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Dyes and Auxiliaries for Textile Printing
Published in Asim Kumar Roy Choudhury, Principles of Textile Printing, 2023
Metal-complex dyes depend on formation of co-ordinate links between the dye and metal. The co-ordinate link occurs with atoms such as oxygen and nitrogen having a lone pair of electrons in the outer shell, which can be shared by another atom. In covalent bond, on the other hand, each atom contributes one electron. Thus, with two atoms A and B, the two types of bond formations may be shown as follows (Equations 3.1 and 3.2): Covalent bond,A⋅+⋅B→A:BCoordinate bond,A:+B→A:B The final result is the same, but the mode of formation is different.
Textile Wastewater
Published in Arun Kumar, Jay Shankar Singh, Microalgae in Waste Water Remediation, 2021
There are many sources of heavy metals in textile wastewater: chemicals, salts and dyes which are frequently applied during the bleaching and dyeing textile process. Some bleaching chemicals like caustic soda, sodium carbonate and other salts contain mercury heavy metals as impurities, that could be discharged into wastewater. Some metalized mordant dyes are also responsible for heavy metal discharge in the wastewater stream. As it discussed earlier in the tannery industry, most of the metal complex dyes contain a chromium base; from which chromium could be easily released into wastewater.
Recent Trends in Nanomaterial-Based Advanced Oxidation Processes for Degradation of Dyes in Wastewater Treatment Plants
Published in Maulin P. Shah, Sweta Parimita Bera, Günay Yıldız Töre, Advanced Oxidation Processes for Wastewater Treatment, 2022
Samuel S. Mgiba, Vimbai Mhuka, Nomso C. Hintsho-Mbita, Nilesh S. Wagh, Jaya Lakkakula, Nomvano Mketo
Metal complex dyes are other types of dyes that are a combination of dye molecule and metal salt, generally chrome and other transition metals. These dye compounds are also known as pre-metallized dyes [13]. The structure of these dyes is usually a monoazo structure that consists of different groups such as hydroxyl, carbonyl and amino groups. When dyeing using metal complex dyes, a pH regulator, electrolytes and levelling agents in the form of ionic and nonionic surfactants are used as chemicals and auxiliaries. The metals can also be found in waste due to unfixed dye [13].
First-principles study on the effect of micro-modified D-A-π-A dyes with triphenylamine acting as a donor on its photoelectric properties
Published in Molecular Physics, 2020
Jiameng Cao, Xianbin Zhang, Shihan Zhao, Haohao Ma, Xuyan Wei
Since 1991, DSSCs have been proposed by the Grätzel research group for the first time. The advantages of green, environmentally friendly, low cost, simple preparation, and proper light absorption make researchers reward DSSCs with more attentiveness [1,2]. The structural components of DSSCs mainly include semiconductor oxide nanoporous membranes, dye sensitisers, and electrolytes, and counter electrode compositions [3]. The dye sensitisers are the core components of the entire DSSCs and play a vital role in achieving a high photoelectric conversion efficiency of DSSCs. In order to further improve the photoelectric conversion efficiency of DSSCs and fully utilise the light energy, a series of a new roles of high-efficiency dye molecules have stood on the stage of DSSCs. So far, these high-efficiency dye molecules mainly include zinc porphyrins [4,5], Ru complex sensitisers [6,7] and pure organic dye molecules, in which Ru complex sensitisers (N3, N719, and black dye) are representative. Ru complex sensitisers have been reported to have high power conversion efficiencies surpassed 11% and 10% respectively, under AM 1.5G irradiation [8]. Although metal complex dyes currently recognised as the photosensitizers for the most efficient photoelectric conversion, such dyes are expensive because of the presence of precious metals. In order to achieve a win-win situation in cost and light conversion efficiency, most researchers have focused their researches on pure organic dyes in recent years. At present, the most efficient pure organic dyes are constructed by using the electron donor (D)-conjugated bridge (π)-electron acceptor (A) configuration due to the D-π-A structure possess a kind of ‘push-pull’ that facilitates efficient separation of charges [9]. Among them, the triphenylamine dye sensitiser is famous for its strong electron-donating ability and excellent hole transporting property because of its central nitrogen atom. In addition, the triphenylamine as a non-planar arylamine compound with a propeller space structure has a tremendous steric hindrance thereby improves the stability of dye molecules [10]. Therefore, triphenylamine derivatives widely used as electron donors.
Enhanced photovoltaic performances of C219-based dye sensitisers by introducing electron-withdrawing substituents: a density functional theory study
Published in Molecular Physics, 2020
Caibin Zhao, Qiang Zhang, Xiaohu Yu, Ke Zhou, Lingxia Jin, Wenliang Wang
Fast growth in energy demand and gradual depletion of fossil fuels have increased the widespread interests of scientists to explore and develop renewable energy sources that are environmentally sound, such as wind power, hydropower, geothermal energy, biomass, and solar energy [1]. In numerous renewable energy sources, solar energy is undoubtedly an ideal alternative owing to its abundance, convenience, and cleanliness [2,3]. Generally, the solar-to-electrical energy conversion is an efficient and economic mode that applies the solar energy. At present, several photovoltaic devices have been developed and applied. Among them, photovoltaic devices based on conventional silicon-based materials have been commercialised, while the other photovoltaic technologies are still in development. As one of the most promising photovoltaic technologies, dye-sensitised solar cells (DSSCs) in the past twenty years have received intense concerns due to its several remarkable advantages, such as lightweight, low production cost, raw materials, and simple production process [4]. Typical DSSC devices include four important components: anode, cathode, electrolyte, and dye sensitiser. Among these components, it is no doubt that the dye sensitiser is the most critical one. Therefore, the design and synthesis of high-performable dyes are very important to develop new generation DSSC devices. Currently, dye sensitisers used in DSSC devices can be classified into two main categories. One is metal complex dyes, such as Ru (II) and metalloporphyrin complexes. These dyes usually have better harvesting of solar radiation. So DSSC devices based on metal complex dyes generally possess good photovoltaic performances. Recently, the DSSC device with porphyrin dyes as sensitiser has reported to achieve the highest photoelectric conversion efficiency (PCE) of 13% [5]. However, the metal complex dyes have obvious drawbacks, such as expensive price, complicated preparation process, undesirable environmental impact, and low synthetic yield, which make their future look less promising from large-scale applications [6]. Another is metal-free organic dyes. Comparatively, metal-free organic dyes overcome the above-mentioned deficiencies of metal complex dyes and have received more attention in most recent years. Especially, through the continuous material innovation and device engineering, the highest PCE of DSSC based on metal-free organic dyes has reached up to 12.6% [7], which is even comparable to that of DSSC sensitised by metal complex dyes. These results indicated that DSSC technology based on metal-free organic dyes has been gradually mature, and has promising application prospect. Many studies pointed out that the good metal-free dyes should have a wide optical absorption in ultraviolet–visible (UV–VIS) light region with high molar extinction coefficients to absorb sunlight as possible, and suitable frontier molecular orbital (FMO) levels that match the reduced couple potential and conduction energy level of the semiconductor to ensure efficient electron injection and fast dye regeneration, which are crucial for DSSC devices [8].