Browsing by Author "Sarawade, Pradip B."

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    BET Study of Silver-Doped Silica Based on an Inexpensive Method
    (Materials Letters, 2012-04-28) Hilonga, Askwar; Kim, Jong-gil; Sarawade, Pradip B.; Quang,Dang Viet; Shao, Godlisten N.; Elineema, Gideon; Kim, Hee Taik
    The aimof this study is to identify an acid precursor that ismost desirable for the synthesis of sodiumsilicate-based silver-doped silica for large-scale industrial production. The final products were developed based on the presence of silver (silver-doped silica) or the absence of silver (pure silica). The properties of the obtained final products were examined using the BET method. This method involves characterization based on N2 physisorption studies to determine the surface area, pore diameter, and pore volume. Various graphs were plotted using the obtained data to describe the pore size distribution, isotherms, and the properties of hysteresis loops. Silver-doped silica with a BET surface area of up to 357 m2/g and a pore size of 5.4 nm was obtained using the most desirable precursors—sodium silicate and sulfuric acid. This is an unprecedented step toward synthesis of silver-doped silica fromdesirable precursors. This approach to the synthesis of silica with desirable propertieswithout involving sacrificial templates (surfactants) will be convenient for many applications and suitable for large-scale economic industrial production.
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    Effect of various structure directing agents on the physicochemicalproperties of the silica aerogels prepared at an ambient pressure
    (Applied Surface Science, 2011-09-11) Sarawade, Pradip B.; Shao, Godlisten N.; Quang, Dang Viet; Kim, Hee Taik
    tWe studied the effects of various surfactants on the textural properties (BET surface area, pore size,and pore volume) of the silica aerogels prepared at an ambient pressure. A simple surface modificationof silica gel prepared at an ambient pressure through hydrolysis and polycondensation of TEOS as asilica precursor was conducted using various structure directing agents. The treatment was found toinduce a significant difference in the porosity of the silica aerogel. Highly porous silica aerogels withbimodal porous structures were prepared by modifying the surface of the silica wet-gel (alcogel) withtrimethylchlorosilane (TMCS) in order to preserve its porosity. The samples were analyzed by small-angleX-ray scattering and nitrogen adsorption. In this work, a possible new type of highly porous hydrophobicsilica aerogel with a bimodal porous structure is presented. A hydrophilic extremely porous (high surfacearea and large pore volume) silica aerogel was obtained by heating the as-synthesized hydrophobicsilica aerogel at 400◦C for 1 h. There was a significant effect of structure directing agent on the texturalproperties, such as specific surface area, pore size distribution and cumulative pore volume of the silicaaerogels.
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    Enhancement of porosity of sodium silicate and titanium oxychloride based TiO2–SiO2 systems synthesized by sol–gel process and their photocatalytic activity
    (Microporous and Mesoporous Materials, 2012-11-09) Shao, Godlisten N.; Kim, You Na; Imran, S.M; Jeon, Sunjeong; Sarawade, Pradip B.; Hilonga, Askwar; Kim, Jong-gil; Kim, Hee Taik
    The textural properties of TiO2–SiO2 composites (TSCs) were successively enhanced using three approaches; (1) washing the hydrogels with different solvents, (2) using surfactant and (3) forming the TiO2 sol in ethanol medium. The sol–gel process was exquisitely used to form the composites using cost effective precursors. Initially, the precipitated hydrogels were washed with water or alcohol to evaluate the influence of washing on the dried hydrogels. Consequently, two composites were formed differently in the presence of stearic acid (SA) as a surfactant and the other by forming TiO2 sol in ethanol medium prior to reaction with silica source. The TSC powders were examined by XRD, N2 physisorption studies, FTIR, TGA, SEM, XRF and HRTEM. The BET surface area of the sample obtained after washing the hydrogels with ethanol (TSCE) was the largest (594 m2/g) while porosities of the composites obtained using stearic acid as a surfactant (TSCSA, 0.96 cm3/g) and ethanol as a medium to form the TiO2 sol (TSCES, 1.85 cm3/g) were relatively superior to those obtained under influence of changing washing solvent. Photocatalytic decolorization of methylene blue by the composites calcined at 800 C revealed that the TSCES-800 possessed the highest activity of all the composites due to its superior properties.
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    Silver-Doped Silica Powder with Antibacterial Properties
    (Powder Technology, 2011-10-08) Hilonga, Askwar; Kim, Jong-gil; Sarawade, Pradip B.; Quang, Dang Viet; Shao, Godlisten N.; Elineema, Gideon; Kim, Hee Taik
    In this study a simple and reproduciblemethodwas used to develop silver-doped silica powder with antibacterial properties. Silicamatriceswere synthesized via a sol–gel route which allows one to easily tailor textural and chemical properties. A wide range of silica-materials/products was obtained via the present route. These are: pure silver nanoparticles (Ag0), silver in ionic state (Ag+), AgCl nanoparticles, and the mixture of Ag0 and AgCl. The efficacy of these products were tested against Escherichia coli and the results demonstrate thatmaterials that are suitable for antibacterial applications were obtained by this newly developed technique while utilizing sodium silicate, which is relatively inexpensive, as a silica precursor. This may significantly boost the industrial production of the inexpensive silver-doped silica products for various applications. A project on other innovative industrial applications of our products is in progress.
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    Synthesis of Silver Nanoparticles within the Pores of Functionalized-Free Silica Beads: The Effect of Pore Size and Porous Structure
    (Materials Letters, 2011-10-29) Quang, Dang Viet; Sarawade, Pradip B.; Hilonga, Askwar; Kim, Jong-gil; Shim, YoungHo; Shao, Godlisten N.; Kim, Hee Taik
    Here, we report on the synthesis of silver nanoparticles (Ag-NPs) manipulating the pores of silica beads (SBs) with sizes ranging from 0.5 to 1 mm. Silver ions were occluded inside the pores of SBs and in situ reduced to Ag-NPs using Sodium borohydride (NaBH4). SBs with different average pore diameters from 3.8 to 20 nm were used to assess the effect of their pore sizes and porous structures on the formation of Ag-NPs. Obtained results revealed that the silver amount occluded inside pores increases along with the increase of total pore volume. The particle sizes of the synthesized Ag-NPs mainly distribute from 8 to 15 nm and vary with the pore sizes and porous structure.