S M IMRAN - Academia.edu (original) (raw)
Papers by S M IMRAN
Materials science & engineering. C, Materials for biological applications, 2016
The present study reports the antibacterial disinfection properties of a series of silver nanopar... more 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 form AgNPs-APES. The properties of the obtained membrane were examined by FT-IR, XPS, XRD, TGA, ICP-OES and SEM-EDAX analyses. These structural characterizations revealed that AgNPs ranging from 5 to 40nm 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 1cm×3cm 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% o...
Applied Surface Science, 2015
ABSTRACT The development of visible-light effective TiO2 photocatalysts allows low cost degradati... more ABSTRACT The development of visible-light effective TiO2 photocatalysts 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 ammonium solution 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.
Solid State Sciences, 2015
The present study demonstrates a novel, systematic and application route synthesis approach to de... more The present study demonstrates a novel, systematic and application route synthesis approach to develop size-property relationship and control the growth of silver nanoparticles (AgNPs) embedded on reduced graphene oxide (rGO). A sequential repetitive chemical reduction technique to observe the growth of silver nanoparticles (AgNPs) attached to rGO, was performed on a single solution of graphene oxide (GO) and silver nitrate solution (7 runs, R1eR7) in order to manipulate the growth and size of the AgNPs. The physicalechemical properties of the samples were examined by RAMAN, XPS, XRD, SEM-EDAX, and HRTEM analyses. It was confirmed that AgNPs with diameter varying from 4 nm in first run (R1) to 50 nm in seventh run (R7) can be obtained using this technique. A major correlation between particle size and activities was also observed. Antibacterial activities of the samples were carried out to investigate the disinfection performance of the samples on the Gram negative bacteria (Escherichia coli). It was suggested that the sample obtained in the third run (R3) exhibited the highest antibacterial activity as compared to other samples, toward disinfection of bacteria due to its superior properties. This study provides a unique and novel application route to synthesize and control size of AgNPs embedded on graphene for various applications.
Advances in gerontology = Uspekhi gerontologii / Rossiĭskai͡a akademii͡a nauk, Gerontologicheskoe obshchestvo, 2012
In article, analysis has been carried out on the influence of recanalization of chronic total occ... more In article, analysis has been carried out on the influence of recanalization of chronic total occlusion of left anterior descending artery on the course of heart failure in elderly patients who had damage to a single artery and viable myocardium. Recanalization of chronic occlusion of left anterior descending artery together with conservative therapy in elderly patients improves the clinical course of heart failure. A more significant improvement seen in patients with chronic occlusion of left anterior descending artery without history of myocardial infarction.
Vision: The Journal of Business Perspective, 2014
Applied Surface Science, 2015
ABSTRACT Supporting TiO2 on different materials is a potential strategy to improve the photochemi... more ABSTRACT 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.
Incorporation of metal nanoparticles in Polyaniline composites could effectively improve its opti... more Incorporation of metal nanoparticles in Polyaniline composites could effectively improve its optical, thermal and electrical properties and making it an ideal for the use in semiconductor industry. In this study Ag nanoparticles were uniformly dispersed ultrasonically in the solution of polyaniline emeraldine base (PANIEB) and isopropyl alcohol. PANIEB used in this experiment were doped with polymer of methacrylic acid ester and vinyl verstate. The results about the morphological, optical and electrical properties of Ag-PANIEB with IPA colloid as a function of different concentration of Ag nanoparticles (Such as 25%, 50%, 100% by weight) were presented and discussed.
2013 Conference on Lasers and Electro-Optics Pacific Rim (CLEOPR), 2013
Journal of Applied Polymer Science, 2014
The present study demonstrates a modified in situ emulsion polymerization (EP) approach convenien... more 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 m 21 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.
2014 International Conference on Informatics, Electronics & Vision (ICIEV), 2014
ABSTRACT In brain-computer interface (BCI) applications, classification of electroencephalogram (... more ABSTRACT In brain-computer interface (BCI) applications, classification of electroencephalogram (EEG) data for different motor imagery (MI) tasks is a major concern. In this paper, an efficient MI task classification scheme is proposed based on autoregressive (AR) modeling of the EEG signal. From given EEG recording, after some basic preprocessing operations, the processed EEG data of each channel is windowed into several frames and AR parameters are extracted using least-square Yule-Walker method. Considering the reflection coefficients from the autoregressive modeling, a set of features is extracted from the average of the coefficients of the specified frames. In order to reduce the dimension of the proposed feature matrix, principal component analysis (PCA) is employed. For the purpose of classification, train and test sets are formed based on leave one out cross validation and then linear discriminant analysis (LDA) based classifier is used. Simulation is carried out on publicly available MI dataset IVa of BCI Competition-III and a very satisfactory performance is obtained in classifying the MI data in two classes, namely right hand and right foot MI tasks. Proposed classification scheme not only offers significant reduction in feature dimensionality but also provides satisfactory classification accuracy.
2012 International Conference on Emerging Technologies, 2012
Powder Technology, 2014
ABSTRACT Photoactive metal oxide systems capable of reducing non-biodegradable pollutants are hig... more ABSTRACT Photoactive metal 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-gel method 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 degrees C). Comparisons of the activities of the samples toward decolorization of methylene blue indicated that the photocatalytic efficiencies of the composites with Zr/ri <= 2.2 were superior to that of pure TiO2.
Microporous and Mesoporous Materials, 2013
The textural properties of TiO 2 -SiO 2 composites (TSCs) were successively enhanced using three ... more The textural properties of TiO 2 -SiO 2 composites (TSCs) were successively enhanced using three approaches; (1) washing the hydrogels with different solvents, (2) using surfactant and forming the TiO 2 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 TiO 2 sol in ethanol medium prior to reaction with silica source. The TSC powders were examined by XRD, N 2 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 m 2 /g) while porosities of the composites obtained using stearic acid as a surfactant (TSCSA, 0.96 cm 3 /g) and ethanol as a medium to form the TiO 2 sol (TSCES, 1.85 cm 3 /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.
IEEE Journal of Quantum Electronics, 2000
IEEE Journal of Quantum Electronics, 2000
Semiconductor lasers tend to suffer from the optical feedback (OFB) noise caused by the reflectio... more Semiconductor lasers tend to suffer from the optical feedback (OFB) noise caused by the reflection of the output light at the surface of the optical disc or the optical fiber. Superposition of high frequency (HF) current is used as a technique to suppress the OFB noise. However, this is not effective when the frequency of the HF current coincides with a rational number of the round trip time for the OFB. This paper shows numerical simulations on the phenomena of the OFB noise, its suppression by the superposition of HF current and conditions at which the HF current is unable to suppress the noise. The model used here is based on multimode rate equations that include nonlinear gain, Langevin noise sources, the OFB, and the HF superposition. Generating mechanism of the OFB noise and its suppression are explained with approximated but analytical equations. Excellent correspondence between experimental data and simulation is also demonstrated.
Chemical Engineering Journal, 2013
Hydrophobic TiO 2 -SiO 2 composite aerogels are synthesized by the solgel method. Sodium silicate... more Hydrophobic TiO 2 -SiO 2 composite aerogels are synthesized by the solgel method. Sodium silicate solution and TiOCl 2 are used as sources to form photocatalysts. The surface area and pore volume of the sample calcined at 400°C are the highest. The as-synthesized sample exhibits the highest activity of all synthesized samples.
Materials science & engineering. C, Materials for biological applications, 2016
The present study reports the antibacterial disinfection properties of a series of silver nanopar... more 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 form AgNPs-APES. The properties of the obtained membrane were examined by FT-IR, XPS, XRD, TGA, ICP-OES and SEM-EDAX analyses. These structural characterizations revealed that AgNPs ranging from 5 to 40nm 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 1cm×3cm 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% o...
Applied Surface Science, 2015
ABSTRACT The development of visible-light effective TiO2 photocatalysts allows low cost degradati... more ABSTRACT The development of visible-light effective TiO2 photocatalysts 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 ammonium solution 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.
Solid State Sciences, 2015
The present study demonstrates a novel, systematic and application route synthesis approach to de... more The present study demonstrates a novel, systematic and application route synthesis approach to develop size-property relationship and control the growth of silver nanoparticles (AgNPs) embedded on reduced graphene oxide (rGO). A sequential repetitive chemical reduction technique to observe the growth of silver nanoparticles (AgNPs) attached to rGO, was performed on a single solution of graphene oxide (GO) and silver nitrate solution (7 runs, R1eR7) in order to manipulate the growth and size of the AgNPs. The physicalechemical properties of the samples were examined by RAMAN, XPS, XRD, SEM-EDAX, and HRTEM analyses. It was confirmed that AgNPs with diameter varying from 4 nm in first run (R1) to 50 nm in seventh run (R7) can be obtained using this technique. A major correlation between particle size and activities was also observed. Antibacterial activities of the samples were carried out to investigate the disinfection performance of the samples on the Gram negative bacteria (Escherichia coli). It was suggested that the sample obtained in the third run (R3) exhibited the highest antibacterial activity as compared to other samples, toward disinfection of bacteria due to its superior properties. This study provides a unique and novel application route to synthesize and control size of AgNPs embedded on graphene for various applications.
Advances in gerontology = Uspekhi gerontologii / Rossiĭskai͡a akademii͡a nauk, Gerontologicheskoe obshchestvo, 2012
In article, analysis has been carried out on the influence of recanalization of chronic total occ... more In article, analysis has been carried out on the influence of recanalization of chronic total occlusion of left anterior descending artery on the course of heart failure in elderly patients who had damage to a single artery and viable myocardium. Recanalization of chronic occlusion of left anterior descending artery together with conservative therapy in elderly patients improves the clinical course of heart failure. A more significant improvement seen in patients with chronic occlusion of left anterior descending artery without history of myocardial infarction.
Vision: The Journal of Business Perspective, 2014
Applied Surface Science, 2015
ABSTRACT Supporting TiO2 on different materials is a potential strategy to improve the photochemi... more ABSTRACT 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.
Incorporation of metal nanoparticles in Polyaniline composites could effectively improve its opti... more Incorporation of metal nanoparticles in Polyaniline composites could effectively improve its optical, thermal and electrical properties and making it an ideal for the use in semiconductor industry. In this study Ag nanoparticles were uniformly dispersed ultrasonically in the solution of polyaniline emeraldine base (PANIEB) and isopropyl alcohol. PANIEB used in this experiment were doped with polymer of methacrylic acid ester and vinyl verstate. The results about the morphological, optical and electrical properties of Ag-PANIEB with IPA colloid as a function of different concentration of Ag nanoparticles (Such as 25%, 50%, 100% by weight) were presented and discussed.
2013 Conference on Lasers and Electro-Optics Pacific Rim (CLEOPR), 2013
Journal of Applied Polymer Science, 2014
The present study demonstrates a modified in situ emulsion polymerization (EP) approach convenien... more 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 m 21 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.
2014 International Conference on Informatics, Electronics & Vision (ICIEV), 2014
ABSTRACT In brain-computer interface (BCI) applications, classification of electroencephalogram (... more ABSTRACT In brain-computer interface (BCI) applications, classification of electroencephalogram (EEG) data for different motor imagery (MI) tasks is a major concern. In this paper, an efficient MI task classification scheme is proposed based on autoregressive (AR) modeling of the EEG signal. From given EEG recording, after some basic preprocessing operations, the processed EEG data of each channel is windowed into several frames and AR parameters are extracted using least-square Yule-Walker method. Considering the reflection coefficients from the autoregressive modeling, a set of features is extracted from the average of the coefficients of the specified frames. In order to reduce the dimension of the proposed feature matrix, principal component analysis (PCA) is employed. For the purpose of classification, train and test sets are formed based on leave one out cross validation and then linear discriminant analysis (LDA) based classifier is used. Simulation is carried out on publicly available MI dataset IVa of BCI Competition-III and a very satisfactory performance is obtained in classifying the MI data in two classes, namely right hand and right foot MI tasks. Proposed classification scheme not only offers significant reduction in feature dimensionality but also provides satisfactory classification accuracy.
2012 International Conference on Emerging Technologies, 2012
Powder Technology, 2014
ABSTRACT Photoactive metal oxide systems capable of reducing non-biodegradable pollutants are hig... more ABSTRACT Photoactive metal 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-gel method 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 degrees C). Comparisons of the activities of the samples toward decolorization of methylene blue indicated that the photocatalytic efficiencies of the composites with Zr/ri <= 2.2 were superior to that of pure TiO2.
Microporous and Mesoporous Materials, 2013
The textural properties of TiO 2 -SiO 2 composites (TSCs) were successively enhanced using three ... more The textural properties of TiO 2 -SiO 2 composites (TSCs) were successively enhanced using three approaches; (1) washing the hydrogels with different solvents, (2) using surfactant and forming the TiO 2 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 TiO 2 sol in ethanol medium prior to reaction with silica source. The TSC powders were examined by XRD, N 2 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 m 2 /g) while porosities of the composites obtained using stearic acid as a surfactant (TSCSA, 0.96 cm 3 /g) and ethanol as a medium to form the TiO 2 sol (TSCES, 1.85 cm 3 /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.
IEEE Journal of Quantum Electronics, 2000
IEEE Journal of Quantum Electronics, 2000
Semiconductor lasers tend to suffer from the optical feedback (OFB) noise caused by the reflectio... more Semiconductor lasers tend to suffer from the optical feedback (OFB) noise caused by the reflection of the output light at the surface of the optical disc or the optical fiber. Superposition of high frequency (HF) current is used as a technique to suppress the OFB noise. However, this is not effective when the frequency of the HF current coincides with a rational number of the round trip time for the OFB. This paper shows numerical simulations on the phenomena of the OFB noise, its suppression by the superposition of HF current and conditions at which the HF current is unable to suppress the noise. The model used here is based on multimode rate equations that include nonlinear gain, Langevin noise sources, the OFB, and the HF superposition. Generating mechanism of the OFB noise and its suppression are explained with approximated but analytical equations. Excellent correspondence between experimental data and simulation is also demonstrated.
Chemical Engineering Journal, 2013
Hydrophobic TiO 2 -SiO 2 composite aerogels are synthesized by the solgel method. Sodium silicate... more Hydrophobic TiO 2 -SiO 2 composite aerogels are synthesized by the solgel method. Sodium silicate solution and TiOCl 2 are used as sources to form photocatalysts. The surface area and pore volume of the sample calcined at 400°C are the highest. The as-synthesized sample exhibits the highest activity of all synthesized samples.