Архивы рубрики ‘Chemistry’

Colour and the Environment

Over the last few decades, society has become increasingly sensitive towards the protection of the environment. We have developed a concern over a range of issues, amongst the most extensively debated being the destruction of the rain forests, global warming and the depletion of the ozone layer. Over this period, the chemical manufacturing industry has […]


Electrochromic dyes, as the name implies, are dyes which undergo a colour change as a result of the application of electrical energy. These dyes are of obvious interest because of their potential for application in displays. One approach to the production of electrochromic displays involves the chemistry illustrated in Scheme 10.5. This approach makes use […]


Photochromism is generally regarded as the reversible interchange of a single compound between two molecular states, which show different absorption spectra when activated by light. Most commonly, reversible photochromism follows the general principles illustrated in Scheme 10.3 in which structure A (usually colourless) is converted by irradiation with light of a certain wavelength (usually in […]


Thermochromism is the term used to describe a change of colour as a result of a temperature change. Thermochromic dyes and pigments find application where this colour change is used to indicate a temperature change, for example in plastic strip thermometers, medical thermography and non-destructive testing of engineered articles and electronic circuitry. They may also […]


Chemichromism is a term which has been introduced to describe a change in colour, caused by a chemical conversion, induced by some external stimulus, for example exposure to light, heat or electric current. Examples of these phenomena have been well known for many years but, for many traditional applications such as dyes applied to textiles, […]

Photodynamic Therapy

Arguably the most significant recent medical development which in­volves the use of dyes is photodynamic therapy (PDT). PDT is a treat­ment for cancer that uses a combination of laser light, a photosensitising compound (the dye), and molecular oxygen. In this treatment, the photo — sensitiser is given intravenously to the patient and some time is […]


One of the most common uses of dyes in biology and medicine is as staining agents. The role of such agents is in the selective coloration of certain biological features, which may be used to aid their characterisa­tion. These techniques sometimes involve well-established dyes, but fre­quently make use of coloured derivatives synthesised for a specific […]

Ink-jet printing

Ink-jet printing is currently experiencing tremendous growth. It is a non-impact means of generating images which involves directing smalldroplets of ink in rapid succession, under computer control, onto the substrate. There are a number of types of ink-jet printing methods. Two of the principal types are the continuous jet method and the impulse or ‘drop […]


The term electrophotography encompasses the familiar techniques of photocopying and laser printing. In these printing systems, the ink is a toner, which is generally a powder consisting mainly of pigment, charge control agent, and a low melting binder. Toner printing systems use optical or electrical methods to form an electrostatic latent image to which the […]


The term reprography was first used around the 1960s to encompass the new imaging techniques, including xerography, electrofax and thermog­raphy, which were emerging at the time for document reproduction. Reprographics still refers to those newer imaging processes which may be distinguished from conventional printing techniques, such as lithogra­phy, flexography and gravure printing, and traditional silver […]