Functional Cyan Dyes

Some cyan dyes derived from both naphthols and phenols are reported to show thermochromism, a reversible shift in the dye hue as a function of temperature. This can occur in a negative while prints are being made (65). 

To investigate the response of the optode membrane to NH4+, its absorption spectrum was monitored as a function of the NH4+ concentration after immersing the freshly prepared PVC film in 0.1 M aqueous HC1 to pro-tonate the dye. The absoption data are shown in Fig. 14. The absorption maximum shifted from 475 to 610 nm, and the color of the optode membrane changed from yellow (10-6—10 5 M) — light yellow (10 M) —> fight green (10 3 M) —> cyan (10 2 M) — blue (10-1 -1 M). The absorption spectra have a clear isosbestic point. 

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