Abstract This work reports the development of a biosensor method for the label‐free detection of ... more Abstract This work reports the development of a biosensor method for the label‐free detection of specific DNA sequences. In the initial phase, square wave voltammetry (SWV) was used in a comparative investigation into the electrochemical oxidation of purines (guanine and adenine) and DNA fragments at various electrode surfaces: carbon paste (CPE), glassy carbon electrode (GCE), and gold (AuE). Relative to the carbon electrodes, an approximate 4.0‐fold, 6.0‐fold, and 3.25‐fold increase in the anodic response was observed when guanine, adenine, and hydrolyzed DNA, respectively, were measured on the AuE. It was shown that the guanine and adenine bases could be successfully determined by use of SWV for a deoxyribonucleic acid sample following acid hydrolysis. This label‐free detection of hydrolyzed DNA on gold electrodes has significant advantages over methods using existing carbon electrode materials because of its higher sensitivity and the potential applicability of microfabrication techniques for the production of the requisite gold electrodes. In another phase of development, the times and conditions for DNA hydrolysis and purine release were investigated. It was shown that under optimal conditions, trace levels of the purine bases could be readily detected following 20 min of hydrolysis at room temperature. The proposed method can be used to estimate the guanine and adenine contents in DNA with in a linear range of 5–30 ng ml−1. Finally, when appropriate probe sequences were first adsorbed on the surface of the screen‐printed gold electrode (SPGE), this electrochemical biosensor could be used to specifically detect sequences from ss corona virus aviair following hybridization and hydrolysis reactions on the sensor surface. No enhancement of the voltammetric response was observed when the sensor was challenged with a non‐complementary DNA sequence.
The use of organic polymers as shell to encapsulate the organic Phase Change Materials (PCMs) pre... more The use of organic polymers as shell to encapsulate the organic Phase Change Materials (PCMs) presents some disadvantages because of their being highly flammable, having a poor thermal stability and low thermal conductivity. The use of hybrid materials composed of organic and inorganic materials constitutes a promising way to improve chemical and thermal properties of microencapsulated PCMs (MEPCMs). In this research, organic-inorganic hybrid-MEPCMs were synthesized by utilizing paraffin as core and urea-formaldehyde (UF) polymer as shell, and ZnO metal oxide nanoparticles. The prepared samples were characterized using Fourier Transform Infrared spectroscopy, X-Ray Diffraction, Scanning Electron Microscopy, Differential Scanning Calorimetry and Thermogravimetric analysis. The obtained results showed that the synthesized hybrid-MEPCMs are in spherical and irregular forms and present a rougher surface due to the presence of metal oxide nanoparticles which are scattered onto the surface of microcapsules or wrapped by UF shell material. They also indicated the probable improvement of hybrid-MEPCMs' thermal stability. In this work, the influence of metal oxides content on structural, morphological and thermal properties of hybrid-MEPCMs is discussed.
Polymer-based Nanocomposites for Energy and Environmental Applications, 2018
Abstract Referring to the International Energy Agency (IEA), the total world energy consumption w... more Abstract Referring to the International Energy Agency (IEA), the total world energy consumption was highly increased over the past 20 years in which the building applications are responsible for a significant part. This growth renders the thermal energy storage technologies, by using phase-change material (PCM) as a hot topic in the field of building applications. The PCM had a great function of reducing building energy consumption attributed to their ability to store and releasing large amounts of energy. Furthermore, the use of PCMs may improve also the overall performance and reliability of the building envelope. For this reason, wide variety generally more than 300 substances of PCMs have been used by many incorporation methods and in many specific building applications. The PCMs show superior properties over the other technologies, but their incorporation into other various building applications still remains the topic of intense research. In this respect, many studies have been devoted to the development of the novel route to preparing PCM composite by incorporation of nanoparticles such as using composite phase-change material reinforced by nanoclays and their incorporation into insulation materials of polymer foam type as PCMs.
ABSTRACT Highly sensitive label-free techniques of DNA determination are particularly interesting... more ABSTRACT Highly sensitive label-free techniques of DNA determination are particularly interesting in relation to the present development of an electrochemical hybridization biosensor for the detection of short DNA fragments specific to the human papilloma virus (HPV). Unlabeled DNA probes have been immobilized by spontaneous coadsorption of thiolated single-stranded oligonucleotides (HS-ssDNA) onto the sensing surface of a screen-printed gold electrode (SPGE). The covalently immobilized single-stranded DNA probe (HS-ssDNA) could selectively hybridize with its complementary DNA (cDNA) in solution to form double-stranded DNA (dsDNA) on the surface. DNA is treated with acid (e.g., 0.5 M chloridric acid), and the acid-released purine bases are directly determined by square wave voltammetry (SWV). Variables of the probe-immobilization and hybridization steps are optimized to offer convenient quantitation of HPV DNA target, in connection with a short hybridization time. Peak currents were found to increase in the following order: hybrid-modified SPGE, 11-base mismatched modified SPGE, 18-base mismatched SPGE, and the probe modified SPGE. Control experiments with noncomplementary oligonucleotides were carried out to assess whether the suggested DNA sensor responds selectively to the target. The effect of the target DNA concentration on the hybridization signal was also studied. Under optimal conditions, this sensor has a good calibration range with HPV DNA sequence detection limit of 2 pg · ml-1 (S/N = 3).
Currently, as the population continues to grow, the preservation of the world’s water resources i... more Currently, as the population continues to grow, the preservation of the world’s water resources is becoming a serious challenge. The seawater desalination process is considered a sustainable option for the future. The two most common technologies used in desalination are reverse osmosis (RO) and membrane distillation (MD). However, membrane fouling caused by the accumulation of contaminants membrane surface is an emerging and growing problem. then a pre-treatment stage is required to reach an optimal efficiency during desalination process, since this stage is crucial for a successful desalination process. In this regard, developing new material-based composite membranes has the potential to upgrade the anti-fouling features of RO membranes and thereby enhance the desalination efficiency due to the characteristics of these composite membranes especially, their high permeability, hydrophilicity, selectivity mechanical strength, thermal stability, and anti-bacterial property. The objective of this review is to present the main techniques for seawater pre-treatment. the results of several membrane types and methods of modification were also discussed. Finally, the performance of composite membranes for seawater pre-treatment is defined and future perspectives are highlighted.
Solar Energy Materials and Solar Cells, Dec 1, 2016
Abstract A packed bed of rocks with air as heat transfer fluid can be considered as a cost effect... more Abstract A packed bed of rocks with air as heat transfer fluid can be considered as a cost effective storage system, as it enhances the dispatchability of the concentrated solar power plant at lower costs. However, the identification of suitable rocks to be used as a storage medium requires a prior experimental characterization, since the studies published about the behaviour of rocks at high temperatures are scarce in literature. This work aims to investigate the potential of gneiss rock as a candidate storage material in solar power plants. Thus, thermal stability of two varieties of gneiss rock has been studied at temperatures up to 1000 °C during heating and cooling by thermogravimetric and differential thermal analyzer (TG/DTA). The influence of temperature on specific heat capacity, thermal diffusivity and thermal conductivity has been analyzed. Furthermore, the chemical composition and crystalline phases have been identified by X-ray fluorescence and X-ray diffraction, respectively. The obtained results proved the potential of this type of rocks in terms of high thermal capacities, high density and good thermal stability up to 550 °C.
Abstract This work reports the development of a biosensor method for the label‐free detection of ... more Abstract This work reports the development of a biosensor method for the label‐free detection of specific DNA sequences. In the initial phase, square wave voltammetry (SWV) was used in a comparative investigation into the electrochemical oxidation of purines (guanine and adenine) and DNA fragments at various electrode surfaces: carbon paste (CPE), glassy carbon electrode (GCE), and gold (AuE). Relative to the carbon electrodes, an approximate 4.0‐fold, 6.0‐fold, and 3.25‐fold increase in the anodic response was observed when guanine, adenine, and hydrolyzed DNA, respectively, were measured on the AuE. It was shown that the guanine and adenine bases could be successfully determined by use of SWV for a deoxyribonucleic acid sample following acid hydrolysis. This label‐free detection of hydrolyzed DNA on gold electrodes has significant advantages over methods using existing carbon electrode materials because of its higher sensitivity and the potential applicability of microfabrication techniques for the production of the requisite gold electrodes. In another phase of development, the times and conditions for DNA hydrolysis and purine release were investigated. It was shown that under optimal conditions, trace levels of the purine bases could be readily detected following 20 min of hydrolysis at room temperature. The proposed method can be used to estimate the guanine and adenine contents in DNA with in a linear range of 5–30 ng ml−1. Finally, when appropriate probe sequences were first adsorbed on the surface of the screen‐printed gold electrode (SPGE), this electrochemical biosensor could be used to specifically detect sequences from ss corona virus aviair following hybridization and hydrolysis reactions on the sensor surface. No enhancement of the voltammetric response was observed when the sensor was challenged with a non‐complementary DNA sequence.
The use of organic polymers as shell to encapsulate the organic Phase Change Materials (PCMs) pre... more The use of organic polymers as shell to encapsulate the organic Phase Change Materials (PCMs) presents some disadvantages because of their being highly flammable, having a poor thermal stability and low thermal conductivity. The use of hybrid materials composed of organic and inorganic materials constitutes a promising way to improve chemical and thermal properties of microencapsulated PCMs (MEPCMs). In this research, organic-inorganic hybrid-MEPCMs were synthesized by utilizing paraffin as core and urea-formaldehyde (UF) polymer as shell, and ZnO metal oxide nanoparticles. The prepared samples were characterized using Fourier Transform Infrared spectroscopy, X-Ray Diffraction, Scanning Electron Microscopy, Differential Scanning Calorimetry and Thermogravimetric analysis. The obtained results showed that the synthesized hybrid-MEPCMs are in spherical and irregular forms and present a rougher surface due to the presence of metal oxide nanoparticles which are scattered onto the surface of microcapsules or wrapped by UF shell material. They also indicated the probable improvement of hybrid-MEPCMs' thermal stability. In this work, the influence of metal oxides content on structural, morphological and thermal properties of hybrid-MEPCMs is discussed.
Polymer-based Nanocomposites for Energy and Environmental Applications, 2018
Abstract Referring to the International Energy Agency (IEA), the total world energy consumption w... more Abstract Referring to the International Energy Agency (IEA), the total world energy consumption was highly increased over the past 20 years in which the building applications are responsible for a significant part. This growth renders the thermal energy storage technologies, by using phase-change material (PCM) as a hot topic in the field of building applications. The PCM had a great function of reducing building energy consumption attributed to their ability to store and releasing large amounts of energy. Furthermore, the use of PCMs may improve also the overall performance and reliability of the building envelope. For this reason, wide variety generally more than 300 substances of PCMs have been used by many incorporation methods and in many specific building applications. The PCMs show superior properties over the other technologies, but their incorporation into other various building applications still remains the topic of intense research. In this respect, many studies have been devoted to the development of the novel route to preparing PCM composite by incorporation of nanoparticles such as using composite phase-change material reinforced by nanoclays and their incorporation into insulation materials of polymer foam type as PCMs.
ABSTRACT Highly sensitive label-free techniques of DNA determination are particularly interesting... more ABSTRACT Highly sensitive label-free techniques of DNA determination are particularly interesting in relation to the present development of an electrochemical hybridization biosensor for the detection of short DNA fragments specific to the human papilloma virus (HPV). Unlabeled DNA probes have been immobilized by spontaneous coadsorption of thiolated single-stranded oligonucleotides (HS-ssDNA) onto the sensing surface of a screen-printed gold electrode (SPGE). The covalently immobilized single-stranded DNA probe (HS-ssDNA) could selectively hybridize with its complementary DNA (cDNA) in solution to form double-stranded DNA (dsDNA) on the surface. DNA is treated with acid (e.g., 0.5 M chloridric acid), and the acid-released purine bases are directly determined by square wave voltammetry (SWV). Variables of the probe-immobilization and hybridization steps are optimized to offer convenient quantitation of HPV DNA target, in connection with a short hybridization time. Peak currents were found to increase in the following order: hybrid-modified SPGE, 11-base mismatched modified SPGE, 18-base mismatched SPGE, and the probe modified SPGE. Control experiments with noncomplementary oligonucleotides were carried out to assess whether the suggested DNA sensor responds selectively to the target. The effect of the target DNA concentration on the hybridization signal was also studied. Under optimal conditions, this sensor has a good calibration range with HPV DNA sequence detection limit of 2 pg · ml-1 (S/N = 3).
Currently, as the population continues to grow, the preservation of the world’s water resources i... more Currently, as the population continues to grow, the preservation of the world’s water resources is becoming a serious challenge. The seawater desalination process is considered a sustainable option for the future. The two most common technologies used in desalination are reverse osmosis (RO) and membrane distillation (MD). However, membrane fouling caused by the accumulation of contaminants membrane surface is an emerging and growing problem. then a pre-treatment stage is required to reach an optimal efficiency during desalination process, since this stage is crucial for a successful desalination process. In this regard, developing new material-based composite membranes has the potential to upgrade the anti-fouling features of RO membranes and thereby enhance the desalination efficiency due to the characteristics of these composite membranes especially, their high permeability, hydrophilicity, selectivity mechanical strength, thermal stability, and anti-bacterial property. The objective of this review is to present the main techniques for seawater pre-treatment. the results of several membrane types and methods of modification were also discussed. Finally, the performance of composite membranes for seawater pre-treatment is defined and future perspectives are highlighted.
Solar Energy Materials and Solar Cells, Dec 1, 2016
Abstract A packed bed of rocks with air as heat transfer fluid can be considered as a cost effect... more Abstract A packed bed of rocks with air as heat transfer fluid can be considered as a cost effective storage system, as it enhances the dispatchability of the concentrated solar power plant at lower costs. However, the identification of suitable rocks to be used as a storage medium requires a prior experimental characterization, since the studies published about the behaviour of rocks at high temperatures are scarce in literature. This work aims to investigate the potential of gneiss rock as a candidate storage material in solar power plants. Thus, thermal stability of two varieties of gneiss rock has been studied at temperatures up to 1000 °C during heating and cooling by thermogravimetric and differential thermal analyzer (TG/DTA). The influence of temperature on specific heat capacity, thermal diffusivity and thermal conductivity has been analyzed. Furthermore, the chemical composition and crystalline phases have been identified by X-ray fluorescence and X-ray diffraction, respectively. The obtained results proved the potential of this type of rocks in terms of high thermal capacities, high density and good thermal stability up to 550 °C.
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