Name: development and validation of chromium getters for solid oxide fuel cell power systems
Uploaded: 2019-05-26T14:00:00
Description: Watch this Scientific Journal Video about Development and Validation of Chromium Getters for Solid Oxide Fuel Cell Power Systems at JoVE.com

Authors acknowledge financial support from U.S. Department of Energy (US DOE) under the federal grant DE-FE-0023385. Technical discussion with Drs. Rin Burke and Shailesh Vora (National Energy Technology Laboratory) is gratefully acknowledged. Drs. Amit Pandey (LG Fuel Cells, Canton OH), Jeff Stevenson and Matt Chou (Pacific Northwest National Laboratory, Richland WA) are acknowledged for their help with long term test validation of the performance of the getters. Authors acknowledge the University of Connecticut for providing laboratory support. Dr. Lichun Zhang and Ms. Chiying Liang is acknowledged for technical discussion and help with the experiments.

1. Synthesis of chromium getter
<ol>
	<li>Synthesize precursor powder using alkaline earth and transition metal oxide salts via conventional coprecipitation synthesis route as depicted in Figure 116.
	<ol>
		<li>Prepare a stock solution using 50.33 g of strontium nitrate Sr(NO3)2 and 43.97 g of nickel nitrate hexahydrate Ni(NO3)2.6H2O in order to prepare 2.4 M solutions in 100 mL of de-ionized water.&#160;</li>
...

<ol>
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C. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=La(Ni,Fe)O3+as+a+cathode+material+with+high+tolerance+to+chromium+poisoning+for+solid+oxide+fuel+cells.">La(Ni,Fe)O3 as a cathode material with high tolerance to chromium poisoning for solid oxide fuel cells.</a> Journal of Power Sources. 170, 61-66 (2007).</li><li>Aphale, A., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Synthesis+and+stability+of+SrxNiyOz+chromium+getter+for+solid+oxide+fuel+cells.">Synthesis and stability of SrxNiyOz chromium getter for solid oxide fuel cells.</a> Journal of the Electrochemical Society. 165, (2018).</li><li>Aphale, A., Hu, B., Singh, P. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Low-Cost+Getters+for+Gaseous+Chromium+Removal+in+High-Temperature+Electrochemical+Systems.">Low-Cost Getters for Gaseous Chromium Removal in High-Temperature Electrochemical Systems.</a> Jom. , 2-8 (2018).</li><li>Heo, S. 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K., Keane, M., Zhang, H., Singh, P. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Effect+of+CO2+on+the+stability+of+strontium+doped+lanthanum+manganite+cathode.">Effect of CO2 on the stability of strontium doped lanthanum manganite cathode.</a> Journal of Power Sources. 268, 404-413 (2014).</li><li>Hu, B., Keane, M., Mahapatra, M. K., Singh, P. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Stability+of+strontium-doped+lanthanum+manganite+cathode+in+humidified+air.">Stability of strontium-doped lanthanum manganite cathode in humidified air.</a> Journal of Power Sources. 248, 196-204 (2014).</li><li>Li, C., Habler, G., Baldwin, L. 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The experimental results clearly demonstrate the effectiveness of chromium getters during long-term chromium transpiration tests and electrochemical tests. Presence of getters successfully mitigates the contamination of the electrode which otherwise would lead to rapid increase in polarization resistance and electrochemical performance degradation.
The formation of gas phase chromium species from chromia is favored and enhanced with an increase of water vapor concentration (humidity level)<sup...

Solid oxide fuel cell (SOFC) power system, a high temperature direct electrochemical energy conversion device, offers an environmentally friendly pathway to generate electricity from a wide variety of fossil and renewable fuels. SOFC technology finds its applications in centralized as well as distributed power generation areas1. This technology relies on electrochemical conversion of chemical energy stored in the fuels into electricity. Numerous advantages are offered by SOFCs in terms of high energy efficiency, high quality heat, ease of modularity, and no or negligible carbon footprints2. Several individual SOFC cells are connected in series or parallel fashion (namely SOFC stacks) to obtain desired output voltage. SOFC stacks consist of components such as dense electrolyte, porous electrodes, interconnection (IC) and seals3,4. Anode and cathode of adjacent cells are connected using IC, which not only serves as a separator to prevent any mixing of oxidant with fuel but also provides electrical connection between the adjacent anode and cathode5.
Improvements over decades of research and development in materials engineering have led to reduction in operating temperature for SOFCs, enabling replacements of ceramics materials with inexpensive stainless-steel alloys for the fabrication of electrochemically active cell and stack components and balance-of-plant (BOP) sub-systems. Commercially available ferritic and austenitic stainless steels are utilized for the fabrication of system components due to their low cost, matched coefficient of thermal expansion (CTE) and resistance to oxidation and corrosion at high operating temperatures6. Formation of Cr2O3 type passivating oxide scale on the alloy surface acts as a barrier layer against inward diffusion of oxygen from air or outward diffusion of cations from bulk alloy7.
In the presence of humidified air, Cr2O3 undergoes significant chemical transformation leading to hydrated chromium vapor species formation at SOFC operating temperatures. The gaseous chromium vapor is subsequently carried through the air stream into the cathode leading to surface and interface reactions with the cathode materials. Such cathode experiences both ohmic and non-ohmic increases in the polarization and electrical performance degradation. Details of the cathode degradation mechanisms have been illustrated elsewhere8,9,10.
The state-of-the-art methods to reduce or eliminate the above cathode degradation processes commonly consist of modifications of the alloy chemistry, application of surface coating and the use of chromium tolerant cathodes11,12. Although these techniques have demonstrated reduction of the cathode degradation due to Cr vapor interactions (namely Cr poisoning) for short-term, long-term efficacy for performance stability remains a concern, mainly due to cracking and spallation within the coating and interdiffusion of cations.
We have demonstrated a novel method to mitigate the problem of chromium poisoning by capturing the incoming chromium vapor before it reacts with the cathode materials13. The getters have been synthesized from low-cost alkaline earth and transition metal oxides using conventional ceramic processing techniques. The cost advantage of this approach is use of non-noble and non-strategic materials as well as conventional processing methods to fabricate getters for the mitigation of cathode degradation arising from airborne contaminants. The placement of the getter can be tailored to capture chromium vapor arising from BOP components or it can also be tailored to be placed within the electrochemically active stack components14,15. Here, we present methods to validate the chromium getters using transpiration and electrochemical tests. Experimental setup and characterization results will also be demonstrated to show the getter effectiveness and the mechanisms of Cr capture on the getter under typical SOFC operating conditions.

<table>
	<tbody>
		<tr>
			<td>Sr(NO3)2</td>
			<td>Sigma-Aldrich</td>
			<td>243426</td>
			<td>Getter precursor material</td>
		</tr>
		<tr>
			<td>Ni(NO3)2-6H2O</td>
			<td>Alfa Aesar</td>
			<td>A15540</td>
			<td>Getter precursor material</td>
		</tr>
		<tr>
			<td>NH4OH</td>
			<td>Alfa Aesar</td>
			<td>L13168</td>
			<td>Getter precursor material</td>
		</tr>
		<tr>
			<td>Pt ink</td>
			<td>ESL ElectroScience</td>
			<td>5051</td>
			<td>Current collector paste</td>
		</tr>
		<tr>
			<td>Pt wire</td>
			<td>Alfa Aesar</td>
			<td>10288</td>
			<td>Current collector wire</td>
		</tr>
		<tr>
			<td>Pt gause</td>
			<td>Alfa Aesar</td>
			<td>40935</td>
			<td>Current collector</td>
		</tr>
		<tr>
			<td>Cr2O3 powder</td>
			<td>Alfa Aesar</td>
			<td>12286</td>
			<td>Chromium source</td>
		</tr>
		<tr>
			<td>Nitric acid (HNO3)</td>
			<td>Sigma-Aldrich</td>
			<td>438073</td>
			<td>Chromium extraction</td>
		</tr>
		<tr>
			<td>Potassium permanganate (KMnO4)</td>
			<td>Alfa Aesar</td>
			<td>A12170</td>
			<td>Chromium extraction</td>
		</tr>
		<tr>
			<td>LSM paste</td>
			<td>Fuelcellmaterials</td>
			<td>18007</td>
			<td>Cathode</td>
		</tr>
		<tr>
			<td>YSZ electrolyte</td>
			<td>Fuelcellmaterials</td>
			<td>211102</td>
			<td>Electrolyte</td>
		</tr>
		<tr>
			<td>Alumina fiber board</td>
			<td>Zircar</td>
			<td>GJ0014</td>
			<td>Getter substrate</td>
		</tr>
		<tr>
			<td>Ceramabond paste</td>
			<td>AREMCO</td>
			<td>552-VFG</td>
			<td>For cell sealing</td>
		</tr>
		<tr>
			<td>ICP-MS (7700s)</td>
			<td>Agilent</td>
			<td>NA</td>
			<td>For Cr analysis</td>
		</tr>
		<tr>
			<td>Potentiostat (VMP3)</td>
			<td>Biologic</td>
			<td>NA</td>
			<td>For EIS/I-t measurement</td>
		</tr>
		<tr>
			<td>FIB (Helios Nanolab 460F1)</td>
			<td>FEI</td>
			<td>NA</td>
			<td>For Nano-sample preparation</td>
		</tr>
		<tr>
			<td>TEM (Talos F200X S/TEM)</td>
			<td>FEI</td>
			<td>NA</td>
			<td>For composition analysis</td>
		</tr>
	</tbody>
</table>

development and validation of chromium getters for solid oxide fuel cell power systems

Degradation of cathode in solid oxide fuel cells (SOFC) remains a major concern for the long-term performance stability and operational reliability. The presence of gas phase chromium species in air has demonstrated significant cathode performance degradation during long-term exposure due to unwanted compound formation at the cathode and electrolyte interface which retards the oxygen reduction reaction (ORR). We have demonstrated a novel method to mitigate the cathode degradation using chromium getters which capture the gas phase chromium species before it is ingested in the cathode chamber. Low-cost getter materials, synthesized from alkaline earth and transition metal oxides, are coated on the cordierite honeycomb substrate for application in the SOFC power systems. As-fabricated getters have been screened by chromium transpiration tests for 500 h in humidified air atmosphere in presence of chromium vapor. Selected getters have been further validated utilizing electrochemical tests. Typically, electrochemical performance of SOFCs (lanthanum strontium manganite (LSM) &#449; yttria stabilized zirconia (YSZ) &#449; Pt) was measured at 850 &#176;C in the presence and absence of Cr getter. For the 100 h cell tests containing getters, stable electrochemical performance was maintained, whereas the cell performance in the absence of Cr getters rapidly decreased in 10 h. Analyses of Nyquist plots indicated significant increase in the polarization resistance within the first 10 h of the cell operation. Characterization results from posttest SOFCs and getters have demonstrated the high efficiency of chromium capture for the mitigation of cell degradation.

A Cr transpiration experiment is a screening test for the selection of Cr getters. Cr transpiration setup was utilized to validate the performance of chromium getter under the SOFC operating conditions. Experiments were conducted in the presence of a chromium getter operated at 850 &#176;C in humidified (3% H2O) air for 500 h. Visual observations during Cr transpiration tests indicated significant discoloration of the outlet elbow during 500 h in the absence of getter. However,...

Watch this Scientific Journal Video about Development and Validation of Chromium Getters for Solid Oxide Fuel Cell Power Systems at JoVE.com

Development and Validation of Chromium Getters for Solid Oxide Fuel Cell Power Systems

Cathode poisoning from airborne contaminants in trace levels remains a major concern for long-term stability of high-temperature electrochemical systems. We provide a novel method to mitigate the cathode degradations using getters, which capture airborne contaminants at high temperature before entering electrochemically active stack area.

Degradation of cathode in solid oxide fuel cells (SOFC) remains a major concern for the long-term performance stability and operational reliability. The ...

Chromium containing alloys are used in SOFC's as metallic interconnects to form chromia scale for corrosion protection. However, chromium vaporization at high temperatures produces gaseous chromium species resulting in SOFC degradation. This method provides a solution for chromium poisoning in solid oxide fuel cell power systems.The main advantages are the use of low cost materials and effective capture of contaminants at both low and high temperatures. Other high temperature industrial systems using chromium containing alloys, such as steam electrolysis systems, oxygen transport membrane systems and petrochemical systems could use this method for quality and emission control. This video demonstration can have interested researchers quickly learn these technicals, some steps are very simple for beginners.These technicals can have researchers develop the skills for an advance to electrochemical technology research. To begin, combine nine milliliters of 2.4 molar aqueous strontium nitrate, with seven milliliters of 2.4 molar aqueous nickel nitrate. Stir the mixture for 30 minutes at 300 RPM while heating it to 80 degrees celsius to dissolve the solids.Then, add 30 milliliters of 5 molar aqueous ammonia to increase the solution pH to 8.5. Continue stirring the mixture at 80 degree celsius for 24 hours, to precipitate the precursor powder. Dry the solution in a dry oven at 120 degrees Celsius, until the water evaporates completely, which usually takes about 24 hours, to leave a blue waxy compound.We suspend the compound in 50 milliliters of deionized water using both manual and magnetic stirring. Centrifuge the suspension at 5000 RPM for 5 minutes. And remove the liquid which contains residual ammonium nitrate.At 200 to 380 degrees Celsius, ammonium nitrate will decompose and produce ammonia nitrate acid, nitrogen oxide gases. Proper washing with distilled water will reduce or eliminate the emission of these gases. Dry the rinsed precursor powder at 120 degrees Celsius for two hours.Next, add the ionized water to the powder and mix it for at least five minutes to make a thick slurry. De-gas the slurry in a vacuum chamber to remove air bubbles. Then, place a cordierite honeycomb substrate in the slurry and perform vacuum infiltration for five minutes to fill the pores with slurry.Afterwards, flow air through the dip coated substrate to remove excess slurry from the channels. Place the sample in an air filled furnace and heat it to about 120 degrees Celsius at five degrees per minute. Dry the sample in air for at least two hours.Then, ramp the furnace to 650 degrees Celsius at five degrees per minute and calsign the sample in air for 12 hours to finish producing the chromium getter. To begin the validation test, place two grams of centered chromia pellets in a quartz tube furnace equipped with a diffuser. Place a chromium getter on the other side of the diffuser.Connect the chromium side of the furnace to a compressed air source via a room temperature water bubbler. Connect the getter side to a vent via a glass elbow and a chromium vapor trapping assembly. Purge the system with humidified air at 300 SCCM for 15 minutes to an hour.Then ramp the furnace to 850 degrees Celsius at three degrees per minute and maintain that temperature for 500 hours. Check the outlet elbow for discoloration indicating the deposition of chromium compounds every 100 hours. Once the test is finished, cool the furnace to room temperature before turning off the air flow and retrieving the getter sample.Collect the water from the chromium trapping assembly then, soak the quartz tube, glass elbow, condenser and wash bottles with 20%by weight nitric acid to extract deposited chromium and collect the rinses. Soak the glassware in 20%nitric acid for 12 hours to extract additional deposited chromium and collect the rinse. If any glassware is still discolored, soak it in alkaline potassium permanganate for 12 hours at 80 degrees Celsius.Then collect and mix chromium extract from all the components to analyze the chromium content with ICPMS. Then, slice the getter sample in half with a knife and coat the exposed surfaces with gold. Coat the chromium getter sample with gold and assess the elemental distribution with energy dispersive x-ray spectroscopy.Perform another EDS analysis and plot the quantity of chromium with respect to the distance from the chromium source. To begin SOFC fabrication, screen print lanthanum strontium manganate paste on the surface of three yttria-stabilized zirconia electrodes and center the assemblies. Then, attach a platinum electrode to each YSZ disk as the anode using platinum ink.Attach platinum gauze to both the anode and cathode and attach short platinum wires to the cathode, anode and YSZ disk. Place the SOFC's in a furnace, ramp them to 850 degrees Celsius at three degrees per minute and cure them in air for two hours. Then, connect silver conductive wires to a cured SOFC and mount it in the constant heating zone of a cylinder tube furnace.Seal the SOFC in the furnace with ceramic paste and connect the electrodes to a potentiostat. Follow standard procedures to set up the experiment. Make sure that these are good cylinder cell and that all three electrodes are properly connected to the potentiostat.Then, ramp the furnace to 850 degrees Celsius at five degrees per minute. While the furnace heats, configure the potentiostats to record the cell current every minute with a 0.5 volt bias between the cathode and the reference electrode. Set the potentiostats to perform electrochemical impedance spectroscopy between the cathode and the reference electrode every hour.When the furnace reaches the test temperature, flow humidified air towards the cathode at 300 SCCM and dry air towards the anode at 150 SCCM. Start the measurements and let the test run for 100 hours. After the test, cool the furnace to room temperature and retrieve the cell for characterization.For the next test, place two grams of chromia pellets in a perforated alumina tube in the constant heating zone. Fix a new SOFC above the chromium source and repeat the test end measurements in the exact same way. For the third test, load two grams of chromia pellets into the tube and mount a chromium getter above the chromium source.Fix a new SOFC over the getter and perform the test end measurements under the same conditions. In the transpiration test, the chromium profile indicated that most of the chromium was trapped within the first four millimeters of the getter. Analysis of the chromium getter material deposited on an alumina fiber substrate showed large chromium and strontium rich particles near the vapor inlet.Elemental maps of fiber cross-sections confirmed that chromium and strontium occurred on the surface of the fiber. Electrochemical tests of LSM-YSZ SOFC's in the presence and absence of chromium showed that chromium vapor rapidly poisoned the cell. This was attributed to chromium oxide deposits on the LSM-YSZ interface, hindering the oxygen reduction reaction at that interface.Placing an SNO chromium getter between the chromium source and the SOFC resulted in SOFC performance comparable to the performance in the absence of chromium. This performance was maintained over a wide range of chromium vapor flow rates. The fabrication protocol produces a stable efficient getter for airborne chromium impurities.Using different chemicals we can develop getters to capture other gaseous contaminants such as boron and silicon vapors. The transmission protocol measures the evaporation of chromium containing alloy materials and validates the performance of getters capturing hexaamminechromium vapor in air under typical SOFC operating conditions. The electrochemical validation protocol demonstrates getter efficience at a nominal SOFC operating conditions.Since the information is essential for scaling up getter and SOFC technologies for industry and their commercial uses. This method uses small amounts of chemicals and reasons that can be managed and handled according to existing laboratory health and safety policies.

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Preparation of Hydrophobic Metal-Organic Frameworks via Plasma Enhanced Chemical Vapor Deposition of Perfluoroalkanes for the Removal of Ammonia

Plasma enhanced chemical vapor deposition (PECVD) of perfluoroalkanes has long been studied for tuning the wetting properties of surfaces. For high surface area microporous materials, such as metal-organic frameworks (MOFs), unique challenges present themselves for PECVD treatments. Herein the protocol for development of a MOF that was previously unstable to humid conditions is presented. The protocol describes the synthesis of Cu-BTC (also known as HKUST-1), the treatment of Cu-BTC with PECVD of perfluoroalkanes, the aging of materials under humid conditions, and the subsequent ammonia microbreakthrough experiments on milligram quantities of microporous materials. Cu-BTC has an extremely high surface area (~1,800 m2/g) when compared to most materials or surfaces that have been previously treated by PECVD methods. Parameters such as chamber pressure and treatment time are extremely important to ensure the perfluoroalkane plasma penetrates to and reacts with the inner MOF surfaces. Furthermore, the protocol for ammonia microbreakthrough experiments set forth here can be utilized for a variety of test gases and microporous materials.

Herein the procedures for plasma enhanced chemical vapor deposition of perfluoroalkanes on microporous materials such as metal-organic frameworks to enhance their stability and hydrophobicity are described. Furthermore, breakthrough testing of milligram quantities of samples is described in detail.

Plasma enhanced chemical vapor deposition (PECVD) of perfluoroalkanes has long been studied for tuning the wetting properties of surfaces. For high ...

Activating Molecules, Ions, and Solid Particles with Acoustic Cavitation

The chemical and physical effects of ultrasound arise not from a direct interaction of molecules with sound waves, but rather from the acoustic cavitation: the nucleation, growth, and implosive collapse of microbubbles in liquids submitted to power ultrasound. The violent implosion of bubbles leads to the formation of chemically reactive species and to the emission of light, named sonoluminescence. In this manuscript, we describe the techniques allowing study of extreme intrabubble conditions and chemical reactivity of acoustic cavitation in solutions. The analysis of sonoluminescence spectra of water sparged with noble gases provides evidence for nonequilibrium plasma formation. The photons and the "hot" particles generated by cavitation bubbles enable to excite the non-volatile species in solutions increasing their chemical reactivity. For example the mechanism of ultrabright sonoluminescence of uranyl ions in acidic solutions varies with uranium concentration: sonophotoluminescence dominates in diluted solutions, and collisional excitation contributes at higher uranium concentration. Secondary sonochemical products may arise from chemically active species that are formed inside the bubble, but then diffuse into the liquid phase and react with solution precursors to form a variety of products. For instance, the sonochemical reduction of Pt(IV) in pure water provides an innovative synthetic route for monodispersed nanoparticles of metallic platinum without any templates or capping agents. Many studies reveal the advantages of ultrasound to activate the divided solids. In general, the mechanical effects of ultrasound strongly contribute in heterogeneous systems in addition to chemical effects. In particular, the sonolysis of PuO2 powder in pure water yields stable colloids of plutonium due to both effects.

Acoustic cavitation in liquids submitted to power ultrasound creates transient extreme conditions inside the collapsing bubbles, which are the origin of unusual chemical reactivity and light emission, known as sonoluminescence. In the presence of noble gases, nonequilibrium plasma is formed. The "hot" particles and the photons generated by collapsing bubbles are able to excite species in solution.

The chemical and physical effects of ultrasound arise not from a direct interaction of molecules with sound waves, but rather from the acoustic ...

High-pressure Sapphire Cell for Phase Equilibria Measurements of CO2/Organic/Water Systems

The high pressure sapphire cell apparatus was constructed to visually determine the composition of multiphase systems without physical sampling. Specifically, the sapphire cell enables visual data collection from multiple loadings to solve a set of material balances to precisely determine phase composition. Ternary phase diagrams can then be established to determine the proportion of each component in each phase at a given condition. In principle, any ternary system can be studied although ternary systems (gas-liquid-liquid) are the specific examples discussed herein. For instance, the ternary THF-Water-CO2 system was studied at 25 and 40&#160;&#176;C and is described herein. Of key importance, this technique does not require sampling. Circumventing the possible disturbance of the system equilibrium upon sampling, inherent measurement errors, and technical difficulties of physically sampling under pressure is a significant benefit of this technique. Perhaps as important, the sapphire cell also enables the direct visual observation of the phase behavior. In fact, as the CO2 pressure is increased, the homogeneous THF-Water solution phase splits at about 2 MPa. With this technique, it was possible to easily and clearly observe the cloud point and determine the composition of the newly formed phases as a function of pressure.
The data acquired with the sapphire cell technique can be used for many applications. In our case, we measured swelling and composition for tunable solvents, like gas-expanded liquids, gas-expanded ionic liquids and Organic Aqueous Tunable Systems (OATS)1-4. For the latest system, OATS, the high-pressure sapphire cell enabled the study of (1) phase behavior as a function of pressure and temperature, (2) composition of each phase (gas-liquid-liquid) as a function of pressure and temperature and (3) catalyst partitioning in the two liquid phases as a function of pressure and composition. Finally, the sapphire cell is an especially effective tool to gather accurate and reproducible measurements in a timely fashion.

High-pressure Sapphire Cell for Phase Equilibria Measurements of CO2/Organic/Water Systems

The high pressure sapphire cell apparatus is a unique tool to study, without sampling, phase behavior under a wide range of pressures. Using a cathetometer, very precise volume measurements can be recorded to measure liquid expansion and phase composition. Thus, this synthetic method enables the study of (1) phase equilibria of multi-component mixtures and (2) the partition behavior of catalyst or model compounds as a function of pressure.

The high pressure sapphire cell apparatus was constructed to visually determine the composition of multiphase systems without physical sampling. ...

Quantitative Detection of Trace Explosive Vapors by Programmed Temperature Desorption Gas Chromatography-Electron Capture Detector

The direct liquid deposition of solution standards onto sorbent-filled thermal desorption tubes is used for the quantitative analysis of trace explosive vapor samples. The direct liquid deposition method yields a higher fidelity between the analysis of vapor samples and the analysis of solution standards than using separate injection methods for vapors and solutions, i.e., samples collected on vapor collection tubes and standards prepared in solution vials. Additionally, the method can account for instrumentation losses, which makes it ideal for minimizing variability and quantitative trace chemical detection. Gas chromatography with an electron capture detector is an instrumentation configuration sensitive to nitro-energetics, such as TNT and RDX, due to their relatively high electron affinity. However, vapor quantitation of these compounds is difficult without viable vapor standards. Thus, we eliminate the requirement for vapor standards by combining the sensitivity of the instrumentation with a direct liquid deposition protocol to analyze trace explosive vapor samples.

Trace explosive vapors of TNT and RDX collected on sorbent-filled thermal desorption tubes were analyzed using a programmed temperature desorption system coupled to GC with an electron capture detector. The instrumental analysis is combined with direct liquid deposition method to reduce sample variability and account for instrumentation drift and losses.

The direct liquid deposition of solution standards onto sorbent-filled thermal desorption tubes is used for the quantitative analysis of trace explosive ...

Synthetic Methodology for Asymmetric Ferrocene Derived Bio-conjugate Systems via Solid Phase Resin-based Methodology

Early detection is a key to successful treatment of most diseases, and is particularly imperative for the diagnosis and treatment of many types of cancer. The most common techniques utilized are imaging modalities such as Magnetic Resonance Imaging (MRI), Positron Emission Topography (PET), and Computed Topography (CT) and are optimal for understanding the physical structure of the disease but can only be performed once every four to six weeks due to the use of imaging agents and overall cost. With this in mind, the development of &#8220;point of care&#8221; techniques, such as biosensors, which evaluate the stage of disease and/or efficacy of treatment in the clinician&#8217;s office and do so in a timely manner, would revolutionize treatment protocols.1 As a means to exploring ferrocene based biosensors for the detection of biologically relevant molecules2, methods were developed to produce ferrocene-biotin bio-conjugates described herein. This report will focus on a biotin-ferrocene-cysteine system that can be immobilized on a gold surface.

The synthesis of asymmetric species of ferrocene is challenging using solution techniques. This report focuses on the methods carried out to produce a ferrocene-biotin bioconjugate using facile and clean reactions accomplished via solid-phase synthesis. Incorporation of a thiolate moiety is shown to impart the ability for immobilization on gold surfaces.

Early detection is a key to successful treatment of most diseases, and is particularly imperative for the diagnosis and treatment of many types of cancer. ...

Development of a Backbone Cyclic Peptide Library as Potential Antiparasitic Therapeutics Using Microwave Irradiation

Protein-protein interactions (PPIs) are intimately involved in almost all biological processes and are linked to many human diseases. Therefore, there is a major effort to target PPIs in basic research and in the pharmaceutical industry. Protein-protein interfaces are usually large, flat, and often lack pockets, complicating the discovery of small molecules that target such sites. Alternative targeting approaches using antibodies have limitations due to poor oral bioavailability, low cell-permeability, and production inefficiency.
Using peptides to target PPI interfaces has several advantages. Peptides have higher conformational flexibility, increased selectivity, and are generally inexpensive. However, peptides have their own limitations including poor stability and inefficiency crossing cell membranes. To overcome such limitations, peptide cyclization can be performed. Cyclization has been demonstrated to improve peptide selectivity, metabolic stability, and bioavailability. However, predicting the bioactive conformation of a cyclic peptide is not trivial. To overcome this challenge, one attractive approach it to screen a focused library to screen in which all backbone cyclic peptides have the same primary sequence, but differ in parameters that influence their conformation, such as ring size and position.
We describe a detailed protocol for synthesizing a library of backbone cyclic peptides targeting specific parasite PPIs. Using a rational design approach, we developed peptides derived from the scaffold protein Leishmania receptor for activated C-kinase (LACK). We hypothesized that sequences in LACK that are conserved in parasites, but not in the mammalian host homolog, may represent interaction sites for proteins that are critical for the parasites&#39; viability. The cyclic peptides were synthesized using microwave irradiation to reduce reaction times and increase efficiency. Developing a library of backbone cyclic peptides with different ring sizes facilitates a systematic screen for the most biological active conformation. This method provides a general, fast, and facile way to synthesize cyclic peptides.

A simple and general method for the synthesis of cyclic peptides using microwave irradiation is outlined. This procedure enables the synthesis of backbone cyclic peptides with a collection of different conformations while retaining the side chains and the pharmacophoric moieties., and therefore, allows to screen for the bioactive conformation.

Protein-protein interactions (PPIs) are intimately involved in almost all biological processes and are linked to many human diseases. Therefore, there is ...

X-ray Powder Diffraction in Conservation Science: Towards Routine Crystal Structure Determination of Corrosion Products on Heritage Art Objects

The crystal structure determination and refinement process of corrosion products on historic art objects using laboratory high-resolution X-ray powder diffraction (XRPD) is presented in detail via two case studies.
The first material under investigation was sodium copper formate hydroxide oxide hydrate, Cu4Na4O(HCOO)8(OH)2&#8729;4H2O (sample 1) which forms on soda glass/copper alloy composite historic objects (e.g., enamels) in museum collections, exposed to formaldehyde and formic acid emitted from wooden storage cabinets, adhesives, etc. This degradation phenomenon has recently been characterized as &#34;glass induced metal corrosion&#34;.
For the second case study, thecotrichite, Ca3(CH3COO)3Cl(NO3)2&#8729;6H2O (sample 2), was chosen, which is an efflorescent salt forming needlelike crystallites on tiles and limestone objects which are stored in wooden cabinets and display cases. In this case, the wood acts as source for acetic acid which reacts with soluble chloride and nitrate salts from the artifact or its environment.
The knowledge of the geometrical structure helps conservation science to better understand production and decay reactions and to allow for full quantitative analysis in the frequent case of mixtures.

Modern high resolution X-ray powder diffraction (XRPD) in the laboratory is used as an efficient tool to determine crystal structures of long-known corrosion products on historic objects.

The crystal structure determination and refinement process of corrosion products on historic art objects using laboratory high-resolution X-ray powder ...

Original Experimental Approach for Assessing Transport Fuel Stability

The study of fuel oxidation stability is an important issue for the development of future fuels. Diesel and kerosene fuel systems have undergone several technological changes to fulfill environmental and economic requirements. These developments have resulted in increasingly severe operating conditions whose suitability for conventional and alternative fuels needs to be addressed. For example, fatty acid methyl esters (FAMEs) introduced as biodiesel are more prone to oxidation and may lead to deposit formation. Although several methods exist to evaluate fuel stability (induction period, peroxides, acids, and insolubles), no technique allows one to monitor the real-time oxidation mechanism and to measure the formation of oxidation intermediates that may lead to deposit formation. In this article, we developed an advanced oxidation procedure (AOP) based on two existing reactors. This procedure allows the simulation of different oxidation conditions and the monitoring of the oxidation progress by the means of macroscopic parameters, such as total acid number (TAN) and advanced analytical methods like gas chromatography coupled to mass spectrometry (GC-MS) and Fourier Transform Infrared - Attenuated Total Reflection (FTIR-ATR). We successfully applied AOP to gain an in-depth understanding of the oxidation kinetics of a model molecule (methyl oleate) and commercial diesel and biodiesel fuels. These developments represent a key strategy for fuel quality monitoring during logistics and on-board utilization.

Oxidation stability of transport fuels has become a concern for future fuel development. This work presents an original methodology developed by IFP Energies Nouvelles for assessing fuel stability using two different reactors. This methodology was successfully applied to gain an in-depth understanding of the oxidation kinetics and pathways of model molecules and commercial fuels.

The study of fuel oxidation stability is an important issue for the development of future fuels. Diesel and kerosene fuel systems have undergone several ...

Measurement of Particle Size Distribution in Turbid Solutions by Dynamic Light Scattering Microscopy

A protocol for measuring polydispersity of concentrated polymer solutions using dynamic light scattering is described. Dynamic light scattering is a technique used to measure the size distribution of polymer solutions or colloidal particles. Although this technique is widely used for the assessment of polymer solutions, it is difficult to measure the particle size in concentrated solutions due to the multiple scattering effect or strong light absorption. Therefore, the concentrated solutions should be diluted before measurement. Implementation of the confocal optical component in a dynamic light scattering microscope1 helps to overcome this barrier. Using such a microscopic system, both transparent and turbid systems can be analyzed under the same experimental setup without a dilution. As a representative example, a size distribution measurement of a temperature-responsive polymer solution was performed. The sizes of the polymer chains in an aqueous solution were several tens of nanometers at a temperature below the lower critical solution temperature (LCST). In contrast, the sizes increased to more than 1.0 &#181;m when above the LCST. This result is consistent with the observation that the solution turned turbid above the LCST.

A protocol for the direct measurement of particle size distribution in concentrated solutions using dynamic light scattering microscopy is presented.

A protocol for measuring polydispersity of concentrated polymer solutions using dynamic light scattering is described. Dynamic light scattering is a ...

In Situ Detection and Single Cell Quantification of Metal Oxide Nanoparticles Using Nuclear Microprobe Analysis

Micro-analytical techniques based on chemical element imaging enable the localization and quantification of chemical composition at the cellular level. They offer new possibilities for the characterization of living systems and are particularly appropriate for detecting, localizing and quantifying the presence of metal oxide nanoparticles both in biological specimens and the environment. Indeed, these techniques all meet relevant requirements in terms of (i) sensitivity (from 1 up to 10 &#181;g.g-1 of dry mass), (ii) micrometer range spatial resolution, and (iii) multi-element detection. Given these characteristics, microbeam chemical element imaging can powerfully complement routine imaging techniques such as optical and fluorescence microscopy. This protocol describes how to perform a nuclear microprobe analysis on cultured cells (U2OS) exposed to titanium dioxide nanoparticles. Cells must grow on and be exposed directly in a specially designed sample holder used on the optical microscope and in the nuclear microprobe analysis stages. Plunge-freeze cryogenic fixation of the samples preserves both the cellular organization and the chemical element distribution. Simultaneous nuclear microprobe analysis (scanning transmission ion microscopy, Rutherford backscattering spectrometry and particle induced X-ray emission) performed on the sample provides information about the cellular density, the local distribution of the chemical elements, as well as the cellular content of nanoparticles. There is a growing need for such analytical tools within biology, especially in the emerging context of Nanotoxicology and Nanomedicine for which our comprehension of the interactions between nanoparticles and biological samples must be deepened. In particular, as nuclear microprobe analysis does not require nanoparticles to be labelled, nanoparticle abundances are quantifiable down to the individual cell level in a cell population, independently of their surface state.

In Situ Detection and Single Cell Quantification of Metal Oxide Nanoparticles Using Nuclear Microprobe Analysis

We describe a procedure for the detection of chemical elements present in situ in human cells as well as their in vitro quantification. The method is well-suited to any cell type and is particularly useful for quantitative chemical analyses in single cells following in vitro metal oxide nanoparticles exposure.

Micro-analytical techniques based on chemical element imaging enable the localization and quantification of chemical composition at the cellular level. ...