy (SEM) and transmission electron microscopy (TEM) analyses.« less

Asymmetric bioreduction of acetophenones by Baker's yeast and its cell-free extract encapsulated in sol-gel silica materials

NASA Astrophysics Data System (ADS)

Kato, Katsuya; Nakamura, Hitomi; Nakanishi, Kazuma

2014-02-01

Baker's yeast (BY) encapsulated in silica materials was synthesized using a yeast cell suspension and its cell-free extract during a sol-gel reaction of tetramethoxysilane with nitric acid as a catalyst. The synthesized samples were fully characterized using various methods, such as scanning electron microscopy, nitrogen adsorption-desorption, Fourier transform infrared spectroscopy, thermogravimetry, and differential thermal analysis. The BY cells were easily encapsulated inside silica-gel networks, and the ratio of the cells in the silica gel was approximately 75 wt%, which indicated that a large volume of BY was trapped with a small amount of silica. The enzyme activity (asymmetric reduction of prochiral ketones) of BY and its cell-free extract encapsulated in silica gel was investigated in detail. The activities and enantioselectivities of free and encapsulated BY were similar to those of acetophenone and its fluorine derivatives, which indicated that the conformation structure of BY enzymes inside silica-gel networks did not change. In addition, the encapsulated BY exhibited considerably better solvent (methanol) stability and recyclability compared to free BY solution. We expect that the development of BY encapsulated in sol-gel silica materials will significantly impact the industrial-scale advancement of high-efficiency and low-cost biocatalysts for the synthesis of valuable chiral alcohols.

Integrated optical devices based on sol – gel waveguides using the temperature dependence of the effective refractive index

DOE Office of Scientific and Technical Information (OSTI.GOV)

Pavlov, S V; Trofimov, N S; Chekhlova, T K

2014-07-31

A possibility of designing optical waveguide devices based on sol – gel SiO{sub 2} – TiO{sub 2} films using the temperature dependence of the effective refractive index is shown. The dependences of the device characteristics on the parameters of the film and opticalsystem elements are analysed. The operation of a temperature recorder and a temperature limiter with a resolution of 0.6 K mm{sup -1} is demonstrated. The film and output-prism parameters are optimised. (fibreoptic and nonlinear-optic devices)

Chemistry and Processing of Nanostructured Materials

DOE Office of Scientific and Technical Information (OSTI.GOV)

Fox, G A; Baumann, T F; Hope-Weeks, L J

2002-01-18

Nanostructured materials can be formed through the sol-gel polymerization of inorganic or organic monomer systems. For example, a two step polymerization of tetramethoxysilane (TMOS) was developed such that silica aerogels with densities as low as 3 kg/m{sup 3} ({approx} two times the density of air) could be achieved. Organic aerogels based upon resorcinol-formaldehyde and melamine-formaldehyde can also be prepared using the sol-gel process. Materials of this type have received significant attention at LLNL due to their ultrafine cell sizes, continuous porosity, high surface area and low mass density. For both types of aerogels, sol-gel polymerization depends upon the transformation ofmore » these monomers into nanometer-sized clusters followed by cross-linking into a 3-dimensional gel network. While sol-gel chemistry provides the opportunity to synthesize new material compositions, it suffers from the inability to separate the process of cluster formation from gelation. This limitation results in structural deficiencies in the gel that impact the physical properties of the aerogel, xerogel or nanocomposite. In order to control the properties of the resultant gel, one should be able to regulate the formation of the clusters and their subsequent cross-linking. Towards this goal, we are utilizing dendrimer chemistry to separate the cluster formation from the gelation so that new nanostructured materials can be produced. Dendrimers are three-dimensional, highly branched macromolecules that are prepared in such a way that their size, shape and surface functionality are readily controlled. The dendrimers will be used as pre-formed clusters of known size that can be cross-linked to form an ordered gel network.« less

Aptamer entrapment in microfluidic channel using one-step sol-gel process, in view of the integration of a new selective extraction phase for lab-on-a-chip.

PubMed

Perréard, Camille; d'Orlyé, Fanny; Griveau, Sophie; Liu, Baohong; Bedioui, Fethi; Varenne, Anne

2017-10-01

There is a great demand for integrating sample treatment into μTASs. In this context, we developed a new sol-gel phase for extraction of trace compounds in complex matrices. For this purpose, the incorporation of aptamers in silica-based gel within PDMS/glass microfluidic channels was performed for the first time by a one-step sol-gel process. The effective gel attachment onto microchannel walls and aptamer incorporation in the polymerized gel were evaluated using fluorescence microscopy. A good gel stability and aptamer incorporation inside the microchannel was demonstrated upon rinsing and over storage time. The ability of gel-encapsulated aptamers to interact with its specific target (either sulforhodamine B as model fluorescent target, or diclofenac, a pain killer drug) was assessed too. The binding capacity of entrapped aptamers was quantified (in the micromolar range) and the selectivity of the interaction was evidenced. Preservation of aptamers binding affinity to target molecules was therefore demonstrated. Dissociation constant of the aptamer-target complex and interaction selectivity were evaluated similar to those in bulk solution. This opens the way to new selective on-chip SPE techniques for sample pretreatment. © 2017 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Liposomes as protective capsules for active silica sol-gel biocomposite synthesis.

PubMed

Li, Ye; Yip, Wai Tak

2005-09-21

Using liposome to shield an enzyme from hostile chemical environments during the sol-gel formation process has resulted in a novel approach to synthesizing silica sol-gel biocomposite materials. By reporting the encapsulation of horseradish peroxidase and firefly luciferase, we demonstrate that this new protocol can produce silica biocomposites that are more active than trapping the enzymes directly into hydrogels.

Weathering characteristics and moisture uptake properties of wood coated with water-borne sol-gel thin films

Treesearch

M. A. Tshabalala; C. Starr; N. R. Sutherland

2010-01-01

In this study, wood specimens were coated with water-borne silsesquioxane oligomers by an in situ sol-gel deposition process. The effect of these water-borne sol-gel thin films on weathering characteristics and moisture-uptake properties of the wood specimens were investigated. The weathering characteristics were investigated by exposure of the specimens to artificial...

Radiation hardening of sol gel-derived silica fiber preforms through fictive temperature reduction.

PubMed

Hari Babu, B; Lancry, Matthieu; Ollier, Nadege; El Hamzaoui, Hicham; Bouazaoui, Mohamed; Poumellec, Bertrand

2016-09-20

The impact of fictive temperature (T_f) on the evolution of point defects and optical attenuation in non-doped and Er³⁺-doped sol-gel silica glasses was studied and compared to Suprasil F300 and Infrasil 301 glasses before and after γ-irradiation. To this aim, sol-gel optical fiber preforms have been fabricated by the densification of erbium salt-soaked nanoporous silica xerogels through the polymeric sol-gel technique. These γ-irradiated fiber preforms have been characterized by FTIR, UV-vis-NIR absorption spectroscopy, electron paramagnetic resonance, and photoluminescence measurements. We showed that a decrease in the glass fictive temperature leads to a decrease in the glass disorder and strained bonds. This mainly results in a lower defect generation rate and thus less radiation-induced attenuation in the UV-vis range. Furthermore, it was found that γ-radiation "hardness" is higher in Er³⁺-doped sol-gel silica compared to un-doped sol-gel silica and standard synthetic silica glasses. The present work demonstrates an effective strategy to improve the radiation resistance of optical fiber preforms and glasses through glass fictive temperature reduction.

Biodegradable and adjustable sol-gel glass based hybrid scaffolds from multi-armed oligomeric building blocks.

PubMed

Kascholke, Christian; Hendrikx, Stephan; Flath, Tobias; Kuzmenka, Dzmitry; Dörfler, Hans-Martin; Schumann, Dirk; Gressenbuch, Mathias; Schulze, F Peter; Schulz-Siegmund, Michaela; Hacker, Michael C

2017-11-01

Biodegradability is a crucial characteristic to improve the clinical potential of sol-gel-derived glass materials. To this end, a set of degradable organic/inorganic class II hybrids from a tetraethoxysilane(TEOS)-derived silica sol and oligovalent cross-linker oligomers containing oligo(d,l-lactide) domains was developed and characterized. A series of 18 oligomers (Mn: 1100-3200Da) with different degrees of ethoxylation and varying length of oligoester units was established and chemical composition was determined. Applicability of an established indirect rapid prototyping method enabled fabrication of a total of 85 different hybrid scaffold formulations from 3-isocyanatopropyltriethoxysilane-functionalized macromers. In vitro degradation was analyzed over 12months and a continuous linear weight loss (0.2-0.5wt%/d) combined with only moderate material swelling was detected which was controlled by oligo(lactide) content and matrix hydrophilicity. Compressive strength (2-30MPa) and compressive modulus (44-716MPa) were determined and total content, oligo(ethylene oxide) content, oligo(lactide) content and molecular weight of the oligomeric cross-linkers as well as material porosity were identified as the main factors determining hybrid mechanics. Cytocompatibility was assessed by cell culture experiments with human adipose tissue-derived stem cells (hASC). Cell migration into the entire scaffold pore network was indicated and continuous proliferation over 14days was found. ALP activity linearly increased over 2weeks indicating osteogenic differentiation. The presented glass-based hybrid concept with precisely adjustable material properties holds promise for regenerative purposes. Adaption of degradation kinetics toward physiological relevance is still an unmet challenge of (bio-)glass engineering. We therefore present a glass-derived hybrid material with adjustable degradation. A flexible design concept based on degradable multi-armed oligomers was combined with an established indirect rapid prototyping method to produce a systematic set of porous sol-gel-derived class II hybrid scaffolds. Mechanical properties in the range of cancellous bone were narrowly controlled by hybrid composition. The oligoester introduction resulted in significantly increased compressive moduli. Cytocompatible hybrids degraded in physiologically relevant time frames and a promising linear and controllable weight loss profile was found. To our knowledge, our degradation study represents the most extensive long-term investigation of sol-gel-derived class II hybrids. Due to the broad adjustability of material properties, our concept offers potential for engineering of biodegradable hybrid materials for versatile applications. Copyright © 2017. Published by Elsevier Ltd.

Electrochemical sensor based on molecularly imprinted polymer film via sol-gel technology and multi-walled carbon nanotubes-chitosan functional layer for sensitive determination of quinoxaline-2-carboxylic acid.

PubMed

Yang, Yukun; Fang, Guozhen; Liu, Guiyang; Pan, Mingfei; Wang, Xiaomin; Kong, Lingjie; He, Xinlei; Wang, Shuo

2013-09-15

Quinoxaline-2-carboxylic acid (QCA) is difficult to measure since only trace levels are present in commercial meat products. In this study, a rapid, sensitive and selective molecularly imprinted electrochemical sensor for QCA determination was successfully constructed by combination of a novel modified glassy carbon electrode (GCE) and differential pulse voltammetry (DPV). The GCE was fabricated via stepwise modification of multi-walled carbon nanotubes (MWNTs)-chitosan (CS) functional composite and a sol-gel molecularly imprinted polymer (MIP) film on the surface. MWNTs-CS composite was used to enhance the electron transfer rate and expand electrode surface area, and consequently amplify QCA reduction electrochemical response. The imprinted mechanism and experimental parameters affecting the performance of MIP film were discussed in detail. The resulting MIP/sol-gel/MWNTs-CS/GCE was characterized using various electrochemical methods involving cyclic voltammetry (CV), electrochemical impedance spectroscopy (EIS) and DPV. The sensor using MIP/sol-gel/MWNTs-CS/GCE as working electrode showed a linear current response to the target QCA concentration in the wide range from 2.0×10(-6) to 1.0×10(-3)molL(-1) with a low detection limit of 4.4×10(-7)molL(-1) (S/N=3). The established sensor with excellent reproductivity and stability was applied to evaluate commercial pork products. At five concentration levels, the recoveries and standard deviations were calculated as 93.5-98.6% and 1.7-3.3%, respectively, suggesting the proposed sensor is promising for the accurate quantification of QCA at trace levels in meat samples. Copyright © 2013 Elsevier B.V. All rights reserved.

Transparent Glass-Ceramics Produced by Sol-Gel: A Suitable Alternative for Photonic Materials

PubMed Central

Gorni, Giulio; Mosa, Jadra; Balda, Rolindes; Fernández, Joaquin; Durán, Alicia; Castro, Yolanda

2018-01-01

Transparent glass-ceramics have shown interesting optical properties for several photonic applications. In particular, compositions based on oxide glass matrices with fluoride crystals embedded inside, known as oxyfluoride glass-ceramics, have gained increasing interest in the last few decades. Melt-quenching is still the most used method to prepare these materials but sol-gel has been indicated as a suitable alternative. Many papers have been published since the end of the 1990s, when these materials were prepared by sol-gel for the first time, thus a review of the achievements obtained so far is necessary. In the first part of this paper, a review of transparent sol-gel glass-ceramics is made focusing mainly on oxyfluoride compositions. Many interesting optical results have been obtained but very little innovation of synthesis and processing is found with respect to pioneering papers published 20 years ago. In the second part we describe the improvements in synthesis and processing obtained by the authors during the last five years. The main achievements are the preparation of oxyfluoride glass-ceramics with a much higher fluoride crystal fraction, at least double that reported up to now, and the first synthesis of NaGdF4 glass-ceramics. Moreover, a new SiO2 precursor was introduced in the synthesis, allowing for a reduction in the treatment temperature and favoring hydroxyl group removal. Interesting optical properties demonstrated the incorporation of dopant ions in the fluoride crystals, thus obtaining crystal-like spectra along with higher efficiencies with respect to xerogels, and hence demonstrating that these materials are a suitable alternative for photonic applications. PMID:29385706

Synthesis of microspheres of triuranium octaoxide by simultaneous water and nitrate extraction from ascorbate-uranyl sols.

PubMed

Brykala, M; Deptula, A; Rogowski, M; Lada, W; Olczak, T; Wawszczak, D; Smolinski, T; Wojtowicz, P; Modolo, G

A new method for synthesis of uranium oxide microspheres (diameter <100 μm) has been developed. It is a variant of our patented Complex Sol-Gel Process, which has been used to synthesize high-quality powders of a wide variety of complex oxides. Starting uranyl-nitrate-ascorbate sols were prepared by addition of ascorbic acid to uranyl nitrate hexahydrate solution and alkalizing by aqueous ammonium hydroxide and then emulsified in 2-ethylhexanol-1 containing 1v/o SPAN-80. Drops of emulsion were firstly gelled by extraction of water by the solvent. Destruction of the microspheres during thermal treatment, owing to highly reactive components in the gels, requires modification of the gelation step by Double Extraction Process-simultaneously extraction of water and nitrates using Primene JMT, which completely eliminates these problem. Final step was calcination in air of obtained microspheres of gels to triuranium octaoxide.

Wet powder processing of sol-gel derived mesoporous silica-hydroxyapatite hybrid powders.

PubMed

Andersson, Jenny; Johannessen, Espen; Areva, Sami; Järn, Mikael; Lindén, Mika

2006-08-01

This paper describes a method by which a porous silica coating layer can be obtained on different apatite particles through a simple sol-gel synthesis route. Sol-gel derived powders of hydroxyapatite (HAP) and beta tricalciumphosphate (beta-TCP) were coated with a mesoporous silica using C16TAB (hexadecyltrimethylammonium bromide) as a template in order to induce mesophase formation. Further calcination of the material removes the template from the mesophase and leaves a highly ordered hexagonal arranged mesoporous silica structure with a core of HAP/beta-TCP. The phase purity of the SiO2/apatite composites has been thoroughly investigated by the means of FT-IR, XRD, and solid state 31P MAS NMR. The phase purity of these materials is shown to be dependent on the solubility properties of the used apatites. The hybrid materials are suitable as a multifunctional biomaterial where osteoconductive properties can be combined with drug delivery.

Optical properties of rhodamine 6G-doped TiO2 sol-gel films

NASA Astrophysics Data System (ADS)

Tomás, S. A.; Stolik, S.; Palomino, R.; Lozada, R.; Persson, C.; Ahuja, R.; Pepe, I.; Ferreira da Silva, A.

2005-06-01

The optical properties of titania (TiO2) thin films prepared by the sol-gel process and doped with rhodamine 6G were studied by Photoacoustic Spectroscopy. Rhodamine 6G-doping was achieved by adding 0.01%, 0.02%, 0.05% y 0.1% mol rhodamine to a solution that contained titanium isopropoxide as precursor. Two absorption regions were distinguished in the absorption spectrum of a typical rhodamine 6G-doped TiO2 film. A shift of these bands occured as a function of rhodamine 6G-doping concentration. In addition, the optical absorption and band gap energy for rutile-phase TiO2 films were calculated employing the full-potential linearized augmented plane wave method. A comparison of these calculations with experimental data of TiO2 films prepared by sol-gel at room temperature was performed.

Anti-adhesive effect of poloxamer-based thermo-sensitive sol-gel in rabbit laminectomy model.

PubMed

Shin, Sung Joon; Lee, Jae Hyup; So, Jungwon; Min, Kyungdan

2016-11-01

Poloxamer-based thermo-sensitive sol-gel has been developed to reduce the incidence of postoperative scar formation at the laminectomy site. The purpose of this study was to evaluate the anti-adhesive effect of poloxamer based thermo-sensitive sol-gel compared to hyaluronate based solution after laminectomy, using a rabbit model. A thermo-sensitive anti-adhesive with a property of sol-gel transition was manufactured by a physical mixture of Poloxamer188/407, Chitosan and Gelatin. The viscosity in different temperatures was assessed. 72 adult New Zealand rabbits underwent lumbar laminectomy and were randomly divided into experimental (treated with the newly developed agent), positive (treated with hyaluronate based solution), and negative control groups. Each group was subdivided into 1 and 4-week subgroups. Gross and histological evaluations were performed to assess the extent of epidural adhesion. The experimental group showed significantly higher viscosity compared to the positive control group and showed a significant increase of viscosity as the temperature increased. Gross evaluation showed no statistically significant differences between the 1- and 4-week subgroups. However, histologic evaluation showed significant differences both in 1- and 4-week subgroups. Although the 4-week histologic results of the experimental and the positive control subgroups showed no significant difference, both subgroups revealed higher value compared to the negative control subgroup with regard to the ratio of adhesion less than 50 %. The new poloxamer based thermo-sensitive agent showed superior efficacy over the hyaluronate based agent at 1 week postoperatively. At 4 weeks postoperatively, there were no statistically significant differences between the two agents, although both showed efficacy over the sham group.

Fabrication and characterization of sol-gel based nanoparticles for drug delivery

NASA Astrophysics Data System (ADS)

Yadav, Reeta

Nanogels are cross linked polymeric sol-gel based nanoparticles that offer an interior network for incorporation and protection of biomolecules, exhibiting unique advantages for polymer based delivery systems. We have successfully synthesized stable sol-gel nanoparticles by means of [a] silicification reactions using cationic peptides like polylysine as gelating agents, and [b] lyophilization of sol-gels. Macromolecules such as Hemoglobin and Glucose Oxidase and small molecules such as Sodium Nitroprusside (SNP) and antibiotics were encapsulated within the nanogels. We have used transmission electron microscopy, dynamic light scattering, zeta potential analysis, and spectroscopy to perform a physicochemical characterization of the nanogels resulting from the two approaches. Our studies have indicated that the nanogel encapsulated proteins and small molecules remain intact, stable and functional. A Hydrogen Peroxide (H2O2) and Nitric Oxide (NO) generating drug carrier was synthesized using these nanogels and the effect of generation of H2O2 from Glucose Oxidase encapsulated nanogels and NO from SNP encapsulated nanogels was tested on E.coli. The results show that the nanoparticles exert antimicrobial activity against E.Coli, in addition NO generating nanogels potentiated H2O2 generating nanogels induced killing. These data suggest that these NO and H2O2 releasing nanogels have the potential to serve as a novel class of antimicrobials for the treatment of multidrug resistant bacteria. The unique properties of these protein/drug incorporated nanogels raise the prospect of fine tailoring to specific applications such as drug delivery and bio imaging.

Sol-Gel Deposited Double Layer TiO₂ and Al₂O₃ Anti-Reflection Coating for Silicon Solar Cell.

PubMed

Jung, Jinsu; Jannat, Azmira; Akhtar, M Shaheer; Yang, O-Bong

2018-02-01

In this work, the deposition of double layer ARC on p-type Si solar cells was carried out by simple spin coating using sol-gel derived Al2O3 and TiO2 precursors for the fabrication of crystalline Si solar cells. The first ARC layer was created by freshly prepared sol-gel derived Al2O3 precursor using spin coating technique and then second ARC layer of TiO2 was deposited with sol-gel derived TiO2 precursor, which was finally annealed at 400 °C. The double layer Al2O3/TiO2 ARC on Si wafer exhibited the low average reflectance of 4.74% in the wavelength range of 400 and 1000 nm. The fabricated solar cells based on double TiO2/Al2O3 ARC attained the conversion efficiency of ~13.95% with short circuit current (JSC) of 35.27 mA/cm2, open circuit voltage (VOC) of 593.35 mV and fill factor (FF) of 66.67%. Moreover, the fabricated solar cells presented relatively low series resistance (Rs) as compared to single layer ARCs, resulting in the high VOC and FF.

Preparation of Composite Coating on AZ91D Magnesium Alloy by Silica Sol-Micro Oxidation

NASA Astrophysics Data System (ADS)

Shao, Zhongcai; Zhang, Feifei; Zhao, Ruiqiang; Shen, Xiaoyi

2016-03-01

Composite coating was prepared on AZ91D magnesium alloy with a new method which combined silica sol with micro-arc oxidation (MAO). The MAO coating was prepared on the basis of MAO solution, and then coated by sol-gel process. The composite coating was obtained after second MAO treatment. Scanning electron microscopy coupled with X-ray diffraction (XRD), energy spectrum analysis and electrochemical testing was applied to characterize the properties of MAO coating and composite coating. The experimental test results indicated that the Si element derived from SiO2 gel particle embedded into the MAO coating by second MAO treatment. The surface of composite coating became dense and the holes were smaller with silica sol sealing process. The corrosion resistance of composite coating was improved than the MAO coating.

The Effect of Poly (Glycerol Sebacate) Incorporation within Hybrid Chitin-Lignin Sol-Gel Nanofibrous Scaffolds.

PubMed

Abudula, Tuerdimaimaiti; Gzara, Lassaad; Simonetti, Giovanna; Alshahrie, Ahmed; Salah, Numan; Morganti, Pierfrancesco; Chianese, Angelo; Fallahi, Afsoon; Tamayol, Ali; Bencherif, Sidi A; Memic, Adnan

2018-03-19

Chitin and lignin primarily accumulate as bio-waste resulting from byproducts of crustacean crusts and plant biomass. Recently, their use has been proposed for diverse and unique bioengineering applications, amongst others. However, their weak mechanical properties need to be improved in order to facilitate their industrial utilization. In this paper, we fabricated hybrid fibers composed of a chitin-lignin (CL)-based sol-gel mixture and elastomeric poly (glycerol sebacate) (PGS) using a standard electrospinning approach. Obtained results showed that PGS could be coherently blended with the sol-gel mixture to form a nanofibrous scaffold exhibiting remarkable mechanical performance and improved antibacterial and antifungal activity. The developed hybrid fibers showed promising potential in advanced biomedical applications such as wound care products. Ultimately, recycling these sustainable biopolymers and other bio-wastes alike could propel a "greener" economy.

Metal-doped organic gels and method thereof

DOEpatents

Satcher, Jr., Joe H.; Baumann, Theodore F.

2003-09-02

Disclosed herein is a sol-gel polymerization process for synthesizing metal-doped organic gels. The process polymerizes metal salts of hydroxylated benzenes or hydroxylated benzene derivatives with alkyl or aryl aldehydes to form metal-doped, wet, organic gels. The gels can then be dried by supercritical solvent extraction to form metal-doped aerogels or by evaporation to form metal-doped xerogels. The aerogels and xerogels can then be pyrolyzed.

Metal-doped organic gels and method thereof

DOEpatents

Satcher, Jr., Joe H.; Baumann, Theodore F.

2007-10-23

Disclosed herein is a sol-gel polymerization process for synthesizing metal-doped organic gels. The process polymerizes metal salts of hydroxylated benzenes or hydroxylated benzene derivatives with alkyl or aryl aldehydes to form metal-doped, wet, organic gels. The gels can then be dried by supercritical solvent extraction to form metal-doped aerogels or by evaporation to form metal-doped xerogels. The aerogels and xerogels can then be pyrolyzed.

Sol-Gel Thin Films for Plasmonic Gas Sensors

PubMed Central

Della Gaspera, Enrico; Martucci, Alessandro

2015-01-01

Plasmonic gas sensors are optical sensors that use localized surface plasmons or extended surface plasmons as transducing platform. Surface plasmons are very sensitive to dielectric variations of the environment or to electron exchange, and these effects have been exploited for the realization of sensitive gas sensors. In this paper, we review our research work of the last few years on the synthesis and the gas sensing properties of sol-gel based nanomaterials for plasmonic sensors. PMID:26184216

Composite Biomaterials Based on Sol-Gel Mesoporous Silicate Glasses: A Review

PubMed Central

Baino, Francesco; Fiorilli, Sonia; Vitale-Brovarone, Chiara

2017-01-01

Bioactive glasses are able to bond to bone and stimulate the growth of new tissue while dissolving over time, which makes them ideal materials for regenerative medicine. The advent of mesoporous glasses, which are typically synthesized via sol-gel routes, allowed researchers to develop a broad and versatile class of novel biomaterials that combine superior bone regenerative potential (compared to traditional melt-derived glasses) with the ability of incorporating drugs and various biomolecules for targeted therapy in situ. Mesoporous glass particles can be directly embedded as a bioactive phase within a non-porous (e.g., microspheres), porous (3D scaffolds) or injectable matrix, or be processed to manufacture a surface coating on inorganic or organic (macro)porous substrates, thereby obtaining hierarchical structures with multiscale porosity. This review provides a picture of composite systems and coatings based on mesoporous glasses and highlights the challenges for the future, including the great potential of inorganic–organic hybrid sol-gel biomaterials. PMID:28952496

Electrochemical luminescence determination of hyperin using a sol-gel@graphene luminescent composite film modified electrode for solid phase microextraction

NASA Astrophysics Data System (ADS)

Zou, Xiaojun; Shang, Fang; Wang, Sui

2017-02-01

In this paper, a novel electrochemiluminescence (ECL) sensor of sol-gel@graphene luminescent composite film modified electrode for hyperin determination was prepared using graphene (G) as solid-phase microextraction (SPME) material, based on selective preconcentration of target onto an electrode and followed by luminol ECL detection. Hyperin was firstly extracted from aqueous solution through the modified GCE. Hydrogel, electrogenerated chemiluminescence reagents, pH of working solution, extraction time and temperature and scan rate were discussed. Under the optimum conditions, the change of ECL intensity was in proportion to the concentration of hyperin in the range of 0.02-0.24 μg/mL with a detection limit of 0.01 μg/mL. This method showed good performance in stability, reproducibility and precision for the determination of hyperin.

Magneto-Sensitive Adsorbents Modified by Functional Nitrogen-Containing Groups

NASA Astrophysics Data System (ADS)

Melnyk, Inna V.; Gdula, Karolina; Dąbrowski, Andrzej; Zub, Yuriy L.

2016-02-01

In order to obtain amino-functionalized silica materials with magnetic core, one-step synthesis was carried out. Several materials, differ in number and structure of amino groups, were synthesized on the basis of sol-gel method. The synthesized materials were examined by several analytical techniques. The presence and content of amino groups were measured by using Diffuse Reflectance Infrared Fourier Transform (DRIFT) spectroscopy and acid-base titration, respectively. Specific surface areas were measured by nitrogen/adsorption desorption isotherms. It was proved that sol-gel approach leads to obtain materials with high content of amino groups built into their surfaces (in the range 1.6-2.7 mmol/g). As-obtained materials were tested as potential adsorbents for copper(II) ions. The received maximum adsorption capacities were in the range 0.4-0.7 mmol/g.

The Sol-Gel-Xerogel Transition

DTIC Science & Technology

1993-11-01

basic pH. Bioactive sol-gel glasses obtained by a surface adsorption of trypsin to a readymade xerogel were also completley * L...presence of siloxane chains and hydrophobic methyl groups an easy film deposition on glass sheets can be obtained. Rhodamine 6G and Coumarin 4 were...Research Proposal was prepared (early 1989) have witnessed a tremendous, almost explosive, progress in the field of organically doped sol-gel glasses

Sol-gel dip coating of yttria-stabilized tetragonal zirconia dental ceramic by aluminosilicate nanocomposite as a novel technique to improve the bonding of veneering porcelain.

PubMed

Madani, Azamsadat; Nakhaei, Mohammadreza; Karami, Parisa; Rajabzadeh, Ghadir; Salehi, Sahar; Bagheri, Hossein

2016-01-01

The aim of this in vitro study was to evaluate the effect of silica and aluminosilicate nanocomposite coating of zirconia-based dental ceramic by a sol-gel dip-coating technique on the bond strength of veneering porcelain to the yttria-stabilized tetragonal zirconia polycrystal (Y-TZP) in vitro. Thirty Y-TZP blocks (10 mm ×10 mm ×3 mm) were prepared and were assigned to four experimental groups (n=10/group): C, without any further surface treatment as the control group; S, sandblasted using 110 μm alumina powder; Si, silica sol dip coating + calcination; and Si/Al, aluminosilicate sol dip coating + calcination. After preparing Y-TZP samples, a 3 mm thick layer of the recommended porcelain was fired on the coated Y-TZP surface. Fourier transform infrared spectroscopy (FT-IR), X-ray diffraction (XRD), scanning electron microscopy (SEM), and energy-dispersive X-ray analysis were used to characterize the coating and the nature of the bonding between the coating and zirconia. To examine the zirconia-porcelain bond strength, a microtensile bond strength (μTBS) approach was chosen. FT-IR study showed the formation of silica and aluminosilicate materials. XRD pattern showed the formation of new phases consisting of Si, Al, and Zr in coated samples. SEM showed the formation of a uniform coating on Y-TZP samples. Maximum μTBS values were obtained in aluminosilicate samples, which were significantly increased compared to control and sandblasted groups (P=0.013 and P<0.001, respectively). This study showed that aluminosilicate sol-gel dip coating can be considered as a convenient, less expensive reliable method for improving the bond strength between dental Y-TZP ceramics and veneering porcelain.

Methods for and products of processing nanostructure nitride, carbonitride and oxycarbonitride electrode power materials by utilizing sol gel technology for supercapacitor applications

DOEpatents

Huang, Yuhong; Wei, Oiang; Chu, Chung-tse; Zheng, Haixing

2001-01-01

Metal nitride, carbonitride, and oxycarbonitride powder with high surface area (up to 150 m.sup.2 /g) is prepared by using sol-gel process. The metal organic precursor, alkoxides or amides, is synthesized firstly. The metal organic precursor is modified by using unhydrolyzable organic ligands or templates. A wet gel is formed then by hydrolysis and condensation process. The solvent in the wet gel is then be removed supercritically to form porous amorphous hydroxide. This porous hydroxide materials is sintered to 725.degree. C. under the ammonia flow and porous nitride powder is formed. The other way to obtain high surface area nitride, carbonitride, and oxycarbonitride powder is to pyrolyze polymerized templated metal amides aerogel in an inert atmosphere. The electrochemical capacitors are prepared by using sol-gel prepared nitride, carbonitride, and oxycarbonitride powder. Two methods are used to assemble the capacitors. Electrode is formed either by pressing the mixture of nitride powder and binder to a foil, or by depositing electrode coating onto metal current collector. The binder or coating is converted into a continuous network of electrode material after thermal treatment to provide enhanced energy and power density. Liquid electrolyte is soaked into porous electrode. The electrochemical capacitor assembly further has a porous separator layer between two electrodes/electrolyte and forming a unit cell.

Piezoelectric Sol-Gel Composite Film Fabrication by Stencil Printing.

PubMed

Kaneko, Tsukasa; Iwata, Kazuki; Kobayashi, Makiko

2015-09-01

Piezoelectric films using sol-gel composites could be useful as ultrasonic transducers in various industrial fields. For sol-gel composite film fabrication, the spray coating technique has been used often because of its adaptability for various substrates. However, the spray technique requires multiple spray coating processes and heating processes and this is an issue of concern, especially for on-site fabrication in controlled areas. Stencil printing has been developed to solve this issue because this method can be used to fabricate thick sol-gel composite films with one coating process. In this study, PbTiO3 (PT)/Pb(Zr,Ti)O3 (PZT) films, PZT/PZT films, and Bi4Ti3O12 (BiT)/PZT films were fabricated by stencil printing, and PT/ PZT films were also fabricated using the spray technique. After fabrication, a thermal cycle test was performed for the samples to compare their ultrasonic performance. The sensitivity and signal-to-noise-ratio (SNR) of the ultrasonic response of PT/PZT fabricated by stencil printing were equivalent to those of PT/PZT fabricated by the spray technique, and better than those of other samples between room temperature and 300°C. Therefore, PT/PZT films fabricated by stencil printing could be a good candidate for nondestructive testing (NDT) ultrasonic transducers from room temperature to 300°C.

Microstructural changes in NiFe{sub 2}O{sub 4} ceramics prepared with powders derived from different fuels in sol-gel auto-combustion technique

DOE Office of Scientific and Technical Information (OSTI.GOV)

Chauhan, Lalita, E-mail: chauhan.lalita5@gmail.com; Sreenivas, K.; Bokolia, Renuka

2016-05-23

Structural properties of Nickel ferrite (NiFe{sub 2}O{sub 4}) ceramics prepared from powders derived from sol gel auto-combustion method using different fuels (citric acid, glycine and Dl-alanine) are compared. Changes in the structural properties at different sintering temperatures are investigated. X-ray diffraction (XRD) confirms the formation of single phase material with cubic structure. Ceramics prepared using the different powders obtained from different fuels show that that there are no significant changes in lattice parameters. However increasing sintering temperatures show significant improvement in density and grain size. The DL-alanine fuel is found to be the most effective fuel for producing NIFe{sub 2}O{submore » 4} powders by the sol-gel auto combustion method and yields highly crystalline powders in the as-burnt stage itself at a low temperature (80 °C). Subsequent use of the powders in ceramic manufacturing produces dense NiFe{sub 2}O{sub 4} ceramics with a uniform microstructure and a large grain size.« less

Fabrication of optical chemical ammonia sensors using anodized alumina supports and sol-gel method.

PubMed

Markovics, Akos; Kovács, Barna

2013-05-15

In this comparative study, the fabrication and the sensing properties of various reflectometric optical ammonia gas sensors are described. In the first set of experiments the role of the support material was investigated on four different sensor membranes. Two of them were prepared by the adsorption of bromocresol green indicator on anodized aluminum plates. The applied anodizing voltages were 12 V and 24 V, which resulted in different dynamic ranges and response times for gaseous ammonia. The sol-gel method was used for the preparation of the other batch of sensors. These layers were coated on anodized aluminum plates (24 V) and on standard microscope cover glasses. In spite of the identical sensing chemistry, slightly different response times were measured merely because of the aluminum surface porosity. Gas molecules can remain entrapped in the pores, which results in delayed recovery time. On the other hand, the porous oxide film provides excellent adhesion, making the anodized aluminum an attractive support for the sol-gel layer. Copyright © 2013 Elsevier B.V. All rights reserved.

Tubular and Spherical SiO₂ Obtained by Sol Gel Method for Lipase Immobilization and Enzymatic Activity.

PubMed

Anastasescu, Crina; Preda, Silviu; Rusu, Adriana; Culita, Dana; Plavan, Gabriel; Strungaru, Stefan; Calderon-Moreno, Jose Maria; Munteanu, Cornel; Gifu, Catalina; Enache, Mirela; Socoteanu, Radu; Angelescu, Daniel; Anastasescu, Mihai; Gartner, Mariuca; Balint, Ioan; Zaharescu, Maria

2018-06-05

A wide range of hybrid biomaterials has been designed in order to sustain bioremediation processes by associating sol-gel SiO₂ matrices with various biologically active compounds (enzymes, antibodies). SiO₂ is a widespread, chemically stable and non-toxic material; thus, the immobilization of enzymes on silica may lead to improving the efficiency of biocatalysts in terms of endurance and economic costs. Our present work explores the potential of different hybrid morphologies, based on hollow tubes and solid spheres of amorphous SiO₂, for enzyme immobilization and the development of competitive biocatalysts. The synthesis protocol and structural characterization of spherical and tubular SiO₂ obtained by the sol gel method were fully investigated in connection with the subsequent immobilization of lipase from Rhizopus orizae . The immobilization is conducted at pH 6, lower than the isoelectric point of lipase and higher than the isoelectric point of silica, which is meant to sustain the physical interactions of the enzyme with the SiO₂ matrix. The morphological, textural and surface properties of spherical and tubular SiO₂ were investigated by SEM, nitrogen sorption, and electrokinetic potential measurements, while the formation and characterization of hybrid organic-inorganic complexes were studied by UV-VIS, FTIR-ATR and fluorescence spectroscopy. The highest degree of enzyme immobilization (as depicted from total organic carbon) was achieved for tubular morphology and the hydrolysis of p-nitrophenyl acetate was used as an enzymatic model reaction conducted in the presence of hybrid lipase⁻SiO₂ complex.

Sol-gel Technology and Advanced Electrochemical Energy Storage Materials

NASA Technical Reports Server (NTRS)

Chu, Chung-tse; Zheng, Haixing

1996-01-01

Advanced materials play an important role in the development of electrochemical energy devices such as batteries, fuel cells, and electrochemical capacitors. The sol-gel process is a versatile solution for use in the fabrication of ceramic materials with tailored stoichiometry, microstructure, and properties. This processing technique is particularly useful in producing porous materials with high surface area and low density, two of the most desirable characteristics for electrode materials. In addition,the porous surface of gels can be modified chemically to create tailored surface properties, and inorganic/organic micro-composites can be prepared for improved material performance device fabrication. Applications of several sol-gel derived electrode materials in different energy storage devices are illustrated in this paper. V2O5 gels are shown to be a promising cathode material for solid state lithium batteries. Carbon aerogels, amorphous RuO2 gels and sol-gel derived hafnium compounds have been studied as electrode materials for high energy density and high power density electrochemical capacitors.

Novel Materials through Non-Hydrolytic Sol-Gel Processing: Negative Thermal Expansion Oxides and Beyond

PubMed Central

Lind, Cora; Gates, Stacy D.; Pedoussaut, Nathalie M.; Baiz, Tamam I.

2010-01-01

Low temperature methods have been applied to the synthesis of many advanced materials. Non-hydrolytic sol-gel (NHSG) processes offer an elegant route to stable and metastable phases at low temperatures. Excellent atomic level homogeneity gives access to polymorphs that are difficult or impossible to obtain by other methods. The NHSG approach is most commonly applied to the preparation of metal oxides, but can be easily extended to metal sulfides. Exploration of experimental variables allows control over product stoichiometry and crystal structure. This paper reviews the application of NHSG chemistry to the synthesis of negative thermal expansion oxides and selected metal sulfides.

Surface and catalytic properties of acid metal carbons prepared by the sol gel method

NASA Astrophysics Data System (ADS)

Aguado-Serrano, J.; Rojas-Cervantes, M. L.; Martín-Aranda, R. M.; López-Peinado, A. J.; Gómez-Serrano, V.

2006-06-01

The sol-gel method has been applied for the synthesis of a series of acid metal-carbon xerogels (with M = V, Cr, Mo and Ni) by polymerisation of resorcinol with formaldehyde in the presence of metallic precursors. A blank sample was also prepared without any metal addition. The xerogels were heated in nitrogen at 1000 °C to obtain the pyrolysed products. The samples were characterised by different techniques such as thermal-mass spectrometry analysis, gas physisorption, and mercury porosimetry. In addition, the acid character of the pyrolysed products was tested by the Claisen-Schmidt condensation between benzaldehyde and acetophenone for the formation of chalcones.

Sol-gel syntheses of pentaborate β-LaB5O9 and the photoluminescence by doping with Eu3+, Tb3+, Ce3+, Sm3+, and Dy3+

NASA Astrophysics Data System (ADS)

Yang, Ruirui; Sun, Xiaorui; Jiang, Pengfei; Gao, Wenliang; Cong, Rihong; Yang, Tao

2018-02-01

Rare earth (RE) borates have been extensively studied as good photoluminescent materials, however, the target hosts were limited to "RE3BO6", REBO3, and REB3O6 in the RE2O3-B2O3 phase diagram until the recent discovery of rare earth pentaborate. For the first time, the sol-gel method was employed to synthesize β-LaB5O9 doped with Eu3+, Tb3+, Ce3+, Sm3+, Dy3+. In comparison to the previous synthetic methods, the sol-gel method possesses superiorities including easily-controllable doping concentration, high yield and emission efficiency. Solid solutions of phosphors were prepared and carefully analyzed by powder X-ray diffraction. Concentration quenching or saturation was observed in Eu3+, Tb3+ and Ce3+ doped phosphors at round 10 at%. Eu3+, Tb3+, Sm3+, and Dy3+ emit red, green, orange, and close-to-white light, respectively. The absolute emission efficiency of Ce3+ is high and in the UV range, suggesting the function of being sensitizer once combined with other activators.

Tertiary-amine-containing thermo- and pH-sensitive hydrophilic ABA triblock copolymers: effect of different tertiary amines on thermally induced sol-gel transitions.

PubMed

Henn, Daniel M; Wright, Roger A E; Woodcock, Jeremiah W; Hu, Bin; Zhao, Bin

2014-03-11

This Article reports on the synthesis of a series of well-defined, tertiary-amine-containing ABA triblock copolymers, composed of a poly(ethylene oxide) (PEO) central block and thermo- and pH-sensitive outer blocks, and the study of the effect of different tertiary amines on thermally induced sol-gel transition temperatures (T(sol-gel)) of their 10 wt % aqueous solutions. The doubly responsive ABA triblock copolymers were prepared from a difunctional PEO macroinitiator by atom transfer radical polymerization of methoxydi(ethylene glycol) methacrylate and ethoxydi(ethylene glycol) methacrylate at a feed molar ratio of 30:70 with ∼5 mol % of either N,N-diethylaminoethyl methacrylate (DEAEMA), N,N-diisopropylaminoethyl methacrylate, or N,N-di(n-butyl)aminoethyl methacrylate. The chain lengths of thermosensitive outer blocks and the molar contents of tertiary amines were very similar for all copolymers. Using rheological measurements, we determined the pH dependences of T(sol-gel) of 10 wt % aqueous solutions of these copolymers in a phosphate buffer. The T(sol-gel) versus pH curves of all polymers exhibited a sigmoidal shape. The T(sol-gel) increased with decreasing pH; the changes were small on both high and low pH sides. At a specific pH, the T(sol-gel) decreased with increasing the hydrophobicity of the tertiary amine, and upon decreasing pH the onset pH value for the T(sol-gel) to begin to increase noticeably was lower for the more hydrophobic tertiary amine-containing copolymer. In addition, we studied the effect of different tertiary amines on the release behavior of FITC-dextran from 10 wt % micellar gels in an acidic medium at 37 and 27 °C. The release profiles for three studied hydrogels at 37 °C were essentially the same, suggesting that the release was dominated by the diffusion of FITC-dextran. At 27 °C, the release was significantly faster for the DEAEMA-containing copolymer, indicating that both diffusion and gel dissolution contributed to the release at this temperature.

Zr doping dependence of structural and magnetic properties of cobalt ferrite synthesized by sol-gel based Pechini method

NASA Astrophysics Data System (ADS)

Motavallian, Pourya; Abasht, Behzad; Abdollah-Pour, Hassan

2018-04-01

Nanocrystalline CoZrxFe2-xO4 (0 ≤ x ≤ 0.3 in a step of 0.05) powders were synthesized by Pechini sol-gel method. The dry gel was grinded and calcined at 700 °C in a static air atmosphere for 1 h. Some tests such as thermo gravimetric analysis (TGA) combined with differential analysis (DTA), fourier transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), field emission scanning electron microscopy (FE-SEM) and vibrating sample magnetometer (VSM) were carried out to investigate the thermal behaviour, structural bonds identification, crystallographic properties, morphology and magnetic properties of the obtained powders. X-ray diffraction revealed a single-phase cubic spinel structure for all samples, where the crystallite size decreases; the lattice parameter simultaneously increases with substitution of Zr. The results of FE-SEM showed that the particle size is in the 20-70 nm range. The magnetic properties such as saturation magnetization (Ms), remanent magnetization (Mr) and coercivity (Hc) were measured from the hysteresis loops. The greatest amount of saturation magnetization for CoZr0.05Fe1.95O4 sample was 67.9 emu·g-1.

Study of the Kinetics and Equilibrium of the Adsorption of Oils onto Hydrophobic Jute Fiber Modified via the Sol-Gel Method.

PubMed

Lv, Na; Wang, Xiaoli; Peng, Shitao; Zhang, Huaqin; Luo, Lei

2018-05-12

A new kind of hydrophobic and oil sorbent based on jute fiber was successfully prepared by the integration of silica onto a fiber surface via the sol-gel method and subsequent hydrophobic modification with octadecyltrichlorosilane (OTS). Compared with the hydrophilic raw fiber, the modified fiber had a water contact angle (CA) of 136.2°, suggesting that the material has good hydrophobicity. Furthermore, the ability of oil in the oil/water system (taking diesel for example) to absorb was revealed by the kinetics, the isotherm equation, and the thermodynamic parameters. Adsorption behavior was kinetically investigated using pseudo first-order and pseudo second-order models. The data mostly correlated with the pseudo first-order model. The equilibrium adsorption at 298 K was assessed by using the Langmuir and Freundlich isotherm models. The Freundlich model had greater consistency with the experimental data. The obtained thermodynamic parameters demonstrate that the adsorption of diesel is spontaneous, favorable, and exothermic.

Plasmon mediated cathodic photocurrent generation in sol-gel synthesized doped SrTiO{sub 3} nanofilms

DOE Office of Scientific and Technical Information (OSTI.GOV)

Sugavaneshwar, Ramu Pasupathi, E-mail: r.p.sugavaneshwar@nims.go.jp, E-mail: NAGAO.Tadaaki@nims.go.jp; Chen, Kai; Lakshminarayana, Gandham

2015-11-01

Thin films of SrTiO{sub 3} (STO) and Rh-doped SrTiO{sub 3} (Rh-STO) were synthesized by sol-gel method and loaded with Ag nanoparticles. Pristine STO films exhibited anodic photocurrent while Rh-STO exhibited cathodic photocurrent. An enhancement in the overall cathodic photocurrent is observed with Ag nanoparticle loading and an additional enhancement in the visible light range is seen from the incident photon-to-current efficiency spectrum due to synergetic effect of Rh doping and Ag loading in STO.

Sol-gel-derived double-layered nanocrystal memory

NASA Astrophysics Data System (ADS)

Ko, Fu-Hsiang; You, Hsin-Chiang; Lei, Tan-Fu

2006-12-01

The authors have used the sol-gel spin-coating method to fabricate a coexisting hafnium silicate and zirconium silicate double-layered nanocrystal (NC) memories. From transmission electron microscopic and x-ray photoelectron spectroscopic analyses, the authors determined that the hafnium silicate and zirconium silicate NCs formed after annealing at 900°C for 1min. When using channel hot electron injection for charging and band-to-band tunneling-induced hot hole injection for discharging, the NC memories exhibited superior Vth shifting because of the higher probability for trapping the charge carrier.

Eu-doped BaTiO₃powder and film from sol-gel process with polyvinylpyrrolidone additive.

PubMed

García-Hernández, Margarita; García-Murillo, Antonieta; de J Carrillo-Romo, Felipe; Jaramillo-Vigueras, David; Chadeyron, Geneviève; De la Rosa, Elder; Boyer, Damien

2009-09-17

Transparent BaTiO(3):Eu(3+) films were prepared via a sol-gel method and dip-coating technique, using barium acetate, titanium butoxide, and polyvinylpyrrolidone (PVP) as modifier viscosity. BaTiO(3):Eu(3+) films ~500 nm thick, crystallized after thermal treatment at 700 masculineC. The powders revealed spherical and rod shape morphology. The optical quality of films showed a predominant band at 615 nm under 250 nm excitation. A preliminary luminescent test provided the properties of the Eu(3+) doped BaTiO(3).

Fabrication of transparent ceramics using nanoparticles

DOEpatents

Cherepy, Nerine J; Tillotson, Thomas M; Kuntz, Joshua D; Payne, Stephen A

2012-09-18

A method of fabrication of a transparent ceramic using nanoparticles synthesized via organic acid complexation-combustion includes providing metal salts, dissolving said metal salts to produce an aqueous salt solution, adding an organic chelating agent to produce a complexed-metal sol, heating said complexed-metal sol to produce a gel, drying said gel to produce a powder, combusting said powder to produce nano-particles, calcining said nano-particles to produce oxide nano-particles, forming said oxide nano-particles into a green body, and sintering said green body to produce the transparent ceramic.

Well-aligned Vertically Oriented ZnO Nanorod Arrays and their Application in Inverted Small Molecule Solar Cells.

PubMed

Lin, Ming-Yi; Wu, Shang-Hsuan; Hsiao, Li-Jen; Budiawan, Widhya; Chen, Shih-Lun; Tu, Wei-Chen; Lee, Chia-Yen; Chang, Yia-Chung; Chu, Chih-Wei

2018-04-25

This manuscript describes how to design and fabricate efficient inverted solar cells, which are based on a two-dimensional conjugated small molecule (SMPV1) and [6,6]-phenyl-C71-butyric acid methyl ester (PC71BM), by utilizing ZnO nanorods (NRs) grown on a high quality Al-doped ZnO (AZO) seed layer. The inverted SMPV1:PC71BM solar cells with ZnO NRs that grew on both a sputtered and sol-gel processed AZO seed layer are fabricated. Compared with the AZO thin film prepared by the sol-gel method, the sputtered AZO thin film exhibits better crystallization and lower surface roughness, according to X-ray diffraction (XRD) and atomic force microscope (AFM) measurements. The orientation of the ZnO NRs grown on a sputtered AZO seed layer shows better vertical alignment, which is beneficial for the deposition of the subsequent active layer, forming better surface morphologies. Generally, the surface morphology of the active layer mainly dominates the fill factor (FF) of the devices. Consequently, the well-aligned ZnO NRs can be used to improve the carrier collection of the active layer and to increase the FF of the solar cells. Moreover, as an anti-reflection structure, it can also be utilized to enhance the light harvesting of the absorption layer, with the power conversion efficiency (PCE) of solar cells reaching 6.01%, higher than the sol-gel based solar cells with an efficiency of 4.74%.

Self-organized micro-holes on titania based sol-gel films under continuous direct writing with a continuous wave ultraviolet laser

DOE Office of Scientific and Technical Information (OSTI.GOV)

Bakhti, S.; Destouches, N.; Gamet, E.

The microstructuring of titania based sol-gel films is investigated by direct writing with a continuous wave ultraviolet laser beam emitting at 244 nm. Depending on the exposure conditions, the films exhibit a volume expansion, a volume shrinkage, a self-shaped delamination, or are damaged. This paper is mainly focused on the regime where spontaneous local delamination occurs, which corresponds to a narrow range of laser irradiances and writing speeds. In this regime, self-organized round-shape micro-holes opened on the substrate are generated.

Investigation of the surface morphology of biocompatible chitosan-based hydrogels and xerogels

NASA Astrophysics Data System (ADS)

Zhuravleva, Yulia Yu.; Malinkina, Olga N.; Shipovskaya, Anna B.

2018-04-01

Our biocompatible hydrogel systems obtained by the sol-gel technqiue and based on chitosan and silicon polyolates are promising for medical and biological applications. The surface microrelief of these sol-gel materials (hydrogels and xerogels) based on chitosan and silicon tetraglycerolate was explored by AFM and SEM. A significant influence of the component ratio in the mixed system on the morphology and surface profile of the hydrogels and xerogels prepared therefrom was established. An increased content of the structure-forming component (chitosan) in the system was shown to increase the roughness scale of the hydrogel surface and to promote the porosity of the xerogel structure.

A simple and rapid method for direct determination of Al(III) based on the enhanced resonance Rayleigh scattering of hemin-functionalized graphene-Al(III) system

NASA Astrophysics Data System (ADS)

Ling, Yu; Chen, Ling Xiao; Dong, Jiang Xue; Li, Nian Bing; Luo, Hong Qun

2016-03-01

A novel method for direct determination of Al(III) by using hemin-functionalized graphene (H-GO) has been established based on the enhancement of resonance Rayleigh scattering (RRS) intensity. The characteristics of RRS spectra, the optimum reaction conditions, and the reaction mechanism have been investigated. In this experiment, the Al(III) would exist in sol-gel Al(OH)3 species under the condition of pH 5.9 in aqueous solutions. When H-GO existed in the solution, the sol-gel Al(OH)3 would react with H-GO and result in enhancement of RRS intensity, owing to the enhanced hydrophobicity of H-GO surface. Therefore, a simple and rapid sensor for Al(III) was developed. The increased intensity of RRS is directly proportional to the concentration of Al(III) in the range of 10 nM-6 μM, along with a detection limit of 0.87 nM. Moreover, the sensor has been applied to determination of Al(III) concentration in real water and aspirin tablet samples with satisfactory results. Therefore, the proposed method is promising as an effective means for selective and sensitive determination of Al(III).

Production of monodisperse cerium oxide microspheres with diameters near 100 µm by internal-gelation sol–gel methods

DOE Office of Scientific and Technical Information (OSTI.GOV)

Katalenich, Jeffrey A.; Kitchen, Brian B.; Pierson, Bruce D.

Cerium dioxide microspheres with uniform diameters between 65 – 211 µm were fabricated using internal gelation sol-gel methods. Although uniform microspheres are produced for nuclear fuel applications with diameters above 300 µm, sol-gel microspheres with diameters of 50 - 200 µm have historically been made by emulsion techniques and had poor size uniformity [1, 2]. An internal gelation, sol-gel apparatus was designed and constructed to accommodate the production of small, uniform microspheres whereby cerium-containing solutions were dispersed into flowing silicone oil and heated in a gelation column to initiate solidification [3, 4]. Problems with premature feed gelation and microsphere coalescencemore » were overcome by equipment modifications unique among known internal gelation setups. Microspheres were fabricated and sized in batches as a function of dispersing needle diameter and silicone oil flow rate in the two-fluid nozzle in order to determine the range of sizes possible and corresponding degree of monodispersity. Initial experiments with poor size uniformity were linked to microsphere coalescence in the gelation column prior to solidification as well as excessive flow rates for the cerium feed solution. Average diameter standard deviations as low as 2.23% were observed after optimization of flow rates and minimization of coalescence reactions.« less

Thickening compositions containing xanthomonas gum and hydroxyalkyl ether of guar gum

DOE Office of Scientific and Technical Information (OSTI.GOV)

Jordan, W.A.

1973-07-24

Natural and synthetic gums have been used as thickeners for foods, coatings, paints, dyes, explosive slurries, oil-well fluids, and many other applications. Thickening compositions are described which consist of xanthomonas gum and hydroxyalkyl ether of guar gum and are suitable for use in explosive slurries. Aqueous sols of xanthomonas gum are plastic in nature and exhibit higher gel strengths than sols of other gums. Aqueous sols of hydroxyalkyl ether of guar are almost Newtonian and exhibit little or no gel strength. Aqueous sols of the thickening compositions of the present invention are plastic in character. At certain concentrations of themore » thickening compositions in aqueous sols, the sols have higher gel strengths than can be obtained from xanthomonas gum alone. At certain concentrations, the aqueous sols containing the thickening compositions exhibit greater viscosity differentials than do sols containing xanthomonas gum alone. In addition, the aqueous sols exhibit a greater drop in viscosity as the thickening composition concentration is reduced than do aqueous sols of xanthomonas gum alone.(5 claims)« less

Reversible sol-to-gel transformation of uracil gelators: specific colorimetric and fluorimetric sensor for fluoride ions.

PubMed

Xing, Ling-Bao; Yang, Bing; Wang, Xiao-Jun; Wang, Jiu-Ju; Chen, Bin; Wu, Qianhong; Peng, Hui-Xing; Zhang, Li-Ping; Tung, Chen-Ho; Wu, Li-Zhu

2013-03-05

A new type of anthracene organogelator based on uracil was obtained using organic aromatic solvents, cyclohexane, DMSO, ethanol, and ethyl acetate. It was further characterized by field-emission scanning electron microscopy and transmission electron microscopy. Specifically, the resulting organogels were demonstrated to be promising colorimetric and fluorescent sensors toward fluoride ions with high sensitivity and selectivity, accompanying the disruption of the gelators. Spectroscopic study and (1)H NMR titration experiment revealed that the deprotonation of the hydrogen atom on the N position of uracil moiety by fluoride ions is responsible for the recognition events, evidenced by immediate transformation from the sol phase to the gel state upon adding a small amount of a proton solvent, methanol. The process is reversible, with zero loss in sensing activity and sol-to-gel transformation ability even after five runs.

Sol-gel synthesis, phase composition, morphological and structural characterization of Ca10(PO4)6(OH)2: XRD, FTIR, SEM, 3D SEM and solid-state NMR studies

NASA Astrophysics Data System (ADS)

Kareiva, Simonas; Klimavicius, Vytautas; Momot, Aleksandr; Kausteklis, Jonas; Prichodko, Aleksandra; Dagys, Laurynas; Ivanauskas, Feliksas; Sakirzanovas, Simas; Balevicius, Vytautas; Kareiva, Aivaras

2016-09-01

Aqueous sol-gel chemistry route based on ammonium-hydrogen phosphate as the phosphorus precursor, calcium acetate monohydrate as source of calcium ions, and 1,2-ethylendiaminetetraacetic acid (EDTA), or 1,2-diaminocyclohexanetetracetic acid (DCTA), or tartaric acid (TA), or ethylene glycol (EG), or glycerol (GL) as complexing agents have been used to prepare calcium hydroxyapatite (Ca10(PO4)6(OH)2, CHAp). The phase transformations, composition, and structural changes in the polycrystalline samples were studied by infrared spectroscopy (FTIR), X-ray powder diffraction analysis (XRD), and scanning electron microscopy (SEM). The local short-range (nano- and mezo-) scale effects in CHAp were studied using solid-state NMR spectroscopy. The spatial 3D data from the SEM images of CHAp samples obtained by TA, EG and GL sol-gel routes were recovered for the first time to our knowledge.

Chemical sensing of copper phthalocyanine sol-gel glass through organic vapors

DOE Office of Scientific and Technical Information (OSTI.GOV)

Ridhi, R.; Gawri, Isha; Abbas, Saeed J.

2015-05-15

The sensitivities of metallophthalocyanine to vapor phase electron donors has gained significance in many areas and disciplines due to their sensing properties and ease of operation. In the present study the interaction mechanism of organic vapors in Copper Phthalocyanine (CuPc) sol-gel glass has been studied. The interaction mechanism is affected by many factors like morphology, electrical or optical properties of film. CuPc sol-gel glass has been synthesized using chemical route sol-gel method. Its structural characterization was conducted using XRD and the amorphous nature of the silicate glass was observed with characteristic α polymorph phase of CuPc at around 6.64° withmore » 13.30Å interplanar spacing. The size of the particle as determined using Debbye Scherre’s formula comes out around 15.5 nm. The presence of α phase of CuPc was confirmed using FTIR with the appearance of crystal parameter marker band at 787 cm-1. Apart from this A2u and Eu symmetry bands of CuPc have also been observed. The UV absorption spectrum of CuPc exhibits absorption peaks owing to π→ π* and n→ π* transitions. A blue shift in the prepared CuPc glass has been observed as compared to the dopant CuPc salt indicating increase of band gap. A split in B (Soret) band and Q band appears as observed with the help of Lorentzian fitting. CuPc sol gel glass has been exposed with chemical vapors of Methanol, Benzene and Bromine individually and the electrical measurements have been carried out. These measurements show the variation in conductivity and the interaction mechanism has been analyzed.« less

Fabrication of mesoporous silica nanoparticles by sol gel method followed various hydrothermal temperature

NASA Astrophysics Data System (ADS)

Purwaningsih, Hariyati; Pratiwi, Vania Mitha; Purwana, Siti Annisa Bani; Nurdiansyah, Haniffudin; Rahmawati, Yenny; Susanti, Diah

2018-04-01

Rice husk is an agricultural waste that is potentially used as natural silica resources. Natural silica claimed to be safe in handling, cheap and can be generate from cheap resource. In this study mesoporous silica was synthesized using sodium silicate extracted from rice husk ash. This research's aim are to study the optimization of silica extraction from rice husk, characterizing mesoporous silica from sol-gel method and surfactant templating from rice husk and the effect of hydrothermal temperature on mesoporous silica nanoparticle (MSNp) formation. In this research, rice husk was extracted with sol-gel method and was followed by hydrothermal treatment; several of hydrothermal temperatures were 85°C, 100°C, 115°C, 130°C and 145° for 24 hours. X-ray diffraction analysis was identified of α-SiO2 phase and NaCl compound impurities. Scherer's analysis method for crystallite size have resulted 6.27-40.3 nm. FTIR results of silica from extraction and MSNp indicated Si-O-Si bonds on the sample. SEM result showed the morphology of the sample that has spherical shape and smooth surface. TEM result showed particle size ranged between 69,69-84,42 nm. BET showed that the pore size classified as mesoporous with pore diameter size is 19,29 nm.

Functional materials based on nanocrystalline cellulose

NASA Astrophysics Data System (ADS)

Surov, O. V.; Voronova, M. I.; Zakharov, A. G.

2017-10-01

The data on the synthesis of functional materials based on nanocrystalline cellulose (NCC) published over the past 10 years are analyzed. The liquid-crystal properties of NCC suspensions, methods of investigation of NCC suspensions and films, conditions for preserving chiral nematic structure in the NCC films after removal of the solvent and features of templated sol-gel synthesis of functional materials based on NCC are considered. The bibliography includes 106 references.

Surface modification of wood by alkoxysilane sol-gel deposition to create anti-mold and anti-fungal characteristics

Treesearch

Mandla A. Tshabalala; Vina Yang; Ryan Libert

2009-01-01

Hybrid inorganic/organic thin films deposited on wood substrates have been shown to lower the rate of moisture sorption of the wood. Deposition of such thin films can be accomplished by sol–gel deposition or by plasma-enhanced chemical vapor deposition. This paper describes in situ sol–gel deposition of hybrid inorganic/organic thin films on wood substrates using...

Spatiotemporal control of synergistic gel disintegration consisting of boroxole- and glyco-based polymers via photoinduced proton transfer.

PubMed

Kotsuchibashi, Yohei; Ebara, Mitsuhiro; Sato, Takeshi; Wang, Yinan; Rajender, Rajender; Hall, Dennis G; Narain, Ravin; Aoyagi, Takao

2015-02-12

We demonstrate here a local- and remote-control of gel disintegration by using photoinduced proton transfer chemistry of photoacid generator (PAG). The gels were prepared by simply mixing two polymers, poly(N-isopropylacrylamide-co-5-methacrylamido-1,2-benzoxaborole) (P(NIPAAm-co-MAAmBO)) and poly(3-gluconamidopropyl methacrylamide) (PGAPMA) via the synergistic interaction of benzoxaborole and diol groups. The o-nitrobenzaldehyde (o-NBA) was then loaded into the gel as a PAG. The benzoxaborole-diol interaction was successfully disintegrated upon UV irradiation due to the local pH decrease inside the gel. When the gel was irradiated to a specific gel region, the synergistic interactions were disintegrated only at the exposed region. Of special interest is that the whole material eventually transitioned from gel to sol state, as the generated protons diffused gradually toward the nonilluminated region. The ability of the proposed gel-sol transition system via photoinduced proton diffusion may be beneficial for not only prompt pH changes within the gel but also the design of predictive and programmable devices for drug delivery.

Adjustable rheology of fumed silica dispersion in urethane prepolymers: Composition-dependent sol and gel behaviors and energy-mediated shear responses

DOE Office of Scientific and Technical Information (OSTI.GOV)

Zheng, Zhong, E-mail: 11329038@zju.edu.cn; Song, Yihu, E-mail: s-yh0411@zju.edu.cn; Wang, Xiang, E-mail: 11229036@zju.edu.cn

2015-07-15

Variation of colloidal and interfacial interactions leads to a microstructural diversity in fumed silica dispersions exhibiting absolutely different sol- or gel-like rheological responses. In this study, fumed silicas with different surface areas (200–400 m{sup 2}/g) and surface characteristics (hydrophilic or hydrophobic) are dispersed into moisture-cured polyurethane. The microstructures investigated using transmission electron microscope are associated perfectly with three different rheological behaviors: (i) Sols with well-dispersed silica aggregates, (ii) weak gels with agglomerate-linked networks, and (iii) strong gels with concentrated networks of large agglomerates. Though sols and gels are well distinguished by shear thickening or sustained thinning response through steady shearmore » flow test, it is interesting that the sols and weak gels exhibit a uniform modulus plateau-softening-hardening-softening response with increasing dynamic strain at frequency 10 rad s{sup −1} while the strong gels show a sustained softening beyond the linear regime. Furthermore, the onset of softening and hardening can be normalized: The two softening are isoenergetic at mechanical energies of 0.3 J m{sup −3} and 10 kJ m{sup −3}. On the other hand, the hardening is initiated by a critical strain of 60%. The mechanisms involved in the generation of the sol- and the gel-like dispersions and their structural evolutions during shear are thoroughly clarified in relation to the polyols, the characteristic and content of silica and the curing catalysts.« less

Modified silica sol coatings for surface enhancement of leather.

PubMed

Mahltig, Boris; Vossebein, Lutz; Ehrmann, Andrea; Cheval, Nicolas; Fahmi, Amir

2012-06-01

The presented study reports on differently modified silica sols for coating applications on leather. Silica sols are prepared by acidic hydrolysis of tetraethoxysilane and modified by silane compounds with fluorinated and non-fluorinated alkylgroups. In contrast to many earlier investigations regarding sol-gel applications on leather, no acrylic resin is used together with the silica sols when applying on leather. The modified silica particles are supposed to aggregate after application, forming thus a modified silica coating on the leather substrate. Scanning electron microscopy investigation shows that the applied silica coatings do not fill up or close the pores of the leather substrate. However, even if the pores of the leather are not sealed by this sol-gel coating, an improvement of the water repellent and oil repellent properties of the leather substrates are observed. These improved properties of leather by application of modified silica sols can provide the opportunity to develop sol-gel products for leather materials present in daily life.

Photo-Definable Self Assembled Maerials

DOEpatents

DOSHI, DHAVAL; [et al

2004-10-26

The present invention provides a mesoporous material comprising at least one region of mesoporous material patterned at a lithographic scale. The present invention also provides a a method for forming a patterned mesoporous material comprising: coating a sol on a substrate to form a film, the sol comprising: a templating molecule, a photoactivator generator, a material capable of being sol-gel processed, water, and a solvent; and exposing the film to light to form a patterned mesoporous material.

Poly(aniline) nanowires in sol-gel coated ITO: A pH-responsive substrate for planar supported lipid bilayers

PubMed Central

Ge, Chenhao; Orosz, Kristina S.; Armstrong, Neal R.; Saavedra, S. Scott

2011-01-01

Facilitated ion transport across an artificial lipid bilayer coupled to a solid substrate is a function common to several types of bioelectronic devices based on supported membranes, including biomimetic fuel cells and ion channel biosensors. Described here is fabrication of a pH-sensitive transducer composed of a porous sol-gel layer derivatized with poly(aniline) (PANI) nanowires grown from an underlying planar indium-tin oxide (ITO) electrode. The upper sol-gel surface is hydrophilic, smooth, and compatible with deposition of a planar supported lipid bilayer (PSLB) formed via vesicle fusion. Conducting tip AFM was used to show that the PANI wires are connected to the ITO, which convert this electrode into a potentiometric pH sensor. The response to changes in the pH of the buffer contacting the PANI nanowire/sol-gel/ITO electrode is blocked by the very low ion permeability of the overlying, fluid PSLB. The feasibility of using this assembly to monitor facilitated proton transport across the PSLB was demonstrated by doping the membrane with lipophilic ionophores that respond to a transmembrane pH gradient, which produced an apparent proton permeability several orders of magnitude greater than values measured for undoped lipid bilayers. PMID:21707069

Amperometric detector for gas chromatography based on a silica sol-gel solid electrolyte.

PubMed

Steinecker, William H; Miecznikowski, Krzysztof; Kulesza, Pawel J; Sandlin, Zechariah D; Cox, James A

2017-11-01

An electrochemical cell comprising a silica sol-gel solid electrolyte, a working electrode that protrudes into a gas phase, and reference and counter electrodes that contact the solid electrolyte comprises an amperometric detector for gas chromatography. Under potentiostatic conditions, a current related to the concentration of an analyte in the gas phase is produced by its oxidation at the three-phase boundary among the sol-gel, working electrode, and the gas phase. The sol-gel is processed to contain an electrolyte that also serves as a humidistat to maintain a constant water activity even in the presence the gas chromatographic mobile phase. Response was demonstrated toward a diverse set of analytes, namely hydrogen, 1,2-ethandithiol, phenol, p-cresol, and thioanisole. Using flow injection amperometry of hydrogen with He as the carrier gas, 90% of the steady-state current was achieved in < 1s at a flow rate of 20mLmin -1 . A separation of 1,2-ethandithiol, phenol, p-cresol, and thioanisole at a 2.2mLmin -1 flow rate was achieved with respective detection limits (k = 3 criterion) of 4, 1, 3, and 70 ppmv when the working electrode potential was 800mV. Copyright © 2017 Elsevier B.V. All rights reserved.

Surface and biological evaluation of hydroxyapatite-based coatings on titanium deposited by different techniques.

PubMed

Massaro, C; Baker, M A; Cosentino, F; Ramires, P A; Klose, S; Milella, E

2001-01-01

Hydroxyapatite coatings have been deposited on titanium cp by plasma spray, sol-gel, and sputtering techniques for dental implant applications. The latter two techniques are of current interest, as they allow coatings of micrometer dimensions to be deposited. Coating morphology, composition, and structure have been investigated by scanning electron microscopy (SEM), X-ray photoelectron spectroscopy (XPS) and X-ray diffraction (XRD). All coatings were homogeneous and exhibited a rough morphology suitable for implant applications. The sputtered (after annealing), plasma spray, and sol-gel coatings all showed diffraction peaks corresponding to hydroxyapatite. The surface contaminants were observed to be different for the different coating types. The sputtered coatings were found to have a composition most similar to hydroxyapatite; the sol-gel deposits also showed a high concentration of hydroxyl ions. A discrepancy in the Ca/P ratio was observed for the plasma spray coatings, and a small concentration of carbonate ions was found in the sputter-deposited coatings. The in vitro cell-culture studies using MG63 osteoblast-like cells demonstrated the ability of cells to proliferate on the materials tested. The sol-gel coating promotes higher cell growth, greater alkaline phosphatase activity, and greater osteocalcin production compared to the sputtered and plasma-sprayed coatings. Copyright 2001 John Wiley & Sons, Inc.

Application of surface analytical methods in thin film analysis

NASA Astrophysics Data System (ADS)

Wen, Xingu

Self-assembly and the sol-gel process are two promising methods for the preparation of novel materials and thin films. In this research, these two methods were utilized to prepare two types of thin films: self-assembled monolayers of peptides on gold and SiO2 sol-gel thin films modified with Ru(II) complexes. The properties of the resulting thin films were investigated by several analytical techniques in order to explore their potential applications in biomaterials, chemical sensors, nonlinear optics and catalysis. Among the analytical techniques employed in the study, surface analytical techniques, such as X-ray photoelectron spectroscopy (XPS) and grazing angle reflection absorption Fourier transform infrared spectroscopy (RA-FTIR), are particularly useful in providing information regarding the compositions and structures of the thin films. In the preparation of peptide thin films, monodisperse peptides were self-assembled on gold substrate via the N-terminus-coupled lipoic acid. The film compositions were investigated by XPS and agreed well with the theoretical values. XPS results also revealed that the surface coverage of the self-assembled films was significantly larger than that of the physisorbed films and that the chemisorption between the peptides and gold surface was stable in solvent. Studies by angle dependent XPS (ADXPS) and grazing angle RA-FTIR indicated that the peptides were on average oriented at a small angle from the surface normal. By using a model of orientation distribution function, both the peptide tilt angle and film thickness can be well calculated. Ru(II) complex doped SiO2 sol-gel thin films were prepared by low temperature sol-gel process. The ability of XPS coupled with Ar + ion sputtering to provide both chemical and compositional depth profile information of these sol-gel films was evaluated. This technique, together with UV-VIS and electrochemical measurements, was used to investigate the stability of Ru complexes in the composite films. The stability of Ru complexes with respect to dopant leaching was dependent on the film microstructures. Three methods aiming to improve the dopant stability were also explored. In addition, the ion exchange properties of the composite films, upon exposure to various ions in aqueous solutions, were investigated by XPS, and the ion exchange mechanism was elucidated.

Study on fabrication of the superhydrophobic sol-gel films based on copper wafer and its anti-corrosive properties

NASA Astrophysics Data System (ADS)

Fan, Youhua; Li, Changzhu; Chen, Zejun; Chen, Hong

2012-06-01

In the present study, superhydrophobic copper wafer was prepared by a sol-gel deposition method. Different molar ratios of vinyltrimethoxysilane (VTES), ethanol (EtOH), water (H2O) and ammonia water (NH3·OH) were involved in this research. The morphologies, chemical compositions and hydrophobicity of the films were analyzed by scanning electron microscopy (SEM), energy dispersive X-ray detector (EDX), Fourier transfer infrared spectrometer (FTIR) and water contact angle measurement (CA). It was shown by the surface morphological study that different structures, such as pyramid-shaped protrusions, nipple-shaped protrusions or ball-shaped silica particles, were distributed on the copper substrate. The films had a high water contact angle larger than 155.4°. The durability properties revealed that the films had a good superhydrophobicity deposited in 3.5 wt.% sodium chloride solution for up to 14 days.

Trimetallic oxide nanocomposites of transition metals titanium and vanadium by sol-gel technique: synthesis, characterization and electronic properties

NASA Astrophysics Data System (ADS)

Kumar, Amit; Mishra, Neeraj Kumar; Sachan, Komal; Ali, Md Asif; Soaham Gupta, Sachchidanand; Singh, Rajeev

2018-04-01

Novel titanium and vanadium based trimetallic oxide nanocomposites (TMONCs) have been synthesized using metal salts of titanium-vanadium along with three others metals viz. tin, aluminium and zinc as precursors by the sol-gel method. Aqueous ammonia and hydrazine hydrate were used as the reducing agents. The preparations of nanocomposites were monitored by observing the visual changes during each step of synthesis. The synthesized TMONCs were characterized using UV–vis, SEM, EDX, TEM and DLS. Band gap of the synthesized TMONCs ranges from 3–4.5 eV determined using tauc plot. FTIR study revealed the molecular stretching and bending peaks of corresponding M–O/M–O–M bonds thus confirming their formation. Molecular composition and particle size were determined using EDX and DLS respectively. Molecular shape, size and surface morphology have been examined by SEM and TEM.

Synthesis of Silver-Strontium Titanate Hybrid Nanoparticles by Sol-Gel-Hydrothermal Method.

PubMed

Ueno, Shintaro; Nakashima, Kouichi; Sakamoto, Yasunao; Wada, Satoshi

2015-03-24

Silver (Ag) nanoparticle-loaded strontium titanate (SrTiO₃) nanoparticles were attempted to be synthesized by a sol-gel-hydrothermal method. We prepared the titanium oxide precursor gels incorporated with Ag⁺ and Sr 2+ ions with various molar ratios, and they were successfully converted into the Ag-SrTiO₃ hybrid nanoparticles by the hydrothermal treatment at 230 °C in strontium hydroxide aqueous solutions. The morphology of the SrTiO₃ nanoparticles is dendritic in the presence and absence of Ag⁺ ions. The precursor gels, which act as the high reactive precursor, give rise to high nucleation and growth rates under the hydrothermal conditions, and the resultant diffusion-limited aggregation phenomena facilitate the dendritic growth of SrTiO₃. From the field-emission transmission electron microscope observation of these Ag-SrTiO₃ hybrid nanoparticles, the Ag nanoparticles with a size of a few tens of nanometers are distributed without severe agglomeration, owing to the competitive formation reactions of Ag and SrTiO₃.

In situ ZnO-PVA nanocomposite coated microfluidic chips for biosensing

NASA Astrophysics Data System (ADS)

Habouti, Salah; Kunstmann-Olsen, Casper; Hoyland, James D.; Rubahn, Horst-Günter; Es-Souni, Mohammed

2014-05-01

Microfluidic chips with integrated fluid and optical connectors have been generated via a simple PDMS master-mould technique. In situ coating using a Zinc oxide polyvinylalcohol based sol-gel method results in ultrathin nanocomposite layers on the fluid channels, which makes them strongly hydrophilic and minimizes auto contamination of the chips by injected fluorescent biomarkers.

Chemical Sensors Based on IR Spectroscopy and Surface-Modified Waveguides

NASA Technical Reports Server (NTRS)

Lopez, Gabriel P.; Niemczyk, Thomas

1999-01-01

Sol-gel processing techniques have been used to apply thin porous films to the surfaces of planar infrared (IR) waveguides to produce widely useful chemical sensors. The thin- film coating serves to diminish the concentration of water and increase the concentration of the analyte in the region probed by the evanescent IR wave. These porous films are composed of silica, and therefore, conventional silica surface modification techniques can be used to give the surface a specific functional character. The sol-gel film was surface-modified to make the film highly hydrophobic. These sensors were shown to be capable of detecting non-polar organic analytes, such as benzonitrile, in aqueous solution with detection limits in the ppb range. Further, these porous sol-gel structures allow the analytes to diffuse into and out of the films rapidly, thus reaching equilibrium in less than ten seconds. These sensors are unique because of the fact that their operation is based on the measurement of an IR absorption spectrum. Thus, these sensors are able to identify the analytes as well as measure concentration with high sensitivity. These developments have been documented in previous reports and publications. Recently, we have also targeted detection of the polar organic molecules acetone and isopropanol in aqueous solution. Polar organics are widely used in industrial and chemical processes, hence it is of interest to monitor their presence in effluents or decontamination process flows. Although large improvements in detection limits were expected with non-polar organic molecules in aqueous solutions using very hydrophobic porous sol-gel films on silicon attenuated total reflectance (Si ATR) waveguides, it was not as clear what the detection enhancements might be for polar organic molecules. This report describes the use of modified sol-gel-coated Si ATR sensors for trace detection and quantitation of small polar organic molecules in aqueous solutions. The detection of both acetone and isopropanol molecules in aqueous solution has been previously reported for chalcogenide fiber optic sensors. The sol-gel film was produced using a mixture of ethyltriethoxysilane and tetraethoxysilane and the surface modification was carried out using trimethylchlorosilane. We have demonstrated that this film concentrates the target polar analytes from aqueous solution in the region probed by the evanescent wave to improve detection limits by as much as a factor of 450.

Ultra-small dye-doped silica nanoparticles via modified sol-gel technique.

PubMed

Riccò, R; Nizzero, S; Penna, E; Meneghello, A; Cretaio, E; Enrichi, F

2018-01-01

In modern biosensing and imaging, fluorescence-based methods constitute the most diffused approach to achieve optimal detection of analytes, both in solution and on the single-particle level. Despite the huge progresses made in recent decades in the development of plasmonic biosensors and label-free sensing techniques, fluorescent molecules remain the most commonly used contrast agents to date for commercial imaging and detection methods. However, they exhibit low stability, can be difficult to functionalise, and often result in a low signal-to-noise ratio. Thus, embedding fluorescent probes into robust and bio-compatible materials, such as silica nanoparticles, can substantially enhance the detection limit and dramatically increase the sensitivity. In this work, ultra-small fluorescent silica nanoparticles (NPs) for optical biosensing applications were doped with a fluorescent dye, using simple water-based sol-gel approaches based on the classical Stöber procedure. By systematically modulating reaction parameters, controllable size tuning of particle diameters as low as 10 nm was achieved. Particles morphology and optical response were evaluated showing a possible single-molecule behaviour, without employing microemulsion methods to achieve similar results. Graphical abstractWe report a simple, cheap, reliable protocol for the synthesis and systematic tuning of ultra-small (< 10 nm) dye-doped luminescent silica nanoparticles.

Study of Wrinkle Resistant, Breathable, Anti-Uv Nanocoated Woven Polyester Fabric

NASA Astrophysics Data System (ADS)

Memon, Hafeezullah; Yasin, Sohail; Khoso, Nazakat Ali; Memon, Samiulah

2016-02-01

The multifunctional textiles are interesting areas to be researched on. In this paper, the effect of the fiber nanocoating on the wrinkle recovery, air permeability and anti-Ultraviolet (UV) property of different woven fabrics using sol-gel method has been studied. The sol-gel method has various advantages over other methods. Along with these properties, no change in visual appearance has also been discussed in this paper. The dispersion of nanoparticles of titanium was obtained into silica sol. The characterization of nanocoating was done using Field emission scanning electron micrograph (FESEM) and Fourier transform infrared spectroscopy (FTIR) studies. The fabric wrinkle recovery properties, air permeability and anti-UV performance were analyzed using three different immersion timings into the nanosol. The results revealed that both wrinkle recovery properties and anti-UV performance have increased with respect to immersing time of the nanocoating although a slight decrease in air permeability and whiteness index of the fabric was also observed.

Optical detection of parasitic protozoa in sol-gel matrices

NASA Astrophysics Data System (ADS)

Livage, Jacques; Barreau, J. Y.; Da Costa, J. M.; Desportes, I.

1994-10-01

Whole cell parasitic protozoa have been entrapped within sol-gel porous silica matrices. Stationary phase promastigote cells of Leishmania donovani infantum are mixed with a silica sol before gelation occurs. They remain trapped within the growing oxide network and their cellular organization appears to be well preserved. Moreover protozoa retain their antigenic properties in the porous gel. They are still able to detect parasite specific antibodies in serum samples from infected patients via an enzyme linked immunosorbent assay (ELISA). Antigen- antibody associations occurring in the gel are optically detected via the reactions of a peroxidase conjugate with ortho-phenylenediamine leading to the formation of a yellow coloration. A clear-cut difference in optical density is measured between positive and negative sera. Such an entrapment of antigenic species into porous sol-gel matrices avoids the main problems due to non specific binding and could be advantageously used in diagnostic kits.

Correlation of the oxidation state of cerium in sol-gel glasses as a function of thermal treatment via optical spectroscopy and XANES studies.

PubMed

Assefa, Zerihun; Haire, R G; Caulder, D L; Shuh, D K

2004-07-01

Sol-gel glass matrices containing lanthanides have numerous technological applications and their formation involves several chemical facets. In the case of cerium, its ability to exist in two different oxidation states or in mixed valence state provides additional complexities for the sol-gel process. The oxidation state of cerium present during different facets of preparation of sol-gel glasses, and also as a function of the starting oxidation state of cerium added, were studied both by optical spectroscopy and X-ray absorption near-edge structures (XANES). The findings acquired by each approach were compared. The primary focus was on the redox chemistries associated with sample preparation, gelation, and thermal treatment. When Ce3+ is introduced into the starting sols, the trivalent state normally prevails in the wet and room temperature-dried gels. Heating in air at >100 degrees C can generate a light yellow coloration with partial oxidation to the tetravalent state. Above 200 degrees C and up to approximately 1000 degrees C, cerium is oxidized to its tetravalent state. In contrast, when tetravalent cerium is introduced into the sol, both the wet and room temperature-dried gels lose the yellow-brown color of the initial ceric ammonium nitrate solution. When the sol-gel is heated to 110 degrees C it turns yellowish as the cerium tends to be re-oxidized. The yellow color is believed to represent the effect of oxidation and oligomerization of the cerium-silanol units in the matrix. The luminescence properties are also affected by these changes, the details of which are reported herein.

Ultra-high-stability, pH-resistant sol-gel titania poly(tetrahydrofuran) coating for capillary microextraction on-line coupled to high-performance liquid chromatography.

PubMed

Segro, Scott S; Cabezas, Yaniel; Malik, Abdul

2009-05-15

A sol-gel titania poly(tetrahydrofuran) (poly-THF) coating was developed for capillary microextraction hyphenated on-line with high-performance liquid chromatography (HPLC). Poly-THF was covalently bonded to the sol-gel titania network which, in turn, became chemically anchored to the inner surface of a 0.25mm I.D. fused silica capillary. For sample preconcentration, a 38-cm segment of the sol-gel titania poly-THF coated capillary was installed on an HPLC injection port as a sampling loop. Aqueous samples containing a variety of analytes were passed through the capillary and, during this process, the analytes were extracted by the sol-gel titania poly-THF coating on the inner surface of the capillary. Using isocratic and gradient elution with acetonitrile/water mobile phases, the extracted analytes were desorbed into the on-line coupled HPLC column for separation and UV detection. The sol-gel titania poly-THF coating was especially efficient in extracting polar analytes, such as underivatized phenols, alcohols, amines, and aromatic carboxylic acids. In addition, this coating was capable of extracting moderately polar and nonpolar analytes, such as ketones and polycyclic aromatic hydrocarbons. The sol-gel titania poly-THF coated capillary was also able to extract polypeptides at pH values near their respective isoelectric points. Extraction of these compounds can be important for environmental and biomedical applications. The observed extraction behavior can be attributed to the polar and nonpolar moieties in the poly-THF structure. This coating was found to be stable under extremely low and high pH conditions-even after 18h of exposure to 1M HCl (pH approximately 0.0) and 1M NaOH (pH approximately 14.0).

Percutaneous external fixator pins with bactericidal micron-thin sol-gel films for the prevention of pin tract infection.

PubMed

Qu, Haibo; Knabe, Christine; Radin, Shula; Garino, Jonathan; Ducheyne, Paul

2015-09-01

Risk of infection is considerable in open fractures, especially when fracture fixation devices are used to stabilize the fractured bones. Overall deep infection rates of 16.2% have been reported. The infection rate is even greater, up to 32.2%, with external fixation of femoral fractures. The use of percutaneous implants for certain clinical applications, such as percutaneous implants for external fracture fixation, still represents a challenge today. Currently, bone infections are very difficult to treat. Very potent antibiotics are needed, which creates the risk of irreversible damage to other organs, when the antibiotics are administered systemically. As such, controlled, local release is being pursued, but no such treatments are in clinical use. Herein, the use of bactericidal micron-thin sol-gel films on metallic fracture fixation pins is reported. The data demonstrates that triclosan (2,4,4'-trichloro-2'-hydroxydiphenylether), an antimicrobial agent, can be successfully incorporated into micron-thin sol-gel films deposited on percutaneous pins. The sol-gel films continuously release triclosan in vitro for durations exceeding 8 weeks (longest measured time point). The bactericidal effect of the micron-thin sol-gel films follows from both in vitro and in vivo studies. Inserting percutaneous pins in distal rabbit tibiae, there were no signs of infection around implants coated with a micron-thin sol-gel/triclosan film. Healing had progressed normally, bone tissue growth was normal and there was no epithelial downgrowth. This result was in contrast with the results in rabbits that received control, uncoated percutaneous pins, in which abundant signs of infection and epithelial downgrowth were observed. Thus, well-adherent, micron-thin sol-gel films laden with a bactericidal molecule successfully prevented pin tract infection. Copyright © 2015 Elsevier Ltd. All rights reserved.

Synthesis and Characterization of BaFe12O19 Thin Films Using Suspension of Nano Powders

NASA Astrophysics Data System (ADS)

Salemizadeh, Saman; Seyyed Ebrahimi, S. A.

BaM thin films have been synthesized by dispersing the dried gel nano powders prepared by Sol-Gel method. The solution was made by dissolving iron nitrate Fe(NO3).9H2O, barium nitrate Ba(NO3)2 and citric acid in deyonized water and methanol. This sol was slowly evaporated until a dried gel was formed. This dried gel was then added to ethylene glycol. The final solution was vigorously shaken and mixed in ultrasonic cleaner for 30 min to disperse particles sufficiently. Then the prepared solution spin coated on Si(110) substrate. The obtained thin films were dried at 120 °C and then calcined at 900 °C for 1 h. The films were characterized using X-ray diffraction (XRD) and vibrating sample magnetometer (VSM).

Anomalously large bend elastic constant and faster electro-optic response in anisotropic gels formed by a dipeptide

NASA Astrophysics Data System (ADS)

Bhargavi, R.; Nair, Geetha G.; Prasad, S. Krishna; Prabhu, Rashmi; Yelamaggad, C. V.

2011-04-01

We report rheological, static, and dynamic Freedericksz transformation measurements on an anisotropic thermoreversible gel formed by gelation of a nematic liquid crystal (NLC) with a monodisperse dipeptide. The storage and loss modulii obtained from a low strain oscillatory shear experiment display that the material forms a weak anisotropic gel, and undergoes a sharp thermal transition to an anisotropic sol state. Freedericksz transformation studies employing an electric field for the reorientation of the molecules present a surprising result: the gel possesses a very large Frank bend elastic constant value, which is orders of magnitude higher than that for the high temperature sol state as well as that for the neat NLC used. On the other hand, the splay elastic constant shows relatively a small increase. Further, these elastic constants show systematic but nonlinear variation with the concentration of the gelator. Attractive features of the electro-optic switching when the sol transforms to the gel state are the vanishing of the undesirable backflow effect, and nearly an order of magnitude decrease in the switching speed. In both the gel and sol states the extracted rotational viscosities are comparable to the values of the neat NLC at corresponding temperatures. In contrast, the bulk dynamic viscosity is more than three orders of magnitude higher in the gel. The studies also demonstrate that the anisotropic gel to anisotropic sol transition seen in this weak gel can be tracked by simply monitoring the static or the dynamic Freedericksz transformation.

Molecular interactions in high conductive gel electrolytes based on low molecular weight gelator.

PubMed

Bielejewski, Michał; Łapiński, Andrzej; Demchuk, Oleg

2017-03-15

Organic ionic gel (OIG) electrolytes, also known as gel electrolytes or ionogels are one example of modern functional materials with the potential to use in wide range of electrochemical applications. The functionality of OIGs arises from the thermally reversible solidification of electrolytes or ionic liquids and their superior ionic conductivity. To understand and to predict the properties of these systems it is important to get the knowledge about the interactions on molecular level between the solid gelator matrix and the electrolyte solution. This paper reports the spectroscopic studies (FT-IR, UV-Vis and Raman) of the gel electrolyte based on low molecular weight gelator methyl-4,6-O-(p-nitrobenzylidene)-α-d-glucopyranoside and solution of quaternary ammonium salt, tetramethylammonium bromide. The solidification process was based on sol-gel technique. Below characteristic temperature, defined as gel to sol phase transition temperature, T gs , the samples were solid-like and showed high conductivity values of the same order as observed for pure liquid electrolytes. The investigations were performed for a OIGs in a wide range of molar concentrations of the electrolyte solution. Copyright © 2016 Elsevier Inc. All rights reserved.

Dual controlled release, in situ gelling periodontal sol of metronidazole benzoate and serratiopeptidase: statistical optimization and mechanistic evaluation.

PubMed

Kumari, Neeraj; Pathak, Kamla

2012-01-01

In situ gelling syringeable periodontal sol capable of dual controlled delivery of metronidazole benzoate and serratiopeptidase was designed based on 2(3) factorial design with drug, poloxamer 407 and aerosil as independent variables and sol gel transition characteristics, %CDR(48h) and palatability as responses. The sols had agreeable taste, were mucoadhesive, syringeable and inverted into gels at periodontal cavity temperature. F8 with optimal drug release was identified as the best formulation. The dispersion characteristics of poloxamer significantly affected the pharmacotechnical properties of the in situ gelling systems. Extra design checkpoint generated using Design Expert software 8.02 (Stat-Ease, USA) validated the experimental design. Thus a thermoreversible, in situ gelling and syringeable periodontal sol with acceptable taste characteristics that offered controlled release of metronidazole benzoate and serratiopeptidase was developed for application into the periodontal pocket. The developed optimized sol was satisfactory in terms of taste, syringeability, palatability and incorporation of serratiopeptidase as anti-inflammatory agent, has the potential of developing a therapeutically efficacious system for treatment of periodontal inflammatory anaerobic infections.

Structural, optical, and electrical properties of Ni-doped ZnO nanorod arrays prepared via sonicated sol-gel immersion method

NASA Astrophysics Data System (ADS)

Ismail, A. S.; Mamat, M. H.; Malek, M. F.; Saidi, S. A.; Yusoff, M. M.; Mohamed, R.; Sin, N. D. Md; Suriani, A. B.; Rusop, M.

2018-05-01

Nickel (Ni)-doped zinc oxide (ZnO) nanorod array films were synthesised using sonicated sol-gel immersion method. The FESEM images showed that the Ni-doped ZnO nanorod arrays possess hexagonal shape with average diameter about 120 nm and thickness about 1.10 µm. The Ni-doped ZnO nanorod arrays possess better transmittance properties with 3.27 eV of optical band gap energy and 40 meV of urbach energy. The current-voltage (I-V) measurement indicated that the conductivity of ZnO film slightly improved with Ni-doping. The doped film displayed good humidity sensing performance with sensitivity of 1.21.

Nano sized La2Co2O6 double perovskite synthesized by sol gel method

NASA Astrophysics Data System (ADS)

Solanki, Neha; Lodhi, Pavitra Devi; Choudhary, K. K.; Kaurav, Netram

2018-05-01

We report here the synthesis of double perovskite La2Co2O6 (LCO) compound by a sol gel route method. The double perovskite structure of LCO system was confirmed via X-ray diffraction (XRD) analysis. Further, the lattice parameter, unit cell volume and bond length were refined by means of rietveld analysis using the full proof software. Debye Scherer formula was used to determine the particle size. The compound crystallized in triclinic structure with space group P-1 in ambient condition. We also obtained Raman modes from XRD spectra of poly-crystalline LCO sample. These results were interpreted for the observation of phonon excitations in this compound.

Structure and magnetic properties of Fe-doped ZnO prepared by the sol-gel method.

PubMed

Liu, Huilian; Yang, Jinghai; Zhang, Yongjun; Yang, Lili; Wei, Maobin; Ding, Xue

2009-04-08

Zn(0.97)Fe(0.03)O nanoparticles were synthesized by the sol-gel method. X-ray diffraction (XRD) and transmission electron microscope (TEM) analysis revealed that the samples had pure ZnO wurtzite structure and Fe ions were well incorporated into the ZnO crystal lattice. X-ray photoelectron spectroscopy (XPS) showed that both Fe(2+) and Fe(3+) existed in Zn(0.97)Fe(0.03)O. The result of x-ray absorption near-edge structure (XANES) further testified that Fe ions took the place of Zn sites in our samples. Magnetic measurements indicated that Zn(0.97)Fe(0.03)O was ferromagnetic at room temperature.

Synthesis of galium nitride thin films using sol-gel dip coating method

NASA Astrophysics Data System (ADS)

Hamid, Maizatul Akmam Ab; Ng, Sha Shiong

2017-12-01

In this research, gallium nitride (GaN) thin film were grown on silicon (Si) substrate by a low-cost sol-gel dip coating deposition method. The GaN precursor solution was prepared using gallium (III) nitrate hydrate powder, ethanol and diethanolamine as a starting material, solvent and surfactant respectively. The structural, morphological and optical characteristics of the deposited GaN thin film were investigated. Field-emission scanning electron microscopy observations showed that crack free and dense grains GaN thin films were formed. Energy dispersive X-ray analysis confirmed that the oxygen content in the deposited films was low. X-ray diffraction results revealed that deposited GaN thin films have hexagonal wurtzite structure.

Synthesis of Bi0.9Nd0.1FeO3 multiferroic nanoceramic by sol-gel method and its structural, surface morphology and dielectric analysis

NASA Astrophysics Data System (ADS)

Das, S.; Bera, K. P.; Nath, T. K.

2017-05-01

Synthesis of Nd-doped BFO multiferroic nanoceramic by the conventional sol-gel method has been carried out. HRXRD and FESEM have been used for the structural analysis to confirm the triclinic structure and to obtain the surface morphology showing agglomeration and to find out the size of the nanoparticles. A high precision LCR meter has been used to record the dielectric constants at various temperatures. Several anomalies are observed whose physical explanations have been given. Space charge polarization effect and magnetoelectric coupling have been confirmed in the synthesized Bi0.9Nd0.1FeO3 nanoceramic sample.

Synthesis and characterization of NiO nanopowder by sol-gel process

DOE Office of Scientific and Technical Information (OSTI.GOV)

Ningsih, Sherly Kasuma Warda

2015-09-30

Preparation of nickel oxide (NiO) nanopowder by sol-gel process has been studied. NiO nanopowders were obtained by sol-gel method by using nickel nitrate hexahydrate and sodium hydroxide and aquadest were used as precursor, agent precipitator and solvent, respectively. The powders were formed by drying at 110°C and followed by heating in the furnace at 400°C for 1.5 hours. The product was obtained black powder. The product was characterized by Energy Dispesive X-ray Fluorescence (ED-XRF), X-ray diffraction (XRD) and Scanning Electron Microscopy (SEM). The ED-XRF pattern shows the composition of NiO produced was 97.1%. The XRD pattern showed NiO forms weremore » produced generally in monoclinic stucture. The crystalline size of NiO was obtained in the range 40-85 nm. SEM micrograph clearly showed that powder had a spherical with uniform distribution size is 0.1-1.0 µm approximately.« less

Solid-phase microextraction of methadone in urine samples by electrochemically co-deposited sol-gel/Cu nanocomposite fiber.

PubMed

Mohammadiazar, Sirwan; Hasanli, Fateme; Maham, Mehdi; Payami Samarin, Somayeh

2017-08-01

Electrochemically co-deposited sol-gel/Cu nanocomposites have been introduced as a novel, simple and single-step technique for preparation of solid-phase microextraction (SPME) coating to extract methadone (MDN) (a synthetic opioid) in urine samples. The porous surface structure of the sol-gel/Cu nanocomposite coating was revealed by scanning electron microscopy. Direct immersion SPME followed by HPLC-UV determination was employed. The factors influencing the SPME procedure, such as the salt content, desorption solvent type, pH and equilibration time, were optimized. The best conditions were obtained with no salt content, acetonitrile as desorption solvent type, pH 9 and 10 min equilibration time. The calibration graphs for urine samples showed good linearity. The detection limit was about 0.2 ng mL -1 . Also, the novel method for preparation of nanocomposite fiber was compared with previously reported techniques for MDN determination. The results show that the novel nanocomposite fiber has relatively high extraction efficiency. Copyright © 2016 John Wiley & Sons, Ltd.

Structure and intense UV up-conversion emissions in RE3+-doped sol-gel glass-ceramics containing KYF4 nanocrystals

NASA Astrophysics Data System (ADS)

Yanes, A. C.; Santana-Alonso, A.; Méndez-Ramos, J.; del-Castillo, J.

2013-12-01

Transparent nano-glass-ceramics containing KYF4 nanocrystals were successfully obtained by the sol-gel method, doped with Eu3+ and co-doped with Yb3+ and Tm3+ ions. Precipitation of cubic KYF4 nanocrystals was confirmed by X-ray diffraction and high-resolution transmission electron microscope images. Excitation and emission spectra let us to discern between ions into KYF4 nanocrystals and those remaining in a glassy environment, supplemented with time-resolved photoluminescence decays, that also clearly reveal differences between local environments. Unusual high-energy up-conversion emissions in the UV range were obtained in Yb3+-Tm3+ co-doped samples, and involved mechanisms were discussed. The intensity of these high-energy emissions was analyzed as a function of Yb3+ concentration, heat treatment temperature of precursor sol-gel glasses and pump power, determining the optimum values for potential optical applications as highly efficient UV up-conversion materials in UV solid-state lasers.

Preparation of stir bars for sorptive extraction using sol-gel technology.

PubMed

Liu, Wenmin; Wang, Hanwen; Guan, Yafeng

2004-08-06

A sol-gel coating method for the preparation of extractive phase on bars used in sorptive microextraction is described. The extraction phase of poly(dimethylsiloxane) is partially crosslinked with the sol-gel network, and the most part is physically incorporated in the network. Three aging steps at different temperatures are applied to complete the crosslinking process. Thirty-micrometer-thick coating layer is obtained by one coating process. The improved coating shows good thermal stability up to 300 degrees C. Spiked aqueous samples containing n-alkanes, polycyclic aromatic hydrocarbons and organophosphorus pesticides were analyzed by using the sorptive bars and GC. The results demonstrate that it is suitable for both aploar and polar analytes. The detection limit for chrysene is 7.44 ng/L, 0.74 ng/L for C19 and 0.9 ng/L for phorate. The extraction equilibration can be reached in less than 15 min by supersonic extraction with the bars of 30 microm coating layer.

Rheological study of physical cross-linked quaternized cellulose hydrogels induced by β-glycerophosphate.

PubMed

You, Jun; Zhou, Jinping; Li, Qian; Zhang, Lina

2012-03-20

As a weak base, β-glycerophosphate (β-GP) was used to spontaneously initiate gelation of quaternized cellulose (QC) solutions at body temperature. The QC/β-GP solutions are flowable below or at room temperature but gel rapidly under physiological conditions. In order to clarify the sol-gel transition process of the QC/β-GP systems, the complex was investigated by dynamic viscoelastic measurements. The shear storage modulus (G') and loss modulus (G″) as a function of (1) concentration of β-GP (c(β-GP)), (2) concentration of QC (c(QC)), (3) degree of substitution (DS; i.e., the average number of substituted hydroxyl groups in the anhydroglucose unit) of QC, (4) viscosity-average molecular weight (M(η)) of QC, and (5) solvent medium were studied by the oscillatory rheology. The sol-gel transition temperature of QC/β-GP solutions decreased with an increase of c(QC) and c(β-GP), the M(η) of QC, and a decrease of the DS of QC and pH of the solvent. The sol-gel transition temperature and time could be easily controlled by adjusting the concentrations of QC and β-GP, M(η) and DS of QC, and the solvent medium. Gels formed after heating were irreversible; i.e., after cooling to lower temperature they could not be dissolved to become liquid again. The aggregation and entanglement of QC chains, electrostatic interaction, and hydrogen bonding between QC and β-GP were the main factors responsible for the irreversible sol-gel transition behavior of QC/β-GP systems.

Structural development and kinetic analysis of PbTiO3 powders processed at low-temperature via new sol-gel approach

NASA Astrophysics Data System (ADS)

Bel-Hadj-Tahar, Radhouane; Abboud, Mohamed

2018-04-01

The synthesis of crystalline lead titanate powder by a generic low-temperature sol-gel approach is developed. Acetoin was added as ligand, instead of the commonly used alkanolamines, to ensure total dissolution of the precursor compounds. The feasibility of the acetoin-Ti isopropoxide complex as a new precursor of PbTiO3 perovskite particles via sol-gel method has been demonstrated. No excess lead has been introduced. Nanometric PbTiO3 crystallites have been formed at 400 °C under atmospheric pressure from titanium isopropoxide and lead acetate in alcoholic solution by remarkably low activation energy of crystallization process of 90 kJ mol-1. The powders show tetragonal lattice and dendritic morphology. In addition to the effect of heat-treatment temperature, time, and atmosphere, the sol chemistry particularly influenced the phase composition, particle size, and particle morphology. The use of different ligands significantly modified powder morphology. The extent of the crystallization was quantitatively evaluated by differential thermal analysis and analyzed by Johnson-Mehl-Avrami approach. The crystallization followed two rate regimes depending on the interval of the crystallized fraction.

Effect of Synthesis Method of La1 - x Sr x MnO3 Manganite Nanoparticles on Their Properties

NASA Astrophysics Data System (ADS)

Shlapa, Yulia; Solopan, Sergii; Belous, Anatolii; Tovstolytkin, Alexandr

2018-01-01

Nanoparticles of lanthanum-strontium manganite were synthesized via different methods, namely, sol-gel method, precipitation from non-aqueous solution, and precipitation from reversal microemulsions. It was shown that the use of organic compounds and non-aqueous media allowed significantly decreasing of the crystallization temperature of nanoparticles, and the single-phased crystalline product was formed in one stage. Morphology and properties of nanoparticles depended on the method and conditions of the synthesis. The heating efficiency directly depended on the change in the magnetic parameters of nanoparticles, especially on the magnetization. Performed studies showed that each of these methods of synthesis can be used to obtain weakly agglomerated manganite nanoparticles; however, particles synthesized via sol-gel method are more promising for use as hyperthermia inducers. PACS: 61.46.Df 75.75.Cd 81.20. Fw

Optimizing Metalloporphyrin-Catalyzed Reduction Reactions for In Situ Remediation of DOE Contaminants

DOE Office of Scientific and Technical Information (OSTI.GOV)

Schlautman, Mark A.

2013-07-14

Past activities have resulted in a legacy of contaminated soil and groundwater at Department of Energy facilities nationwide. Uranium and chromium are among the most frequently encountered and highest-priority metal and radionuclide contaminants at DOE installations. Abiotic chemical reduction of uranium and chromium at contaminated DOE sites can be beneficial because the reduced metal species are less soluble in water, less mobile in the environment, and less toxic to humans and ecosystems. Although direct biological reduction has been reported for U(VI) and Cr(VI) in laboratory studies and at some field sites, the reactions can sometimes be slow or even inhibitedmore » due to unfavorable environmental conditions. One promising approach for the in-situ remediation of DOE contaminants is to develop electron shuttle catalysts that can be delivered precisely to the specific subsurface locations where contaminants reside. Previous research has shown that reduction of oxidized organic and inorganic contaminants often can be catalyzed by electron shuttle systems. Metalloporphyrins and their derivatives are well known electron shuttles for many biogeochemical systems, and thus were selected to study their catalytic capabilities for the reduction of chromium and uranium in the presence of reducing agents. Zero valent iron (ZVI) was chosen as the primary electron donor in most experimental systems. Research proceeded in three phases and the key findings of each phase are reported here. Phase I examined Cr(VI) reduction and utilized micro- and nano-sized ZVI as the electron donors. Electron shuttle catalysts tested were cobalt- and iron-containing metalloporphyrins and Vitamin B12. To aid in the recycle and reuse of the nano-sized ZVI and soluble catalysts, sol-gels and calcium-alginate gel beads were tested as immobilization/support matrices. Although the nano-sized ZVI could be incorporated within the alginate gel beads, preliminary attempts to trap it in sol-gels were not successful. Conversely, the water-soluble catalysts could be trapped within sol-gel matrices but they tended to leach out of the alginate gel beads during use. In general, immobilization of the nano-sized ZVI in gel beads and of the catalysts in sol-gels tended to result in slower rates of Cr(VI) reduction, but these effects could be overcome to some extent by using higher reactant/catalyst concentrations. In addition, the lowering of their effectiveness would likely be offset by the benefits obtained when recycling and reusing the materials because they were immobilized. Addition of the catalytic electron shuttles will be most useful when the micro-sized or nano-sized ZVI becomes less reactive with reaction time. Continued work in Phase II in the area of nano-sized ZVI immobilization led to procedures that were successful in incorporating the iron particles in sol-gel matrices. The water-soluble reductants sodium dithionite and L-ascorbic acid were also tested, but their use appeared to lead to formation of complexes with the uranyl cation which limited their effectiveness. Also, although the sol-gel supported nano-sized ZVI showed some promise at reducing uranium, the fluoride used in the sol-gel synthesis protocol appeared to lead to formation of uranyl-fluoride complexes that were less reactive. Because hexavalent chromium is an anion which does not form complexes with fluoride, it was used to demonstrate the intrinsic reactivity of the sol-gel immobilized nano-sized ZVI. Consistent with our observations in Phase I, the sol-gel matrix once again slowed down the reduction reaction but the expected benefits of recycle/reuse should outweigh this adverse effect. The major emphasis in Phase III of this study was to simultaneously incorporate nano-sized ZVI and water-soluble catalysts in the same sol-gel matrix. The catalysts utilized were cobalt complexes of uroporphyrin and protoporphyrin and Cr(VI) reduction was used to test the efficacy of the combined "catalyst + reductant" sol-gel matrix. When enough catalyst was added to the sol-gels, enhancement of the Cr(VI) reduction reaction was observed. At the lowest levels of catalyst addition, however, the rates of Cr(VI) reduction were similar to those systems which only used sol-gel immobilized nano-sized ZVI without any catalyst present. These findings suggest future areas of research that should be pursued to further optimize abiotic reduction reactions of metals with combined "catalyst + reductant" matrices.« less

The Influence of the Polymer Amount on the Biological Properties of PCL/ZrO2 Hybrid Materials Synthesized via Sol-Gel Technique

PubMed Central

Tranquillo, Elisabetta; Illiano, Michela; Sapio, Luigi; Spina, Annamaria; Naviglio, Silvio

2017-01-01

Organic/inorganic hybrid materials are attracting considerable attention in the biomedical area. The sol-gel process provides a convenient way to produce many bioactive organic–inorganic hybrids. Among those, poly(e-caprolactone)/zirconia (PCL/ZrO2) hybrids have proved to be bioactive with no toxic materials. The aim of this study was to investigate the effects of these materials on the cellular response as a function of the PCL content, in order to evaluate their potential use in the biomedical field. For this purpose, PCL/ZrO2 hybrids containing 6, 12, 24, and 50 wt % of PCL were synthesized by the sol-gel method. The effects of their presence on the NIH-3T3 fibroblast cell line carrying out direct cell number counting, MTT, cell damage assays, flow cytometry-based analysis of cell-cycle progression, and immunoblotting experiments. The results confirm and extend the findings that PCL/ZrO2 hybrids are free from toxicity. The hybrids containing 12 and 24 wt % PCL, (more than 6 and 50 wt % ones) enhance cell proliferation when compared to pure ZrO2 by affecting cell cycle progression. The finding that the content of PCL in PCL/ZrO2 hybrids differently supports cell proliferation suggests that PCL/ZrO2 hybrids could be useful tools with different potential clinical applications. PMID:29039803

A new biocatalyst: Penicillin G acylase immobilized in sol-gel micro-particles with magnetic properties.

PubMed

Bernardino, Susana M S A; Fernandes, Pedro; Fonseca, Luís P

2009-05-01

The present work focuses on the development and basic characterization of a new magnetic biocatalyst, namely penicillin G acylase (PGA), immobilized in sol-gel matrices with magnetic properties, ultimately aimed for application in cephalexin (CEX) synthesis. A mechanically stable carrier, based on porous xerogels silica matrixes starting from tetramethoxysilane (TMOS), was prepared leading to micro-carriers with medium sized particles of 30 microm, as determined by scanning electron microscopy. An immobilization yield of 95-100% and a recovered activity of 50-65% at 37 degrees C, as determined by penicillin G (PG) hydrolysis (pH STAT method), were observed. These results clearly exceed those reported in a previous work on PGA immobilization in sol-gel, where only 10% of activity was recovered. The values of activity were kept constant for 6 months. Immobilized PGA (682 U/g(dry weight)) retained high specific activity throughout ten consecutive runs for PG hydrolysis, suggesting adequate biocatalyst stability. The CEX synthesis was performed at 14 degrees C, using the free and immobilized PGA in aqueous medium. Phenylglycine methyl ester was used as acyl donor at 90 mM and 7-aminodeacetoxycephalosporanic acid was the limiting substrate at 30 mM. The CEX stoichiometric yield after 1-h reaction was close to 68% (23 mM CEX/h) and 65% (19 mM CEX/h), respectively.

Sol-gel nano-porous silica-titania thin films with liquid fill for optical interferometric sensors

NASA Astrophysics Data System (ADS)

Martin, Andrew J.; Green, Mino

1990-11-01

The production of thin films whose refractive index is measurand specific, for use in an interferometric fiber optic chemical sensor, is discussed. The problem of making such coatings has been tackled by a system we have termed the "guest-host" approach, in which an active liquid whose index varies with measurand, is contained within a porous glass host of fixed index. Suitable porous silica-titania glass films have been produced via the sol-gel process. The use of this system enables the index of the glass to be varied, so that the composite index of the liquid filled film can be tailored to that required by the optical system. The sol-gel method developed is based upon the hydrolysis and polymerisation of metal alkoxides, in an acidic aqueous/alcoholic solution. Thin film slab waveguides were deposited in order to measure the light scattering losses, which were found to be typically ''1dB/cm. The porosity of films was studied using a new technique developed in which water adsorption isotherms are plotted using ellipsometry. The pore size was found to be very small of pore diameter in the nanometer range, and the total porosity -1O%. Both of these factors were increased by the removal of residual organic material, using hydrogen peroxide. Finally the use of pH indicator dyes as a liquid fill is discussed, to produce a pH sensor.

Use of sol-gels as solid matrixes for simultaneous multielement determination by radio frequency glow discharge optical emission spectrometry: determinations of suspended particulate matter.

PubMed

Davis, W Clay; Knippel, Brad C; Cooper, Julia E; Spraul, Bryan K; Rice, Jeanette K; Smith, Dennis W; Marcus, R Kenneth

2003-05-15

A new approach for the analysis of particulate matter by radio frequency glow discharge optical emission spectrometry (rf-GD-OES) is described. Dispersion of the particles in a sol-gel sample matrix provides a convenient means of generating a thin film suitable for sputter-sampling into the discharge. Acid-catalyzed sol-gel glasses synthesized from tetramethyl orthosilicate were prepared and spun-cast on glass substrates. The resultant thin films on glass substrates were analyzed to determine the discharge operating conditions and resultant sputtering characteristics while a number of optical emission lines of the film components were monitored. Slurries of powdered standard reference materials NIST SRM 1884a (Portland Cement) and NIST SRM 2690 (Coal Fly Ash) dispersed in the sols were cast into films in the same manner. Use of the sol-gels as sample matrixes allows for background subtraction through the use of analytical blanks and may facilitate the generation of calibration curves via readily synthesized, matrix-matched analytical standards in solids analysis. Detection limits were determined for minor elements via the RSDB method to be in the range of 1-10 microg/g in Portland Cement and Coal Fly Ash samples for the elements Al, Fe, Mg, S, and Si. Values for Ca were in the range of 15-35 microg/g. This preliminary study demonstrates the possibility of incorporating various insoluble species, including ceramics and geological specimens in powder form, into a solid matrix for further analysis by either rf-GD-OES or MS.

YIG based broad band microwave absorber: A perspective on synthesis methods

NASA Astrophysics Data System (ADS)

Sharma, Vinay; Saha, J.; Patnaik, S.; Kuanr, Bijoy K.

2017-10-01

The fabrication of a thin layer of microwave absorber that operates over a wide band of frequencies is still a challenging task. With recent advances in nanostructure synthesis techniques, considerable progress has been achieved in realizations of thin nanocomposite layer designed for full absorption of incident electromagnetic (EM) radiation covering S to K band frequencies. The primary objective of this investigation is to achieve best possible EM absorption with a wide bandwidth and attenuation >10 dB for a thin absorbing layer (few hundred of microns). Magnetic yttrium iron garnet (Y3Fe5O12; in short YIG) nanoparticles (NPs) were prepared by sol-gel (SG) as well as solid-state (SS) reaction methods to elucidate the effects of nanoscale finite size on the magnetic behavior of the particles and hence their microwave absorption capabilities. It is found that YIG prepared by these two methods are different in many ways. Magnetic properties investigated using vibrating sample magnetometry (VSM) exhibit that the coercivity (Hc) of solid-state NPs is much larger (72 Oe) than the sol-gel NPs (31 Oe). Microwave absorption properties were studied by ferromagnetic resonance (FMR) technique in field sweep mode at different fixed frequencies. A thin layer (∼300 μm) of YIG film was deposited using electrophoretic deposition (EPD) technique over a coplanar waveguide (CPW) transmission line made on copper coated RT/duroid® 5880 substrates. Temperature dependent magnetic properties were also investigated using VSM and FMR techniques. Microwave absorption properties were investigated at high temperatures (up to 300 °C) both for sol-gel and solid-state synthesized NPs and are related to skin depth of YIG films. It is observed that microwave absorption almost vanishes when the temperature reached the Néel temperature of YIG.

Method for net-shaping using aerogels

DOEpatents

Brinker, C. Jeffrey; Ashey, Carol S.; Reed, Scott T.; Sriram, Chunangad S.; Harris, Thomas M.

2001-01-01

A method of net-shaping using aerogel materials is provided by first forming a sol, aging the sol to form a gel, with the gel having a fluid component and having been formed into a medium selected from the group consisting of a powder, bulk material, or granular aerobeads, derivatizing the surface of the gel to render the surface unreactive toward further condensation, removing a portion of the fluid component of the final shaped gel to form a partially dried medium, placing the medium into a cavity, wherein the volume of said medium is less that the volume of the cavity, and removing a portion of the fluid component of the medium. The removal, such as by heating at a temperature of approximately less than 50.degree. C., applying a vacuum, or both, causes the volume of the medium to increase and to form a solid aerogel. The material can be easily removed by exposing the material to a solvent, thereby reducing the volume of the material. In another embodiment, the gel is derivatized and then formed into a shaped medium, where subsequent drying reduces the volume of the shaped medium, forming a net-shaping material. Upon further drying, the material increases in volume to fill a cavity. The present invention is both a method of net-shaping and the material produced by the method.

High Refractive Organic–Inorganic Hybrid Films Prepared by Low Water Sol-Gel and UV-Irradiation Processes

PubMed Central

Ma, Hsiao-Yuan; Wang, Tzong-Liu; Chang, Pei-Yu; Yang, Chien-Hsin

2016-01-01

Organic-inorganic hybrid sols (Ti–O–Si precursor) were first synthesized by the sol-gel method at low addition of water, and were then employed to prepare a highly refractive hybrid optical film. This film was obtained by blending the Ti–O–Si precursor with 2-phenylphenoxyethyl acrylate (OPPEA) to perform photo-polymerization by ultraviolet (UV) irradiation. Results show that the film transparency of poly(Ti–O–Si precursor-co-OPPEA) film is higher than that of a pure poly(Ti–O–Si precursor) film, and that this poly(Ti–O–Si precursor-co-OPPEA) hybrid film exhibits a high transparency of ~93.7% coupled with a high refractive index (n) of 1.83 corresponding to a thickness of 2.59 μm. PMID:28344303

Site selective generation of sol-gel deposits in layered bimetallic macroporous electrode architectures.

PubMed

Lalo, Hélène; Bon-Saint-Côme, Yémima; Plano, Bernard; Etienne, Mathieu; Walcarius, Alain; Kuhn, Alexander

2012-02-07

The elaboration of an original composite bimetallic macroporous electrode containing a site-selective sol-gel deposit is reported. Regular colloidal crystals, obtained by a modified Langmuir-Blodgett approach, are used as templates for the electrogeneration of the desired metals in the form of a well-defined layered bimetallic porous electrode. This porous matrix shows a spatially modulated electroactivity which is subsequently used as a strategy for targeted electrogeneration of a sol-gel deposit, exclusively in one predefined part of the porous electrode.

Photonic devices based on patterning by two photon induced polymerization techniques

NASA Astrophysics Data System (ADS)

Fortunati, I.; Dainese, T.; Signorini, R.; Bozio, R.; Tagliazucca, V.; Dirè, S.; Lemercier, G.; Mulatier, J.-C.; Andraud, C.; Schiavuta, P.; Rinaldi, A.; Licoccia, S.; Bottazzo, J.; Franco Perez, A.; Guglielmi, M.; Brusatin, G.

2008-04-01

Two and three dimensional structures with micron and submicron resolution have been achieved in commercial resists, polymeric materials and sol-gel materials by several lithographic techniques. In this context, silicon-based sol-gel materials are particularly interesting because of their versatility, chemical and thermal stability, amount of embeddable active compounds. Compared with other micro- and nano-fabrication schemes, the Two Photon Induced Polymerization is unique in its 3D processing capability. The photopolymerization is performed with laser beam in the near-IR region, where samples show less absorption and less scattering, giving rise to a deeper penetration of the light. The use of ultrashort laser pulses allows the starting of nonlinear processes like multiphoton absorption at relatively low average power without thermally damaging the samples. In this work we report results on the photopolymerization process in hybrid organic-inorganic films based photopolymerizable methacrylate-containing Si-nanobuilding blocks. Films, obtained through sol-gel synthesis, are doped with a photo-initiator allowing a radical polymerization of methacrylic groups. The photo-initiator is activated by femtosecond laser source, at different input energies. The development of the unexposed regions is performed with a suitable solvent and the photopolymerized structures are characterized by microscopy techniques.

Eu-Doped BaTiO3 Powder and Film from Sol-Gel Process with Polyvinylpyrrolidone Additive

PubMed Central

García-Hernández, Margarita; García-Murillo, Antonieta; de J. Carrillo-Romo, Felipe; Jaramillo-Vigueras, David; Chadeyron, Geneviève; De la Rosa, Elder; Boyer, Damien

2009-01-01

Transparent BaTiO3:Eu3+ films were prepared via a sol-gel method and dip-coating technique, using barium acetate, titanium butoxide, and polyvinylpyrrolidone (PVP) as modifier viscosity. BaTiO3:Eu3+ films ~500 nm thick, crystallized after thermal treatment at 700 ºC. The powders revealed spherical and rod shape morphology. The optical quality of films showed a predominant band at 615 nm under 250 nm excitation. A preliminary luminescent test provided the properties of the Eu3+ doped BaTiO3. PMID:19865533

Solid materials for removing metals and fabrication method

DOEpatents

Coronado, Paul R.; Reynolds, John G.; Coleman, Sabre J.

2004-10-19

Solid materials have been developed to remove contaminating metals and organic compounds from aqueous media. The contaminants are removed by passing the aqueous phase through the solid materials which can be in molded, granular, or powder form. The solid materials adsorb the metals and the organics leaving a purified aqueous stream. The materials are sol-gel and or sol-gel and granulated activated carbon (GAC) mixtures. The species-specific adsorption occurs through specific chemical modifications of the solids tailored towards the contaminant(s). The contaminated solid materials can then be disposed of or the contaminant can be removed and the solids recycled.

Characterizations of maghemite thin films prepared by a sol-gel method

DOE Office of Scientific and Technical Information (OSTI.GOV)

Lau, L. N., E-mail: lau7798@gmail.com; Ibrahim, N. B., E-mail: baayah@ukm.edu.my

2015-09-25

Iron is one of the abundant elements of Mother Nature and its compound, iron oxide is an interesting material to study since its discovery in the form of magnetite. It can exist in many phases such as hematite and maghemite, this unique nature has put it as a potential candidate in various applications. The aim of this work is to study the influence of different precursor concentrations on the microstructural and magnetic properties of iron oxide thin film. All samples were prepared via the sol-gel method followed by a spin coating technique on quartz substrates. Iron oxide films were confirmedmore » as maghemite phase from X-ray diffraction patterns. The film morphology was examined by a field emission scanning electron microscope and it showed non-systematic value of average grain size and film thickness throughout the study. Hysteresis loop further confirmed that maghemite is a magnetic material when it was characterized by a vibrating sample magnetometer. The coercivity did not show any correlation with molarity. Nevertheless, it increased as the precursor concentration of the film increased due to the domain behaviour. In conclusion, maghemite thin films were successfully synthesized by the sol-gel method with different precursor concentrations in this work.« less

Sol-gel antireflective coating on plastics

DOEpatents

Ashley, C.S.; Reed, S.T.

1988-01-26

An antireflection film made from reliquified sol-gel hydrolyzation, condensation polymeric reaction product of a silicon, alkoxides and/or metal alkoxides, or mixtures thereof. The film is particularly useful for coating plastics.

Effect of ethanol variation on the internal environment of sol-gel bulk and thin films with aging.

PubMed

Gupta, R; Mozumdar, S; Chaudhury, N K

2005-10-15

Sol-gel derived bulk and thin films were prepared from different compositions at low pH ( approximately 2.0) containing varying concentrations of ethanol from 15 to 60% at constant water (H(2)O)/tetraethyl-orthosilicate (TEOS) ratio (R=4). The fluorescence microscopic and spectroscopic measurements on fluorescent probe, Hoechst 33258 (H258) entrapped in these compositions were carried out at different days of storage to monitor the effects of concentration of ethanol on the internal environment of sol-gel materials. Fluorescence microscopic observations on sol-gel thin films, prepared by dip coating technique depicted uniform and cracked surface at withdrawal speed 1cm/min (high speed) and 0.1cm/min (low speed) respectively, which did not change during aging. Fluorescence spectral measurements showed emission maximum of H258 at approximately 535 nm in fresh sols at all concentrations of ethanol which depicted slight blue shift to 512 nm during aging in bulk. No such spectral shift has been observed in sol-gel thin films coated at high speed whereas thin films coated at low speed clearly showed an additional band at approximately 404 nm at 45 and 60% concentration of ethanol after about one month of storage. Analysis of the fluorescence lifetime data indicated single exponential decay (1.6-1.8 ns) in fresh sol and from third day onwards, invariably double exponential decay with a short (tau(1)) and a long (tau(2)) component were observed in sol-gel bulk with a dominant tau(1) at approximately 1.2 ns at all concentrations of ethanol. A double exponential decay consisting of a short component (tau(1)) at approximately 0.2 ns and a long component (tau(2)) at approximately 3.5 ns were observed at all ethanol concentrations in both fresh and aged sol-gel thin films. Further, distribution analysis of lifetimes of H258 showed two mean lifetimes with increased width in aged bulk and thin films. These results are likely to have strong implications in designing the internal environment for applications in biosensors.

Molecularly imprinted polymer-sol-gel tablet toward micro-solid phase extraction: II. Determination of amphetamine in human urine samples by liquid chromatography-tandem mass spectrometry.

PubMed

El-Beqqali, Aziza; Andersson, Lars I; Jeppsson, Amin Dadoun; Abdel-Rehim, Mohamed

2017-09-15

Amphetamine selective molecularly imprinted sol-gel polymer tablets, MIP-tablets, for solid-phase microextraction of biofluid samples were prepared. An acetonitrile solution of deuterated amphetamine template and silane precursor, 3-(propylmethacrylate) trimethoxysilane, was soaked into the pores of polyethylene tablet substrates and polymerized by an acid-catalysed sol-gel process. Application of the resultant MIP-tablets to extract amphetamine from human urine samples followed by LC-MS/MS analysis was investigated. The extraction protocol was optimised with respect to pH of sample, addition of sodium chloride, extraction time, desorption solvent and desorption time. The final analysis method determined amphetamine in human urine with a limit of detection (LOD) of 1.0ng/mL and a lower limit of quantification (LLOQ) of 5ng/mL. Validation demonstrated accuracy of the method was 91.0-104.0% and inter-assay precision was 4.8-8.5% (RSD). Extraction recovery was 80%. The MIP-tablets could be re-used and the same tablet could be employed for more than twenty extractions. Copyright © 2017 Elsevier B.V. All rights reserved.

Characterisation of Sol-Gel Synthesis of Phase Pure CaTiO3 Nano Powders after Drying

NASA Astrophysics Data System (ADS)

Mallik, P. K.; Biswal, G.; Patnaik, S. C.; Senapati, S. K.

2015-02-01

According to a few recent studies, calcium titanate (CT) is a material that is similar to hydroxyapatite in biological properties. However, calcium titanate is not currently being used in the biomedical applications as to hydroxyapatite. The objective is to prepare nano calcium titanate powders from the equimolar solution of calcium oxide, ethanol and Titanium (IV) isopropoxide via sol-gel synthesis. The phase analysis and morphology of powder particles were studied by X-ray diffraction (XRD), while the composition and size of powder particles were determined by Transmission electron microscope (TEM) attached with energy dispersive x-ray spectrometer (EDS). As results, XRD confirm the presence of phase pure crystalline CaTiO3 after drying at 100°C for 24 hours, while TEM analysis confirms about 13 nm sizes of CaTiO3 particles and some agglomerated particle of 20-30 nm. Moreover, EDS analysis indicates that the approximately stoichiometric Ca/Ti ratio 1:1 was obtained in the CaTiO3 powders. Finally, it can be concluded that described sol-gel synthesis could be novel method for the production of nano CaTiO3 particles at lower temperature compared to any other methods of production.

Fast nucleation for silica nanoparticle synthesis using a sol-gel method.

PubMed

Dixit, Chandra K; Bhakta, Snehasis; Kumar, Ajeet; Suib, Steven L; Rusling, James F

2016-12-01

We have developed a method that for the first time allowed us to synthesize silica particles in 20 minutes using a sol-gel preparation. Therefore, it is critically important to understand the synthesis mechanism and kinetic behavior in order to achieve a higher degree of fine tuning ability during the synthesis. In this study, we have employed our ability to modulate the physical nature of the reaction medium from sol-gel to emulsion, which has allowed us to halt the reaction at a particular time; this has allowed us to precisely understand the mechanism and chemistry of the silica polymerization. The synthesis medium is kept quite simple with tetraethyl orthosilicate (TEOS) as a precursor in an equi-volumetric ethanol-water system and with sodium hydroxide as a catalyst. Synthesis is performed under ambient conditions at 20 °C for 20 minutes followed by phasing out of any unreacted TEOS and polysilicic acid chains via their emulsification with supersaturated water. We have also demonstrated that the developed particles with various sizes can be used as seeds for further particle growth and other applications. Luminol, a chemiluminescent molecule, has been entrapped successfully between the layers of silica and was demonstrated for the chemiluminescence of these particles.

Synthesis of zinc oxide thin films prepared by sol-gel for specific bioactivity

NASA Astrophysics Data System (ADS)

Adam, Tijjani; Basri, B.; Dhahi, Th. S.; Mohammed, Mohammed; Hashim, U.; Noriman, N. Z.; Dahham, Omar S.

2017-09-01

Zinc oxide (ZnO) thin films this device to used for many application like chemical sensor, biosensor, solar energy, etc but my project to use for bioactivity(biosensor). Zinc oxide (ZnO) thin films have been grown using sol-gel technique. Characterization was done using Scanning Electron Microscope (SEM), Energy Dispersive X-ray(EDX) and Electrical Measurement(I-V). ZnO thin film was successfully synthesized using low cost sol-gel spin coating method. The coupling of DNA probe to ZnO thin film supports modified with carboxylic acid (COOH) is certainly the best practical method to make DNA immobilization and it does not require any coupling agent which could be a source of variability during the spotting with an automatic device. So, selected this coupling procedure for further experiments. The sensor was tested with initial trial with low concentrated DNA and able to detect detection of the disease effectively. Silicon-on-insulator (SOI) wafer device with ZnO can detect at different concentration in order to valid the device capabilities for detecting development. The lowest concentration 1 µM HPV DNA probe can detect is 0.1 nM HPV target DNA.

High strength air-dried aerogels

DOEpatents

Coronado, Paul R.; Satcher, Jr., Joe H.

2012-11-06

A method for the preparation of high strength air-dried organic aerogels. The method involves the sol-gel polymerization of organic gel precursors, such as resorcinol with formaldehyde (RF) in aqueous solvents with R/C ratios greater than about 1000 and R/F ratios less than about 1:2.1. Using a procedure analogous to the preparation of resorcinol-formaldehyde (RF) aerogels, this approach generates wet gels that can be air dried at ambient temperatures and pressures. The method significantly reduces the time and/or energy required to produce a dried aerogel compared to conventional methods using either supercritical solvent extraction. The air dried gel exhibits typically less than 5% shrinkage.

Synthesis of Titania-supported Copper Nanoparticles via Refined Alkoxide Sol-gel Process

NASA Astrophysics Data System (ADS)

Wu, Jeffrey C. S.; Tseng, I.-Hsiang; Chang, Wan-Chen

2001-06-01

Nanoparticles of titania and copper-loaded titania were synthesized by a refined sol-gel method using titanium butoxide. Unlike the conventional sol-gel procedure of adding water directly, the esterification of anhydrous butanol and glacial acetic acid provided the hydrolyzing water. In addition, acetic acid also served as a chelating ligand to stabilize the hydrolysis-condensation process and minimize the agglomeration of titania. Following the hydrolysis, Cu/TiO2 was prepared by adding copper chloride to titania sol. The sol was dried, then calcined at 500°C to remove organics and transformed to anatase titania which was verified by XRD. Cu/TiO2 was further hydrogen-reduced at 300°C. The recovery of Ti was exceeded by an average of 95% from titanium butoxide. TEM micrographs show that the Cu/TiO2 particles are near uniform. The average crystallite sizes are 17-20 nm estimated from the peak broadening of XRD spectra. The bandgaps of TiO2 and reduced Cu/TiO2 range from 2.70 to 3.15 eV estimated from the diffusive reflective UV-Vis spectra. XPS analysis shows that Cu 2p3/2 is 933.4 eV indicating primary Cu2O form on the TiO2 supports. The binding energy of Ti does not exhibit chemical shift suggesting negligible interaction of Cu cluster and TiO2 support.

THE MECHANISM OF THE INFLAMMATORY PROCESS : III. ELECTROPHORETIC MIGRATION OF INERT PARTICLES AND BLOOD CELLS IN GELATIN SOLS AND GELS WITH REFERENCE TO LEUCOCYTE EMIGRATION THROUGH THE CAPILLARY WALL.

PubMed

Abramson, H A

1928-07-20

1. Quartz particles and certain other particles move cataphoretically in certain soft gelatin gels, with the same velocity as in the sol. The speed is a function of the true viscosity of the sol or gel, and it is See PDF for Structure apparently not altered in these soft gels by the presence of gel structure. It is proportional to the applied difference of potential. 2. This finding is compatible with the fact that certain sols undergo gelation with no increase of the true viscosity although a marked change in the apparent viscosity takes place. 3. Red cells in soft gelatin-serum gels show a distinct difference in behavior. They migrate through the sol or gel with a speed that is about twice as great as the leucocytes and quartz particles, which latter particles migrate with the same velocity. This ratio has been found to hold for serum and plasma. The absolute velocities are comparatively slightly decreased by the presence of the gel. 4. In more concentrated or stiffer gels, leucocytes, red cells and quartz particles all move at first with the same velocity. By producing mechanical softening of these gels (shearing from cataphoretic movement of the micells within the cell) the red cells presently resume their previous property of independent migration through the gel. 5. The movements of particles in gelatin gels produced by a magnetic force or the force of gravity are of a different nature than those movements produced by cataphoresis. 6. The mechanical nature of obstruction to the cataphoretic migration of leucocytes and red cells in fibrin gels is briefly described. 7. The correlation of cataphoresis of microscopic particles in gels with the order of magnitude and nature of the potential differences in the capillary wall, lends additional evidence to the theory that polymorphonuclear leucocyte emigration and migration are dependent upon these potential differences.

Iron Oxide Silica Derived from Sol-Gel Synthesis

PubMed Central

Darmawan, Adi; Smart, Simon; Julbe, Anne; Diniz da Costa, João Carlos

2011-01-01

In this work we investigate the effect of iron oxide embedded in silica matrices as a function of Fe/Si molar ratio and sol pH. To achieve homogeneous dispersion of iron oxide particles, iron nitrate nonahydrate was dissolved in hydrogen peroxide and was mixed with tetraethyl orthosilicate and ethanol in a sol-gel synthesis method. Increasing the calcination temperature led to a reduction in surface area, although the average pore radius remained almost constant at about 10 Å, independent of the Fe/Si molar ratio or sol pH. Hence, the densification of the matrix was accompanied by similar reduction in pore volume. However, calcination at 700 °C resulted in samples with similar surface area though the iron oxide content increased from 5% to 50% Fe/Si molar ratio. As metal oxide particles have lower surface area than polymeric silica structures, these results strongly suggest that the iron oxides opposed the silica structure collapse. The effect of sol pH was found to be less significant than the Fe/Si molar ratio in the formation of molecular sieve structures derived from iron oxide silica. PMID:28879999

Free-standing coating patterns fabricated by ultraviolet contact lithography using photosensitive sol-gel coatings

NASA Astrophysics Data System (ADS)

Xiang, Youlai; Du, Ai; Li, Xiaoguang; Sun, Wei; Wu, Shuai; Li, Tiemin; Liu, Mingfang; Zhou, Bin

2017-07-01

Photosensitive ZrO2-SiO2 hybrid sol-gel coatings containing large contents of chelating rings were prepared by using the zirconium n-butoxide (TBOZ) and methyltriethoxysilane (MTES) as hybrid precursors, and benzoylacetone (BZAC) as chelating agent. The change of ultraviolet (UV) absorption spectra, chemical composition, and optical properties of ZrO2-SiO2 hybrid sol-gel coatings were analyzed before and after UV exposure and calcination. The refractive index of the ZrO2-SiO2 hybrid gel coatings decreased from 1.673 to 1.561 with the increase of the molar content of MTES in precursors. The sol-gel coating patterns with the periods of 20.24 μm, 10.11 μm and 3.99 μm on the PAMS substrates were firstly obtained by using the photosensitive ZrO2-SiO2 hybrid sol-gel films as fundamental materials through a process of UV contact lithography with photo masks and etching with ethanol. Finally, the free-standing gel coating patterns supported by copper grids, with the period of 12.70 μm and line width of 4.93 μm, and the period of 14.20 μm and line width of 3.82 μm, were obtained by removing the PAMS thermal degradation sacrifice layer after being calcined at 330 °C. Micrometer-periodic free-standing gel coating patterns with different structure have potential applications in the laser physical experiments.

Study of Different Sol-Gel Coatings to Enhance the Lifetime of PDMS Devices: Evaluation of Their Biocompatibility

PubMed Central

Aymerich, María; Gómez-Varela, Ana I.; Álvarez, Ezequiel; Flores-Arias, María T.

2016-01-01

A study of PDMS (polydimethylsiloxane) sol-gel–coated channels fabricated using soft lithography and a laser direct writing technique is presented. PDMS is a biocompatible material that presents a high versatility to reproduce several structures. It is widely employed in the fabrication of preclinical devices due to its advantages but it presents a rapid chemical deterioration to organic solvents. The use of sol-gel layers to cover the PDMS overcomes this problem since it provides the robustness of glass for the structures made with PDMS, decreasing its deterioration and changing the biocompatibility of the surface. In this work, PDMS channels are coated with three different kinds of sol-gel compositions (60MTES/40TEOS, 70MTES/30TISP and 80MTES/20TISP). The endothelial cell adhesion to the different coated devices is evaluated in order to determine the most suitable sol-gel preparation conditions to enhance cellular adhesion. PMID:28773848

A Urea Biosensor from Stacked Sol-Gel Films with Immobilized Nile Blue Chromoionophore and Urease Enzyme.

PubMed

Alqasaimeh, Muawia Salameh; Heng, Lee Yook; Ahmad, Musa

2007-10-11

An optical urea biosensor was fabricated by stacking several layers of sol-gelfilms. The stacking of the sol-gel films allowed the immobilization of a Nile Bluechromoionophore (ETH 5294) and urease enzyme separately without the need of anychemical attachment procedure. The absorbance response of the biosensor was monitoredat 550 nm, i.e. the deprotonation of the chromoionophore. This multi-layer sol-gel filmformat enabled higher enzyme loading in the biosensor to be achieved. The urea opticalbiosensor constructed from three layers of sol-gel films that contained urease demonstrateda much wider linear response range of up to 100 mM urea when compared with biosensorsthat constructed from 1-2 layers of films. Analysis of urea in urine samples with thisoptical urea biosensor yielded results similar to that determined by a spectrophotometricmethod using the reagent p-dimethylaminobenzaldehyde (R² = 0.982, n = 6). The averagerecovery of urea from urine samples using this urea biosensor is approximately 103%.

Sol-gel antireflective coating on plastics

DOEpatents

Ashley, Carol S.; Reed, Scott T.

1990-01-01

An antireflection film made from a reliquified sol-gel hydrolyzation, condensation polymeric reaction product of a silicon, alkoxides and/or metal alkoxides, or mixtures thereof. The film is particularly useful for coating plastics.