TY - JOUR
T1 - Sol-Gel Physical and Covalent Entrapment of Three Methyl Red Indicators
T2 - A Comparative Study
AU - Rottman, Claudio
AU - Turniansky, Avner
AU - Avnir, David
PY - 1998/1
Y1 - 1998/1
N2 - We report the results of a comparative study of the properties of three azo dyes from the methyl red indicator family, which were coentrapped with the surfactant cetyltrimethylammonium bromide within tetramethoxysilane-derived silica sol-gel matrices. Characteristic parameters studied were spectral shifts, shifts in indicating ranges and in pKi values, isosbestic-point behavior, changes in the titration curves and stability to leaching. Physical entrapment of methyl red and para-methyl red (pMR) is compared to the covalent entrapment of a trialkoxysilane derivative of methyl red. High stability for leaching was found for all three entrapped indicators. The pKi change in entrapped pMR is interpreted in terms of intracage motion induced by pH changes.
AB - We report the results of a comparative study of the properties of three azo dyes from the methyl red indicator family, which were coentrapped with the surfactant cetyltrimethylammonium bromide within tetramethoxysilane-derived silica sol-gel matrices. Characteristic parameters studied were spectral shifts, shifts in indicating ranges and in pKi values, isosbestic-point behavior, changes in the titration curves and stability to leaching. Physical entrapment of methyl red and para-methyl red (pMR) is compared to the covalent entrapment of a trialkoxysilane derivative of methyl red. High stability for leaching was found for all three entrapped indicators. The pKi change in entrapped pMR is interpreted in terms of intracage motion induced by pH changes.
KW - CTAB
KW - Entrapment pH indicators
KW - Surfactants
UR - http://www.scopus.com/inward/record.url?scp=0032314875&partnerID=8YFLogxK
U2 - 10.1023/a:1008630701220
DO - 10.1023/a:1008630701220
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AN - SCOPUS:0032314875
SN - 0928-0707
VL - 13
SP - 17
EP - 25
JO - Journal of Sol-Gel Science and Technology
JF - Journal of Sol-Gel Science and Technology
IS - 1-3
ER -