modified sol-gel process: Topics by Science.gov

Sample records for modified sol-gel process

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.
Multicomponent micropatterned sol-gel materials by capillary molding

NASA Astrophysics Data System (ADS)

Lochhead, Michael J.; Yager, Paul

1997-10-01

A physically and chemically benign method for patterning multiple sol-gel materials onto a single substrate is described. Structures are demonstrated for potential micro- optical chemical sensor, biosensor, and waveguiding applications. Fabrication is based on the micro molding in capillaries (MIMIC) approach. A novel mold design allows several sols to be cast simultaneously. Closely spaced, organically modified silica ridges containing fluorescent dyes are demonstrated. Ridges have cross sectional dimensions from one to 50 micrometers and are centimeters in length. Processing issues, particularly those related to mold filling, are discussed in detail. Because sol-gel MIMIC avoids the harsh physical and chemical environments normally associated with patterning, the approach allows full exploitation of sol- gel processing advantages, such as the ability to entrap sensitive organic dopant molecules in the sol-gel matrix.
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.
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.
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.
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.
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.
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.
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.
Metal-oxide-based energetic materials and synthesis thereof

DOEpatents

Tillotson, Thomas M. , Simpson; Randall, L [Livermore, CA; Hrubesh, Lawrence W [Pleasanton, CA

2006-01-17

A method of preparing energetic metal-oxide-based energetic materials using sol-gel chemistry has been invented. The wet chemical sol-gel processing provides an improvement in both safety and performance. Essentially, a metal-oxide oxidizer skeletal structure is prepared from hydrolyzable metals (metal salts or metal alkoxides) with fuel added to the sol prior to gelation or synthesized within the porosity metal-oxide gel matrix. With metal salt precursors a proton scavenger is used to destabilize the sol and induce gelation. With metal alkoxide precursors standard well-known sol-gel hydrolysis and condensation reactions are used. Drying is done by standard sol-gel practices, either by a slow evaporation of the liquid residing within the pores to produce a high density solid nanocomposite, or by supercritical extraction to produce a lower density, high porous nanocomposite. Other ingredients may be added to this basic nanostructure to change physical and chemical properties, which include organic constituents for binders or gas generators during reactions, burn rate modifiers, or spectral emitters.
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.
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.
Electroanalytical applications of screen-printable surfactant-induced sol-gel graphite composites

DOEpatents

Guadalupe, Ana R.; Guo, Yizhu

2001-05-15

A process for preparing sol-gel graphite composite electrodes is presented. This process preferably uses the surfactant bis(2-ethylhexyl) sulfosuccinate (AOT) and eliminates the need for a cosolvent, an acidic catalyst, a cellulose binder and a thermal curing step from prior art processes. Fabrication of screen-printed electrodes by this process provides a simple approach for electroanalytical applications in aqueous and nonaqueous solvents. Examples of applications for such composite electrodes produced from this process include biochemical sensors such as disposable, single-use glucose sensors and ligand modified composite sensors for metal ion sensitive sensors.
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...
Sol-gel method to fabricate CaP scaffolds by robocasting for tissue engineering.

PubMed

Houmard, Manuel; Fu, Qiang; Saiz, Eduardo; Tomsia, Antoni P

2012-04-01

Highly porous calcium phosphate (CaP) scaffolds for bone-tissue engineering were fabricated by combining a robocasting process with a sol-gel synthesis that mixed Calcium Nitrate Tetrahydrate and Triethyl Phosphite precursors in an aqueous medium. The resulting gels were used to print scaffolds by robocasting without the use of binder to increase the viscosity of the paste. X-ray diffraction analysis confirmed that the process yielded hydroxyapatite and β-tricalcium phosphate biphasic composite powders. Thus, the scaffold composition after crystallization of the amorphous structure could be easily modified by varying the initial Ca/P ratio during synthesis. The compressive strengths of the scaffolds are ~6 MPa, which is in the range of human cancellous bone (2-12 MPa). These highly porous scaffolds (~73 vol% porosity) are composed of macro-pores of ~260 μm in size; such porosity is expected to enable bone ingrowth into the scaffold for bone repair applications. The chemistry, porosity, and surface topography of such scaffolds can also be modified by the process parameters to favor bone formation. The studied sol-gel process can be used to coat these scaffolds by dip-coating, which induces a significant enhancement of mechanical properties. This can adjust scaffold properties such as composition and surface morphology, which consequently may improve their performances.
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.
Short communication: Evaluation of a sol-gel-based stainless steel surface modification to reduce fouling and biofilm formation during pasteurization of milk.

PubMed

Liu, Dylan Zhe; Jindal, Shivali; Amamcharla, Jayendra; Anand, Sanjeev; Metzger, Lloyd

2017-04-01

Milk fouling and biofilms are common problems in the dairy industry across many types of processing equipment. One way to reduce milk fouling and biofilms is to modify the characteristics of milk contact surfaces. This study examines the viability of using Thermolon (Porcelain Industries Inc., Dickson, TN), a sol-gel-based surface modification of stainless steel, during thermal processing of milk. We used stainless steel 316L (control) and sol-gel-modified coupons in this study to evaluate fouling behavior and bacterial adhesion. The surface roughness as measured by an optical profiler indicated that the control coupons had a slightly smoother finish. Contact angle measurements showed that the modified surface led to a higher water contact angle, suggesting a more hydrophobic surface. The modified surface also had a lower surface energy (32.4 ± 1.4 mN/m) than the control surface (41.36 ± 2.7 mN/m). We evaluated the susceptibility of control and modified stainless steel coupons to fouling in a benchtop plate heat exchanger. We observed a significant reduction in the amount of fouled layer on modified surfaces. We found an average fouling weight of 19.21 mg/cm 2 and 0.37 mg/cm 2 on the control and modified stainless steel coupons, respectively. We also examined the adhesion of Bacillus and biofilm formation, and observed that the modified stainless steel surface offered greater resistance to biofilm formation. Overall, the Thermolon-modified surface showed potential in the thermal processing of milk, offering significantly lower fouling and bacterial attachment than the control surface. Copyright © 2017 American Dairy Science Association. Published by Elsevier Inc. All rights reserved.
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
Site-specific protein immobilization in a microfluidic chip channel via an IEF-gelation process.

PubMed

Shi, Mianhong; Peng, Youyuan; Yu, Shaoning; Liu, Baohong; Kong, Jilie

2007-05-01

A novel strategy for site-specific protein immobilization via combining chip IEF with low-temperature sol-gel technology, called IEF-GEL here, in the channel of a modified poly(methyl methacrylate) (PMMA) microfluidic chip is proposed in this work. The IEF-GEL process involves firstly IEF for homogeneously dissolved protein in PBS containing alumina sol and carrier ampholyte with prearranged pH gradient, and then gelation locally for protein encapsulation. The process and feasibility of proposed IEF-GEL were investigated by EOF measurements, fluorescence microscopic photography, Raman spectrum and further demonstrated by glucose oxidase (GOx) reactors integrated with end-column electrochemical detection. Site-controllable immobilization of protein was realized in a 30 mm long microfluidic chip channel by the strategy to create a approximately 1.7 mm concentrated FITC-BSA band, which leads to great improvement of the elute peak shape, accomplished with remarkably increased sensitivity, approximately 20 times higher than that without IEF-GEL treatment to GOx reactors. The kinetic response of GOx after IEF-GEL treatment was also investigated. The proposed system holds the advantages of IEF and low-temperature sol-gel technologies, i.e. concentrating the protein to be focused and retaining the biological activity for the gel-embedded protein, thus realizes site-specific immobilization of low-concentration protein at nL volume level.
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.

Synthesis and adsorption of silica gel modified 3-aminopropyltriethoxysilane (APTS) from corn cobs against Cu(II) in water

NASA Astrophysics Data System (ADS)

Purwanto, Agung; Yusmaniar, Ferdiani, Fatmawati; Damayanti, Rachma

2017-03-01

Silica gel modified APTS was synthesized from silica gel which was obtained from corn cobs via sol-gel process. Silica gel was synthesized from corn cobs and then chemically modified with silane coupling agent which has an amine group (NH2). This process resulting modified silica gel 3-aminopropyltriethoxysilane (APTS). Characterization of silica gel modified APTS by SEM-EDX showed that the size of the particles of silica gel modified APTS was 20µm with mass percentage of individual elements were nitrogen (N) 15.56%, silicon (Si) 50.69% and oxygen (O) 33.75%. In addition, silica gel modified APTS also showed absorption bands of functional groups silanol (Si-OH), siloxane (Si-O-Si), and an aliphatic chain (-CH2-), as well as amine (NH2) from FTIR spectra. Based on the characterization of XRD, silica gel 2θ of 21.094° and 21.32° respectively. It indicated that both material were amorphous. Determination of optimum pH and contact time on adsorption of silica gel 3-aminopropyltriethoxysilane (APTS) against Cu(II). The optimum pH and contact time was measured by using AAS. Optimum pH of adsorption silica gel modified APTS against metal Cu(II) could be obtained at pH 6 while optimum contact time was at 30 minutes, with the process of adsorption metal Cu(II) occured based on the model Freundlich isotherm.
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.
Analysis of Zinc Oxide Thin Films Synthesized by Sol-Gel via Spin Coating

NASA Astrophysics Data System (ADS)

Wolgamott, Jon Carl

Transparent conductive oxides are gaining an increasingly important role in optoelectronic devices such as solar cells. Doped zinc oxide is a candidate as a low cost and nontoxic alternative to tin doped indium oxide. Lab results have shown that both n-type and p-type zinc oxide can be created on a small scale. This can allow zinc oxide to be used as either an electrode as well as a buffer layer to increase efficiency and protect the active layer in solar cells. Sol-gel synthesis is emerging as a low temperature, low cost, and resource efficient alternative to producing transparent conducting oxides such as zinc oxide. For sol-gel derived zinc oxide thin films to reach their potential, research in this topic must continue to optimize the known processing parameters and expand to new parameters to tighten control and create novel processing techniques that improve performance. The processing parameters of drying and annealing temperatures as well as cooling rate were analyzed to see their effect on the structure of the prepared zinc oxide thin films. There were also preliminary tests done to modify the sol-gel process to include silver as a dopant to produce a p-type thin film. The results from this work show that the pre- and post- heating temperatures as well as the cooling rate all play their own unique role in the crystallization of the film. Results from silver doping show that more work needs to be done to create a sol-gel derived p-type zinc oxide thin film.
Ferroelectric PLZT thick films grown by poly(1-vinylpyrrolidone-co-vinyl acetate) (PVP/VA)-modified sol-gel process

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

Hu, Zhongqiang; Ma, Beihai; Li, Meiya

2016-03-01

We report the growth of ferroelectric Pb0.92La0.08Zr0.52Ti0.48O3 (PLZT) thick films using a poly(1-vinylpyrrolidone-co-vinyl acetate) (PVP/VA)-modified sol–gel process. A per-coating thickness of ≈0.66 μm has been demonstrated using PVP/VA-modified solution, which is more than doubled that of the PLZT films grown by PVP-modified method, and nearly 6 times the per-coating thickness of films prepared by conventional sol–gel process. PLZT thick films grown on LNO/Ni substrates exhibited denser microstructure, higher remanent polarization (11 μC/cm 2) and dielectric tunability (45%), lower leakage current density (≈1.2 × 10 -8 A/cm 2), and higher breakdown strength (≈1.6 MV/cm) than those for the samples grown onmore » PtSi substrates. These results demonstrated great potential of using PVP/VA-modified sol–gel process for high power film capacitor applications.« less
Modified Au nanoparticles-imprinted sol-gel, multiwall carbon nanotubes pencil graphite electrode used as a sensor for ranitidine determination.

PubMed

Rezaei, B; Lotfi-Forushani, H; Ensafi, A A

2014-04-01

A new, simple, and disposable molecularly imprinted electrochemical sensor for the determination of ranitidine was developed on pencil graphite electrode (PGE) via cyclic voltammetry (CV). The PGEs were coated with MWCNTs containing the carboxylic functional group (f-MWCNTs), imprinted with sol-gel and Au nanoparticle (AuNPs) layers (AuNP/MIP-sol-gel/f-MWCNT/PGE), respectively, to enhance the electrode's electrical transmission and sensitivity. The thin film of molecularly imprinted sol-gel polymers with specific binding sites for ranitidine was cast on modified PGE by electrochemical deposition. The AuNP/MIP-sol-gel/f-MWCNT/PGE thus developed was characterized by electrochemical impedance spectroscopy (EIS) and CV. The interaction between the imprinted sensor and the target molecule was also observed on the electrode by measuring the current response of 5.0mMK3[Fe(CN)6] solution as an electrochemical probe. The pick currents of ranitidine increased linearly with concentration in the ranges of 0.05 to 2.0μM, with a detection limit of (S/N=3) 0.02μM. Finally, the modified electrode was successfully employed to determine ranitidine in human urine samples. Copyright © 2014 Elsevier B.V. All rights reserved.
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.
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).
Construction of flame retardant coating on polyamide 6.6 via UV grafting of phosphorylated chitosan and sol-gel process of organo-silane.

PubMed

Kundu, Chanchal Kumar; Wang, Xin; Hou, Yanbei; Hu, Yuan

2018-02-01

Phosphorylated chitosan (PCS) was synthesized and grafted onto the surface of polyamide 6.6 (PA 6.6) fabrics via UV-induced grafting polymerization in order to improve the flame retardant properties. Subsequently, PCS grafted PA 6.6 fabrics were modified by (3-aminopropyl) triethoxysilane (APTES) through sol-gel process in order to form a cross-linking coating. The results obtained from the vertical burning test indicated that only the PCS grafted and simultaneously sol-gel treated fabrics could stop the melt dripping. A maximum reduction (30%) in the peak heat release rate was achieved for the PA6.6-PCS-4W-SG fabric sample. The optimal flame retardant effect was achieved for the PA6.6 fabrics treated by PCS and APTES simultaneously, which was attributed to the joint effect of thermal shielding exerted by the silica and char-forming effect derived from PCS. Copyright © 2017 Elsevier Ltd. All rights reserved.
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.
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.
Bioactivity of sol-gel-derived TiO2 coating on polyetheretherketone: In vitro and in vivo studies.

PubMed

Shimizu, Takayoshi; Fujibayashi, Shunsuke; Yamaguchi, Seiji; Yamamoto, Koji; Otsuki, Bungo; Takemoto, Mitsuru; Tsukanaka, Masako; Kizuki, Takashi; Matsushita, Tomiharu; Kokubo, Tadashi; Matsuda, Shuichi

2016-04-15

A polyetheretherketone (PEEK) surface was modified using a sol-gel-derived TiO2 coating in order to confer bone-bonding ability. To enhance the bonding strength of the coating layer, pretreatment with either O2 plasma or sandblasting was performed prior to sol-gel coating. Additionally, post-treatment with acid was carried out to confer apatite (calcium phosphate)-forming ability to the surface. Biomechanical and histological analyses performed using an in vivo rabbit tibia model showed that PEEK surfaces modified with sol-gel-derived TiO2 and acid post-treatment had better bone-bonding properties than uncoated PEEK surfaces. These modified surfaces also performed well in terms of their in vitro cell responses due to their modified surface chemistries and topographies. Although O2 plasma or sandblasting treatment were, for the most part, equivocal in terms of performance, we conclude that sol-gel-derived TiO2 coating followed by acid post-treatment significantly improves the bone bonding ability of PEEK surfaces, thus rendering them optimal for their use in surgical implants. The role of polyetheretherketone (PEEK) as an alternative biomaterial to conventional metallic implant materials has become increasingly important. However, its low bone bonding ability is yet to be resolved. This in vivo and in vitro investigation on the functionalization of PEEK surfaces highlights the utility of this material in clinical interventions that require implants, and may extend range of applications of PEEK. Copyright © 2016 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.
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.
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
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.
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.
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%.
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.
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.
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.
The influence of precursor addition order on the porosity of sol-gel bioactive glasses.

PubMed

Fernando, Delihta; Colon, Pierre; Cresswell, Mark; Journet, Catherine; Pradelle-Plasse, Nelly; Jackson, Phil; Grosgogeat, Brigitte; Attik, Nina

2018-06-16

The superior textural properties of sol-gel derived bioactive glasses compared to conventional melt quench glasses accounts for their accelerated bioactivity in vitro. Several studies have explored ways to improve the surface properties of sol-gel glasses in order to maximise their efficiency for bone and tooth regeneration. In this study, we investigated the effect of order of network modifying precursor addition on the textural properties of sol-gel derived bioactive glasses. The effect of precursor addition order on the glass characteristics was assessed by switching the order of network modifying precursor (calcium acetate monohydrate and sodium acetate anhydrous) addition for a fixed composition of bioactive glass (75SiO 2 :5CaO:10Na 2 O:10P 2 O 5 ). The results of this study showed that the order of precursor addition does influence the porosity of these glasses. For the glasses of a fixed composition and preparation conditions we achieved a doubling of surface area, a 1.5 times increase in pore volume and a 1.2 times decrease in pore size just by the mixing the network modifying precursors and adding them together in the sol-gel preparation. This simple and straightforward route adaptation to the preparation of bioactive glasses would allow us to enhance the textural properties of existing and novel composition of bioactive glasses and thus accelerate their bioactivity. Copyright © 2018 The Academy of Dental Materials. Published by Elsevier Inc. All rights reserved.

A new powder production route for transparent spinel windows: powder synthesis and window properties

NASA Astrophysics Data System (ADS)

Cook, Ronald; Kochis, Michael; Reimanis, Ivar; Kleebe, Hans-Joachim

2005-05-01

Spinel powders for the production of transparent polycrystalline ceramic windows have been produced using a number of traditional ceramic and sol-gel methods. We have demonstrated that magnesium aluminate spinel powders produced from the reaction of organo-magnesium compounds with surface modified boehmite precursors can be used to produce high quality transparent spinel parts. The new powder production method allows fine control over the starting particle size, size distribution, purity and stoichiometry. The new process involves formation of a boehmite sol-gel from the hydrolysis of aluminum alkoxides followed by surface modification of the boehmite nanoparticles using carboxylic acids. The resulting surface modified boehmite nanoparticles can then be metal exchanged at room temperature with magnesium acetylacetonate to make a precursor powder that is readily transformed into pure phase spinel.
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.
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.
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.
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.
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.
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...
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.
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.
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.
Rheology of polyaniline-dinonylnaphthalene disulfonic acid (DNNDSA) montmorillonite clay nanocomposites in the sol state: shear thinning versus pseudo-solid behavior.

PubMed

Garai, Ashesh; Nandi, Arun K

2008-04-01

The melt rheology of polyaniline (PANI)-dinonylnaphthalenedisulfonic acid (DNNDSA) gel nanocomposites (GNCs) with organically modified (modified with cetyl trimethylammonium bromide)-montmorillonite (om-MMT) clay has been studied for three different clay concentrations at the temperature range 120-160 degrees C. Field emission scanning electron microscopy (FE-SEM), wide angle X-ray scattering (WAXS), differential scanning calorimetry (DSC) and dc-conductivity data (approximately 10(-3) S/cm) indicate that the PANI-DNNDSA melt is in sol state and it is not de-doped at that condition. The WAXS data indicate that in GNC-1 sol clay tactoids are in exfoliated state but in the other sols they are in intercalated state. The zero shear viscosity (eta0), storage modulus (G') and loss modulus (G") increase than that of pure gel in the GNCs. The pure sol and the sols of gel nanocomposites (GNCs) exhibit Newtonian behavior for low shear rate (< 6 x 10(-3) s(-1)) and power law variation for the higher shear rate region. The characteristic time (A) increase with increasing clay concentration and the power law index (n) decreases with increase in clay concentration in the GNCs indicating increased shear thinning for the clay addition. Thus the sols of om-clay nanocomposites of PANI-DNNDSA system are easily processible. The storage modulus (G') of GNC sols are higher than that of pure PANI-DNNDSA sol, GNC1 sol shows a maximum of 733% increase in storage modulus and the percent increase decreases with increase in temperature. Exfoliated nature of clay tactoids has been attributed for the above dramatic increase of G'. The PANI-DNNDSA sol nanocomposites behave as a pseudo-solid at higher frequency where G' and loss modulus (G") show a crossover point in the frequency sweep experiment at a fixed temperature. The crossover frequency decreases with increase in clay concentration and it increases with increase in temperature for GNC sols. The pseudo-solid behavior has been explained from jamming or network formation of clay tactoids under shear. A probable explanation of the two apparently contradictory phenomena of shear thinning versus pseudo-solid behavior of the nanocomposite sols is discussed.
Effect of Adding SiO2-Al2O3 Sol into Anodizing Bath on Corrosion Resistance of Oxidation Film on Magnesium Alloy

NASA Astrophysics Data System (ADS)

Liu, Huicong; Zhu, Liqun; Li, Weiping

Due to the widely use in automobile and construction field, AZ91D magnesium alloy need to be protected more effectively for its high chemical activity. In this paper, three kinds of films were formed on magnesium alloy. The first kind of film, named as anodic oxidation film, was prepared by anodic oxidation in the alkaline solution. The processes for preparing the second kind of film, named as multiple film, involved coating sol-gel on the samples and heat-treating before anodic oxidation. The third kind of film was prepared by anodic oxidation in the alkaline oxidation solution containning 5% (vol) SiO2-Al2O3 sol, named as modified oxidation film. The corrosion resistance of the three different films was investigated. The results showed that the modified oxidation film had the highest corrosion resistance due to the largest thickness and most dense surface morphology. Sol was discussed to react during the film forming process, which leaded to the difference between modified oxidation film and anodic oxidation film.
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
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.
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%.
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.
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
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...
Sol-gel synthesis of mesoporous CaCu{sub 3}Ti{sub 4}O{sub 12} thin films and their gas sensing response

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

Parra, R., E-mail: rparra@fi.mdp.edu.a; Savu, R.; Ramajo, L.A.

2010-06-15

A new sol-gel synthesis procedure of stable calcium copper titanate (CaCu{sub 3}Ti{sub 4}O{sub 12}-CCTO) precursor sols for the fabrication of porous films was developed. The composition of the sol was selected in order to avoid the precipitation of undesired phases; ethanol was used as solvent, acetic acid as modifier and poly(ethyleneglycol) as a linker agent. Films deposited by spin-coating onto oxidized silicon substrates were annealed at 700 {sup o}C. The main phase present in the samples, as detected by X-ray diffraction and Raman spectroscopy, was CaCu{sub 3}Ti{sub 4}O{sub 12}. Scanning electron microscopy analysis showed that mesoporous structures, with thicknesses betweenmore » 200 and 400 nm, were developed as a result of the processing conditions. The films were tested regarding their sensibility towards oxygen and nitrogen at atmospheric pressure using working temperatures from 200 to 290 {sup o}C. The samples exhibited n-type conductivity, high sensitivity and short response times. These characteristics indicate that CCTO mesoporous structures obtained by sol-gel are suitable for application in gas sensing. - Graphical abstract: A sol-gel synthesis procedure toward stable CaCu{sub 3}Ti{sub 4}O{sub 12}-precursor sols avoiding the precipitation of undesired compounds is proposed. Films deposited by spin-coating onto oxidized silicon substrates were annealed at 700 {sup o}C. The thickness varied between 200 and 400 nm depending on sol composition. The films, tested as gas sensors for O{sub 2}, showed n-type conductivity, good sensitivity and short response times.« less

High surface area neodymium phosphate nano particles by modified aqueous sol-gel method

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

Sankar, Sasidharan; Warrier, Krishna Gopakumar, E-mail: wwarrierkgk@yahoo.co.in; Komban, Rajesh

2011-12-15

Graphical abstract: Synthesis of nano rod shaped neodymium phosphate particles with specific surface area as high as 107 m{sup 2} g{sup -1} and particles could be compacted and sintered at as low as 1300 Degree-Sign C to a density of 98.5% (theoretical) with an average grain size of {approx}1 {mu}m. Highlights: Black-Right-Pointing-Pointer Nano size neodymium phosphate is synthesized and characterized using a novel modified aqueous sol gel process. Black-Right-Pointing-Pointer Specific surface area above 100 m{sup 2} g{sup -1} achieved without the addition of any complexing agents. Black-Right-Pointing-Pointer High sintered density reported than the density obtained for powder synthesized through conventionalmore » solid state reaction. Black-Right-Pointing-Pointer The particles are nano sized and have rod shape morphology and are retained at higher temperatures. Black-Right-Pointing-Pointer An average grain size of {approx}1 {mu}m obtained for sintered NdPO{sub 4} after thermal etching at 1400 Degree-Sign C. -- Abstract: Synthesis of nano rod shaped neodymium phosphate (NdPO{sub 4}) particles with specific surface area as high as 107 m{sup 2}g{sup -1} and an average length of 50 nm with aspect ratio 5 was achieved using modified sol gel method. Crystallite size calculated from the X-ray diffraction data by applying Scherer equation was 5 nm for the precursor gel after calcination at 400 Degree-Sign C. NdPO{sub 4} was first precipitated from neodymium nitrate solution using phosphoric acid followed by peptization using dilute nitric acid and further gelation in ammonia atmosphere. The calcined gel powders were further characterized by surface area (Brunauer-Emmet-Teller nitrogen adsorption analysis), Transmission electron microscopy, scanning electron microscopy, UV-vis and FT-IR analysis. Transmission electron microscopy confirms the formation of rod like morphology from the sol, gel and the calcined particles in nano size range. These particles could be compacted and sintered at as low as 1300 Degree-Sign C to a density of 98.5% (theoretical) with an average grain size of {approx}1 {mu}m.« less
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.
Synthesis of CaCu3Ti4O12 by modified Sol-gel method with Hydrothermal process

NASA Astrophysics Data System (ADS)

Masingboon, C.; Rungruang, S.

2017-09-01

CaCu3Ti4O12 powders were synthesized by modified Sol-gel method with Hydrothermal process using Ca(NO3)2· 4H2O, Cu(NO3)2·3H2O, Ti(OC3H7)4 and freshly extracted egg white (ovalbumin) in aqueous medium. The precursor was calcined at 800, 900 and 1000 °C in air for 8 h to obtain nanocrystalline powders of CaCu3Ti4O12. The calcined CaCu3Ti4O12 powders were characterized by XRD, TEM and EDX. The XRD results indicated that all calcined samples have a typical perovskite CaCu3Ti4O12 structure and a small amount of CaTiO3, CuO and TiO2. TEM micrographs showed particle size 100 - 500 nm and EDX results showed elements of CaCu3Ti4O12 powders have calcium, copper, titanium and oxygen.
Deactivation of photocatalytically active ZnO nanoparticle and enhancement of its compatibility with organic compounds by surface-capping with organically modified silica

NASA Astrophysics Data System (ADS)

Cao, Zhi; Zhang, Zhijun

2011-02-01

Tetraethyl orthosilicate (TEOS) and dimethyldiethoxysilane (DEDMS) were used as co-precursors to prepare organically modified silica (ormosil) via sol-gel process. The resultant ormosil was adopted for surface-capping of ZnO nanoparticle, where methyl (organic functional group) and silica (inorganic component) were simultaneously introduced onto the surface of the nanoparticles for realizing dual surface-modification. The ormosil-capped ZnO nanoparticle showed strong hydrophobicity and good compatibility with organic phases, as well as effectively decreased photocatalytic activity and almost unchanged ultraviolet (UV)-shielding ability. More importantly, the comprehensive properties of ormosil-capped ZnO nanoparticle could be manipulated by adjusting the molar ratio of TEOS to DEDMS during sol-gel process. This should help to open a wider window to better utilizing the unique and highly attractive properties such as high UV-shielding ability and high-visible light transparency of ZnO nanoparticle in sunscreen cosmetics.
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.
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.
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.
Characterization and enhanced nonlinear optical limiting response in carbon nanodots dispersed in solid-state hybrid organically modified silica gel glasses

NASA Astrophysics Data System (ADS)

Huang, Li; Zheng, Chan; Guo, Qiaohang; Huang, Dongdong; Wu, Xiukai; Chen, Ling

2018-02-01

Freely dispersed carbon nanodots (CNDs) were introduced into a 3-glycidoxy-propyltrimethoxysilane modified silicate gel glass (i.e. an organically modified silica or ORMOSIL) by a highly efficient and simple sol-gel process, which could be easily extended to prepare functional molecules/nanoparticles solid state optoelectronic devices. Scanning electron microscope imaging, Fourier transform infrared spectroscopy, pore structure measurements, ultraviolet-visible spectroscopy, and fluorescence spectroscopy were used to investigate the surface characteristics, structure, texture, and linear optical properties of the CND/SiO2 ORMOSIL gel glasses. Images and UV/Vis spectra confirmed the successful dispersion of CNDs in the ORMOSIL gel glass. The surface characteristics and pore structure of the host SiO2 matrix were markedly changed through the introduction of the CNDs. The linear optical properties of the guest CNDs were also affected by the sol-gel procedure. The nonlinear optical (NLO) properties of the CNDs were investigated by a nanosecond open-aperture Z-scan technique at 532 nm both in liquid and solid matrices. We found that the NLO response of the CNDs was considerably improved after their incorporation into the ORMOSIL gel glasses. Possible enhancement mechanisms were also explored. The nonlinear extinction coefficient gradually increased while the optical limiting (OL) threshold decreased as the CND doping level was increased. This result suggests that the NLO and OL properties of the composite gel glasses can be optimized by tuning the concentration of CNDs in the gel glass matrix. Our findings show that CND/SiO2 ORMOSIL gel glasses are promising candidates for optical limiters to protect sensitive instruments and human eyes from damage caused by high power lasers.
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
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.
Studies on modification of ZnO sol-gel spin coated on flexible substrate at low temperature: Effect of time exposure

NASA Astrophysics Data System (ADS)

Kamardin, Ili Liyana Khairunnisa; Ainuddin, Ainun Rahmahwati

2017-04-01

Transparent Conducting Oxide (TCO) Film has been chosen as flexible substrate recently in the application of a device. One of the TCO mostly used is ITO/PET substrates. Through this communication, the effect of time exposure of ZnO thin film by modified sol-gel deposited on flexible substrates was investigated. 0.75 M of NaOH and C6H8O7 were dropped directly into precursor solution right before aging process in order to modified precursor solution environment condition. x-ray diffraction pattern recorded plane (100) and (101) as preferential growth orientation. The (101) plane was selected to calculate the average crystallite. The atomic force microscopy indicated RMS value for NaOH samples increased with time exposure. Meanwhile, for C6H8O7 samples decreased with hot water treatment time exposure.
Sol-gel hybrid films based on organosilane and montmorillonite for corrosion inhibition of AA2024.

PubMed

Dalmoro, V; dos Santos, J H Z; Armelin, E; Alemán, C; Azambuja, D S

2014-07-15

The present work reports the production of films on AA2024-T3 composed of vinyltrimethoxysilane (VTMS)/tetraethylorthosilicate (TEOS) with incorporation of montmorillonite (sodium montmorillonite and montmorillonite modified with quaternary ammonium salt, abbreviated Na and 30B, respectively), generated by the sol-gel process. According to FT-IR analyses the incorporation of montmorillonite does not affect silica network. Electrochemical characterization was performed by electrochemical impedance spectroscopy measurement in 0.05 mol L(-1) NaCl solution. Results indicate that montmorillonite incorporation improves the corrosion protection compared to the non-modified system. Scanning electron microscopy micrographs reveal that high concentrations of montmorillonite provide agglomerations on the metallic surface, which is in detriment of the anticorrosive performance. The VTMS/TEOS/30B films with the lowest concentration (22 mg L(-1)) of embedded clay provide the highest corrosion protection. Copyright © 2014 Elsevier Inc. All rights reserved.
Preparation of highly hydrophobic cotton fabrics by modification with bifunctional silsesquioxanes in the sol-gel process

NASA Astrophysics Data System (ADS)

Przybylak, Marcin; Maciejewski, Hieronim; Dutkiewicz, Agnieszka

2016-11-01

The surface modification of cotton fabrics was carried out using two types of bifunctional fluorinated silsesquioxanes with different ratios of functional groups. The modification was performed either by one- or two-step process. Two methods, the sol-gel and the dip coating method were used in different configurations. The heat treatment and the washing process were applied after modification. The wettability of cotton fabric was evaluated by measuring water contact angles (WCA). Changes in the surface morphology were examined by scanning electron microscopy (SEM, SEM-LFD) and atomic force microscopy (AFM). Moreover, the modified fabrics were subjected to analysis of elemental composition of the applied coatings using SEM-EDS techniques. Highly hydrophobic textiles were obtained in all cases studied and one of the modifications resulted in imparting superhydrophobic properties. Most of impregnated textiles remained hydrophobic even after multiple washing process which shows that the studied modification is durable.
An abrasion-resistant and broadband antireflective silica coating by block copolymer assisted sol-gel method.

PubMed

Zou, Liping; Li, Xiaoguang; Zhang, Qinghua; Shen, Jun

2014-09-02

A double-layer broadband antireflective (AR) coating was prepared on glass substrate via sol-gel process using two kinds of acid-catalyzed TEOS-derived silica sols. The relative dense layer with a porosity of ∼10% was obtained from an as-prepared sol, while the porous layer with a porosity of ∼55% was from a modified one with block copolymer (BCP) Pluronic F127 as template which results in abundant ordered mesopores. The two layers give rise to a reasonable refractive index gradient from air to the substrate and thus high transmittance in a wide wavelength range, and both of them have the same tough skeleton despite different porosity, for which each single-layer and the double-layer coatings all behaved well in the mechanical property tests. The high transmittance and the strong ability of resisting abrasion make this coating promising for applications in some harsh conditions. In addition, the preparation is simple, low-cost, time-saving, and flexible for realizing the optical property.
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.
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.
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
Optical fiber sensor having a sol-gel fiber core and a method of making

DOEpatents

Tao, Shiquan; Jindal, Rajeev; Winstead, Christopher; Singh, Jagdish P.

2006-06-06

A simple, economic wet chemical procedure is described for making sol-gel fibers. The sol-gel fibers made from this process are transparent to ultraviolet, visible and near infrared light. Light can be guided in these fibers by using an organic polymer as a fiber cladding. Alternatively, air can be used as a low refractive index medium. The sol-gel fibers have a micro pore structure which allows molecules to diffuse into the fiber core from the surrounding environment. Chemical and biochemical reagents can be doped into the fiber core. The sol-gel fiber can be used as a transducer for constructing an optical fiber sensor. The optical fiber sensor having an active sol-gel fiber core is more sensitive than conventional evanescent wave absorption based optical fiber sensors.
Selective determination of dopamine using quantum-sized gold nanoparticles protected with charge selective ligands

NASA Astrophysics Data System (ADS)

Kwak, Kyuju; Kumar, S. Senthil; Lee, Dongil

2012-06-01

We report here the selective determination of dopamine (DA) using quantum-sized gold nanoparticles coated with charge selective ligands. Glutathione protected gold nanoparticles (GS-Au25) were synthesized and immobilized into a sol-gel matrix via thiol linkers. The GS-Au25 modified sol-gel electrode was found to show excellent electrocatalytic activity towards the oxidation of DA but no activity towards the oxidation of ascorbic acid. The role of electrostatic charge in the selective electrocatalytic activity of GS-Au25 was verified by voltammetry of redox markers carrying opposite charges. The pH dependent sensitivity for the determination of DA further confirmed the charge screening effect of GS-Au25. Mechanistic investigation revealed that the selectivity is attained by the selective formation of an electrostatic complex between the negatively charged GS-Au25 and DA cation. The GS-Au25 modified sol-gel electrode also showed excellent selectivity for DA in the presence of an interferent, ascorbic acid.We report here the selective determination of dopamine (DA) using quantum-sized gold nanoparticles coated with charge selective ligands. Glutathione protected gold nanoparticles (GS-Au25) were synthesized and immobilized into a sol-gel matrix via thiol linkers. The GS-Au25 modified sol-gel electrode was found to show excellent electrocatalytic activity towards the oxidation of DA but no activity towards the oxidation of ascorbic acid. The role of electrostatic charge in the selective electrocatalytic activity of GS-Au25 was verified by voltammetry of redox markers carrying opposite charges. The pH dependent sensitivity for the determination of DA further confirmed the charge screening effect of GS-Au25. Mechanistic investigation revealed that the selectivity is attained by the selective formation of an electrostatic complex between the negatively charged GS-Au25 and DA cation. The GS-Au25 modified sol-gel electrode also showed excellent selectivity for DA in the presence of an interferent, ascorbic acid. Electronic supplementary information (ESI) available: TEM image of GS-Au25, SWV of GS-Au25 in solution, effect of scan rate on the CV of GS-Au25ME, CVs of DA and AA at the bare GCE and CVs of GS-Au25ME at different pHs. See DOI: 10.1039/c2nr30481c

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.
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.
The Effect of Time, Temperature and Composition on Boron Carbide Synthesis by Sol-gel Method

NASA Astrophysics Data System (ADS)

Hadian, A. M.; Bigdeloo, J. A.

2008-02-01

To minimize free carbon residue in the boron carbide (B4C) powder, a modified sol-gel process is performed where the starting materials as boric acid and citric acid compositions are adjusted. Because of boron loss in the form of B2O2(g) during the reduction reaction of the stoichiometric starting composition, the final B4C powders contain carbon residues. Thus, an excess H3BO3 is used in the reaction to compensate the loss and to obtain stoichiometric powders. Parameters of production have been determined using x-ray diffraction analysis and particle size analyses. The synthesized B4C powder using an excess boric acid composition shows no trace of carbon.
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.
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
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.
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.
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 Derived Warfarin - Silica Composites for Controlled Drug Release.

PubMed

Dolinina, Ekaterina S; Parfenyuk, Elena V

2017-01-01

Warfarin, commonly used anticoagulant in clinic, has serious shortcomings due to its unsatisfactory pharmacodynamics. One of the efficient ways for the improvement of pharmacological and consumer properties of drugs is the development of optimal drug delivery systems. The aim of this work is to synthesize novel warfarin - silica composites and to study in vitro the drug release kinetics to obtain the composites with controlled release. The composites of warfarin with unmodified (UMS) and mercaptopropyl modified silica (MPMS) were synthesized by sol-gel method. The composite formation was confirmed by FTIR spectra. The concentrations of warfarin released to media with pH 1.6, 6.8 and 7.4 were measured using UV spectroscopy. The drug release profiles from the solid composites were described by a series of kinetic models which includes zero order kinetics, first order kinetics, the modified Korsmeyer-Peppas model and Hixson-Crowell model. The synthesized sol-gel composites have different kinetic behavior in the studied media. In contrast to the warfarin composite with unmodified silica, the drug release from the composite with mercaptopropyl modified silica follows zero order kinetics for 24 h irrespective to the release medium pH due to mixed mechanism (duffusion + degradation and/or disintegration of silica matrix). The obtained results showed that warfarin - silica sol-gel composites have a potential application for the development of novel oral formulation of the drug with controlled delivery. Copyright© Bentham Science Publishers; For any queries, please email at epub@benthamscience.org.
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.
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).
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.
Integrating sol-gel with cold plasmas modified porous polycaprolactone membranes for the drug-release of silver-sulfadiazine and ketoprofen

NASA Astrophysics Data System (ADS)

Mangindaan, Dave; Chen, Chao-Ting; Wang, Meng-Jiy

2012-12-01

A controlled release system composed of surface modified porous polycaprolactone (PCL) membranes combined with a layer of tetraorthosilicate (TEOS)-chitosan sol-gel was reported in this study. PCL is a hydrophobic, semi-crystalline, and biodegradable polymer with a relatively slow degradation rate. The drugs chosen for release experiments were silver-sulfadiazine (AgSD) and ketoprofen which were impregnated in the TEOS-chitosan sol-gel. The surface modification was achieved by O2 plasma and the surfaces were characterized by water contact angle (WCA) measurements, atomic force microscope (AFM), scanning electron microscope and electron spectroscopy for chemical analysis (ESCA). The results showed that the release of AgSD on O2 plasma treated porous PCL membranes was prolonged when compared with the pristine sample. On the contrary, the release rate of ketoprofen revealed no significant difference on pristine and plasma treated PCL membranes. The prepared PCL membranes showed good biocompatibility for the wound dressing biomaterial applications.
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
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.
One-step sol-gel imprint lithography for guided-mode resonance structures.

PubMed

Huang, Yin; Liu, Longju; Johnson, Michael; C Hillier, Andrew; Lu, Meng

2016-03-04

Guided-mode resonance (GMR) structures consisting of sub-wavelength periodic gratings are capable of producing narrow-linewidth optical resonances. This paper describes a sol-gel-based imprint lithography method for the fabrication of submicron 1D and 2D GMR structures. This method utilizes a patterned polydimethylsiloxane (PDMS) mold to fabricate the grating coupler and waveguide for a GMR device using a sol-gel thin film in a single step. An organic-inorganic hybrid sol-gel film was selected as the imprint material because of its relatively high refractive index. The optical responses of several sol-gel GMR devices were characterized, and the experimental results were in good agreement with the results of electromagnetic simulations. The influence of processing parameters was investigated in order to determine how finely the spectral response and resonant wavelength of the GMR devices could be tuned. As an example potential application, refractometric sensing experiments were performed using a 1D sol-gel device. The results demonstrated a refractive index sensitivity of 50 nm/refractive index unit. This one-step fabrication process offers a simple, rapid, and low-cost means of fabricating GMR structures. We anticipate that this method can be valuable in the development of various GMR-based devices as it can readily enable the fabrication of complex shapes and allow the doping of optically active materials into sol-gel thin film.
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...

Effects of ion irradiation on the mechanical properties of SiNa wO xC yH z sol-gel derived thin films

NASA Astrophysics Data System (ADS)

Lucca, D. A.; Qi, Y.; Harriman, T. A.; Prenzel, T.; Wang, Y. Q.; Nastasi, M.; Dong, J.; Mehner, A.

2010-10-01

A study of the effects of ion irradiation of hybrid organic/inorganic modified silicate thin films on their mechanical properties is presented. NaOH catalyzed SiNa wO xC yH z thin films were synthesized by sol-gel processing from tetraethylorthosilicate (TEOS) and methyltriethoxysilane (MTES) precursors and spin-coated onto Si substrates. After drying at 300 °C, the films were irradiated with 125 keV H + or 250 keV N 2+ at fluences ranging from 1 × 10 14 to 2.5 × 10 16 ions/cm 2. Nanoindentation was used to characterize the films. Changes in hardness and reduced elastic modulus were examined as a function of ion fluence and irradiating species. The resulting increases in hardness and reduced elastic modulus are compared to similarly processed acid catalyzed silicate thin films.
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%.
Ceria nanoparticles vis-à-vis cerium nitrate as corrosion inhibitors for silica-alumina hybrid sol-gel coating

NASA Astrophysics Data System (ADS)

Lakshmi, R. V.; Aruna, S. T.; Sampath, S.

2017-01-01

The present work provides a comparative study on the corrosion protection efficiency of defect free sol-gel hybrid coating containing ceria nanoparticles and cerium nitrate ions as corrosion inhibitors. Less explored organically modified alumina-silica hybrid sol-gel coatings are synthesized from 3-glycidoxypropyltrimethoxysilane and aluminium-tri-sec-butoxide. The microemulsion derived nanoparticles and the hybrid coatings are characterized and compared with coatings containing cerium nitrate. Corrosion inhibiting capability is assessed using electrochemical impedance spectroscopy. Scanning Kelvin probe measurements are also conducted on the coatings for identifying the apparent corrosion prone regions. Detailed X-ray photoelectron spectroscopy (XPS) analysis is carried out to comprehend the bonding and corrosion protection rendered by the hybrid coatings.
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).
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.
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.
Sol-gel optics for biomeasurements

NASA Astrophysics Data System (ADS)

Lechna-Marczynska, Monika I.; Podbielska, Halina; Ulatowska-Jarza, Agnieszka; Holowacz, Iwona; Andrzejewski, Damian

2001-10-01

Sol-gel technique is a method for producing of glass-like materials without involving a melting process. Organic compounds such as alcoholates of silicon, sodium or calcium can be used. The irregular non-crystalline network forms a gel structure where the metallic atoms are bonded to oxygen atoms. Low-temperature treatment turns this gel into an inorganic glass-like structure. There are numbers of applications of these materials that can be produced in various forms and shapes. Here, silica based sol-gel bulks and thin films optodes for biomedical applications will be presented.
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.
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.
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).
Preparation, characterization, and biological properties of organic-inorganic nanocomposite coatings on titanium substrates prepared by sol-gel.

PubMed

Catauro, Michelina; Bollino, Flavia; Papale, Ferdinando

2014-02-01

When surface-reactive (bioactive) coatings are applied to medical implants by means of the sol-gel dip-coating technique, the biological proprieties of the surface of the implant can be locally modified to match the properties of the surrounding tissues to provide a firm fixation of the implant. The aim of this study has been to synthesize, via sol-gel, organoinorganic nanoporous materials and to dip-coat a substrate to use in dental applications. Different systems have been prepared consisting of an inorganic zirconium-based matrix, in which a biodegradable polymer, the poly-ε-caprolactone was incorporated in different percentages. The materials synthesized by the sol-gel process, before gelation, when they were still in sol phase, have been used to coat a titanium grade 4 (Ti-4) substrate to change its surface biological properties. Thin films have been obtained by means of the dip-coating technique. A microstructural analysis of the obtained coatings was performed using scanning electron microscopy (SEM) and Fourier transform infrared spectroscopy. The biological proprieties have been investigated by means of tests in vitro. The bone-bonding capability of the nanocomposite films has been evaluated by examining the appearance of apatite on their surface when plunged in a simulated body fluid (SBF) with ion concentrations nearly equal to those of human blood plasma. The examination of apatite formation on the nanocomposites, after immersion in SBF, has been carried out by SEM equipped with energy-dispersive X-ray spectroscopy. To evaluate cells-materials interaction, human osteosarcoma cell line (Saos-2) has been seeded on specimens and cell vitality evaluated by WST-8 assay. © 2013 Wiley Periodicals, Inc.
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.
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.
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.
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.
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.
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.
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.
A novel l-leucine modified Sol-Gel-Carbon electrode for simultaneous electrochemical detection of homovanillic acid, dopamine and uric acid in neuroblastoma diagnosis.

PubMed

Khamlichi, Redouan El; Bouchta, Dounia; Anouar, El Hassane; Atia, Mounia Ben; Attar, Aisha; Choukairi, Mohamed; Tazi, Saloua; Ihssane, Raissouni; Faiza, Chaoukat; Khalid, Draoui; Khalid, Riffi Temsamani

2017-02-01

Neuroblastoma is a pediatric neuroblastic tumor arising in the sympathetic nervous crest cells. A high grade of Neuroblastoma is characterized by a high urinary excretion of homovanillic acid and dopamine. In this work l-leucine modified Sol-Gel-Carbon electrode was used for a sensitive voltammetric determination of homovanillic acid and dopamine in urine. The electrochemical response characteristics were investigated by cyclic and differential pulse voltammetry; the modified electrode has shown an increase in the effective area of up to 40%, a well-separated oxidation peaks and an excellent electrocatalytic activity. High sensitivity and selectivity in the linear range of 0,4-100μML -1 of homovanillic acid and 10-120μML -1 of dopamine were also obtained. Moreover, a sub-micromolar limit of detection of 0.1μM for homovanillic acid and 1.0μM for the dopamine was achieved. Indeed, high reproducibility with simple preparation and regeneration of the electrode surface made this electrode very suitable for the determination of homovanillic acid and dopamine in pharmaceutical and clinical preparations. The mechanism of homovanillic acid and the electrochemical oxidation at l-leucine modified Sol-Gel-Carbon electrode is described out the B3P86/6-31+G(d,p) level of theory as implemented in Gaussian software. Copyright © 2016 Elsevier B.V. All rights reserved.
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.

Secondary Crystal Growth on a Cracked Hydrotalcite-Based Film Synthesized by the Sol-Gel Method.

PubMed

Lee, Wooyoung; Lee, Chan Hyun; Lee, Ki Bong

2016-05-02

The sol-gel synthesis method is an attractive technology for the fabrication of ceramic films due to its preparation simplicity and ease of varying the metal composition. However, this technique presents some limitations in relation to the film thickness. Notably, when the film thickness exceeds the critical limit, large tensile stresses occur, resulting in a cracked morphology. In this study, a secondary crystal growth method was introduced as a post-treatment process for Mg/Al hydrotalcite-based films synthesized by the sol-gel method, which typically present a cracked morphology. The cracked hydrotalcite-based film was hydrothermally treated for the secondary growth of hydrotalcite crystals. In the resulting film, hydrotalcite grew with a vertical orientation, and the gaps formed during the sol-gel synthesis were filled with hydrotalcite after the crystal growth. The secondary crystal growth method provides a new solution for cracked ceramic films synthesized by the sol-gel method.
Effects of ion irradiation on the surface mechanical behavior of hybrid sol-gel derived silicate thin films

NASA Astrophysics Data System (ADS)

Ghisleni, Rudy

A study on the effects of ion irradiation on the surface mechanical behavior of hybrid sol-gel derived thin films has been performed. Hybrid organic/inorganic modified silicate thin films were synthesized by sol-gel processing from tetraethoxysilane (TEOS) and methyltriethoxysilane (MTES) precursors and spin-coated onto (100) Si substrates. The synthesized films were investigated by nanoindentation, photoluminescence spectroscopy, and Raman spectroscopy. Hybrid TEOS/MTES sol-gel films modified by ion irradiation with deposited electronic energies of 1.87 x 1025 eV/cm3 or higher showed higher values of reduced elastic modulus and hardness than 800°C heat treated films. Thus, ion irradiation was found to be an effective means in converting the polymer sol into ceramic type coatings. The ions used in this study were Cu2+, N2+, Si+, O+, N+, He+, and H+, with incident energies ranging from 100 keV to 2 MeV, and fluences ranging from 1 x 1014 to 1 x 1017 ions/cm2. Both the reduced elastic modulus and hardness were seen to increase monotonically with the increase in ion fluence, with an observed maximum hardness of 7.7 GPa (an unirradiated film hardness was 0.4 GPa) and a maximum reduced elastic modulus of 84.0 GPa (an unirradiated film reduced elastic modulus was 7.1 GPa) for 250 keV N2+ irradiation with a 5 x 1016 ions/cm2 fluence. The electronic stopping power was found to be principally responsible for the film hardening, while the role of nuclear stopping power was minimal. A monotonic increase in hardness with increase in electronic energy deposited to the film surface was found. A model describing the hardening of ion irradiated films was developed. This model characterizes the hardening effectiveness of the ion species considered by two parameters: the constant hardening cross-section and the hardening coefficient. Where the hardening cross-section represents the cross-sectional area hardened by the interaction of an incident ion with the target, and the hardening coefficient represents an index of the cross-sectional area gradient as a function of fluence. The increase in hardness of hybrid sol-gel films following ion irradiation was linked to structural changes. Ion irradiation results in a cross-linked silica film as well as the segregation of amorphous carbon clusters, both of which contributed to increase the mechanical properties of the films.
Process of forming a sol-gel/metal hydride composite

DOEpatents

Congdon, James W [Aiken, SC

2009-03-17

An external gelation process is described which produces granules of metal hydride particles contained within a sol-gel matrix. The resulting granules are dimensionally stable and are useful for applications such as hydrogen separation and hydrogen purification. An additional coating technique for strengthening the granules is also provided.
Chemical Processing of Nanostructured Coatings

DTIC Science & Technology

2000-01-01

increasing particle loading in sol-gel process (8-10). This approach involved dispersing large ceramic powders in sol-gel solution, and the mixture...the high loading of ceramic powders. One way to prepare thicker coatings is to add powders into the sol. This helps to reduce the capillary stresses...thickness that range between 2 and 4 microns. In order to investigate the nature and origin of the textured region of the coatings, GIXS was used to
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.
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.
Polymer modified sol-gel materials for photochromic applications

NASA Astrophysics Data System (ADS)

Janik, Ryszard; Kucharski, Stanislaw

2006-08-01

The chromophoric materials were prepared by copolymerization of various methacrylic monomers. The incorporation of the chromophore groups was done by coupling reaction of diazonium salts of the sulfonamide such as: sulfomethazine or sulfisomidine). The copolymers having free OH groups were able to react with 3-triethoxypropyl isocyanate forming intermediates used to prepare hybrid transparent films by sol-gel technique. The films of both copolymers as well as of hybrid sol-gel structures showed photochromic properties via trans-cis isomerization of the diazo groups. The absorption maximum of the trans form was ca. 435-445 nm depending on chemical composition of the material. Illumination of the films with coherent laser beams (two-beam coupling) resulted in formation of diffraction grating. The diffraction efficiency reached 4-5 % and refractive index modulation was in the range up to 0.0032.
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
Hydroxyapatite, fluor-hydroxyapatite and fluorapatite produced via the sol-gel method. Optimisation, characterisation and rheology.

PubMed

Tredwin, Christopher J; Young, Anne M; Georgiou, George; Shin, Song-Hee; Kim, Hae-Won; Knowles, Jonathan C

2013-02-01

Currently, most titanium implant coatings are made using hydroxyapatite and a plasma spraying technique. There are however limitations associated with plasma spraying processes including poor adherence, high porosity and cost. An alternative method utilising the sol-gel technique offers many potential advantages but is currently lacking research data for this application. It was the objective of this study to characterise and optimise the production of Hydroxyapatite (HA), fluorhydroxyapatite (FHA) and fluorapatite (FA) using a sol-gel technique and assess the rheological properties of these materials. HA, FHA and FA were synthesised by a sol-gel method. Calcium nitrate and triethylphosphite were used as precursors under an ethanol-water based solution. Different amounts of ammonium fluoride (NH4F) were incorporated for the preparation of the sol-gel derived FHA and FA. Optimisation of the chemistry and subsequent characterisation of the sol-gel derived materials was carried out using X-ray Diffraction (XRD) and Differential Thermal Analysis (DTA). Rheology of the sol-gels was investigated using a viscometer and contact angle measurement. A protocol was established that allowed synthesis of HA, FHA and FA that were at least 99% phase pure. The more fluoride incorporated into the apatite structure; the lower the crystallisation temperature, the smaller the unit cell size (changes in the a-axis), the higher the viscosity and contact angle of the sol-gel derived apatite. A technique has been developed for the production of HA, FHA and FA by the sol-gel technique. Increasing fluoride substitution in the apatite structure alters the potential coating properties. Crown Copyright © 2012. Published by Elsevier Ltd. All rights reserved.
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
Preparation and Characterisation of Hydroxyapatite Coatings on Nanotubular TiO2 Surface Obtained by Sol-Gel Process.

PubMed

Shin, Jin-Ho; Kim, Jung-Hwa; Koh, Jeong-Tae; Lim, Hyun-Pil; Oh, Gye-Jeong; Lee, Seok-Woo; Lee, Kwang-Min; Yun, Kwi-Dug; Park, Sang-Won

2015-08-01

Hydroxyapatite (HA) coating on titanium dioxide (TiO2) nanotubular surface has been developed to complement the defects of both TiO2 and HA. A sol-gel processing technique was used to coat HA on TiO2 nanotubular surface. All the titanium discs were blasted with resorbable blast media (RBM). RBM-blasted Ti surface, anodized Ti surface, and sol-gel HA coating on the anodized Ti surface were prepared. The characteristics of samples were observed using scanning electron microscopy and X-ray photoemission spectroscopy. Biologic responses were evaluated with human osteosarcoma MG63 cells in vitro. The top of the TiO2 nanotubes was not completely covered by HA particles when the coating time was less than 60 sec. It was demonstrated the sol-gel derived HA film was well-crystallized and this enhanced biologic responses in early stage cell response.
Cellulose-silica/gold nanomaterials for electronic applications.

PubMed

Kim, Gwang-Hoon; Ramesh, Sivalingam; Kim, Joo-Hyung; Jung, Dongsoo; Kim, Heung Soo

2014-10-01

Cellulose and one dimensional nano-material composite has been investigated for various industrial applications due to their optical, mechanical and electrical properties. In present investigation, cellulose/silica and silica-gold hybrid biomaterials were prepared by sol-gel covalent cross-linking process. The tetraethoxysiliane (TEOS) and gold precursors and γ-aminopropyltriethoxysilane (γ-APTES) as coupling agent were used for sol-gel cross-linking process. The chemical and morphological properties of cellulose/silica and cellulose/silica-gold nano-materials via covalent cross-linking hybrids were confirmed by FTIR, XRD, SEM, and TEM analysis. In the sol-gel process, the inorganic particles were dispersed in the cellulose host matrix at the nanometer scale, bonding to the cellulose through the covalent bonds.
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.
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
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.
Effects of sol-gel processed silica coating on bond strength of resin cements to glass-infiltrated alumina ceramic.

PubMed

Xie, Haifeng; Wang, Xiaozu; Wang, Yu; Zhang, Feimin; Chen, Chen; Xia, Yang

2009-02-01

The aim of this study was to verify the effects of sol-gel processed silica coating on the bond strength between resin cement and glass-infiltrated aluminum oxide ceramic. Silica coatings were prepared on glass-infiltrated aluminum oxide ceramic surface via the sol-gel process. Atomic Force Microscope (AFM), Fourier Transmission Infrared spectrum (FTIR), and Energy Dispersive X-ray Spectroscopy (EDS) were used for coating characterization. Forty-eight blocks of glass-infiltrated aluminum oxide ceramic were fabricated. The ceramic surfaces were polished following sandblasting. Three groups of specimens (16 for each group) with different surface treatment were prepared. Group P: no treatment; group PO: treated with silane solution; group PTO: silica coating via sol-gel process, followed by silane application. Composite cylinders were luted with resin cement to the test specimens. Half of the specimens in each group were stored in distilled water for 24 h and the other half were stored in distilled water for 30 days before shear loading in a universal testing machine until failure. Selected ceramic surfaces were analyzed to identify the failure mode using a scanning electron microscopy (SEM). Nanostructured silica coatings were prepared on glass-infiltrated aluminum oxide ceramic surfaces by the sol-gel process. The silicon element on the ceramic surface increased significantly after the coating process. The mean shear bond strength values (standard deviation) before artificial aging were: group P: 1.882 +/- 0.156 MPa; group PO: 2.177 +/- 0.226 MPa; group PTO: 3.574 +/- 0.671 MPa. Statistically significant differences existed between group PTO and group P, and group PTO and groups PO. The failure mode for group P and group PO was adhesive, while group PTO was mixed. The mean shear bond strength values (standard deviation) after artificial aging were: group P: 1.594 +/- 0.111 MPa; group PO: 2.120 +/- 0.339 MPa; group PTO: 2.955 +/- 0.113 MPa. Statistically significant differences existed between each two groups after artificial aging, group P had the lowest bond durability, and group PTO had the highest bond durability. The sol-gel process is an effective way to prepare silica coating on dental glass-infiltrated alumina ceramic. Sol-gel processed silica coating can improve the resin bond strength of glass-infiltrated alumina ceramic.
Effect of substrate surface treatment on electrochemically assisted photocatalytic activity of N-S co-doped TiO2 films

NASA Astrophysics Data System (ADS)

Parada-Gamboa, N. J.; Pedraza-Avella, J. A.; Meléndez, A. M.

2017-01-01

To investigate whether different metal surface treatments, performed on meshes of stainless steel 304 and titanium, affect the photocatalytic activity (PCA) of supported modified anodic TiO2 films, metallic substrates were coated with titanium isopropoxide sol-gel precursor modified with thiourea. Substrates were pretreated by some of the following techniques: a) sandblasting, b) pickling, c) hydroxylation and d) passivation. The as-prepared electrode materials were characterized by X-ray photoelectron spectroscopy (XPS), field emission scanning electron microscopy (FESEM), and voltammetry in the dark and under light UVA irradiation. PCA of modified N-S-TiO2 electrodes was evaluated by electrochemically assisted photocatalytic degradation of methyl orange. The results of XPS revealed that N and S were incorporated into the lattice of TiO2. FESEM showed that surface roughness and thickness of films varies depending on surface treatment. Voltammetric and XPS characterization of N-S co-doped TiO2 films supported on stainless steel revealed that their surface contains alpha-Fe2O3/FeOOH. Accordingly, iron contamination of the films coming from stainless steel was detrimental to the degradation of methyl orange. Prior to sol-gel coating process, sandblasting followed by nitric acid passivation for stainless steel or hydrofluoric acid pickling process in the case of titanium improved the PCA of N-S co-doped TiO2 films.
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.
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.
A Comparative Study of Phosphoric Acid-doped m-PBI Membranes

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

Perry, Kelly A; More, Karren Leslie; Payzant, E Andrew

2014-01-01

Phosphoric acid (PA)-doped m-polybenzimidazole (PBI) membranes used in high temperature fuel cells and hydrogen pumps were prepared by a conventional imbibing process and a sol-gel fabrication process. A comparative study was conducted to investigate the critical properties of PA doping levels, ionic conductivities, mechanical properties, and molecular ordering. This systematic study found that sol-gel PA-doped m-PBI membranes were able to absorb higher acid doping levels and to achieve higher ionic conductivities than conventionally imbibed membranes when treated in an equivalent manner. Even at similar acid loadings, the sol-gel membranes exhibited higher ionic conductivities. Heat treatment of conventionally imbibed membranes withmore » 29wt% solids caused a significant reduction in mechanical properties; conversely, sol-gel membranes exhibited an enhancement in mechanical properties. From X-ray structural studies and atomistic simulations, both conventionally imbibed and sol-gel membranes exhibited d-spacings of 3.5 and 4.6 , which were tentatively attributed to parallel ring stacking and staggered side-to-side packing, respectively, of the imidazole rings in these aromatic hetercyclic polymers. An anisotropic staggered side-to-side chain packing present in the conventional membranes may be root to the reduction in mechanical properties.« less

Effect of calcium source on structure and properties of sol-gel derived bioactive glasses.

PubMed

Yu, Bobo; Turdean-Ionescu, Claudia A; Martin, Richard A; Newport, Robert J; Hanna, John V; Smith, Mark E; Jones, Julian R

2012-12-18

The aim was to determine the most effective calcium precursor for synthesis of sol-gel hybrids and for improving homogeneity of sol-gel bioactive glasses. Sol-gel derived bioactive calcium silicate glasses are one of the most promising materials for bone regeneration. Inorganic/organic hybrid materials, which are synthesized by incorporating a polymer into the sol-gel process, have also recently been produced to improve toughness. Calcium nitrate is conventionally used as the calcium source, but it has several disadvantages. Calcium nitrate causes inhomogeneity by forming calcium-rich regions, and it requires high temperature treatment (>400 °C) for calcium to be incorporated into the silicate network. Nitrates are also toxic and need to be burnt off. Calcium nitrate therefore cannot be used in the synthesis of hybrids as the highest temperature used in the process is typically 40-60 °C. Therefore, a different precursor is needed that can incorporate calcium into the silica network and enhance the homogeneity of the glasses at low (room) temperature. In this work, calcium methoxyethoxide (CME) was used to synthesize sol-gel bioactive glasses with a range of final processing temperatures from 60 to 800 °C. Comparison is made between the use of CME and calcium chloride and calcium nitrate. Using advanced probe techniques, the temperature at which Ca is incorporated into the network was identified for 70S30C (70 mol % SiO(2), 30 mol % CaO) for each of the calcium precursors. When CaCl(2) was used, the Ca did not seem to enter the network at any of the temperatures used. In contrast, Ca from CME entered the silica network at room temperature, as confirmed by X-ray diffraction, (29)Si magic angle spinning nuclear magnetic resonance spectroscopy, and dissolution studies. CME should be used in preference to calcium salts for hybrid synthesis and may improve homogeneity of sol-gel glasses.
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.
Nanocrystal/sol-gel nanocomposites

DOEpatents

Klimov, Victor L.; Petruska, Melissa A.

2010-05-25

The present invention is directed to a process for preparing a solid composite having colloidal nanocrystals dispersed within a sol-gel matrix, the process including admixing colloidal nanocrystals with an amphiphilic polymer including hydrophilic groups selected from the group consisting of --COOH, --OH, --SO.sub.3H, --NH.sub.2, and --PO.sub.3H.sub.2 within a solvent to form an alcohol-soluble colloidal nanocrystal-polymer complex, admixing the alcohol-soluble colloidal nanocrystal-polymer complex and a sol-gel precursor material, and, forming the solid composite from the admixture. The present invention is also directed to the resultant solid composites and to the alcohol-soluble colloidal nanocrystal-polymer complexes.
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.
Titanium modified with layer-by-layer sol-gel tantalum oxide and an organodiphosphonic acid: a coating for hydroxyapatite growth.

PubMed

Arnould, C; Volcke, C; Lamarque, C; Thiry, P A; Delhalle, J; Mekhalif, Z

2009-08-15

Titanium and its alloys are widely used in surgical implants due to their appropriate properties like corrosion resistance, biocompatibility, and load bearing. Unfortunately when metals are used for orthopedic and dental implants there is the possibility of loosening over a long period of time. Surface modification is a good way to counter this problem. A thin tantalum oxide layer obtained by layer-by-layer (LBL) sol-gel deposition on top of a titanium surface is expected to improve biocorrosion resistance in the body fluid, biocompatibility, and radio-opacity. This elaboration step is followed by a modification of the tantalum oxide surface with an organodiphosphonic acid self-assembled monolayer, capable of chemically binding to the oxide surface, and also improving hydroxyapatite growth. The different steps of this proposed process are characterized by surfaces techniques like contact angle, X-ray photoelectron spectroscopy (XPS), and atomic force microscopy (AFM).
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.
Method to produce alumina aerogels having porosities greater than 80 percent

DOEpatents

Poco, John F.; Hrubesh, Lawrence W.

2003-09-16

A two-step method for producing monolithic alumina aerogels having porosities of greater than 80 percent. Very strong, very low density alumina aerogel monoliths are prepared using the two-step sol-gel process. The method of preparing pure alumina aerogel modifies the prior known sol method by combining the use of substoichiometric water for hydrolysis, the use of acetic acid to control hydrolysis/condensation, and high temperature supercritical drying, all of which contribute to the formation of a polycrystalline aerogel microstructure. This structure provides exceptional mechanical properties of the alumina aerogel, as well as enhanced thermal resistance and high temperature stability.
Synthesis of Ba 0.6K 0.4BiO 3 and BaPb 0.75Bi 0.25O 3 superconductors by sol-gel process

NASA Astrophysics Data System (ADS)

Rao, G. V. Rama; Varadaraju, U. V.; Mannan, S. L.

1994-12-01

We have synthesised Ba 0.6K 0.4BiO 3 (BKB) and BaPb 1-xBi xO 3-y compounds by sol-gel process. IR spectra of gels indicated the bridging type of bonding between metal carboxylates leading to the formation of homogeneous gels. BKB and BaPb 0.75Bi 0.25O 3 compounds exhibited sharp superconducting transitions from R-T and χ-T measurements indicating excellent homogeneity of the samples
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.
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.
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.
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.
Development of Novel Warfarin-Silica Composite for Controlled Drug Release.

PubMed

Parfenyuk, Elena V; Dolinina, Ekaterina S

2017-04-01

The work is devoted to synthesis and study of warfarin composites with unmodified, methyl and phenyl modified silica in order to develop controlled release formulation of the anticoagulant. The composites were prepared by two routes, adsorption and sol-gel, and characterized with FTIR spectroscopy, dynamic light scattering and DSC methods. The drug release behavior from the composites in media with pH 1.6, 6.8 and 7.4 was analyzed in vitro. The release kinetics of the warfarin - silica composites prepared by the two routes was compared among each other and with analogous silica composites with water soluble drug molsidomine. The comparative analysis showed that in general the kinetic regularities and mechanisms of release for both drugs are similar and determined by nonuniform distribution of the drugs over the silica matrixes and stability of the matrixes in the studied media for the adsorbed composites and uniformly distributed drug and more brittle structure for the sol-gel composites. The sol-gel composite of warfarin - phenyl modified silica is perspective for further development of novel warfarin formulation with controlled release because it releases warfarin according to zero-order kinetic law with approximately equal rate in the media imitating different segments of gastrointestinal tract.
Sol-gel-Derived nano-sized double layer anti-reflection coatings (SiO2/TiO2) for low-cost solar cell fabrication.

PubMed

Lee, Seung Jun; Hur, Man Gyu; Yoon, Dae Ho

2013-11-01

We investigate nano-sized double layer anti-reflection coatings (ARCs) using a TiO2 and SiO2 sol-gel solution process for mono-crystalline silicon solar cells. The process can be easily adapted for spraying sol-gel coatings to reduce manufacturing cost. The spray-coated SiO2/TiO2 nano-sized double layer ARCs were deposited on mono-crystalline silicon solar cells, and they showed good optical properties. The spray coating process is a lower-cost fabrication process for large-scale coating than vacuum deposition processes such as PECVD. The measured average optical reflectance (300-1200 nm) was about approximately 8% for SiO2/TiO2 nano-sized double layer ARCs. The electrical parameters of a mono-crystalline silicon solar cell and reflection losses show that the SiO2/TiO2 stacks can improve cell efficiency by 0.2% compared to a non-coated mono-crystalline silicon solar cell. In the results, good correlation between theoretical and experimental data was obtained. We expect that the sol-gel spray-coated mono-crystalline silicon solar cells have high potential for low-cost solar cell fabrication.
The impact of thermal treatment conditions on the formation of crystalline structure of Ce-Zr-oxide composite obtained by a modified sol-gel technique

NASA Astrophysics Data System (ADS)

Trusova, E. A.; Khrushcheva, A. A.; Shvorneva, L. I.

2012-02-01

We present the results of the modified sol-gel synthesis of ultrafine ceria-doped zirconia powder for medical ceramics (implants) and catalytic purposes (environmental catalysis and petrochemistry). Special attention has been paid to study the influence of thermal treatment on crystallite size and crystal lattice parameters of zirconia doped by ceria. Zirconyl chloride and cerium nitrate were used as metal sources, and tetraethylammonium hydroxide (TEAH) was used as a sol stabilizer at molar ratio TEAH/Σ (Ce + Zr) equal to 0.5. It was proved that zirconium and cerium practically completely were included in the obtained solid solutions, since their phase compositions fully correspond to initial quantities of cerium and zirconium in reaction mixture. It was shown that average crystallite size of the obtained powders did not exceed 75Å, and the powders were resistant to thermal treatment. It was established that stabilization of the crystal lattice of ZrO2 occurs through formation of a cubic ceria sublattice.
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.
Sol-gel coating of inorganic nanostructures with resorcinol-formaldehyde resin.

PubMed

Li, Na; Zhang, Qiao; Liu, Jian; Joo, Jibong; Lee, Austin; Gan, Yang; Yin, Yadong

2013-06-07

A general sol-gel process has been developed to form a coating of resorcinol-formaldehyde (RF) resin on inorganic nanostructures of various compositions and morphologies. The RF shell can be conveniently converted into carbon through high temperature carbonization under an inert atmosphere.
Metal-silica sol-gel materials

NASA Technical Reports Server (NTRS)

Stiegman, Albert E. (Inventor)

2002-01-01

The present invention relates to a single phase metal-silica sol-gel glass formed by the co-condensation of a transition metal with silicon atoms where the metal atoms are uniformly distributed within the sol-gel glass as individual metal centers. Any transition metal may be used in the sol-gel glasses. The present invention also relates to sensor materials where the sensor material is formed using the single phase metal-silica sol-gel glasses. The sensor materials may be in the form of a thin film or may be attached to an optical fiber. The present invention also relates to a method of sensing chemicals using the chemical sensors by monitoring the chromatic change of the metal-silica sol-gel glass when the chemical binds to the sensor. The present invention also relates to oxidation catalysts where a metal-silica sol-gel glass catalyzes the reaction. The present invention also relates to a method of performing oxidation reactions using the metal-silica sol-gel glasses. The present invention also relates to organopolymer metal-silica sol-gel composites where the pores of the metal-silica sol-gel glasses are filled with an organic polymer polymerized by the sol-gel glass.
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.
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.

The Effect of Different Coupling Agents on Nano-ZnO Materials Obtained via the Sol-Gel Process.

PubMed

Purcar, Violeta; Şomoghi, Raluca; Niţu, Sabina Georgiana; Nicolae, Cristian-Andi; Alexandrescu, Elvira; Gîfu, Ioana Cătălina; Gabor, Augusta Raluca; Stroescu, Hermine; Ianchiş, Raluca; Căprărescu, Simona; Cinteză, Ludmila Otilia

2017-12-12

Hybrid nanomaterials based on zinc oxide were synthesized via the sol-gel method, using different silane coupling agents: (3-glycidyloxypropyl)trimethoxysilane (GPTMS), phenyltriethoxysilane (PhTES), octyltriethoxysilane (OTES), and octadecyltriethoxysilane (ODTES). Morphological properties and the silane precursor type effect on the particle size were investigated using dynamic light scattering (DLS), environmental scanning electron microscopy (ESEM), transmission electron microscopy (TEM), thermogravimetric analysis (TGA), and X-ray diffraction (XRD). The bonding characteristics of modified ZnO materials were investigated using Fourier transform infrared spectroscopy (FTIR). The final solutions were deposited on metallic substrate (aluminum) in order to realize coatings with various wettability and roughness. The morphological studies, obtained by ESEM and TEM analysis, showed that the sizes of the ZnO nanoparticles are changed as function of silane precursor used in synthesis. The thermal stability of modified ZnO materials showed that the degradation of the alkyl groups takes place in the 300-500 °C range. Water wettability study revealed a contact angle of 142 ± 5° for the surface covered with ZnO material modified with ODTES and showed that the water contact angle increases as the alkyl chain from the silica precursor increases. These modified ZnO materials, therefore, can be easily incorporated in coatings for various applications such as anti-corrosion and anti-icing.
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
Method of making ionic liquid mediated sol-gel sorbents

DOEpatents

Malik, Abdul; Shearrow, Anne M.

2017-01-31

Ionic liquid (IL)-mediated sol-gel hybrid organic-inorganic materials present enormous potential for effective use in analytical microextraction. One obstacle to materializing this prospect arises from high viscosity of ILs significantly slowing down sol-gel reactions. A method was developed which provides phosphonium-based, pyridinium-based, and imidazolium-based IL-mediated advanced sol-gel organic-inorganic hybrid materials for capillary microextraction. Scanning electron microscopy results demonstrate that ILs can serve as porogenic agents in sol-gel reactions. IL-mediated sol-gel coatings prepared with silanol-terminated polymers provided up to 28 times higher extractions compared to analogous sol-gel coatings prepared without any IL in the sol solution. This study shows that IL-generated porous morphology alone is not enough to provide effective extraction media: careful choice of the organic polymer and the precursor with close sol-gel reactivity must be made to ensure effective chemical bonding of the organic polymer to the created sol-gel material to be able to provide the desired sorbent characteristics.
Ternary Phase-Separation Investigation of Sol-Gel Derived Silica from Ethyl Silicate 40

PubMed Central

Wang, Shengnan; Wang, David K.; Smart, Simon; Diniz da Costa, João C.

2015-01-01

A ternary phase-separation investigation of the ethyl silicate 40 (ES40) sol-gel process was conducted using ethanol and water as the solvent and hydrolysing agent, respectively. This oligomeric silica precursor underwent various degrees of phase separation behaviour in solution during the sol-gel reactions as a function of temperature and H2O/Si ratios. The solution composition within the immiscible region of the ES40 phase-separated system shows that the hydrolysis and condensation reactions decreased with decreasing reaction temperature. A mesoporous structure was obtained at low temperature due to weak drying forces from slow solvent evaporation on one hand and formation of unreacted ES40 cages in the other, which reduced network shrinkage and produced larger pores. This was attributed to the concentration of the reactive sites around the phase-separated interface, which enhanced the condensation and crosslinking. Contrary to dense silica structures obtained from sol-gel reactions in the miscible region, higher microporosity was produced via a phase-separated sol-gel system by using high H2O/Si ratios. This tailoring process facilitated further condensation reactions and crosslinking of silica chains, which coupled with stiffening of the network, made it more resistant to compression and densification. PMID:26411484
Foldable and Cytocompatible Sol-gel TiO2 Photonics

NASA Astrophysics Data System (ADS)

Li, Lan; Zhang, Ping; Wang, Wei-Ming; Lin, Hongtao; Zerdoum, Aidan B.; Geiger, Sarah J.; Liu, Yangchen; Xiao, Nicholas; Zou, Yi; Ogbuu, Okechukwu; Du, Qingyang; Jia, Xinqiao; Li, Jingjing; Hu, Juejun

2015-09-01

Integrated photonics provides a miniaturized and potentially implantable platform to manipulate and enhance the interactions between light and biological molecules or tissues in in-vitro and in-vivo settings, and is thus being increasingly adopted in a wide cross-section of biomedical applications ranging from disease diagnosis to optogenetic neuromodulation. However, the mechanical rigidity of substrates traditionally used for photonic integration is fundamentally incompatible with soft biological tissues. Cytotoxicity of materials and chemicals used in photonic device processing imposes another constraint towards these biophotonic applications. Here we present thin film TiO2 as a viable material for biocompatible and flexible integrated photonics. Amorphous TiO2 films were deposited using a low temperature (<250 °C) sol-gel process fully compatible with monolithic integration on plastic substrates. High-index-contrast flexible optical waveguides and resonators were fabricated using the sol-gel TiO2 material, and resonator quality factors up to 20,000 were measured. Following a multi-neutral-axis mechanical design, these devices exhibit remarkable mechanical flexibility, and can sustain repeated folding without compromising their optical performance. Finally, we validated the low cytotoxicity of the sol-gel TiO2 devices through in-vitro cell culture tests. These results demonstrate the potential of sol-gel TiO2 as a promising material platform for novel biophotonic devices.
Foldable and Cytocompatible Sol-gel TiO2 Photonics

PubMed Central

Li, Lan; Zhang, Ping; Wang, Wei-Ming; Lin, Hongtao; Zerdoum, Aidan B.; Geiger, Sarah J.; Liu, Yangchen; Xiao, Nicholas; Zou, Yi; Ogbuu, Okechukwu; Du, Qingyang; Jia, Xinqiao; Li, Jingjing; Hu, Juejun

2015-01-01

Integrated photonics provides a miniaturized and potentially implantable platform to manipulate and enhance the interactions between light and biological molecules or tissues in in-vitro and in-vivo settings, and is thus being increasingly adopted in a wide cross-section of biomedical applications ranging from disease diagnosis to optogenetic neuromodulation. However, the mechanical rigidity of substrates traditionally used for photonic integration is fundamentally incompatible with soft biological tissues. Cytotoxicity of materials and chemicals used in photonic device processing imposes another constraint towards these biophotonic applications. Here we present thin film TiO2 as a viable material for biocompatible and flexible integrated photonics. Amorphous TiO2 films were deposited using a low temperature (<250 °C) sol-gel process fully compatible with monolithic integration on plastic substrates. High-index-contrast flexible optical waveguides and resonators were fabricated using the sol-gel TiO2 material, and resonator quality factors up to 20,000 were measured. Following a multi-neutral-axis mechanical design, these devices exhibit remarkable mechanical flexibility, and can sustain repeated folding without compromising their optical performance. Finally, we validated the low cytotoxicity of the sol-gel TiO2 devices through in-vitro cell culture tests. These results demonstrate the potential of sol-gel TiO2 as a promising material platform for novel biophotonic devices. PMID:26344823
Foldable and Cytocompatible Sol-gel TiO2 Photonics.

PubMed

Li, Lan; Zhang, Ping; Wang, Wei-Ming; Lin, Hongtao; Zerdoum, Aidan B; Geiger, Sarah J; Liu, Yangchen; Xiao, Nicholas; Zou, Yi; Ogbuu, Okechukwu; Du, Qingyang; Jia, Xinqiao; Li, Jingjing; Hu, Juejun

2015-09-07

Integrated photonics provides a miniaturized and potentially implantable platform to manipulate and enhance the interactions between light and biological molecules or tissues in in-vitro and in-vivo settings, and is thus being increasingly adopted in a wide cross-section of biomedical applications ranging from disease diagnosis to optogenetic neuromodulation. However, the mechanical rigidity of substrates traditionally used for photonic integration is fundamentally incompatible with soft biological tissues. Cytotoxicity of materials and chemicals used in photonic device processing imposes another constraint towards these biophotonic applications. Here we present thin film TiO2 as a viable material for biocompatible and flexible integrated photonics. Amorphous TiO2 films were deposited using a low temperature (<250 °C) sol-gel process fully compatible with monolithic integration on plastic substrates. High-index-contrast flexible optical waveguides and resonators were fabricated using the sol-gel TiO2 material, and resonator quality factors up to 20,000 were measured. Following a multi-neutral-axis mechanical design, these devices exhibit remarkable mechanical flexibility, and can sustain repeated folding without compromising their optical performance. Finally, we validated the low cytotoxicity of the sol-gel TiO2 devices through in-vitro cell culture tests. These results demonstrate the potential of sol-gel TiO2 as a promising material platform for novel biophotonic devices.
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.
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.
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.
Evidence of modifications of micellar interface in sol-gel glass

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

Catuara, C.M.; Lin, C.T.

1994-12-31

A new sol-gel procedure using micellar solutions has been developed to immobilize local anesthetic drugs in optically transparent glass. Dibucaine was selected as a direct emission probe at 77 K for determining the forms of the anesthetic drug (free base, monoprotonated, and/or diprotonated) and its location (hydrophobic core, interfacial layer or hydrophilic region) in micelles. The photophysical properties of local anesthetics obtained in gels are compared to those in solutions. During the gelation stage, the predominant drug species was identified as free base dibucaine embedded in the hydrophobic core of neutral as well as charged micelles. This observation suggests thatmore » the micellar interface was modified by the large hydrophilic gel surface during the gelation stage. The modified micellar interface allows an increase in the partition of free base dibucaine into the hydrophobic region. At the xerogel stage, however, the collapse of micellar structure provides a direct interaction of dibucaine with the acidic gel surface, leading to a formation of diprotonated dibucaine. The results are discussed in terms of molecular basis of pharmacological implications such as drug delivery, release, and transport under microencapsulation conditions.« less
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
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.
Investigation on the path process of M doped ZnO (M = Gd, Mg) via the sol-gel method from dried gel to stable nanostructure powder

NASA Astrophysics Data System (ADS)

Suharno; Soegijono, B.; Budiawanti, S.; Fadillah, L.

2017-04-01

Doping is one of the effective methods to modify the physical properties of ZnO material in order to extend its applications. An investigation on Zn1-xMxO (M = Gd, Mg and x = 0.00, 0.03) nanopowders that have been synthesized by sol-gel method and sintered at 600 °C for 2 hours was reported. The decomposition process of the dried gel system was investigated by thermal gravimetric analysis (TGA) and the nanopowders with different heating temperature were studied using FT-IR spectroscopy. The crystal structure of the nanopowders after sintering at 600 °C was obtained using X-ray diffraction (XRD). The TGA curves of the samples showed the various weight loss regions corresponding to the removal of starting materials and no weight loss was observed in the temperature range of 300 to 800 °C which corresponded to the phase-crystallization step. The FTIR spectra showed that ZnO band was assigned to the stretching frequency at 669 cm-1 while Gd/Mg doped ZnO was at 668 cm-1 and 666 cm-1. From the XRD studies, the crystal structure of the samples indicated single phase ZnO crystalline and confirmed hexagonal wurtzite structure (space group of P63mc).
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.
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.
Hybrid organic-inorganic sol-gel materials and components for integrated optoelectronics

NASA Astrophysics Data System (ADS)

Lu, Dong

On the technical platform of hybrid organic-inorganic sol-gel, the integrated optoelectronics in the forms of heterogeneous integration between the hybrid sol-gel waveguide and the high refractive index semiconductors and the nonlinear functional doping of disperse red chromophore into hybrid sol-gel is developed. The structure of hybrid sol-gel waveguide on high index semiconductor substrate is designed with BPM-CAD software. A hybrid sol-gel based on MAPTMS and TEOS suitable for lower cladding for the waveguide is developed. The multi-layer hybrid sol-gel waveguide with good mode confinement and low polarization dependence is fabricated on Si and InP. As proof of concept, a 1 x 12 beam splitter based on multimode interference is fabricated on silicon substrate. The device shows excess loss below 0.65 dB and imbalance below 0.28 dB for both TE and TM polarization. A nonlinear active hybrid sol-gel doped with disperse red 13 has been developed by simple co-solvent method. It permits high loading concentration and has low optical loss at 1550 nm. The second-order nonlinear property of the active sol-gel is induced with corona poling and studied with second harmonic generation. A 3-fold of enhancement in the poling efficiency is achieved by blue light assisted corona poling. The chromophore alignment stability is improved by reducing the free volume of the formed inorganic network from the sol-gel condensation reaction. An active sol-gel channel waveguide has been fabricated using active and passive hybrid sol-gel materials by only photopatterning and spin-coating. An amplitude modulator based on the active sol-gel containing 30 wt.% of DR13 shows an electro-optic coefficient of 14 pm/V at 1550 nm and stable operation within the observation time of 24 days.
Fluorescent Dye-doped Sol-gel Sensor for Highly Sensitive Carbon Dioxide Gas Detection below Atmospheric Concentrations

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

Dansby-Sparks, Royce N.; Jin, Jun; Mechery, Shelly J

2009-01-01

Optical fluorescence sol-gel sensors have been developed for the detection of carbon dioxide gas in the 0.03?30% range with a detection limit of 0.008% (or 80 ppm) and a quantitation limit of 0.02% (or 200 ppm) CO{sub 2}. Sol?gels were spin-coated on glass slides to create an organically modified silica-doped matrix with the 1-hydroxypyrene-3,6,8-trisulfonate (HPTS) fluorescent indicator. The luminescence intensity of the HPTS indicator (513 nm) is quenched by CO{sub 2}, which protonates the anionic form of HPTS. An ion pair technique was used to incorporate the lipophilic dye into the hydrophilic sol?gel matrix. TiO{sub 2} particles (<5 {mu}m diameter)more » were added to induce Mie scattering and increase the incident light interaction with the sensing film, thus increasing the signal-to-noise ratio. Moisture-proof overcoatings have been used to maintain a constant level of water inside the sensor films. The optical sensors are inexpensive to prepare and can be easily coupled to fiber optics for remote sensing capabilities. A fiber-optic bundle was used for the gas detection and shown to work as part of a multianalyte platform for simultaneous detection of multiple analytes. The studies reported here resulted in the development of sol?gel optical fluorescent sensors for CO{sub 2} gas with sensitivity below that in the atmosphere (ca. 387 ppm). These sensors are a complementary approach to current FT-IR measurements for real-time carbon dioxide detection in environmental applications.« less
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

Synthesis, Fabrication and Characterization of ZnO-Based Thin Films Prepared by Sol-Gel Process and H2 Gas Sensing Performance

NASA Astrophysics Data System (ADS)

Dey, Anup; Roy, Subhashis; Sarkar, Subir Kumar

2018-03-01

In this paper, an attempt is made to deposit ZnO thin films using sol-gel process followed by dip-coating method on p-silicon (100) substrates for intended application as a hydrogen gas sensor owing to the low toxic nature and thermal stability of ZnO. The thin films are annealed under annealing temperatures of 350, 450 and 550 °C for 25 min. The crystalline quality of the fabricated thin films is then analyzed by field-emission scanning electron microscopy and transmission electron microscope. The gas sensing performance analysis of ZnO thin films is demonstrated at different annealing temperatures and hydrogen gas concentrations ranging from 100 to 3000 ppm. Results obtained show that the sensitivity is significantly improved as annealing temperature increases with maximum sensitivity being achieved at 550 °C annealing temperature and operating temperature of 150 °C. Hence, the modified ZnO thin films can be applicable as H2 gas sensing device showing to the improved performance in comparison with unmodified thin-film sensor.
Silica- and germania-based dual-ligand sol-gel organic-inorganic hybrid sorbents combining superhydrophobicity and π-π interaction. The role of inorganic substrate in sol-gel capillary microextraction.

PubMed

Seyyal, Emre; Malik, Abdul

2017-04-29

Principles of sol-gel chemistry were utilized to create silica- and germania-based dual-ligand surface-bonded sol-gel coatings providing enhanced performance in capillary microextraction (CME) through a combination of ligand superhydrophobicity and π-π interaction. These organic-inorganic hybrid coatings were prepared using sol-gel precursors with bonded perfluorododecyl (PF-C 12 ) and phenethyl (PhE) ligands. Here, the ability of the PF-C 12 ligand to provide enhanced hydrophobic interaction was advantageously combined with π-π interaction capability of the PhE moiety to attain the desired sorbent performance in CME. The effect of the inorganic sorbent component on microextraction performance of was explored by comparing microextraction characteristics of silica- and germania-based sol-gel sorbents. The germania-based dual-ligand sol-gel sorbent demonstrated superior CME performance compared to its silica-based counterpart. Thermogravimetric analysis (TGA) of the created silica- and germania-based dual-ligand sol-gel sorbents suggested higher carbon loading on the germania-based sorbent. This might be indicative of more effective condensation of the organic ligand-bearing sol-gel-active chemical species to the germania-based sol-gel network (than to its silica-based counterpart) evolving in the sol solution. The type and concentration of the organic ligands were varied in the sol-gel sorbents to fine-tune extraction selectivity toward different classes of analytes. Specific extraction (SE) values were used for an objective comparison of the prepared sol-gel CME sorbents. The sorbents with higher content of PF-C 12 showed remarkable affinity for aliphatic hydrocarbons. Compared to their single-ligand sol-gel counterparts, the dual-ligand sol-gel coatings demonstrated significantly superior CME performance in the extraction of alkylbenzenes, providing up to ∼65.0% higher SE values. The prepared sol-gel CME coatings provided low ng L -1 limit of detections (LOD) (4.2-26.3 ng L -1 ) for environmentally important analytes including polycyclic aromatic hydrocarbons, ketones and aliphatic hydrocarbons. In CME-GC experiments (n = 5), the capillary-to-capillary RSD value was ∼2.1%; such a low RSD value is indicative of excellent reproducibility of the sol-gel method used for the preparation of these CME coatings. The dual-ligand sol-gel coating provided stable performance in capillary microextraction of analytes from saline samples. Copyright © 2017 Elsevier B.V. All rights reserved.
Development of an extended-range fiber optic pH sensor using evanescent wave absorption of sol-gel-entrapped pH indicators

NASA Astrophysics Data System (ADS)

Butler, Thomas M.; MacCraith, Brian D.; McDonagh, Colette M.

1995-09-01

The sol-gel process has been used to entrap pH indicators in porous glass coatings for sensor applications. This sensor is based on evanescent wave absorption using an unclad optical fiber dipcoated with the pH sensitive coating. The entrapped pH indicators show a broadening of the pH range with respect to the behavior in solution giving accurate measurement over three pH units when one indicator is used (bromophenol blue) and over six pH units (pH 3-9) when two indicators are used (bromophenol blue and bromocresol purple). The response of the pH sensor was monitored by measuring absorption at 590 nm referenced against a nonabsorbing region of the spectrum. This enabled the use of LED sources together with low cost photodiodes. The sensor displayed short response time and good repeatability. The thickness and stability of the pH sensitive coatings can be influenced by modifying the composition of the starting sol mixture. The evanescent absorption, and hence the sensitivity of the sensor, can be increased by selectively launching higher order modes in the fiber. These issues together with a full sensor characterization will be reported.
Morphology of one-time coated palladium-alumina composite membrane prepared by sol-gel process and electroless plating technique

NASA Astrophysics Data System (ADS)

Sari, R.; Dewi, R.; Pardi; Hakim, L.; Diana, S.

2018-03-01

Palladium coated porous alumina ceramic membrane tube was obtained using a combination of sol-gel process and electroless plating technique. The thickness, structure and composition of palladium-alumina composite membrane were analyzed by transmission electron microscopy (TEM), scanning electron microscopy (SEM), energy-dispersive X-ray (EDX), and atomic force microscopy (AFM). Palladium particle size was 6.18 to 7.64 nm. Palladium membrane with thickness of approximately 301.5 to 815.1 nm was formed at the outer surface of the alumina layer. EDX data confirmed the formation of palladium-alumina membrane containing 45% of palladium. From this research it shows the combination of sol-gel process and electroless plating technique with one-time coating can produce a homogeneous and smoother palladium nano layer film on alumina substrate.
Improvement of Sol-Gel Derived PbZrxTi1-xO3 Film Properties Using Thermal Press Treatment

NASA Astrophysics Data System (ADS)

Kaneda, Toshihiko; Kim, Joo-Nam; Tokumitsu, Eisuke; Shimoda, Tatsuya

2010-09-01

A thermal press treatment was introduced in the sol-gel process of PbZrxTi1-xO3 (PZT) thin films for the first time and the crystalline and electrical characteristics of the PZT films were investigated. The thermal press treatment was applied to the amorphous PZT gel film before crystallization annealing. It is found that the crystalline orientation and grain size of the PZT film fabricated with the thermal press treatment are different from those of the film fabricated by the conventional sol-gel process without the thermal press treatment, even though the crystallization conditions are exactly the same. It is demonstrated that the electrical properties, especially leakage current density and breakdown field, are significantly improved for the PZT film fabricated with the thermal press treatment. Furthermore, we also demonstrate that the fatigue property is improved by introducing the thermal press treatment.
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.
Versatile bio-ink for covalent immobilization of chimeric avidin on sol-gel substrates.

PubMed

Heikkinen, Jarkko J; Kivimäki, Liisa; Määttä, Juha A E; Mäkelä, Inka; Hakalahti, Leena; Takkinen, Kristiina; Kulomaa, Markku S; Hytönen, Vesa P; Hormi, Osmo E O

2011-10-15

A bio-ink for covalent deposition of thermostable, high affinity biotin-binding chimeric avidin onto sol-gel substrates was developed. The bio-ink was prepared from heterobifunctional crosslinker 6-maleimidohexanoic acid N-hydroxysuccinimide which was first reacted either with 3-aminopropyltriethoxysilane or 3-aminopropyldimethylethoxysilane to form silane linkers 6-maleimide-N-(3-(triethoxysilyl)propyl)hexanamide or -(ethoxydimethylsilyl)propyl)-hexanamide. C-terminal cysteine genetically engineered to chimeric avidin was reacted with the maleimide group of silane linker in methanol/PBS solution to form a suspension, which was printed on sol-gel modified PMMA film. Different concentrations of chimeric avidin and ratios between silane linkers were tested to find the best properties for the bio-ink to enable gravure or inkjet printing. Bio-ink prepared from 3-aminopropyltriethoxysilane was found to provide the highest amount of active immobilized chimeric avidin. The developed bio-ink was shown to be valuable for automated fabrication of avidin-functionalized polymer films. Copyright © 2011 Elsevier B.V. All rights reserved.
Titanium dioxide nanoparticles: Impact of increasing ionic strength during synthesis, reflux, and hydrothermal aging

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

Isley, Sara L.; Jordan, David S.; Penn, R. Lee

2009-01-08

This work investigates the role of ionic strength during synthesis, reflux, and hydrothermal aging of sol-gel synthesized titanium dioxide. Research presented here uses X-ray diffraction data and Rietveld refinements to quantify anatase, brookite, and rutile phases as functions of synthetic and aging variables. In addition, the Scherrer equation is used to obtain average crystallite sizes for each phase quantified. Results presented in this work demonstrate that the most control over the sol-gel products can be obtained by modifying the pH during hydrolysis. In addition, while varying the ionic strength during reflux and hydrothermal aging can result in enhanced control overmore » the crystalline phase and crystallite size, the most control can be achieved by varying the ionic strength during synthesis. Finally, sol-gel synthesis at low pH (-0.6) and high-chloride concentration (3 M NaCl) produced a heterogeneous sample composed of nanocrystalline anatase (3.8 nm) and rutile (2.9 nm)« less
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.
Surface chemistry and moisture sorption properties of wood coated with multifunctional alkoxysilanes by sol-gel process

Treesearch

Mandla A. Tshabalala; Peter Kingshott; Mark R. VanLandingham; David Plackett

2003-01-01

Sol-gel surface deposition of a hydrophobic polysiloxane coating on wood was accomplished by using a mixture of a low molecular weight multifunctional alkoxysilane, methyltrimethoxysilane (MTMOS), and a high molecular weight multifunctional alkoxysilane, hexadecyltrimethoxysilane (HDTMOS). Investigation of the surface chemistry and morphology of the wood specimens by...
Thermal stability of a modified sol-gel derived hydroxyapatite nanopowders

NASA Astrophysics Data System (ADS)

Herradi, S.; El Bali, B.; Khaldi, M.; Lachkar, M.

2017-03-01

Hydroxyapatite Ca10(PO4)6(OH)2 (HA) powder was successfully synthesized by a modified sol-gel method using a solution of calcium nitrate in ethanol, along with a solution of diammonium hydrogen phosphate in water and NH4OH as starting materials. The Ca/P molar ratio was maintained at 1.67. The powder was subjected to furnace and microwave heating to compare the decomposition of HA and study the crystallite sizes. It was found that microwave heated powders were pure HAP up to 230°C with absence of secondary phases. However, XRD patterns show that furnace heated powders convert completely to β-TCP when treated at 750°C and 1000°C. This result was confirmed by the absence of hydroxyl bands in the FT-IR spectra for these temperatures.
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.
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.
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.
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
Preparation and Application of Immobilized Surfactant-Modified PANi-CNT/TiO2 under Visible-Light Irradiation

PubMed Central

Yuan, Ching; Hung, Chung-Hsuang; Yuan, Chung-Shin; Li, Huei-Wen

2017-01-01

Hydrothermally and sol-gel-synthesized immobilized surfactant-modified polyaniline-carbon nanotubes/TiO2 (PANi-CNT/TiO2) photocatalysts were prepared and their application in the degradation of diethyl phthalate (DEP) under visible light at 410 nm was investigated in this sturdy. To improve the dispersion of nanoparticles and the transfer of electrons, the TiO2 surface was modified with both sodium dodecyl sulfate (SDS) and functionalized carbon nanotubes (CNT-COOH and CNT-COCl). With the addition of PANi, which was increased from 1–5%, the adsorption edge of the prepared photocatalysts shifted to 442 nm. The SDS linked the PANi polymers to achieve a thickness of coating of the film of up to 314–400 nm and 1301–1600 nm for sol-gel hydrolysis and hydrothermally-synthesized photocatalysts, respectively. An appropriate film thickness would extend the transfer path of the electrons and inhibit the recombination of the electrons and the electron-holes. The photo-degradation performance of DEP by the hydrothermally-synthesized photocatalysts was better than those by sol-gel hydrolysis. The results revealed that the hydroxyl radicals were the key oxidant in the degradation of DEP using hydrothermally-synthesized PANi-CNT/TiO2 photocatalysts. The morphology and functional groups of the raw materials of photocatalysts were characterized and a comparison of photocatalytic activity with other TiO2-based photocatalysts was also provided. PMID:28773238
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.
Luminescence of Eu(3+) doped SiO2 Thin Films and Glass Prepared by Sol-gel Technology

NASA Technical Reports Server (NTRS)

Castro, Lymari; Jia, Weiyi; Wang, Yanyun; Santiago, Miguel; Liu, Huimin

1998-01-01

Trivalent europium ions are an important luminophore for lighting and display. The emission of (5)D0 to (7)F2 transition exhibits a red color at about 610 nm, which is very attractive and fulfills the requirement for most red-emitting phosphors including lamp and cathode ray phosphorescence materials. Various EU(3+) doped phosphors have been developed, and luminescence properties have been extensively studied. On the other hand, sol-gel technology has been well developed by chemists. In recent years, applications of this technology to optical materials have drawn a great attention. Sol-gel technology provides a unique way to obtain homogeneous composition distribution and uniform doping, and the processing temperature can be very low. In this work, EU(3+) doped SiO2 thin films and glasses were prepared by sol-gel technology and their spectroscopic properties were investigated.
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.
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.

Sol-gel, One Technology by Produced Nanohybrid with Anticorrosive Properties

NASA Astrophysics Data System (ADS)

Hernández-Padrón, Genoveva; García-Garduño, Margarita V.

The evolution of nanotechnology has been allowed modify the material properties since of chemical architecture. In this work, we development nanohybrids sol-gel process, silica particles are incorporated a functionalized polymer resin (type epoxy and/or phenolic) with carboxylic groups. When the metallic plate is coating formed film ceramic glass. The incorporation this particles into to polymeric matrix, allowed to obtain performance corrosive properties. The structural characteristics of the different materials prepared, phenolic resin (RF), the resin functionalized (RFF) and its corresponding hybrids (RF-SiO2 and RFF- SiO2), were studied by infrared spectroscopy and morphological changes were analyzed by scanning electron microscopy. Then cooper plates were coated with these materials to evaluate their corrosion performance. The corrosion performance evaluation for each of these coatings RF, RFF, RE- SiO2 and RFF- SiO2 were determined by the following tests: a misty saline chamber operated under accelerated corrosive conditions for corrosion advance measurement, abrasion and adhesion.
Effects of lithium doping on microstructure, electrical properties, and chemical bonds of sol-gel derived NKN thin films

NASA Astrophysics Data System (ADS)

Lin, Chun-Cheng; Chen, Chan-Ching; Weng, Chung-Ming; Chu, Sheng-Yuan; Hong, Cheng-Shong; Tsai, Cheng-Che

2015-02-01

Highly (100/110) oriented lead-free Lix(Na0.5K0.5)1-xNbO3 (LNKN, x = 0, 0.02, 0.04, and 0.06) thin films are fabricated on Pt/Ti/SiO2/Si substrates via a sol-gel processing method. The lithium (Li) dopants modify the microstructure and chemical bonds of the LNKN films, and therefore improve their electrical properties. The optimal values of the remnant polarization (Pr = 14.3 μC/cm2), piezoelectric coefficient (d33 = 48.1 pm/V), and leakage current (<10-5 A/cm2) are obtained for a lithium addition of x = 0.04 (i.e., 4 at. %). The observation results suggest that the superior electrical properties are the result of an improved crystallization, a larger grain size, and a smoother surface morphology. It is shown that the ion transport mechanism is dominated by an Ohmic behavior under low electric fields and the Poole-Frenkel emission effect under high electric fields.
Silica sol-gel encapsulation of cyanobacteria: lessons for academic and applied research.

PubMed

Dickson, David J; Ely, Roger L

2013-03-01

Cyanobacteria inhabit nearly every ecosystem on earth, play a vital role in nutrient cycling, and are useful as model organisms for fundamental research in photosynthesis and carbon and nitrogen fixation. In addition, they are important for several established biotechnologies for producing food additives, nutritional and pharmaceutical compounds, and pigments, as well as emerging biotechnologies for biofuels and other products. Encapsulation of living cyanobacteria into a porous silica gel matrix is a recent approach that may dramatically improve the efficiency of certain production processes by retaining the biomass within the reactor and modifying cellular metabolism in helpful ways. Although encapsulation has been explored empirically in the last two decades for a variety of cell types, many challenges remain to achieving optimal encapsulation of cyanobacteria in silica gel. Recent evidence with Synechocystis sp. PCC 6803, for example, suggests that several unknown or uncharacterized proteins are dramatically upregulated as a result of encapsulation. Also, additives commonly used to ease stresses of encapsulating living cells, such as glycerol, have detrimental impacts on photosynthesis in cyanobacteria. This mini-review is intended to address the current status of research on silica sol-gel encapsulation of cyanobacteria and research areas that may further the development of this approach for biotechnology applications.
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.
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.
Commercial and home-made nitrogen modified titanias. A short reflection about the advantageous/disadvantageous properties of nitrogen doping in the frame of their applicability

NASA Astrophysics Data System (ADS)

Pap, Zs.; Mogyorósi, K.; Veréb, G.; Dombi, A.; Hernádi, K.; Danciu, V.; Baia, L.

2014-09-01

As visible light driven photocatalysis became more and more intensively studied, the first commercial products showed up on the market. Simultaneously controversial results appeared in the literature generating an intensive debate regarding the advantages and draw-backs of nitrogen doping of titania. Hence, the present work focuses on two commercially available and four sol-gel made nitrogen modified titania powders regarding their structure and activity. It is demonstrated that the interstitial nitrogen entities “leak out” from the catalysts if the material is irradiated with UV light, while substitutional nitrogen remains stable. However, the latter one was proven to be less important in the photocatalytic point of view. These observations were also valid in the case of sol-gel made nitrogen modified titanias. Furthermore, the results obtained after applying different spectroscopic methods (IR, XPS and DRS) shown that the yellow color of the titanias, does not necessary mean that a successful doping is achieved.
Synthesis of a fluorine-free polymeric water-repellent agent for creation of superhydrophobic fabrics

NASA Astrophysics Data System (ADS)

Shen, Keke; Yu, Miao; Li, Qianqian; Sun, Wei; Zhang, Xiting; Quan, Miao; Liu, Zhengtang; Shi, Suqing; Gong, Yongkuan

2017-12-01

A non-fluorinated polymeric alkylsilane, poly(isobutyl methacrylate-co-3-methacryloxypropyltrimethoxysilane) (PIT), is designed and synthesized to replace the commercial long-chain perfluoroalkylsilane (FAS) water-repellent agent. The superhydrophobic polyester fabrics are prepared by anchoring sol-gel derived silica nanoparticles onto alkali-treated polyester fabric surfaces and subsequently hydrophobilizing with PIT, using FAS as control. The surface chemical composition, surface morphology, wetting behavior and durability of the modified polyester fabrics are characterized by scanning electron microscopy (SEM), X-ray photoelectron spectrophotometer (XPS) and video-based contact angle goniometer, respectively. The results show that a porous silica layer could be successfully fabricated onto the surface of polyester fabric through base-catalyzed sol-gel process with tetraethoxysilane (TEOS) as precursor, incorporating additional nanostructured roughness essential for superhydrophobicity. At the same time, such a silica primer layer could provide both secondary reactive moieties (-Si - OH) for the subsequent surface hydrophobization and acceptable adhesion at the silica-polyester fabric interface. When silica modified polyester fabric (SiO2@ fabric) is hydrophobized by PIT solution (10 mg/mL), excellent water-repellency could be obtained. The water contact angle is up to 154° and the sliding angle is about 5°. Compared with small molecule water-repellent agent FAS, PIT modified SiO2@ fabric exhibits greatly improved solvent resistance under ultra-sonication, abrasion and simulated laundering durability. The anti-stain property of PIT-modified SiO2@ fabric is also evaluated by using different aqueous colored solutions.
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.
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).
Sol-Gel Processing Science Using a Sol-Gel Optics Research Facility (SGORF)

DTIC Science & Technology

1989-09-10

Malaysia , Hong-Kong) where labor rates are perhaps one-tenth those of the U.S.. Figure 1 presents the trends of imports and exports of all optical... ACerS Annual Meeting, Washington, DC, May 1972. 2. W. A. Plummer, "Differential Dilatometry--A Powerful Tool," Corning Gla 33 Works, Corning, NY 14830
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.
Constructing a superhydrophobic surface on polydimethylsiloxane via spin coating and vapor-liquid sol-gel process.

PubMed

Peng, Yu-Ting; Lo, Kuo-Feng; Juang, Yi-Je

2010-04-06

In this study, a superhydrophobic surface on polydimethylsiloxane (PDMS) substrate was constructed via the proposed vapor-liquid sol-gel process in conjunction with spin coating of dodecyltrichlorosilane (DTS). Unlike the conventional sol-gel process where the reaction takes place in the liquid phase, layers of silica (SiO(2)) particles were formed through the reaction between the reactant spin-coated on the PDMS surface and vapor of the acid solution. This led to the SiO(2) particles inlaid on the PDMS surface. Followed by subsequent spin coating of DTS solution, the wrinkle-like structure was formed, and the static contact angle of the water droplet on the surface could reach 162 degrees with 2 degrees sliding angle and less than 5 degrees contact angle hysteresis. The effect of layers of SiO(2) particles, concentrations of DTS solution and surface topography on superhydrophobicity of the surface is discussed.
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.
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.
Preparation and Characterization of Polyurethanes with Cross-Linked Siloxane in the Side Chain by Sol-Gel Reactions

PubMed Central

Zhao, Hui; Hao, Tong-Hui; Hu, Guo-Hua; Shi, Dean; Huang, Da; Jiang, Tao; Zhang, Qun-Chao

2017-01-01

A series of novel polyurethanes containing cross-linked siloxane in the side chain (SPU) were successfully synthesized through a sol-gel process. The SPU was composed of 0%–20% N-(n-butyl)-3-aminopropyltriethoxysilane (HDI-T) modified hexamethylene diisocynate homopolymer. The effects of HDI-T content on both the structure and properties of SPU were investigated by Fourier transform infrared spectroscopy (FT-IR), X-ray photoelectron spectroscopy (XPS), X-ray diffraction (XRD), scanning electron microscopy (SEM), energy dispersive spectroscopy (EDS), differential scanning calorimetry (DSC), thermogravimetric analysis (TGA), mechanical properties tests, gel content test, water contact angle measurement and water absorption test. FT-IR, XPS and XRD results confirmed the successful incorporation of HDI-T onto polyurethanes and the formation of Si–O–Si. The surface roughness and the Si content of SPU enhanced with the increase of HDI-T content. Both crystallization and melting temperature shifted to a lower point after the incorporation of HDI-T. The hydrophobicity, tensile strength, Young’s modulus and pencil hardness overall increased with the increasing of HDI-T content, whereas the thermal stability and the elongation at break of SPU slightly decreased. PMID:28772607
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.
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 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.
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.

Effect of V-Nd co-doping on phase transformation and grain growth process of TiO2

NASA Astrophysics Data System (ADS)

Khatun, Nasima; Amin, Ruhul; Anita, Sen, Somaditya

2018-05-01

The pure and V-Nd co-doped TiO2 samples are prepared by the modified sol-gel process. The phase formation is confirmed by XRD spectrum. Phase transformation is delayed in V-Nd co-doped TiO2 (TVN) samples compared to pure TiO2. The particle size is comparatively small in TVN samples at both the temperature 450 °C and 900 °C. Hence the effect of Nd doping is dominated over V doping in both phase transformation and grain growth process of TiO2.
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
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.
Fabrication and Anti-Oxidation Ability of SiC-SiO₂ Coated Carbon Fibers Using Sol-Gel Method.

PubMed

Yang, Guangyuan; Huang, Zhixiong; Wang, Xu; Wang, Bo

2018-02-27

The paper proposed a method to improve the anti-oxidation performance of carbon fibers (CF) at high temperature environment by coating silicon dioxide (SiO₂) and silicon carbide (SiC). The modified sol-gel method had been used to ensure the proper interface between fibers and coating. We used polydimethylsiloxane and ethyl orthosilicate to make stable emulsion to uniformly disperse SiC nanoparticles. The modified SiO₂/SiC coating had been coated on CF successfully. Compared with the untreated CF, the coated fibers started to be oxidized around 900 °C and the residual weight was 57% at 1400 °C. The oxidation mechanism had been discussed. The structure of SiC/SiO₂ coated CF had been characterized by scanning electron microscope and X-ray diffraction analysis. Thermal gravimetric analysis was used to test the anti-oxidation ability of CF with different coatings.
Sol-gel Synthesis, Photo- and Electrocatalytic Properties of Mesoporous TiO2 Modified with Transition Metal Ions

NASA Astrophysics Data System (ADS)

Smirnova, N.; Petrik, I.; Vorobets, V.; Kolbasov, G.; Eremenko, A.

2017-03-01

Mesoporous nanosized titania films modified with Co2+, Ni2+, Mn3+, and Cu2+ ions have been produced by templated sol-gel method and characterized by optical spectroscopy, X-ray diffraction (XRD), and Brunauer, Emmett, and Teller (BET) surface area measurement. Band gap energy and the position of flat band potentials were estimated by photoelectrochemical measurements. The films doped with transition metals possessed higher photocurrent quantum yield, as well as photo- and electrochemical activity compared to undoped samples. Mn+/TiO2 (M-Co, Ni, Mn, Cu) electrodes with low dopant content demonstrate high efficiency in electrocatalytic reduction of dissolved oxygen. Polarization curves of TiO2, TiO2/Ni2+, TiO2/Co2+/3+, and TiO2/Mn3+ electrodes contain only one current wave (oxygen reduction current). It means that reaction proceeds without the formation of an intermediate product H2O2.
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.
Studies of (3-mercaptopropyl)trimethoxylsilane and bis(trimethoxysilyl)ethane sol-gel coating on copper and aluminum.

PubMed

Li, Ying-Sing; Lu, Weijie; Wang, Yu; Tran, Tuan

2009-09-01

Bis(trimethoxysilyl)ethane (BTMSE) and (3-mercaptopropyl)trimethoxysilane (MPTMS) have been used as precursors to prepare sol-gels and hybrid sol-gel under acidic condition. From the X-ray photoelectron spectroscopy data on MPTMS sol-gel coated aluminum and copper, it has been shown that the silane film is covalently bonded to Al surface through the interfacial condensation. There is no evidence of bonding interaction between the thiol group and the Cu. The recorded reflection adsorption IR (RAIR) spectrum has provided evidence that the coating BTMSE film covalently interacts with Al. Vibrational assignments have been suggested for pure BTMSE, BTMSE sol-gel, BTMSE xerogel, and BTMSE coated Al panel based on the group frequencies and the variation of frequencies with the sample treatment conditions. The progression of condensation reaction has been observed from the IR spectra of the BTMSE sol-gel and the sol-gel coated film after the treatments at different temperatures with different lengths of time. The corrosion protection of the sol-gel coated Al and Cu has been characterized in NaCl solutions by cyclic voltammetric, potentiodynamic polarization and impedance spectroscopy methods. All these electrochemical measurements indicate that the sol-gel coated metals have better corrosion protection than the corresponding uncoated metals.
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.
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.
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.
Chitosan-silane sol-gel hybrid thin films with controllable layer thickness and morphology.

PubMed

Spirk, Stefan; Findenig, Gerald; Doliska, Ales; Reichel, Victoria E; Swanson, Nicole L; Kargl, Rupert; Ribitsch, Volker; Stana-Kleinschek, Karin

2013-03-01

The preparation of thin films of chitosan-silane hybrid materials by combining sol-gel processing and spin coating is reported. A variety of silanes can be used as starting materials for the preparation of such thin films, namely tetraethoxysilane, tri-tert-butoxysilanol, trimethylethoxysilane, p-trifluoromethyltetra-fluorophenyltriethoxysilane, trivinylmethoxysilane, (methoxymethyl)trimethyl-silane, and hexamethoxydisilane. These silanes are subjected to a sol-gel process before they are added to acidic chitosan solutions. The chitosan:silane ratio is kept constant at 6:1 (w/w) and dilutions with ethanol are prepared and spin coated. Depending on the degree of dilution, film thickness can be controlled in a range between 5 and 70 nm. For the determination of additional surface properties, static water contact angle measurements and atomic force microscopy have been employed. Copyright © 2012 Elsevier Ltd. 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.
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.
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.
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.
Diamond nanoparticles as a way to improve electron transfer in sol-gel L-lactate biosensing platforms.

PubMed

Briones, M; Casero, E; Vázquez, L; Pariente, F; Lorenzo, E; Petit-Domínguez, M D

2016-02-18

In the present work, we have included for the first time diamond nanoparticles (DNPs) in a sol-gel matrix derived from (3-mercaptopropyl)-trimethoxysilane (MPTS) in order to improve electron transfer in a lactate oxidase (LOx) based electrochemical biosensing platform. Firstly, an exhaustive AFM study, including topographical, surface potential (KFM) and capacitance gradient (CG) measurements, of each step involved in the biosensing platform development was performed. The platform is based on gold electrodes (Au) modified with the sol-gel matrix (Au/MPTS) in which diamond nanoparticles (Au/MPTS/DNPs) and lactate oxidase (Au/MPTS/DNPs/LOx) have been included. For the sake of comparison, we have also characterized a gold electrode directly modified with DNPs (Au/DNPs). Secondly, the electrochemical behavior of a redox mediator (hydroxymethyl-ferrocene, HMF) was evaluated at the platforms mentioned above. The response of Au/MPTS/DNPs/LOx towards lactate was obtained. A linear concentration range from 0.053 mM to 1.6 mM, a sensitivity of 2.6 μA mM(-1) and a detection limit of 16 μM were obtained. These analytical properties are comparable to other biosensors, presenting also as advantages that DNPs are inexpensive, environment-friendly and easy-handled nanomaterials. Finally, the developed biosensor was applied for lactate determination in wine samples. Copyright © 2016 Elsevier B.V. All rights reserved.
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.
Synthesis and Properties of Carbon Nanotube-Grafted Silica Nanoarchitecture-Reinforced Poly(Lactic Acid)

PubMed Central

Hsu, Yao-Wen; Wu, Chia-Ching; Wu, Song-Mao

2017-01-01

A novel nanoarchitecture-reinforced poly(lactic acid) (PLA) nanocomposite was prepared using multi-walled carbon nanotube (MWCNT)-grafted silica nanohybrids as reinforcements. MWCNT-grafted silica nanohybrids were synthesized by the generation of silica nanoparticles on the MWCNT surface through the sol-gel technique. This synthetic method involves organo-modified MWCNTs that are dispersed in tetrahydrofuran, which incorporates tetraethoxysilane that undergoes an ultrasonic sol-gel process. Gelation yielded highly dispersed silica on the organo-modified MWCNTs. The structure and properties of the nanohybrids were established using 29Si nuclear magnetic resonance, Raman spectroscopy, wide-angle X-ray diffraction, thermogravimetric analysis, and transmission electron microscopy. The resulting MWCNT nanoarchitectures were covalently assembled into silica nanoparticles, which exhibited specific and controllable morphologies and were used to reinforce biodegradable PLA. The tensile strength and the heat deflection temperature (HDT) of the PLA/MWCNT-grafted silica nanocomposites increased when the MWCNT-grafted silica was applied to the PLA matrix; by contrast, the surface resistivity of the PLA/MWCNT-grafted silica nanocomposites appeared to decline as the amount of MWCNT-grafted silica in the PLA matrix increased. Overall, the reinforcement of PLA using MWCNT-grafted silica nanoarchitectures was efficient and improved its mechanical properties, heat resistance, and electrical resistivity. PMID:28773187
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...
Formation and prevention of fractures in sol-gel-derived thin films.

PubMed

Kappert, Emiel J; Pavlenko, Denys; Malzbender, Jürgen; Nijmeijer, Arian; Benes, Nieck E; Tsai, Peichun Amy

2015-02-07

Sol-gel-derived thin films play an important role as the functional coatings for various applications that require crack-free films to fully function. However, the fast drying process of a standard sol-gel coating often induces mechanical stresses, which may fracture the thin films. An experimental study on the crack formation in sol-gel-derived silica and organosilica ultrathin (submicron) films is presented. The relationships among the crack density, inter-crack spacing, and film thickness were investigated by combining direct micrograph analysis with spectroscopic ellipsometry. It is found that silica thin films are more prone to fracturing than organosilica films and have a critical film thickness of 300 nm, above which the film fractures. In contrast, the organosilica films can be formed without cracks in the experimentally explored regime of film thickness up to at least 1250 nm. These results confirm that ultrathin organosilica coatings are a robust silica substitute for a wide range of applications.

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.
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.
[Surface modification of dental alumina ceramic with silica coating].

PubMed

Xie, Hai-Feng; Zhang, Fei-Min; Wang, Xiao-Zu; Xia, Yang

2006-12-01

To make silica coating through sol-gel process, and to evaluate the wettability of dental alumina ceramic with or without coating. Silica coating was prepared with colloidal silica sol on In-Ceram alumina ceramic surface which had been treated with air particle abrasion. Coating gel after heat treatment was observed with atomic force microscope (AFM), and was analyzed by infrared spectrum (IR) with gel without sintered as control. Contact angles of oleic acid to be finished, sandblasted and coated ceramic surface of were measured. AFM pictures showed that some parts of nano-particles in coating gel conglomerated after heat treatment. It can be seen from the IR picture that bending vibration absorption kurtosis of Si-OH also vanished after heat treatment. Among contact angles of three treated surface, the ones on polished surface were the biggest (P = 0.000, P = 0.000), and sandblasting+silica coating surface the smallest (P = 0.000, P = 0.003). Silica coating can be made with sol-gel process successfully. Heat treatment may reinforce Si-O-Si net structure of coating gel. Wettability of dental alumina ceramic with silica coating is higher than with sandblasting and polishing.
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.
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.
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.
Glycol-modified silanes: novel possibilities for the synthesis of hierarchically organized (hybrid) porous materials.

PubMed

Hartmann, Sarah; Brandhuber, Doris; Hüsing, Nicola

2007-09-01

The preparation of porous hierarchical architectures that have structural features spanning from the nanometer to micrometer and even larger dimensions and that exhibit certain functionalities is one of the new challenging frontiers in materials chemistry. The sol-gel process is one of the most promising synthesis routes toward such materials because it not only offers the possibility to incorporate organic functions into the porous host but also offers the possibility to deliberately tailor the pore structure. In this Account, the opportunities given by the application of novel diol-modified silanes are discussed for the synthesis of hierarchically organized inorganic and also inorganic-organic porous monoliths.
The characteristic of carbon-coated LiFePO{sub 4} as cathode material for lithium ion battery synthesized by sol-gel process in one step heating and varied pH

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

Triwibowo, J., E-mail: joko.triwibowo@lipi.go.id; Yuniarti, E.; Suharyadi, E.

2014-09-25

This research has been done on the synthesis of carbon coated LiFePO{sub 4} through sol-gel process. Carbon layer serves for improving electronic conductivity, while the variation of pH in the sol-gel process is intended to obtain the morphology of the material that may improve battery performance. LiFePO{sub 4}/C precursors are Li{sub 2}CO{sub 3}, NH{sub 4}H{sub 2}PO{sub 4} and FeC{sub 2}O{sub 4}.H{sub 2}O and citric acid. In the synthesis process, consisting of a colloidal suspension FeC{sub 2}O{sub 4}.H{sub 2}O and distilled water mixed with a colloidal suspension consisting of NH{sub 4}H{sub 2}PO{sub 4}, Li{sub 2}CO{sub 3}, and distilled water. Variations additionmore » of citric acid is used to control the pH of the gel formed by mixing two colloidal suspensions. Sol in this study had a pH of 5, 5.4 and 5.8. The obtained wet gel is further dried in the oven and then sintered at a temperature 700°C for 10 hours. The resulting material is further characterized by XRD to determine the phases formed. The resulting powder morphology is observed through SEM. Specific surface area of the powder was tested by BET, while the electronic conductivity characterized with EIS.« less
Synthesis and thermochromic property studies on W doped VO2 films fabricated by sol-gel method.

PubMed

Pan, Guoping; Yin, Jinhua; Ji, Keli; Li, Xiang; Cheng, Xingwang; Jin, Haibo; Liu, Jiping

2017-07-21

Tungsten-doped VO 2 thin films have been synthesized by a modified sol-gel process and followed by a post annealing. Vanadium pentoxide and tungstic acid as raw materials with the addition of hydrogen peroxide, concentrated hydrochloric acid (catalyst) and oxalic acid used as reducing agent were reacted in isobutanol. Finally, the uniform sol of vanadyl oxalate in isobutanol solvent was obtained as precursor. Detailed study suggested that W doped in VO 2 introduces additional electron carriers and induces the formation of V 3+ . Post annealing under vacuum promotes the releasing of chemical stress and generates oxygen vacancies in the samples. Temperature dependent transmittance study revealed that the releasing of chemical stress and deliberately introducing oxygen vacancies in W-doped VO 2 films have positive effects on enhancing its switching ability in the infrared transmittance as the metal-insulator transition (MIT) occurs. The largest switching of transmittance was obtained about 48% in the infrared range at 43 °C in 1.5%W doped VO 2 films, which is significantly larger than the reported ones. The findings in this work open a new way to synthesize the novel and thermochromic W doped VO 2 films with facility and low cost. Therefore, it has extensive application to construct smart windows and electronic devices.
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...
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
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.
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.
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.
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
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.
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.
Novel carboxy functionalized sol-gel precursors

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

Wolter, H.; Storch, W.; Gellermann, C.

1996-12-31

A novel family of inorganic-organic copolymers (ORMOCER`s) derived from urethane- and thioether(meth)acrylate alkoxysilanes has been successfully exploited for a variety of diverse applications. In order to widen the range of applications an additional functionality (carboxy group) has been incorporated int his silane type. Conventional sol-gel processing facilitates the formation of an inorganic Si-O-Si-network via hydrolysis and polycondensation reactions of alkoxysilyl moieties and in addition, the (meth)acrylate groups are available for radically induced polymerization to obtain a complementary organic polymer structure. The presence of a carboxy group would appear to have great potential for a range of diverse areas of application,more » such as an internal catalyst for the sol-gel process, complexation of elements such as Zr and Ti, increasing the adhesion to various substrates and modification of solubility. A number of novel silanes and their syntheses will be described in this paper.« less
Low birefringent magneto-optical waveguides fabricated via organic-inorganic sol-gel process

NASA Astrophysics Data System (ADS)

Choueikani, F.; Royer, F.; Douadi, S.; Skora, A.; Jamon, D.; Blanc, D.; Siblini, A.

2009-09-01

This paper is devoted to the study and the characterization of novel magneto-optical waveguides prepared via organic-inorganic sol-gel process. Thin silica/zirconia films doped with magnetic nanoparticles were coated on glass substrate using dip-coating technique. After annealing, samples were UV-treated. Two different techniques were used to measure their properties: m-lines spectroscopy and free space ellipsometry. Results evidence low refractive index waveguides that combine a low modal birefringence (2×10-4) with a Faraday rotation around 15 °/cm (φ = 0.1%). The low birefringence is obtained with a soft UV treatment and a graded intrinsic anisotropy is evidenced for films thicker than 5 μm. Therefore, we prove that the organic-inorganic sol-gel approach is very promising to realize magneto-optical waveguides with a non-reciprocal functionality such as TE-TM mode conversion.
Reactive Molecular Dynamics Investigations of Alkoxysilane Sol-Gel and Surface Coating Processes

NASA Astrophysics Data System (ADS)

Deetz, Joshua David

The ability to generate nanostructured materials with tailored morphology or chemistry is of great technological interest. One proven method of generating metal-oxide materials, and chemically modifying metal-oxide surfaces is through the reactions of molecular building blocks known as alkoxysilanes. Alkoxysilanes are a class of chemicals which contain one or more organic alkoxy groups bonded to silicon atoms. Alkoxysilane (Si-O-R) chemical groups can undergo reactions to form bridges (Si-O-M) with metal oxides. Due to their ability to "attach" to metal-oxides through condensation reactions, alkoxysilanes have a number of interesting applications, such as: the generation of synthetic siloxane materials through the sol-gel process, and the formation of functionalized surface coatings on metal-oxide surfaces. Despite widespread study of sol-gel and surface coatings processes, it is difficult to predict the morphology of the final products due to the large number of process variables involved, such as precursor molecule structure, solvent effects, solution composition, temperature, and pH. To determine the influence of these variables on the products of sol-gel and coatings processes reactive molecular dynamics simulations are used. A reactive force field was used (ReaxFF) to allow the chemical bonds in simulation to dynamically form and break. The force field parameters were optimized using a parallel optimization scheme with a combination of experimental information, and density functional theory calculations. Polycondensation of alkoxysilanes in mixtures of alcohol and water were studied. Steric effects were observed to influence the rates of hydrolysis and condensation in solutions containing different precursor monomers. By restricting the access of nucleophiles to the central silicon atom, the nucleation rate of siloxanes can be controlled. The influence of solution precursor, water, and methanol composition on reaction rates was explored. It was determined that the rate of alkoxysilane hydrolysis is strongly dependent on the concentration of water. The dynamics of siloxane cluster formation are revealed, which provides insight for experimentalists. The silanization of hydroxylated silica surfaces by alkoxysilanes was modeled in pseudo-infinite liquid solution. Butyl-, octyl-, or dodecylsilanes were exposed to hydroxylated silica surfaces in order to observe the influence of silyl headgroup size on the morphology and formation kinetics of silane films on silica substrates. The radius of gyration and order parameter of the hydrocarbon silyl groups were found to increase with grafting density. This was the first simulation study of the dynamic grafting of alkoxysilanes to a substrate.

Preparation of MTMS based transparent superhydrophobic silica films by sol-gel method.

PubMed

Venkateswara Rao, A; Latthe, Sanjay S; Nadargi, Digambar Y; Hirashima, H; Ganesan, V

2009-04-15

Superhydrophobic surfaces with water contact angle higher than 150 degrees generated a lot of interest both in academia and in industry because of the self-cleaning properties. Optically transparent superhydrophobic silica films were synthesized at room temperature (27 degrees C) using sol-gel process by a simple dip coating technique. The molar ratio of MTMS:MeOH:H(2)O (5 M NH(4)OH) was kept constant at 1:10.56:4.16, respectively. Emphasis is given to the effect of the surface modifying agents on the hydrophobic behavior of the films. Methyl groups were introduced in the silica film by post-synthesis grafting from two solutions using trimethylchlorosilane (TMCS) and hexamethyldisilazane (HMDZ) silylating agents in hexane solvent, individually. The percentage of silylating agents and silylation period was varied from 2.5 to 7.5% and 1 to 3 h, respectively. The TMCS modified films exhibited a very high water contact angle (166+/-2 degrees) in comparison to the HMDZ (138+/-2 degrees) modified films, indicating the water repellent behavior of the surface. When the TMCS and HMDZ modified films were heated at temperatures higher than 350 degrees C and 335 degrees C, respectively, the films became superhydrophilic; the contact angle for water on the films was smaller than 5 degrees. Further, the humidity study was carried out at a relative humidity of 85% at 30 degrees C temperature over 30 days. The films have been characterized by scanning electron microscopy (SEM), atomic force microscopy (AFM), Fourier transform infrared spectroscopy (FT-IR), % optical transmission, humidity tests and contact angle (CA) measurements.
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.
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.
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 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.
Development of Highly Durable and Reactive Regenerable Magnesium-Based Sorbents for CO2 Separation in Coal Gasification Process

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

Javad Abbasian; Armin Hassanzadeh Khayyat; Rachid B. Slimane

The specific objective of this project was to develop physically durable and chemically regenerable MgO-based sorbents that can remove carbon dioxide from raw coal gas at operating condition prevailing in IGCC processes. A total of sixty two (62) different sorbents were prepared in this project. The sorbents were prepared either by various sol-gel techniques (22 formulations) or modification of dolomite (40 formulations). The sorbents were prepared in the form of pellets and in granular forms. The solgel based sorbents had very high physical strength, relatively high surface area, and very low average pore diameter. The magnesium content of the sorbentsmore » was estimated to be 4-6 % w/w. To improve the reactivity of the sorbents toward CO{sub 2}, The sorbents were impregnated with potassium salts. The potassium content of the sorbents was about 5%. The dolomite-based sorbents were prepared by calcination of dolomite at various temperature and calcination environment (CO{sub 2} partial pressure and moisture). Potassium carbonate was added to the half-calcined dolomite through wet impregnation method. The estimated potassium content of the impregnated sorbents was in the range of 1-6% w/w. In general, the modified dolomite sorbents have significantly higher magnesium content, larger pore diameter and lower surface area, resulting in significantly higher reactivity compared to the sol-gel sorbents. The reactivities of a number of sorbents toward CO{sub 2} were determined in a Thermogravimetric Analyzer (TGA) unit. The results indicated that at the low CO{sub 2} partial pressures (i.e., 1 atm), the reactivities of the sorbents toward CO{sub 2} are very low. At elevated pressures (i.e., CO{sub 2} partial pressure of 10 bar) the maximum conversion of MgO obtained with the sol-gel based sorbents was about 5%, which corresponds to a maximum CO{sub 2} absorption capacity of less than 1%. The overall capacity of modified dolomite sorbents were at least one order of magnitude higher than those of the sol-gel based sorbents. The results of the tests conducted with various dolomite-based sorbent indicate that the reactivity of the modified dolomite sorbent increases with increasing potassium concentration, while higher calcination temperature adversely affects the sorbent reactivity. Furthermore, the results indicate that as long as the absorption temperature is well below the equilibrium temperature, the reactivity of the sorbent improves with increasing temperature (350-425 C). As the temperature approaches the equilibrium temperature, because of the significant increase in the rate of reverse (i.e., regeneration) reaction, the rate of CO{sub 2} absorption decreases. The results of cyclic tests show that the reactivity of the sorbent gradually decreases in the cyclic process. To improve long-term durability (i.e., reactivity and capacity) of the sorbent, the sorbent was periodically re-impregnated with potassium additive and calcined. The results indicate that, in general, re-treatment improves the performance of the sorbent, and that, the extent of improvement gradually decreases in the cyclic process. The presence of steam significantly enhances the sorbent reactivity and significantly decreases the rate of decline in sorbent deactivation in the cyclic process.« less
Correlation of structural properties with energy transfer of Eu-doped ZnO thin films prepared by sol-gel process and magnetron reactive sputtering

PubMed Central

Petersen, Julien; Brimont, Christelle; Gallart, Mathieu; Schmerber, Guy; Gilliot, Pierre; Ulhaq-Bouillet, Corinne; Rehspringer, Jean-Luc; Colis, Silviu; Becker, Claude; Slaoui, Abdelillah; Dinia, Aziz

2010-01-01

We investigated the structural and optical properties of Eu-doped ZnO thin films made by sol-gel technique and magnetron reactive sputtering on Si (100) substrate. The films elaborated by sol-gel process are polycrystalline while the films made by sputtering show a strongly textured growth along the c-axis. X-ray diffraction patterns and transmission electron microscopy analysis show that all samples are free of spurious phases. The presence of Eu2+ and Eu3+ into the ZnO matrix has been confirmed by x-ray photoemission spectroscopy. This means that a small fraction of Europium substitutes Zn2+ as Eu2+ into the ZnO matrix; the rest of Eu being in the trivalent state. This is probably due to the formation of Eu2O3 oxide at the surface of ZnO particles. This is at the origin of the strong photoluminescence band observed at 2 eV, which is characteristic of the 5D0→7F2 Eu3+ transition. In addition the photoluminescence excitonic spectra showed efficient energy transfer from the ZnO matrix to the Eu3+ ion, which is qualitatively similar for both films although the sputtered films have a better structural quality compared to the sol-gel process grown films. PMID:20644657
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.
Highly Luminescent Hybrid SiO2-Coated CdTe Quantum Dots Retained Initial Photoluminescence Efficiency in Sol-Gel SiO2 Film.

PubMed

Sun, Hongsheng; Xing, Yugui; Wu, Qinan; Yang, Ping

2015-02-01

A highly luminescent silica film was fabricated using tetraethyl orthosilicate (TEOS) and 3-aminopropyltrimethoxysilane (APS) through a controlled sol-gel reaction. The pre-hydrolysis of TEOS and APS which resulted in the mixture of TEOS and APS in a molecular level is a key for the formation of homogenous films. The aminopropyl groups in APS play an important role for obtaining homogeneous film with high photoluminescence (PL). Red-emitting hybrid SiO2-coated CdTe nano-crystals (NCs) were fabricated by a two-step synthesis including a thin SiO2 coating via a sol-gel process and a subsequent refluxing using green-emitting CdTe NCs. The hybrid SiO2-coated CdTe NCs were embedded in a functional SiO2 film via a two-step process including adding the NCs in SiO2 sol with a high viscosity and almost without ethanol and a subsequent spinning coating. The hybrid SiO2-coated CdTe NCs retained their initial PL efficiency (54%) in the film. Being encapsulated with the hybrid NCs in the film, no change on the absorption and PL spectra of red-emitting CdTe NCs (632 nm) was observed. This indicates the hybrid NCs is stable enough during preparation. This phenomenon is ascribed to the controlled sol-gel process and a hybrid SiO2 shell on CdTe NCs. Because these films exhibited high PL efficiency and stability, they will be utilizable for potential applications in many fields.
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.
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
Dielectric relaxation and electrical conductivity in Bi 5NbO 10 oxygen ion conductors prepared by a modified sol-gel process

NASA Astrophysics Data System (ADS)

Hou, Jungang; Vaish, Rahul; Qu, Yuanfang; Krsmanovic, Dalibor; Varma, K. B. R.; Kumar, R. V.

Crystalline Bi 5NbO 10 nanoparticles have been achieved through a modified sol-gel process using a mixture of ethylenediamine and ethanolamine as a solvent. The Bi 5NbO 10 nanoparticles were characterized by X-ray diffraction (XRD), differential scanning calorimetry/thermogravimetry (DSC/TG), Fourier transform infrared spectroscopy (FT-IR), transmission electron microscopy (TEM) and Raman spectroscopy. The results showed that well-dispersed 5-60 nm Bi 5NbO 10 nanoparticles were prepared through heat-treating the precursor at 650 °C and the high density pellets were obtained at temperatures lower than those commonly employed. The frequency and temperature dependence of the dielectric constant and the electrical conductivity of the Bi 5NbO 10 solid solutions were investigated in the 0.1 Hz to 1 MHz frequency range. Two distinct relaxation mechanisms were observed in the plots of dielectric loss and the imaginary part of impedance (Z″) versus frequency in the temperature range of 200-350 °C. The dielectric constant and the loss in the low frequency regime were electrode dependent. The ionic conductivity of Bi 5NbO 10 solid solutions at 700 °C is 2.86 Ω -1 m -1 which is in same order of magnitude for Y 2O 3-stabilized ZrO 2 ceramics at same temperature. These results suggest that Bi 5NbO 10 is a promising material for an oxygen ion conductor.
Integrating nanohybrid membranes of reduced graphene oxide: chitosan: silica sol gel with fiber optic SPR for caffeine detection

NASA Astrophysics Data System (ADS)

Kant, Ravi; Tabassum, Rana; Gupta, Banshi D.

2017-05-01

Caffeine is the most popular psychoactive drug consumed in the world for improving alertness and enhancing wakefulness. However, caffeine consumption beyond limits can result in lot of physiological complications in human beings. In this work, we report a novel detection scheme for caffeine integrating nanohybrid membranes of reduced graphene oxide (rGO) in chitosan modified silica sol gel (rGO: chitosan: silica sol gel) with fiber optic surface plasmon resonance. The chemically synthesized nanohybrid membrane forming the sensing route has been dip coated over silver coated unclad central portion of an optical fiber. The sensor works on the mechanism of modification of dielectric function of sensing layer on exposure to analyte solution which is manifested in terms of red shift in resonance wavelength. The concentration of rGO in polymer network of chitosan and silica sol gel and dipping time of the silver coated probe in the solution of nanohybrid membrane have been optimized to extricate the supreme performance of the sensor. The optimized sensing probe possesses a reasonably good sensitivity and follows an exponentially declining trend within the entire investigating range of caffeine concentration. The sensor boasts of an unparalleled limit of detection value of 1.994 nM and works well in concentration range of 0-500 nM with a response time of 16 s. The impeccable sensor methodology adopted in this work combining fiber optic SPR with nanotechnology furnishes a novel perspective for caffeine determination in commercial foodstuffs and biological fluids.
Evaluation of tetraethoxysilane (TEOS) sol-gel coatings, modified with green synthesized zinc oxide nanoparticles for combating microfouling.

PubMed

Krupa, A Nithya Deva; Vimala, R

2016-04-01

Green synthesis of zinc oxide nanoparticles (ZnO-NPs) is gaining importance as an eco-friendly alternative to conventional methods due to its enormous applications. The present work reports the synthesis of ZnO-NPs using the endosperm of Cocos nucifera (coconut water) and the bio-molecules responsible for nanoparticle formation have been identified. The synthesized nanoparticles were characterized using UV-Visible spectroscopy (UV-Vis), X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), Transmission Electron Microscopy (TEM) and Zeta potential measurement. The results obtained reveal that the synthesized nanoparticles are moderately stable with the size ranging from 20 to 80 nm. The bactericidal effect of the nanoparticles was proved by well diffusion assay and determination of minimum inhibitory concentration (MIC) against marine biofilm forming bacteria. Further the green synthesized ZnO-NPs were doped with TEOS sol-gels (TESGs) in order to assess their antimicrofouling capability. Different volumes of liquid sol-gels were coated on to 96-well microtitre plate and cured under various conditions. The optimum curing conditions were found to be temperature 60 °C, time 72 h and volume 200 μl. Antiadhesion test of the undoped (SG) and ZnO-NP doped TEOS sol-gel (ZNSG) coatings were evaluated using marine biofilm forming bacteria. ZNSG coatings exhibited highest biofilm inhibition (89.2%) represented by lowest OD value against Pseudomonasotitidis strain NV1. Copyright © 2016 Elsevier B.V. All rights reserved.
Preparation and luminescent properties of lanthanide (Eu3+ and Tb3+) complexes grafted to 3-aminopropyltriethoxysilane by covalent bonds

NASA Astrophysics Data System (ADS)

Zhang, Wenjun; Wang, Haiyan

2015-12-01

A novel precursor PMA-Si was synthesized by modifying 1,2,4,5-benzene-tetracarboxylic acid (PMA) with 3-aminopropyltriethoxysilane (APTES). Then the hybrids were prepared by PMA-Si coordinating to lanthanide ions (Eu3+ and Tb3+) in sol-gel process. In order to improve luminescent efficiency, 1,10-Phenanthroline (Phen) was introduced to the system as the second ligand. As-prepared compounds in sol condition were coated on quartz plates to form a layer of thin film, which was different from other similar hybrids. The properties of the hybrids were characterized by FT-IR, fluorescence spectra, TG and SEM. The results showed that the obtained materials enhanced thermal stability, mechanical resistances, waterproofness as well as machining properties.
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.
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.

Could titanium oxide coating from a sol-gel process make stone baskets more resistant to laser radiation at 2.1 μm?

PubMed

Cordes, Jens; Nguyen, Felix; Heidenau, Frank; Jocham, Dieter

2012-10-19

Stone baskets could be easily destroyed by Holmium:YAG-laser at an endourologic treatment, with respect to this, we try to improve the resistance by coating them with a titanium oxide layer. The layer was established by a sol-gel-process. Six new baskets (Equadus, Opi Med, Ettlingen, Germany) were used: 1.8 Ch. with 4 wires (diameter 0.127 mm). Three baskets were coated with a layer of titanium oxide established by a sol-gel process at the BioCerEntwicklungs GmbH in Bayreuth (~100 nanometres thickness). The lithotripter was a Holmium:YAG laser (Auriga XL, Starmedtec, Starnberg, Germany). 10 uncoated and 10 coated wires were tested with 610 mJ (the minimal clinical setting) and 2 uncoated and 2 coated wires were tested with 110 mJ. The wires were locked in a special holding instrument under water and the laser incident angle was 90°. The endpoint was gross visible damage to the wire and loss of electric conduction. Only two coated wires resisted two pulses (one in the 610 mJ and one in the 110 mJ setting). All other wires were destroyed after one pulse. This was the first attempt at making stone baskets more resistant to a Holmium:YAG laser beam. Titanium oxide deposited by a sol-gel-process on a titanium-nickel alloy did not result in better resistance to laser injuries.
Silica coatings formed on noble dental casting alloy by the sol-gel dipping process.

PubMed

Yoshida, K; Tanagawa, M; Kamada, K; Hatada, R; Baba, K; Inoi, T; Atsuta, M

1999-08-01

The sol-gel dipping process, in which liquid silicon alkoxide is transformed into the solid silicon-oxygen network, can produce a thin film coating of silica (SiO2). The features of this method are high homogeneity and purity of the thin SiO2 film and a low sinter temperature, which are important in preparation of coating films that can protect from metallic ion release from the metal substrate and prevent attachment of dental plaque. We evaluated the surface characteristics of the dental casting silver-palladium-copper-gold (Ag-Pd-Cu-Au) alloy coated with a thin SiO2 film by the sol-gel dipping process. The SiO2 film bonded strongly (over 40 MPa) to Ti-implanted Ag-Pd-Cu-Au alloy substrate as demonstrated by a pull test. Hydrophobilization of Ti-implanted/SiO2-coated surfaces resulted in a significant increase of the contact angle of water (80.5 degrees) compared with that of the noncoated alloy specimens (59.3 degrees). Ti-implanted/SiO2-coated specimens showed the release of many fewer metallic ions (192 ppb/cm2) from the substrate than did noncoated specimens (2,089 ppb/cm2). The formation of a thin SiO2 film by the sol-gel dipping process on the surface of Ti-implanted Ag-Pd-Cu-Au alloy after casting clinically may be useful for minimizing the possibilities of the accumulation of dental plaque and metal allergies caused by intraoral metal restorations.
The development and characterization of sol-gel substrates for chemical and optical applications

NASA Astrophysics Data System (ADS)

Powers, Kevin William

1998-12-01

The sol gel process can be used to make monolithic porous glass for various scientific and engineering uses. The porosity of the material imparts a large surface area which is advantageous in applications such as catalyst supports or in the study of surface mediated chemical reactions. The chemical stability and transparency of the porous glass also make it suitable for use in the emerging field of optical sensors. In this study fluoride catalysis is used to produce sol gel monoliths with pore radii of up to 400 Angstroms, four times larger than any previously reported using conventional drying techniques. Gel monoliths with pore radii of 200 Angstroms were found to have the best combination of surface area, pore volume and optical transparency. Typical monoliths have surface areas of 150 m2/g and pore volumes of 1.60 cm3/g with good transparency. The monoliths are chemically stable, have good mechanical strength and can be easily rehydrated without cracking. The substrates are also suitable for sintering into dense high purity silica glass with little tendency towards foaming. An in-depth study of the catalytic effect of fluoride on the sol gel process is also included. It has been theorized that fluoride serves to expand the coordination sphere of the silicon center making it more subject to nucleophilic attack. In this work an ion-specific fluoride electrode is used to monitor free fluoride concentrations in HF catalyzed sols while silicic acid is added in the form of tetramethoxysilane (TMOS). It is found that fluoride is rapidly bound by the silicic acid in a ratio of four to one, indicating the formation of silicon tetrafluoride. A concurrent decrease in pH suggests that a pentacoordinate species is formed that is more stable than previously thought. A polymerization mechanism is proposed that explains the hydrophobicity of fluoride catalyzed gels and the difficulty in retaining structural fluoride in fluoride catalyzed sol gel glasses. Finally, several porous monoliths are doped with colloidal gold and the optical properties evaluated as a function of heat treatment. This demonstrates the feasibility of using porous glass nanocomposites in sensors and other optical components.
Stability Improvements of DNA Photonic Devices

DTIC Science & Technology

2008-12-20

possible in such areas as photonics, separation process or biomedical materials . Recent research results on DNA-lipid complexes have shown various...onto Teflon- coated glass plate to obtain films by irradiating UV light to cause crosslinking reactions of the Adeka sol-gel materials Clear and...into sol-gel materials or synthetic polymers so that water permeation is prevented by glass or synthetic polymers to stabilize and to keep the optical
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.
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.
Effects of sol aging on resistive switching behaviors of HfOx resistive memories

NASA Astrophysics Data System (ADS)

Hsu, Chih-Chieh; Sun, Jhen-Kai; Tsao, Che-Chang; Chen, Yu-Ting

2017-03-01

This work investigates effects of long-term sol-aging time on sol-gel HfOx resistive random access memories (RRAMs). A nontoxic solvent of ethanol is used to replace toxic 2-methoxyethanol, which is usually used in sol-gel processes. The top electrodes are fabricated by pressing indium balls onto the HfOx surface rather than by using conventional sputtering or evaporation processes. The maximum process temperature is limited to be 100 ℃. Therefore, influences of plasma and high temperature on HfOx film can be avoided. Under this circumstance, effects of sol aging time on the HfOx films can be more clearly studied. The current conduction mechanisms in low and high electric regions of the HfOx RRAM are found to be dominated by Ohmic conduction and trap-filled space charge limited conduction (TF-SCLC), respectively. When the sol aging time increases, the resistive switching characteristic of the HfOx layer becomes unstable and the transition voltage from Ohmic conduction to TF-SCLC is also increased. This suggests that an exceedingly long aging time will give a HfOx film with more defect states. The XPS results are consistent with FTIR analysis and they can further explain the unstable HfOx resistive switching characteristic induced by sol aging.
[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.
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)
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.
Sensing response of copper phthalocyanine salt dispersed glass with organic vapours

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

Ridhi, R.; Sachdeva, Sheenam; Saini, G. S. S.

2016-05-06

Copper Phthalocyanine and other Metal Phthalocyanines are very flexible and tuned easily to modify their structural, spectroscopic, optical and electrical properties by either functionalizing them with various substituent groups or by replacing or adding a ligand to the central metal atom in the phthalocyanine ring and accordingly can be made sensitive and selective to various organic species or gaseous vapours. In the present work, we have dispersed Copper Phthalocyanine Salt (CuPcS) in sol-gel glass form using chemical route sol-gel method and studied its sensing mechanism with organic vapours like methanol and benzene and found that current increases onto their exposuremore » with vapours. A variation in the activation energies was also observed with exposure of vapours.« less
Sensing response of copper phthalocyanine salt dispersed glass with organic vapours

NASA Astrophysics Data System (ADS)

Ridhi, R.; Sachdeva, Sheenam; Saini, G. S. S.; Tripathi, S. K.

2016-05-01

Copper Phthalocyanine and other Metal Phthalocyanines are very flexible and tuned easily to modify their structural, spectroscopic, optical and electrical properties by either functionalizing them with various substituent groups or by replacing or adding a ligand to the central metal atom in the phthalocyanine ring and accordingly can be made sensitive and selective to various organic species or gaseous vapours. In the present work, we have dispersed Copper Phthalocyanine Salt (CuPcS) in sol-gel glass form using chemical route sol-gel method and studied its sensing mechanism with organic vapours like methanol and benzene and found that current increases onto their exposure with vapours. A variation in the activation energies was also observed with exposure of vapours.
Growth and properties of gradient free sol-gel lead zirconate titanate thin films

NASA Astrophysics Data System (ADS)

Calame, F.; Muralt, P.

2007-02-01

Pb(Zrx,Ti1-x)O3 thin films of homogeneous composition were synthesized by means of a modified sol-gel route on Pt(111)/TiOx/SiO2/Si substrates. The gradient in B-site composition as obtained by standard routes could be lowered, reducing Zr concentration fluctuations form ±12to±2.5at.%. The 2μm thick, dense and crack-free films exhibited a {100}-texture index of 98.4%. Grain diameters increased by 50%. Dielectric and piezoelectric properties were remarkably improved. The relative dielectric constant ɛ33,f was obtained as 1620, and the remanent transverse piezoelectric coefficient e31,f was measured as -17.7Cm2.
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.
Effectiveness of silica based sol-gel microencapsulation method for odorants and flavors leading to sustainable environment

PubMed Central

Ashraf, Muhammad Aqeel; Khan, Aysha Masood; Ahmad, Mushtaq; Sarfraz, Maliha

2015-01-01

Microencapsulation has become a hot topic in chemical research. Technology mainly used for control release and protection purposes. The sol-gel micro encapsulation approach for fragrance and aroma in porous silica-based materials leads to sustainable odorant and flavored materials with novel and unique beneficial properties. Sol-gel encapsulation of silica based micro particles considered economically cheap as capital investment in manufacturing is very low and environmentally friendly. Amorphous sol-gel SiO2 is non-toxic and safe, whereas the sol-gel entrapment of delicate chemicals in its inner pores results in pronounced chemical and physical stabilization of the entrapped active agents, thereby broadening the practical utilization of chemically unstable essential oils (EOs). Reviewing progress in the fabrication of diverse odorant and flavored sol-gels, shows us how different synthetic strategies are appropriate for practical application with important health and environmental benefits. PMID:26322304
Effectiveness of silica based sol-gel microencapsulation method for odorants and flavors leading to sustainable environment.

PubMed

Ashraf, Muhammad Aqeel; Khan, Aysha Masood; Ahmad, Mushtaq; Sarfraz, Maliha

2015-01-01

Microencapsulation has become a hot topic in chemical research. Technology mainly used for control release and protection purposes. The sol-gel micro encapsulation approach for fragrance and aroma in porous silica-based materials leads to sustainable odorant and flavored materials with novel and unique beneficial properties. Sol-gel encapsulation of silica based micro particles considered economically cheap as capital investment in manufacturing is very low and environmentally friendly. Amorphous sol-gel SiO2 is non-toxic and safe, whereas the sol-gel entrapment of delicate chemicals in its inner pores results in pronounced chemical and physical stabilization of the entrapped active agents, thereby broadening the practical utilization of chemically unstable essential oils (EOs). Reviewing progress in the fabrication of diverse odorant and flavored sol-gels, shows us how different synthetic strategies are appropriate for practical application with important health and environmental benefits.
Nanostructured Silica/Gold-Cellulose-Bonded Amino-POSS Hybrid Composite via Sol-Gel Process and Its Properties.

PubMed

Ramesh, Sivalingam; Kim, Heung Soo; Lee, Young-Jun; Hong, Gwang-Wook; Kim, Joo-Hyung

2017-12-01

It is demonstrated in this paper that silica nanoparticles coated with core/shell gold provide efficient thermal, optical, and morphological properties with respect to the cellulose-polyhedral oligomeric silsesquioxanes (POSS) hybrid system. The one-step synthesis of a silica/gold nanocomposite is achieved with a simultaneous hydrolysis and reduction of gold chloride in the presence of formic acid, and the trimethoxysilane group acts as a silica precursor. The focus here comprises the synthesis of cellulose-POSS and silica/gold hybrid nanocomposites using the following two methods: (1) an in situ sol-gel process and (2) a polyvinyl alcohol/tetrakis (hydroxymethyl)phosphonium chloride process. Accordingly, the silica/gold core/shell nanoparticles are synthesized. The growth and attachment of the gold nanoparticles onto the functionalized surface of the silica at the nanometer scale is achieved via both the sol-gel and the tetrakis (hydroxymethyl) phosphonium chloride processes. The cellulose-POSS-silica/gold nanocomposites are characterized according to Fourier transformed infrared spectroscopy, Raman, X-ray diffraction, UV, photoluminescence, SEM, energy-dispersive X-ray spectroscopy, TEM, thermogravimetric, and Brunauer-Emmett-Teller analyses.
Nanostructured Silica/Gold-Cellulose-Bonded Amino-POSS Hybrid Composite via Sol-Gel Process and Its Properties

NASA Astrophysics Data System (ADS)

Ramesh, Sivalingam; Kim, Heung Soo; Lee, Young-June; Hong, Gwang-Wook; Kim, Joo-Hyung

2017-06-01

It is demonstrated in this paper that silica nanoparticles coated with core/shell gold provide efficient thermal, optical, and morphological properties with respect to the cellulose-polyhedral oligomeric silsesquioxanes (POSS) hybrid system. The one-step synthesis of a silica/gold nanocomposite is achieved with a simultaneous hydrolysis and reduction of gold chloride in the presence of formic acid, and the trimethoxysilane group acts as a silica precursor. The focus here comprises the synthesis of cellulose-POSS and silica/gold hybrid nanocomposites using the following two methods: (1) an in situ sol-gel process and (2) a polyvinyl alcohol/tetrakis (hydroxymethyl)phosphonium chloride process. Accordingly, the silica/gold core/shell nanoparticles are synthesized. The growth and attachment of the gold nanoparticles onto the functionalized surface of the silica at the nanometer scale is achieved via both the sol-gel and the tetrakis (hydroxymethyl) phosphonium chloride processes. The cellulose-POSS-silica/gold nanocomposites are characterized according to Fourier transformed infrared spectroscopy, Raman, X-ray diffraction, UV, photoluminescence, SEM, energy-dispersive X-ray spectroscopy, TEM, thermogravimetric, and Brunauer-Emmett-Teller analyses.

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.
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.
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.
Modification of Different Zirconium Propoxide Precursors by Diethanolamine. Is There a Shelf Stability Issue for Sol-Gel Applications?

PubMed Central

Spijksma, Gerald I.; Blank, Dave H. A.; Bouwmeester, Henny J. M.; Kessler, Vadim G.

2009-01-01

Modification of different zirconium propoxide precursors with H2dea was investigated by characterization of the isolated modified species. Upon modification of zirconium n-propoxide and [Zr(OnPr)(OiPr)3(iPrOH)]2 with ½ a mol equivalent of H2dea the complexes [Zr2(OnPr)6(OCH2CH2)2NH]2 (1) and [Zr2(OnPr)2(OiPr)4(OCH2CH2)2NH]2 (2) were obtained. However, 1H-NMR studies of these tetranuclear compounds showed that these are not time-stable either in solution or solid form. The effect of this time instability on material properties is demonstrated by light scattering and TEM experiments. Modification of zirconium isopropoxide with either ½ or 1 equivalent mol of H2dea results in formation of the trinuclear complex, Zr{η3μ2-NH(C2H4O)2}3[Zr(OiPr)3]2(iPrOH)2 (3) countering a unique nona-coordinated central zirconium atom. This complex 3 is one of the first modified zirconium propoxide precursors shown to be stable in solution for long periods of time. The particle size and morphology of the products of sol-gel synthesis are strongly dependent on the time factor and eventual heat treatment of the precursor solution. Reproducible sol-gel synthesis requires the use of solution stable precursors. PMID:20087472
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
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.
Sol-gel encapsulation of pullulanase in the presence of hybrid magnetic (Fe3O4-chitosan) nanoparticles improves thermal and operational stability.

PubMed

Long, Jie; Li, Xingfei; Zhan, Xiaobei; Xu, Xueming; Tian, Yaoqi; Xie, Zhengjun; Jin, Zhengyu

2017-06-01

Pullulanase was sol-gel encapsulated in the presence of magnetic chitosan/Fe 3 O 4 nanoparticles. The resulting immobilized pullulanase was characterized by scanning electron microscopy, vibrating sample magnetometry, Fourier transform infrared spectroscopy and thermogravimetric analysis. The results showed that the addition of pullulanase created a more regular surface on the sol-gel matrix and an enhanced magnetic response to an applied magnetic field. The maximal activity retention (83.9%) and specific activity (291.7 U/mg) of the immobilized pullulanase were observed under optimized conditions including an octyltriethoxysilane:tetraethoxysilane (OTES:TEOS) ratio of 1:2 and enzyme concentration of 0.484 mg/mL sol. The immobilized enzyme exhibited good thermal stability. When the temperature was above 60 °C, the immobilized pullulanase showed significantly higher activity than the free enzyme (p < 0.01); enzyme immobilized by simple sol-gel encapsulation and co-immobilized by crosslinking-encapsulation retained 52 and 69% of their initial activity after 5 h at 62 °C, respectively, compared to 11% for the free enzyme. Moreover, the stability of the pullulanase was improved by crosslinking-encapsulation, as the enzyme retained more than 85 and 81% of its original activity after 5 and 6 consecutive reuses, respectively, compared to 80 and 72% of its original activity for simple sol-gel encapsulated enzymes. This indicated the leakage of enzyme molecules through the pores of the gel was substantially abated by cross-linking. Such immobilized pullulanase provides high stability and ease of enzyme recovery, characteristics that are advantageous for applications in the food industry that involve continuous starch processing.
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.
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.
Large-Scale Precise Printing of Ultrathin Sol-Gel Oxide Dielectrics for Directly Patterned Solution-Processed Metal Oxide Transistor Arrays.

PubMed

Lee, Won-June; Park, Won-Tae; Park, Sungjun; Sung, Sujin; Noh, Yong-Young; Yoon, Myung-Han

2015-09-09

Ultrathin and dense metal oxide gate di-electric layers are reported by a simple printing of AlOx and HfOx sol-gel precursors. Large-area printed indium gallium zinc oxide (IGZO) thin-film transistor arrays, which exhibit mobilities >5 cm(2) V(-1) s(-1) and gate leakage current of 10(-9) A cm(-2) at a very low operation voltage of 2 V, are demonstrated by continuous simple bar-coated processes. © 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.
Aqueous silicates in biological sol-gel applications: new perspectives for old precursors.

PubMed

Coradin, Thibaud; Livage, Jacques

2007-09-01

Identification of silica sol-gel chemistry with silicon alkoxide hydrolysis and condensation processes is common in modern materials science. However, aqueous silicates exhibit several features indicating that they may be more suitable precursors for specific fields of research and applications related to biology and medicine. In this Account, we illustrate the potentialities of such aqueous precursors for biomimetic studies, bio-hybrid material design, and bioencapsulation routes. We emphasize that the natural relevance, the biocompatibility, and the low ecological impact of silicate chemistry may balance its lack of diversity, flexibility, and processability.
Magnetic and structural properties of CoFe 2O 4 thin films synthesized via a sol-gel process

NASA Astrophysics Data System (ADS)

dos S. Duque, J. G.; Macêdo, M. A.; Moreno, N. O.; Lopez, J. L.; Pfanes, H.-D.

2001-05-01

Using a sol-gel process having the coconut water as a precursor of organic chain, we synthesized thin films of cobalt ferrite. The films were characterized by using a SQUID magnetometer, an X-ray diffractometer, an X-ray spectrophotometer, Mössbauer spectroscopy and atomic force microscope. Co ferrite films annealed at 500°C for 2 h show grain sizes between 10 and 20 nm, grown as single-phase spinel structure and exhibit high coercivity and a moderate saturation magnetization (above 30 kOe).
Manufacture of Regularly Shaped Sol-Gel Pellets

NASA Technical Reports Server (NTRS)

Leventis, Nicholas; Johnston, James C.; Kinder, James D.

2006-01-01

An extrusion batch process for manufacturing regularly shaped sol-gel pellets has been devised as an improved alternative to a spray process that yields irregularly shaped pellets. The aspect ratio of regularly shaped pellets can be controlled more easily, while regularly shaped pellets pack more efficiently. In the extrusion process, a wet gel is pushed out of a mold and chopped repetitively into short, cylindrical pieces as it emerges from the mold. The pieces are collected and can be either (1) dried at ambient pressure to xerogel, (2) solvent exchanged and dried under ambient pressure to ambigels, or (3) supercritically dried to aerogel. Advantageously, the extruded pellets can be dropped directly in a cross-linking bath, where they develop a conformal polymer coating around the skeletal framework of the wet gel via reaction with the cross linker. These pellets can be dried to mechanically robust X-Aerogel.
Encapsulation of nanoclusters in dried gel materials via an inverse micelle/sol gel synthesis

DOEpatents

Martino, Anthony; Yamanaka, Stacey A.; Kawola, Jeffrey S.; Showalter, Steven K.; Loy, Douglas A.

1998-01-01

A dried gel material sterically entrapping nanoclusters of a catalytically active material and a process to make the material via an inverse micelle/sol-gel synthesis. A surfactant is mixed with an apolar solvent to form an inverse micelle solution. A salt of a catalytically active material, such as gold chloride, is added along with a silica gel precursor to the solution to form a mixture. To the mixture are then added a reducing agent for the purpose of reducing the gold in the gold chloride to atomic gold to form the nanoclusters and a condensing agent to form the gel which sterically entraps the nanoclusters. The nanoclusters are normally in the average size range of from 5-10 nm in diameter with a monodisperse size distribution.
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.
Fabrication and Anti-Oxidation Ability of SiC-SiO2 Coated Carbon Fibers Using Sol-Gel Method

PubMed Central

Yang, Guangyuan; Huang, Zhixiong; Wang, Xu; Wang, Bo

2018-01-01

The paper proposed a method to improve the anti-oxidation performance of carbon fibers (CF) at high temperature environment by coating silicon dioxide (SiO2) and silicon carbide (SiC). The modified sol-gel method had been used to ensure the proper interface between fibers and coating. We used polydimethylsiloxane and ethyl orthosilicate to make stable emulsion to uniformly disperse SiC nanoparticles. The modified SiO2/SiC coating had been coated on CF successfully. Compared with the untreated CF, the coated fibers started to be oxidized around 900 °C and the residual weight was 57% at 1400 °C. The oxidation mechanism had been discussed. The structure of SiC/SiO2 coated CF had been characterized by scanning electron microscope and X-ray diffraction analysis. Thermal gravimetric analysis was used to test the anti-oxidation ability of CF with different coatings. PMID:29495499
An improved biosensor for acetaldehyde determination using a bienzymatic strategy at poly(neutral red) modified carbon film electrodes.

PubMed

Ghica, Mariana Emilia; Pauliukaite, Rasa; Marchand, Nicolas; Devic, Eric; Brett, Christopher M A

2007-05-15

Improved biosensors for acetaldehyde determination have been developed using a bienzymatic strategy, based on a mediator-modified carbon film electrode and co-immobilisation of NADH oxidase and aldehyde dehydrogenase. Modification of the carbon film electrode with poly(neutral red) mediator resulted in a sensitive, low-cost and reliable NADH detector. Immobilisation of the enzymes was performed using encapsulation in a sol-gel matrix or cross-linking with glutaraldehyde. The bienzymatic biosensors were characterized by studying the influence of pH, applied potential and co-factors. The sol-gel and glutaraldehyde biosensors showed a linear response up to 60 microM and 100 microM, respectively, with detection limits of 2.6 microM and 3.3 microM and sensitivities were 1.7 microA mM(-1) and 5.6 microA mM(-1). The optimised biosensors showed good stability and good selectivity and have been tested for application for the determination of acetaldehyde in natural samples such as wine.
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.
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.
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.

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.
Production of mullite fibers

NASA Technical Reports Server (NTRS)

Tucker, Dennis S. (Inventor); Sparks, J. Scott (Inventor)

1991-01-01

Disclosed here is a process for making mullite fibers wherein a hydrolizable silicon compound and an aluminum compound in the form of a difunctional aluminum chelate are hydrolized to form sols using water and an alcohol with a catalytic amount of hydrochloric acid. The sols are mixed in a molar ratio of aluminum to silicon of 3 to 1 and, under polycondensation conditions, a fibrous gel is formed. From this gel the mullite fibers can be produced.
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.
Effect of silica coating on fracture strength of glass-infiltrated alumina ceramic cemented to dentin.

PubMed

Xie, Haifeng; Zhu, Ye; Chen, Chen; Gu, Ning; Zhang, Feimin

2011-10-01

To examine the availability of sol-gel processed silica coating for alumina-based ceramic bonding, and determine which silica sol concentration was appropriate for silica coating. Sixty disks of In-Ceram alumina ceramic were fabricated and randomly divided into 5 main groups. The disks received 5 different surface conditioning treatments: Group Al, sandblasted; Group AlC, sandblasted + silane coupling agent applied; Groups Al20C, Al30C, and Al40C, sandblasted, silica coating via sol-gel process prepared using 20 wt%, 30 wt%, and 40 wt% silica sols, and then silane coupling agent applied. Before bonding, one-step adhesives were applied on pre-prepared ceramic surfaces of all groups. Then, 60 dentin specimens were prepared and conditioned with phosphoric acid and one-step adhesive. Ceramic disks of all groups were cemented to dentin specimens with dual-curing resin cements. Fracture strength was determined at 24 h and after 20 days of storage in water. Groups Al20C, Al30C, and Al40C revealed significantly higher fracture strength than groups Al and AlC. No statistically significant difference in fracture strength was found between groups Al and AlC, or among groups Al20C, Al30C, and Al40C. Fracture strength values of all the groups did not change after 20 days of water storage. Sol-gel processed silica coating can enhance fracture strength of In-Ceram alumina ceramic after bonding to dentin, and different silica sol concentrations produced the same effects. Twenty days of water storage did not decrease the fracture strength.
Structural Modification of Sol-Gel Materials through Retro Diels-Alder Reaction

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

SHALTOUT,RAAFAT M.; LOY,DOUGLAS A.; MCCLAIN,MARK D.

1999-12-08

Hydrolysis and condensation of organically bridged bis-triethoxysilanes, (EtO){sub 3}Si-R-Si(OEt){sub 3}, results in the formation of three dimensional organic/inorganic hybrid networks (Equation 1). Properties of these materials, including porosity, are dependent on the nature of the bridging group, R. Flexible groups (akylene-spacers longer than five carbons in length) polymerize under acidic conditions to give non-porous materials. Rigid groups (such as arylene-, alkynylene-, or alkenylene) form non-porous, microporous, and macroporous gels. In many cases the pore size distributions are quite narrow. One of the motivations for preparing hybrid organic-inorganic materials is to extend the range of properties available with sol-gel systems bymore » incorporating organic groups into the inorganic network. For example, organically modified silica gels arc either prepared by co-polymerizing an organoalkoxysilane with a silica precursor or surface silylating the inorganic gel. This can serve to increase hydrophobicity or to introduce some reactive organic functionality. However, the type and orientation of these organic functionalities is difficult to control. Furthermore, many organoalkoxysilanes can act to inhibitor even prevent gelation, limiting the final density of organic functionalities. We have devised a new route for preparing highly functionalized pores in hybrid materials using bridging groups that are thermally converted into the desired functionalities after the gel has been obtained. In this paper, we present the preparation and characterization of bridged polysilsesquioxanes with Diels-Alder adducts as the bridging groups from the sol-gel polymerization of monomers 2 and 4. The bridging groups are constructed such that the retro Diela-Alder reaction releases the dienes and leaves the dienophiles as integral parts of the network polymers. In the rigid architecture of a xerogel, this loss of organic functionality should liberate sufficient space to modify the overall porosity. Furthermore, the new porosity will be functionalized with the dienophilic olefin bridging group. We also demonstrate that by changing the type of Diels-Alder adduct used as the bridging group, we can change the temperature at which the retro-Diels-Alder reaction will occur.« less
Manipulating surface wettability and oil absorbency of diatomite depending on processing and ambient conditions

NASA Astrophysics Data System (ADS)

Özen, İlhan; Şimşek, Süleyman; Okyay, Gamze

2015-03-01

In this study, a diatomite sample, which is a natural inorganic mineral with inherently high water and oil absorption capacity, was subjected to grinding before surface modification. Afterwards, the diatomite surface was modified via facile methods using a fluorocarbon (FC) chemical and stearic acid (SA) in addition to the sol-gel fluorosilanization (FS) process. The water and oil wettability, and oil absorbency properties of the unmodified and modified diatomites were investigated in addition to diatomite characterizations such as chemical content, surface area, particle size distribution, morphology, and modification efficiency. It was revealed that the wettability was changed completely depending on the surface modification agent and the media used, while the oil absorbency property surprisingly did not change. On the other hand, the oil absorbency was worsened by the grinding process, whereas the wettability was not affected.
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
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.
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.
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.
Coatings of titanium substrates with xCaO · (1 - x)SiO2 sol-gel materials: characterization, bioactivity and biocompatibility evaluation.

PubMed

Catauro, M; Papale, F; Bollino, F

2016-01-01

The objective of this study has been to develop low temperature sol-gel coatings to modify the surface of commercially pure titanium grade 4 (a material generally used in dental application) and to evaluate their bioactivity and biocompatibility on the substrate. Glasses of composition expressed by the following general formula xCaO · (1 - x)SiO2 (0.0
Biocompatible Nb2O5 thin films prepared by means of the sol-gel process.

PubMed

Velten, D; Eisenbarth, E; Schanne, N; Breme, J

2004-04-01

Thin biocompatible oxide films with an optimised composition and structure on the surface of titanium and its alloys can improve the implant integration. The preparation of these thin oxide layers with the intended improvement of the surface properties can be realised by means of the sol-gel process. Nb2O5 is a promising coating material for this application because of its extremely high corrosion resistance and thermodynamic stability. In this study, thin Nb2O5 layers ( < 200 nm) were prepared by spin coating of polished discs of cp-titanium with a sol consisting of a mixture of niobium ethoxide, butanol and acetylacetone. The thickness, phase composition, corrosion resistance and the wettability of the oxide layers were determined after an optimisation of the processing parameters for deposition of oxide without any organic impurities. The purity of the oxide layer is an important aspect in order to avoid a negative response to the cell adhesion. The biocompatibility of the oxide layers which was investigated by in vitro tests (morphology, proliferation rate, WST-1, cell spreading) is improved as compared to uncoated and TiO2 sol-gel coated cp-titanium concerning the spreading of cells, collagen I synthesis and wettability.
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.
A micro oxygen sensor based on a nano sol-gel TiO2 thin film.

PubMed

Wang, Hairong; Chen, Lei; Wang, Jiaxin; Sun, Quantao; Zhao, Yulong

2014-09-03

An oxygen gas microsensor based on nanostructured sol-gel TiO2 thin films with a buried Pd layer was developed on a silicon substrate. The nanostructured titania thin films for O2 sensors were prepared by the sol-gel process and became anatase after heat treatment. A sandwich TiO2 square board with an area of 350 μm × 350 μm was defined by both wet etching and dry etching processes and the wet one was applied in the final process due to its advantages of easy control for the final structure. A pair of 150 nm Pt micro interdigitated electrodes with 50 nm Ti buffer layer was fabricated on the board by a lift-off process. The sensor chip was tested in a furnace with changing the O2 concentration from 1.0% to 20% by monitoring its electrical resistance. Results showed that after several testing cycles the sensor's output becomes stable, and its sensitivity is 0.054 with deviation 2.65 × 10(-4) and hysteresis is 8.5%. Due to its simple fabrication process, the sensor has potential for application in environmental monitoring, where lower power consumption and small size are required.
Influence of polyols on the formation of nanocrystalline nickel ferrite inside silica matrices

NASA Astrophysics Data System (ADS)

Stoia, Marcela; Barvinschi, Paul; Barbu-Tudoran, Lucian; Bunoiu, Mădălin

2017-01-01

We have synthesized nickel ferrite/silica nanocomposites, using a modified sol-gel method that combines the sol-gel processing with the thermal decomposition of metal-organic precursors, leading to a homogenous dispersion of ferrite nanoparticles within the silica matrix and a narrow size distribution. We used as starting materials tetraethyl orthosilicate (TEOS) as source of silica, Fe(III) and Ni(II) nitrates as sources of metal cations, and polyols as reducing agent (polyvinyl alcohol, 1,4-butanediol and their mixture). TG/DTA coupled technique evidenced the redox interaction between the polyol and the mixture of metal nitrates during the heating of the gel, with formation of nickel ferrite precursors in the pores of the silica-gels. FT-IR spectroscopy confirmed the formation of metal carboxylates inside the silica-gels and the interaction of the polyols with the Si-OH groups of the polysiloxane network. X-ray diffractometry evidenced that in case of nanocomposites obtained by using a single polyol, nickel ferrite forms as single crystalline phase inside the amorphous silica matrix, while in case of using a mixture of polyols the nickel oxide appears as a secondary phase. TEM microscopy and elemental mapping evidenced the fine nature of the obtained nickel ferrite nanoparticles that are homogenously dispersed within the silica matrix. The obtained nanocomposites exhibit magnetic behavior very close to superparamagnetism slightly depending on the presence and nature of the organic compounds used in synthesis; the magnetization reached at 5 kOe magnetic field was 7 emu/g for all composites.
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.
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
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.
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.
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).

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.
Preparation of nanocrystalline TiN coated cubic boron nitride powders by a sol-gel process.

PubMed

Park, Hee S; Umer, M Adeel; Ryu, Ho J; Hong, Soon H

2011-01-01

Cubic boron nitride (cBN) particles coated with 20 wt% nanocrystalline TiN were prepared by coating the surface of cBN particles with TiO2, followed by nitridation with NH3 gas at 900 degrees C. Coating of TiO2 on cBN powders was accomplished by a sol-gel process from a solution of titanium (IV) isopropoxide and anhydrous ethanol. An amorphous TiO(x) layer of 50 nm thickness was homogenously formed on the surface of the cBN particles by the sol-gel process. The amorphous layer was then crystallized to an anatase TiO2 phase through calcination in air at 400 degrees C. The crystallized TiO2 layer was 50 nm in thickness, and the size of TiO2 particles comprising the layer was nearly 10 nm. The TiO2 on cBN surfaces was completely converted into nanocrystalline TiN of uniform particles 20 nm in size on cBN particles by nitridation under flowing NH3 gas.
Entrapment of subtilisin in ceramic sol-gel coating for antifouling applications.

PubMed

Regina, Viduthalai Rasheedkhan; Søhoel, Helmer; Lokanathan, Arcot Raghupathi; Bischoff, Claus; Kingshott, Peter; Revsbech, Niels Peter; Meyer, Rikke Louise

2012-11-01

Enzymes with antifouling properties are of great interest in developing nontoxic antifouling coatings. A bottleneck in developing enzyme-based antifouling coatings is to immobilize the enzyme in a suitable coating matrix without compromising its activity and stability. Entrapment of enzymes in ceramics using the sol-gel method is known to have several advantages over other immobilization methods. The sol-gel method can be used to make robust coatings, and the aim of this study was to explore if sol-gel technology can be used to develop robust coatings harboring active enzymes for antifouling applications. We successfully entrapped a protease, subtilisin (Savinase, Novozymes), in a ceramic coating using a sol-gel method. The sol-gel formulation, when coated on a stainless steel surface, adhered strongly and cured at room temperature in less than 8 h. The resultant coating was smoother and less hydrophobic than stainless steel. Changes in the coating's surface structure, thickness and chemistry indicate that the coating undergoes gradual erosion in aqueous medium, which results in release of subtilisin. Subtilisin activity in the coating increased initially, and then gradually decreased. After 9 months, 13% of the initial enzyme activity remained. Compared to stainless steel, the sol-gel-coated surfaces with active subtilisin were able to reduce bacterial attachment of both Gram positive and Gram negative bacteria by 2 orders of magnitude. Together, our results demonstrate that the sol-gel method is a promising coating technology for entrapping active enzymes, presenting an interesting avenue for enzyme-based antifouling solutions.
Electronic nose screening of ethanol release during sol-gel encapsulation. A novel non-invasive method to test silica polymerisation.

PubMed

Lovino, Magalí; Cardinal, M Fernanda; Zubiri, Diana B V; Bernik, Delia L

2005-12-15

Porous silica matrices prepared by sol-gel process yield biocompatible materials adequate for encapsulation of biomolecules or drugs. The procedure is simple and fast, but when alkoxyde precursors like tetraethoxysilane (TEOS) are used the polymerisation reaction leads to the formation of alcohol as a by-product, which can produce undesirable effects on the activity of entrapped enzymes or modify a drug release kinetic. Therefore, it is critical to determine that no remnant ethanol is left prior using or storing the obtained biomaterial. In this regard, the technique used in the alcohol determination should be non-invasive and non-destructive to preserve the encapsulation device intact and ready to use. In this work we have successfully used a portable electronic nose (e-nose) for the screening of silica polymerisation process during theophylline encapsulation. TEOS reaction was "smelt" since precursor pre-hydrolysis until the end of ethanol release, sensed directly at the headspace of matrices slabs. Measurements showed that ethanol was negligible since 10th day in polymeric slabs of 10 mm width and 2 cm diameter. This first use of e-nose following a polymerisation reaction opens a wide number of putative applications in pharmaceutical and biochemical fields.
Exploitation of the Sol-Gel Route in Processing of Ceramics and Composites.

DTIC Science & Technology

1987-07-10

titanium isoproporude which is first reacted with ethylene glycol and citnc acid at 120*C. This stabilizes the titanium isopropoxide against hydrolysis...the acid-catalyzed hy’drolysis of titanium isopropoxide . The sols gelled in * 2-4 da%s, and then w ere dried for 6-8 days. The drv gels were sintered...hydrolysis and peptization of titanium isopropoxide in a variety of simple acids (namely, nitric, hydrochloric, and acetic) was evaluated for the preparation
Domain Engineered Magnetoelectric Thin Films for High Sensitivity Resonant Magnetic Field Sensors

DTIC Science & Technology

2011-12-01

synthesis and texture analysis Sol-gel deposition and RF sputtering process was developed for deposition of PZT on Pt/Ti/Si02/Si (hereafter...well textured (i.e. with preferred crystalline orientation). To texture and obtain crack-free thick PZT RF films, we employed pre- treated substrates...and post-deposition annealing. One pre-treatment was the use of seed layer of textured PZT sol-gel thin film of thickness 65-85nm [1]. • Oean
Role of precursors and coating polymers in sol-gel chemistry toward enhanced selectivity and efficiency in solid phase microextraction.

PubMed

Bagheri, Habib; Piri-Moghadam, Hamed; Ahdi, Tayebeh

2012-09-12

To evaluate the selectivity and efficiency of solid phase microextraction (SPME) fiber coatings, synthesized by sol-gel technology, roles of precursors and coating polymers were extensively investigated. An on-line combination of capillary microextraction (CME) technique and high performance liquid chromatography (HPLC) was set up to perform the investigation. Ten different fiber coatings were synthesized in which five of them contained only the precursor and the rests were prepared using both the precursor and coating polymer. All the coatings were chemically bonded to the inner surface of copper tubes, intended to be used as the CME device and already functionalized by self-assembly monolayers of 3-(mercaptopropyl)trimethoxysilane (3MPTMOS). The selected precursors included tetramethoxysilane (TMOS), 3-(trimethoxysilyl)propylmethacrylate (TMSPMA), 3-(triethoxysilyl)-propylamine (TMSPA), 3MPTMOS, [3-(2,3-epoxypropoxy)-propyl]-trimethoxysilane (EPPTMOS) while poly(ethyleneglycol) (PEG) was chosen as the coating polymer. The effects of different precursors on the extraction efficiency and selectivity, was studied by selecting a list of compounds ranging from non-polar to polar ones, i.e. polycyclic aromatic hydrocarbon, herbicides, estrogens and triazines. The results from CME-HPLC analysis revealed that there is no significant difference between precursors, except TMOS, in which has the lowest extraction efficiency. Most of the selected precursors have rather similar interactions toward the selected analytes which include Van der Walls, dipole-dipole and hydrogen bond while TMOS has only dipole-dipole interaction and therefore the least efficiency. TMOS is silica but the other sorbents are organically modified silica (ORMOSIL). Our investigation revealed that it is rather impossible to prepare a selective coating using conventional sol-gel methodologies. The comparison study performed among the fiber coatings contained only a precursor and those synthesized by a precursor along with coating polymer proved that the extraction efficiency obtained for all coatings are the same. This is an indication that by selecting the appropriate precursor there is no need to use any coating polymer. In overall, a fiber coating in sol-gel process could be synthesize with no coating polymer which leads to faster, easier, cheaper and more controllable synthesis. Copyright © 2012 Elsevier B.V. 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
Encapsulation of nanoclusters in dried gel materials via an inverse micelle/sol gel synthesis

DOEpatents

Martino, A.; Yamanaka, S.A.; Kawola, J.S.; Showalter, S.K.; Loy, D.A.

1998-09-29

A dried gel material sterically entrapping nanoclusters of a catalytically active material and a process to make the material via an inverse micelle/sol-gel synthesis are disclosed. A surfactant is mixed with an apolar solvent to form an inverse micelle solution. A salt of a catalytically active material, such as gold chloride, is added along with a silica gel precursor to the solution to form a mixture. To the mixture are then added a reducing agent for the purpose of reducing the gold in the gold chloride to atomic gold to form the nanoclusters and a condensing agent to form the gel which sterically entraps the nanoclusters. The nanoclusters are normally in the average size range of from 5--10 nm in diameter with a monodisperse size distribution. 1 fig.
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.
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.
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.
Preparation and characterization of polydimethylsiloxane/poly(vinylalcohol) coated solid phase microextraction fibers using sol-gel technology.

PubMed

Lopes, Alexandre Leite; Augusto, Fabio

2004-11-12

The applicability of a composite composed of polydimethylsiloxane (PDMS) and poly(vinyl alcohol) (PDMS/PVA) as coating sorbent for SPME fibers is demonstrated here. Fused silica (FS) fibers were coated with PDMS/PVA composite through a sol-gel process, using methyltrimethoxysilane as reticulating agent. The chemical and physical properties of the sol-gel PDMS/PVA composite were determined by infrared spectroscopy and thermogravimetric analysis. Electron scanning microscopy of the prepared fibers, showed that the coating obtained was highly microporous, having a thickness of approximately 5 microm. The fibers were tested for the headspace extraction of several organic compounds (o-xylene, naphthalene, ethyl caprate, p-chlorotoluene and PCB) prior to gas chromatographic analysis. The extractive capacity of the PDMS/PVA coating was found to be superior to that of pure conventional PDMS fibers.
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.
Down- and up-conversion luminescent carbon dot fluid: inkjet printing and gel glass fabrication.

PubMed

Wang, Fu; Xie, Zheng; Zhang, Bing; Liu, Yun; Yang, Wendong; Liu, Chun-yan

2014-04-07

Room temperature liquid-like nanoparticles have emerged as an exciting new research and development area, because their properties could be tailored over a broad range by manipulating geometric and chemical characteristics of the inorganic core and organic canopy. However, related applications are rarely reported due to the multi-step synthesis process and potential toxicity of cadmium based nanomaterials. In this study, we prepared inexpensive and eco-friendly carbon dot fluid by the direct thermal decomposition method. The carbon dot fluid can be excited from UV to near infrared light, and can be prepared as highly concentrated luminescent ink or incorporated into sol-gel derived organically modified silicate glass, suggesting that it has great application potential in the field of printable electronics, solid state lighting and so on.
Sol-Gel Entrapped Levonorgestrel Antibodies: Activity and Structural Changes as a Function of Different Polymer Formats

PubMed Central

Shalev, Moran; Miriam, Altstein

2011-01-01

The paper describes development of a sol-gel based immunoaffinity method for the steroid hormone levonorgestrel (LNG) and the effects of changes in the sol-gel matrix format on the activity of the entrapped antibodies (Abs) and on matrix structure. The best sol-gel format for Ab entrapment was found to be a tetramethoxysilane (TMOS) based matrix at a TMOS:water ratio of 1:8, containing 10% polyethylene glycol (PEG) of MW 0.4 kDa. Addition of higher percentages of PEG or a higher MW PEG did not improve activity. No activity was obtained with a TMOS:water ratio of 1:12, most likely because of the very dense polymer that resulted from these polymerization conditions. Only minor differences in the non-specific binding were obtained with the various formats. TMOS was found to be more effective than tetrakis (2-hydroxyethyl)orthosilicate (THEOS) for entrapment of anti-levonorgestrel (LNG) Abs. However, aging the THEOS-based sol-gel for a few weeks at 4 °C stabilized the entrapped Abs and increased its binding capacity. Confocal fluorescent microscopy with fluorescein isothiocyanate (FITC) labeled immunoglobulines (IgGs) entrapped in the sol-gel matrix showed that the entrapped Abs were distributed homogenously within the gel. Scanning electron microscopy (SEM) images have shown the diverse structures of the various sol-gel formats and precursors. PMID:28880001
Synthesis of bioactive organic-inorganic nanohybrid for bone repair through sol-gel processing.

PubMed

Miyazaki, Toshiki; Ohtsuki, Chikara; Tanihara, Masao

2003-12-01

So-called bioactive ceramics have been attractive because they form bone-like apatite on their surfaces to bond directly to living bone when implanted in bony defects. However, they are much more brittle and much less flexible than natural bone. Organic-inorganic hybrids consisting of flexible organic polymers and the essential constituents of the bioactive ceramics (i.e., Si-OH groups and Ca2+ ions) are useful as novel bone substitutes, because of their bioactivity and mechanical properties analogous to those of natural bone. In the present study, organic-inorganic nanohybrids were synthesized from hydroxyethylmethacrylate (HEMA) and methacryloxypropyltrimethoxysilane (MPS), as well as various calcium salts. Bioactivity of the synthesized hybrids was assessed in vitro by examining their acceptance of apatite deposition in simulated body fluid (Kokubo solution). The prepared hybrids formed apatite in Kokubo solution when they were modified with calcium chloride (CaCl2) at 5 or 10 mol% of the total of MPS and HEMA. Deposition of a kind of calcium phosphate was observed for the hybrids modified with calcium acetate (Ca(CH3COO)2), although it could not be identified with apatite. The addition of glycerol up to 10 mol% of the total of MPS and HEMA or water up to 20 mol% as plasticizers did not appreciably decrease the acceptance of apatite formation of the hybrids. These findings allow wide selectivity in the design of bioactive nanohybrids developed by organic modification of the Si-OH group and calcium ion through sol-gel processing. Such nanohybrids have potential as novel bone substitutes with both high bioactivity and high flexibility.
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 Â© 2016 Elsevier B.V. All rights reserved.
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.

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.
Influence of surfactants on the release behaviour and structural properties of sol-gel derived silica xerogels embedded with metronidazole.

PubMed

Czarnobaj, Katarzyna; Sawicki, Wiesław

2013-01-01

The aim of this study was to obtain stable and controlled release silica xerogels containing metronidazole (MT) prepared with surfactants with different charges: cetyltrimethylammonium bromide (CTAB), sodium dodecyl sulphate (SDS) and hydroxypropyl cellulose (HPC), which could be the promising carrier materials used as the implantable drug delivery systems. The xerogels were prepared by the sol-gel method. The influence of various formulation precursors on porosity parameters and drug release were investigated. Addition of surfactants showed a promising result in controlling the MT release. Dissolution study revealed increased release of MT from silica modified SDS and CTAB, whereas the release of MT from silica modified HPC considerably decreased, in comparison with unmodified silica. The addition of surfactants showed slight changes in porosity parameters. All xerogels are characterized by a highly developed surface area (701-642 m(2) g(-1)) and mesoporous structure. The correlation between pore size obtained matrices and release rate of drug was also observed. Based on the presented results of this study, it may be stated that applied xerogel matrices: pure silica and surfactants-modified silica could be promising candidates for the formulation in local delivery systems.
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.
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.
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.
Durable polyorganosiloxane superhydrophobic films with a hierarchical structure by sol-gel and heat treatment method

NASA Astrophysics Data System (ADS)

Jiang, Zhenlin; Fang, Shuying; Wang, Chaosheng; Wang, Huaping; Ji, Chengchang

2016-12-01

For a surface to be superhydrophobic a combination of surface roughness and low surface energy is required. In this study, polyorganosiloxane superhydrophobic surfaces were fabricated using a sol-gel and heat treatment process followed by coating with a nanosilica (SiO2) sol and organosiloxane 1, 1, 1, 3, 5, 5, 5-heptamethyl-3-[2-(trimethoxysilyl)ethyl]-trisiloxane (β-HPEOs). The nano-structure was superimposed using self-assembled, surface-modified silica nanoparticles, forming two-dimensional hierarchical structures. The water contact angle (WCA) of polyorganosiloxane superhydrophobic surface was 143.7 ± 0.6°, which was further increased to 156.7 ± 1.1° with water angle hysteresis of 2.5 ± 0.6° by superimposing nanoparticles using a heat treatment process. An analytical characterization of the surface revealed that the nano-silica and polyorganosiloxane formed a micro/nano structure on the films and the wetting behaviour of the films changed from hydrophilic to superhydrophobic. The WCA of these films were 143.7 ± 0.6° and at heat treatment temperatures of less than 400 °C, the WCA increased from 144.5 ± 0.7° to 156.7 ± 1.1°. The prepared superhydrophobic films were stable even after heat treatment at 430 °C for 30 min and their superhydrophobicity was durable for more than 120 days. The effects of heat treatment process on the surface chemistry structure, wettability and morphology of the polyorganosiloxane superhydrophobic films were investigated in detail. The results indicated that the stability of the chemical structure was required to yield a thermally-stable superhydrophobic surface.
Ultrafast Sol-Gel Synthesis of Graphene Aerogel Materials

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

Lim, Mathew; Hu, Matthew; Manandhar, Sandeep

2015-12-01

Graphene aerogels derived from graphene-oxide (GO) starting materials recently have been shown to exhibit a combination of high electrical conductivity, chemical stability, and low cost that has enabled a range of electrochemical applications. Standard synthesis protocols for manufacturing graphene aerogels require the use of sol-gel chemical reactions that are maintained at high temperatures for long periods of time ranging from 12 hours to several days. Here we report an ultrafast, acid-catalyzed sol-gel formation process in acetonitrile in which wet GO-loaded gels are realized within 2 hours at temperatures below 45°C. Spectroscopic and electrochemical analysis following supercritical drying and pyrolysis confirmsmore » the reduction of the GO in the aerogels to sp2 carbon crystallites with no residual carbon–nitrogen bonds from the acetonitrile or its derivatives. This rapid synthesis enhances the prospects for large-scale manufacturing of graphene aerogels for use in numerous applications including sorbents for environmental toxins, support materials for electrocatalysis, and high-performance electrodes for electrochemical capacitors and solar cells.« less
Structural and Luminescence Properties of Lu2O3:Eu3+ F127 Tri-Block Copolymer Modified Thin Films Prepared by Sol-Gel Method

PubMed Central

de Jesus Morales Ramírez, Angel; Hernández, Margarita García; Murillo, Antonieta García; de Jesús Carrillo Romo, Felipe; Palmerin, Joel Moreno; Velazquez, Dulce Yolotzin Medina; Jota, María Luz Carrera

2013-01-01

Lu2O3:Eu3+ transparent, high density, and optical quality thin films were prepared using the sol-gel dip-coating technique, starting with lutetium and europium nitrates as precursors and followed by hydrolysis in an ethanol-ethylene glycol solution. Acetic acid and acetylacetonate were incorporated in order to adjust pH and as a sol stabilizer. In order to increment the thickness of the films and orient the structure, F127 Pluronic acid was incorporated during the sol formation. Structural, morphological, and optical properties of the films were investigated for different F127/Lu molar ratios (0–5) in order to obtain high optical quality films with enhanced thickness compared with the traditional method. X-ray diffraction (XRD) shows that the films present a highly oriented cubic structure <111> beyond 1073 K for a 3-layer film, on silica glass substrates. The thickness, density, porosity, and refractive index evolution of the films were investigated by means of m-lines microscopy along with the morphology by scanning electron microscope (SEM) and luminescent properties. PMID:28809336
Development and Characterization of Titanium Dioxide Gel with Encapsulated Bacteriorhodopsin for Hydrogen Production.

PubMed

Johnson, Kaitlin E; Gakhar, Sukriti; Risbud, Subhash H; Longo, Marjorie L

2018-06-06

We study bacteriorhodopsin (BR) in its native purple membrane encapsulated within amorphous titanium dioxide, or titania, gels and in the presence of titania sol-particles to explore this system for hydrogen production. Förster resonance energy transfer between BR and titanium dioxide sol particles was used to conclude that there is nanometer-scale proximity of bacteriorhodopsin to the titanium dioxide. The detection of BR-titania sol aggregates by fluorescence anisotropy and particle sizing indicated the affinity amorphous titania has for BR without the use of additional cross-linkers. UV-Visible spectroscopy of BR-titania gels show that methanol addition did not denature BR at a 25 mM concentration presence as a sacrificial electron donor. Additionally, confinement of BR in the gels significantly limited protein denaturation at higher concentration of added methanol or ethanol. Subsequently, titania gels fabricated through the sol-gel process using a titanium ethoxide precursor, water and the addition of 25 mM methanol were used to encapsulate BR and a platinum reduction catalyst for the production of hydrogen gas under white light irradiation. The inclusion of 5 µM bacteriorhodopsin resulted in a hydrogen production rate of about 3.8 µmole hydrogen mL -1 hr -1 , an increase of 52% compared to gels containing no protein. Electron transfer and proton pumping by BR in close proximity to the titania gel surface are feasible explanations for the enhanced production of hydrogen without the need to crosslink BR to the titania gel. This work sets the stage for further developments of amorphous, rather than crystalline, titania-encapsulated bacteriorhodopsin for solar-driven hydrogen production through water-splitting.
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
Sol-gel synthesis and characterization of SiO{sub 2}/PEG hybrid materials containing quercetin as implants with antioxidant properties

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

Catauro, Michelina; Bollino, Flavia; Gloria, Antonio

2016-05-18

In the present work, Silica/Polyethylene glycol (PEG) hybrid nanocomposites containing an antioxidant agent, the quercetin, were synthesized via sol-gel to be used as implants with antioxidant properties. Fourier transform infrared (FT-IR) analysis proved that a modification of both polymer and quercetin occurs due to synthesis process. Scanning electron microscope (SEM) showed that the proposed materials were hybrid nanocomposites. The bioactivity was ascertained by soaking the samples in a simulated body fluid (SBF).
Li+ ions diffusion into sol-gel V2O5 thin films: electrochromic properties

NASA Astrophysics Data System (ADS)

Benmoussa, M.; Outzourhit, A.; Bennouna, A.; Ihlal, A.

2009-10-01

V{2}O{5} thin films were prepared by the sol-gel spin coating process. The Li+ ions insertion effect on optical and electrochromic properties of those films was studied. The diffusion coefficient was calculated using both cyclic voltammograms and chronoamperometric curves. The amount x of Li+ ions in LixV{2}O{5} was also calculated. Finally, the electrochromic performance evolution characteristics such as the reversibility, coloration efficiency, coloration memory stability and response time were studied.
Synthesis and thermal stability of zirconia and yttria-stabilized zirconia microspheres.

PubMed

Leib, Elisabeth W; Vainio, Ulla; Pasquarelli, Robert M; Kus, Jonas; Czaschke, Christian; Walter, Nils; Janssen, Rolf; Müller, Martin; Schreyer, Andreas; Weller, Horst; Vossmeyer, Tobias

2015-06-15

Zirconia microparticles produced by sol-gel synthesis have great potential for photonic applications. To this end, identifying synthetic methods that yield reproducible control over size uniformity is important. Phase transformations during thermal cycling can disintegrate the particles. Therefore, understanding the parameters driving these transformations is essential for enabling high-temperature applications. Particle morphology is expected to influence particle processability and stability. Yttria-doping should improve the thermal stability of the particles, as it does in bulk zirconia. Zirconia and YSZ particles were synthesized by improved sol-gel approaches using fatty acid stabilizers. The particles were heated to 1500 °C, and structural and morphological changes were monitored by SEM, ex situ XRD and high-energy in situ XRD. Zirconia particles (0.4-4.3 μm in diameter, 5-10% standard deviation) synthesized according to the modified sol-gel approaches yielded significantly improved monodispersities. As-synthesized amorphous particles transformed to the tetragonal phase at ∼450 °C with a volume decrease of up to ∼75% and then to monoclinic after heating from ∼650 to 850 °C. Submicron particles disintegrated at ∼850 °C and microparticles at ∼1200 °C due to grain growth. In situ XRD revealed that the transition from the amorphous to tetragonal phase was accompanied by relief in microstrain and the transition from tetragonal to monoclinic was correlated with the tetragonal grain size. Early crystallization and smaller initial grain sizes, which depend on the precursors used for particle synthesis, coincided with higher stability. Yttria-doping reduced grain growth, stabilized the tetragonal phase, and significantly improved the thermal stability of the particles. Copyright © 2015 The Authors. Published by Elsevier Inc. All rights reserved.
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…
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.
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
Enantioseparation on cellulose dimethylphenylcarbamate-modified zirconia monolithic columns by reversed-phase capillary electrochromatography.

PubMed

Kumar, Avvaru Praveen; Park, Jung Hag

2010-06-25

This work reports the preparation of monolithic zirconia chiral columns for separation of enantiomeric compounds by capillary electrochromatography (CEC). Using sol-gel technology, a porous monolith having interconnected globular-like structure with through-pores is synthesized in the capillary column as a first step in the synthesis of monolithic zirconia chiral capillary columns. In the second step, the surface of the monolith is modified by coating with cellulose tris(3,5-dimethylphenylcarbamate) (CDMPC) as the chiral stationary phase to obtain a chiral column (CDMPCZM). The process of the preparation of the zirconia monolithic capillary column was investigated by varying the concentrations of the components of the sol solution including polyethylene glycol, water and acetic acid. CDMPCZM is mechanically stable and no bubble formation was detected with the applied current of up to 30 microA. The enantioseparation behavior of the CDMPCZM columns was investigated by separating a set of 10 representative chiral compounds by varying the applied voltage and pH and organic composition of the aqueous organic mobile phases. Copyright 2010 Elsevier B.V. All rights reserved.
Fe-Doped Sol-Gel Glasses and Glass-Ceramics for Magnetic Hyperthermia

PubMed Central

Fiume, Elisa; Miola, Marta; Leone, Federica; Onida, Barbara; Laviano, Francesco; Gerbaldo, Roberto; Verné, Enrica

2018-01-01

This work deals with the synthesis and characterization of novel Fe-containing sol-gel materials obtained by modifying the composition of a binary SiO2-CaO parent glass with the addition of Fe2O3. The effect of different processing conditions (calcination in air vs. argon flowing) on the formation of magnetic crystalline phases was investigated. The produced materials were analyzed from thermal (hot-stage microscopy, differential thermal analysis, and differential thermal calorimetry) and microstructural (X-ray diffraction) viewpoints to assess both the behavior upon heating and the development of crystalline phases. N2 adsorption–desorption measurements allowed determining that these materials have high surface area (40–120 m2/g) and mesoporous texture with mesopore size in the range of 18 to 30 nm. It was assessed that the magnetic properties can actually be tailored by controlling the Fe content and the environmental conditions (oxidant vs. inert atmosphere) during calcination. The glasses and glass-ceramics developed in this work show promise for applications in bone tissue healing which require the use of biocompatible magnetic implants able to elicit therapeutic actions, such as hyperthermia for bone cancer treatment. PMID:29361763
Ambient pressure dried tetrapropoxysilane-based silica aerogels with high specific surface area

NASA Astrophysics Data System (ADS)

Parale, Vinayak G.; Han, Wooje; Jung, Hae-Noo-Ree; Lee, Kyu-Yeon; Park, Hyung-Ho

2018-01-01

In the present paper, we report the synthesis of tetrapropoxysilane (TPOS)-based silica aerogels with high surface area and large pore volume. The silica aerogels were prepared by a two-step sol-gel process followed by surface modification via a simple ambient pressure drying approach. In order to minimize drying shrinkage and obtain hydrophobic aerogels, the surface of the alcogels was modified using trichloromethylsilane as a silylating agent. The effect of the sol-gel compositional parameters on the polymerization of aerogels prepared by TPOS, one of the precursors belonging to the Si(OR)4 family, was reported for the first time. The oxalic acid and NH4OH concentrations were adjusted to achieve good-quality aerogels with high surface area, low density, and high transparency. Controlling the hydrolysis and condensation reactions of the TPOS precursor turned out to be the most important factor to determine the pore characteristics of the aerogel. Highly transparent aerogels with high specific surface area (938 m2/g) and low density (0.047 g/cm3) could be obtained using an optimized TPOS/MeOH molar ratio with appropriate concentrations of oxalic acid and NH4OH.
Osteoblast responses to different oxide coatings produced by the sol-gel process on titanium substrates.

PubMed

Ochsenbein, Anne; Chai, Feng; Winter, Stefan; Traisnel, Michel; Breme, Jürgen; Hildebrand, Hartmut F

2008-09-01

In order to improve the osseointegration of endosseous implants made from titanium, the structure and composition of the surface were modified. Mirror-polished commercially pure (cp) titanium substrates were coated by the sol-gel process with different oxides: TiO(2), SiO(2), Nb(2)O(5) and SiO(2)-TiO(2). The coatings were physically and biologically characterized. Infrared spectroscopy confirmed the absence of organic residues. Ellipsometry determined the thickness of layers to be approximately 100nm. High resolution scanning electron microscopy (SEM) and atomice force microscopy revealed a nanoporous structure in the TiO(2) and Nb(2)O(5) layers, whereas the SiO(2) and SiO(2)-TiO(2) layers appeared almost smooth. The R(a) values, as determined by white-light interferometry, ranged from 20 to 50nm. The surface energy determined by the sessile-drop contact angle method revealed the highest polar component for SiO(2) (30.7mJm(-2)) and the lowest for cp-Ti and 316L stainless steel (6.7mJm(-2)). Cytocompatibility of the oxide layers was investigated with MC3T3-E1 osteoblasts in vitro (proliferation, vitality, morphology and cytochemical/immunolabelling of actin and vinculin). Higher cell proliferation rates were found in SiO(2)-TiO(2) and TiO(2), and lower in Nb(2)O(5) and SiO(2); whereas the vitality rates increased for cp-Ti and Nb(2)O(5). Cytochemical assays showed that all substrates induced a normal cytoskeleton and well-developed focal adhesion contacts. SEM revealed good cell attachment for all coating layers. In conclusion, the sol-gel-derived oxide layers were thin, pure and nanostructured; consequent different osteoblast responses to those coatings are explained by the mutual action and coadjustment of different interrelated surface parameters.

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.
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.
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.
One-pot preparation of silica-supported hybrid immobilized metal affinity adsorbent with macroporous surface based on surface imprinting coating technique combined with polysaccharide incorporated sol--gel process.

PubMed

Li, Feng; Li, Xue-Mei; Zhang, Shu-Sheng

2006-10-06

A simple and reliable one-pot approach using surface imprinting coating technique combined with polysaccharide incorporated sol-gel process was established to synthesize a new organic-inorganic hybrid matrix possessing macroporous surface and functional ligand. Using mesoporous silica gel being a support, immobilized metal affinity adsorbent with a macroporous shell/mesoporous core structure was obtained after metal ion loading. In the prepared matrix, covalently bonded coating and morphology manipulation on silica gel was achieved by using one-pot sol-gel process starting from an inorganic precursor, -glycidoxypropyltrimethoxysiloxane (GPTMS), and a functional biopolymer, chitosan (CS) at the atmosphere of imprinting polyethylene glycol (PEG). Self-hydrolysis of GPTMS, self-condensation, and co-condensation of silanol groups (Si-OH) from siloxane and silica gel surface, and in situ covalent cross-linking of CS created an orderly coating on silica gel surface. PEG extraction using hot ammonium hydroxide solution gave a chemically and mechanically stabilized pore structure and deactivated residual epoxy groups. The prepared matrix was characterized by using X-ray energy dispersion spectroscopy (EDX), scanning electron microscopy (SEM) and mercury intrusion porosimetry. The matrix possessed a high capacity for copper ion loading. Protein adsorption performance of the new immobilized metal affinity adsorbent was evaluated by batch adsorption and column chromatographic experiment using bovine serum albumin (BSA) as a simple model protein. Under the optimized coating conditions, the obtained macroporous surface resulted in a fast kinetics and high capability for protein adsorption, while the matrix non-charged with metal ions offered a low non-specific adsorption.
Down- and up-conversion luminescent carbon dot fluid: inkjet printing and gel glass fabrication

NASA Astrophysics Data System (ADS)

Wang, Fu; Xie, Zheng; Zhang, Bing; Liu, Yun; Yang, Wendong; Liu, Chun-Yan

2014-03-01

Room temperature liquid-like nanoparticles have emerged as an exciting new research and development area, because their properties could be tailored over a broad range by manipulating geometric and chemical characteristics of the inorganic core and organic canopy. However, related applications are rarely reported due to the multi-step synthesis process and potential toxicity of cadmium based nanomaterials. In this study, we prepared inexpensive and eco-friendly carbon dot fluid by the direct thermal decomposition method. The carbon dot fluid can be excited from UV to near infrared light, and can be prepared as highly concentrated luminescent ink or incorporated into sol-gel derived organically modified silicate glass, suggesting that it has great application potential in the field of printable electronics, solid state lighting and so on.Room temperature liquid-like nanoparticles have emerged as an exciting new research and development area, because their properties could be tailored over a broad range by manipulating geometric and chemical characteristics of the inorganic core and organic canopy. However, related applications are rarely reported due to the multi-step synthesis process and potential toxicity of cadmium based nanomaterials. In this study, we prepared inexpensive and eco-friendly carbon dot fluid by the direct thermal decomposition method. The carbon dot fluid can be excited from UV to near infrared light, and can be prepared as highly concentrated luminescent ink or incorporated into sol-gel derived organically modified silicate glass, suggesting that it has great application potential in the field of printable electronics, solid state lighting and so on. Electronic supplementary information (ESI) available: Details of FTIR, XRD and DLS of CDF, optical properties of CDF, TEM images of other obtained products, luminescent spectra of CDF at different temperatures, and the optical photographs of CDF inks and silica glasses with different concentrations under normal, UV and 800 nm light. See DOI: 10.1039/c3nr05869g
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.
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
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.
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.
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.
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.
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.
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.
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.
Synthesis of PbS/TiO2 nanocomposite materials using the sol-gel process via the incorporation of lead thiolates

NASA Astrophysics Data System (ADS)

Patel, Khushikumari

PbS/TiO2 nanocomposites were prepared by two methods using the sol-gel process: a one step process and a multi-step process. The incorporation of 3-mercaptopropionic acid, followed by the addition of Pb2+ generated covalently incorporated lead thiolate precursors which can then be converted to PbS/TiO2 nanocomposites by controlled thermal decomposition. Various ratios of bifunctional linker to matrix were used to monitor the incorporation of functional groups of the ceramic matrix, and the sol-gel process was used to produce a high yield ceramic materials. This allows solutions to chemically bind and form solid state ceramics, while allowing complex compounds to combine with a high degree of homogeneity. 3-mercaptoproprionic acid, was added to the titania gel, and as a source of sulfur component to bind to the titania. PbS/TiO2 nanocomposites were studied using FTIR spectroscopy. The covalent bonding between PbS and the titania ceramics was also confirmed with the signal intensity in the infrared spectra. The success of the covalent bond between the thiolate and ceramics led to possibility of nanocomposites. X-ray diffraction was used analyze the structure of the nanocomposites X-ray diffraction results showed lead sulfide nanocrystals in the ceramic matrix as well as the size of the particles. The presence of crystalline PbS and particle size was determined using powder X-ray diffraction.
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.
Processing and Characterization of Sol-Gel Cerium Oxide Microspheres

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

McClure, Zachary D.; Padilla Cintron, Cristina

Of interest to space exploration and power generation, Radioisotope Thermoelectric Generators (RTGs) can provide long-term power to remote electronic systems without the need for refueling or replacement. Plutonium-238 (Pu-238) remains one of the more promising materials for thermoelectric power generation due to its high power density, long half-life, and low gamma emissions. Traditional methods for processing Pu-238 include ball milling irregular precipitated powders before pressing and sintering into a dense pellet. The resulting submicron particulates of Pu-238 quickly accumulate and contaminate glove boxes. An alternative and dust-free method for Pu-238 processing is internal gelation via sol-gel techniques. Sol-gel methodology createsmore » monodisperse and uniform microspheres that can be packed and pressed into a pellet. For this study cerium oxide microspheres were produced as a surrogate to Pu-238. The similar electronic orbitals between cerium and plutonium make cerium an ideal choice for non-radioactive work. Before the microspheres can be sintered and pressed they must be washed to remove the processing oil and any unreacted substituents. An investigation was performed on the washing step to find an appropriate wash solution that reduced waste and flammable risk. Cerium oxide microspheres were processed, washed, and characterized to determine the effectiveness of the new wash solution.« less
A Micro Oxygen Sensor Based on a Nano Sol-Gel TiO2 Thin Film

PubMed Central

Wang, Hairong; Chen, Lei; Wang, Jiaxin; Sun, Quantao; Zhao, Yulong

2014-01-01

An oxygen gas microsensor based on nanostructured sol-gel TiO2 thin films with a buried Pd layer was developed on a silicon substrate. The nanostructured titania thin films for O2 sensors were prepared by the sol-gel process and became anatase after heat treatment. A sandwich TiO2 square board with an area of 350 μm × 350 μm was defined by both wet etching and dry etching processes and the wet one was applied in the final process due to its advantages of easy control for the final structure. A pair of 150 nm Pt micro interdigitated electrodes with 50 nm Ti buffer layer was fabricated on the board by a lift-off process. The sensor chip was tested in a furnace with changing the O2 concentration from 1.0% to 20% by monitoring its electrical resistance. Results showed that after several testing cycles the sensor's output becomes stable, and its sensitivity is 0.054 with deviation 2.65 × 10−4 and hysteresis is 8.5%. Due to its simple fabrication process, the sensor has potential for application in environmental monitoring, where lower power consumption and small size are required. PMID:25192312

Spherical LDH-Ag°-montmorillonite heterocoagulated system with a pH-dependent sol-gel structure for controlled accessibility of AgNPs immobilized on the clay lamellae.

PubMed

Deák, Ágota; Janovák, László; Tallósy, Szabolcs Péter; Bitó, Tamás; Sebők, Dániel; Buzás, Norbert; Pálinkó, István; Dékány, Imre

2015-02-17

Aqueous suspensions of spherical ZnMgAl-layered double hydroxides [LDH(sph)] and antibacterial silver nanoparticles (AgNPs) deposited on the lamellae of montmorillonite were used for the synthesis of composites, which behave like coherent gels at low pH (≲4.5) and incoherent sols at higher pH (≳4.5). The composition of the composite was chosen as LDH(sph)/Ag°-montm. = 25:75 wt % in order to ensure a sol-gel transition that can also be characterized by viscometry. This pH-sensitive heterocoagulated system consisting of oppositely charged colloid particles was suitable for the release of antimicrobial AgNPs immobilized on the clay lamellae via a pH-controlled gel-sol transition. The heterocoagulation process was also characterized by surface charge titration measurements. Spherical LDH/Ag°-montmorillonite composite samples were identified by X-ray diffraction (XRD) measurements. The morphological properties of the composites were studied, and the presence of the heterocoagulated structure was confirmed by scanning electron microscopy (SEM). The nanoscale structure of the LDH(sph)-Ag°-montmorillonite composite obtained was also verified by small-angle X-ray scattering (SAXS), and the rheological characteristics were studied at various pH values. The viscosity and yield value of the composite decreased by an order of magnitude upon increasing the pH from 3.0 to 5.5. The sol-gel transition of the composite suspension was reversible in the previously mentioned pH range.
Enhanced self-repairing capability of sol-gel derived SrTiO3/nano Al2O3 composite films

NASA Astrophysics Data System (ADS)

Yao, Manwen; Peng, Yong; Xiao, Ruihua; Li, Qiuxia; Yao, Xi

2016-08-01

SrTiO3/nano Al2O3 inorganic nanocomposites were prepared by using a conventional sol-gel spin coating process. For comparison, SrTiO3 films doped by equivalent amount of sol-Al2O3 have also been investigated. Aluminum deposited by using vacuum evaporation was used as the top electrode. The nanocomposites exhibited a significantly enhanced dielectric strength of 506.9 MV/m, which was increased by 97.4% as compared with the SrTiO3 films doped with sol-Al2O3. The leakage current maintained of the same order of microampere until the ultimate breakdown of the nanocomposites. The excellent electrical performances are ascribed to the anodic oxidation reaction in origin, which can repair the internal and/or surface defects of the films.
Encapsulating Cytochrome c in Silica Aerogel Nanoarchitectures without Metal Nanoparticles while Retaining Gas-phase Bioactivity.

PubMed

Harper-Leatherman, Amanda S; Pacer, Elizabeth R; Kosciuszek, Nina D

2016-03-01

Applications such as sensors, batteries, and fuel cells have been improved through the use of highly porous aerogels when functional compounds are encapsulated within the aerogels. However, few reports on encapsulating proteins within sol-gels that are processed to form aerogels exist. A procedure for encapsulating cytochrome c (cyt. c) in silica (SiO2) sol-gels that are supercritically processed to form bioaerogels with gas-phase activity for nitric oxide (NO) is presented. Cyt. c is added to a mixed silica sol under controlled protein concentration and buffer strength conditions. The sol mixture is then gelled and the liquid filling the gel pores is replaced through a series of solvent exchanges with liquid carbon dioxide. The carbon dioxide is brought to its critical point and vented off to form dry aerogels with cyt. c encapsulated inside. These bioaerogels are characterized with UV-visible spectroscopy and circular dichroism spectroscopy and can be used to detect the presence of gas-phase nitric oxide. The success of this procedure depends on regulating the cyt. c concentration and the buffer concentration and does not require other components such as metal nanoparticles. It may be possible to encapsulate other proteins using a similar approach making this procedure important for potential future bioanalytical device development.
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.
Electrical and optical properties of sol-gel derived La modified PbTiO 3 thin films

NASA Astrophysics Data System (ADS)

Chopra, Sonalee; Sharma, Seema; Goel, T. C.; Mendiratta, R. G.

2004-09-01

Lanthanum modified lead titanate (Pb 1- xLa xTi 1- x/4 O 3) PLT x ( x=0.08 i.e. PLT8) sol-gel derived thin films have been prepared on indium tin oxide (ITO) coated glass and quartz substrates using lead acetate trihydrate, lanthanum acetate hydrate and titanium isopropoxide as precursors along with 2-methoxyethanol as solvent and acetic acid as catalyst by spin coating method. The microstructure and surface morphology of the films annealed at 650 °C have been studied by X-ray diffraction technique and atomic force microscope (AFM). XRD has shown a single phase with tetragonal structure and AFM images have confirmed a smooth and crack-free surface with low surface roughness. The dependence of leakage current on applied voltage show ohmic behavior at low field region with a space charge conduction mechanism at high fields. The wavelength dispersion curve of thin films obtained from the transmission spectrum of thin films show that the films have high optical transparency in the visible region.
Structural and physical property study of sol-gel synthesized CoFe2-xHoxO4 nano ferrites

NASA Astrophysics Data System (ADS)

Patankar, K. K.; Ghone, D. M.; Mathe, V. L.; Kaushik, S. D.

2018-05-01

CoFe2-xHoxO4 (x = 0.00, 0.05, 0.10, 0.15, 0.20) ferrites were prepared by the suitably modified Sol-Gel technique. X-ray diffraction (XRD) analysis revealed that the substituted samples show phase pure formation till 10% substitution, which is far higher phase pure than the earlier reports. Upon further substitution an inevitable secondary phase of HoFeO3 along with the spinel phase despite regulating synthesis parameters in the sol-gel reaction route. These results are further corroborated more convincingly by room temperature neutron diffraction. Morphological features of the ferrites were studied by Scanning Electron Microscopy (SEM). The magnetic parameters viz. the saturation magnetization (Ms), coercivity (Hc) and remanence (Mr) were determined from room temperature isothermal magnetization. These parameters were found to decrease with increase in Ho substitution. The decrease in magnetization is analyzed in the light of exchange interactions between rare earth and transition metal ions. Magnetostriction measurements revealed interesting results and the presence of a secondary phase was found to be responsible for decreased measu-red magnetostriction values. The solubility limit of Ho in CoFe2O4 lattice is also reflected from the X-ray and neutron diffraction analysis and magnetostriction studies.
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.
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.
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.
Organo-metallic elements for associative information processing

NASA Astrophysics Data System (ADS)

Potember, Richard S.; Poehler, Theodore O.

1989-01-01

In the three years of the program we have: (1) built and tested a 4 bit element matrix device for possible use in high density content-addressable memories systems; (2) established a test and evaluation laboratory to examine optical materials for nonlinear effects, saturable absorption, harmonic generation and photochromism; (3) successfully designed, constructed and operated a codeposition processing system that enables organic materials to be deposited on a variety of substrates to produce optical grade coatings and films. This system is also compatible with other traditional microelectronic techniques; (4) used the sol-gel process with colloidal AgTCNQ to fabricate high speed photochromic switches; (5) develop and applied for patent coverage to make VO2 optical switching materials via the sol-gel processing using vanadium (IV) alkoxide compounds.
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.
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.
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.
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.
Gel Fabrication of Molybdenum “Beads”

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

Lowden, Richard Andrew; Armstrong, Beth L.; Cooley, Kevin M.

2016-11-01

Spherical molybdenum particles or “beads” of various diameters are of interest as feedstock materials for the additive manufacture of targets and assemblies used in the production of 99Mo medical isotopes using accelerator technology. Small metallic beads or ball bearings are typically fabricated from wire; however, small molybdenum spheres cannot readily be produced in this manner. Sol-gel processes are often employed to produce small dense microspheres of metal oxides across a broad diameter range that in the case of molybdenum could be reduced and sintered to produce metallic spheres. These Sol-gel type processes were examined for forming molybdenum oxide beads; however,more » the molybdenum trioxide was chemically incompatible with commonly used gelation materials. As an alternative, an aqueous alginate process being assessed for the fabrication of oxide spheres for catalyst applications was employed to form molybdenum trioxide beads that were successfully reduced and sintered to produce small molybdenum spheres.« less
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.

Synthesis of LiCoO 2 thin films by sol/gel process

NASA Astrophysics Data System (ADS)

Porthault, H.; Le Cras, F.; Franger, S.

LiCoO 2 thin films were synthesized by sol/gel process using acrylic acid (AA) as chelating agent. The gel formulation was optimized by varying solvent (ethylene glycol or water) and precursors molar ratios (Li, Co, AA) in order to obtain a dense film for positive electrode of lithium batteries. The gel was deposited by spin-coating technique on an Au/TiO 2/SiN/SiO 2/Si substrate. Thin films were deposited by either single or multistep process to enhance the density of the thin film and then calcined during 5 h at 800 °C to obtain the R-3m phase (HT-LiCoO 2). A chemical characterization of the solution was realized by Fourier Transform Infrared (FTIR) spectroscopy. Thermal decomposition of precursors and gel was studied by Thermo Gravimetric Analyses (TGA). Further investigations were done to characterize rheologic behaviour of the gel and solvents affinity with the substrate. Crystallinity and morphology were analyzed respectively by X-ray diffraction (XRD) and Scanning Electron Microscopy (SEM). The formation of R-3m phase was confirmed by the electrochemical behaviour of the gel derived LiCoO 2. Cyclic voltammograms and galvanostatic cycling show typical curve shape of the HT-LiCoO 2.
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.
The nature, fabrication, and applications of photosensitive, bulk, germano-silicate glass

NASA Astrophysics Data System (ADS)

Heaney, Alan Douglas

2000-08-01

The photosensitive nature of germano-silicate glass is widely used to create fiber-optic devices. This thesis examines the cause of photosensitivity in germano- silicate glass. The results of this research elucidate the role that germanium oxygen deficient defects play in the photosensitivity of hydrogen-loaded, germano-silicate glass. We find that defects are not vital to the photosensitivity of hydrogen-loaded, germano-silicate glass but they do enhance the effect. Quantitative measurements show that germanium oxygen deficient defects promote the formation of OH, GeH, and GeH2 when hydrogen-loaded, germano-silicate glass is exposed to ultraviolet light. A sol-gel process for fabricating germano-silicate glass in bulk samples has been developed. The sol-gel process produces high-quality, germano-silicate glass which can be tailored to contain defects or be relatively free of defects. Control over the glass defect concentration allows us to use sol-gel derived glass for comparative studies of the photosensitive process and for device applications. The unique properties of germano-silicate glass make it a likely choice for use in optical applications. To prove the feasibility of bulk devices, chirped-pulse amplification is demonstrated using gratings written in bulk germano-silicate glass.
Sol-gel route to highly transparent (Ho0.05Y0.95)2Ti2O7 thin films for active optical components operating at 2 μm

NASA Astrophysics Data System (ADS)

Vytykáčová, Soňa; Mrázek, Jan; Puchý, Viktor; Džunda, Róbert; Skála, Roman; Peterka, Pavel; Kašík, Ivan

2018-04-01

We present a generic sol-gel route to the preparation of optically active nanocrystalline holmium-yttrium titanate (Ho0.05Y0.95)2Ti2O7 thin films, which exhibit a strong luminescence at 2 μm. The films were prepared by the sol-gel process and thermally treated in a rapid thermal annealing furnace. The nanocrystal size and optical properties were tailored by the processing temperature. The final film thickness was around 500 nm. X-ray diffraction analysis and Raman spectroscopy confirmed the high purity of the crystal phase of (Ho0.05Y0.95)2Ti2O7. The activation energy of crystal growth was 35.7 kJ mol-1. The films had excellent structural and surface homogeneity causing their high transparency close to the theoretical limit of 93.39%. Refractive index of the film heat-treated at 1000 °C was around 1.98. The films exhibited strong emission at 2 μm with a luminescence lifetime around 4.6 ms. Their properties together with processing feasibility make them promising materials for photonic applications.
Sol-gel thin-film based mesoporous silica and carbon nanotubes for the determination of dopamine, uric acid and paracetamol in urine.

PubMed

Canevari, Thiago C; Raymundo-Pereira, Paulo A; Landers, Richard; Benvenutti, Edilson V; Machado, Sérgio A S

2013-11-15

This work describes the preparation, characterization and application of a hybrid material composed of disordered mesoporous silica (SiO2) modified with multiwalled carbon nanotubes (MWCNTs), obtained by the sol-gel process using HF as the catalyst. This hybrid material was characterized by N2 adsorption-desorption isotherms, X-ray powder diffraction (XRD), scanning electron microscopy (SEM), high resolution transmission microscopy (HR-TEM), Raman spectroscopy and X-ray photoelectron spectroscopy (XPS). This new hybrid material was used for the construction of a thin film on a glassy carbon electrode. The modified electrode using this material was designated SiO2/MWCNT/GCE. The electrocatalytic properties of the electrode toward dopamine, uric acid and paracetamol oxidation were studied by differential pulse voltammetry. Well-defined and separated oxidation peaks were observed in phosphate buffer solution at pH 7.0, in contrast with the ill-defined peaks observed with unmodified glassy carbon electrodes. The electrode had high sensitivity for the determination of dopamine, uric acid and paracetamol, with the limits of detection obtained using statistical methods, at 0.014, 0.068 and 0.098 µmol L(-1), respectively. The electrode presented some important advantages, including enhanced physical rigidity, surface renewability by polishing and high sensitivity, allowing the simultaneous determination of these three analytes in a human urine sample. Crown Copyright © 2013 Published by Elsevier B.V. All rights reserved.
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.
Indirect rapid prototyping of sol-gel hybrid glass scaffolds for bone regeneration - Effects of organic crosslinker valence, content and molecular weight on mechanical properties.

PubMed

Hendrikx, Stephan; Kascholke, Christian; Flath, Tobias; Schumann, Dirk; Gressenbuch, Mathias; Schulze, F Peter; Hacker, Michael C; Schulz-Siegmund, Michaela

2016-04-15

We present a series of organic/inorganic hybrid sol-gel derived glasses, made from a tetraethoxysilane-derived silica sol (100% SiO2) and oligovalent organic crosslinkers functionalized with 3-isocyanatopropyltriethoxysilane. The material was susceptible to heat sterilization. The hybrids were processed into pore-interconnected scaffolds by an indirect rapid prototyping method, described here for the first time for sol-gel glass materials. A large panel of polyethylene oxide-derived 2- to 4-armed crosslinkers of molecular weights ranging between 170 and 8000Da were incorporated and their effect on scaffold mechanical properties was investigated. By multiple linear regression, 'organic content' and the 'content of ethylene oxide units in the hybrid' were identified as the main factors that determined compressive strength and modulus, respectively. In general, 3- and 4-armed crosslinkers performed better than linear molecules. Compression tests and cell culture experiments with osteoblast-like SaOS-2 cells showed that macroporous scaffolds can be produced with compressive strengths of up to 33±2MPa and with a pore structure that allows cells to grow deep into the scaffolds and form mineral deposits. Compressive moduli between 27±7MPa and 568±98MPa were obtained depending on the hybrid composition and problems associated with the inherent brittleness of sol-gel glass materials could be overcome. SaOS-2 cells showed cytocompatibility on hybrid glass scaffolds and mineral accumulation started as early as day 7. On day 14, we also found mineral accumulation on control hybrid glass scaffolds without cells, indicating a positive effect of the hybrid glass on mineral accumulation. We produced a hybrid sol-gel glass material with significantly improved mechanical properties towards an application in bone regeneration and processed the material into macroporous scaffolds of controlled architecture by indirect rapid prototyping. We were able to produce macroporous materials of relevant porosity and pore size with compressive moduli, covering the range reported for cancellous bone while an even higher compressive strength was maintained. By multiple linear regression, we identified crosslinker parameters, namely organic content and the content of ethylene oxide units in the hybrids that predominantly determined the mechanics of the hybrid materials. The scaffolds proved to be cytocompatible and induced mineralization in SaOS-2 cells. This provides new insight on the critical parameters for the design of the organic components of covalent hybrid sol-gel glasses. Copyright © 2016 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.
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.
Flexible freestanding sandwich type ZnO/rGO/ZnO electrode for wearable supercapacitor

NASA Astrophysics Data System (ADS)

Ghorbani, Mina; Golobostanfard, Mohammad Reza; Abdizadeh, Hossein

2017-10-01

The development of flexible supercapacitors with high energy and power density as one of the main components of wearable electronics is in an enormous interest. In this report, a unique flexible electrode based on freestanding sandwich type ZnO/rGO/ZnO paper is fabricated by a simple low cost sol-gel method for utilizing in flexible supercapacitor. ZnO layers are deposited on both sides of rGO paper which is prepared by a modified Hummer's method and evaporation induced assembly. The uniform and densely packed ZnO layers are formed on graphene oxide paper and the paper is simultaneously reduced. Structural analysis reveals the formation of ZnO thin films on both sides of rGO nanosheets, which leads to the sandwich architecture. Also, the effect of ZnO sol-gel process parameters on microstructure of sandwich paper are investigated and the most suitable condition for highest supercapacity performance is the solvent of 1-PrOH, stabilizer of TeA, sol concentration of 0.2 M, deposition speed of 30 mm min-1, and 10 deposited layers. The results of electrochemical impedance spectroscopy, galvanostatic charge-discharge, and cyclic voltammetry confirm that the incorporation of ZnO improves the capacitive performance of rGO electrode. Moreover, ZnO/rGO/ZnO flexible electrode exhibits suitable capacitance value of 60.63 F g-1 at scan rate of 5 mV/s.
Synthesis of Sol-Gel Precursors for Ceramics from Lunar and Martian Soil Simulars

NASA Technical Reports Server (NTRS)

Sibille, L.; Gavira-Gallardo, J. A.; Hourlier-Bahloul, D.

2004-01-01

Recent NASA mission plans for the human exploration of our Solar System has set new priorities for research and development of technologies necessary to enable a long-term human presence on the Moon and Mars. The recovery and processing of metals and oxides from mineral sources on other planets is under study to enable use of ceramics, glasses and metals by explorer outposts. We report initial results on the production of sol-gel precursors for ceramic products using mineral resources available in martian or lunar soil. The presence of SO2, TiO2, and Al2O3 in both martian (44 wt.% SiO2, 1 wt.% TiO2, 7 wt.% Al2O3) and lunar (48 wt.% SiO2, 1.5 wt.% TiO2, 16 wt.% Al2O3) soils and the recent developments in chemical processes to solubilize silicates using organic reagents and relatively little energy indicate that such an endeavor is possible. In order to eliminate the risks involved in the use of hydrofluoric acid to dissolve silicates, two distinct chemical routes are investigated to obtain soluble silicon oxide precursors from lunar and martian soil simulars. Clear solutions of sol-gel precursors have been obtained by dissolution of silica from lunar soil similar JSC-1 in basic ethylene glycol (C2H4(OH)2) solutions to form silicon glycolates. Similarly, sol-gel solutions produced from martian soil simulars reveal higher contents of iron oxides. Characterization of the precursor molecules and efforts to further concentrate and hydrolyze the products to obtain gel materials will be presented for evaluation as ceramic precursors.
Synthesis of Sol-Gel Precursors for Ceramics from Lunar and Martian Soil Simulars

NASA Technical Reports Server (NTRS)

Sibille, L.; Gavira-Gallardo, J. A.; Hourlier-Bahloul, D.

2003-01-01

Recent NASA mission plans for the human exploration of our Solar System has set new priorities for research and development of technologies necessary to enable a long-term human presence on the Moon and Mars. The recovery and processing of metals and oxides from mineral sources on other planets is under study to enable use of ceramics, glasses and metals by explorer outposts. We report initial results on the production of sol-gel precursors for ceramic products using mineral resources available in martian or lunar soil. The presence of SiO2, TiO2, and Al2O3 in both martian (44 wt.% SiO2, 1 wt.% TiO2,7 wt.% Al2O3) and lunar (48 wt.% SiO2, 1.5 wt.% TiO2, 16 wt.% Al2O3) soils and the recent developments in chemical processes to solubilize silicates using organic reagents and relatively little energy indicate that such an endeavor is possible. In order to eliminate the risks involved in the use of hydrofluoric acid to dissolve silicates, two distinct chemical routes are investigated to obtain soluble silicon oxide precursors from lunar and martian soil simulars. Clear solutions of sol-gel precursors have been obtained by dissolution of silica from lunar soil simular in basic ethylene glycol (C2H4(OH)2) solutions to form silicon glycolates. Similarly, sol-gel solutions produced from martian soil simulars reveal higher contents of iron oxides. The elemental composition and structure of the precursor molecules were characterized. Further concentration and hydrolysis of the products was performed to obtain gel materials for evaluation as ceramic precursors.
Silica coating of nanoparticles by the sonogel process.

PubMed

Chen, Quan; Boothroyd, Chris; Tan, Gim Hong; Sutanto, Nelvi; Soutar, Andrew McIntosh; Zeng, Xian Ting

2008-02-05

A modified aqueous sol-gel route was developed using ultrasonic power for the silica coating of indium tin oxide (ITO) nanoparticles. In this approach, organosilane with an amino functional group was first used to cover the surface of as-received nanoparticles. Subsequent silica coating was initiated and sustained under power ultrasound irradiation in an aqueous mixture of surface-treated particles and epoxy silane. This process resulted in a thin but homogeneous coverage of silica on the particle surface. Particles coated with a layer of silica show better dispersability in aqueous and organic media compared with the untreated powder. Samples were characterized by high-resolution transmission electron microscopy (HRTEM), X-ray photoelectron spectroscopy (XPS), and the zeta potential.
Sol-Gel Material-Enabled Electro-Optic Polymer Modulators

PubMed Central

Himmelhuber, Roland; Norwood, Robert A.; Enami, Yasufumi; Peyghambarian, Nasser

2015-01-01

Sol-gels are an important material class, as they provide easy modification of material properties, good processability and are easy to synthesize. In general, an electro-optic (EO) modulator transforms an electrical signal into an optical signal. The incoming electrical signal is most commonly information encoded in a voltage change. This voltage change is then transformed into either a phase change or an intensity change in the light signal. The less voltage needed to drive the modulator and the lower the optical loss, the higher the link gain and, therefore, the better the performance of the modulator. In this review, we will show how sol-gels can be used to enhance the performance of electro-optic modulators by allowing for designs with low optical loss, increased poling efficiency and manipulation of the electric field used for driving the modulator. The optical loss is influenced by the propagation loss in the device, as well as the losses occurring during fiber coupling in and out of the device. In both cases, the use of sol-gel materials can be beneficial due to the wide range of available refractive indices and low optical attenuation. The influence of material properties and synthesis conditions on the device performance will be discussed. PMID:26225971
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.
Low cost sol-gel derived SiC-SiO2 nanocomposite as anti reflection layer for enhanced performance of crystalline silicon solar cells

NASA Astrophysics Data System (ADS)

Jannat, Azmira; Lee, Woojin; Akhtar, M. Shaheer; Li, Zhen Yu; Yang, O.-Bong

2016-04-01

This paper describes the preparation, characterizations and the antireflection (AR) coating application in crystalline silicon solar cells of sol-gel derived SiC-SiO2 nanocomposite. The prepared SiC-SiO2 nanocomposite was effectively applied as AR layer on p-type Si-wafer via two step processes, where the sol-gel of precursor solution was first coated on p-type Si-wafer using spin coating at 2000 rpm and then subjected to annealing at 450 °C for 1 h. The crystalline, and structural observations revealed the existence of SiC and SiO2 phases, which noticeably confirmed the formation of SiC-SiO2 nanocomposite. The SiC-SiO2 layer on Si solar cells was found to be an excellent AR coating, exhibiting the low reflectance of 7.08% at wavelengths ranging from 400 to 1000 nm. The fabricated crystalline Si solar cell with SiC-SiO2 nanocomposite AR coating showed comparable power conversion efficiency of 16.99% to the conventional SixNx AR coated Si solar cell. New and effective sol-gel derived SiC-SiO2 AR layer would offer a promising technique to produce high performance Si solar cells with low-cost.
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.
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.
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.
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.
Synthesis of a colloid solution of silica-coated gold nanoparticles for X-ray imaging applications

NASA Astrophysics Data System (ADS)

Kobayashi, Yoshio; Nagasu, Ryoko; Shibuya, Kyosuke; Nakagawa, Tomohiko; Kubota, Yohsuke; Gonda, Kohsuke; Ohuchi, Noriaki

2014-08-01

This work proposes a method for fabricating silica-coated gold (Au) nanoparticles, surface modified with poly(ethylene glycol) (PEG) (Au/SiO2/PEG), with a particle size of 54.8 nm. X-ray imaging of a mouse is performed with the colloid solution. A colloid solution of 17.9 nm Au nanoparticles was prepared by reducing Au ions (III) with sodium citrate in water at 80 °C. The method used for silica-coating the Au nanoparticles was composed of surface-modification of the Au nanoparticles with (3-aminopropyl)-trimethoxysilane (APMS) and a sol-gel process. The sol-gel process was performed in the presence of the surface-modified Au nanoparticles using tetraethylorthosilicate, APMS, water, and sodium hydroxide, in which the formation of silica shells and the introduction of amino groups to the silica-coated particles took place simultaneously (Au/SiO2-NH2). Surface modification of the Au/SiO2-NH2 particles with PEG, or PEGylation of the particle surface, was performed by adding PEG with a functional group that reacted with an amino group in the Au/SiO2-NH2 particle colloid solution. A computed tomography (CT) value of the aqueous colloid solution of Au/SiO2/PEG particles with an actual Au concentration of 0.112 M was as high as 922 ± 12 Hounsfield units, which was higher than that of a commercial X-ray contrast agent with the same iodine concentration. Injecting the aqueous colloid solution of Au/SiO2/PEG particles into a mouse increased the light contrast of tissues. A CT value of the heart rose immediately after the injection, and this rise was confirmed for up to 6 h.

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
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.
Phase equilibrium and preparation, crystallization and viscous sintering of glass in the alumina-silica-lanthanum phosphate system

NASA Astrophysics Data System (ADS)

He, Feng

The phase equilibrium, viscosity of melt-quenched glasses, and processing of sol-gel glasses of the alumina-silica-lanthanum phosphate system were studied. These investigations were directed towards serving the objective of synthesizing nano-structured ceramic-matrix-composites via controlled crystallization of glass precursors. The thermal stability, phase equilibrium, and liquidus temperatures of the alumina- and mullite-lanthanum phosphate systems are determined. An iridium wire heater was constructed to anneal samples up to 2200°C. Phosphorus evaporation losses were significant at high temperatures, especially over 1800°C. The tentative phase diagrams of the two quasi-binary systems were presented. The viscosity of the melt-quenched mullite-lanthanum phosphate glasses was measured by three different methods, including viscous sintering of glass powder compacts, neck formation between two Frenkel glass beads, and thermal analysis of the glass transition. Improved methodologies were developed for applying the interpretative mathematical models to the results of the sintered powder and thermal analytical experiments. Good agreement was found between all three methods for both absolute values and temperature dependence. A sol-gel process was developed as a low temperature route to producing glasses. A unique, single phase mullite gel capable of low temperature (575°C) mullitization was made from tetraethoxysilane and aluminum isopropoxide at room temperature in three days. Low temperature crystallization was attributed to the avoidance of phase segregation during gel formation and annealing. This was greatly enhanced by a combination of low temperature preheating in the amorphous state, a high heating rate during crystallization and low water content. The Al2O3 content in mullite (61-68 mol%) depended on the highest annealing temperature. Two mullite-lanthanum phosphate gels were made based upon modifying the chemical procedures used for the homogeneous single phase and heterogeneous diphasic mullite gels from same starting chemicals. Amorphous powders were obtained after optimized calcinations. Their different crystallization routes and sintering behavior were investigated and correlated with the different homogeneities of precursor gels. Structurally stable open, porous ceramics (up to 80% porosity) were produced from the single-phase gel derived powder, where gases exsolved during calcination caused foaming coincident with sintering. Translucent, dense glass ceramic was made from the calcined diphasic gel by hot-pressing.
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.
Magnetic studies of cobalt doped barium hexaferrite nanoparticles prepared by modified sol-gel method

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

Shalini, M. Govindaraj; Sahoo, Subasa C., E-mail: subasa@cukerala.ac.in

2016-05-06

M-type barium hexaferrite (BaFe{sub 12}O{sub 19}) and cobalt doped barium hexaferrite (BaFe{sub 11}CoO{sub 19}) nanopowders were synthesized by modified sol-gel auto-combustion technique and were annealed at 900°C in air for 4 hours. The annealed powders were studied in the present work and X-ray diffraction studies showed pure phase formation after annealing. The average grain size in the nanopowder sample was decreased after doping. Magnetization value of 60 emu/g was observed at 300 K for the barium hexaferrite and was reduced to 54 emu/g after doping. The coercivity of 5586 Oe was observed at 300 K for the undoped sample andmore » was found to be decreased in the doped sample. As the measurement temperature was decreased from 300 K to 60 K, magnetization value was increased in both the samples compared to those at 300 K. The coercivity of the undoped sample was found to decrease whereas it was increased for the doped sample at 60 K. The observed magnetic properties may be understood on the basis of modified exchange interaction and anisotropy in the doped sample compared to that of pure barium hexaferrite.« less
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.
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.
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.
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%.
Structural properties and gas sensing behavior of sol-gel grown nanostructured zinc oxide

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

Rajyaguru, Bhargav; Gadani, Keval; Kansara, S. B.

2016-05-06

In this communication, we report the results of the studies on structural properties and gas sensing behavior of nanostructured ZnO grown using acetone precursor based modified sol-gel technique. Final product of ZnO was sintered at different temperatures to vary the crystallite size while their structural properties have been studied using X-ray diffraction (XRD) measurement performed at room temperature. XRD results suggest the single phasic nature of all the samples and crystallite size increases from 11.53 to 20.96 nm with increase in sintering temperature. Gas sensing behavior has been studied for acetone gas which indicates that lower sintered samples are moremore » capable to sense the acetone gas and related mechanism has been discussed in the light of crystallite size, crystal boundary density, defect mechanism and possible chemical reaction between gas traces and various oxygen species.« less
Octadecylsilane hybrid silicas prepared by the sol-gel method: morphological and textural aspects.

PubMed

Brambilla, Rodrigo; Pires, Gilvan P; dos Santos, João H Z; Lacerda Miranda, Márcia S

2007-08-15

A series of octadecylsilane-modified silicas was prepared by the sol-gel method through the hydrolysis and cocondensation of tetraethylorthosilicate (TEOS) with octadecyltriethoxysilane (ODS). The ODS:TEOS ratio was varied between 0:100 and 100:0. The resulting carbon content was between 2.5 and 53.4%. In the case of pure ODS, the resulting silica presented 68.6% of C. Hybrid silicas were characterized by scanning electron microscopy, energy dispersive X-ray spectroscopy, and (29)Si nuclear magnetic resonance spectroscopy. Spheres of ca. 0.5-1.0 microm were obtained in the case of hydrolysis of pure TEOS. The combination of ODS:TEOS ratio yielded systems combining spherical and lamellar patterns zones. Monitoring the particle growth, it seems that spherical particles grow around lamellar zones, these latter concentrating the organosilicon moieties. The degree of cross-linking of ODS moieties was shown to be dependent on the ODS addition time and stirring speed.
Preparation of ZrO II/nano-TiO II composite powder by sol-gel method

NASA Astrophysics Data System (ADS)

Baharvandi, H. R.; Mohammadi, E.; Abdizadeh, H.; Hadian, A. M.; Ehsani, N.

2007-07-01

The effects of concentration of TTIP, amount of distilled water, and calcination temperature on morphology and particle size distribution of ZrO II/nano-TiO II catalysts were investigated. Mixed ZrO II/nano-TiO II powders were prepared by a modified sol-gel method by varying the mole fraction of TTIP from 0.002 to 0.01, H IIO/TTIP fraction from 2 to 8, and various stirring time (2, 4, and 10 h). The prepared ZrO II/nano-TiO II powders have been characterized by scanning electron microscopy (SEM), X-ray diffraction (XRD), and TG/DTA. Each oxide was calcined at the temperature between 110 and 1000°C. The results showed that the calcinations temperature has a pronounced effect on the phase formation and particle size of the calcined zirconium titanate (ZT) powders.
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.
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.
Additive Manufacturing of Transparent Silica Glass from Solutions.

PubMed

Cooperstein, Ido; Shukrun, Efrat; Press, Ofir; Kamyshny, Alexander; Magdassi, Shlomo

2018-06-06

A sol, aqueous solution-based ink is presented for fabrication of 3D transparent silica glass objects with complex geometries, by a simple 3D printing process conducted at room temperature. The ink combines a hybrid ceramic precursor that can undergo both the photopolymerization reaction and a sol-gel process, both in the solution form, without any particles. The printing is conducted by localized photopolymerization with the use of a low-cost 3D printer. Following printing, upon aging and densifying, the resulting objects convert from a gel to a xerogel and then to a fused silica. The printed objects, which are composed of fused silica, are transparent and have tunable density and refractive indices.
Sol-gel derived ZnO as an electron transport layer (ETL) for inverted organic solar cells

NASA Astrophysics Data System (ADS)

Tiwari, D. C.; Dwivedi, Shailendra Kumar; Dipak, Phukhrambam; Chandel, Tarun; Sharma, Rishi

2017-05-01

In this work, we present the study of the fabrication process of the sol-gel derived zinc oxide (ZnO) as an electron transport layer (ETL.). The solution processed inverted bulk heterojunction organic solar cells based on a thin film blend of poly (3-hexylthiophene 2, 5-diyl) and [6,6]-phenyl-C61-butyric acid methyl ester is prepared. ZnO thin films are annealed at different temperature to optimize the solar cell performance and their characterization for their structural and optical properties are carried out. We have observed Voc=70mV, Jsc=1.33 µA/cm2 and FF=26% from the inverted heterojunction solar cell.
Sol-gel antireflective spin-coating process for large-size shielding windows

NASA Astrophysics Data System (ADS)

Belleville, Philippe F.; Prene, Philippe; Mennechez, Francoise; Bouigeon, Christian

2002-10-01

The interest of the antireflective coatings applied onto large-area glass components increases everyday for the potential application such as building or shop windows. Today, because of the use of large size components, sol-gel process is a competitive way for antireflective coating mass production. The dip-coating technique commonly used for liquid-deposition, implies a safety hazard due to coating solution handling and storage in the case of large amounts of highly flammable solvent use. On the other hand, spin-coating is a liquid low-consumption technique. Mainly devoted to coat circular small-size substrate, we have developed a spin-coating machine able to coat large-size rectangular windows (up to 1 x 1.7 m2). Both solutions and coating conditions have been optimized to deposit optical layers with accurate and uniform thickness and to highly limit the edge effects. Experimental single layer antireflective coating deposition process onto large-area shielding windows (1000 x 1700 x 20 mm3) is described. Results show that the as-developed process could produce low specular reflection value (down to 1% one side) onto white-glass windows over the visible range (460-750 nm). Low-temperature curing process (120°C) used after sol-gel deposition enables antireflective-coating to withstand abrasion-resistance properties in compliance to US-MIL-C-0675C moderate test.
Critical behavior of modulus of gel

NASA Astrophysics Data System (ADS)

Tokita, Masayuki; Niki, Ryoya; Hikichi, Kunio

1985-09-01

The critical behavior of the shear modulus of casein gel is studied. The shear modulus of casein gel scales with the conductivity exponent in the immediate vicinity of the sol-gel transition point. The asymptotic behavior of the modulus in the region far above the transition point is governed by a different exponent which is much larger than the conductivity exponent. These results are explainable by the crossover behavior of the percolation process. This study shows that the gelation of the casein micelle solution is a realization of the percolation process.
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

Sol-gel immobilization as a suitable technique for enhancement of α-amylase activity of Aspergillus oryzae PP.

PubMed

Evstatieva, Yana; Yordanova, Mariya; Chernev, Georgi; Ruseva, Yanislava; Nikolova, Dilyana

2014-07-04

Bioencapsulation of microbial cells in silica-based matrices has proved to be a good strategy to enhance the biosynthetic capabilities and viability of bioproducers. In the present study, mycelium and pellet cultures of strain Aspergillus oryzae PP were successfully immobilized in sol-gel hybrid matrices composed of tetraethylorthosilicate as an inorganic precursor, 5% (w/v) starch and 10 or 15% (w/v) polyethylene oxide, or 10% (w/v) calcium alginate as organic compounds. Biosynthetic activity of immobilized cultures was investigated by batch and fed-batch cultivation and the obtained results of 3042.04 IU cm -3 were comparable with the enzyme activity of the free cell culture. Immobilized cultures retained their viability and biosynthetic capabilities up to the 744th h during fed-batch fermentation processes. Consequently, sol-gel encapsulation in hybrid matrices could be considered as a promising technique for immobilization of Aspergillus oryzae PP in order to increase the α-amylase production.
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
Fabrication of hydrophobic compressed oil palm trunk surface by sol-gel process

NASA Astrophysics Data System (ADS)

Muzakir, Syafiqah; Salim, Nurjannah; Huda Abu Bakar, Nurul; Roslan, Rasidi; Sin, Lim Wan; Hashim, Rokiah

2018-04-01

Improvement of the robustness of hydrophobic surfaces is crucial to achieving commercial applications of these surfaces in such various areas as self-cleaning, water repellency and corrosion resistance. Compressed oil palm trunk (OPT) panel is one of potential product which can be used as panelling and indoor furniture application. By adding hydrophobic properties to compressed oil palm trunk panel might increase the application of compressed oil palm trunk especially for outdoor application. In this study, fabrication is using the sol-gel technique. Sol-gel was prepared by adding ethanol with Hexadecyl Trimethyl Ammonium Bromide (CTAB) solution with Tetraethyl Orthosilicate (TEOS) with surface modification of chlorotrimethylsilane (CTMS). The surface with hydrophobic coating was undergone surface analysis with contact angle machine with the aid of software SCA 20 and the determined of the morphology of surface with scanning electron microscope (SEM). The produced compressed oil palm trunk surfaces exhibited promising hydrophobic properties with a contact angle of 104° and the relatively better mechanical robustness.
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
Encapsulation of Polymer Colloids in a Sol-Gel Matrix. Direct-Writing of Coassembling Organic-Inorganic Hybrid Photonic Crystals.

PubMed

Mikosch, Annabel; Kuehne, Alexander J C

2016-03-22

The spontaneous self-assembly of polymer colloids into ordered arrangements provides a facile strategy for the creation of photonic crystals. However, these structures often suffer from defects and insufficient cohesion, which result in flaking and delamination from the substrate. A coassembly process has been developed for convective assembly, resulting in large-area encapsulated colloidal crystals. However, to generate patterns or discrete deposits in designated places, convective assembly is not suitable. Here we experimentally develop conditions for direct-writing of coassembling monodisperse dye-doped polystyrene particles with a sol-gel precursor to form solid encapsulated photonic crystals. In a simple procedure the colloids are formulated in a sol-gel precursor solution, drop-cast on a flat substrate, and dried. We here establish the optimal parameters to form reproducible highly ordered photonic crystals with good optical performance. The obtained photonic crystals interact with light in the visible spectrum with a narrow optical stop-gap.
[Study on surface modification and biocompatibility of NiTi alloy intravascular stents].

PubMed

Shen, Yang; Wang, Gui-xue; Quan, Xue-jun; Yu, Qing-song

2006-01-01

This paper introduces the surface modification of NiTi alloy intravascular stents for roughness by chemical erosion and plasma deposition technology. The stent which had been granulated with chemical erosion was treated with TiO2 film prepared with Gel-sol. The study on the biocompatibility of the modified stent by the above two ways shows that the modified stent is rougher, and its anticoagulation and hydrophilicity are improved. However, the capability of erosion resistance is not enhanced significantly.
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.
A novel nano-Ni/SiO2 catalyst for hydrogen production from steam reforming of ethanol.

PubMed

Wu, Chunfei; Williams, Paul T

2010-08-01

Catalytic steam reforming of ethanol has been regarded as a promising way to produce hydrogen. However, catalytic deactivation is a key problem in the process. In this paper, a novel nano-Ni/SiO2 catalyst was prepared by a simple sol-gel method and compared to catalysts prepared by an impregnation method in relation to the steam reforming ethanol process. Good Ni dispersion and high BET surface areas (>700 m2 g(-1)) were obtained for sol-gel catalysts, whereas only 1 m2 g(-1) surface area was obtained for the Ni/SiO2 impregnation catalyst. The results of catalytic steam reforming of ethanol showed that about twice of the hydrogen production was produced with the Ni/SiO2 catalyst prepared by sol-gel (around 0.2 g h(-1)) compared with that prepared by impregnation (around 0.1 g h(-1)). The analysis of the used catalysts showed that 10Ni/SiO2-B and 20Ni/SiO2-B presented the highest stability, while other catalysts were fragmented into small pieces after the reforming process, especially the catalysts prepared by impregnation. A novel catalyst has been produced that has been shown to be effective in the production of hydrogen from the steam reforming of ethanol.
Oxidation of gas phase trichloroethylene and toluene using composite sol-gel TiO2 photocatalytic coatings.

PubMed

Keshmiri, Mehrdad; Troczynski, Tom; Mohseni, Madjid

2006-02-06

The previously developed composite sol-gel (CSG) process is proposed for the deposition of thick (10-50 microm) porous films of photocatalytic TiO2. The CSG titania was developed by binding pre-calcined TiO2 particles with TiO2 sol. It had relatively high surface area (15-35 m2/g) and good resistance against mechanical stress and abrasion. Photocatalytic activity tests were carried out on trichloroethylene (TCE) and toluene, and compared with those of standard Degussa P-25 titania. The CSG photocatalyst provided good photo-efficiency in removing both pollutants from contaminated air streams. When compared with P-25 titania, the CSG photocatalyst showed a similar photo-efficiency with first-order kinetic rate constants not significantly different from that of P-25. For both photocatalysts the rate of photocatalytic oxidation of TCE was significantly greater than that obtained for toluene. Overall, the combination of better mechanical integrity, resistance against abrasion, and comparable photocatalytic efficiency of the CSG titania versus that of P-25 titania, make the composite sol-gel (CSG) photocatalyst a viable alternative for industrial applications where long term stability, superior mechanical properties, and good photo-efficiency are of critical value.
Sol-Gel-Synthesis of Nanoscopic Complex Metal Fluorides

PubMed Central

Rehmer, Alexander; Scheurell, Kerstin; Scholz, Gudrun; Kemnitz, Erhard

2017-01-01

The fluorolytic sol-gel synthesis for binary metal fluorides (AlF3, CaF2, MgF2) has been extended to ternary and quaternary alkaline earth metal fluorides (CaAlF5, Ca2AlF7, LiMgAlF6). The formation and crystallization of nanoscopic ternary CaAlF5 and Ca2AlF7 sols in ethanol were studied by 19F liquid and solid state NMR (nuclear magnetic resonance) spectroscopy, as well as transmission electron microscopy (TEM). The crystalline phases of the annealed CaAlF5, Ca2AlF7, and LiMgAlF6 xerogels between 500 and 700 °C could be determined by X-ray powder diffraction (XRD) and 19F solid state NMR spectroscopy. The thermal behavior of un-annealed nanoscopic ternary and quaternary metal fluoride xerogels was ascertained by thermal analysis (TG/DTA). The obtained crystalline phases of CaAlF5 and Ca2AlF7 derived from non-aqueous sol-gel process were compared to crystalline phases from the literature. The corresponding nanoscopic complex metal fluoride could provide a new approach in ceramic and luminescence applications. PMID:29099086
Influence of Chemical Conditions on the Nanoporous Structure of Silicate Aerogels

PubMed Central

Sinkó, Katalin

2010-01-01

Silica or various silicate aerogels can be characterized by highly porous, open cell, low density structures. The synthesis parameters influence the three-dimensional porous structures by modifying the kinetics and mechanism of hydrolysis and condensation processes. Numerous investigations have shown that the structure of porous materials can be tailored by variations in synthesis conditions (e.g., the type of precursors, catalyst, and surfactants; the ratio of water/precursor; the concentrations; the medium pH; and the solvent). The objectives of this review are to summarize and elucidate the effects of chemical conditions on the nanoporous structure of sol-gel derived silicate aerogels.
Template-free magnesium oxide hollow sphere inclusion in organic-inorganic hybrid films via sol-gel reaction.

PubMed

Kang, Eun-Seok; Takahashi, Masahide; Tokuda, Yomei; Yoko, Toshinobu

2006-06-06

Magnesium oxide hollow spheres without a template core were conveniently prepared by stabilized bubble formation in a hybrid solution containing a magnesium acetate precursor, thus avoiding the complicated preparation process using a template. The hollow sphere could be aligned along the radial striation by spin coating, and its diameter from a micrometer to submicrometer dimension could be easily modified by the solution composition. It was also possible to control the open or closed hollow sphere by changing the solvent. Thus, the produced magnesium oxide hollow sphere is envisioned to have applications in many areas such as medicine, analysis, optics, and so on.
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 solâgel deposition or by plasma-enhanced chemical vapor deposition. This paper describes in situ solâgel deposition of hybrid inorganic/organic thin films on wood substrates using...
Preparation of mesoporous silica microparticles by sol-gel/emulsion route for protein release.

PubMed

Vlasenkova, Mariya I; Dolinina, Ekaterina S; Parfenyuk, Elena V

2018-04-06

Encapsulation of therapeutic proteins into particles from appropriate material can improve both stability and delivery of the drugs, and the obtained particles can serve as a platform for development of their new oral formulations. The main goal of this work was development of sol-gel/emulsion method for preparation of silica microcapsules capable of controlled release of encapsulated protein without loss of its native structure. For this purpose, the reported in literature direct sol-gel/W/O/W emulsion method of protein encapsulation was used with some modifications, because the original method did not allow to prepare silica microcapsules capable for protein release. The particles were synthesized using sodium silicate and tetraethoxysilane as silica precursors and different compositions of oil phase. In vitro kinetics of bovine serum albumin (BSA) release in buffer (pH 7.4) was studied by Fourier transform infrared (FTIR) and fluorescence spectrometry, respectively. Structural state of encapsulated BSA and after release was evaluated. It was found that the synthesis conditions influenced substantially the porous structure of the unloaded silica particles, release properties of the BSA-loaded silica particles and structural state of the encapsulated and released protein. The modified synthesis conditions made it possible to obtain the silica particles capable of controlled release of the protein during a week without loss of the protein native structure.
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
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.
Sol-gel deposited Cu2O and CuO thin films for photocatalytic water splitting.

PubMed

Lim, Yee-Fun; Chua, Chin Sheng; Lee, Coryl Jing Jun; Chi, Dongzhi

2014-12-21

Cu2O and CuO are attractive photocatalytic materials for water splitting due to their earth abundance and low cost. In this paper, we report the deposition of Cu2O and CuO thin films by a sol-gel spin-coating process. Sol-gel deposition has distinctive advantages such as low-cost solution processing and uniform film formation over large areas with a precise stoichiometry and thickness control. Pure-phase Cu2O and CuO films were obtained by thermal annealing at 500 °C in nitrogen and ambient air, respectively. The films were successfully incorporated as photocathodes in a photoelectrochemical (PEC) cell, achieving photocurrents of -0.28 mA cm(-2) and -0.35 mA cm(-2) (for Cu2O and CuO, respectively) at 0.05 V vs. a reversible hydrogen electrode (RHE). The Cu2O photocurrent was enhanced to -0.47 mA cm(-2) upon incorporation of a thin layer of a NiOx co-catalyst. Preliminary stability studies indicate that CuO may be more stable than Cu2O as a photocathode for PEC water-splitting.
Solid-phase microextraction Ni-Ti fibers coated with functionalised silica particles immobilized in a sol-gel matrix.

PubMed

Azenha, Manuel; Ornelas, Mariana; Fernando Silva, A

2009-03-20

One of the possible approaches for the development of novel solid-phase microextraction (SPME) fibers is the physical deposition of porous materials onto a support using high-temperature epoxy glue. However, a major drawback arises from decomposition of epoxy glue at temperatures below 300 degrees C and instability in some organic solvents. This limitation motivated us to explore the possibility of replacing the epoxy glue with a sol-gel film, thermally more stable and resistant to organic solvents. We found that functionalised silica particles could be successfully attached to a robust Ni-Ti wire by using a UV-curable sol-gel film. The particles were found to be more important than the sol-gel layer during the microextraction process, as shown by competitive extraction trials and by the different extraction profiles observed with differently functionalised particles. If a quality control microscopic-check aiming at the rejection of fibers exhibiting unacceptably low particle load was conducted, acceptable (6-14%) reproducibility of preparation of C(18)-silica fibers was observed, and a strong indication of the durability of the fibers was also obtained. A cyclohexyldiol-silica fiber was used, as a simple example of applicability, for the successful determination of benzaldehyde, acetophenone and dimethylphenol at trace level in spiked tap water. Recoveries: 95-109%; limits of detection: 2-7 microg/L; no competition effects within the studied range (
Fabrication of highly conductive graphene/ITO transparent bi-film through CVD and organic additives-free sol-gel techniques.

PubMed

Hemasiri, Bastian Waduge Naveen Harindu; Kim, Jae-Kwan; Lee, Ji-Myon

2017-12-19

Indium tin oxide (ITO) still remains as the main candidate for high-performance optoelectronic devices, but there is a vital requirement in the development of sol-gel based synthesizing techniques with regards to green environment and higher conductivity. Graphene/ITO transparent bi-film was synthesized by a two-step process: 10 wt. % tin-doped ITO thin films were produced by an environmentally friendly aqueous sol-gel spin coating technique with economical salts of In(NO 3 ) 3 .H 2 O and SnCl 4 , without using organic additives, on surface free energy enhanced (from 53.826 to 97.698 mJm -2 ) glass substrate by oxygen plasma treatment, which facilitated void-free continuous ITO film due to high surface wetting. The chemical vapor deposited monolayer graphene was transferred onto the synthesized ITO to enhance its electrical properties and it was capable of reducing sheet resistance over 12% while preserving the bi-film surface smoother. The ITO films contain the In 2 O 3 phase only and exhibit the polycrystalline nature of cubic structure with 14.35 ± 0.5 nm crystallite size. The graphene/ITO bi-film exhibits reproducible optical transparency with 88.66% transmittance at 550 nm wavelength, and electrical conductivity with sheet resistance of 117 Ω/sq which is much lower than that of individual sol-gel derived ITO film.

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
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.
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.
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
Progress of studies on preparation of TiO2 photocatalysts with sol-gel auto igniting synthesis

NASA Astrophysics Data System (ADS)

Wu, Di; Shi, Zaifeng; Zhang, Xiaopeng; Xinghui, Wu

2017-11-01

In this article, influencing factors on the kinetics of the process of Sol-gel Auto igniting Synthesis (SAS) which is an advanced technology for preparing nanometer particles of inorganic materials were reviewed. The studies on preparing of nanometer TiO2 photocatalysts with SAS were focused. It was concluded that SAS will play an important role in practical preparing of high-pure nanometer TiO2 powder, and as a technical support, preparation of titania TiO2 from titanic iron ore with SAS is feasible and practicable.
Au NPs immersed in sol-gel matrix: nonlinear optical characterization

NASA Astrophysics Data System (ADS)

Aguilera-Zavala, Angélica; Trejo-Durán, Mónica; Ortiz-Jiménez, Orlando; Cornejo-Monroy, Delfino; Severiano-Carrillo, Israel; Alvarado-Méndez, Edgar

2016-09-01

Physical and optical characterization of thin films doped with Au Nanoparticles onto a silica substrate is presented. Films were prepared through sol-gel process, by using Au nanoparticles immersed in lipoic acid as dopant by means of hydrolysis and acid catalyzed reaction of tetraethyl-orthosilicate. The surface was characterized by SEM and AFM microscopies. Z-scan technique was used to measure nonlinear optical properties as nonlinear absorption and refraction indexes, using two different wavelengths. At 633 nm it was possible to observe nonlinear absorption only but at 514 nm both nonlinear properties were observed.
Nano-scale optical circuits and self-organized lightwave network (SOLNET) fabricated using sol-gel materials with photo-induced refractive index increase

NASA Astrophysics Data System (ADS)

Ono, Shigeru; Yoshimura, Tetsuzo; Sato, Tetsuo; Oshima, Juro

2009-02-01

Recently, Nissan Chemical Industries, LTD, developed the photo-induced refractive index variation sol-gel materials, in which the refractive index increases from 1.65 to 1.85 by ultra-violet (UV) light exposure and baking. The materials enable us to fabricate high-index-contract waveguides without developing/etching processes and strong-lightconfinement self-organized lightwave network (SOLNET). Therefore, the materials are expected promising for nanoscale optical circuits with self-alignment capability. Nano-scale optical circuits with core thickness of ~230 nm and core width of ~1 μm were fabricated. Propagation loss was 1.86 dB/cm for TE mode and 1.89 dB/cm for TM mode at 633 nm in wavelength, indicating that there were small polarization dependences. Spot sizes of guided beams along core width direction and along core thickness direction were respectively 0.6 μm and 0.3 μm for both TE and TM mode. Bending loss of S-bending waveguides was reduced from 0.44 dB to 0.24 dB for TE mode with increasing the bending curvature radius from 5 μm to 60 μm. Difference in bending loss between TM and TE mode was less than 10%. Branching loss of Y-branching waveguides was reduced from 1.33 dB to 0.08 dB for TE mode, and from 1.34 dB to 0.12 dB for TM mode with decreasing the branching angle from 80° to 20°. These results indicate that the photoinduced refractive index variation sol-gel materials can realize miniaturized optical circuits with sizes of several tens μm and guided beam confinement within a cross-section area less than 1.0 μm2 with small polarization dependences, suggesting potential applications to intra-chip optical interconnects. In addtion, we fabricated self-organized lightwave network (SOLNET) using the photo-induced refractive index variation sol-gel materials. When write beams of 405 nm in wavelength were introduced into the sol-gel thin film under baking at 200°C, self-focusing was induced, and SOLNET was formed. SOLNET fabricated by low write beam intensity exhibited strong light confinement. Furthermore, SOLNET was found to be drawn automatically to reflective portion such as a defect and a silver paste droplet in the sol-gel thin film during SOLNET formation, indicating that reflective SOLNET is formed. The results suggest that the photo-induced refractive index variation sol-gel materials can provide self-alignment capability to the nano-scale optical circuits.
Silver nanowires network encapsulated by low temperature sol-gel ZnO for transparent flexible electrodes with ambient stability

NASA Astrophysics Data System (ADS)

Shin, Wonjung; Cho, Wonki; Baik, Seung Jae

2018-01-01

As a geometrically engineered realization of transparent electrode, Ag nanowires network is promising for its superior characteristics both on electrical conductivity and optical transmittance. However, for a potential commercialization of Ag nanowires network, further investigations on encapsulation materials are necessary to prevent degradation caused by ambient aging. In addition, the temperature range of the coating process for the encapsulation material needs to be low enough to prevent degradation of polymer substrates during the film coating processes, when considering emerging flexible device application of transparent electrodes. We present experimental results showing that low temperature sol-gel ZnO processed under 130 °C is an effective encapsulation material preventing ambient oxidation of Ag nanowires network without degrading electrical, optical, and mechanical properties.
Synthesis of ultrafine ZrB2 powders by sol-gel process

NASA Astrophysics Data System (ADS)

Yang, Li-Juan; Zhu, Shi-Zhen; Xu, Qiang; Yan, Zhen-Yu; Liu, Ling

2010-09-01

Ultrafine zirconium diboride (ZrB2) powders have been synthesized by sol-gel process using zirconium oxychloride (ZrOCl2·8H2O), boric acid (H3BO3) and phenolic resin as sources of zirconia, boron oxide and carbon, respectively. The effects of the reaction temperature, B/Zr ratio, holding time, and EtOH/H2O ratio on properties of the synthesized ZrB2 powders were investigated. It was revealed that ultrafine (average crystallite size between 100 and 400 nm) ZrB2 powders can be synthesized with the optimum processing parameters as follows: (i) the ratio of B/Zr is 4; (ii) the solvent is pure ethanol; (iii) the condition of carbothermal reduction heat treatment is at 1550°C for 20 min.
Influence of Operating Parameters on Surface Properties of RF Glow Discharge Oxygen Plasma Treated TiO2/PET Film for Biomedical Application

EPA Science Inventory

Thin transparent titania (TiO2) films were coated on the surface of flexible poly (ethylene terephthalate) (PET) surface using standard sol gel techniques. The TiO2/PET thin film surfaces were further modified by exposing the films to a RF glow discharge oxygen plasma. The exposu...
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.
Electrochemical determination of L-phenylalanine at polyaniline modified carbon electrode based on β-cyclodextrin incorporated carbon nanotube composite material and imprinted sol-gel film.

PubMed

Hu, Yu-fang; Zhang, Zhao-hui; Zhang, Hua-bin; Luo, Li-juan; Yao, Shou-zhuo

2011-04-15

A sensitive and selective electrochemical sensor based on a polyaniline modified carbon electrode for the determination of L-phenylalanine has been proposed by utilizing β-cyclodextrin (β-CD) incorporated multi-walled carbon nanotube (MWNT) and imprinted sol-gel film. The electrochemical behavior of the sensor towards L-phenylalanine was investigated by cyclic voltammetry (CV), differential pulse voltammetry (DPV), and amperometric i-t curve. The surface morphologies of layer-by-layer assembly electrodes were displayed by scanning electron microscope (SEM). The response mechanism of the imprinted sensor for L-phenylalanine was based on the inclusion interaction of β-CD and molecular recognition capacity of the imprinted film for L-phenylalanine. A linear calibration plot was obtained covering the concentration range from 5.0 × 10(-7) to 1.0 × 10(-4) mol L(-1) with a detection limit of 1.0 × 10(-9) mol L(-1). With excellent sensitivity, selectivity, stability, reproducibility and recovery, the electrochemical imprinted sensor was used to detect L-phenylalanine in blood plasma samples successfully. Copyright © 2011 Elsevier B.V. All rights reserved.
High-Quality Solution-Processed Silicon Oxide Gate Dielectric Applied on Indium Oxide Based Thin-Film Transistors.

PubMed

Jaehnike, Felix; Pham, Duy Vu; Anselmann, Ralf; Bock, Claudia; Kunze, Ulrich

2015-07-01

A silicon oxide gate dielectric was synthesized by a facile sol-gel reaction and applied to solution-processed indium oxide based thin-film transistors (TFTs). The SiOx sol-gel was spin-coated on highly doped silicon substrates and converted to a dense dielectric film with a smooth surface at a maximum processing temperature of T = 350 °C. The synthesis was systematically improved, so that the solution-processed silicon oxide finally achieved comparable break downfield strength (7 MV/cm) and leakage current densities (<10 nA/cm(2) at 1 MV/cm) to thermally grown silicon dioxide (SiO2). The good quality of the dielectric layer was successfully proven in bottom-gate, bottom-contact metal oxide TFTs and compared to reference TFTs with thermally grown SiO2. Both transistor types have field-effect mobility values as high as 28 cm(2)/(Vs) with an on/off current ratio of 10(8), subthreshold swings of 0.30 and 0.37 V/dec, respectively, and a threshold voltage close to zero. The good device performance could be attributed to the smooth dielectric/semiconductor interface and low interface trap density. Thus, the sol-gel-derived SiO2 is a promising candidate for a high-quality dielectric layer on many substrates and high-performance large-area applications.
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.
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.
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.
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.
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.
Injectable magnetic supramolecular hydrogel with magnetocaloric liquid-conformal property prevents the post-operative recurrence in a breast cancer model.

PubMed

Wu, Haoan; Song, Lina; Chen, Ling; Zhang, Wei; Chen, Yi; Zang, Fengchao; Chen, Hong; Ma, Ming; Gu, Ning; Zhang, Yu

2018-05-03

Locoregional recurrence of breast cancer after tumor resection represents several clinical challenges. Here, we demonstrate that co-delivery of chemotherapy and thermotherapeutic agents by a magnetic supramolecular hydrogel (MSH) following tumor resection prevents tumor recurrence in a breast cancer mouse model. The self-assembled MSH was designed through the partial inclusion complexation associated with the threading of α-CD on the copolymer moieties on the surface of the PEGylated iron oxide (Fe 3 O 4 ) nanoparticles, which enables shear-thinning injection and controllable thermoreversible gel-sol transition. MSH was injected to the postoperative wound uniformly, which became mobile and perfect match with irregular cavity without blind angle due to the magnetocaloric gel-sol transition when exposed to alternating current magnetic field (ACMF). The magnetic nanoparticle-mediated induction heat during the gel-sol transition process caused the triggered release of dual-encapsulated chemotherapeutic drugs and provided an effect of thermally induced cell damage. The hierarchical structure of the MSH ensured that both hydrophobic and hydrophilic drugs can be loaded and consecutively delivered with different release curves. The hydrogel nanocomposite might provide a potential locally therapeutic approach for the precise treatment of locoregional recurrence of cancer. Tumor recurrence after resection represents several clinical challenges. In this study, we prepared shear-thinning injectable magnetic supramolecular hydrogel (MSH) and demonstrated their therapeutic applications in preventing the post-operative recurrence of breast cancer with facile synthesis and minimally invasive implantation in vivo. MSH was injected to the postoperative wound uniformly, which become mobile and perfect match with irregular cavity without blind angle through magnetocaloric gel-sol transition when exposed to ACMF. The magnetic nanoparticles mediated induction heat during the gel-sol transition process caused the triggered release of dual-encapsulated chemotherapeutic drugs as well as thermally induced cell damage. This study demonstrates that MSH with the controlled administration of combined thermo-chemotherapy exhibit great superiority in terms of preventing post-operation cancer relapse. Copyright © 2018 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.
Facile Synthesis of Smart Nanocontainers as Key Components for Construction of Self-Healing Coating with Superhydrophobic Surfaces.

PubMed

Liang, Yi; Wang, MingDong; Wang, Cheng; Feng, Jing; Li, JianSheng; Wang, LianJun; Fu, JiaJun

2016-12-01

SiO2-imidazoline nanocomposites (SiO2-IMI) owning high loading capacity of corrosion inhibitor, 1-hexadecyl-3-methylimidazolium bromide (HMID), and a special acid/alkali dual-stimuli-accelerated release property have been synthesized via a one-step modified Stöber method. SiO2-IMI were uniformly distributed into the hydrophobic SiO2 sol to construct "host"-"guest" feedback active coating with a superhydrophobic surface (SiO2-IMI@SHSC) on aluminium alloy, AA2024, by dip-coating technique. SiO2-IMI as "guest" components have good compatibility with "host" sol-gel coating, and more importantly, once localized corrosion occurs on the surface of AA2024, SiO2-IMI can simultaneously respond to the increase in environmental pH around corrosive micro-cathodic regions and decrease in pH near micro-anodic regions, promptly releasing HMID to form a compact molecular film on the damaged surface, inhibiting corrosion spread and executing a self-healing function. The scanning vibrating electrode technique (SVET) was applied to illustrate the suppression process of cathodic/anodic corrosion activities. Furthermore, benefiting from the superhydrophobic surface, SiO2-IMI@SHSC remained its protective ability after immersion in 0.5 M NaCl solution for 35 days, which is far superior to the conventional sol-gel coating with the same coating thickness. The facile fabrication method of SiO2-IMI simplifies the construction procedure of SiO2-IMI@SHSC, which have great potential to replace non-environmental chromate conversion coatings for practical use.

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