Sensing Characteristics to Acid Vapors of a TPPS Coated Fiber Optic: A Preliminary Analysis
In this work we report on preliminary analysis of a novel optoelectronic gas sensor based on an optical fiber integrated with a tetrakis(4-sulfonatophenyl)porphyrin (TPPS) thin film. The sensitive materials are selectively deposited on the core region of a fiber tip by UV light induced deposition technique. A simple and cheap process which can be easily extended to different porphyrin derivatives. When the TPPS film on the fiber tip is exposed to acid and/or base vapors, dramatic changes occur in the aggregation structure of the dye molecules in the film, from Jto H-type, resulting in a profound modification of their corresponding reflectance spectra. From the achieved experimental results it is evident that the presence of intense and narrow band peaks in the reflected spectra could be monitored to detect hazardous vapors. Keywords—Optical fiber sensor, Porphyrins, Thin films UVinduced deposition, TPPS.
Layer-by-Layer Growth of Electrostatically Assembled Multilayer Porphyrin Films
The feasibility of preparing multilayer porphyrin films with monolayer control of composition and thickness is demonstrated. Successive dip-coating of tetraruthenated zinc porphyrin, [ZnTPyPBpy]4+, and meso-tetraphenylporphyrin sulfonate, [M-TPPS]4-, is shown to result in linear growth of the film thickness (12.7(6) A/bilayer) and optical absorbance as a function of the number of bilayers. These results strongly suggest a layer-by-layer assembly of compositionally homogeneous films of up to 30 bilayers. The assembled multilayer composite films have been characterized by UV−vis spectroscopy, scanning electron microscopy, X-ray photoelectron spectroscopy, atomic force microscopy, and electrochemical methods. Electrodes modified with these films exhibit a reversible wave at 0.94 V and are photocatalytically active toward the reduction of O2. Our findings suggest that the layer-by-layer growth method may be a general route to compositionally modulated porphyrin films of arbitrary thickness and rationally tail...
Guest Conformation and Diffusion into Amorphous and Emptied Clathrate Phases of Syndiotactic Polystyrene
The sorption kinetics of 1,2-dichloroethane (DCE) (pure or dissolved in water at different concentrations) in amorphous and semicrystalline syndiotactic polystyrene films are studied by Fourier transform infrared spectroscopy. Experiments at low DCE concentrations show that the DCE sorption in empty clathrate samples is much faster and leads to much higher sorption equilibrium values than that in the amorphous or other semicrystalline samples. The results of the sorption experiments into emptied clathrate polymer samples can be interpreted by assuming that DCE, for low concentrations in aqueous solutions, is mainly absorbed by the clathrate phase and that, as guest molecule in the polymeric clathrate, it is substantially only in the trans conformation. In the assumption that the guest DCE molecules in the clathrate are present only in the trans conformation, the kinetics of clathration in the emptied clathrate phase and of sorption in the amorphous phase are separated.