The first use of electrospun nanofibrous materials as highly responsive fluorescence quenching-based optical CO(2) sensors is reported. Poly(methyl methacrylate) and ethyl cellulose were used as polymeric materials. Sensing slides were fabricated by electrospinning technique. A fiber-optic bundle was used for the gas detection. CO(2) sensors based on the change in the fluorescence signal intensity of ion pair form of 8-hydroxypyrene-1,3,6-trisulfonic acid (HPTS). The sensor slides showed high sensitivities due to the high surface area-to-volume ratio of the nanofibrous membrane structures. The preliminary results of Stern-Volmer analysis show that the sensitivities of electrospun nanofibrous membranes to detect CO(2) are 24 to 120 fold higher than those of the thin film based sensors. The response times of the sensing reagents were short and the signal changes were fully reversible. The stability of ion pair form of HPTS in the employed matrix materials was excellent and when stored in the ambient air of the laboratory there was no significant drift in signal intensity after 7 months. Our stability tests are still in progress.

In this study we have employed two ionic liquids (ILs) as a new media for the analysis of aluminum in aqueous solutions by spectrofluorimetric method. ILs are liquid salts and they have no measurable vapor pressure up to their thermal decomposition point, >300 °C. This lack of vapor pressure makes these materials highly attractive for many studies as they can be used as clean solvents. Besides they are promising environments for analysis purposes and optical sensor designs. The results revealed that absorption, excitation and emission spectra of the morin-Al complex exhibited considerable changes in moieties. The morin-Al complex was stable at aluminum concentrations below 9.1 mg L(-1) in 25% 1-butyl-3-methylimidazolium bromide (IL-I)-water binary mixtures. The higher concentrations of IL (>25% by volume) was not suitable for the complex formation thus in pure IL media the complex formation even at high aluminum concentrations was not observed. The complex stoichiometry ratio of aluminum:morin was 2:1 in IL-I-water binary mixtures. The linear concentration range was 0.045-7.2 mg L(-1) with a correlation coefficient of r = 0.9909. The detection limit was found to be 0.036 mg L(-1). Cu(2+), Mn(2+) and PO (4) (3-) ions exhibited less interfering effect in presence of IL-I and the tolerance limit of Cu enhanced 10 times when compared with ethanol.

ABSTRACT:The PT/PS/SiO 2 nanocomposite of polythiophene (PT), polystyrene (PS), and SiO 2 with a grain size of 100 -150 nm was synthesized by chemical polymerization using FeCl 3 oxidant in nanoqueous medium (CHCl 3 ). The properties of PT/PS/SiO 2 synthesized were compared to those of PT, PT/PS, and PT/SiO 2 synthesized in the same conditions. The synthesized materials were subsequently characterized by FTIR spectroscopy, thermogravimetric analysis (TGA), and scanning electron microscopy (SEM). The incorporation of PT in the composite was endorsed by FTIR studies. TGA revealed enhanced thermal stability of the PT/PS/SiO 2 nanocomposite compared to that of PT. SEMs showed globular particles and the presence of clusters of composite particles. The conductivity of the PT/PS/SiO 2 nanocomposite was measured as 1.30ϫ10Ϫ7 Scm Ϫ1 and the conductivity value of PT (1.02ϫ10 Ϫ4 Scm Ϫ1 ) decreased with entiring PS and SiO 2 to PT structure.

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