A novel luminol derivative and its functionalized filter-paper for reversible double-wavelength colorimetric pH detection in fruit juice

A novel luminol derivative combining with azobenzene chromophore (LABD) and its functionalized filter-paper were developed and evaluated for double-wavelength visible pH detection for the first time. By virtue of the reversible protonation or deprotonation of amide or tertiary amino groups, the present sensors displayed high sensitivity and selectivity for reversible double-wavelength colorimetric response to pH at A433 and A529 respectively, with a wide linear recognition range between pH 4.0 and pH 11.0 and a visible color change from purple to bright yellow. After it was confirmed to be quite low-toxic to mouse fibroblast cells, LABD and its functionalized filter-paper were successfully applied to selectively detect pH in some real fruit juices with satisfied results.