Optimization of bright, highly flexible, and humidity insensitive porphyrin-based oxygen-sensing materials

There is a strong demand for reliable oxygen sensors in the fields of fitness tracking, health monitoring, and medical diagnostics. Recently, oxygen-sensing materials based on phosphorescence quenching by oxygen have...

Characterization of Response Frequency for the Pressure-Sensitive Paint Based on Fluorine-Containing Polymer Matrixes Using Oscillating Sound Wave Technique

Five kinds of new homo-polymer and copolymers of methacrylate containing a fluorine ester group were synthesized and used for the binder of pressure-sensitive paint (PSP)to ensure the good compatibility between luminophore (Pt(II) meso-tetra (pentafluorophenyl) porphine (PtTFPP)) and polymer binder. In the work, we were concerned with how the structure of thesepolymers containing fluorine, especially the various ester group structure, affects the response frequency of PSP using oscillating sound wave technique. The results showed that the pressure sensitivities (Sp) of these PSP samples containing different polymers, exhibit some difference. The length of ester chain on the methacrylatepolymer affects the response frequency of PSP sensor layer composed of the polymer. The longer the chain length of the ester group, the higher the response frequency of the PSP sensor layer quenching by oxygen.

Photooxidation of Cyclohexane by Visible and Near-UV Light Catalyzed by Tetraethylammonium Tetrachloroferrate

Tetraethylammonium tetrachloroferrate catalyzes the photooxidation of cyclohexane heterogeneously, exhibiting significant photocatalysis even in the visible portion of the spectrum. The photoproducts, cyclohexanol and cyclohexanone, initially develop at constant rates, implying that the ketone and the alcohol are both primary products. The yield is improved by the inclusion of 1% acetic acid in the cyclohexane. With small amounts of catalyst, the reaction rate increases with the amount of catalyst employed, but then passes through a maximum and decreases, due to increased reflection of the incident light. The reaction rate also passes through a maximum as the percentage of dioxygen above the sample is increased. This behavior is due to quenching by oxygen, which at the same time is a reactant. Under one set of reaction conditions, the photonic efficiency at 365 nm was 0.018 mol/Einstein. Compared to TiO2 as a catalyst, Et4N[FeCl4] generates lower yields at wavelengths below about 380 nm, but higher yields at longer wavelengths. Selectivity for cyclohexanol is considerably greater with Et4N[FeCl4], and oxidation does not proceed past cyclohexanone.

Reversible oxygen addition on a triplet sensitizer molecule: protection from excited state depopulation

The molecular “chaff-flares” strategy for the protection of the triplet excited state from quenching by oxygen.

Influence of Atmospheric Gases Present in the Pores of MCM-41 on Lifetime of Ortho-Positronium

The modification of the extended Tao-Eldrup model accounting ortho-positronium quenching in air is presented. Taking into account quenching by oxygen molecules adsorbed on the surface of porous material gives reasonable agreement between results of the model and the experimental positron annihilation lifetime spectroscopy data. Pore size distributions calculated using this model from the spectra for MCM 41 mesoporous sieve obtained in air, oxygen or vacuum are compared and discussed taking into account effect of ortho-positronium migration from small open pores to the larger ones. The rates of ortho-positronium quenching by air (47.2 µs-1 MPa 1), oxygen (220 µs-1 MPa-1) or nitrogen (1.7 µs-1 MPa-1) obtained from pressure dependences of the lifetimes observed in MCM 41 agree reasonably with the experimental results of other authors, if the correction for oxygen adsorbed on the surface is applied.

Study of Pressure Sensitive Coating Using Palladium Octaethylporphyrin as Luminescent Molecule

Pressure sensitive paint (PSP) has become a useful tool to measure the surface pressure distribution of aerodynamic components replacing conventional pressure taps. For the PSP technique based on the luminescence quenching by oxygen, improvement of its sensitivity is important. In this study, we synthesized palladium octaethylporphyrin (PdOEP) as luminophor and embeded PdOEP in polydimethylsiloxane (PDMS) as polymeric binder to make up of pressure sensitive paints. We used UV/Vis spectrometer and spectrofluorimeter to study the absorption and phosphorescence spectra of PdOEP. In addition, by our self-made experimental setup, the sensitivity of PSPs were examined especially in the range of pressure below 150 Pa. As a result, it is clarified that the PSP using PdOEP as a luminophore and using PDMS as a binder has very high sensitivity to oxygen pressure in low pressure conditions below 150 Pa.