Browsing by Author "Shao, Godlisten N."
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Item 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, HTThe 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.Item 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 TaikThe 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.Item Biodiesel production by sulfated mesoporous titania–silica catalysts synthesized by the sol–gel process from less expensive precursors(Chemical Engineering Journal, 2012-11-21) Shao, Godlisten N.; Sheikh, Rizwan; Hilonga, Askwar; Lee, Jae Eun; Park, Yeung-Ho; Kim, HTA sulfated titania–silica composite (S-TSC) was obtained through surface modification of mesoporous titania–silica composite synthesized using less expensive precursors; titanium oxychloride and sodium silicate as titania and silica sources respectively. A pre-formed titania sol facilitated the synthesis of a mesoporous composite with a high BET surface area (520 m2/g), suitable for surface modification using sulfuric acid to improve its catalytic performance. The materials synthesized via this process were examined by XRD, XRF, FTIR, SEM, TEM, TGA, and N2 physisorption studies. FTIR analysis showed the vibration band of the TiAOASi bond at 943 cm 1, suggesting the incorporation of titania into silica to form a composite. This vibration band was substantially shifted to 952 cm 1 after the attachment of the sulfate group. The catalytic activity of a series of as-prepared TSC, S-TSC calcined samples and pure H2SO4 were evaluated for esterification of oleic acid and transesterification of waste oil with methanol to yield methyl esters. It was observed that at these reaction conditions, S-TSC-450 and S-TSC-550 possessed high catalytic activity comparable to that of pure H2SO4 implying that surface modification of the titania–silica composite improves its acidic properties.Item Characterization of Calcium-Doped Silica Gel Prepared in an Aqueous Solution(Resources Processing, 2012-02-20) Quang, Dang Viet; Park, Jin Koo; Kim, Jong-gil; Elineema, Gideon; Shao, Godlisten N.; Lee, Jae Eun; Kim, Hee TaikIn this study, calcium-doped silica was prepared by modifying sodium silicate-based silica gel in an aqueous solution of Ca(OH)2. Silica gels with less than 1 mm in size with different pH values were treated in Ca(OH)2 solution at concentrations ranging from 2 to 20 g/L and aged at 25, 60, and 90°C for 40 min. The BET surface area of the silica gel decreased while its pore size increased considerably after modification in Ca(OH)2 solution. The pH of 5% calcium-doped silica in water ranged from about 8.5 to 10, depending on the pH of silica gel, the aging temperature, and the concentration of the Ca(OH)2. When the concentration of the Ca(OH)2 solution was 20%, needle-like crystals of calcium silicate hydrate formed over the surface of silica gel.Item Dynamics of Kaolinite-Urea Nanocomposites via Coupled DMSO-Hydroxyaluminum Oligomeric Intermediates(Hindawi Publishing Corporation, 2015) Ibahati, Sempeho S.; Kim, Hee T.; Mubofu, Egid B.; Pogrebnoi, Alexander; Shao, Godlisten N.; Hilonga, AskwarKaolinite-urea nanocomposites were prepared via intercalation reactions in an attempt to investigate the dynamic nature of kaolinite morphology for advanced applications in controlled release systems (CRS). Characterization was done using SEM-EDX, XRF, ATR-FTIR, XRD, and DT/DTG; Andreasen pipette sedimentation technique was used to determine the grain size distribution of the raw kaolinite. The X-ray diffraction pattern revealed the existence of an FCC Bravais lattice where the intercalation ratios attained were 51.2%, 32.4%, 7.0%, and 38.4% for hydroxyaluminum oligomeric intercalated kaolinite, substituted urea intercalated kaolinite, calcined DMSO intercalated kaolinite, and hydroxyaluminum reintercalated kaolinite, respectively, along with their respective crystallite sizes of 33.51–31.73 nm, 41.92–39.69 nm, 22.31–21.13 nm, and 41.86–39.63 nm. The outcomes demonstrated that the employed intercalation routes require improvements as the intercalation reactions were in average only ≈32.3%. The observations unveiled that it is possible to manipulate kaolinite structure into various morphologies including dense-tightly packed overlapping euhedral pseudo hexagonal platelets, stacked vermiform morphologies, postulated forms, and unique patterns exhibiting self-assembled curled glomeruli-like morphologies. Such a diversity of kaolinite morphologies expedites its advanced applications in the controlled release systems (CRS) such as drug delivery systems and controlled release fertilizers (CRFs).Item 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 TaiktWe 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.Item 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, HTThe 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.Item Encapsulated Urea-Kaolinite Nanocomposite for Controlled Release Fertilizer Formulations(Hindawi Publishing Corporation,, 2015-05-20) Sempeho, SI; Kim, HT; Mubofu, Egid; Pogrebnoi, Alexander; Shao, Godlisten N.; Hilonga, AskwarUrea controlled release fertilizer (CRF) was prepared via kaolinite intercalation followed by gum arabic encapsulation in an attempt to reduce its severe losses associated with dissolution, hydrolysis, and diffusion. Following the beneficiation, the nonkaolinite fraction decreased from 39.58% to 0.36% whereas the kaolinite fraction increased from 60.42% to 99.64%. The X-ray diffractions showed that kaolinite was a major phase with FCC Bravais crystal lattice with particle sizes ranging between 14.6nm and 92.5 nm. Theparticle size varied with intercalation ratioswithmethanol intercalated kaolinite >DMSO-kaolinite > urea-kaolinite (KPDMU). Following intercalation, SEM analysis revealed a change of order from thick compact overlapping euhedral pseudohexagonal platelets to irregular booklets which later transformed to vermiform morphology and dispersed euhedral pseudohexagonal platelets. Besides, dispersed euhedral pseudohexagonal platelets were seen to coexist with blocky-vermicular booklets. In addition, a unique brain-form agglomeration which transformed into roundish particles mart was observed after encapsulation. The nanocomposites decomposed between 48 and 600∘C. Release profiles showed that 100% of urea was released in 97 hours from KPDMU while 87% was released in 150 hours from the encapsulated nanocomposite.The findings established that it is possible to use Pugu kaolinite and gum arabic biopolymer to prepare urea CRF formulations.Item 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, HTThe 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.Item 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 TaikThe 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.Item Esterification of oleic acid by Heteropolyacid/ TiO2-SiO2 catalysts synthesized from less expensive precursors(Wiley, 2015-03-11) Sheik, R.; Shao, Godlisten N.; Kim, HeetaikA series of 12-tungstophosphoric acid [HPW, H3PW12O40 (HPW)] catalysts supported on mesoporous titania– silica composite (TSC) were prepared by impregnation method. Primarily, TSC with mesostructure was successfully prepared by a modified sol–gel process using a less expensive silica precursor (sodium silicate) and titanium oxychloride as a titania source. In order to develop catalysts with various properties, the HPW loading over mesoporous TSC was controlled between 5 and 50wt%. The surface morphology and structural properties of the prepared catalysts were characterized using N2 gas physisorption analysis, Fourier transform infrared spectroscopy, X-ray diffraction, ultraviolet spectroscopy, transmission electron microscopy, and scanning electron microscopy analysis. The X-ray diffraction and ultraviolet spectroscopy results were useful in determining the HPW dispersion on the support material. The catalytic activities of the samples were tested in liquid phase esterification of oleic acid with methanol. The results suggested that HPW dispersion on the support material was essential for the stability and performance of the catalysts during the esterification reaction. Even though the activity of the synthesized catalysts increased with increasing HPW loading, the homogeneity decreased in the samples with higher HPW content (30–50wt%). The 20%HPW/TSC sample was found to be an active and catalytically stable catalyst, which was successfully regenerated and recycled for three consecutive runs.Item Facile, Single-pot preparation of nanoporous SiO2 particles (carrier) with AgNPs at core and crust for controlled disinfectant release(Journal of Saudi Chemical Society, Elsevier B.V., 2019-03-11) Haider, M. Salman; Shao, Godlisten N.; Ahmad, Ahmad; Imran, S. Muhammad; Abbas, Nadir; Abbas, Ghulam; Hussein, Manwar; Kim, Hee TaikThis study demonstrates a novel, facile and one-pot approach to synthesize silica nanoparticles with silver at core and crust (SiNP-AgCC). A modified Stöber method was used to make SiNP-AgCC. A significant reduction in the size of SiO2 nanoparticles was seen, with 2–5 nm AgNPs being uniformly distributed on the surface and 10–20 nm AgNPs in the center. A typical mesoporous SiO2 particle (SiNP) produced using the Stöber method was transformed to nanoporous SiO2 by this modified Stöber method. Nanoporous SiO2 particles with silver in the center are advantageous for slow and consistent Ag+ release, which was confirmed by Ag+ ion release test. Antibacterial activities of the samples were tested to evaluate the disinfection performance of the samples on gram-negative bacteria (Escherichia coli) using disk diffusion and the LB-agar method. SiNP-AgCC showed prolonged silver release for more than 20 days and improved antibacterial properties even after five days of incubation.Item A Gentle Method to Graft Thiol-Functional Groups onto Silica Gel for Adsorption of Silver Ions and Immobilization of Silver Nanoparticles(2012-10-22) Quang, Dang Viet; Lee, Jae Eun; Kim, Jong-gil; Kim, You Na; Shao, Godlisten N.; Kim, Hee TaikThiol-functionalized silica that has been used to remove heavymetal from an aqueous solution and supportmetallic nanoparticles is usually synthesized by reflux in an organic solvent containing 3-mercaptopropyltrimethoxysilane (MPTMS). In this paper, we report a gentle method for grafting thiol-functional groups onto silica gel by an aging process that does not require mixing and refluxing in an organic solvent. Silica gel was synthesized by a sol–gel method from H2SO4 (40%) and sodium silicate, which was crushed into beads with sizes ranging from 180 to 450 μm. Silica beads (50 g) were mixed with 75 mL of a functionalization solution consisting of MPTMS, H2O, and C2H5OH and aged at 50 °C for 36 h in a box dryer. The success of the functionalization process was confirmed by FT-IR, BET, SEM and elemental analyses. The functionalization solution was percolated into pores and thiolfunctional groups were grafted onto the surface and pore walls of the silica beads. The ability of these functionalized silica beads to adsorb silver ionswas determined by the Langmuir isotherm equationwith amaximumadsorption of 75.8 mg/g. Silver nanoparticles with sizes ranging from 2 to 6 nmformed by chemical reductionwere located inside the pores and on the surfaces.Item https://www.sciencedirect.com/science/article/abs/pii/S092633731500346X(Wiley, 2016) Imran, S.M; Shao, Godlisten N.; Kim, HeetaikWe 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 devicesItem Inexpensive sol-gel synthesis of multiwalled carbon nanotube-TiO2 hybrids for high performance antibacterial materials(Materials Science and Engineering: C, Elsevier, 2016-11-01) Abbas, Nadir; Shao, Godlisten N.; Kim, HeetaikThis study reports an inexpensive sol-gel method to synthesize TiO2-CNT hybrid materials. Synthesized TiO2-CNT materials show strong antibacterial activity in the absence of light. Cheap TiO2 source TiOCl2 is used during synthesis in the absence of high temperatures, high pressures and organic solvents. TiO2-CNT materials with 0, 2, 5, 10, 15 and 20 wt% of CNT were synthesized and compared for antibacterial activity, surface area, porosity, crystalline structure, chemical state, and HaCaT cell proliferation. The antibacterial strength of hybrid materials increased significantly with the increase in CNT loading amount, and the TiO2-CNT samples with a CNT loading of 10 wt% or more nearly removed all of the E.coli bacteria. HaCaT cell proliferation studies of synthesized hybrid materials illustrated that prepared TiO2-CNT systems exhibit minimum cytotoxicity. The characteristics of prepared materials were analyzed by means of XRD, FTIR, Raman spectroscopy, XPS, TEM, and nitrogen gas physisorption studies, compared and discussedItem Inexpensive synthesis of a high-performance Fe3O4-SiO2-TiO2 photocatalyst: Magnetic recovery and reuse(Springer, 2016) Abbas, Nadir; Shao, Godlisten N.; Kim, HeetaikA sol-gel technique has been developed for the synthesis of a magnetite-silica-titania (Fe3O4-SiO2-TiO2) tertiary nanocomposite with improved photocatalytic properties based on the use of inexpensive titania and silica precursors. The exceptional photocatalytic activity of the resulting materials was demonstrated by using them to photocatalyze the degradation of methylene blue solution. The best formulation achieved 98% methylene blue degradation. An interesting feature of the present work was the ability to magnetically separate and reuse the catalyst. The efficiency of the catalyst remained high during two reuses. The synthesized nanomaterials were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), Fourier transform infrared (FTIR) spectroscopy, ultra-violet-visible spectroscopy, diffuse reflectance spectroscopy, and thermogravimetric analysis. XRD analysis revealed the formation of multicrystalline systems of cubic magnetite and anatase titania crystals. SEM and TEM characterization revealed well-developed and homo-geneously dispersed particles of size less than 15 nm. FTIR spectra confirmed the chemical interaction of titania and silica. It was further noticed that the optical properties of the prepared materials were dependent on the relative contents of their constituent metal oxides.Item Influence of titania content on the mesostructure of titania–silica composites and their photocatalytic activity(Powder Technology, 2012-08-28) Shao, Godlisten N.; Hilonga, Askwar; Jeon, Sun Jeong; Lee, Jae Eun; Elineema, Gideon; Quang, Dang Viet; Kim, Jong-Kil; Kim, Hee TaikTitania–silica composites (TSC) with various Ti/Si ratios were synthesized via sol–gel process using less expensive precursors; sodium silicate solution as a silica source and titanium oxychloride as a titania source. The influence of varying Ti content in the composites was examined by FTIR, SEM, TEM, DTA/TGA, N2 physisorption studies, XRF and XRD. The BET surface area of the raw materials increased with increasing Ti/Si ratio up to 2.9 (461 m2/g) but further increase of Ti content beyond that ratio yielded compositeswith decreased surface area. The effect of aging evaluated in the samplewith Ti/Si=2.9 revealed that aging the composite for 2 h yields titania–silica powderwith the highest surface area (461 m2/g). The FTIR analysis displayed the presence of a vibration band at 945 cm−1, assignable to hetero linkage of the Si–O–Ti depicting the incorporation of TiO2 into SiO2 to form a composite.Moreover, photodegradation of methyl orange (MO) by the samples calcined at 800 °C showed that the TSC-5-800 (Ti/Si=5.6) exhibited the highest maximum photocatalytic activity of all the composites.Item Investigation of the influence of vanadium, iron and nickel dopants on the morphology, and crystal structure and photocatalytic properties of titanium dioxide based nanopowders(Elsevier, 2016) Shao, Godlisten N.; Haider, M.S; Kim, HeetaikPhotoactive V, Fe and Ni doped TiO2 (M-TiO2) nanopowders were synthesized by a modified two-step sol-gel process in the absence of additives. Titanium oxychloride, which is a rarely-used TiO2 precursor was used to yield M-TiO2 photocatalysts with preferential photochemical performance in the presence of natural solar irradiation. The obtained samples were calcined at different calcination temperatures ranging from 450 to 800 °C to evaluate the influence of the sintering on the physicochemical properties. The properties of the obtained samples were examined by XRF, XRD, Raman spectroscopy, UV–visible DRS, XPS, nitrogen gas physisorption studies, SEM-EDAX and HRTEM analyses. Structural characterization of the samples revealed the incorporation of these transition metal element into TiO2. It was also depicted that the morphology, crystal structure, optical and photochemical properties of the obtained samples were largely dependent on the calcination temperature and the type of dopant used during the preparation process. The photochemical performance of the samples was investigated in the photodegradation of methylene blue in the presence of natural sunlight. The experimental results indicated that the VT600 sample possessed the highest activity due to its superior properties. This study provides a systematic preparation and selection of the precursor, dopant and calcination temperature that are suitable for the formation of TiO2-based heterogeneous photocatalysts with appealing morphology, crystal structure, optical and photochemical properties for myriad of applications.Item Mesoporous Electrodes for Supercapacitors(CRC Press (Taylor & Francis Group), 2019-12) Shao, Godlisten N.; Kibona, Talam EnockMesoporous electrodes with desirable properties for supercapacitors are very fascinating and their ubiquitous attraction to scientists and engineers is indisputably incessant. Conversely, supercapacitors are highly researched energy storage materials due to their promising potentials to solve the energy storage demands for high-performance energy applications. Investigation of materials with suitable properties for mesoporous electrodes for supercapacitors is mainly carried out to improve their power density and energy density. This chapter highlights the recent investigations and advances toward the development of mesoporous electrodes for supercapacitors.Item Microstructure and Materials Characterization of Sol-Gel Synthesized ZrO2 Systems(Tanzania Journal of Science, 2019) Park, Sungsoo; Shao, Godlisten N.The roles of pH and thermal treatment on the microstructures of sol-gel synthesized mesoporous ZrO2 systems have been investigated. In order to control the crystal structure and particle size of the final products, the pH values of the reaction mixtures were controlled between 5 and 12 followed by calcination at temperatures ranging from 450 to 1000 °C. The microstructures of the zirconia systems were then examined by XRD, TEM, TGA, UV-visible DRS and nitrogen physisorption study analyses. It was found that pH values and calcination temperatures have significant influence on the crystallization temperature, phase transformation and particle size of the ZrO2 systems. Pure tetragonal and monoclinic ZrO2 crystals or a mixture of tetragonal and monoclinic ZrO2 crystals with controlled particle size could readily be yielded by maintaining the pH values and the calcination temperatures. This study therefore elucidates a facile approach to yielding sol-gel synthesized metal oxide nanoparticles with controlled phase and particle size.