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1 – 10 of 89Galal H. Elgemeie and Doaa M. Masoud
This paper aims to focus on the most popular technique nowadays, the use of microwave irradiation in organic synthesis; in a few years, most chemists will use microwave energy to…
Abstract
Purpose
This paper aims to focus on the most popular technique nowadays, the use of microwave irradiation in organic synthesis; in a few years, most chemists will use microwave energy to heat chemical reactions on a laboratory scale. Also, many scientists use microwave technology in the industry. They have turned to microwave synthesis as a frontline methodology for their projects. Microwave and microwave-assisted organic synthesis (MAOS) has emerged as a new “lead” in organic synthesis.
Design/methodology/approach
Using microwave radiation for synthesis and design of fluorescent dyes is of great interest, as it decreases the time required for synthesis and the synthesized dyes can be applied to industrial scale.
Findings
The technique offers many advantages, as it is simple, clean, fast, efficient and economical for the synthesis of a large number of organic compounds. These advantages encourage many chemists to switch from the traditional heating method to microwave-assisted chemistry.
Practical implications
This review highlights applications of microwave chemistry in organic synthesis for fluorescent dyes. Fluorescents are a fairly new and very heavily used class of organics. These materials have many applications, as a penetrant liquid for crack detection, synthetic resins, plastics, printing inks, non-destructive testing and sports ball dyeing.
Originality/value
The aim value of this review is to define the scope and limitation of microwave synthesis procedures for the synthesis of novel fluorescent dyes via a simple and economic way.
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Uyen Nguyen Tu Tran, Hung Ngoc Phan, Thao Thanh Hoang, Nu Thi Hong Le and Huong Mai Bui
The textile industry has consumed large quantities of water and discharged large volumes of wastewater in the dyeing process. The study aims to characterize self-dyed silk with…
Abstract
Purpose
The textile industry has consumed large quantities of water and discharged large volumes of wastewater in the dyeing process. The study aims to characterize self-dyed silk with Rhodamine B (RhB) for fashion applications to reduce textile hazards to the environment and increase the added value of silk.
Design/methodology/approach
Bombyx mori was fed with RhB-colored mulberry leaves (1500 ppm). The effects of self-dyeing were investigated via color strength K/S, Fourier-transform infrared spectroscopy (FT-IR), scanning electron microscope, X-ray diffraction, tensile strength, color fastness to washing, rubbing, perspiration and light.
Findings
Self-dyed silk possesses effective coloration and impressive color fastness (4–5/5), higher crystalline index (CrI) (73.26 ± 2.28%), less thermal stability and tenacity, slight change in amino acid composition compared with the pristine and no existence of harmful aromatic azo amines and arylamine salts.
Practical implications
The application of self-dyed silk with RhB dye has expanded new technology into fashion industry, contributing partly to economic growth and adding value to silk in the global supply chain. Besides, the self-dyeing will yield practical values in the reduction of dyeing discharge in textile industry.
Originality/value
Self-dyed silk was characterized for textile applications in comparison with pristine silk in terms of color strength and fastness as well as determined its polymeric properties relating to crystallinity, morphology, chemical composition, tensile properties and thermal stability which have not been investigated before.
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According to the play, Julius Caesar liked to have men about him that were fat, and the conspirator with the lean and hungry look asked:
L.K. El-Gabry and M.M. El-Zawahry
Nylon 6 fabric is pretreated with tannic acid and subsequently dyed with a cationic dye, Rhodamine B, from an aqueous dye solution and emulsion phase. The emulsion phase of…
Abstract
Nylon 6 fabric is pretreated with tannic acid and subsequently dyed with a cationic dye, Rhodamine B, from an aqueous dye solution and emulsion phase. The emulsion phase of n-hexadecane is emulsified by isopropyl alcohol and stabilized by Rhodamine B/tannic acid complex. Different factors affecting pretreatment and dyeing process have been studied. Changes of moisture regain, tensile strength, elongation and binding stiffness of the pretreated fabric are investigated.
The FTIR spectra of tannic acid pretreatment of nylon are also examined. The pretreated fabric with 10% owf tannic acid shows a slight increase in the tensile strength and elongation percentage. A higher moisture regain and binding stiffness are observed with increases in the amount of tannic acid. The results also indicate that the pretreatment for cationic dyed nylon 6 fabrics with tannic acid promote a higher dye uptake and cationic dye-based emulsion system with better fastness properties relative to those of the dye solution based system. A further improvement in wet fastness is secured by an aftertreatment of all dyed fabrics with a commercial anionic fluorescent whitening agent, Uvitex® RSB 150%.
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Wenjie Wang, Mengran Zhang, Binxia Zhao, Linxue Liu, Ruixuan Han and Nan Wang
The purpose of this paper is to improve the degradation efficiency of Rhodamine B (RhB) by new photocatalytic materials.
Abstract
Purpose
The purpose of this paper is to improve the degradation efficiency of Rhodamine B (RhB) by new photocatalytic materials.
Design/methodology/approach
Binary Z-scheme g-C3N4/Bi2WO6 photocatalytic material was synthesized by the one-step hydrothermal reaction. The construction of Z-scheme heterojunction led to the rapid separation of photogenerated electrons and holes, which would degrade RhB into small molecular substances to achieve the purpose of degradation.
Findings
It was found that Bi2WO6/25%g-C3N4 displayed the highest photocatalytic activity, which was about 1.44 and 1.34 times higher than that of pure Bi2WO6 and g-C3N4, respectively. According to the trapping experiments, the superoxide radical (·O2−) was the major active species of the RhB decomposition in Bi2WO6/g-C3N4 catalysts.
Originality/value
The successful synthesis of Z-scheme Bi2WO6/g-C3N4 provides new ideas and references for the design of catalysts with high photocatalytic activity, which should have wide applications in the future.
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The purpose of this study is to evaluate the possibility of using titanium dioxide coating in the field of architectural heritage.
Abstract
Purpose
The purpose of this study is to evaluate the possibility of using titanium dioxide coating in the field of architectural heritage.
Design/methodology/approach
In this research, a titanium dioxide coating was prepared and then applied to the travertine stone surfaces. The nature of the coating was determined through various observations and analyses. Moreover, the effect of photocatalytic self-cleaning was evaluated using an organic dye (Rhodamine B).
Findings
The results of XRD, DLS and SEM confirmed the formation of small anatase crystals. The hydrophilic behavior on the surface was observed by coatings based on titanium dioxide.
Research limitations/implications
The self-cleaning ability of titanium dioxide is due to the synergistic effect of its optical inductive property, which is activated with sunlight.
Practical implications
The self-cleaning coatings are interested for many industries. The reported data can be used by the formulators working in the research and development departments.
Social implications
Self-cleaning systems are considered as smart coatings. Therefore, the developing of its knowledge can help to extend its usage to different applications.
Originality/value
The application of titanium dioxide coating in the field of architectural heritage is a great challenge. Therefore, in this research, a titanium dioxide coating was prepared by sol-gel method and then applied on travertine surfaces and its properties were studied.
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This paper aims to investigate the reusability of metal/metal oxide-coupled ZnO nanorods (ZnO NRs) to degrade rhodamine B (RhB).
Abstract
Purpose
This paper aims to investigate the reusability of metal/metal oxide-coupled ZnO nanorods (ZnO NRs) to degrade rhodamine B (RhB).
Design/methodology/approach
ZnO NRs particles were synthesized by precipitation method and used to remove various types of metal ions such as Cu2+, Ag+, Mn2+, Ni2+, Pb2+, Cd2+ and Cr2+ ions under UV illumination. The metal/metal oxide-coupled ZnO NRs were characterized by scanning electron microscope, X-ray diffraction and UV-Vis diffuse reflectance. The photodegradation of RhB dye by these metal/metal oxide-coupled ZnO NRs under UV exposure was assessed.
Findings
The metal/metal oxide-coupled ZnO NRs were successfully reused to remove RhB dye in which more than >90% of RhB dye was degraded under UV exposure. Furthermore, the coupling of Ag, CuO, MnO2, Cd and Ni particles onto the surface of ZnO NRs even enhanced the degradation of dye. The dominant reactive species involved in the degradation of RhB dye were •OH- and •O2−-free radicals.
Research limitations/implications
The coupling of metal/metal oxide onto the surface of ZnO NRs after metal ions removal could affect the photocatalytic performance of ZnO NRs in the degradation of organic pollutants in subsequent stage.
Practical implications
A good reusability performance of metal/metal oxide-coupled ZnO NRs make ZnO NRs become a desirable photocatalyst material for the treatment of wastewater, which consists of both heavy metal ions and organic dyes.
Originality/value
Metal/metal oxide coupling onto the surface of ZnO NRs particles improved subsequent UV-assisted photocatalytic degradation of RhB dye.
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Abstract
Purpose
The aim of this paper is to synthesize graphene-modified titanium dioxide (GR-TiO2) nanorod arrays nanocomposite films, so that these can enhance the photocatalytic properties of titanium dioxide and overcome the problem of difficult separation and recovery of photocatalysts.
Design/methodology/approach
The GR-TiO2 nanocomposite films were synthesized via hydrothermal method and spin-coating. The obtained samples were characterized by X-ray diffraction (XRD), scanning electron microscope (SEM), ultraviolet–visible (UV-Vis) diffuse reflectance spectrum and Raman spectrum. The photocatalytic performance of the GR-TiO2 nanocomposite films for degrading Rhodamin B under ultraviolet (UV) was studied by a UV-Vis spectrophotometer. The photocatalytic enhancement mechanism of graphene was studied by photoelectrochemical analysis.
Findings
The introduction of graphene expanded the range of the optical response of TiO2 nanorod arrays, improving the separation efficiency of the photogenerated electron-hole pairs, and thus dramatically increasing its photocatalytic performance.
Research limitations/implications
A simple and novel way for synthesizing GR-TiO2 nanocomposite films has enhanced the photocatalytic performance of TiO2.
Originality/value
The photocatalyst synthesized is easy to separate and recycle in the process of photocatalytic reaction, so it is possible to achieve industrialization.
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Diego C. Knupp, Carolina Palma Naveira-Cotta, Adrian Renfer, Manish K. Tiwari, Renato M Cotta and Dimos Poulikakos
The purpose of this paper is to employ the Generalized Integral Transform Technique in the analysis of conjugated heat transfer in micro-heat exchangers, by combining this hybrid…
Abstract
Purpose
The purpose of this paper is to employ the Generalized Integral Transform Technique in the analysis of conjugated heat transfer in micro-heat exchangers, by combining this hybrid numerical-analytical approach with a reformulation strategy into a single domain that envelopes all of the physical and geometric sub-regions in the original problem. The solution methodology advanced is carefully validated against experimental results from non-intrusive techniques, namely, infrared thermography measurements of the substrate external surface temperatures, and fluid temperature measurements obtained through micro Laser Induced Fluorescence.
Design/methodology/approach
The methodology is applied in the hybrid numerical-analytical treatment of a multi-stream micro-heat exchanger application, involving a three-dimensional configuration with triangular cross-section micro-channels. Space variable coefficients and source terms with abrupt transitions among the various sub-regions interfaces are then defined and incorporated into this single domain representation for the governing convection-diffusion equations. The application here considered for analysis is a multi-stream micro-heat exchanger designed for waste heat recovery and built on a PMMA substrate to allow for flow visualization.
Findings
The methodology here advanced is carefully validated against experimental results from non-intrusive techniques, namely, infrared thermography measurements of the substrate external surface temperatures and fluid temperature measurements obtained through Laser Induced Fluorescence. A very good agreement among the proposed hybrid methodology predictions, a finite elements solution from the COMSOL code, and the experimental findings has been achieved. The proposed methodology has been demonstrated to be quite flexible, robust, and accurate.
Originality/value
The hybrid nature of the approach, providing analytical expressions in all but one independent variable, and requiring numerical treatment at most in one single independent variable, makes it particularly well suited for computationally intensive tasks such as in optimization, inverse problem analysis, and simulation under uncertainty.
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Swee-Yong Pung, Yim-Leng Chan, Srimala Sreekantan and Fei-Yee Yeoh
The purpose of this study is to synthesize a semiconductor photocatalyst which responds to both UV light and visible light in removal of organic dyes.
Abstract
Purpose
The purpose of this study is to synthesize a semiconductor photocatalyst which responds to both UV light and visible light in removal of organic dyes.
Design/methodology/approach
ZnO nanoparticles were pre-synthesised via sol-gel method using zinc nitrate tetrahydrate and methanamine at 90°C for 20 h. Subsequently, the as-synthesised ZnO nanoparticles were filtered, washed and dried. To synthesize ZnO-MnO2 core shell nanocomposites (CSNs), 2:3 M ratio of KMnO4 and MnSO4 solution was stirred for an hour. Next, ZnO nanoparticles were added into the solution. The solution was heated at 160°C for 3 h for the formation of ZnO-MnO2 CSNs. The structural, optical and photocatalytic properties of ZnO-MnO2 CSNs were characterised by field emission scanning electron microscope, transmission electron microscopy (TEM), X-ray diffractometer and PL spectroscopy, respectively.
Findings
The photodegradation efficiencies of rhodamine B (RhB) dye by ZnO-MnO2 CSNs as photocatalysts are 87.1 per cent under UV irradiation and 76.6 per cent under visible light irradiation, respectively. Their corresponding rate constants are 0.016 min−1 under UV irradiation and 0.013 min−1 under visible light irradiation. It can be concluded that N-deethylation was the dominant step during the photodegradation of RhB dye as compared to cycloreversion. The ZnO-MnO2 CSNs demonstrated good photostability after three consecutive runs.
Originality/value
ZnO-MnO2 CSN photocatalyst which could response to UV and visible light in degradation of RhB dye was synthesised using sol-gel method. The analysis shows that N-deethylation was the key photodegradation mechanism of RhB by ZnO-MnO2 CSN.
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