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Luminescent oxygen sensor composed of platinum-porphyrin and a gas-permeable polymer binder was applied as an optical crack sensor paint for infrastructure. The sensor paints were designed as a three-layered structure in which the luminescent oxygen sensor layer was sandwiched between oxygen barrier layers. The sensor paints emitted intense luminescence under UV light irradiation, and the luminescence was efficiently quenched when a new crack formed on the concrete surface. Microcracks, which were

CO2 capture-reduction (CCR) is a recently developed catalytic process that combines two critical functions of the CO2 utilization path in one process, namely CO2 capture and subsequent transformation (e.g. reduction by H2) into chemical fuels or intermediates such as CO. A bifunctional catalyst material is needed and the two functions are activated by means of an isothermal unsteady-state operation (i.e. gas switching). This work employs operando space- and time-resolved DRIFTS, XAFS, and XRD to elucidate the nature and functions of Cu and the promoters. Both unpromoted and K/Ba-promoted Cu/Al2O3 catalysts were studied to illuminate the active surface species varying along the catalyst bed. The K promoter was found to uniquely facilitate efficient CO2 capture in the form of surface formates, dispersion of active metallic Cu and suppression of surface Cu oxidation. The CO2-trapping efficiency of the K-promoted catalyst is so high that CO2 capture takes place gradually along the catalyst bed towards the reactor outlet, hence creating large spatial and temporal gradients of surface chemical species. Understanding these features is of central importance to design efficient CCR catalysts. Furthermore, a completely different path for CO2 reduction was evidenced for the unpromoted and Ba-promoted Cu catalysts where CO2 can directly react with metallic Cu and oxidize its outer surface and thus releasing CO. These results also provide important new mechanistic insights into the widely investigated reverse water–gas shift reaction and the role that K and Ba promoters play.

During start-up/shut-down processes of a polymer electrolyte fuel cell, platinum particles are lost from the catalyst layer at the cathode due to corrosion of the carbon supports. We simulated the start-up/shut-down cycle by exchanging gases at the anode between hydrogen and air. During the gas exchange, the distribution of oxygen partial pressures at the anode was visualized by our real-time/space visualization system, which clearly showed the location of H2- and O2-rich areas along the gas-flow channel from the inlet to the outlet. The gas exchange rate was found to be much slower than that predicted from the simple replacement and to be correlated to the proton transfer derived from carbon corrosion of the cathode catalyst layer. By the visualization results, it was found that the shut-down process gives more serious effect than the start-up process. After the degradation, the oxygen partial pressure at the cathode was visualized during the cell operation. Oxygen was consumed mainly in the middle of the MEA because the MEA was degraded mainly near the inlet and outlet of reactant gases in the cell.

Luminescent oxygen-sensory polymer-coatings composed of platinum tetrakis(pentafluorophenyl)-porpholactone (PtPL) and -porphyrin (PtPP) with poly(trimethylsilylpropyne) (PMSP) were prepared for visualization of the oxygen partial pressure on two parallel planes or a biplanar surface. PMSP formed a smooth and tough coating as a high oxygen-permeable polymer matrix with a thickness of ca. 2 μm, which homogeneously contained the luminescent dye probe, PtPL or PtPP. Under UV light (395 nm) irradiation, the coatings displayed strong magenta and red luminescence with maximum peaks at 750 and 650 nm ascribed to the PtPL and PtPP, respectively. The luminescence of the two coatings was efficiently quenched by oxygen which allowed the development of engineering curve to analyze the oxygen partial pressure. The luminescence intensities of the two coatings were separately monitored in order to allow the simultaneous measurement of the oxygen partial pressure distribution upon two planar surfaces.

Active control of flow over object surfaces achieved by means of mechanical and/or electrical methods has recently been studied. However, there has been no report on actively switching the surface drag of an object by chemical modification of the object's surface. Poly(N-isopropylacrylamide) (PNIPA) was grafted onto the surface of an aluminium (Al) substrate via (A) surface-initiated atom transfer radical polymerization and (B) radical polymerization with an azo-group surface initiator. The grafting density was 0.19 and 0.15 chains nm−2, respectively. The water contact angle of the PNIPA-grafted Al surface reversibly changed between 55° and 82° for (A) and between 42° and 65° for (B) at temperatures of 25 and 40 °C, which was ascribed to the temperature-responsive, hydrophilic–hydrophobic switching of the grafted PNIPA surface. The PNIPA grafting was applied on the surface of an ogive-shaped Al model. The normalized dropping speed of the model in water increased 1.1 times at 42 °C in comparison to that at 22 °C. Switching of the surface drag of PNIPA-grafted Al in water was demonstrated on the basis of the hydrophilicity and hydrophobicity of the grafted Al surface, the switching occurring with a change in temperature. Copyright © 2010 Society of Chemical Industry

Poly[1-trimethylsilyl-1-propyne-co-1-(3-pyridyl)propyne] 1 was prepared both as a polymer-ligand of a palladium porphyrin (PdOEP) and of a platinum porphyrin (PtTFP) and as a highly gas-permeable polymer matrix of the porphyrin. The porphyrin acted as a phosphorescence probe which could be quenched with oxygen and sense the oxygen partial pressure. 1 gave a smooth and tough coating with a thickness of ca. 2 µm which homogeneously involved the porphyrin. The porphyrin-1 coatings displayed strong red-colored phosphorescences (the emission maximum at 670 and 650 nm for PdOEP and PtTFP, respectively), and their intensity significantly decreased with an increase in the oxygen partial pressure on the coating. The high oxygen-quenching efficiency or the high oxygen pressure sensitivity of the porphyrin's phosphorescence was observed even at cryogenic temperature. Aggregation of the porphyrin was suppressed in the coating by ligation of the porphyrin with the nitrogenous residue of 1 to significantly reduce spatial noise in the phosphorescence measurement or the oxygen-pressure sensing. PtTFP-1 was coated on the surface of a delta wing model. The oxygen-pressure distribution on the coated model was successfully visualized in a cryogenic wind tunnel test. Copyright © 2008 John Wiley & Sons, Ltd.

Fuel cells are devices that produce electric power by means of the chemical reaction of oxygen and fuels more efficiently than current technologies, and they are expected to become a cleaner source of energy. Despite considerable recent advances, especially in polymer electrolyte membrane fuel cells (PEMFCs), existing technology still has drawbacks, including kinetic limitations on the oxygen reduction reaction and the instability of Pt catalysts and polymer membranes nearby, in particular during startup–shutdown cycles. The chemical reactions are uneven throughout the reaction field and not well understood. A central issue in fuel cell research is the measurement of the parameters that determine performance during cell operation, a difficult task owing to the structure of these devices. The distribution of liquid water in operating fuel cells has been measured and imaged through neutron radiography, by NMR spectroscopy, and by X-ray microtomography, and temperatures have been recorded with a thermograph. Hydrogen cross-over from the anode to cathode has been studied by mass spectrometry and magnetic resonance imaging in an operating PEMFC. Oxygen consumption and H2O2 formation, as well as the local catalytic activity of a catalyst have been investigated and visualized in solution with a scanning electrochemical microscope. However, to improve the performance and durability of PEMFCs, it is crucial to understand distributions in real time not only of liquid water but also of reactants and products (oxygen, fuel, CO2, water vapor, etc.) throughout the cell. Here we present a laboratoryuse, nondestructive system for visualizing oxygen distribution in the interior of the operating fuel cells which relies on dye films painted on the transparent gas flow field. Oxygen partial pressures were successfully visualized with spatial and time resolutions of 300 mm and 500 ms, respectively. We found that the oxygen distribution in PEMFC is not in accordance with that expected based on the current, which suggests a significant contribution from water. This imaging system is applicable to other important parameters such as water, carbon monoxide, and temperature, and should help in the design of new fuel cell separators and a reaction field called a membrane-electrode assembly (MEA). An oxygen-sensitive porphyrin, tetrakis(pentafluorophenyl)porphyrinatoplatinum (PtTFPP), was used in the visualization system. This dye complex was dispersed in an oxygenpermeable polymer matrix, poly(1-trimethylsilyl-1-propyne) (pTMSP), for making a thin, water-insoluble dye film. To understand the properties of the dye film, we placed the film in an environment with controlled oxygen partial pressure (mixtures of oxygen, nitrogen, and water vapor at 0–26 kPa of a total of approximately 101.3 kPa), temperature, and humidity, and irradiated it with a laser light at a wavelength of 407 nm. The emission from the film was filtered (> 600 nm), and the intensity was measured with a charge-coupled device (CCD) camera. Figure 1a shows a Stern–Volmer plot of the

We describe the capsulation of colloidally templated polythiophene (P3-TAA) arrays with multi-walled carbon nanotubes (MWNTs) after colloidal template electropolymerization. The dissolution of the polystyrene (PS) particle templates, which were assembled via the Langmuir-Blodgett (LB)-like technique, allowed the formation of hollow-shell Janus type arrays.

A dual-mode and a non-Stern–Volmer type oxygen pressure-sensitive coating was prepared by combining the cobaltporphyrin (CoP) ligated with a polymer and 1-pyrenebutyric acid (Py): the combination of the rapid and reversible oxygen (O2)-adduct formation of the CoP was accompanied by a visible absorption spectral change and luminescence quenching of Py with oxygen. The oxygen sensor composed of CoP/Py was successfully characterized by a significantly high oxygen sensitivity under the practical atmospheric oxygen pressure of 10–21 kPa. Py was adsorbed on an anodized aluminium substrate. Its luminescence decreased by quenching with oxygen which obeyed the conventional Stern–Volmer equation. Copolymers of vinylidenechloride with 1-vinylimidazole, 1-vinyl-2-methylimidazole, and 4-vinylpyridine (1, 2 and 3, respectively) were prepared to provide both an oxygen-barrier coating for the first luminescent Py layer and CoP ligation for tuning the oxygen-adduct formation equilibrium. The luminescent Py layer was further coated with a second polymer layer: The oxygen-barrier polymer coating enhanced the Stern–Volmer type luminescence intensity from the Py layer. Visible absorption of the CoP-containing polymer second layer increased in response to the oxygen-adduct formation or oxygen partial pressure, which overlapped and reduced the luminescence from the Py layer. The sum of the luminescence decreased along with an increase in the oxygen partial pressure, yielding a non-Stern–Volmer type response or high sensitivity to the oxygen partial pressure.