The authors thank Chris Mortimer, Chris Rhodes (Department of Chemistry workshops) and Kari Niemi (York Plasma Institute) for their help with the equipment. The work was supported by the Leverhulme Trust (grant No. RPG-2013-079) and EPSRC (EP/H003797/1 &amp; EP/K018388/1).

1. Shielding the Plasma Setup
<ol>
	<li>Position all parts of the electric environment inside the cage: power supply, voltage/current meter, power cable, plasma electrodes, plasma jet, etc.</li>
	<li>Make sure that the space within the cage is sufficient so that the live electrode, the ground electrode and respective cables are not in contact with each other or the metal mesh.</li>
	<li>Equip the cage with an interlock connected to the plasma power supply to avoid the risk of electric shock from the high voltage electrode during the plasma operation.</li>
	<li>Place the voltage and frequency controls on the outer surface of the cage to allow changing of the parameters without interrupting the plasma operation.</li>
	<li>Ground all metal supports inside the mesh cage and the cage itself by wiring them to an earth bonding plug.</li>
</ol>
2. Discharge Parameters
<ol>
	<li>Position the live electrode below the ground electrode on the glass tube (i.e., closer to the tube nozzle).</li>
	<li>Connect the voltage probe to the plasma power supply to measure the operating voltage, and pass the ground electrode through the circular current probe to monitor the return current.</li>
	<li>Connect both the voltage and the current probe to an oscilloscope, monitoring the current, the voltage and the plasma operating frequency (determined by either the current or the voltage probe).</li>
	<li>Set the flow of gas through the glass tube to 2 slm using the mass flow controllers (MFCs).</li>
	<li>Ignite the plasma in a glass tube with the feed gas helium passing through it by turning on the plasma power supply. Using the readings from the probes, set the voltage and frequency of the discharge to 18 kV and 25 kHz, respectively. 
	NOTE: Parameter variations are carried out to determine the minimal voltage and frequency at which the discharge is occurring with the highest molecular content of all the experiments. The increased molecular content requires higher voltage for the plasma to be ignited. Note that elevated voltages can result in significant gas temperature increase of the plasma, thus leading to increased evaporation of the liquid sample.</li>
	<li>Keep the voltage constant in all experiments.</li>
</ol>
3. Introducing Admixtures to the Feed Gas
<ol>
	<li>Connect the second MFC to the main feed gas tubing using a T-connector.</li>
	<li>To add the water vapor to the feed gas, direct an MFC-regulated flow of helium through a Drechsel flask filled with water and positioned outside (on top or on the side) of the mesh cage.</li>
	<li>Obtain a desired level of saturation by splitting the flow of the feed gas. Direct 10% of the gas flow (200 sccm) through the Drechsel flask with water (H216O) to achieve a 10% saturation of the feed gas.</li>
	<li>Using the T-connector, combine this fully water vapor-saturated gas with the 90% (1,800 sccm) of the dry gas flow.</li>
</ol>
4. The Reactor
<ol>
	<li>Prepare a glass reactor consisting of two parts, upper and lower. Equip the lower part of the with an exhaust tube.</li>
	<li>Position the glass reactor at the nozzle of the plasma jet.</li>
	<li>Insert the plasma jet nozzle into a rubber grommet inside the opening in the upper part of the reactor.</li>
	<li>Prepare the container consisting of a well-like reservoir on top of a stand. Make both the stand and the well from a dielectric material (e.g., glass, quartz glass).</li>
	<li>Place the sample container inside the reactor so that it is exposed to the plasma effluent from the nozzle of the jet.</li>
	<li>Put a liquid H217O sample inside the sample container. For the detection of the hydroxyl radicals, use a solution of the 5,5-dimethyl-1-pyrroline-N-oxide (DMPO) spin trap (see 5.1). 
	NOTE: The choice of the spin trap as well as the choice of the liquid sample components depends on the specific species investigated. For example, the source of the &#8226;OH radical is studied using H216O/H217O and DMPO spin trap. The source of &#8226;H radical requires the use of an H2O/D2O (gas and liquid). N-tert-Butyl-&#945;-phenylnitrone (PBN) should be used for the detection of the &#8226;H radical. In the case of He plasma with H2O vapor, it was shown to predominantly trap hydrogen radical, while DMPO formed mostly DMPO-OH adduct15.</li>
	<li>Connect the two reactor parts via the ground glass surfaces contact.</li>
</ol>
5. Spin Trapping of Radical Species
<ol>
	<li>Prepare the solutions of the chosen spin trap with the required concentration. For aqueous solutions, use de-ionized water. For nitrone spin traps (such as DMPO), use a 100 mM concentration.</li>
	<li>Pre-flush the reactor with the feed gas (2 slm) for 30 sec.</li>
	<li>Ignite the plasma (see 2.5) and expose the liquid sample to the plasma effluent for a set period of time (e.g., 60 sec).</li>
	<li>After a required exposure time, switch off the plasma power supply and open the reactor. Remove the sample container from the reactor.</li>
	<li>Collect the sample and analyze it using the electron paramagnetic resonance spectroscopy (EPR)15.</li>
</ol>

<ol>
	<li>Boxhammer, V., 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=Bactericidal+action+of+cold+atmospheric+plasma+in+solution.">Bactericidal action of cold atmospheric plasma in solution.</a> New J. Phys. 14, 113042 (2012).</li><li>Graves, D. B. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=The+emerging+role+of+reactive+oxygen+and+nitrogen+species+in+redox+biology+and+some+implications+for+plasma+applications+to+medicine+and+biology.">The emerging role of reactive oxygen and nitrogen species in redox biology and some implications for plasma applications to medicine and biology.</a> J. Phys. D: Appl. Phys. 45, 263001 (2012).</li><li>von Woedtke, T., Reuter, S., Masur, K., Weltmann, K. -. D. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Plasmas+for+medicine.">Plasmas for medicine.</a> Phys. Rep. 530, 291-320 (2013).</li><li>Machala, Z., 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=Formation+of+ROS+and+RNS+in+Water+Electro-Sprayed+through+Transient+Spark+Discharge+in+Air+and+their+Bactericidal+Effects.">Formation of ROS and RNS in Water Electro-Sprayed through Transient Spark Discharge in Air and their Bactericidal Effects.</a> Plasma Proc. Polym. 10, 649-659 (2013).</li><li>Lu, X., 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=Reactive+species+in+non-equilibrium+atmospheric-pressure+plasmas:+Generation,+transport,+and+biological+effects.">Reactive species in non-equilibrium atmospheric-pressure plasmas: Generation, transport, and biological effects.</a> Phys. 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J. Cancer. 112, 1536-1545 (2015).</li><li>Norberg, S. A., Tian, W., Johnsen, E., Kushner, M. J. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Atmospheric+pressure+plasma+jets+interacting+with+liquid+covered+tissue:+touching+and+not-touching+the+liquid.">Atmospheric pressure plasma jets interacting with liquid covered tissue: touching and not-touching the liquid.</a> J. Phys. D: Appl. 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The authors have nothing to disclose.

Here, we demonstrate the use of an in-house built atmospheric pressure plasma setup. The metal mesh cage helps to achieve reproducible plasma conditions with minimized interference from external fields, at the same time protecting nearby sensitive equipment from possible interference and/or damage by any plasma-induced fields. The shielding (caging) of the setup depends on the type of operated plasma and its electrical characteristics. The aim is to ensure the absence of external interference on the plasma operation and avoid the plasma fields interfering with surrounding equipment. In this case the mesh size is 22 mm, however, reduced mesh size may be required for different plasmas. The plasma operation parameters were controlled using a voltage and a current probe connected to an oscilloscope. The introduction of the high voltage probe significantly changes the electric environment, and therefore the probe must become part of the electrical system and be positioned the same way throughout all of the experiments.
The use of the glass reactor encapsulating the sample and the plasma jet allows exclusion of the ambient atmosphere of often unknown composition from the reaction system. In the presented results (vide supra), it was used to determine the source of the plasma-induced reactive oxygen species in the aqueous sample exposed to the plasma effluent. Such investigation is possible if the molecules of the liquid water and the water in the feed gas (vapor) can be differentiated. To determine whether the hydroxyl radicals were formed in the gas phase or from the liquid water molecules, isotopically labelled water was introduced: H217O as the liquid medium, H216O vapor in the feed gas. If a hypothetical experiment was conducted in an open atmosphere, distinguishing between the two phases would have been hampered by the presence of the water vapor in the surrounding air. An alternative method to minimize the influence of the surrounding atmosphere was demonstrated in the literature, in which the diffusion of the species from the atmosphere into the plasma effluent was prevented using a shielding gas17. The shielding gas (N2 or O2) creates a gas curtain with a known composition18. The reactor presented in this manuscript is a simple way to remove the influence of the ambient air components (such as water vapor), and can be used with different plasma jets without the introduction of the additional gas flow. Similar to the &#8226;OH radical, the source of the &#8226;H radical can be determined by employing a D2O/H2O system. The inexpensive D2O can also be introduced into the feed gas as a vapor as described above.
The saturation of the gas with H2O vapor was determined by weighing the Drechsel flask before and after bubbling the gas flow through it. The relative humidity (i.e., saturation) of the gas is calculated by the amount of the water evaporated and the volume of gas passed through.
Note that in prolonged experiments, the temperature of the liquid in the Drechsel flask may decrease due to the evaporation. The relative humidity is calculated for a specific temperature. The calculated values are further compared with those in literature19 to determine the relative humidity of the feed gas. We have empirically discovered that a flow of up to 2 slm of He through a water-filled Drechsel flask fully saturates the gas with water vapor. However, elevated flow rates may not allow sufficient residence time of the gas in the liquid for full saturation. Other saturation techniques may be required.
Another challenging task is ensuring that no surrounding air is present in the system. The reactor is pre-flushed with the feed gas to remove the residual air. The time required for pre-flushing will depend on the volume of the reactor and the flow of the feed gas. The absence of external ambient air diffusion and entrainment into the system such as a helium feed gas plasma system can be tested using an &#8226;NO radical trapping reaction. Nitric oxide generated by plasma from N2 and O2 molecules of air can be detected by EPR as a radical adduct of the (MGD)2Fe2+ complex20 (MGD = N-methyl-D-glucamine dithiocarbamate). In the case of the complete absence of air, the EPR signal of the adduct is not observed. The absence of external water molecules in the reactor can be demonstrated by the following experiment. A liquid sample of D2O is exposed to a dry feed gas plasma. The NMR analysis of the post-exposure sample reveals the amount of H2O brought into the liquid during the exposure. This allows to estimate the amount of the residual H2O in the tubing used for the feed gas15 in the experiment.
The sample container design is crucial in the experimental work. Initially, we have attempted using plastic and glass microcentrifuge tubes. Together with relatively high plasma feed gas flow, the small diameter of the opening does not let the surrounding air penetrate the microcentrifuge tube. However, this has many disadvantages. The plasma exhibited arching and large temperature increase near the edges of the microcentrifuge tube. The delivery of the species from the gas phase into the liquid was also significantly less efficient due to the different gas phase dynamics and the low surface area (and large volume) of the liquid sample. Thus, the surface area of the liquid sample is crucial for the delivery of the reactive species from the gas phase to the liquid sample. This is especially important for the short-lived radicals. The liquid sample container must therefore be designed to allow the exposed liquid to have high surface area for efficient diffusion. The sample should also have low depth to minimize the convection-related limitations of the liquid sample. It must be taken into account that elevated gas flows and especially with ignited plasma create significant disturbances at the surface of the liquid sample21. Therefore, the sample container has a well-like shape with diameter and depth required for the specific experiment. The height of the stand on which the well is positioned can be adjusted to experimental needs. The rubber grommet through which the plasma jet is inserted into the reactor makes it possible to change the contact angle of the effluent with the liquid.
The presented method allows investigation of the source of the reactive species (&#8226;OH, &#8226;H, etc.) induced in the liquid by a kHz frequency parallel field plasma jet. The method employing a glass reactor surrounding the jet is not limited to the described conditions, and can be used with other atmospheric pressure plasmas. The method allows introduction of any admixtures to the feed gas: vapor, O2, N2, etc. Among its other advantages is the possibility of conducting optical measurements inside it, although in this case optical quality quartz glass must be used as a reactor material. The exhaust tube in the lower part of the reactor allows using the plasma jet in virtually any lab: the exhaust can be connected via plastic tubing to a remote extraction hood. The reactor concept is versatile and can be used in research of different plasmas where controlled atmosphere is required. For example, polymerization of styrene is inhibited by the oxygen species22, but can be observed in the reactor when liquid styrene is exposed to the helium feed gas plasma.

Low-temperature atmospheric pressure plasmas (LTPs) have attracted increased attention in recent years due to their vast potential for biomedical applications1-3. Upon contact with ambient atmosphere, LTP reacts with molecular content of air (N2, O2, H2O vapor), generating a variety of reactive oxygen and nitrogen species (RONS)2,4. Among these are relatively stable species (such as hydrogen peroxide, ozone, nitrite and nitrate anions) and highly reactive radicals (&#8226;OH, &#8226;OOH/O2&#8226;-, &#8226;H, &#8226;NO, etc.). These species, initially generated in the gas phase, are further delivered by the plasma to the biological substrate5. RONS interact with substrates and thus define the antimicrobial, anticancer and antiviral effects of LTP6-8.
The development of LTP therapies requires complex modelling of the reactions of RONS9. Water is an essential part of the biological milieu, and the reactions in the aqueous phase increase the complexity of the system dramatically. The investigation of the gas-phase plasma is widely performed using various analytical techniques, including optical emission spectroscopy, laser induced fluorescence, infrared spectroscopy, mass spectrometry (MS), etc.10-12. At the same time, detailed investigations of the species detected in the liquid phase are still scarce. Available reports describe the use of various analytical methods such as UV and electron paramagnetic resonance (EPR) spectroscopy, cytometry, etc. for the detection of RONS in aqueous solutions13,14. EPR is one of the most direct methods for radical detection in the liquid. However, many radical species cannot be detected by EPR due to their short life time. In these cases, spin trapping is often used. Spin trapping a technique involving a compound (spin trap) which rapidly and selectively reacts with the radical to yield a more persistent radical adduct (e.g., DMPO reacts with the hydroxyl radical, forming DMPO-OH adduct).
The common challenges in plasma-liquid interaction studies are the inability to control the ambient atmosphere around the plasma effluent and other interfering factors (external fields, environment-sensitive power supply parts, etc.). Here, we demonstrate the use of a setup comprising of a metal mesh case containing the operated plasma and an in-house built reactor around the plasma jet nozzle. The metal mesh serves as the Faraday cage, allowing significantly improved reproducibility and general operability of the plasma jet. The glass reactor encapsulates both the plasma jet and the liquid sample, excluding the surrounding atmosphere from the system.
This method can be employed for any atmospheric pressure plasma jet in contact with liquid solutions. For example, we have recently presented an investigation of the source of the reactive oxygen species detected in an aqueous sample exposed to plasma. Isotopically labelled water was used to distinguish between the species formed in the liquid and in the gas phase of the plasma jet-liquid solution system15.

<table border="0" cellpadding="0" cellspacing="0" width="783">
	<tbody>
		<tr height="53">
			<td height="53" style="height:53px;width:255px;">Plasma Resonant and Dielectric Barrier Corona Driver power supply&#160;</td>
			<td style="width:243px;">Information Unlimited</td>
			<td style="width:119px;"></td>
			<td style="width:167px;">PVM500&#160;</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:255px;">Mass flow controller (MFC)</td>
			<td>Brooks Instruments&#160;</td>
			<td style="width:119px;"></td>
			<td>2 slm (He calib.)</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:255px;">MFC</td>
			<td>Brooks Instruments&#160;</td>
			<td style="width:119px;"></td>
			<td>5 slm (He calib.)</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:255px;">Microcomputer controller for MFCs</td>
			<td>Brooks Instruments&#160;</td>
			<td style="width:119px;"></td>
			<td>0254</td>
		</tr>
		<tr height="26">
			<td height="26" style="height:26px;width:255px;">H217O</td>
			<td>Icon Isotopes</td>
			<td style="width:119px;">IO 6245</td>
			<td></td>
		</tr>
		<tr height="45">
			<td height="45" style="height:45px;width:255px;">5,5-dimethyl-1-pyrroline N-oxide&#160;</td>
			<td style="width:243px;">Dojindo Molecular Technologies, Inc.&#160;</td>
			<td style="width:119px;">D048-10</td>
			<td>&#8805;99%</td>
		</tr>
		<tr height="26">
			<td height="26" style="height:26px;width:255px;">2,2,6,6-tetramethylpiperidine 1-oxyl&#160;</td>
			<td style="width:243px;">Sigma-Aldrich</td>
			<td style="width:119px;">214000</td>
			<td>98%</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:255px;">Helium</td>
			<td style="width:243px;">BOC UK</td>
			<td style="width:119px;">110745-V</td>
			<td>99.996%</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:255px;">High voltage probe</td>
			<td style="width:243px;">Tektronix&#160;</td>
			<td style="width:119px;"></td>
			<td>P6015A</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:255px;">Current probe</td>
			<td>Ion Physics Corporation&#160;</td>
			<td style="width:119px;"></td>
			<td>CM-100-L</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:255px;">Oscilloscope</td>
			<td style="width:243px;">Teledyne LeCroy</td>
			<td style="width:119px;"></td>
			<td>WaveJet 354A&#160;</td>
		</tr>
	</tbody>
</table>

an atmospheric pressure plasma setup to investigate the reactive species formation

Non-thermal atmospheric pressure (&#39;cold&#39;) plasmas have received increased attention in recent years due to their significant biomedical potential. The reactions of cold plasma with the surrounding atmosphere yield a variety of reactive species, which can define its effectiveness. While efficient development of cold plasma therapy requires kinetic models, model benchmarking needs empirical data. Experimental studies of the source of reactive species detected in aqueous solutions exposed to plasma are still scarce. Biomedical plasma is often operated with He or Ar feed gas, and a specific interest lies in investigation of the reactive species generated by plasma with various gas admixtures (O2, N2, air, H2O vapor, etc.) Such investigations are very complex due to difficulties in controlling the ambient atmosphere in contact with the plasma effluent. In this work, we addressed common issues of &#39;high&#39; voltage kHz frequency driven plasma jet experimental studies. A reactor was developed allowing the exclusion of ambient atmosphere from the plasma-liquid system. The system thus comprised the feed gas with admixtures and the components of the liquid sample. This controlled atmosphere allowed the investigation of the source of the reactive oxygen species induced in aqueous solutions by He-water vapor plasma. The use of isotopically labelled water allowed distinguishing between the species originating in the gas phase and those formed in the liquid. The plasma equipment was contained inside a Faraday cage to eliminate possible influence of any external field. The setup is versatile and can aid in further understanding the cold plasma-liquid interactions chemistry.

Using the method and equipment described above, we have investigated the origin of the reactive oxygen species in the LTP system in contact with water. The plasma operating frequency and voltage were 25 kHz and 18 kV (peak-to-peak), respectively (Figure 1).
For example, the source of the hydroxyl radical was determined using the isotopically labelled water. This enabled distinguishing between the water molecules in the feed gas from those in the liquid sample. For that, H216O was introduced in the feed gas (as vapor). A liquid sample of H217O with the dissolved spin trap DMPO was positioned in a sample container. The reactor was pre-flushed for 30 sec with the feed gas. Importantly, in this case longer pre-flushing time may result in substantial amount of H216O delivered to the liquid H217O sample. Then, the plasma was ignited and the sample was exposed to the effluent for 60 sec. The post-exposure solution was analyzed by EPR. Two DMPO-OH radical adducts (DMPO-17OH and DMPO-16OH) were detected (Figure 2). The ratio of the adducts formed was determined via further analysis of the EPR data. The MS analysis of the liquid phase composition showed the ratio of H216O (diffused into the liquid from the gas phase) to H217O (Table 1). The comparison of the two suggested that the hydroxyl radicals detected in the liquid were, in fact, originating in the gas phase, and not in the liquid.
Similar studies can be performed by using other systems, such as a D2O/H2O system to detect the source of the &#8226;H (&#8226;D) radical15.
<img alt="Figure 1" src="/files/ftp_upload/54765/54765fig1.jpg" /> 
Figure 1. Setup used for the investigation of the source of reactive oxygen species. The plasma was generated in a quartz glass tube (4 mm internal diameter, 1 mm wall thickness) with the helium feed gas. The feed gas flow was 2 slm. The feed gas contained H2O vapor introduced as stated above. <a href="https://www-jove-com.remotexs.ntu.edu.sg/files/ftp_upload/54765/54765fig1large.jpg" target="_blank">Please click here to view a larger version of this figure.</a>
<img alt="Figure 2" src="/files/ftp_upload/54765/54765fig2.jpg" /> 
Figure 2. An EPR spectrum of the mixture of DMPO-H, DMPO-16OH and DMPO-17OH radical adducts induced in the solution of DMPO in H217O exposed to plasma. The analysis was performed using the spectra simulation software using the hyperfine values available in literature16. <a href="https://www-jove-com.remotexs.ntu.edu.sg/files/ftp_upload/54765/54765fig2large.jpg" target="_blank">Please click here to view a larger version of this figure.</a>
<img alt="Table 1" src="/files/ftp_upload/54765/54765tbl1.jpg" /> 
Table 1. Concentration of the DMPO-16OH and DMPO-17OH radical adducts and the amount of H216O in the liquid H217O sample after the plasma exposure. The absolute quantities of adducts concentrations were obtained using the EPR calibration with the stable radical 2,2,6,6-Tetramethylpiperidine 1-oxyl (TEMPO). In the case of no added water vapor (entry 1), a residual humidity was present in the feed gas. The relative amounts of H217O and H216O in the liquid sample were determined using a hydrolysis reaction of cinnamoyl chloride yielding a mixture 16O- and 17O-cinnamic acids upon reaction with the post-plasma exposure solution. The resulting mixture was analyzed by high resolution mass spectrometry as described elsewhere15.

Watch this Scientific Journal Video about An Atmospheric Pressure Plasma Setup to Investigate the Reactive Species Formation at JoVE.com

An Atmospheric Pressure Plasma Setup to Investigate the Reactive Species Formation

An experimental setup was created for the helium-operated kHz frequency plasma jet. The setup includes a cage for the plasma power supply and jet and an in-house built reactor to monitor plasma-induced reactive species without the interference of the ambient atmosphere.

Non-thermal atmospheric pressure (&#39;cold&#39;) plasmas have received increased attention in recent years due to their significant biomedical potential. ...

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9.8K Views.  University of York. An experimental setup was created for the helium-operated kHz frequency plasma jet. The setup includes a cage for the plasma power supply and jet and an in-house built reactor to monitor plasma-induced reactive species without the interference of the ambient atmosphere. 

Video: An Atmospheric Pressure Plasma Setup to Investigate the Reactive Species Formation

Encapsulation and Permeability Characteristics of Plasma Polymerized Hollow Particles

In this protocol, core-shell nanostructures are synthesized by plasma enhanced chemical vapor deposition. We produce an amorphous barrier by plasma polymerization of isopropanol on various solid substrates, including silica and potassium chloride. This versatile technique is used to treat nanoparticles and nanopowders with sizes ranging from 37 nm to 1 micron, by depositing films whose thickness can be anywhere from 1 nm to upwards of 100 nm. Dissolution of the core allows us to study the rate of permeation through the film. In these experiments, we determine the diffusion coefficient of KCl through the barrier film by coating KCL nanocrystals and subsequently monitoring the ionic conductivity of the coated particles suspended in water. The primary interest in this process is the encapsulation and delayed release of solutes. The thickness of the shell is one of the independent variables by which we control the rate of release. It has a strong effect on the rate of release, which increases from a six-hour release (shell thickness is 20 nm) to a long-term release over 30 days (shell thickness is 95 nm). The release profile shows a characteristic behavior: a fast release (35% of the final materials) during the first five minutes after the beginning of the dissolution, and a slower release till all of the core materials come out.

We have used plasma enhanced chemical vapor deposition to deposit thin films ranging from a few nm to several 100 nm on nano-sized particles of various materials. We subsequently etch the core material to produce hollow nanoshells whose permeability is controlled by the thickness of the shell. We characterize the permeability of these coatings to small solutes and demonstrate that these barriers can provide sustained release of the core material over several days.

In this protocol, core-shell nanostructures are synthesized by plasma enhanced chemical vapor deposition. We produce an amorphous barrier by plasma ...

Synthesis and Microdiffraction at Extreme Pressures and Temperatures

High pressure compounds and polymorphs are investigated for a broad range of purposes such as determine structures and processes of deep planetary interiors, design materials with novel properties, understand the mechanical behavior of materials exposed to very high stresses as in explosions or impacts. Synthesis and structural analysis of materials at extreme conditions of pressure and temperature entails remarkable technical challenges. In the laser heated diamond anvil cell (LH-DAC), very high pressure is generated between the tips of two opposing diamond anvils forced against each other; focused infrared laser beams, shined through the diamonds, allow to reach very high temperatures on samples absorbing the laser radiation. When the LH-DAC is installed in a synchrotron beamline that provides extremely brilliant x-ray radiation, the structure of materials under extreme conditions can be probed in situ. LH-DAC samples, although very small, can show highly variable grain size, phase and chemical composition. In order to obtain the high resolution structural analysis and the most comprehensive characterization of a sample, we collect diffraction data in 2D grids and combine powder, single crystal and multigrain diffraction techniques. Representative results obtained in the synthesis of a new iron oxide, Fe4O5 1 will be shown.

The laser heated diamond anvil cell combined with synchrotron micro-diffraction techniques allows researchers to explore the nature and properties of new phases of matter at extreme pressure and temperature (PT) conditions. Heterogeneous samples can be characterized in situ under high pressure by 2D mapping and combined powder, single-crystal and multigrain diffraction approaches.

High pressure compounds and polymorphs are investigated for a broad range of purposes such as determine structures and processes of deep planetary ...

Using Neutron Spin Echo Resolved Grazing Incidence Scattering to Investigate Organic Solar Cell Materials

The spin echo resolved grazing incidence scattering (SERGIS) technique has been used to probe the length-scales associated with irregularly shaped crystallites. Neutrons are passed through two well defined regions of magnetic field; one before and one after the sample. The two magnetic field regions have opposite polarity and are tuned such that neutrons travelling through both regions, without being perturbed, will undergo the same number of precessions in opposing directions. In this case the neutron precession in the second arm is said to &#34;echo&#34; the first, and the original polarization of the beam is preserved. If the neutron interacts with a sample and scatters elastically the path through the second arm is not the same as the first and the original polarization is not recovered. Depolarization of the neutron beam is a highly sensitive probe at very small angles (&#60;50&#160;&#956;rad) but still allows a high intensity, divergent beam to be used. The decrease in polarization of the beam reflected from the sample as compared to that from the reference sample can be directly related to structure within the sample.
In comparison to scattering observed in neutron reflection measurements the SERGIS signals are often weak and are unlikely to be observed if the in-plane structures within the sample under investigation are dilute, disordered, small in size and polydisperse or the neutron scattering contrast is low. Therefore, good results will most likely be obtained using the SERGIS technique if the sample being measured consist of thin films on a flat substrate and contain scattering features that contains a high density of moderately sized features (30 nm to 5 &#181;m) which scatter neutrons strongly or the features are arranged on a lattice. An advantage of the SERGIS technique is that it can probe structures in the plane of the sample.

Progress has been made in utilizing spin echo resolved grazing incidence scattering (SERGIS) as a neutron scattering technique to probe the length-scales in irregular samples. Crystallites of [6,6]-phenyl-C61-butyric acid methyl ester have been probed using the SERGIS technique and the results confirmed by optical and atomic force microscopy.

The spin echo resolved grazing incidence scattering (SERGIS) technique has been used to probe the length-scales associated with irregularly shaped ...

How to Ignite an Atmospheric Pressure Microwave Plasma Torch without Any Additional Igniters

This movie shows how an atmospheric pressure plasma torch can be ignited by microwave power with no additional igniters. After ignition of the plasma, a stable and continuous operation of the plasma is possible and the plasma torch can be used for many different applications. On one hand, the hot (3,600 K gas temperature) plasma can be used for chemical processes and on the other hand the cold afterglow (temperatures down to almost RT) can be applied for surface processes. For example chemical syntheses are interesting volume processes. Here the microwave plasma torch can be used for the decomposition of waste gases which are harmful and contribute to the global warming but are needed as etching gases in growing industry sectors like the semiconductor branch. Another application is the dissociation of CO2. Surplus electrical energy from renewable energy sources can be used to dissociate CO2 to CO and O2. The CO can be further processed to gaseous or liquid higher hydrocarbons thereby providing chemical storage of the energy, synthetic fuels or platform chemicals for the chemical industry. Applications of the afterglow of the plasma torch are the treatment of surfaces to increase the adhesion of lacquer, glue or paint, and the sterilization or decontamination of different kind of surfaces. The movie will explain how to ignite the plasma solely by microwave power without any additional igniters, e.g., electric sparks. The microwave plasma torch is based on a combination of two resonators &#8212; a coaxial one which provides the ignition of the plasma and a cylindrical one which guarantees a continuous and stable operation of the plasma after ignition. The plasma can be operated in a long microwave transparent tube for volume processes or shaped by orifices for surface treatment purposes.

This movie shows how an atmospheric plasma torch can be ignited by microwaves with no additional igniters and provides a stable and continuous plasma operation suitable for plenty of applications.

This movie shows how an atmospheric pressure plasma torch can be ignited by microwave power with no additional igniters. After ignition of the plasma, a ...

Development of an Experimental Setup for the Measurement of the Coefficient of Restitution under Vacuum Conditions

The Discrete Element Method is used for the simulation of particulate systems to describe and analyze them, to predict and afterwards optimize their behavior for single stages of a process or even an entire process. For the simulation with occurring particle-particle and particle-wall contacts, the value of the coefficient of restitution is required. It can be determined experimentally. The coefficient of restitution depends on several parameters like the impact velocity. Especially for fine particles the impact velocity depends on the air pressure and under atmospheric pressure high impact velocities cannot be reached. For this, a new experimental setup for free-fall tests under vacuum conditions is developed. The coefficient of restitution is determined with the impact and rebound velocity which are detected by a high-speed camera. To not hinder the view, the vacuum chamber is made of glass. Also a new release mechanism to drop one single particle under vacuum conditions is constructed. Due to that, all properties of the particle can be characterized beforehand.

The coefficient of restitution is a parameter that describes the loss of kinetic energy during collision. Here, a free-fall setup under vacuum conditions is developed to be able to determine the coefficient of restitution parameter for particles in micrometer range with high impact velocities.

The Discrete Element Method is used for the simulation of particulate systems to describe and analyze them, to predict and afterwards optimize their ...

Using Synchrotron Radiation Microtomography to Investigate Multi-scale Three-dimensional Microelectronic Packages

Synchrotron radiation micro-tomography (SR&#181;T) is a non-destructive three-dimensional (3D) imaging technique that offers high flux for fast data acquisition times with high spatial resolution. In the electronics industry there is serious interest in performing failure analysis on 3D microelectronic packages, many which contain multiple levels of high-density interconnections. Often in tomography there is a trade-off between image resolution and the volume of a sample that can be imaged. This inverse relationship limits the usefulness of conventional computed tomography (CT) systems since a microelectronic package is often large in cross sectional area 100-3,600 mm2, but has important features on the micron scale. The micro-tomography beamline at the Advanced Light Source (ALS), in Berkeley, CA USA, has a setup which is adaptable and can be tailored to a sample&#39;s properties, i.e., density, thickness, etc., with a maximum allowable cross-section of 36 x 36 mm. This setup also has the option of being either monochromatic in the energy range ~7-43 keV or operating with maximum flux in white light mode using a polychromatic beam. Presented here are details of the experimental steps taken to image an entire 16 x 16 mm system within a package, in order to obtain 3D images of the system with a spatial resolution of 8.7 &#181;m all within a scan time of less than 3 min. Also shown are results from packages scanned in different orientations and a sectioned package for higher resolution imaging. In contrast a conventional CT system would take hours to record data with potentially poorer resolution. Indeed, the ratio of field-of-view to throughput time is much higher when using the synchrotron radiation tomography setup. The description below of the experimental setup can be implemented and adapted for use with many other multi-materials.

For this study synchrotron radiation micro-tomography, a non-destructive three-dimensional imaging technique, is employed to investigate an entire microelectronic package with a cross-sectional area of 16 x 16 mm. Due to the synchrotron&#39;s high flux and brightness the sample was imaged in just 3 min&#160;with an 8.7 &#181;m spatial resolution.

Synchrotron radiation micro-tomography (SR&#181;T) is a non-destructive three-dimensional (3D) imaging technique that offers high flux for fast data ...

Spark Plasma Sintering Apparatus Used for the Formation of Strontium Titanate Bicrystals

A spark plasma sintering apparatus was used as a novel method for diffusion bonding of two single crystals of strontium titanate to form bicrystals with one twist grain boundary. This apparatus utilizes high uniaxial pressure and a pulsed direct current for rapid consolidation of material. Diffusion bonding of strontium titanate bicrystals without fracture, in a spark plasma sintering apparatus, is possible at high pressures due to the unusual temperature dependent plasticity behavior of strontium titanate. We demonstrate a method for the successful formation of bicrystals at accelerated time scales and lower temperatures in a spark plasma sintering apparatus compared to bicrystals formed by conventional diffusion bonding parameters. Bond quality was verified by scanning electron microscopy. A clean and atomically abrupt interface containing no secondary phases was observed using transmission electron microscopy techniques. Local changes in bonding across the boundary was characterized by simultaneous scanning transmission electron microscopy and spatially resolved electron energy-loss spectroscopy.

A viable technique for the formation of strontium titanate bicrystals at high pressure and fast heating rate via the spark plasma sintering apparatus is developed.

A spark plasma sintering apparatus was used as a novel method for diffusion bonding of two single crystals of strontium titanate to form bicrystals with ...

New Application of an Atmospheric Pressure Plasma Jet as a Neuro-protective Agent Against Glucose Deprivation-induced Injury of SH-SY5Y Cells

The atmospheric pressure plasma jet (APPJ) has attracted the attention of many researchers from multiple disciplines in recent years because its emissions include multiple types of reactive nitrogen species (RNS) and reactive oxygen species (ROS). Our previous study has shown the cytoprotective effect of the APPJ against oxidative stress-induced injuries. The aim of the present study is to provide a detailed in vitro treatment protocol regarding the neuroprotective applications of helium APPJs on glucose deprivation-induced injury in SH-SY5Y cells. The SH-SY5Y human neuroblastoma-derived cell line was maintained in RPMI 1640 medium supplemented with 15% fetal calf serum. The culture medium was then changed to RPMI 1640 without glucose before APPJ treatment. After a 1 h incubation in a cell incubator, cell viability was determined using Cell Counting Kit 8. The results showed that, compared to the glucose deprivation group, cells treated with APPJ exhibited significantly increased cell viability in a dose-dependent manner, with 8 s/well observed as an optimal dose. Meanwhile, helium flow had no effect on the glucose deprivation-induced cell impairment. Our results indicated that APPJ could be potentially used as a treatment method for the diseases in the central nervous system related to glucose deprivation. This protocol could also be used as a cytoprotective application for other cells with different impairments, but the cell culture and APPJ treatment conditions should be readjusted, and the treatment dose must be relatively low.

A protocol for the neuroprotective application of low-dose atmospheric pressure plasma treatment on glucose deprivation-induced SH-SY5Y injuries.

The atmospheric pressure plasma jet (APPJ) has attracted the attention of many researchers from multiple disciplines in recent years because its emissions ...

Atmospheric Pressure Fabrication of Large-Sized Single-Layer Rectangular SnSe Flakes

Tin selenide (SnSe) belongs to the family of layered metal chalcogenide materials with a buckled structure like phosphorene, and has shown potential for applications in two-dimensional nanoelectronics devices. Although many methods to synthesize SnSe nanocrystals have been developed, a simple way to fabricate large-sized single-layer SnSe flakes remains a great challenge. Herein, we show the experimental method to directly grow large-sized single-layer rectangular SnSe flakes on commonly used SiO2/Si insulating substrates using a straightforward two-step fabrication method in an atmospheric pressure quartz tube furnace system. The single-layer rectangular SnSe flakes with an average thickness of ~6.8 &#197; and lateral dimensions of about 30 &#181;m &#215; 50 &#181;m were fabricated by a combination of vapor transport deposition technique and nitrogen etching route. We characterized the morphology, microstructure, and electrical properties of the rectangular SnSe flakes and obtained excellent crystallinity and good electronic properties. This article about the two-step fabrication method can help researchers grow other similar two-dimensional, large-sized, single-layer materials using an atmospheric pressure system.

A protocol is presented demonstrating a two-step fabrication technique to grow large-sized single-layer rectangular shaped SnSe flakes on low-cost SiO2/Si dielectrics wafers in an atmospheric pressure quartz tube furnace system.

Tin selenide (SnSe) belongs to the family of layered metal chalcogenide materials with a buckled structure like phosphorene, and has shown potential for ...

Nerve Stem Cell Differentiation by a One-step Cold Atmospheric Plasma Treatment In Vitro

As the development of physical plasma technology, cold atmospheric plasmas (CAPs) have been widely investigated in decontamination, cancer treatment, wound healing, root canal treatment, etc., forming a new research field named plasma medicine. Being a mixture of electrical, chemical, and biological reactive species, CAPs have shown their abilities to enhance nerve stem cells differentiation both in vitro and in vivo and are becoming a promising way for neurological disease treatment in the future. The much more exciting news is that using CAPs may realize one-step, and safely directed, differentiation of neural stem cells (NSCs) for tissue transportation. We demonstrate here the detailed experimental protocol of using a self-made CAP jet device to enhance NSC differentiation in C17.2-NSCs and primary rat neural stem cells, as well as observing the cell fate by inverted and fluorescence microscopy. With the help of immunofluorescence staining technology, we found both the NSCs showed an accelerated differential rate than the untreated group, and ~75% of the NSCs selectively differentiated into neurons, which are mainly mature, cholinergic, and motor neurons.

Nerve Stem Cell Differentiation by a One-step Cold Atmospheric Plasma Treatment In Vitro

This protocol aims to provide detailed experimental steps of a cold atmospheric plasma treatment on neural stem cells and immunofluorescence detection for differentiation enhancement.

As the development of physical plasma technology, cold atmospheric plasmas (CAPs) have been widely investigated in decontamination, cancer treatment, ...