Chee Wah Loy; Khamirul Amin Matori; M.M. Haslinawati; Mohd Hafiz Mohd Zaid; Norhazlin Zainnudin
Abstract
A low thermal diffusivity SiO2-based ceramic was fabricated by sintering Malaysia agricultural waste rice husk at 800 °C. This paper presents the effect of sintering temperatures on the phase transformation, microstructure and thermal diffusivity of rice husk ash (RHA) as a thermal insulating ...
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A low thermal diffusivity SiO2-based ceramic was fabricated by sintering Malaysia agricultural waste rice husk at 800 °C. This paper presents the effect of sintering temperatures on the phase transformation, microstructure and thermal diffusivity of rice husk ash (RHA) as a thermal insulating material. A series of SiO2-based ceramics were fabricated from rice husk via two sintering stages. Rice husk was pre-sintered at 700 °C and then ground into powder. The RHA powder was compacted into pellets and then re-sintered at a single temperature between 700 and 1400 °C. Sintering of the RHA induces phase transformation from amorphous silica to crystalline α-cristobalite, α-tridymite and β-tridymite. The thermal diffusivities of RHA were evaluated using the laser flash analysis technique. The results indicate RHA-800 °C has the lowest thermal diffusivity, which is 0.17 ± 0.1 mm 2 s −1 at 25 °C. The RHA particle morphologies were observed using a field-emission scanning electron microscopy. Low-frequency vibrational modes of silica such as lattice vibration were investigated using Fourier-transform infrared spectroscopy technique. X-ray fluorescence result indicated that RHA-800 °C contains ~90 wt % of SiO2.
Rosa D
Abstract
Noble metal nanostructures have demonstrated many intriguing features for both therapy and diagnosis in a number of diseases. However, their clinical translation is prevented by their accumulation in organisms that can result in toxicity and interference with common medical diagnoses. In order to combine ...
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Noble metal nanostructures have demonstrated many intriguing features for both therapy and diagnosis in a number of diseases. However, their clinical translation is prevented by their accumulation in organisms that can result in toxicity and interference with common medical diagnoses. In order to combine the most interesting behaviour of metal nanoparticles with the possibility of their body clearance, we have recently introduced and tested the passion fruit-like nano-architectures. They are versatile 100 nm biodegradable nanostructures composed by a silica shell embedding functional polymeric arrays of ultra-small noble metal nanoparticles. Here, we report a novel simple and robust protocol to increase the loading of ultra small gold nanoparticles in the nano-architectures, promoting their possible application in clinical diagnosis.
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.
Saruchi Surbhi; Praveen Aghamkar; Sushil Kumar
Abstract
Nanomaterials and nanostructures have received steadily growing interests as a result of their peculiar and fascinating properties and applications. Neodymia-silica nanocomposites were prepared by sol-gel route followed by calcination. The samples were prepared with different concentration of dopant ...
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Nanomaterials and nanostructures have received steadily growing interests as a result of their peculiar and fascinating properties and applications. Neodymia-silica nanocomposites were prepared by sol-gel route followed by calcination. The samples were prepared with different concentration of dopant (Nd2O3) and calcined in a programmable furnace at 1000 °C for 5 h. The structural evolution of samples was investigated by employing techniques such as XRD, FTIR and TEM. X-ray diffraction patterns showed that the samples were nanocrystalline and the size of crystallites has been determined using Debye-Scherrer relation. The FTIR spectra confirmed the presence of functional groups of prepared material. The particle size of samples was also estimated through TEM analysis. It has been observed that crystallinity as well as particle size of the samples increases with increase in dopant concentration.
Zhongsen Yang; Guangjun Zhou
Abstract
Hydrophobic CdSe/ZnS quantum dots (QDs) were embedded in a transparent functional silica film with thickness of 10-15 µm using a sol-gel method. Namely, the QDs were prepared through an organic synthesis using hexadecylamine as a capping agent. When partially hydrolyzed 3-aminopropyltrimethoxysilane ...
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Hydrophobic CdSe/ZnS quantum dots (QDs) were embedded in a transparent functional silica film with thickness of 10-15 µm using a sol-gel method. Namely, the QDs were prepared through an organic synthesis using hexadecylamine as a capping agent. When partially hydrolyzed 3-aminopropyltrimethoxysilane (APS) sol was mixed with a toluene solution of the QDs, the ligand exchange occurred. With subsequent addition of pure H2O, the QDs were transferred into APS sol accompanied with a phase separation. The APS sol with the QDs was condensed to adjust its’ viscosity by the evaporation of solvents at room temperature. After that, functional SiO2 films with tunable QD concentrations and high photoluminescence (PL) efficiency were fabricated by a spin-coating strategy using the condensed APS sol with the QDs. The absorbance at first absorption peak of the QDs revealed a liner increase against the QD concentrations in these films. The PL peak wavelength and full width at half maximum of PL spectra of the QDs in these films remained unchange compared with their initial values in toluene. The QDs were mono-dispersed in these films according to transmission electron microscopy observation. Due to unique properties, these films are utilizable for further applications in optical and electronic devices.
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.
