Excellence in Research and Innovation for Humanity

International Science Index

Commenced in January 1999 Frequency: Monthly Edition: International Abstract Count: 48522

Chemical and Molecular Engineering

1985
83956
Cloning, Expression and N-Terminal Pegylation of Human Interferon Alpha-2b Analogs and Their Cytotoxic Evaluation against Cancer Cell Lines
Abstract:
In the current research, three recombinant human interferon alpha-2b proteins (two modified and one normal form) were produced and Pegylated with an aim to produce more effective drugs against viral infections and cancers. The modified recombinant human interferon alpha-2b proteins were produced by site-directed modifications of interferon alpha 2b gene, targeting the amino acids at positions ‘R23’ and ‘H34’. The resulting chemically modified and unmodified forms of human interferon alpha 2b were conjugated with methoxy-polyethylene glycol propanealdehyde (400 KDa) and methoxy-polyethylene glycol succinimidyl succinate (400 KDa). Pegylation of normal and modified forms of Interferon alpha-2b prolong their release time and enhance their efficacy. The conjugation of PEG with modified and unmodified human interferon alpha 2b protein drugs was also characterized with 1H-NMR, HPLC, and SDS-PAGE. Antiproliferative assays of modified and unmodified forms of drugs were performed in cell based bioassays using MDBK cell lines. The results indicated that experimentally produced recombinant human interferon alpha-2b proteins were biologically active and resulted in significant inhibition of cell growth.
Digital Article Identifier (DAI):
1984
83793
Highly Efficient and Easily Recoverable Bio-Polymer Supported Pd(II) Catalyst for Synthesis of Biaryls Compounds
Authors:
Abstract:
Bio-polymers as a support material play an important role in catalytic systems due to their green nature, low cost and high thermal stability. Polysaccharides like cellulose, chitosan, and starch have been acknowledged as versatile support materials for catalysts systems. Especially, chitosan is very important support material due to its superior properties such as good chemical stability, high surface area, excellent chemical stability, easy accessibility and low cost. In this study, novel chitosan Schiff base supported palladium (II) catalyst was fabricated, and its chemical structure was characterized with Fourier Transform Infrared (FT-IR), Scanning Electron Microscopy (SEM/EDX), X-ray Powder Diffraction (XRD), Thermal Analysis (TG-DTG), Inductively Coupled Plasma Atomic Emission Spectroscopy (ICP-OES) and magnetic moment techniques. Then, the catalytic efficiency of fabricated palladium catalyst was investigated in synthesis of biaryls compounds under microwave heating technique. The tests showed that catalyst gave remarkable reaction yields with very low amount of the catalyst. In addition, longevity of palladium catalyst was tested, and the test indicated that the catalyst could be reused seven runs without a significant loss of activity.
Digital Article Identifier (DAI):
1983
83792
Highly Selective, Thermally Stable and Eco- Friendly Pd(II) Catalyst: Production, Characterization and Application
Abstract:
Suzuki cross-coupling reaction is very influential method for synthesis of biphenyl compounds which are used cosmetics, medicine, pharmacology applications. However, Suzuki reactions require inert atmosphere, high temperature, organic solvent and use of excess amount of energy. To overcome these drawbacks, we developed new thermally stable and eco-friendly palladium (II) catalyst and characterization studies were performed with Fourier Transform Infrared (FT-IR), Scanning Electron Microscopy (SEM/EDX), X-ray Powder Diffraction (XRD), Thermal Analysis (TG-DTG), Inductively Coupled Plasma Atomic Emission Spectroscopy (ICP-OES). In addition, to reduce the use of excess energy and organic solvent, catalytic performance of catalyst was studied using microwave irradiations with very short reaction time. Catalytic tests showed that prepared eco-friendly catalyst had highly selective and excellent catalytic performance for synthesis of biphenyl compounds. In addition, reusability of catalyst was tested, and the catalyst could be reused 8 runs without any significant loss of activity.
Digital Article Identifier (DAI):
1982
83641
Self-Templated Formation of Carbon Doped Yolk-Shell ZnFe₂O₄ Nanostructures for Enhanced Photocatalysis Degradation of Gaseous O-Dichlorobenzene
Abstract:
Volatile organic compounds (VOCs) as an important class of hazardous air pollutants, mainly generated during the incineration processes of municipal wastes, have attracted increasing attention. Compared with traditional techniques for VOCs degradation, photocatalysis oxidation technique which utilize the absorption of photons by the semiconductor to provoke electron-hole pairs to consequently induce photocatalytic reactions at its surface for pollutant treatment is a much more considerable choice because of its environmentally friendly, high stability, low cost and high efficiency. However, some issues still need to be solved such as low quantum efficiency due to rapid recombination of photo-generated charge carriers and unsatisfactory utilization efficiency of solar energy. Very recently, numerous visible-light-responsive photocatalysts have been developed. Spinel-type oxides, with a general formula of AB₂O₄, are promising photocatalysts due to their visible-light activity, excellent chemical and thermal stability, environmental friendliness and flexible composition. ZnFe₂O₄, as a more promising spinel oxide, has attracted considerable interest in the photocatalysis, solar cells, water splitting and gas sensors over the past years. Despite these substantial virtues, they could not be directly used as an efficient photocatalyst by the high recombination rate of photogenerated e⁻/h⁺ pairs, leading to poor quantum efficiency and low photocatalytic activity under visible-light illumination. Furthermore, the poor ability to capture sunlight presumably caused by their low surface area and weak light scattering effect could also become the major obstacle for their practical applications. Recently, yolk-shell structure photocatalysts have been developed to increase the light-harvesting efficiency due to multi-scattering of light. It could also enhance the photocatalysis performance by providing much more active sites, high specific area and shortened mass transfer path. Althrough many strategies have been developed to obtain the complexed structure such as template methods, they are usually time-consuming and tedious in preparing the templates and post-etching treatment. Thus, no-templated or self-templated methods have been popular in recent years on the fabrication of these complex structures. Considering the rapid recombination of photo-generated charge carriers,it has been reported that carbon modified spinel oxides could accelerate electron transfer from the inside of photocatalyst to interface by the unique properties of carbon as electron reservoir. The carbon doping could also induce several occupied states in the gap and favor the formation of oxygen vacancies, which can enhance the light absorption and exhibit a higher visible-light catalytic activity for degradation of pollutants. However, usually multiple and complexed processes needed in preparation, and a low specific surface area was usually unsatisfied from the traditional synthetic ways. In this work, carbon doped yolk-shell ZnFe₂O₄ nanostructures were efficiently prepared by a facile self-templated method and the carbon could be doped in-situ using dopamine as carbon source in the solvothermal process. The interiors between core and shell could be modulated by controlling the heating rate in the calcination process. In-situ Fourier Transform Infrared Spectroscopy (FTIR) and electron paramagnetic resonance (EPR) were conducted to characterize the towards photocatalytic degradation of gaseous 1, 2-dichlorobenzene (o-DCB) under visible-light irradiation and investigate the main active radical oxygen species involved in the process.
Digital Article Identifier (DAI):
1981
83482
Nanocomposite Metal Material: Study of Antimicrobial and Catalytic Properties
Abstract:
The aim of this study was to obtain antimicrobial material based on thin zirconium dioxide coatings on structured reactors doped with metal nanoparticles using the sonochemical sol-gel method. As a result, dense, uniform zirconium dioxide films were obtained on the kanthal sheets which can be used as support materials in antimicrobial converters with sophisticated shapes. The material was characterised by physicochemical methods, such as AFM, SEM, EDX, XRF, XRD, XPS and in situ Raman and DRIFT spectroscopy. In terms of antimicrobial activity, the material was tested by ATP/AMP method using model microbes isolated from the real systems. The results show that the material can be potentially used in the market as a good candidate for active package and as active bulkheads of climatic systems. The mechanical tests showed that the developed method is an efficient way to obtain durable converters with high antimicrobial activity against fungi and bacteria.
Digital Article Identifier (DAI):
1980
83478
Sonochemically Prepared Non-Noble Metal Oxide Catalysts for Methane Catalytic Combustion
Abstract:
The aim of this study was to obtain highly active catalysts based on non-noble metal oxides supported on zirconia prepared via a sonochemical method. In this study, the influence of the stabilizers addition during the preparation step was checked. The final catalysts were characterized by using such characterization methods as X-ray Diffraction (XRD), nitrogen adsorption, X-ray fluorescence (XRF), scanning electron microscopy (SEM) equipped with energy dispersive X-ray spectrometer (EDS), transmission electron microscopy (TEM) and µRaman. The proposed preparation method allowed to obtain uniformly dispersed metal-oxide nanoparticles at the support’s surface. The catalytic activity of prepared catalyst samples was measured in a methane combustion reaction. The activity of the catalysts prepared by the sonochemical method was considerably higher than their counterparts prepared by the incipient wetness method.
Digital Article Identifier (DAI):
1979
83344
Formulation of a Submicron Delivery System including a Platelet Lysate to Be Administered in Damaged Skin
Abstract:
The prevalence of people with chronic wounds has increased dramatically by many factors including smoking, obesity and chronic diseases, such as diabetes, that can slow the healing process and increase the risk of becoming chronic. Because of this situation, the improvement of chronic wound treatments is a necessity, which has led to the scientific community to focus on improving the effectiveness of current therapies and the development of new treatments. The wound formation is a physiological complex process, which is characterized by an inflammatory stage with the presence of proinflammatory cells that create a proteolytic microenvironment during the healing process, which includes the degradation of important growth factors and cytokines. This decrease of growth factors and cytokines provides an interesting strategy for wound healing if they are administered externally. The use of nanometric drug delivery systems, such as polymer nanoparticles (NP), also offers an interesting alternative around dermal systems. An interesting strategy would be to propose a formulation based on a thermosensitive hydrogel loaded with polymeric nanoparticles that allows the inclusion and application of a platelet lysate (PL) on damaged skin, with the aim of promoting wound healing. In this work, NP were prepared by a double emulsion-solvent evaporation technique, using polylactic-co-glycolic acid (PLGA) as biodegradable polymer. Firstly, an aqueous solution of PL was emulsified into a PLGA organic solution, previously prepared in dichloromethane (DCM). Then, this disperse system (W/O) was poured into a polyvinyl alcohol (PVA) solution to get the double emulsion (W/O/W), finally the DCM was evaporated by magnetic stirring resulting in the NP formation containing PL. Once the NP were obtained, these systems were characterized by morphology, particle size, Z-potential, encapsulation efficiency (%EE), physical stability, infrared spectrum, calorimetric studies (DSC) and in vitro release profile. The optimized nanoparticles were included in a thermosensitive gel formulation of Pluronic® F-127. The gel was prepared by the cold method at 4 °C and 20% of polymer concentration. Viscosity, sol-gel phase transition, time of no flow solid-gel at wound temperature, changes in particle size by temperature-effect using dynamic light scattering (DLS), occlusive effect, gel degradation, infrared spectrum and micellar point by DSC were evaluated in all gel formulations. PLGA NP of 267 ± 10.5 nm and Z-potential of -29.1 ± 1 mV were obtained. TEM micrographs verified the size of NP and evidenced their spherical shape. The %EE for the system was around 99%. Thermograms and in infrared spectra mark the presence of PL in NP. The systems did not show significant changes in the parameters mentioned above, during the stability studies. Regarding the gel formulation, the transition sol-gel occurred at 28 °C with a time of no flow solid-gel of 7 min at 33°C (common wound temperature). Calorimetric, DLS and infrared studies corroborated the physical properties of a thermosensitive gel, such as the micellar point. In conclusion, the thermosensitive gel described in this work, contains therapeutic amounts of PL and fulfills the technological properties to be used in damaged skin, with potential application in wound healing and tissue regeneration.
Digital Article Identifier (DAI):
1978
83178
Effect of Al on Glancing Angle Deposition Synthesized In₂O₃ Nanocolumn for Photodetector Application
Abstract:
Aluminium (Al) doped In2O3 (Indium Oxide) nanocolumn array was synthesized by glancing angle deposition (GLAD) technique on Si (n-type) substrate for photodetector application. The sample was characterized by scanning electron microscopy (SEM). The average diameter of the nanocolumn was calculated from the top view of the SEM image and found to be ∼80 nm. The length of the nanocolumn (~500 nm) was calculated from cross sectional SEM image and it shows that the nanocolumns are perpendicular to the substrate. The EDX analysis confirmed the presence of Al (Aluminium), In (Indium), O (Oxygen) elements in the samples. The XRD patterns of the Al-doped In2O3 nanocolumn show the presence of different phases of the Al doped In2O3 nanocolumn i.e. (222) and (622). Three different peaks were observed from the PL analysis of Al doped In2O3 nanocolumn at 365 nm, 415 nm and 435 nm respectively. The peak at PL emission at 365 nm can be attributed to the near band gap transition of In2O3 whereas the peaks at 415 nm and 435 nm can be attributed to the trap state emissions due to oxygen vacancies and oxygen–indium vacancy centre in Al doped In2O3 nanocolumn. The current-voltage (I–V) characteristics of the Al doped In2O3 nanocolumn based detector was measured through the Au Schottky contact. The devices were then examined under the halogen light (20 W) illumination for photocurrent measurement. The Al-doped In2O3 nanocolumn based optical detector showed high conductivity and low turn on voltage at 0.69 V under white light illumination. A maximum photoresponsivity of 82 A/W at 380 nm was observed for the device. The device shows a high internal gain of ~267 at UV region (380 nm) and ∼127 at visible region (760 nm). Also the rise time and fall time for the device at 650 nm is 0.15 and 0.16 sec respectively which makes it suitable for fast response detector.
Digital Article Identifier (DAI):
1977
83170
Sonochemically Prepared Zeolite Catalysts in the Reduction of NOx by NH3 in Lean Gas Conditions: Catalyst Characterisation and Activity Study
Abstract:
The issue of removal of nitrogen oxides (NOx) is still a current topic in the research. The emission of NOx by stationary and mobile sources as diesel engines, although regulated by low should continuously be minimalized. The nitrogen oxides have a negative impact on the environment, thus they may cause acid rain, photochemical smog and contribute to the ozone hole. As the main solution and the most efficient one, the application of ammonia-selective catalytic reduction process (NH3-SCR) to NOx elimination is used in the industry. Many zeolitic and other oxides systems have been used as catalysts in this reaction over the last years, and among them, most of the zeolitic materials have been prepared by the classical ion-exchange method. As results, this preparation manner leads to the development of highly active catalysts in deNOx process as e.g. the Cu-exchanged form of the SSZ-13 zeolite or Cu exchanged ZSM-5 . However, the searching for the alternatives is not done yet. Much research is still carrying out on the development of new (zeolitic) catalysts that will have highly desired parameters and the high activity in the removal of nitrogen oxides. The development of catalytic systems that will be active in deNOx process has to include several requirements, such as: the resistance of the catalyst’s surface to high temperatures and high selectively, especially to the N2. As the active phase in deNOx process mostly the two metals are used – copper and iron. The aim of this study was to provide the new synthesis route of iron substituted sonochemically prepared zeolite’s catalysts. The zeolites engaged in this study include zeolite Y, USY and MFI. The catalytic activity was established for deNOx SCR process in lean conditions. The activity of catalysts was compared for those prepared with the standard method and with ultrasound irritation. The properties of catalysts materials has been determined by micro-Raman spectroscopy, X-ray diffraction (XRD), scanning electron microscope (SEM), and UV/Visible diffuse reflectance spectroscopy (UV/Vis DRS). A s it was shown in the study both catalysts method leads to decreasing of the porosity and specific surface area of catalysts, however the differences has been found between the Fe-loading depending on used zeolite support. The iron substituted catalysts shown great activity in deNOx process with selectivity towards N2 reached almost 100%.
Digital Article Identifier (DAI):
1976
83104
Adsorption of Methylene Blue by Pectin from Durian (Durio zibethinus) Seeds
Abstract:
Methylene blue is a popular water-soluble dye that is used for dyeing a variety of substrates such as bacteria, wool, and silk. Methylene blue discharged into the aquatic environment will cause health problems for living things. Treatment method for industrial wastewater may be divided into three main categories: physical, chemical, and biological. Among them, adsorption technology is generally considered to be an effective method for quickly lowering the concentration of dissolved dyes in a wastewater. This has attracted considerable research into low-cost alternative adsorbents for adsorbing or removing coloring matter. In this research, pectin from durian seeds was utilized here to assess their ability for the removal of methylene blue. Adsorption parameters are contact time and dye concentration were examined in the batch adsorption processes. Pectin characterization was performed by FTIR spectrometry. Methylene blue concentration was determined by using UV-Vis spectrophotometer. FTIR results show that the samples showed the typical fingerprint in IR spectrogram. The adsorption result on 10 mL of 5 mg/L methylene blue solution achieved 95.12% when contact time 10 minutes and pectin 0.2 g.
Digital Article Identifier (DAI):
1975
82962
Simulation of Multistage Extraction Process of Co-Ni Separation Using Ionic Liquids
Abstract:
Ionic liquids offer excellent advantages over conventional solvents for industrial extraction of metals from aqueous solutions, where such extraction processes bring opportunities for recovery, reuse, and recycling of valuable resources and more sustainable production pathways. Recent research on the use of ionic liquids for extraction confirms their high selectivity and low volatility, but there is relatively little focus on how their properties can be best exploited in practice. This work addresses gaps in research on process modelling and simulation, to support development, design, and optimisation of these processes, focusing on the separation of the highly similar transition metals, cobalt, and nickel. The study exploits published experimental results, as well as new experimental results, relating to the separation of Co and Ni using trihexyl (tetradecyl) phosphonium chloride. This extraction agent is attractive because it is cheaper, more stable and less toxic than fluorinated hydrophobic ionic liquids. This process modelling work concerns selection and/or development of suitable models for the physical properties, distribution coefficients, for mass transfer phenomena, of the extractor unit and of the multi-stage extraction flowsheet. The distribution coefficient model for cobalt and HCl represents an anion exchange mechanism, supported by the literature and COSMO-RS calculations. Parameters of the distribution coefficient models are estimated by fitting the model to published experimental extraction equilibrium results. The mass transfer model applies Newman’s hard sphere model. Diffusion coefficients in the aqueous phase are obtained from the literature, while diffusion coefficients in the ionic liquid phase are fitted to dynamic experimental results. The mass transfer area is calculated from the surface to mean diameter of liquid droplets of the dispersed phase, estimated from the Weber number inside the extractor. New experiments measure the interfacial tension between the aqueous and ionic phases. The empirical models for predicting the density and viscosity of solutions under different metal loadings are also fitted to new experimental data. The extractor is modelled as a continuous stirred tank reactor with mass transfer between the two phases and perfect phase separation of the outlet flows. A multistage separation flowsheet simulation is set up to replicate a published experiment and compare model predictions with the experimental results. This simulation model is implemented in gPROMS software for dynamic process simulation. The results of single stage and multi-stage flowsheet simulations are shown to be in good agreement with the published experimental results. The estimated diffusion coefficient of cobalt in the ionic liquid phase is in reasonable agreement with published data for the diffusion coefficients of various metals in this ionic liquid. A sensitivity study with this simulation model demonstrates the usefulness of the models for process design. The simulation approach has potential to be extended to account for other metals, acids, and solvents for process development, design, and optimisation of extraction processes applying ionic liquids for metals separations, although a lack of experimental data is currently limiting the accuracy of models within the whole framework. Future work will focus on process development more generally and on extractive separation of rare earths using ionic liquids.
Digital Article Identifier (DAI):
1974
82939
Morphology and Flow Analysis of Buoyant Bubble Plumes
Abstract:
Buoyant plumes are encountered in many processes of environmental and engineering importance like wastewater treatment, petrochemical processing, destratification of lakes and reservoirs, mineral and froth floatation and in refining operations like secondary steel making process. Morphological characterization of bubble plumes is very important to design such kind of process reactor and to determine appropriate operating conditions. To study the plume morphology, plumes were generated experimentally in a water filled cylindrical plexiglass tank by injecting air from the bottom of the tank through a nozzle. Motion of these plumes was captured by high speed camera and the images were analyzed to obtain plume characteristics like bubble distribution in the plume, plume spreading etc. The velocity of liquid as well as individual bubbles in the plume was obtained by using particle image velocimetry and particle tracking velocimetry techniques. The variation of these plume characteristics along its height are measured. The effect of inlet gas flow rate and position of gas injecting nozzle on the plume properties was also studied.
Digital Article Identifier (DAI):
1973
82879
Biophysical Analysis of the Interaction of Polymeric Nanoparticles with Biomimetic Models of the Lung Surfactant
Abstract:
The human body offers many avenues that could be used for drug delivery. The pulmonary route, which is delivered through the lungs, presents many advantages that have sparked interested in the field. These advantages include; 1) direct access to the lungs and the large surface area it provides, and 2) close proximity to the blood circulation. The air-blood barrier of the alveoli is about 500 nm thick. The air-blood barrier consist of a monolayer of lipids and few proteins called the lung surfactant and cells. This monolayer consists of ~90% lipids and ~10% proteins that are produced by the alveolar epithelial cells. The two major lipid classes constitutes of various saturation and chain length of phosphatidylcholine (PC) and phosphatidylglycerol (PG) representing 80% of total lipid component. The major role of the lung surfactant monolayer is to reduce surface tension experienced during breathing cycles in order to prevent lung collapse. In terms of the pulmonary drug delivery route, drugs pass through various parts of the respiratory system before reaching the alveoli. It is at this location that the lung surfactant functions as the air-blood barrier for drugs. As the field of nanomedicine advances, the use of nanoparticles (NPs) as drug delivery vehicles is becoming very important. This is due to the advantages NPs provide with their large surface area and potential specific targeting. Therefore, studying the interaction of NPs with lung surfactant and whether they affect its stability becomes very essential. The aim of this research is to develop a biomimetic model of the human lung surfactant followed by a biophysical analysis of the interaction of polymeric NPs. This biomimetic model will function as a fast initial mode of testing for whether NPs affect the stability of the human lung surfactant. The model developed thus far is an 8-component lipid system that contains major PC and PG lipids. Recently, a custom made 16:0/16:1 PC and PG lipids were added to the model system. In the human lung surfactant, these lipids constitute 16% of the total lipid component. According to the author’s knowledge, there is not much monolayer data on the biophysical analysis of the 16:0/16:1 lipids, therefore more analysis will be discussed here. Biophysical techniques such as the Langmuir Trough is used for stability measurements which monitors changes to a monolayer's surface pressure upon NP interaction. Furthermore, Brewster Angle Microscopy (BAM) employed to visualize changes to the lateral domain organization. Results show preferential interactions of NPs with different lipid groups that is also dependent on the monolayer fluidity. Furthermore, results show that the film stability upon compression is unaffected, but there are significant changes in the lateral domain organization of the lung surfactant upon NP addition. This research is significant in the field of pulmonary drug delivery. It is shown that NPs within a certain size range are safe for the pulmonary route, but little is known about the mode of interaction of those polymeric NPs. Moreover, this work will provide additional information about the nanotoxicology of NPs tested.
Digital Article Identifier (DAI):
1972
82878
Calcined Tertiaries Hydrotalcites as Supports of Cobalt-Molybdenum Based Catalysts for the Hydrodesulfurization Reaction of Dibenzothiophene
Abstract:
Nowadays, light conventional crude oils are going down. Therefore, the exploitation of heavy crude oils has been increasing. Hence, a major quantity of refractory sulfur compounds such as dibenzothiophene (DBT) should be removed. Many efforts have been carried out to modify hydrotreatment typical supports in order to increase hydrodesulfurization (HDS) reactions. The present work shows the synthesis of tertiaries MgFeAl(0.16), MgFeAl(0.32), CoFeAl, ZnFeAl hydrotalcites, as supports of CoMo based catalysts, where 0.16 and 0.32 are the Fe3+/Al3+ molar ratio. Solids were characterized by different techniques (XRD, CO2-TPD, H2-TPR, FT-IR, BET, Chemical Analysis and HRTEM) and tested in the DBT HDS reaction. The reactions conditions were: Temp=325°C, P=40 Bar, H2/feed=475. Results show that the catalysts CoMo/MgFeAl(0.16) and CoMo/MgFeAl(0.32), which were the most basics, reduced the sulfur content from 500ppm to less than 1 ppm, increasing the cyclohexylbenzene content, i.e. presented a higher selective toward the HYD pathway than reference catalyst CoMo/γ- Al2O3. This is suitable for improving the fuel quality due to the increase of the cetane number. These catalysts were also more active to the HDS reaction increasing the direct desulfurization (DDS) way and presented a good stability. It is advantageous when the gas oil centane number should be improved. Cobalt, iron or zinc species inside support could avoid the Co and Mo dispersion or form spinel species which could be less active to hydrodesulfuration reactions, while hydrotalcites containing Mg increases the HDS activity probably due to improved Co/Mo ratio.
Digital Article Identifier (DAI):
1971
82801
Chemical and Electrochemical Syntheses of Two Organic Components of Ginger
Abstract:
Ginger (Zingiber officinale) is a perennial plant from Southeast Asia, widely used as a spice, herb, and medicine for many illnesses since its beneficial health effects were observed thousands of years ago. Among the compounds found in ginger, zingerone [4-hydroxy-3- methoxyphenyl-2-butanone] deserves special attention: it has an anti-inflammatory and antispasmodic effect, it can be used in case of diarrheal disease, helps to prevent the formation of blood clots, has antimicrobial properties, and can also play a role in preventing the Alzheimer's disease. Ferulic acid [(E)-3-(4-hydroxy-3-methoxyphenyl)-prop-2-enoic acid] is another cinnamic acid derivative in ginger, which has promising properties. Like many phenolic compounds, ferulic acid is also an antioxidant. Based on the results of animal experiments, it is assumed to have a direct antitumoral effect in lung and liver cancer. It also deactivates free radicals that can damage the cell membrane and the DNA and helps to protect the skin against UV radiation. The aim of this work was to synthesize these two compounds by new methods. A few of the reactions were based on the hydrogenation of dehydrozingerone [4-(4-Hydroxy-3-methoxyphenyl)-3-buten-2-one] to zingerone. Dehydrozingerone can be synthesized by a relatively simple method from acetone and vanillin with good yield (80%, melting point: 41 °C). Hydrogenation can be carried out chemically, for example by the reaction of zinc and acetic acid, or Grignard magnesium and ethyl alcohol. Another way to complete the reduction is the electrochemical pathway. The electrolysis of dehydrozingerone without diaphragm in aqueous media was attempted to produce ferulic acid in the presence of sodium carbonate and potassium iodide using platinum electrodes. The electrolysis of dehydrozingerone in the presence of potassium carbonate and acetic acid to prepare zingerone was carried out similarly. Ferulic acid was expected to be converted to dihydroferulic acid [3-(4-Hydroxy-3-methoxyphenyl)propanoic acid] in potassium hydroxide solution using iron electrodes, separating the anode and cathode space with a Soxhlet paper sheath impregnated with saturated magnesium chloride solution. For this reaction, ferulic acid was synthesized from vanillin and malonic acid in the presence of pyridine and piperidine (yield: 88.7%, melting point: 173°C). Unfortunately, in many cases, the expected transformations did not happen or took place in low conversions, although gas evolution occurred. Thus, a deeper understanding of these experiments and optimization are needed. Since both compounds are found in different plants, they can also be obtained by alkaline extraction or steam distillation from distinct plant parts (ferulic acid from ground bamboo shoots, zingerone from grated ginger root). The products of these reactions are rich in several other organic compounds as well; therefore, their separation must be solved to get the desired pure material. The products of the reactions described above were characterized by infrared spectral data and melting points. The use of these two simple methods may be informative for the formation of the products. In the future, we would like to study the ferulic acid and zingerone content of other plants and extract them efficiently. The optimization of electrochemical reactions and the use of other test methods are also among our plans.
Digital Article Identifier (DAI):
1970
82774
Extrudable Foamed Concrete: General Benefits in Prefabrication and Comparison in Terms of Fresh Properties and Compressive Strength with Classic Foamed Concrete
Abstract:
Foamed concrete belongs to the category of lightweight concrete. It is characterized by a density which is generally ranging from 200 to 2000 kg/m³ and typically comprises cement, water, preformed foam, fine sand and eventually fine particles such as fly ash or silica fume. The foam component mixed with the cement paste give rise to the development of a system of air-voids in the cementitious matrix. The peculiar characteristics of foamed concrete elements are summarized in the following aspects: 1) lightness which allows reducing the dimensions of the resisting frame structure and is advantageous in the scope of refurbishment or seismic retrofitting in seismically vulnerable areas; 2) thermal insulating properties, especially in the case of low densities; 3) the good resistance against fire as compared to ordinary concrete; 4) the improved workability; 5) cost-effectiveness due to the usage of rather simple constituting elements that are easily available locally. Classic foamed concrete cannot be extruded, as the dimensional stability is not permitted in the green state and this severely limits the possibility of industrializing them through a simple and cost-effective process, characterized by flexibility and high production capacity. In fact, viscosity enhancing agents (VEA) used to extrude traditional concrete, in the case of foamed concrete cause the collapsing of air bubbles, so that it is impossible to extrude a lightweight product. These requirements have suggested the study of a particular additive that modifies the rheology of foamed concrete fresh paste by increasing cohesion and viscosity and, at the same time, stabilizes the bubbles into the cementitious matrix, in order to allow the dimensional stability in the green state and, consequently, the extrusion of a lightweight product. There are plans to submit the additive’s formulation to patent. In addition to the general benefits of using the extrusion process, extrudable foamed concrete allow other limits to be exceeded: elimination of formworks, expanded application spectrum, due to the possibility of extrusion in a range varying between 200 and 2000 kg/m³, which allows the prefabrication of both structural and non-structural constructive elements. Besides, this contribution aims to present the significant differences regarding extrudable and classic foamed concrete fresh properties in terms of slump. Plastic air content, plastic density, hardened density and compressive strength have been also evaluated. The outcomes show that there are no substantial differences between extrudable and classic foamed concrete compression resistances.
Digital Article Identifier (DAI):
1969
82675
Equilibrium and Kinetic Studies of Lead Adsorption on Activated Carbon Derived from Mangrove Propagule Waste by Phosporic Acid Activation
Abstract:
The removal of lead ion (Pb2+) from aqueous solution by activated carbon with phosporic acid activation employing mangrove propagule as precursor was investigated in a batch adsorption system. Batch studies were carried out to address various experimental parameters including pH and contact time. The Langmuir and Freundlich models were able to describe the adsorption equilibrium while the pseudo first order and pseudo second order models were used to describe kinetic process of Pb2+ adsorption. The results show that the adsorption data is seen in accordance with Langmuir isotherm model and pseudo-second order kinetic model.
Digital Article Identifier (DAI):
1968
82633
Structural and Photoluminescence Properties of Glancing Angle Deposition Synthesized SiOₓ/ZnO Heterostructure Nanocluster
Abstract:
We report on the synthesis of ZnO nanocluster and SiOₓ/ZnO heterostructure nanocluster on a Si p-type (100) substrate using Glancing Angle Deposition (GLAD) technique. The structural and photoluminescence properties of ZnO nanocluster and SiOₓ/ZnO heterostructure nanocluster were measured using X-Ray Diffractometer (XRD), Fourier Transform Infrared (FTIR) spectroscopy and Photoluminescence (PL) spectrophotometer characterization techniques. The XRD spectrum of both samples revealed the formation of crystalline ZnO having wurtzite structure characterized with dominant (100), (002), (101), and (110) peaks. No characteristic peak of SiOₓ nanocluster was detected which confirms amorphous in nature. The enhancement in the intensity of ZnO (002) diffraction peak is attributed to the preferential growth of SiOₓ/ZnO heterostructure nanocluster as compared to the ZnO nanocluster. We determined the average crystallite size estimated from the full width half maximum (FWHM) for ZnO nanocluster and SiOₓ deposited on ZnO nanocluster and found to be ~ 8.051 nm and ~ 10.436 nm respectively. HRTEM image showed the formation of heterostructure nanocluster which consists of ZnO with length ~225 nm and SiOₓ with length ~248 nm. The vibrational frequencies in the FTIR spectra further confirm the formation of wurtzite structure in ZnO. The peak that appeared in 420 cm⁻¹ of the spectra is due to stretching vibration mode of ZnO, and the Si-O asymmetric stretching at 1109 cm⁻¹ is attributed to oxygen impurities dissolved in the Si-substrate. The PL properties of ZnO nanocluster and SiOₓ/ZnO heterostructure nanocluster at different excitation wavelengths of 325 nm and 350 nm were investigated in details. Visible emission in ZnO nanocluster is attributed to different intrinsic defects. A broad blue-violet peak emission at 450 nm (~ 2.75 eV) at room temperature is due to the non-radiative recombination between the electrons in a deep defect level or a shallow surface defect level of Zinc interstitials (Zni) and the holes in the valence band. Compared with ZnO nanocluster, the emission peak shifted to 457 nm in SiOₓ/ZnO heterostructure nanocluster. The intensity of blue emissions exhibits nonlinear increase-decrease dependence, in SiOₓ/ZnO heterostructure nanocluster first increasing, the saturation at the bandgap energy as the optimal excitation energy and finally decreasing but still effectively emitting as slowly dropping tail emission peaks at 468 nm which is due to transitions from Zni and extended Zni states to the valence band. The property of blue violet emission and interesting peak shift indicate potential applications in optoelectronics device.
Digital Article Identifier (DAI):
1967
82626
Influence of Ag Nanoparticles Patterned on Well Aligned SiOₓ Nanowire Arrays for Enlarged Photodetection
Abstract:
Silver (Ag) nanoparticles (NPs) patterned SiOₓ nanowire (NW) arrays were synthesized on Si substrates by using a catalytic free technique called Glancing Angle Deposition (GLAD) technique. The successful growth of Ag patterned SiOₓ NWs on Si substrate is manifested through the field emission gun scanning electron microscopy with energy dispersive spectroscopy analysis and transmission electron microscope analysis. The Ag patterned SiOₓ NW consists of ~140 nm SiOₓ NW and ~20 nm Ag NPs. The TEM image also reveals the crystalline nature of Ag NPs and amorphous nature of SiOₓ NWs. The photoluminescence spectrum of the sample shows broad band emission exhibiting peak values at 374 nm and 667 nm at an excitation wavelength of 250 nm that corresponds to Ag nanoparticles and SiOₓ NWs respectively. The Ag patterned SiOₓ NWs exhibit a low bandgap of 1.9 eV due to the significant reduction in the recombination of holes and electrons in the SiOₓ layer. The Ag patterned SiOₓ NW-based device shows improvements in photodetection under white-light illumination compared to dark condition due to the hole trapping process at the metal-Ag patterned SiOₓ NW interface states that effectively reduced the depletion width under reverse bias and the Schottky height at the junction, which in turn enhanced electron tunneling process. It is also interesting to know that the device exhibited a low turn-on voltage (~0.6 V) as well as a fast response of 0.16 s (rise time) and 0.17 s (fall time) which makes it a potential application in optoelectronics.
Digital Article Identifier (DAI):
1966
82568
A Method for Delay-Tolerant Networking Congestion Problem Based on Distributed Storage
Abstract:
Volatile organic compounds (VOCs) are one of major air contaminants, and they can react with nitrogen oxides (NOx) in atmosphere to form ozone (O3) and peroxyacetyl nitrate (PAN) with solar irradiation, leading to environmental hazards. In addition, some VOCs are toxic at low concentration levels and cause adverse effects on human health. How to effectively reduce VOCs emission has become an important issue. Thermal catalysis is regarded as an effective way for VOCs removal because it provides oxidation route to successfully convert VOCs into carbon dioxide (CO2) and water (H2O(g)). Single perovskite-type catalysts are promising for VOC removal, and they are of good potential to replace noble metals due to good activity and high thermal stability. Single perovskites can be generally described as ABO3 or A2BO4, where A-site is often a rare earth element or an alkaline. Typically, the B-site is transition metal cation (Fe, Cu, Ni, Co, or Mn). Catalytic properties of perovskites mainly rely on nature, oxidation states and arrangement of B-site cation. Interestingly, single perovskites could be further synthesized to form double perovskite-type catalysts which can simply be represented by A2B’B”O6. Likewise, A-site stands for an alkaline metal or rare earth element, and the B′ and B′′ are transition metals. Double perovskites possess unique surface properties. In structure, three-dimensional of B-site with ordered arrangement of B’O6 and B”O6 is presented alternately, and they corner-share octahedral along three directions of the crystal lattice, while cations of A-site position between the void of octahedral. It has attracted considerable attention due to specific arrangement of alternating B-site structure. Therefore, double perovskites may have more variations than single perovskites, and this greater variation may promote catalytic performance. It is expected that activity of double perovskites is higher than that of single perovskites toward VOC removal. In this study, double perovskite-type catalyst (La2CoMnO6) is prepared and evaluated for VOC removal. Also, single perovskites including LaCoO3 and LaMnO3 are tested for the comparison purpose. Toluene (C7H8) is one of the important VOCs which are commonly applied in chemical processes. In addition to its wide application, C7H8 has high toxicity at a low concentration. Therefore, C7H8 is selected as the target compound in this study. Experimental results indicate that double perovskite (La2CoMnO6) has better activity if compared with single perovskites. Especially, C7H8 can be completely oxidized to CO2 at 300oC as La2CoMnO6 is applied. Characterization of catalysts indicates that double perovskite has unique surface properties and is of higher amounts of lattice oxygen, leading to higher activity. For durability test, La2CoMnO6 maintains high C7H8 removal efficiency of 100% at 300oC and 30,000 h-1, and it also shows good resistance to CO2 (5%) and H2O(g) (5%) of gas streams tested. For various VOCs including isopropyl alcohol (C3H8O), ethanal (C2H4O), and ethylene (C2H4) tested, as high as 100% efficiency could be achieved with double perovskite-type catalyst operated at 300℃, indicating that double perovskites are promising catalysts for VOCs removal, and possible mechanisms will be elucidated in this paper.
Digital Article Identifier (DAI):
1965
82521
Reduction of Nitrogen Monoxide with Carbon Monoxide from Gas Streams by 10% wt. Cu-Ce-Fe-Co/Activated Carbon
Abstract:
Nitrogen oxides (NOₓ) is regarded as one of the most important air pollutants. It not only causes adverse environmental effects but also harms human lungs and respiratory system. As a post-combustion treatment, selective catalytic reduction (SCR) possess the highest NO removal efficiency ( ≥ 85%), which is considered as the most effective technique for removing NO from gas streams. However, injection of reducing agent such as NH₃ is requested, and it is costly and may cause secondary pollution. Reduction of NO with carbon monoxide (CO) as reducing agent has been previously investigated. In this process, the key step involves the NO adsorption and dissociation. Also, the high performance mainly relies on the amounts of oxygen vacancy on catalyst surface and redox ability of catalyst, because oxygen vacancy can activate the N-O bond to promote its dissociation. Additionally, perfect redox ability can promote the adsorption of NO and oxidation of CO. Typically, noble metals such as iridium (Ir), platinum (Pt), and palladium (Pd) are used as catalyst for the reduction of NO with CO; however, high cost has limited their applications. Recently, transition metal oxides have been investigated for the reduction of NO with CO, especially CuₓOy, CoₓOy, Fe₂O₃, and MnOₓ are considered as effective catalysts. However, deactivation is inevitable as oxygen (O₂) exists in the gas streams because active sites (oxygen vacancies) of catalyst are occupied by O₂. In this study, Cu-Ce-Fe-Co is prepared and supported on activated carbon by impregnation method to form 10% wt. Cu-Ce-Fe-Co/activated carbon catalyst. Generally, addition of activated carbon on catalyst can bring several advantages: (1) NO can be effectively adsorbed by interaction between catalyst and activated carbon, resulting in the improvement of NO removal, (2) direct NO decomposition may be achieved over carbon associated with catalyst, and (3) reduction of NO could be enhanced by a reducing agent over carbon-supported catalyst. Therefore, 10% wt. Cu-Ce-Fe-Co/activated carbon may have better performance for reduction of NO with CO. Experimental results indicate that NO conversion achieved with 10% wt. Cu-Ce-Fe-Co/activated carbon reaches 83% at 150°C with 300 ppm NO and 10,000 ppm CO. As temperature is further increased to 200°C, 100% NO conversion could be achieved, implying that 10% wt. Cu-Ce-Fe-Co/activated carbon prepared has good activity for the reduction of NO with CO. In order to investigate the effect of O₂ on reduction of NO with CO, 1-5% O₂ are introduced into the system. The results indicate that NO conversions still maintain at ≥ 90% with 1-5% O₂ conditions at 200°C. It is worth noting that effect of O₂ on reduction of NO with CO could be significantly improved as carbon is used as support. It is inferred that carbon support can react with O₂ to produce CO₂ as O₂ exists in the gas streams. Overall, 10% wt. Cu-Ce-Fe-Co/activated carbon is demonstrated with good potential for reduction of NO with CO, and possible mechanisms will be elucidated in this paper.
Digital Article Identifier (DAI):
1964
82499
Pd(II) Complex with 4-Bromo-2,6-Bis-Hydroxymethyl-Phenol and Nikotinamid: Synthesis and Spectral Analysis
Abstract:
In the present study, the reactions involving 4-Bromo-2,6-bis-hydroxymethyl-phenol (BBHMP) and nikotinamide (NA) in the presence Pd (II) ion were investigated. Optimum conditions for the reactions were established as pH 7 and λ = 450 nm. According to absorbance measurements, the mole ratio of BBHMP : NA : Pd2+ was found as 1 : 2 : 2. As a result of physico-chemical, spectrophotometric and thermal analysis results, the reactions of BBHMP and NA with Pd (II) is complexation reactions and one molecule BBHMP and two molecules of NA react with two molecules of metal (II) ion.
Digital Article Identifier (DAI):
1963
82487
Computational Fluid Dynamics Modelling of Liquefied Natural Gas Pool Fires
Abstract:
There is an increased risk of uncontrolled LNG leakage from equipment that transports and stores this product. This is a consequence of the increasing global demand for natural gas in the last two decades. As a result of such leakage of liquid gas from a faulty installation, a pool fire may occur. The pool fire is most often the result of the ignition of the released evaporation of liquid flammable substances, which form a spillage on the surface of the substrate. An example of a surface fire may be the leakage of volatile liquids, liquefied gases (e.g. LNG) from apparatus, tanks or pipelines. As a result of pool fire, thermal radiation and toxic combustion products are generated that pose a threat to the surrounding populations. Therefore, an important factor is the assessment of a safe distance ensuring that there are no irreversible health effects, property and environmental damage. In the presented work, the CFD model of pool fire has been applied to numerical simulations of methane combustion and risk assessment of such an event. The implemented CFD model in ANSYS Fluent v. 18.2 software was based on the concept of infinitely fast combustion reactions (Eddy Dissipation Model). The gas flow was modelled using the SAS turbulence model. The usage of SAS turbulence model was due to the superior accuracy of SAS results relative to URANS simulation and less hardware and CPU requirements in case of LES models. The numerical simulation of the LNG surface fire also included the radiation mechanism (Discrete Ordinates model). The risk analysis included the possibility of receiving a hazardous amount of thermal radiation by nearby leaving population. A 300 m diameter and 300 m height domain contained 1.1 million hexahedral elements. In calculations, it was assumed that the surface area of liquid LNG was 81 m. The evaporation rate of methane was 0.016 kg/m²s. Numerical simulations were carried out both in the absence of wind and for different values of wind speed. The results obtained in the form of temperature profiles, concentration of reactants and products of combustion reaction, intensity of thermal radiation were used to analyze the risk assessment of pool fire due to the leakage of LNG which could occur in industrial installations. An example may be the determination of a safe distance from a fire source where the radiation dose does not exceed 2.5 kW/m² as the minimum dose that causes pain after 60 s. The results obtained from numerical simulation were consistent with the experimental data published by Sandia National Laboratories in 2011. In the future, it is also planned to perform a numerical simulation of pool fire on a particular industrial site adjacent to residential and public buildings.
Digital Article Identifier (DAI):
1962
82416
Photocatalytic Conversion of Water/Methanol Mixture into Hydrogen Using Cerium/Iron Oxides Based Structures
Abstract:
This research work reports the photocatalytic production of hydrogen from water-methanol mixture using three different 15% ceria/iron oxide catalysts. The catalysts were prepared by physical mixing, precipitation, and ultrasonication methods and labeled as catalysts A-C. The structural and texture properties of the obtained catalysts were confirmed by X-ray diffraction (XRD), BET-surface area analysis and transmission electron microscopy (TEM). The photocatalytic activity of the three catalysts towards hydrogen generation was then tested. Promising hydrogen productivity was obtained by the three catalysts however different gases compositions were obtained by each type of catalyst. Specifically, catalyst A had produced hydrogen mixed with CO₂ while the composite structure (catalyst B) had generated only pure H₂. In the case of catalyst C, syngas made of H₂ and CO was revealed, as a novel product, for the first time, in such process.
Digital Article Identifier (DAI):
1961
82076
Real-Time Observation of Concentration Distribution for Mix Liquids including Water in Micro Fluid Channel with Near-Infrared Spectroscopic Imaging Method
Abstract:
In order to quantitatively comprehend thermal flow for some industrial applications such as nuclear and chemical reactors, detailed measurements for temperature and abundance (concentration) of materials at high temporal and spatial resolution are required. Additionally, rigorous evaluation of the size effect is also important for practical realization. This paper introduces a real-time spectroscopic imaging method in micro scale field, which visualizes temperature and concentration distribution of a liquid or mix liquids with near-infrared (NIR) wavelength region. This imaging principle is based on absorption of pre-selected narrow band from absorption spectrum peak or its dependence property of target liquid in NIR region. For example, water has a positive temperature sensitivity in the wavelength at 1905 nm, therefore the temperature of water can be measured using the wavelength band. In the experiment, the real-time imaging observation of concentration distribution in micro channel was demonstrated to investigate the applicability of micro-scale diffusion coefficient and temperature measurement technique using this proposed method. The effect of thermal diffusion and binary mutual diffusion was evaluated with the time-series visualizations of concentration distribution.
Digital Article Identifier (DAI):
1960
82060
Mucoadhesive Chitosan-Coated Nanostructured Lipid Carriers for Oral Delivery of Amphotericin B
Abstract:
Oral delivery of amphotericin B (AmpB) potentially eliminates constraints and side effects associated with intravenous administration, but remains challenging due to the physicochemical properties of the drug such that it results in meagre bioavailability (0.3%). In an advanced formulation, 1) nanostructured lipid carriers (NLC) were formulated as they can accommodate higher levels of cargoes and restrict drug expulsion and 2) a mucoadhesion feature was incorporated so as to impart sluggish transit of the NLC along the gastrointestinal tract and hence, maximize uptake and improve bioavailability of AmpB. The AmpB-loaded NLC formulation was successfully formulated via high shear homogenisation and ultrasonication. A chitosan coating was adsorbed onto the formed NLC. Physical properties of the formulations; particle size, zeta potential, encapsulation efficiency (%EE), aggregation states and mucoadhesion as well as the effect of the variable pH on the integrity of the formulations were examined. The particle size of the freshly prepared AmpB-loaded NLC was 163.1 ± 0.7 nm, with a negative surface charge and remained essentially stable over 120 days. Adsorption of chitosan caused a significant increase in particle size to 348.0 ± 12 nm with the zeta potential change towards positivity. Interestingly, the chitosan-coated AmpB-loaded NLC (ChiAmpB NLC) showed significant decrease in particle size upon storage, suggesting 'anti-Ostwald' ripening effect. AmpB-loaded NLC formulation showed %EE of 94.3 ± 0.02 % and incorporation of chitosan increased the %EE significantly, to 99.3 ± 0.15 %. This suggests that the addition of chitosan renders stability to the NLC formulation, interacting with the anionic segment of the NLC and preventing the drug leakage. AmpB in both NLC and ChiAmpB NLC showed polyaggregation which is the non-toxic conformation. The mucoadhesiveness of the ChiAmpB NLC formulation was observed in both acidic pH (pH 5.8) and near-neutral pH (pH 6.8) conditions as opposed to AmpB-loaded NLC formulation. Hence, the incorporation of chitosan into the NLC formulation did not only impart mucoadhesive property but also protected against the expulsion of AmpB which makes it well-primed as a potential oral delivery system for AmpB.
Digital Article Identifier (DAI):
1959
81897
Chemometrics Assisted Spectrophotometric Determination of Certain Pharmaceuticals Containing Candesartan Cilexetil and Hydrochlorothiazide
Abstract:
The simultaneous determination of candesartan cilexetil and hydrochlorothiazide mixtures by using spectrophotometric method is a difficult task in analytical chemistry, due to spectral interferences. UV-spectra of the studied drugs were collected from 200 nm to 350 nm in ethanol solutions. In this range, the studied drugs showed a considerable degree of spectral overlapping (91.82%). Initial studies of the UV-spectra of the individual compounds showed that satisfactory linear regression calibration models could be constructed in the concentration range of 5-50µg/ml and 2-20µg/ml for candesartan and hydrochlorothiazide respectively. Resolution of binary mixtures of the drugs has been accomplished by using ¹D (first derivative), ¹D ratio (first derivative ratio). The multivariate methods, classical least squares (CLS) and principal components regression (PCR) have also been used for determination the studied drugs. Thus, a simple, rapid and inexpensive method for the simultaneous determination of these drugs (either in their pure powder forms, laboratory prepared samples or in their pharmaceutical formulation) was researched and developed with the aid of chemometrics assisted spectrophotometric methods.
Digital Article Identifier (DAI):
1958
81863
Effect of Reduced Dimensionality on the Magnetic and Transport Properties of Ca Doped Colossal Magnetoresistive Nanoparticles
Abstract:
Present work is focused on the synthesis and characterization of variable size (20, 26 and 32 nm) colossal magnetoresistance (CMR) (La₀.₇Ca₀.₃MnO₃) nanoparticles (NPs). Modified citrate rout was used to prepare CMR NPs. We explored the size-dependent magnetic properties such as magnetization, coercivity and electric transport properties at different fields as a function of temperature. Saturation magnetization is found to increase with increasing particle size while coercivity first increases from 78 to 210 and then decreases to 174 Oe observed at a field of 5 kOe and at 77K . Alternating current susceptibility curves of these nanoparticles with temperature were also observed showing a gradual transition from paramagnet to ferromagnetic state which supports the presence of defects' states on the surface of the nanoparticles.
Digital Article Identifier (DAI):
1957
81849
Room Temperature Ferromagnetism in (Al,Co) Co-Doped Zno Nanoparticles: Effect of Annealing Time and Pressure
Abstract:
The effects of aluminum, a trivalent substitute have been investigated in the Zn0.96Co0.04O with regard to the role of additional carriers in the n-type ferromagnetic semiconductor. Nanoparticle samples of Zn0.96-yCo0.04AlyO with the different Al composition (y = 0.0025, 0.005, 0.0075 and 0.01) were prepared from the acetate-derived precursor by the sol-gel route. The structural and magnetic properties of the nanoparticles have been investigated. X-ray diffraction measurements show that the nanoparticles were crystallized in Wurtzite ZnO structure after annealing reducing environment (Ar 95% + H5%). We generally find an increase in the magnetization with increase in Al content except at the lowest concentration. The effect of annealing time and annealing gas pressure were also investigated.
Digital Article Identifier (DAI):
1956
81626
ZnO Nanoparticles as Photocatalysts: Synthesis, Characterization and Application
Abstract:
ZnO nanostructures have been synthesized successfully in high yield via catalyst-free chemical precipitation technique by varying zinc source (either zinc nitrate or zinc acetate) and oxygen source (either oxalic acid or urea) without using any surfactant, organic solvent or capping agent. The ZnO nanostructures were characterized by Fourier transform infrared spectroscopy (FT-IR), X-ray diffractometry (XRD), scanning electron microscopy (SEM), thermal gravimetric analysis (TGA), UV-vis diffuse reflection spectroscopy (UV-vis DRS), and photoluminescence spectroscopy (PL). The FTIR peak in the range of 450-470 cm-1 corresponded to Zn-O stretching in ZnO structure. The synthesized ZnO samples showed well crystalized hexagonal wurtzite structure. SEM micrographs displayed spherical droplet of about 50-100 nm. The band gap of prepared ZnO was found to be 3.4-3.5 eV. The presence of PL peak at 468 nm was attributed to surface defect state. The photocatalytic activity of ZnO was studied by monitoring the photodegradation of reactive red (RR141) azo dye under ultraviolet (UV) light irradiation. Blank experiment was also separately carried out by irradiating the aqueous solution of the dye in absence of the photocatalyst. The initial concentration of the dye was fixed at 10 mgL-1. About 50 mg of ZnO photocatalyst was dispersed in 200 mL dye solution. The sample was collected at a regular time interval during the irradiation and then was analyzed after centrifugation. The concentration of the dye was determined by monitoring the absorbance at its maximum wavelength (λₘₐₓ) of 544 nm using UV-vis spectroscopic analysis technique. The sources of Zn and O played an important role on photocatalytic performance of the ZnO photocatalyst. ZnO nanoparticles which prepared by zinc acetate and oxalic acid at molar ratio of 1:1 showed high photocatalytic performance of about 97% toward photodegradation of reactive red azo dye (RR141) under UV light irradiation for only 60 min. This work demonstrates the promising potential of ZnO nanomaterials as photocatalysts for environmental remediation.
Digital Article Identifier (DAI):