Shauna Robbennolt; Stephen S. Sasaki; Tylisia Wallace; Marquise Bartholomew; Sarah H. Tolbert
Abstract
We present a new solution-phase, sol-gel based spin-coating method to fabricating high quality, nickel zinc ferrite (NZFO) thin films. The effect of annealing temperature on the microstructure, static magnetic properties and X-band FMR linewidth and resonance field was investigated. Furthermore, the ...
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We present a new solution-phase, sol-gel based spin-coating method to fabricating high quality, nickel zinc ferrite (NZFO) thin films. The effect of annealing temperature on the microstructure, static magnetic properties and X-band FMR linewidth and resonance field was investigated. Furthermore, the effect of composition on these properties was explored in films with the formula NixZn(1-x)Fe2O4 (where x = 0 to 1 in 0.1 increments). Films annealed at the highest annealing temperature of 1100 ?C were found to have the highest saturation magnetization and coercivity, as well as the lowest FMR linewidths. Films with the composition Ni0.3Zn0.7Fe2O4 were found to have the lowest linewidths along with favorable magnetic properties for microwave applications. The champion film showed an FMR linewidth of 93 G, corresponding to a low Gilbert damping coefficient of α = 0.003, a saturation magnetization of 330 emu/cm 3 , and a coercivity and anisotropy field of 14 and 62 Oe respectively.
Jazmín I. González; Diana M. Escobar; Claudia P. Ossa
Abstract
Hydroxyapatite is one of the appropriate materials for hard tissue engineering because it is the inorganic structural constituent of bones and teeth, and hydroxyapatite has been evaluated to compare the mechanical properties, processing as scaffolds to evaluate the influence of porosity, since the elastic ...
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Hydroxyapatite is one of the appropriate materials for hard tissue engineering because it is the inorganic structural constituent of bones and teeth, and hydroxyapatite has been evaluated to compare the mechanical properties, processing as scaffolds to evaluate the influence of porosity, since the elastic modulus of material is influenced by the porosity, it is essential to establish a relationship between the two characteristics to obtain a material with optimum conditions for its implantation. The main objective of this research was to study the mechanical properties of hydroxyapatite scaffolds using compression and nanoindentation tests. The scaffolds were manufactured by gel-casting and gel-casting combined with foam polymer infiltration, in both cases 40 and 50% solids and three different monomers were used. The samples obtained by gel-casting exhibited a compressive strength between 0.93 and 6.15 MPa, an elastic modulus between 11.46 and 27.27 GPa; some of these scaffolds showed very similar values to human trabecular bone reported. In addition, samples produced by gel-casting combined with foam polymer infiltration, it was found that compressive strength was between 0.05 and 0.12 MPa, the elastic modulus between 1.61 and 6.24 GPa, concluding that the gel-casting produces scaffolds with closest to trabecular bone.
Devender Singh; Suman Sheoran; Vijeta Tanwar
Abstract
In this review article, different synthetic procedures and characterization techniques used for the development of materials are discussed briefly. The stability and high luminous intensity of silicate materials makes them practically important in the field of white light emitting diodes (WLEDs). During ...
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In this review article, different synthetic procedures and characterization techniques used for the development of materials are discussed briefly. The stability and high luminous intensity of silicate materials makes them practically important in the field of white light emitting diodes (WLEDs). During the experimental designing of our research, we have understood carefully the theoretical and methodological strategy regarding the synthesis of phosphors and then, a large number of silicate-based luminescent materials have been prepared using sol-gel technology. Among them, a series of silicate materials having composition M(2-x)EuxSi2O7 (M = Y, Gd, La and x = 0.03 moles) have been described in this review prepared with sol-gel process. Intense peak in europium (III) doped M2Si2O7 silicates originate from 5 D0→ 7 F2 transition of Eu 3+ ion available in crystal lattices. X-ray diffraction pattern have triclinic structure for Y2Si2O7 and Gd2Si2O7 silicate phosphors. However, hexagonal and monoclinic structures are obtained for La2Si2O7 material at different temperatures employed for further annealing. Transmission electron microscopic analysis is used to study the morphology and particle size of prepared phosphors. Excellent luminescence response of these silicate phosphors make them suitable for photonic applications and also open up new avenues for solid-state lighting, cathode ray tubes, fluorescent lamps and scintillators etc.
Ana Flávia R. Silva; Nelcy D. S. Mohallem; Marcelo M. Viana
Abstract
In this work, TiO2 and Ag/TiO2 thin films were synthesized on glass by combination of sol-gel method and dip-coating deposition technique. Thermal treatment in temperatures ranging from 100 °C to 500 °C was used to evaluate changes in structure, morphology and texture of these materials. Adherent ...
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In this work, TiO2 and Ag/TiO2 thin films were synthesized on glass by combination of sol-gel method and dip-coating deposition technique. Thermal treatment in temperatures ranging from 100 °C to 500 °C was used to evaluate changes in structure, morphology and texture of these materials. Adherent and microcrack-free films were obtained. The structural and morphological evolution with temperature was studied by X-ray diffraction (XRD) and high resolution transmission electron microscopy (HRTEM). Average particle size and roughness were determined by atomic force microscopy (AFM). The films were tested for wettability by measuring the contact angle between a drop of distilled water and the material surface. Results of hydrophobic/hydrophilic tests using UV-C irradiation showed that the films change their hydrophobic character to hydrophilic reaching even the superhydrophilic character which indicates their potential application as self-cleaning coatings.
Vibha C; Lizymol P P
Abstract
Novel inorganic-organic hybrid resins [IOHRs] containing mixture of alkoxides of calcium/magnesium/zinc with polymerizable dimethacrylate groups were synthesised using a simple single-pot modified sol-gel method. Objective of the present study is to investigate the impact of calcium content over bioactivity, ...
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Novel inorganic-organic hybrid resins [IOHRs] containing mixture of alkoxides of calcium/magnesium/zinc with polymerizable dimethacrylate groups were synthesised using a simple single-pot modified sol-gel method. Objective of the present study is to investigate the impact of calcium content over bioactivity, polymerization shrinkage, and physico mechanical properties of bioactive IOHR containing mixture of alkoxides of calcium/magnesium/zinc having polymerizable methacrylate groups, along with various fillers they can be used as a dental restorative material. Various formulations with varying concentration of inorganic content were used during the synthesis. The concentration of inorganic content was optimised as 0.1% by weight of with respect to the silane. This optimised formulation based photocured composite [CMZ2] showed better DTS (35-40 MPa), FS (65-70 MPa), VHN (140-146 kg/mm 2 ), possess low shrinkage, non-cytotoxic in nature, bioactive with good cell adhesion and cell proliferation properties. CMZ2 was found to be a potential novel dental composite.
Somit Kumar Singh; Ananda Murthy H. C; Vandana Singh
Abstract
In the present investigation, the remediation of mercury by using the gum acacia-silica composite as an adsorbent has been studied. Experiments revealed optimum parameters which were found to be pH 6, contact time 2 hours, Hg(II) concentration of 100 ppm, reflux temperature 30 0 C and adsorbent dosage ...
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In the present investigation, the remediation of mercury by using the gum acacia-silica composite as an adsorbent has been studied. Experiments revealed optimum parameters which were found to be pH 6, contact time 2 hours, Hg(II) concentration of 100 ppm, reflux temperature 30 0 C and adsorbent dosage of 50 mg. The experimental data was subjected to modeling using the Langmuir and Freundlich isotherms. It was found that the data very well fitted to the Freundlich model. The pseudo second order kinetics confirms chemisorption with rate constant 3.1 × 10-4 gmg-1min-1. The calculated thermodynamic parameters (?G 0 , ?S 0 , ?H 0 ) revealed the exothermic and spontaneous nature of adsorption process at the solid–solution interface. The adsorbent could be recycled for six successive cycles with 31.5% loss in its efficiency. The adsorbent is found to be highly effective and economical for mercury remediation from water.
Elena Emanuela Valcu (Herbei); Viorica Musat; Susanne Oertel; Michael P.M. Jank; Timothy Leedham
Abstract
Solution-processed high-k dielectric hybrid thin films prepared at temperatures below 200 o C represent a subject of increasing scientific interest satisfying current requirements for printable thin film transistors used in transparent flexible electronics. In this work, we propose a new approach ...
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Solution-processed high-k dielectric hybrid thin films prepared at temperatures below 200 o C represent a subject of increasing scientific interest satisfying current requirements for printable thin film transistors used in transparent flexible electronics. In this work, we propose a new approach for the synthesis of new tantalum oxide-PMMA hybrid dielectric thin films at 160 o C by modified sol-gel method, using as precursors tantalum ethoxide cluster (Ta(OC2H5)5) and methyl methacrylate monomer (MMA). So far it has not been reported in situ formation of tantalum oxide nanocrystals in hybrid dielectric materials at this low temperature. Hybrid sols with 1:1 and 4:1 (Ta(OC2H5)5):MMA molar ratios were used for spin-coating of thin films. The thermal behavior of these sols was observed in order to optimize the post-deposition treatment of the films. The hybrid films were investigated by scanning electron microscopy (SEM) for thickness and morphology, by grazing incidence x-ray diffraction (GIXRD) and high-resolution transmission electron microscopy (HRTEM) for tantalum oxide phase formation. TaO2 single crystals with a diameter of about 2 nm embedded in an amorphous phase were identified. The dielectric properties of the hybrid thin films were derived from the characterization of Metal-Insulator-Metal (MIM) structures by current-voltage and capacitance-voltage measurements. I-V curves show a leakage current between 10 -12 and 10 -7 A and a constant capacitance in bias range ± 50 V. For films with 1:1 and 4:1 molar ratio, the leakage current density ranges between 10 -9 - 10 -3 A/cm 2 and 10 -9 - 10 -4 A/cm 2 , and the limit of the current density goes to an electric field of ±1.2 MV/cm and ±2.5 MV/cm, respectively. In the case of films with 1:1 molar ratio, the applied voltage was up to 70 V in positive domain and no breakdown was observed for the dielectric layer. These results show higher current density for a larger voltage range, than the characteristics leakage current values reported for PMMA (10 -8 A/cm 2 ) at 0.3 MV/cm. The value of the permittivity ranges between 3.5 and 7.5 at 1 MHz, depending on the tantalum alkoxyde: MMA molar ratio, suggesting very promising future of these hybrid dielectric thin films for the fabrication of transparent TFTs, which can serve for next generation of transparent and flexible electronic devices.
Vandana Singh; Devendra Singh
Abstract
In the present communication, we report on diastase alpha amylase immobilization at guar gum-silica nanohybrid material (H5). The immobilized amylase (H5-Amyl) showed significantly higher bioactivity (21.62 U mg -1 ) as compared to free amylase (15.59 U mg -1 ) in solution at pH 5 and temperature 40°C. ...
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In the present communication, we report on diastase alpha amylase immobilization at guar gum-silica nanohybrid material (H5). The immobilized amylase (H5-Amyl) showed significantly higher bioactivity (21.62 U mg -1 ) as compared to free amylase (15.59 U mg -1 ) in solution at pH 5 and temperature 40°C. The kinetic parameters of the free (Km = 10.66 mg L -1 ; Vmax = 1.36 µmolemL -1 .min -1 ) and the immobilized enzyme (Km = 6.11 mg mL -1 ; Vmax = 1.45 µmolemL -1 .min -1 ) revealed that the immobilization has increased the overall catalytic property of the enzyme. The immobilized enzyme on recycling could show 87% of initial activity even in the sixth cycle. Since immobilization did not hamper the enzymatic reaction rate, the biocatalyst may be suitably exploited in food and pharmaceutical industries.
Ammar Elsanousi; Kamal Khalifa Taha; Nazar Elamin
Abstract
Nanocrystalline porous titania with rutile and anatase bi-phase structure has been fabricated by the sol-gel method without the introduction of any surfactant, using tetrabutile titanate as precursor. The porous material was integrated as an electrode in a dye-sensitized solar cell as an electrode and ...
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Nanocrystalline porous titania with rutile and anatase bi-phase structure has been fabricated by the sol-gel method without the introduction of any surfactant, using tetrabutile titanate as precursor. The porous material was integrated as an electrode in a dye-sensitized solar cell as an electrode and its photoelectrical parameters were measured. Experimental measurements showed that the cell exhibits higher values of short-circuit current density and overall conversion efficiency compared to P25 (typical commercial titania powder) cells. The overall conversion efficiency of both samples was calculated to be 2.81 and 1.57 for the prepared and commercial (P-25) sample respectively. This drastic increase in the conversion efficiency of the prepared sample was attributed to its high surface area and porous structure, allowing more sensitizer dye to be chemically anchored in the electrode and, as a consequence, improved the light harvesting drastically. These results indicate that it is possible to achieve commendable conversion efficiencies using porous bi-phase titania.
Vinod Kumar; L. P. Purohit;Fouran Singh; R. G. Singh
Abstract
Swift heavy ion (SHI) induced modification in structural and optical properties of undoped and doped nanocrystalline (nc) ZnO films deposited by sol-gel method are investigated. These nanocrystalline films were irradiated by MeV ions of Au, Ag and Ni at various ion fluences. The structural properties ...
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Swift heavy ion (SHI) induced modification in structural and optical properties of undoped and doped nanocrystalline (nc) ZnO films deposited by sol-gel method are investigated. These nanocrystalline films were irradiated by MeV ions of Au, Ag and Ni at various ion fluences. The structural properties were studied using X-ray diffraction and it shows that the average crystallite size of ZnO films is observed to increase by the irradiation. The atomic force microscopy (AFM) study of films shows that the roughness of the films varies with increase in the fluence. A maximum transmittance is observed to be 85% in the visible region for doped films. It is also shown that the bandgap of undoped and doped ZnO films is varied using SHI irradiation. The modifications of structural and optical properties are explained in terms of thermal spikes induced by SHIs.
M. F. R. Fouda; M. A. Wahba;M. F. El-Shahat; M. B. ElKholy; S. A. Mostafa; A. I. Hussien
Abstract
AnchorUniform α-Fe2O3 nanoparticles have been prepared by sol gel method using three different carboxylic acids citric, tartaric and succinic acids as chelating agents. The structure and morphology of α-Fe2O3 samples were characterized using (TGA), (XRD), (TEM), (IR) and diffuse reflectance ...
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AnchorUniform α-Fe2O3 nanoparticles have been prepared by sol gel method using three different carboxylic acids citric, tartaric and succinic acids as chelating agents. The structure and morphology of α-Fe2O3 samples were characterized using (TGA), (XRD), (TEM), (IR) and diffuse reflectance spectroscopy (DRS) techniques. The TEM images revealed that in all cases, the products consisted of 18–25 nm sized particles close to the average crystallite size calculated from XRD data by the Scherrer’s formula. Among the prepared samples, the sample that has the best thermal stability, the smallest particle size and the reddest color is that prepared in presence of tartaric acid. The prepared samples were evaluated as pigments according to the American Society for Testing and Materials (ASTM) standard methods for evaluation of pigments.
Surender Duhan; B.S. Dehiya;Vijay Tomer
Abstract
Sol–gel chemistry has recently attracted a large attention with a view of preparation of silver-silica nano-composites for photo-catalytic applications. This method of synthesis allows glassy materials to be prepared at a much lower temperature than the traditional melt-glass techniques. Moreover, ...
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Sol–gel chemistry has recently attracted a large attention with a view of preparation of silver-silica nano-composites for photo-catalytic applications. This method of synthesis allows glassy materials to be prepared at a much lower temperature than the traditional melt-glass techniques. Moreover, it enables higher doping concentrations and a more uniform distribution of silver in the glass host matrix to be achieved. This method produces large quantities of amorphous gels that are thermal treated in air at the temperature of 500°C for one hour. The silver-silica samples were investigated through X-ray diffraction (XRD for the determination of their microstructure, phase and compositions. It is found that the microstructure depends closely on the solution pH and the extent of silver-doping. MB dye degradation by undoped and Ag doped SiO2 was studied under UV and Visible light irradiation. The results are intriguing as the doping by Ag produces opposite effects on photocatalytic degradation rates under the two conditions.
Jasneet Kaur; Jaspreet Kaur; R. K. Kotnala; Vinay Gupta; Kuldeep Chand Verma
Abstract
In the present work, the self-assembly of Co 2+ and Fe 3+ doped SnO2 nanoparticles (Co and Fe = 5 mol% each) into nanorods by co-doping of Ce 3+ (4 mol%) ions is studied. The nanorods are prepared by a chemical route using polyvinyl alcohol as surfactant with the composition Sn0.91Co0.05Ce0.04O2 (SCC54) ...
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In the present work, the self-assembly of Co 2+ and Fe 3+ doped SnO2 nanoparticles (Co and Fe = 5 mol% each) into nanorods by co-doping of Ce 3+ (4 mol%) ions is studied. The nanorods are prepared by a chemical route using polyvinyl alcohol as surfactant with the composition Sn0.91Co0.05Ce0.04O2 (SCC54) and Sn0.91Fe0.05Ce0.04O2 (SFC54). The X-ray diffraction (XRD), transmission electron microscopy (TEM), magnetic and electrical measurements are used to characterize these nanorods. The XRD pattern show the tetragonal rutile and polycrystalline nature of SnO2 nanorods which is also confirmed by TEM. The TEM images exhibit that the diameter of SCC54 nanorods lie in the range of 15-20 nm, length~100-200 nm whereas for SFC54 specimen, diameter ~5-15 nm and length ~50-100 nm. In our previous work, we fabricated Co and Fe (3 and 5 mol% each) doped SnO2 nanoparticles which exhibited high ferromagnetism. It is observed that on Ce 3+ co-doping, nanoparticles assembled themselves into rod like structures and the values of saturation magnetization and dielectric properties have further enhanced. Thus the nature and the concentration of dopants are found to play crucial role in tuning the morphology, magnetic and electrical properties of nanostructures. The values of saturated magnetization (Ms) are 1.14 and 0.14 emu/g and coercive field are 112 and 42 Oe, in SCC54 and SFC54 specimen, respectively, at room temperature. The variation in dielectric behavior is attributed due to the interface polarization. However, in lower frequency regime, the decreasing trend of dielectric permittivity with increasing frequency is explained by the Maxwell-Wagner theory and Koops’ model, whereas, in higher frequency region, the resonant behavior is observed due to nano size effect.
Kavita Verma; Seema Sharma; Dhananjay K Sharma; Raju Kumar; Radheshyam Rai
Abstract
Ba0.5Sr0.3TiO3 (BST 70/30) nanopowders have been prepared by the modified sol-gel method using barium acetate, strontium acetate and titanium isopropoxide as the precursor. The formation mechanism, phase evolution, and particle size have been investigated using TG/DTA, XRD, and SEM. The fine particles ...
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Ba0.5Sr0.3TiO3 (BST 70/30) nanopowders have been prepared by the modified sol-gel method using barium acetate, strontium acetate and titanium isopropoxide as the precursor. The formation mechanism, phase evolution, and particle size have been investigated using TG/DTA, XRD, and SEM. The fine particles of the nano-powders calcined are homogeneous and well-dispersed and their narrow size distribution is about 15–25 nm. The as-formed gel was dried at 2000 C and then calcined in the temperature range 6500 C to 8500 C for crystallization. Phase evolution during calcination was studied using X-ray diffraction (XRD) technique which exhibited cubic crystal structure with perovskite phase. Sintering of the pellet was performed at 9500 C and the study on the dielectric relaxation and the ac electrical conductivity behavior of modified Barium titanate, Ba0.5Sr0.3TiO3 ferroelectric ceramic exhibit that these are thermally activated process.
Vandana Singha; Sadanand Pandeya;Rashmi Sanghib; Somit Kumar Singha
Abstract
In continuation to our recent study on the synthesis and characterization of starch-silica nanocomposite, in the present study the nanocomposite has been evaluated for the removal of Cd(II) from the aqueous solution. The conditions for the sorption have been optimized and kinetic and thermodynamic studies ...
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In continuation to our recent study on the synthesis and characterization of starch-silica nanocomposite, in the present study the nanocomposite has been evaluated for the removal of Cd(II) from the aqueous solution. The conditions for the sorption have been optimized and kinetic and thermodynamic studies were performed to understand the adsorption behaviour of the composite. Though the cadmium sorption by the nanocomposite takes place in wide pH range, pH 7.5 was found most favorable and at this pH the adsorption equlibrium data were modeled using the Langmuir and Freundlich isotherms at 10°C, 20°C, 30°C and 40°C. At all the temperatures, the data fitted more satisfactorily to Langmuir isotherm indicating unilayer adsorption. Based on Langmuir model, Qmax was calculated to be 769.23 mg/g. The adsorption showed pseudo second order kinetics with a rate constant of 5.65 × 10 -5 g mg -1 min -1 (at 100 mg/L initial Cd(II) concentration) indicating chemisorption. The thermodynamic study revealed the endothermic and spontaneous nature of the adsorption. Effect of electrolyte on the adsorption was also studied. The nanocomposite was sucessfully recycled for six consecutive adsorption-desorption cycles with only a marginal loss in its efficiency indicating its high reusability. The composite was found to be a highly stable photoluminescent Cd(II) adsorbent which may be suitable for sensor applications in detecting the metal ions both in vivo and vitro as the material is natural polymer based.
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