Optical sensors for a wide pH range based on azo dyes immobilized on a novel support

✍ Scribed by Gerhard J. Mohr; Otto S. Wolfbeis

• Publisher: Elsevier Science
• Year: 1994
• Tongue: English
• Weight: 643 KB
• Volume: 292
• Category: Article
• ISSN: 0003-2670
• DOI: 10.1016/0003-2670(94)00096-4

✦ Synopsis

New reactive azo dyes are described which are useful for optical determination of pH. The dyes are covalently linked (via ethylsulfonyl groups) to a novel type of transparent solid films consisting of a thin film of cellulose on top of a polyester support. The resulting membranes exhibit distinct color change when changing the pH and, in most cases, are compatible with LED light sources. Various membranes have been developed with pK, values ranging from 0.5 to 11.28, thus practically covering the whole pH range. Because of the stability of the dyes, the covalent bond and the solid support, the new membranes exhibit storage stability over years, and operational lifetimes of weeks, good reproducibility and a fast (30-60 s) response to pH.