HALOCHROMIC MATERIALS PDF

Chromogenic materials change colour in response to an electrical, optical e. A chromogen is a coloured compound containing a chromophore - responsible for the observed colour. A chromophore is a group of atoms within a larger molecule that are principally responsible for the absorption of visible light to give the compound its colour. The colour you observe is formed from the visible light that is transmitted or reflected by the chromogen.

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A halochromic material is a material which changes color when pH changes occur. In this case, the factor is pH. The pH indicators have this property. Halochromic substances are suited for use in environments where pH changes occur frequently, or places where changes in pH are extreme. Halochromic substances detect alterations in the acidity of substances, like detection of corrosion in metals.

Halochromic substances may be used as indicators to determine the pH of solutions of unknown pH. The colour obtained is compared with the colour obtained when the indicator is mixed with solutions of known pH. The pH of the unknown solution can then be estimated. Obvious disadvantages of this method include its dependency on the colour sensitivity of the human eye, and that unknown solutions that are already coloured cannot be used.

The colour change of halochromic substances occur when the chemical binds to existing hydrogen and hydroxide ions in solution. Such bonds result in changes in the conjugated systems of the molecule, or the range of electron flow.

This alters the wavelength of light absorbed, which in turn results in a visible change of colour. Halochromic substances do not display a full range of colour for a full range of pH because, after certain acidities, the conjugated system will not change. The various shades result from different concentrations of halochromic molecules with different conjugated systems. From Wikipedia, the free encyclopedia.

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Continue to access RSC content when you are not at your institution. Follow our step-by-step guide. A specific class herein is halochromic textiles, i. Such halochromic textiles play an important role in the continuous monitoring and visual reporting of the pH with applications in various fields, such as wound treatment and protective clothing. However, this method suffers from leaching of the dye, which is an undesirable effect that not only reduces the output signal strength but can also be detrimental to the environment by causing, for instance, toxicological responses. In this paper, a new strategy is demonstrated for the reduction of dye leaching in electrospun, nanofibrous materials. Through blend electrospinning of polyamide-6 PA6 with a dye-functionalized copolymer, large sheets of uniform, halochromic nanofibrous material can be fabricated showing a fast pH-sensitive color change.

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Halochromic Textile Materials as Innovative pH-Sensors

Recently, an increasing interest in pH-sensitive textiles is recognized. These chromic textiles can be used as flexible sensors for various applications. The aim of the current research is to develop textile pH-sensors through the application of pH-sensitive dyes on various textile materials using different techniques. The results of our study show that halochromic dyes can be incorporated into conventional textiles by a conventional dyeing technique. Also coating the fabrics with a sol-gel layer containing the halochromic dye proved to be successful. The majority of these developed materials showed a clearly visible color change with a pH-variation. The response of the sensors was dependent on the density of the fabric but was generally relatively fast, especially for the sol-gel treated fabrics.

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Halochromism

A halochromic material is a material which changes color when pH changes occur. In this case, the factor is pH. The pH indicators have this property. Halochromic substances are suited for use in environments where pH changes occur frequently, or places where changes in pH are extreme. Halochromic substances detect alterations in the acidity of substances, like detection of corrosion in metals.

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Lavrentiev Ave. Email: ur. Chromeazurol B Na 2 HL is a pH-sensitive halochromic dye based on a hydroxytriarylmethane core and two carboxylate functional groups, which makes it suitable for the synthesis of coordination polymers. Chromeazurol B anions link each tetranuclear cluster to four individual Zn ii cations and each Zn ii cation with four tetranuclear clusters. Both compounds show pH-sensitivity in water solution which can be observed visually, giving the first example of a halochromic coordination polymer.

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