This work was supported by NSF Grant No. DMR-1207243, the NSF MRSEC program (DMR-0820414), DOE Grant No. DE-FG02-03ER46054, and the OSU-Institute for Materials Research. The authors acknowledge the NanoSystems Laboratory at Ohio State University, and technical assistance from C. Y. Kao and C.Y. Chen.

1. Synthesis and Preparation of Precursors
<ol>
	<li>Preparation of [Et4N][V(CO)6]23
	<ol>
		<li>In a nitrogen glovebox, cut 1.88 g of sodium metal into ~40 pieces and mix with 14.84 g of anthracene in 320 ml of anhydrous tetrahydrofuran (THF) in a 1 L three-neck round bottom flask. 
		CAUTION: Both sodium metal and tetrahydrofuran are highly flammable.</li>
		<li>Stir the solution for 4.5 hr at RT under a nitrogen atmosphere until a deep blue solution of NaC14H10 is formed.</li>
		<li>Cool the solution to 0 &#176;C.</li>
		<li>In a nitrogen glovebox, prepare a pink-red solution of VCL3(THF)3 by adding 400 ml of anhydrous THF into 7.48 g of VCl3(THF)3 in a 500 ml round bottom flask and stir at RT for 1 hr.</li>
		<li>Remove the pink-red solution VCl3(THF)3 from the glovebox and cool to 0 &#176;C for 20 min. Transfer to the previous solution of NaC14H10 via cannula under nitrogen atmosphere. A homogeneous deep purple solution is formed immediately after the addition is completed.</li>
		<li>Remove from the nitrogen and stir for 15 hr. Slowly warm to RT by placing flask in ice bucket allowing the ice to melt O/N.</li>
		<li>Cool the solution again to 0 &#176;C and fill the reaction flask with carbon monoxide. The solution will change from deep purple to yellow-brown in a matter of minutes. 
		CAUTION: Carbon monoxide is highly toxic. This step should not be performed alone and a carbon monoxide alarm should be installed in the lab.</li>
		<li>Stir the solution under a carbon monoxide atmosphere at 0 &#176;C for 15 hr and then slowly warm to RT.</li>
		<li>Remove all but 200 ml of THF under vacuum. Add 500 ml of O2 free water while stirring the solution. V(CO)6 is easily oxidized and the presence of O2 will result in a low yield.</li>
		<li>Filter the resulting yellow slurry into a solution composed of 20.8 g of tetraethylammonium bromide (Et4NBr) in 200 ml of H2O.</li>
		<li>Wash the filter cake with O2 free water until it is colorless.</li>
		<li>Filter the resulting slurry of [Et4N][V(CO)6] by vacuum filtration and dry under vacuum.</li>
		<li>Store [Et4N][V(CO)6] in a glovebox freezer for future use.</li>
	</ol>
	</li>
	<li>Preparation of V(CO)623
	<ol>
		<li>Grease the connection points for a vacuum adaptor with stopcock, glass two-way connecting tube, and cold-finger. Place a cold finger in the center neck and a vacuum adaptor with stopcock in the third opening.</li>
		<li>In an argon glovebox, mix 100 mg of [Et4N][V(CO)6] with 1 g of phosphoric acid in a round bottom flask containing a magnetic stirring bar.</li>
		<li>Connect the round bottom flask to a three-neck round bottom flask via glass two-way connecting tube in the argon glovebox.</li>
		<li>Remove the sealed flask system from the glovebox and set up in chemical hood.</li>
		<li>Add methanol to the cold finger and stir with a spatula-while adding liquid nitrogen until methanol is frozen. Pump down the system by opening the stopcock to a vacuum line until the pressure reaches 5 x 10-2 Torr.</li>
		<li>Submerge the round bottom flask in an oil bath set to 45 &#176;C and turn on the magnetic stirring. Once the reaction starts, the phosphoric acid will melt and a black-blue powder condenses on the cold finger.</li>
		<li>Open the vacuum line when a black powder condenses on the round bottom flask instead of the cold finger because the pressure is too high. Pump the system back to 5 x 10-2 Torr before closing again.</li>
		<li>Rotate the reaction flask as necessary to mix all of the reactants.</li>
		<li>Allow the reaction to continue until the remaining residue in round bottom flask is white-grey and no longer bubbling.</li>
		<li>Pour copper pellets into a cold safe container and cool with liquid nitrogen.</li>
		<li>Remove the methanol from the cold finger with a micropipette. Pour chilled copper pellets into the cold finger to keep it cold during transfer to glovebox.</li>
		<li>Wipe oil and condensed water off the flask system before transferring into an argon glovebox.</li>
		<li>Inside the glovebox, remove the cold finger from the flask system and use a spatula to scrape the black V(CO)6 powder onto a piece of weighing paper.</li>
		<li>Store V(CO)6 in a bottle under an argon atmosphere and keep below RT.</li>
	</ol>
	</li>
	<li>Purification of TCNE by sublimation
	<ol>
		<li>Purchase commercially available tetracyanoethylene (TCNE) and store in a chemical refrigerator.</li>
		<li>Mix ~5 g of TCNE with ~0.5 g of activated carbon and grind with a mortar and pestle.</li>
		<li>Place TCNE/carbon mixture into a glass boat or wrap in delicate task wipes and put in the bottom of a flask with a vacuum line.</li>
		<li>Place a cold finger into the top of the flask and seal the two parts together with a clamp.</li>
		<li>Add methanol to the cold finger and stir with a spatula-while adding liquid nitrogen until methanol is frozen. Place the bottom of the flask containing the TCNE in an oil bath heated to 70 &#176;C.</li>
		<li>Open the vacuum line to reach a pressure of 10-4 Torr and then close the vacuum line.</li>
		<li>Occasionally open the vacuum line to maintain the pressure. TCNE condenses on the cold finger as sublimation begins. Once no more TCNE accumulates on the cold finger the sublimation is finished.</li>
		<li>Remove the methanol from the cold finger with a micropipette.</li>
		<li>Wipe oil and condensed water off the flask system before transferring into an argon glovebox.</li>
		<li>Inside the glovebox, remove the cold finger from the flask system and use a spatula to scrape the TCNE powder onto a piece of weighing paper.</li>
		<li>Store purified TCNE in a refrigerator below RT under inert atmosphere.</li>
	</ol>
	</li>
</ol>
2. Set up Deposition System inside an Argon Glovebox
<ol>
	<li>Assemble the reactor inside an argon glovebox as shown in Figure 1A.
	<ol>
		<li>Set up a connection to a vacuum pump.</li>
		<li>Set up the gas flow connections by connecting a 3-way stopcock between a flow meter and two lines connected to micrometer valves.</li>
		<li>Slide the glass heater coil around the reactor (part A, Figure 1B).</li>
		<li>Wrap a glass slide with polytetrafluoroethylene (PTFE) thread seal tape.</li>
		<li>Push the glass slide approximately 10 cm from the right side of the reactor, part A.</li>
		<li>Place an O-ring on Part B and slide into the right side of the reactor. Join the two pieces together with a clamp.</li>
		<li>Attach a vacuum line to the bottom connection on part A and attach the gauge to the top connection.</li>
		<li>Place a boat filled with purified TCNE into part C near end so that the TCNE will sit in the hottest part of the reactor.</li>
		<li>Grease the connection of part C and slide it into the left side of the reactor.</li>
		<li>Grease both sides of the T-boat filled with V(CO)6 and slide into the right end of part B.</li>
		<li>Connect each micrometer valve. One should be connected to the right side of the T-boat and the other to the left side of part C and clamp both in place.</li>
		<li>Run a test deposition to determine where the reaction zone is located.</li>
	</ol>
	</li>
	<li>Deposit V[TCNE]x~2 onto substrates
	<ol>
		<li>Set the temperature of the reaction heating coil so that the reaction zone is set to a value near 46 &#176;C when measured on the bottom of the reactor and the area of the TCNE boat is near 75 &#176;C. Set the temperature of a silicone oil bath to 10 &#176;C. Allow the temperatures to stabilize for at least 30 min.</li>
		<li>Slide the glass heater coil around the reactor (part A, Figure 1A).</li>
		<li>Wrap a glass slide with polytetrafluoroethylene (PTFE) thread seal tape. Arrange samples on top of covered slide within a two-inch space.</li>
		<li>Push the glass slide into the reactor so the samples are located in the reaction zone. Alternately samples can be placed directly on the bottom of the reactor, although the reaction zone may be shifted without a glass slide.</li>
		<li>Place an O-ring on Part B and slide into the right side of the reactor. Join the two pieces together with a clamp.</li>
		<li>Attach a vacuum line to the bottom connection on part A and attach the gauge to the top connection.</li>
		<li>Put 50 mg of TCNE into the TCNE boat and 5 mg of V(CO)6 into the T-boat (these quantities are appropriate for an 75-90 min deposition).</li>
		<li>Slide the TCNE boat into part C near the end so that the TCNE will sit in the hottest part of the reactor which should be about 75 &#176;C.</li>
		<li>Grease the connection of part C and slide it into the left side of the reactor.</li>
		<li>Grease both sides of the T-boat and slide into the right end of part B.</li>
		<li>Slide the flow line onto the right side of the T-boat and left sides of part C and clamp in place. The assembled set-up should resemble Figure 1A.</li>
		<li>Raise the oil bath to cover the entire bottom of the T-boat.</li>
		<li>Open the vacuum line to reach a pressure of 30-35 mmHg.</li>
		<li>Set the flow rate to 56 sccm for the V(CO)6 and to 84 sccm for the TCNE. The reaction should begin immediately with a greenish material condensing on the wall of reaction zone.</li>
		<li>Allow reaction to proceed for the desired length of time. The thickness of the thin film is based on reaction time and location inside the reactor, as shown in Figure 2.</li>
		<li>To stop the reaction, close vacuum line and turn off the heater and oil bath.</li>
	</ol>
	</li>
</ol>
3. Clean up
<ol>
	<li>Take apart the system in any order.</li>
	<li>Soak all the glassware except the heater coil in a base bath solution for at least 1-2 hr.</li>
	<li>Rinse glassware with water and dry in an oven.</li>
</ol>
<img alt="Figure 1" src="/files/ftp_upload/52891/52891fig1.jpg" /> 
Figure 1. (A) Fully assembled custom chemical vapor deposition (CVD) system. (B) Expanded view of the components for the CVD system. <a href="https://www.jove.com/files/ftp_upload/52891/52891fig1large.jpg" target="_blank">Please click here to view a larger version of this figure.</a>
<img alt="Figure 2" src="/files/ftp_upload/52891/52891fig2.jpg" /> 
Figure 2. (A) A top view of the substrates in the reactor showing their location. (B) Approximate film thickness as function of position inside the reactor tube, Part A from Figure 1B for a deposition of 75 min. <a href="https://www.jove.com/files/ftp_upload/52891/52891fig2large.jpg" target="_blank">Please click here to view a larger version of this figure.</a>

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The authors have nothing to disclose.

The key parameters for V[TCNE]x~2 deposition include temperature, carrier gas flow, pressure, and ratio of precursors. Because the chemical vapor deposition set-up is not commercially available these parameters will need to be optimized for each system. A previous study by Shima et al. revealed that the temperature has the largest impact on the sublimation rate of the TCNE precursor26. The temperature can be modified both by the value set on the temperature controller and also by m...

The organic-based ferrimagnetic semiconductor vanadium tetracyanoethylene (V[TCNE]x, x~2) exhibits room temperature magnetic ordering and promises the advantages of organic materials for magnetoelectronic applications, such as flexibility, low cost production, and chemical tunability. Previous studies have demonstrated functionality in spintronic devices, including hybrid organic/inorganic1,2 and all-organic spin valves3, and as a spin polarizer in an active organic/inorganic semiconductor heterostructure4. In addition, V[TCNE]x~2 has demonstrated promise for inclusion in high frequency electronics due to its extremely narrow ferromagnetic resonance linewidth5.
There are four different methods which have been established for synthesizing V[TCNE]x~26-9. V[TCNE]x~2 was first synthesized as powder in dichloromethane via reaction of TCNE and V(C6H6)6. These powders exhibited the first room temperature magnetic ordering observed in an organic-based material. However, the powder form of this material is extremely air sensitive, limiting its application in thin film devices. In 2000, a chemical vapor deposition (CVD) method was established for creating V[TCNE]x~2 thin films7. More recently physical vapor deposition (PVD)8 and molecular layer deposition (MLD)9 have also been used to fabricate thin films. The PVD method requires an ultra-high vacuum (UHV) system and both PVD and mLD methods require extremely long times to grow films thicker than 100 nm, whereas the CVD films can easily be deposited in thicknesses ranging from 30 nm to several microns. In addition to the variety of thicknesses available with the CVD method, extensive studies have yielded optimized films that consistently show high quality magnetic properties including: narrow ferromagnetic resonance (FMR) linewidth (1.5 G), high Curie temperature (600 K), and sharp magnetic switching5.
Magnetic ordering in V[TCNE]x~2 thin films proceeds via an unconventional route. SQUID magnetometry measurements show strong local magnetic ordering, but the absence of X-ray diffraction peaks and featureless transmission electron microscopy (TEM)10 morphology reveal a lack of long-range structural order. However, extended X-ray absorption fine-structure (EXAFS) studies11 show that each vanadium ion is octahedrally coordinated with six different TCNE molecules, indicating a robust local structural order with a vanadium-nitrogen bond length of 2.084(5) &#197;. Magnetism arises from an antiferromagnetic exchange coupling between the unpaired spins of the TCNE- radical anions, which are distributed across the entire TCNE- molecule , and the spins on the V2+ ions, leading to a local ferrimagnetic ordering with TC ~ 600 K for optimized films5. In addition to exhibiting room temperature magnetic ordering, V[TCNE]x~2 films are semiconducting with 0.5 eV bandgap12. Other properties of note include possible sperimagnetism below a freezing temperature of ~150 K13,14, anomalous positive magnetoresistance12,15,16, and photo-induced magnetism13,17,18.
The CVD method for synthesizing V[TCNE]x~2 thin films is compatible with a variety of substrates due to low temperature (&#60;60 &#176;C) and conformal deposition. Previous studies have shown successful deposition of V[TCNE]x~2 on both rigid and flexible substrates7. Further, this deposition technique lends itself to tuning through modification of precursors and growth parameters.19-22 While the protocol shown here yields the most optimized films to date, significant progress has been made in improving some of the film properties since the discovery of this method and further gains may be possible.

<table border="0" cellpadding="0" cellspacing="0">
	<tbody>
		<tr>
			<td></td>
			<td></td>
			<td></td>
			<td>Equipment</td>
		</tr>
		<tr>
			<td>Nitrogen Glovebox</td>
			<td>Vacuum Atmospheres</td>
			<td>Omni</td>
			<td>steps done in nitrogen glovebox can also be done in an argon glovebox</td>
		</tr>
		<tr>
			<td>1 L three-neck round bottom flask</td>
			<td>Corning</td>
			<td>4965A-1L</td>
			<td></td>
		</tr>
		<tr>
			<td>500 mL round bottom flask</td>
			<td>Sigma Aldrich</td>
			<td>64678</td>
			<td></td>
		</tr>
		<tr>
			<td>Turbo vacuum pumping station</td>
			<td>Agilent Varian</td>
			<td>G8701A-011-037</td>
			<td></td>
		</tr>
		<tr>
			<td>Glass Stopcock</td>
			<td>Kontes</td>
			<td>185000-2440</td>
			<td></td>
		</tr>
		<tr>
			<td>Glass two way connecting tube</td>
			<td>Corning</td>
			<td>8940-24</td>
			<td>Corning Pyrex(R) 105 degree Angled Tube Adapter with Two-Way 24/40 Standard Taper Joint</td>
		</tr>
		<tr>
			<td>Coldfinger</td>
			<td></td>
			<td></td>
			<td>Custom part made by OSU chemistry glass shop</td>
		</tr>
		<tr>
			<td>Argon Glovebox</td>
			<td>Vacuum Atmospheres</td>
			<td>Nexus I</td>
			<td></td>
		</tr>
		<tr>
			<td>Hot plate stirrer</td>
			<td>Corning</td>
			<td>6795</td>
			<td></td>
		</tr>
		<tr>
			<td>Thermoeletric cooler</td>
			<td>Advanced Thermoelectric</td>
			<td>TCP-50</td>
			<td></td>
		</tr>
		<tr>
			<td>Temperature controller</td>
			<td>Advanced Thermoelectric</td>
			<td>TLZ10</td>
			<td>for TE cooler</td>
		</tr>
		<tr>
			<td>Power supply</td>
			<td>Advanced Thermoelectric</td>
			<td>PS-145W-12V&#160;</td>
			<td>for TE cooler and temperature controller</td>
		</tr>
		<tr>
			<td>Temperature controller</td>
			<td>J-Kem&#160; Scientific</td>
			<td>Model 150</td>
			<td>For heating coil</td>
		</tr>
		<tr>
			<td>Heating wire</td>
			<td>Pelican Wire Company</td>
			<td>Nichrome 60</td>
			<td></td>
		</tr>
		<tr>
			<td>Custom glassware pieces</td>
			<td></td>
			<td></td>
			<td>Made by OSU Chemistry glass shop</td>
		</tr>
		<tr>
			<td>Vacuum pump</td>
			<td>BOC Edwards</td>
			<td>XDS-5</td>
			<td>Connected to the CVD set-up</td>
		</tr>
		<tr>
			<td>Flow meter</td>
			<td>Gilmont</td>
			<td>GF-2260</td>
			<td></td>
		</tr>
		<tr>
			<td>Micrometer valve</td>
			<td>Gilmont</td>
			<td>7300</td>
			<td>Controls flow of argon over TCNE</td>
		</tr>
		<tr>
			<td>Micrometer valve</td>
			<td>Gilmont</td>
			<td>7100</td>
			<td>Controls flow of argon over&#160; V(CO)6</td>
		</tr>
		<tr>
			<td>Tubing</td>
			<td>Tygon</td>
			<td>R3603</td>
			<td>1/8 in walls, connected between valves and meter</td>
		</tr>
		<tr>
			<td>3-way Stopcock</td>
			<td>Nalgene</td>
			<td>6470</td>
			<td>used to adjust the flow rates</td>
		</tr>
		<tr>
			<td>Pressure gauge</td>
			<td>Matheson</td>
			<td>63-4105</td>
			<td>connects to the top of Figure 1 part A</td>
		</tr>
		<tr>
			<td>SQUID magnetometer</td>
			<td>Quantum Design</td>
			<td>MPMS-XL</td>
			<td></td>
		</tr>
		<tr>
			<td>EPR</td>
			<td>Bruker</td>
			<td>Elexsys</td>
			<td></td>
		</tr>
		<tr>
			<td>PPMS</td>
			<td>Quantum Design</td>
			<td>14T PPMS</td>
			<td></td>
		</tr>
		<tr>
			<td>Sourcemeter</td>
			<td>Keithely&#160;</td>
			<td>2400</td>
			<td></td>
		</tr>
		<tr>
			<td></td>
			<td></td>
			<td></td>
			<td></td>
		</tr>
		<tr>
			<td></td>
			<td></td>
			<td></td>
			<td></td>
		</tr>
		<tr>
			<td></td>
			<td></td>
			<td></td>
			<td></td>
		</tr>
		<tr>
			<td></td>
			<td></td>
			<td></td>
			<td></td>
		</tr>
		<tr>
			<td></td>
			<td></td>
			<td></td>
			<td>Materials</td>
		</tr>
		<tr>
			<td>Sodium metal</td>
			<td>Sigma Aldrich</td>
			<td>262714</td>
			<td></td>
		</tr>
		<tr>
			<td>Anthracene</td>
			<td>Sigma Aldrich</td>
			<td>141062</td>
			<td></td>
		</tr>
		<tr>
			<td>Anhydrous tetrahydrofuran</td>
			<td>Sigma Aldrich</td>
			<td>186562</td>
			<td></td>
		</tr>
		<tr>
			<td>Vanadium(III) chloride tetrahydrofuran complex</td>
			<td>Sigma Aldrich</td>
			<td>395382</td>
			<td></td>
		</tr>
		<tr>
			<td>Carbon monoxide gas</td>
			<td>OSU stores</td>
			<td>98610</td>
			<td></td>
		</tr>
		<tr>
			<td>Tetraethylammonium bromide</td>
			<td>Sigma Aldrich</td>
			<td>241059</td>
			<td></td>
		</tr>
		<tr>
			<td>Phosphoric acid</td>
			<td>Sigma Aldrich</td>
			<td>79622</td>
			<td></td>
		</tr>
		<tr>
			<td>Methanol</td>
			<td>Sigma Aldrich</td>
			<td>14262</td>
			<td></td>
		</tr>
		<tr>
			<td>Silcone oil</td>
			<td>Sigma Aldrich</td>
			<td>146153</td>
			<td></td>
		</tr>
		<tr>
			<td>Copper pellets</td>
			<td></td>
			<td></td>
			<td>Cut from spare copper wire</td>
		</tr>
		<tr>
			<td>Tetracyanoethylene</td>
			<td>Sigma Aldrich</td>
			<td>T8809</td>
			<td></td>
		</tr>
		<tr>
			<td>Glass slides</td>
			<td>Gold Seal</td>
			<td>3010</td>
			<td></td>
		</tr>
		<tr>
			<td>Activated Charcoal</td>
			<td>Sigma Aldrich</td>
			<td>242276</td>
			<td></td>
		</tr>
	</tbody>
</table>

chemical vapor deposition of an organic magnet, vanadium tetracyanoethylene

Recent progress in the field of organic materials has yielded devices such as organic light emitting diodes (OLEDs) which have advantages not found in traditional materials, including low cost and mechanical flexibility. In a similar vein, it would be advantageous to expand the use of organics into high frequency electronics and spin-based electronics. This work presents a synthetic process for the growth of thin films of the room temperature organic ferrimagnet, vanadium tetracyanoethylene (V[TCNE]x, x~2) by low temperature chemical vapor deposition (CVD). The thin film is grown at &#60;60 &#176;C, and can accommodate a wide variety of substrates including, but not limited to, silicon, glass, Teflon and flexible substrates. The conformal deposition is conducive to pre-patterned and three-dimensional structures as well. Additionally this technique can yield films with thicknesses ranging from 30 nm to several microns. Recent progress in optimization of film growth creates a film whose qualities, such as higher Curie temperature (600 K), improved magnetic homogeneity, and narrow ferromagnetic resonance line-width (1.5 G) show promise for a variety of applications in spintronics and microwave electronics.

The first and easiest method for determining if a deposition is successful is to do a visual inspection of the films. The film should appear dark purple with a mirror finish that is uniform across the substrates. If there are spots on the surface of the substrate where there is no V[TCNE]x~2 or it is lighter in color, then this is likely due to the presence of solvents or other impurities on the substrate surface. Additionally the film should be opaque. Unless a thin film was deposited over a short ti...

Watch this Scientific Journal Video about Chemical Vapor Deposition of an Organic Magnet, Vanadium Tetracyanoethylene at JoVE.com

Chemical Vapor Deposition of an Organic Magnet, Vanadium Tetracyanoethylene

We present the synthesis of the organic-based ferrimagnet vanadium tetracyanoethylene (V[TCNE]x, x~2) via low temperature chemical vapor deposition (CVD). This optimized recipe yields an increase in Curie temperature from 400 K to over 600 K and a dramatic improvement in magnetic resonance properties.

Recent progress in the field of organic materials has yielded devices such as organic light emitting diodes (OLEDs) which have advantages not found in ...

chemical-vapor-deposition-an-organic-magnet-vanadium

Research

JoVE Journal

Chemistry

11.4K Views.  The Ohio State University. We present the synthesis of the organic-based ferrimagnet vanadium tetracyanoethylene (V[TCNE]x, x~2) via low temperature chemical vapor deposition (CVD). This optimized recipe yields an increase in Curie temperature from 400 K to over 600 K and a dramatic improvement in magnetic resonance properties.

Video: Chemical Vapor Deposition of an Organic Magnet, Vanadium Tetracyanoethylene

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 ...

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. ...

Analysis of Volatile and Oxidation Sensitive Compounds Using a Cold Inlet System and Electron Impact Mass Spectrometry

This video presents a protocol for the mass spectrometrical analysis of volatile and oxidation sensitive compounds using electron impact ionization. The analysis of volatile and oxidation sensitive compounds by mass spectrometry is not easily achieved, as all state-of-the-art mass spectrometric methods require at least one sample preparation step, e.g., dissolution and dilution of the analyte (electrospray ionization), co-crystallization of the analyte with a matrix compound (matrix-assisted laser desorption/ionization), or transfer of the prepared samples into the ionization source of the mass spectrometer, to be conducted under atmospheric conditions. Here, the use of a sample inlet system is described which enables the analysis of volatile metal organyls, silanes, and phosphanes using a sector field mass spectrometer equipped with an electron impact ionization source. All sample preparation steps and the sample introduction into the ion source of the mass spectrometer take place either under air-free conditions or under vacuum, enabling the analysis of compounds highly susceptible to oxidation. The presented technique is especially of interest for inorganic chemists, working with metal organyls, silanes, or phosphanes, which have to be handled using inert conditions, such as the Schlenk technique. The principle of operation is presented in this video.

This video presents a protocol for the mass spectrometrical analysis of volatile and oxidation sensitive compounds using electron impact ionization. The presented technique is especially of interest for inorganic chemists, working with metal organyls, silanes, or phosphanes which have to be handled using inert conditions, such as the Schlenk technique.

This video presents a protocol for the mass spectrometrical analysis of volatile and oxidation sensitive compounds using electron impact ionization. The ...

Preparation of Macroporous Epitaxial Quartz Films on Silicon by Chemical Solution Deposition

This work describes the detailed protocol for preparing piezoelectric macroporous epitaxial quartz films on silicon(100) substrates. This is a three-step process based on the preparation of a sol in a one-pot synthesis which is followed by the deposition of a gel film on Si(100) substrates by evaporation induced self-assembly using the dip-coating technique and ends with a thermal treatment of the material to induce the gel crystallization and the growth of the quartz film. The formation of a silica gel is based on the reaction of a tetraethyl orthosilicate and water, catalyzed by HCl, in ethanol. However, the solution contains two additional components that are essential for preparing mesoporous epitaxial quartz films from these silica gels dip-coated on Si. Alkaline earth ions, like Sr2+ act as glass melting agents that facilitate the crystallization of silica and in combination with cetyl trimethylammonium bromide (CTAB) amphiphilic template form a phase separation responsible of the macroporosity of the films. The good matching between the quartz and silicon cell parameters is also essential in the stabilization of quartz over other SiO2 polymorphs and is at the origin of the epitaxial growth.

A protocol is presented for the preparation of piezoelectric macroporous epitaxial films of quartz on silicon by solution chemistry using dip-coating and thermal treatments in air.

This work describes the detailed protocol for preparing piezoelectric macroporous epitaxial quartz films on silicon(100) substrates. This is a three-step ...

Synthesis and Characterization of Supramolecular Colloids

Control over colloidal assembly is of utmost importance for the development of functional colloidal materials with tailored structural and mechanical properties for applications in photonics, drug delivery and coating technology. Here we present a new family of colloidal building blocks, coined supramolecular colloids, whose self-assembly is controlled through surface-functionalization with a benzene-1,3,5-tricarboxamide (BTA) derived supramolecular moiety. Such BTAs interact via directional, strong, yet reversible hydrogen-bonds with other identical BTAs. Herein, a protocol is presented that describes how to couple these BTAs to colloids and how to quantify the number of coupling sites, which determines the multivalency of the supramolecular colloids. Light scattering measurements show that the refractive index of the colloids is almost matched with that of the solvent, which strongly reduces the van der Waals forces between the colloids. Before photo-activation, the colloids remain well dispersed, as the BTAs are equipped with a photo-labile group that blocks the formation of hydrogen-bonds. Controlled deprotection with UV-light activates the short-range hydrogen-bonds between the BTAs, which triggers the colloidal self-assembly. The evolution from the dispersed state to the clustered state is monitored by confocal microscopy. These results are further quantified by image analysis with simple routines using ImageJ and Matlab. This merger of supramolecular chemistry and colloidal science offers a direct route towards light- and thermo-responsive colloidal assembly encoded in the surface-grafted monolayer.

A protocol for the synthesis and characterization of colloids coated with supramolecular moieties is described. These supramolecular colloids undergo self-assembly upon the activation of the hydrogen-bonds between the surface-anchored molecules by UV-light.

Control over colloidal assembly is of utmost importance for the development of functional colloidal materials with tailored structural and mechanical ...

Epitaxial Growth of Perovskite Strontium Titanate on Germanium via Atomic Layer Deposition

Atomic layer deposition (ALD) is a commercially utilized deposition method for electronic materials. ALD growth of thin films offers thickness control and conformality by taking advantage of self-limiting reactions between vapor-phase precursors and the growing film. Perovskite oxides present potential for next-generation electronic materials, but to-date have mostly been deposited by physical methods. This work outlines a method for depositing SrTiO3 (STO) on germanium using ALD. Germanium has higher carrier mobilities than silicon and therefore offers an alternative semiconductor material with faster device operation. This method takes advantage of the instability of germanium's native oxide by using thermal deoxidation to clean and reconstruct the Ge (001) surface to the 2&#215;1 structure. 2-nm thick, amorphous STO is then deposited by ALD. The STO film is annealed under ultra-high vacuum and crystallizes on the reconstructed Ge surface. Reflection high-energy electron diffraction (RHEED) is used during this annealing step to monitor the STO crystallization. The thin, crystalline layer of STO acts as a template for subsequent growth of STO that is crystalline as-grown, as confirmed by RHEED. In situ X-ray photoelectron spectroscopy is used to verify film stoichiometry before and after the annealing step, as well as after subsequent STO growth. This procedure provides framework for additional perovskite oxides to be deposited on semiconductors via chemical methods in addition to the integration of more sophisticated heterostructures already achievable by physical methods.

This work details the procedures for the growth and characterization of crystalline SrTiO3 directly on germanium substrates by atomic layer deposition. The procedure illustrates the ability of an all-chemical growth method to integrate oxides monolithically onto semiconductors for metal-oxide semiconductor devices.

Atomic layer deposition (ALD) is a commercially utilized deposition method for electronic materials. ALD growth of thin films offers thickness control and ...

Fizzy Extraction of Volatile Organic Compounds Combined with Atmospheric Pressure Chemical Ionization Quadrupole Mass Spectrometry

Chemical analysis of volatile and semivolatile compounds dissolved in liquid samples can be challenging. The dissolved components need to be brought to the gas phase, and efficiently transferred to a detection system. Fizzy extraction takes advantage of the effervescence phenomenon. First, a carrier gas (here, carbon dioxide) is dissolved in the sample by applying overpressure and stirring the sample. Second, the sample chamber is decompressed abruptly. Decompression leads to the formation of numerous carrier gas bubbles in the sample liquid. These bubbles assist the release of the dissolved analyte species from the liquid to the gas phase. The released analytes are immediately transferred to the atmospheric pressure chemical ionization interface of a triple quadrupole mass spectrometer. The ionizable analyte species give rise to mass spectrometric signals in the time domain. Because the release of the analyte species occurs over short periods of time (a few seconds), the temporal signals have high amplitudes and high signal-to-noise ratios. The amplitudes and areas of the temporal peaks can then be correlated with concentrations of the analytes in the liquid samples subjected to fizzy extraction, which enables quantitative analysis. The advantages of fizzy extraction include: simplicity, speed, and limited use of chemicals (solvents).

Fizzy extraction is a new laboratory technique for analysis of volatile and semivolatile compounds. A carrier gas is dissolved in the liquid sample by applying overpressure and stirring the sample. The sample chamber is then decompressed. The analyte species are liberated to the gas phase due to effervescence.

Chemical analysis of volatile and semivolatile compounds dissolved in liquid samples can be challenging. The dissolved components need to be brought to ...

Aerosol-assisted Chemical Vapor Deposition of Metal Oxide Structures: Zinc Oxide Rods

Whilst columnar zinc oxide (ZnO) structures in the form of rods or wires have been synthesized previously by different liquid- or vapor-phase routes, their high cost production and/or incompatibility with microfabrication technologies, due to the use of pre-deposited catalyst-seeds and/or high processing temperatures exceeding 900 &#176;C, represent a drawback for a widespread use of these methods. Here, however, we report the synthesis of ZnO rods via a non-catalyzed vapor-solid mechanism enabled by using an aerosol-assisted chemical vapor deposition (CVD) method at 400 &#176;C with zinc chloride (ZnCl2) as the precursor and ethanol as the carrier solvent. This method provides both single-step formation of ZnO rods and the possibility of their direct integration with various substrate types, including silicon, silicon-based micromachined platforms, quartz, or high heat resistant polymers. This potentially facilitates the use of this method at a large-scale, due to its compatibility with state-of-the-art microfabrication processes for device manufacture. This report also describes the properties of these structures (e.g., morphology, crystalline phase, optical band gap, chemical composition, electrical resistance) and validates its gas sensing functionality towards carbon monoxide.

Columnar zinc oxide structures in the form of rods are synthesized via aerosol-assisted chemical vapor deposition without the use of pre-deposited catalyst-seed particles. This method is scalable and compatible with various substrates based on either silicon, quartz or polymers.

Whilst columnar zinc oxide (ZnO) structures in the form of rods or wires have been synthesized previously by different liquid- or vapor-phase routes, ...

Controlled Photoredox Ring-Opening Polymerization of O-Carboxyanhydrides Mediated by Ni/Zn Complexes

Here, we describe an effective protocol that combines photoredox Ni/Ir catalysis with the use of a Zn-alkoxide for efficient ring-opening polymerization, allowing for the synthesis of isotactic poly(&#945;-hydroxy acids) with expected molecular weights (&#62;140 kDa) and narrow molecular weight distributions (Mw/Mn &#60; 1.1). This ring-opening polymerization is mediated by Ni and Zn complexes in the presence of an alcohol initiator and a photoredox Ir catalyst, irradiated by a blue LED (400 - 500 nm). The polymerization is performed at a low temperature (-15 &#176;C) to avoid undesired side reactions. The complete monomer consumption can be achieved within 4 - 8 hours, providing a polymer close to the expected molecular weight with narrow molecular weight distribution. The resulted number-average molecular weight shows a linear correlation with the degree of polymerization up to 1000. The homodecoupling 1H NMR study confirms that the obtained polymer is isotactic without epimerization. This polymerization reported herein offers a strategy for achieving rapid, controlled O-carboxyanhydrides polymerization to prepare stereoregular poly(&#945;-hydroxy acids) and its copolymers bearing various functional side-chain groups.

Controlled Photoredox Ring-Opening Polymerization of O-Carboxyanhydrides Mediated by Ni/Zn Complexes

A protocol for the controlled photoredox ring-opening polymerization of O-carboxyanhydrides mediated by Ni/Zn complexes is presented.

Here, we describe an effective protocol that combines photoredox Ni/Ir catalysis with the use of a Zn-alkoxide for efficient ring-opening polymerization, ...

Reactive Vapor Deposition of Conjugated Polymer Films on Arbitrary Substrates

We demonstrate a method of conformally coating conjugated polymers on arbitrary substrates using a custom-designed, low-pressure reaction chamber. Conductive polymers, poly(3,4-ethylenedioxythiophene) (PEDOT) and poly(3,4-propylenedioxythiophene) (PProDOT), and a semiconducting polymer, poly(thieno[3,2-b]thiophene) (PTT), were deposited on unconventional highly-disordered and textured substrates with high surface areas, such as paper, towels and fabrics. This reported deposition chamber is an improvement of previous vapor reactors because our system can accommodate both volatile and nonvolatile monomers, such as 3,4-propylenedioxythiophene and thieno[3,2-b]thiophene. Utilization of both solid and liquid oxidants are also demonstrated. One limitation of this method is that it lacks sophisticated in situ thickness monitors. Polymer coatings made by the commonly used solution-based coating methods, such as spin-coating and surface grafting, are often not uniform or susceptible to mechanical degradation. This reported vapor phase deposition method overcomes those drawbacks and is a strong alternative to common solution-based coating methods. Notably, polymer films coated by the reported method are uniform and conformal on rough surfaces, even at a micrometer scale. This feature allows for future application of vapor deposited polymers in electronics devices on flexible and highly textured substrates.

This paper presents a protocol for reactive vapor deposition of poly(3,4-ethylenedioxythiophene), poly(3,4-propylenedioxythiophene), and poly(thieno[3,2-b]thiophene) films on glass slides and rough substrates, such as textiles and paper.