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Oxygen sensing materials based on clay/metalloporphyrin hybrid systems

100%
Čeklovský A., Takagi S.
Open Chemistry
|
2013
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vol. 11
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issue 7
1132-1136
EN
This study was focused on the investigation of novel hybrid organo/inorganic systems for oxygen sensing applications. As a host material, a synthetic clay mineral Sumecton SA was chosen, while, as guest materials, metalloporphyrins containing Pt(II) and Pd(II) were chosen. These are known to be very efficient agents for sensing applications because of a “heavy atom effect”. This effect promotes a spin-orbit coupling, resulting in the fact that almost all of the radiation from a singlet excited state undergoes intersystem crossing, followed by a de-excitation via a triplet state. The combination of metalloporphyrin and layered materials enables unique oxygen sensing properties due to the steric effects of layered materials. The result is that the emission from the membrane was sensitive at the range around aerobic conditions. The spectroscopic analysis of hybrid systems - clay/porphyrin membranes (CPMs) showed that these materials can serve as prospective candidates for the construction of effective, reliable and economical oxygen sensors. [...]
2
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Spectral study on the molecular orientation of a tetracationic porphyrin dye on the surface of layered silicates

81%
Čeklovský A., Bujdák J., Czímerová A., Iyi N.
Open Physics
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2007
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vol. 5
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issue 2
236-243
EN
Tetracationic porphyrin dyes TMPyP and ZnPyP were intercalated into hydrophobized layered silicate films of three smectites. The smectites represented the layered silicate specimens of high (Fluorohectorite, Corning; FHT), medium (Kunipia F montmorillonite; KF) and low layer charge (Laponite, Laporte; LAP). The molecular orientations of the dye cations were studied by means of linearly-polarized ultraviolet-visible (UV-VIS) spectroscopy. The spectral analysis and consequent calculations of tilting angles of the transition moments at the wavelengths of Soret band transitions were in the range of 25°-35°. The determined angles indicated molecular orientation of the dye cations being almost parallel to the surface of the silicates. Slightly higher values (above 35°), determined for a FHT film, indicated either a slightly tilted orientation of the dye cations or the change of molecular comformation after the intercalation of the dye.
3
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Interaction of montmorillonite with phenothiazine dyes and pyronin in aqueous dispersions: A visible spectroscopy study

81%
Czímerová A., Čeklovský A., Bujdák J.
Open Chemistry
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2009
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vol. 7
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issue 3
343-353
EN
Layer charge is one of the key parameters used for the characterisation of expandable clay minerals, smectites. It determines most significant properties of the material which are important from the industrial application point of view. This work is related to a novel method introduced to characterize the layer charge of smectites, based on using cationic organic dyes as molecular sensors. One xanthene and four phenothiazine cationic dyes were tested using reduced charge montmorillonites (RCMs) and compared with methylene blue, which has been used most frequently. The characterization of the charge was based on the formation of molecular assemblies (H- and J-aggregates) composed by dye cations, which were easily detectable using absorption spectroscopy in the UV/VIS spectrum. More detailed characterization of the spectra required calculations of second-derivative curves. For all of the reaction systems tested in this work, the molecular aggregation increased with the layer charge of RCMs. Slight to moderate differences in the formation of dye assemblies related to the differences in the molecular structures of the individual dye cations. For example, the molecular asymmetry of azure A brought about the formation of coexistent species of similar structures. The structure of the heteroaromatic skeleton affected the extent of the aggregation and spectral changes with time. The presence of reactive, non-substituted amino groups in thionine cations probably partially decomposed in the clay mineral colloids based on high-charge RCMs. Any of the tested dyes could be used as molecular sensors for empirical characterization of the layer charge of clays taking into account the differences mentioned above. [...]
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