Title of article :
Tailoring the pH response range of fluorescent-based pH sensing phases by sol–gel surfactants co-immobilization
Author/Authors :
Sلnchez-Barragلn، نويسنده , , I. and Costa-Fernلndez، نويسنده , , J.M. and Sanz-Medel، نويسنده , , A.، نويسنده ,
Issue Information :
روزنامه با شماره پیاپی سال 2005
Abstract :
New fluorescence optical sensing phases for pH measurements have been developed, based on the use of 2′,7′-dibromo-5′-(hydroxymercuri)fluorescein (mercurochrome) as the fluorescent pH indicator. Fluorescence emission of mercurochrome changes reversibly with the pH in a relatively wide range of pH. The pH sensing material has been prepared by trapping this fluorescent dye in a rigid inorganic matrix prepared following the sol–gel technology. The resulting sensing phase showed a strong pH dependence (λex = 528 nm, λem = 549 nm) over 6 pH units, with reversible fluorescent changes.
-immobilization of different surfactants and mercurochrome in the sol–gel matrix has been evaluated for tuning the apparent pKa of the luminescent pH indicator and thus the sensing response. In this vein, a wide variety of surfactants of different nature (cationic, anionic, zwitterionic and non-ionic) were tested. Incorporation of surfactants induces large pKa shifts of the sensing phase depending on the nature of the co-immobilized surfactant. Using three of such mercurochrome pH sensing phases, each of them covering a different range of pH, pH-reversible sensing between pH 1–9, with response times in the order of about 1 min, could be accomplished.
ng-term stability of the sensing materials was established over at least eight months, when stored in the absence of light. Additionally, transmission electron microscopy (TEM) analysis of the sol–gel sensing phases to investigate the effect of surfactants immobilization on the microscopic sol–gel structure has also been carried out.
plicability of the synthesized sensing phases has been tested for pH analysis in several mineral and tap water samples. The results obtained showed good agreement with the corresponding pH values provided by a commercial glass electrode.
Keywords :
pH sensing , fluorescence , Surfactants , Sol–gel technology
Journal title :
Sensors and Actuators B: Chemical
Journal title :
Sensors and Actuators B: Chemical