Browsing by Author "Imran, S.M"

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    Aminated polyethersulfone-silver nanoparticles (AgNPs-APES) compositemembranes with controlled silver ion release for antibacterial and water treatment applications
    (Materials Science and Engineering C, 2016-02-10) Haider, M. Salman; Shao, Godlisten N.; Imran, S.M; Park, Seongsoo; Abbas, Nadir; Tahir, M.S; Hussain, Manwar; Bae, Wookeun; Kim, HT
    The present study reports the antibacterial disinfection properties of a series of silver nanoparticle (AgNP) immobilized membranes. Initially, polyethersulfone (PES) was functionalized through the introduction of amino groups to form aminated polyethersulfone (NH2-PES, APES). AgNPs were then coordinately immobilized on the surface of the APES composite membrane to formAgNPs-APES. The properties of the obtainedmembrane were examined by FT-IR, XPS, XRD, TGA, ICP-OES and SEM-EDAX analyses. These structural characterizations revealed that AgNPs ranging from 5 to 40 nm were immobilized on the surface of the polymer membrane. Antibacterial tests of the samples showed that the AgNPs-APES exhibited higher activity than the AgNPs-PES un-functionalized membrane. Generally, the AgNPs-APES 1 cm × 3 cm strip revealed a four times longer life than the un-functionalized AgNPs polymer membranes. The evaluation of the Ag+ leaching properties of the obtained samples indicated that approximately 30% of the AgNPs could be retained, even after 12 days of operation. Further analysis indicated that silver ion release can be sustained for approximately 25 days. The present study provides a systematic and novel approach to synthesize water treatment membranes with controlled and improved silver (Ag+) release to enhance the lifetime of the membranes.
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    Electroconductive performance of polypyrrole/graphene nanocomposites synthesized through in situ emulsion polymerization
    (JOURNAL OF APPLIED POLYMER SCIENCE, 2014-11-22) Imran, S.M; Shao, Godlisten N.; Haider, M. Salman; Abbas, Nadir; Hussain, Manwar; Kim, HT
    The present study demonstrates a modified in situ emulsion polymerization (EP) approach convenient for the formation of polypyrrole/graphene (PPy/GN) nanocomposites with harnessed conductivities. A series of PPy/GN nanocomposites were prepared by loading different weight percent (wt %) of GN during in situ EP of pyrrole monomer. The polymerization was carried out in the presence of dodecyl benzene sulfonic acid, which acts as an emulsifier and protonating agent. The microstructures of the nanocomposites were studied by scanning electron microscopy, transmission electron microscopy, X-ray diffraction, Fourier transform infrared, X-ray photoelectron spectroscopy, UV–vis spectroscopy, Raman spectroscopy, photoluminescence spectroscopy and thermogravimetric analyses. The electrical conductivities of the nanocomposite pellets pressed at different applied pressures were determined using four probe analyzer. The electrical conductivities of the nanocomposites were considerably enhanced as compared to those of the individual PPy samples pressed at the same pressures. An enhanced conductivity of 717.06 S m21 was observed in the sample with 5 wt % GN loading and applied pressure of 8 tons. The results of the present study signify that the addition of GN in the PPy polymer harnesses both electrical and thermal properties of the polymer. Thus, PPy/GN nanocomposites with superior properties for various semiconductor applications can be obtained through direct loading of GN during the polymerization process.
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    Enhancement of electroconductivity of polyaniline/graphene oxide nanocomposites through in situ emulsion polymerization
    (Journal of Material Science, 2013-10-23) Imran, S.M; Shao, Godlisten N.; Kim, You Na; Hussain, Manwar; Choa, Yong-Ho; Kim, HT
    The present study introduces a systematic approach to disperse graphene oxide (GO) during emulsion polymerization (EP) of Polyaniline (PANI) to form nanocomposites with improved electrical conductivities. PANI/ GO samples were fabricated by loading different weight percents (wt%) of GO through modified in situ EP of the aniline monomer. The polymerization process was carried out in the presence of a functionalized protonic acid such as dodecyl benzene sulfonic acid, which acts both as an emulsifier and protonating agent. The microstructure of the PANI/GO nanocomposites was studied by scanning electron microscopy, transmission electron microscopy, X-ray diffraction, UV–Vis spectrometry, Fourier transform infrared, differential thermal, and thermogravimetric analyses. The formed nanocomposites exhibited superior morphology and thermal stability. Meanwhile, the electrical conductivities of the nanocomposite pellets pressed at different applied pressures were determined using the fourprobe analyzer. It was observed that the addition of GO was an essential component to improving the thermal stability and electrical conductivities of the PANI/GO nanocomposites. The electrical conductivities of the nanocomposites were considerably enhanced as compared to those of the individual PANI samples pressed at the same pressures. An enhanced conductivity of 474 S/m was observed at 5 wt% GO loading and an applied pressure of 6 t. Therefore, PANI/GO composites with desirable properties for various semiconductor applications can be obtained by in situ addition of GO during the polymerization process.
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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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    https://www.sciencedirect.com/science/article/abs/pii/S092633731500346X
    (Wiley, 2016) Imran, S.M; Shao, Godlisten N.; Kim, Heetaik
    We have synthesized unique flexible pressure-sensitivenanocomposites by means of a solution mixing method,by adding multiwalled carbon nanotubes (MWCNTs) into athermoplastic urethane (TPU) matrix along with poly(methyl methacrylate) (PMMA) microbeads of varioussizes. The influence of the various PMMA bead sizes onthe pressure sensing properties of the nanocompositeswas studied over a range of pressures. The PMMAmicrobeads were used to achieve an early percolationthreshold at low loadings of MWCNTs. We used scanningelectron microscopy to study the nanocomposites’ mor-phology, and conducted differential scanning calorimetryanalyses to investigate their thermal properties. The nano-composites’ electrical and thermal conductivities werealso measured under various applied pressures. Thenanocomposites displayed repeatable electricalresponses under various applied pressures, demonstrat-ing their suitability for use as pressure sensing materials.The proposed material is an ideal candidate for use in thepreparation of pressure-sensitive devices
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    Sol-gel synthesis of less expensive mesoporous titania-tin dioxide systems: Investigation of the influence of tin dioxide on the phase structure, morphology and optical properties
    (Elsevier, 2017) Shao, Godlisten N.; Imran, S.M; Abbas, Nadir; Kim, Heetaik
    Herein the influence of SnO2 on the optical, morphology and phase structure of mesoporous TiO2-SnO2 composites was examined. Composites with Sn/Ti ratio ranging from 0.1 to 5 were synthesized using less expensive sources in the absence of additives. The obtained samples were examined by XRD, HRTEM, SEM-EDAX, XPS, UV–vis DRS, XRF, TGA and nitrogen gas physisorption studies analyses. The physicochemical properties of the TiO2-SnO2 systems depended mainly on the Sn-to-Ti ratio, calcination temperature and the interaction between Sn4+and Ti4+. XRD results depicted that samples with Sn/Ti = 0.1 calcined at ≤600 °C exhibited pure anatase TiO2 crystals and the tendency of increasing Sn4+ content facilitated a phase transformation to attain rutile structure. Optical analyses of the samples showed that the absorption of the samples can be extended into the visible region. This study provides a systematic and economical method for large-scale production of TiO2 based composites with desirable properties for various applications.
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    Sol–gel synthesis of photoactive kaolinite-titania: Effect of the preparation method and their photocatalytic properties
    (Elsevier, 2015) Shao, Godlisten N.; Imran, S.M; Kim, Heetaik
    Supporting TiO2 on different materials is a potential strategy to improve the photochemical properties of the resulting composites. Kaolinite (K) was used as a support to synthesize a series of kaolinite-titania (K-TiO2) photocatalysts with desirable properties for decolorization of organic contaminants. Initially, TiO2 sol was formed through gelation of titanium oxychloride using ammonium hydroxide solution and subsequent peptization of the preformed gel in a low concentration of nitric acid. The sol was reacted with different concentrations of kaolinite at different pH conditions to yield K-TiO2 composites with different TiO2 compositions. The physicochemical properties of the photocatalysts were examined by XRD, FTIR, TGA, SEM-EDAX, XRF, UV–visible DRS, TEM and nitrogen gas physisorption studies analyses. XRD results revealed that through varying pH of the reaction a mixture of TiO2 crystals can be attained in the sintered samples. A simple photocatalytic experiment of the calcined photocatalysts was carried out to evaluate the decolorization of methylene blue in the presence of an artificial UV source. The obtained results were exquisitely compared to those of the ZrO2-TiO2 based composites obtained in our previous study. It was revealed that the amount of TiO2 in the composites and the calcination temperature had a profound effect on the microstructure and photocatalytic performance of the samples. Thus, the KT34- 600 sample exhibited the highest activity of all due to its superior properties. This study provides a criterion for selection of precursors, synthetic routes and support suitable for the formation of metal oxides composites with desirable properties for heterogeneous catalysis.
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    Sol–gel synthesis of photoactive zirconia–titania from metal salts and investigation of their photocatalytic properties in the photodegradation of methylene blue
    (Powder Technology, 2014-03-11) Shao, Godlisten N.; Imran, S.M; Jeon, Sunjeong; Engole, Marion; Abbas, Nadir; Haider, M. Salman; Kang, Shin Jae; Kim, HT
    Photoactivemetal oxide systems capable of reducing non-biodegradable pollutants are highly needed heterogeneous catalysts for environmental purification. Most of the currently available heterogeneous catalysts are obtained from complicated synthetic routes using expensive and perhaps hazardous precursors. The present study reports a novel sol–gelmethod to synthesize pure TiO2 and ZrO2–TiO2 samples using titanium oxychloride as TiO2 precursor and zirconyl nitrate hydrate as a ZrO2 source in the presence of the surfactant. The ratio of Zr-to- Ti was controlled between 0.75 and 3.2 to evaluate the effect of the amount of ZrO2 in the composites. Consequently, the precipitates were calcined at different temperatures to investigate the effect of removing the template at different sintering temperatures. The physico-chemical properties of the samples were examined by SEM, HRTEM, DT-TGA, XRD, FTIR, XRF, EDX, nitrogen gas physisorption and UV–visible diffusive reflectance spectrometry analyses. These analyses revealed that the crystallization, dispersion, particle size and shape of the samples are critically dependent upon the calcination temperatures and Zr-to-Ti ratios. Abnormal grain growth (AGG) was unexpectedly observed in the samples calcined at higher temperatures (≤800 °C). Comparisons of the activities of the samples toward decolorization of methylene blue indicated that the photocatalytic efficiencies of the composites with Zr/Ti ≤ 2.2 were superior to that of pure TiO2.
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    Sol–gel synthesis of sodium silicate and titanium oxychloride based TiO2–SiO2 aerogels and their photocatalytic property under UV irradiation
    (Chemical Engineering Journal, 2013-07-26) Kim, You Na; Shao, Godlisten N.; Jeon, Sunjeong; Imran, S.M; Sarawade, PB; Kim, HT
    Binary titania–silica metal oxides (TiO2–SiO2) have preferentially been used as photocatalysts for the degradation of organic contaminants under UV irradiation. Herein we synthesized TiO2–SiO2 aerogel powders with different Si-to-Ti ratios suitable for decolorization of organic pollutants using less expensive silica source (sodium silicate) and titanium oxychloride as a titania precursor. Consequently, the surfaces of the alcogels were hydrophobized using trimethylchlorosilane (TMCS) as a silylating agent to yield hydrophobic aerogel powders at ambient pressure drying. The as-prepared samples were calcined at different temperatures ranging from 200 to 1000 C to evaluate the effect of the heat treatment in the microstructure of the aerogels. The physico-chemical properties of the aerogels were examined by XRD, FTIR, XRF, TEM, SEM, N2 gas physisorption studies, TGA/DTA and diffusive reflectance spectrometry analyses. It was found that calcination temperature is an important factor in improving the porosity and crystallinity of the aerogels however; it has a detrimental effect on the hydrophobicity and photochemical performance of the aerogels. The as-synthesized aerogels were hydrophobic and exhibited the highest activity toward decolorization of methylene blue. The hydrophilic aerogels were obtained after calcination at temperature P500 C however; the formed samples possessed lower activities. Hydroxyl radicals ( OH) detection experiment performed in the presence of the photocatalysts indicated that the generation of radicals during irradiation increases with increasing illumination time.
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    Sol–gel synthesis of sodium silicate and titanium oxychloride based TiO2–SiO2 aerogels and their photocatalytic property under UV irradiation
    (Elsevier, 2013-07-26) Kim, You Na; Shao, Godlisten N.; Jeon, Sunjeong; Imran, S.M; Sarawade, PB; Kim, HT
    Binary titania–silica metal oxides (TiO2–SiO2) have preferentially been used as photocatalysts for the degradation of organic contaminants under UV irradiation. Herein we synthesized TiO2–SiO2 aerogel powders with different Si-to-Ti ratios suitable for decolorization of organic pollutants using less expensive silica source (sodium silicate) and titanium oxychloride as a titania precursor. Consequently, the surfaces of the alcogels were hydrophobized using trimethylchlorosilane (TMCS) as a silylating agent to yield hydrophobic aerogel powders at ambient pressure drying. The as-prepared samples were calcined at different temperatures ranging from 200 to 1000 C to evaluate the effect of the heat treatment in the microstructure of the aerogels. The physico-chemical properties of the aerogels were examined by XRD, FTIR, XRF, TEM, SEM, N2 gas physisorption studies, TGA/DTA and diffusive reflectance spectrometry analyses. It was found that calcination temperature is an important factor in improving the porosity and crystallinity of the aerogels however; it has a detrimental effect on the hydrophobicity and photochemical performance of the aerogels. The as-synthesized aerogels were hydrophobic and exhibited the highest activity toward decolorization of methylene blue. The hydrophilic aerogels were obtained after calcination at temperature P500 C however; the formed samples possessed lower activities. Hydroxyl radicals ( OH) detection experiment performed in the presence of the photocatalysts indicated that the generation of radicals during irradiation increases with increasing illumination time
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    Sol–gel synthesis of vanadium doped titania: Effect of the synthetic routes and investigation of their photocatalytic properties in the presence of natural sunlight
    (Elsevier, 2015) Shao, Godlisten N.; Imran, S.M; Kim, Heetaik
    The development of visible-light effective TiO2 allows low cost degradation of toxic non-biodegradable organic pollutants. In the present study a series of vanadium doped titania (V-TiO2) photocatalysts with V-to-Ti of 0.03, 0.06 and 0.1 were synthesized by either one-step or two-step modified sol-gel approaches. Titanium oxychloride solution was used as a titania source while vanadium pentaoxide was used as a vanadia source to form V-TiO2 in the absence of surfactants. One-step process was performed through the reaction of the TiO2 source with vanadium source. In two-step route the Ti(OH)4 gel was preformed through gelation of the TiO2 source using aqueous ammonium and then peptized in the acidic vanadium solution. The physicochemical properties of the samples were examined by XRF, XRD, UV-visible DRS, SEM-EDAX, TEM, DTA-TGA, XPS and nitrogen gas physisorption studies analyses. It was observed that the morphology, crystal structure and photochemical properties of the obtained samples were largely dependent on the calcination temperature, synthetic approach and V-to-Ti ratios. Calcination of the samples yielded large ultrafine and perhaps monodispersed particles with different sizes depending on the synthetic technique. The photocatalytic performance of the samples was tested in the photodegradation of methylene blue in the presence of natural sunlight. The photocatalytic activities of the samples synthesized by two-step route were higher than that of the samples yielded through one-step approach. Thus, the present report suggest systematic, convenient and cost-effective sol-gel techniques to yield V-TiO2 photocatalysts with harnessed photocatalytic performance for decolorization of toxic organic pollutants in the presence of natural solar irradiation.
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    Study of the Electroconductive Properties of Conductive Polymers-Graphene/Graphene Oxide Nanocomposites Synthesized via in Situ Emulsion Polymerization
    (Wiley, 2018) Imran, S.M; Shao, Godlisten N.; Kim, Heetaik
    The present study introduces a modified approach to synthesize polyaniline (PANI) and polypyrrole (PPy) doped with graphene oxide (GO) or graphene (GN) through an in situ emulsion polymerization (EP) technique. Dodecyl benzene sulfonic acid (DBSA) was used as a surfactant and doping agent as well during the polymerization reaction. The morphology and microstructure of the synthesized polymers and their nanocomposites were studied by scanning electron microscopy, transmission electron microscopy, Fourier transform infrared spectroscopy, X-ray photoelectron spectroscopy, and thermogravimetric analysis. All of these characterization techniques confirmed the superior morphology and thermal properties of the nanocomposites. The electroconductive properties of the synthesized polymers and their nanocomposite pellets containing 5 wt% of either GN or GO pressed at pressures of 2, 4, and 6 tons were investigated with a fourprobe analyzer. Nanocomposites showed very high electrical conductivity compared to individual PANI and PPy samples pressed at the same pressures. The addition of GO and GN not only improved the thermal stability but also significantly enhanced the electrical conductivity of the nanocomposites. Thus, the present work signifies the importance of the direct loading of GO and GN into conductive polymers during the EP process using DBSA as a surfactant to achieve nanocomposites with promising properties for various semiconductive applications.