Significant effect of surfactant micelles on pH dependent fluorescent off–on–off behavior of Salicylaldehyde-2,4-Dinitrophenylhydrazone

The fluorescence response to pH of 2,4 dinitrophenolhydrazone in 1:1 CH3OH:H2O and micellar mediums—negatively charged sodium dodecylsulphate (SDS), positively charged cetyltrimethyl ammonium bromide (CTAB) and neutral Triton X-100 (TX-100), is reported. At pH 4.0 the fluorescence of the molecule can be switched “on” by selecting CTAB as the solvent. At pH 6.0 if the medium is TX-100 the fluorescence is “off”, but remains “on” for the other three solvents. At pH 8.0, fluorescence is “on” in the solvents except CTAB. SDS and TX-100 switch the fluorescence “on” at pH 13.0 but for the other two solvents the fluorescence is “off”. ► The fluorescence response to pH of Salicylaldehyde-2,4 Dinitrophenolhydrazone in 1:1 CH3OH:H2O and in positively charged cetyltrimethyl ammonium bromide (CTAB) micellar medium shows “off–on–off” behavior. ► In negatively charged sodium dodecylsulphate (SDS) the response of fluorescence of Salicylaldehyde-2,4 Dinitrophenolhydrazone to pH is “off–on–on” type while in neutral Triton X-100 it is “off–on–1/2on” type. ► At a given pH, fluorescence of 2,4 dinitrophenolhydrazone can be made “on” or “off” by selecting an appropriate pH.