Name: cooling rate dependent ellipsometry measurements to determine the dynamics of thin glassy films
Uploaded: 2016-01-26T18:00:00
Description: Watch this Scientific Journal Video about Cooling Rate Dependent Ellipsometry Measurements to Determine the Dynamics of Thin Glassy Films at JoVE.com

The Authors would like to acknowledge James A. Forrest for help in the initial idea for this technique.26&#160;This work was supported by funding from the University of Pennsylvania and was partially supported by the MRSEC program of the National Science Foundation under award no. DMR-11- 20901 at the University of Pennsylvania.

1. Film Preparation
<ol>
	<li>Weigh 0.04 g of polystyrene, and place into a 30 ml vial.</li>
	<li>Weigh 2 g of toluene into the vial. A 2% by weight solution of polystyrene in toluene yields a film of approximately 100 nm.</li>
	<li>Let the solution sit O/N to fully dissolve the polystyrene and let the solutions settle.</li>
	<li>Place a 1 cm x 1 cm Silicon (Si) wafer onto a Spin Coater.</li>
	<li>Spin the wafer at 8,000 rpm for 45 sec. While it is spinning, drop approximately 1 ml of toluene on the spinning wafer.<br ...

<ol>
	<li>Keddie, J. L., Jones, R. A. L., Cory, R. A. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Size-Dependent+depression+of+the+glass+transition+temperature+in+polymer+films.">Size-Dependent depression of the glass transition temperature in polymer films.</a> Europhys. Lett. 27 (1), 59-64 (1994).</li><li>Forrest, J. A., Veress, K. D., Dutcher, J. R. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Interface+and+chain+confinement+effects+on+the+glass+transition+temperature+of+thin+polymer+films.">Interface and chain confinement effects on the glass transition temperature of thin polymer films.</a> Phys. Rev.E. 56 (5), 5705-5716 (1997).</li><li>Forrest, J. A., Mattsson, J. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Reductions+of+the+glass+transition+temperature+in+thin+polymer+films:+Probing+the+length+scale+of+cooperative+dynamics.">Reductions of the glass transition temperature in thin polymer films: Probing the length scale of cooperative dynamics.</a> Phys. Rev.E. 61 (1), R53-R56 (2000).</li><li>Sharp, J. S., Forrest, J. A. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Free+surfaces+cause+reductions+in+the+glass+transition+temperature+of+thin+polystyrene+films.">Free surfaces cause reductions in the glass transition temperature of thin polystyrene films.</a> PRL. 91 (23), 235701 (2003).</li><li>Ellison, C. J., Torkelson, J. M. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=The+distribution+of+glass-transition+temperatures+in+nanoscopically+confined+glass+formers.">The distribution of glass-transition temperatures in nanoscopically confined glass formers.</a> Nat. Mat. 2 (10), 695-700 (2003).</li><li>Priestley, R. D., Ellison, C. J., Broadbelt, L. J., Torkelson, J. M. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Structural+relaxation+of+polymer+glasses+at+surfaces,+interfaces,+and+in+between.">Structural relaxation of polymer glasses at surfaces, interfaces, and in between.</a> Science. 309 (5733), 456-459 (2005).</li><li>Ellison, C. J., Kim, S. D., Hall, D. B., Torkelson, J. 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M., 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=T+g+depression+and+invariant+segmental+dynamics+in+polystyrene+thin+films.">T g depression and invariant segmental dynamics in polystyrene thin films.</a> Soft Matter. 8 (19), 5119-5122 (2012).</li><li>Yu, M., Olson, E. A., Zhang, M., Zhang, Z., Allen, L. H. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Glass+transition+in+ultrathin+polymer+films:+Calorimetric+study.">Glass transition in ultrathin polymer films: Calorimetric study.</a> PRL. 91 (8), 085703 (2003).</li><li>Kremer, F., Tress, M., Mapesa, E. U. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Glassy+dynamics+and+glass+transition+in+nanometric+layers+and+films:+A+silver+lining+on+the+horizon.">Glassy dynamics and glass transition in nanometric layers and films: A silver lining on the horizon.</a> J. Non-Crys. Solids. 407, 277-283 (2015).</li><li>Qi, D., Ilton, M., Forrest, J. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Measuring+surface+and+bulk+relaxation+in+glassy+polymers.">Measuring surface and bulk relaxation in glassy polymers.</a> Euro. Phys. J. E. 34 (6), 1-7 (2011).</li><li>Teichroeb, J. H., Forrest, J. A. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Direct+imaging+of+nanoparticle+embedding+to+probe+viscoelasticity+of+polymer+surfaces.">Direct imaging of nanoparticle embedding to probe viscoelasticity of polymer surfaces.</a> PRL. 91 (1), 016104 (2003).</li><li>Fakhraai, Z., Forrest, J. A. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Measuring+the+surface+dynamics+of+glassy+polymers.">Measuring the surface dynamics of glassy polymers.</a> Science. 319 (5863), 600-604 (2008).</li><li>Paeng, K., Swallen, S. F., Ediger, M. D. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Direct+measurement+of+molecular+motion+in+freestanding+polystyrene+thin+films.">Direct measurement of molecular motion in freestanding polystyrene thin films.</a> J. Am. Chem. Soc. 133 (22), 8444-8447 (2011).</li><li>Glor, E. C., Fakhraai, Z. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Facilitation+of+interfacial+dynamics+in+entagled+polymer+films.">Facilitation of interfacial dynamics in entagled polymer films.</a> JCP. 141 (9), 194505 (2014).</li><li>Fakhraai, Z., Forrest, J. A. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Probing+slow+dynamics+in+supported+thin+polymer+films.">Probing slow dynamics in supported thin polymer films.</a> PRL. 95 (2), 025701 (2005).</li><li>Roth, C. B., McNerny, K. L., Jager, W. F., Torkelson, J. M. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Eliminating+the+enhanced+mobility+at+the+free+surface+of+polystyrene:+fluorescence+studies+of+the+glass+transition+temperature+in+thin+bilayer+films+of+immiscible+polymers.">Eliminating the enhanced mobility at the free surface of polystyrene: fluorescence studies of the glass transition temperature in thin bilayer films of immiscible polymers.</a> Macromolecules. 40 (7), 2568-2574 (2007).</li><li>Priestley, R. D., Ellison, C. J., Broadbelt, L. J., Torkelson, J. 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Cooling-Rate dependent Tg measurements are high throughput characterization experiments that can determine the Tg, the expansion coefficient of the glass and the super-cooled liquid, the temperature dependence of the average dynamics, and the fragility of a particular glassy material in a single experiment. Furthermore, unlike fluorescence, embedding, or nanohole relaxation experiments, CR-Tg experiments are relatively quick and simple because they do not utilize fluorophores or other com...

The seminal work of Keddie Jones and Corey1 showed that the glass transition temperature (Tg) of ultra-thin polystyrene films decreases with respect to the bulk value at thicknesses lower than 60 nm. Ever since, many experimental studies2-11 have supported the hypothesis that the observed reductions in Tg are caused by a layer of enhanced mobility near the free surface of these films. However, these experiments are indirect measures of a single relaxation time, and thus there is a debate12-18 centered on a direct correlation between average thin film dynamics and the dynamics at the air/polymer interface.
To answer this debate, many studies have directly measured the dynamics of the free surface (&#964;surface). Nanoparticle embedding,19,20 nanohole relaxation,21 and fluorescence22 studies show that the air/polymer interface has dynamics orders of magnitude faster than the bulk alpha relaxation time (&#964;&#945;) with a much weaker temperature dependence than that of &#964;&#945;. Because of its weak temperature dependence, the &#964;surface of these films,19-22 and enhanced dynamics of thin polystyrene films,23,24 intersects the bulk alpha relaxation (&#964;&#945;) at a single point T*, which is a few degrees above Tg, and at a &#964;&#945; of &#8776; 1 sec. The presence of T* could explain why experiments which probe relaxation times faster than * fail to see any thickness dependence on the Tg of ultra-thin Polystyrene films.13-18 Lastly, while direct measurements of the enhanced mobile layer show that it has a thickness of 4-8 nm,20-22 there is evidence that the propagation length of the dynamics at the air/polymer interface is much larger than the thickness of the mobile surface layer.5,25,26
This report aims to fully describe a protocol for using ellipsometry for cooling rate dependent Tg (CR-Tg) experiments. CR-Tg have been previously used to describe the average dynamics of ultra-thin films of polystyrene.23,24,27,28 Furthermore, This technique was recently used to show a direct correlation between the average dynamics in ultra-thin polystyrene films, and the dynamics at the free surface.23 The advantage of CR-Tg measurements over other types of measurements such as fluorescence, nanoparticle embedding, nanohole relaxation, nanocalorimetry, dielectric spectroscopy, and Brillouin light scattering, studies is that they are relatively quick and simple experiments that do not utilize fluorophores or other complicated experimental techniques. Recent advances in spectroscopic ellipsometry allow this technique to be used to efficiently determine the optical properties of ultra-thin films of polymers and other types of hybrid materials with exceptional accuracy. As such, this technique probes the average dynamics of technologically applicable thin films in temperature and time regimes relevant to the glass transition (T &#8804; Tg, &#964;&#945; &#8805; 100 sec). Furthermore, this technique will provide information on the expansion coefficients of the glassy and supper cooled liquid states as well as the fragility of the system, which can then be compared with data for bulk films. Lastly, CR- Tg experiments can be used for any glassy system so long as the integrity of the film remains throughout the experiment.

<table border="0" cellpadding="0" cellspacing="0" width="918">
	<tbody>
		<tr height="21">
			<td height="21" style="height:21px;width:216px;">Toluene</td>
			<td style="width:111px;">Sigma Aldrich</td>
			<td style="width:119px;">179418-1L</td>
			<td style="width:472px;">This can be purchased from any chemical company.</td>
		</tr>
		<tr height="42">
			<td height="42" style="height:42px;width:216px;">Atactic Polystyrene</td>
			<td style="width:111px;">Polymer Source Inc.</td>
			<td style="width:119px;">P-4092-S</td>
			<td>This can be purchased from any chemical company.</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:216px;">THMS 600 temperature stage</td>
			<td style="width:111px;">Linkam</td>
			<td style="width:119px;">THMS 600</td>
			<td>any temperature stage that can be fit to an ellipsometer could be used.</td>
		</tr>
		<tr height="42">
			<td height="42" style="height:42px;width:216px;">M2000V Spectroscopic Ellipsometer</td>
			<td style="width:111px;">J.A. Woollam</td>
			<td style="width:119px;">M200V</td>
			<td>This procedure should be applicable for any spectroscopic ellipsometer.</td>
		</tr>
		<tr height="42">
			<td height="42" style="height:42px;width:216px;">Spin Coater</td>
			<td style="width:111px;">Laurell Technologies</td>
			<td style="width:119px;">WS-650-23B</td>
			<td>This Procedure is possible with any spin coater</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:216px;">Sample vials</td>
			<td style="width:111px;">Fisher Scientific</td>
			<td style="width:119px;">02-912-379</td>
			<td>Any sample vials will do</td>
		</tr>
		<tr height="42">
			<td height="42" style="height:42px;width:216px;">Silicon wafers</td>
			<td style="width:111px;">Virginia semi conductors</td>
			<td style="width:119px;">325S1410694D</td>
			<td></td>
		</tr>
	</tbody>
</table>

cooling rate dependent ellipsometry measurements to determine the dynamics of thin glassy films

This report aims to fully describe the experimental technique of using ellipsometry for cooling rate dependent Tg (CR-Tg) experiments. These measurements are simple high-throughput characterization experiments, which can determine the glass transition temperature (Tg), average dynamics, fragility and the expansion coefficient of the super-cooled liquid and glassy states for a variety of glassy materials. This technique allows for these parameters to be measured in a single experiment, while other methods must combine a variety of different techniques to investigate all of these properties. Measurements of dynamics close to Tg are particularly challenging. The advantage of cooling rate dependent Tg measurements over other methods which directly probe bulk and surface relaxation dynamics is that they are relatively quick and simple experiments, which do not utilize fluorophores or other complicated experimental techniques. Furthermore, this technique probes the average dynamics of technologically relevant thin films in temperature and relaxation time (&#964;&#945;) regimes relevant to the glass transition (&#964;&#945; &#62; 100 sec). The limitation to using ellipsometry for cooling rate dependent Tg experiments is that it cannot probe relaxation times relevant to measurements of viscosity (&#964;&#945; &#60;&#60; 1 sec). Other cooling rate dependent Tg measurement techniques, however, can extend the CR-Tg method to faster relaxation times. Furthermore, this technique can be used for any glassy system so long as the integrity of the film remains throughout the experiment.

Fitting Raw Ellipsometry Data
Polystyrene films are transparent in the wavelength range of the ellipsometer (500-1,600 nm). Thus a Cauchy model is a good model for describing the index of refraction of polystyrene films. Figure 1A shows an example of &#936;(&#955;) and &#916;(&#955;) for a thick (274 nm) film of polystyrene, and the resulting fit to the Cauchy model <img alt="Equation 1" src="/f...

Watch this Scientific Journal Video about Cooling Rate Dependent Ellipsometry Measurements to Determine the Dynamics of Thin Glassy Films at JoVE.com

Cooling Rate Dependent Ellipsometry Measurements to Determine the Dynamics of Thin Glassy Films

Here, we present a protocol for cooling rate dependent ellipsometry experiments, which can determine the glass transition temperature (Tg), average dynamics, fragility and the expansion coefficient of the super-cooled liquid and glass for a variety of glassy materials.

This report aims to fully describe the experimental technique of using ellipsometry for cooling rate dependent Tg (CR-Tg) experiments. These measurements ...

The overall goal of this procedure is to provide a simple method to quickly and accurately measure the glass transition temperature, apparent expansion coefficient, and average dynamics of ultra-thin glassy films. This method can help answer key questions in a polymer glass field, such as how the dynamics of thin-films relate to those of the bulk. The main advantage of this technique is that it can calculate the glass transition temperature, apparent activation coefficients, and fragilities of polymer ultra-thin films in a single high-throughput experiment.While the example provided here is mostly focused on polymer glasses, this method can be applied more broadly to study the properties of thick and thin films of other types of glasses, such as organic molecule glasses and nanocomposites. Start preparing the film a day before it is needed for glass transition temperature measurements. Have a scale ready to accurately weigh materials for the film.This experiment will use polystyrene and toluene to create the film. Begin by measuring 40 milligrams of polystyrene. Add two grams of toluene to produce an approximately 100 nanometer film.After the solution has sat overnight, use it to create a film. Move the vial to a spin coater that is in a fume hood. At the fume hood, put the solution aside for later use.Also, ensure that there is toluene ready for use with the spin coater. Next, get a silicon wafer to create the film on by spin coating. The silicon wafer for this protocol is one centimeter by one centimeter.Place the wafer in the spin coater, and spin it at 8, 000 rpm for 45 seconds. As the wafer spins, drop approximately one milliliter of toluene onto it. Stop the spin coater after 45 seconds of spinning.Use the prepared polystyrene and toluene solution, and begin to add it drop-wise to the silicon surface. Stop when the entire surface is covered. Before the solution dries, spin the wafer at 4, 000 rpm for 20 seconds.Stop the spin coater, and remove the wafer to measure the film thickness. Determine the film thickness using an ellipsometer. Begin by placing the film on the ellipsometer stage and securing it.Continue by checking the angle of incidence, acquisition time, and other settings. Then begin the scan. After collecting data, use the ellipsometer software to fit the ellipsometric angles.Use a three-layer model. The first layer is the substrate, in this case, silicon. The second layer, layer number one, is a native oxide.The layer has a thickness of 1.5 nanometers. The third layer, layer number two, is a Cauchy Model, corresponding to the optical properties of polystyrene film. The Cauchy Model for the index of refraction is given by this formula.Lambda is the wavelength, and A and B are constants to be determined from data. K equals zero for a transparent material. The model returns a determination of the film thickness, in this case, about 105 nanometers.Remove the wafer from the ellipsometer and proceed to the next step. If the film is of the desired thickness, take the wafer to a vacuum oven. Place the wafer in the oven and anneal it for 15 hours at 393 Kelvin.Return to the ellipsometer with the annealed film. Put the film aside while preparing the sample stage. The ellipsometer should be equipped with a variable temperature stage.Use a thermal paste to coat the surface of its heating element. Next, place the annealed polystyrene film onto the heating element. Then clamp it tightly into place.Start a flow of 100%dry nitrogen through the temperature stage. Turn to the computer and the temperature stage software to create a temperature profile. This figure provides an idea of the temperature profile.Temperature is along the vertical axis. Time is along the horizontal axis. The sample is alternately heated to 393 Kelvin and cooled to 293 Kelvin.The temperature ramp-up grade is always a constant 150 Kelvin per minute, as indicated by the constant steep upward slope. The ramp-down varies with each cycle. It starts fast, then slows down, as indicated by the changing downward slopes in the figure.The sample is held for 20 minutes after it first reaches 393 Kelvin. All later temperature holding times, at both 393 Kelvin and 293 Kelvin, are for five minutes. Stay at the computer to complete setting up the experiment.Use the ellipsometer software to create a temperature-dependent ellipsometry model. The substrate layer is a temperature-dependent silicon model. Layer number one is a 1.5 nanometer native oxide layer.Layer number two, the third layer, is the Cauchy Model for polystyrene film. Work with the temperature-dependent silicon layer settings. Turn on the Use Ext Temp from Parm Log"to allow use of the temperature stage temperature.Now navigate to be able to edit the hardware configurations. Set the fast acquisition time to one second. Also, select high-accuracy zone averaging.Set the normal acquisition time to three seconds. Once again, use the high-accuracy zone averaging. Click the In Situ"tab of the ellipsometer software.Check the Fast Acquisition Time Mode"box. Press Start Acquisition"to begin collecting data. Monitor the data collection as the temperature profile is followed.Just before the three Kelvin per minute cooling ramp, uncheck the Fast Acquisition"time box. Use measurements of the thickness versus temperature for a given cooling ramp to calculate the glass transition temperature. In this sample curve, the region highlighted in red corresponds to the supercooled liquid.The region highlighted in blue corresponds to the glassy regime. The point where linear fits to these regions intersect defines the glass transition temperature. This sample is 110 nanometer polystyrene film of 342 kilogram per mole polystyrene.The cooling rate is 10 Kelvin per minute. Measurements at one Kelvin per minute give a temperature of about 372 Kelvin. Here is data of the glass transition temperature versus the cooling rate for a 110 nanometer film of polystyrene.This same data is plotted with black circles using the log of the cooling rate on the left vertical axis. The horizontal axis is 1000 over the transition temperature, as suggested by an empirical relation. For comparison, the red squares are the bulk dynamics of polystyrene, as determined by dielectric spectroscopy.For this data, refer to the right axis of the log of the bulk alpha relaxation time and the horizontal axis, 1000 over temperature. Once mastered, this technique will take five hours if performed properly. While attempting this procedure, it's important to remember to use an appropriate material model, so that you accurately fit the ellipsometry values for the thickness and the index of refraction of the film.I first tried this method of studying polymer thin-films in James Forrest's lab in the University of Waterloo. However, with recent advances in ellipsometry technology, we are now able to use this as a high-throughput method to study broad systems, such as organic thin-films and newly-synthesized molecules. After this video, you should have a good understanding of how to make a polymer thin-film and calculate the glass transition temperature, expansion coefficient, and apparent activation barrier to the relaxation time near the glass transition.

cooling-rate-dependent-ellipsometry-measurements-to-determine

Research

JoVE Journal

Chemistry

A Technique to Functionalize and Self-assemble Macroscopic Nanoparticle-ligand Monolayer Films onto Template-free Substrates

This protocol describes a self-assembly technique to create macroscopic monolayer films composed of ligand-coated nanoparticles1,2. The simple, robust and scalable technique efficiently functionalizes metallic nanoparticles with thiol-ligands in a miscible water/organic solvent mixture allowing for rapid grafting of thiol groups onto the gold nanoparticle surface. The hydrophobic ligands on the nanoparticles then quickly phase separate the nanoparticles from the aqueous based suspension and confine them to the air-fluid interface. This drives the ligand-capped nanoparticles to form monolayer domains at the air-fluid interface.&#160; The use of water-miscible organic solvents is important as it enables the transport of the nanoparticles from the interface onto template-free substrates.&#160; The flow is mediated by a surface tension gradient3,4 and creates macroscopic, high-density, monolayer nanoparticle-ligand films.&#160; This self-assembly technique may be generalized to include the use of particles of different compositions, size, and shape and may lead to an efficient assembly method to produce low-cost, macroscopic, high-density, monolayer nanoparticle films for wide-spread applications.

A simple, robust and scalable technique to functionalize and self-assemble macroscopic nanoparticle-ligand monolayer films onto template-free substrates is described in this protocol.

This protocol describes a self-assembly technique to create macroscopic monolayer films composed of ligand-coated nanoparticles1,2. The simple, robust and ...

Atomically Defined Templates for Epitaxial Growth of Complex Oxide Thin Films

Atomically defined substrate surfaces are prerequisite for the epitaxial growth of complex oxide thin films. In this protocol, two approaches to obtain such surfaces are described. The first approach is the preparation of single terminated perovskite SrTiO3 (001) and DyScO3 (110) substrates. Wet etching was used to selectively remove one of the two possible surface terminations, while an annealing step was used to increase the smoothness of the surface. The resulting single terminated surfaces allow for the heteroepitaxial growth of perovskite oxide thin films with high crystalline quality and well-defined interfaces between substrate and film. In the second approach, seed layers for epitaxial film growth on arbitrary substrates were created by Langmuir-Blodgett (LB) deposition of nanosheets. As model system Ca2Nb3O10- nanosheets were used, prepared by delamination of their layered parent compound HCa2Nb3O10. A key advantage of creating seed layers with nanosheets is that relatively expensive and size-limited single crystalline substrates can be replaced by virtually any substrate material.

Various procedures are outlined to prepare atomically defined templates for epitaxial growth of complex oxide thin films. Chemical treatments of single crystalline SrTiO3 (001) and DyScO3 (110) substrates were performed to obtain atomically smooth, single terminated surfaces. Ca2 Nb3 O10- nanosheets were used to create atomically defined templates on arbitrary substrates.

Atomically defined substrate surfaces are prerequisite for the epitaxial growth of complex oxide thin films. In this protocol, two approaches to obtain ...

High Precision Zinc Isotopic Measurements Applied to Mouse Organs

We present a procedure to measure with high precision zinc isotope ratios in mouse organs. Zinc is composed of 5 stable isotopes (64Zn, 66Zn, 67Zn, 68Zn and 70Zn) which are naturally fractionated between mouse organs. We first show how to dissolve the different organs in order to free the Zn atoms; this step is realized by a mixture of HNO3 and H2O2. We then purify the zinc atoms from all the other elements, in particular from isobaric interferences (e.g., Ni), by anion-exchange chromatography in a dilute HBr/HNO3 medium. These first two steps are performed in a clean laboratory using high purity chemicals. Finally, the isotope ratios are measured by using a multi-collector inductively-coupled-plasma mass-spectrometer, in low resolution. The samples are injected using a spray chamber and the isotopic fractionation induced by the mass-spectrometer is corrected by comparing the ratio of the samples to the ratio of a standard (standard bracketing technique).&#160;This full typical&#160;procedure produces an isotope ratio with a 50 ppm (2 s.d.) reproducibility.

We present the technique to measure with high precision zinc isotope ratios in mouse organs.

We present a procedure to measure with high precision zinc isotope ratios in mouse organs. Zinc is composed of 5 stable isotopes (64Zn, 66Zn, 67Zn, 68Zn ...

Fabrication of Large-area Free-standing Ultrathin Polymer Films

This procedure describes a method for the fabrication of large-area and ultrathin free-standing polymer films. Typically, ultrathin films are prepared using either sacrificial layers, which may damage the film or affect its mechanical properties, or they are made on freshly cleaved mica, a substrate that is difficult to scale. Further, the size of ultrathin film is typically limited to a few square millimeters. In this method, we modify a surface with a polyelectrolyte that alters the strength of adhesion between polymer and deposition substrate. The polyelectrolyte can be shown to remain on the wafer using spectroscopy, and a treated wafer can be used to produce multiple films, indicating that at best minimal amounts of the polyelectrolyte are added to the film. The process has thus far been shown to be limited in scalability only by the size of the coating equipment, and is expected to be readily scalable to industrial processes. In this study, the protocol for making the solutions, preparing the deposition surface, and producing the films is described.

We describe a method for the fabrication of large-area (up to 13 cm diameter) and ultrathin (as thin as 8 nm) polymer films. Instead of using a sacrificial interlayer to delaminate the film from its substrate, we use a self-limiting surface treatment suitable for arbitrarily large areas.

This procedure describes a method for the fabrication of large-area and ultrathin free-standing polymer films.  Typically, ultrathin films are prepared ...

Unraveling Entropic Rate Acceleration Induced by Solvent Dynamics in Membrane Enzymes

Enzyme catalysis evolved in an aqueous environment. The influence of solvent dynamics on catalysis is, however, currently poorly understood and usually neglected. The study of water dynamics in enzymes and the associated thermodynamical consequences is highly complex and has involved computer simulations, nuclear magnetic resonance (NMR) experiments, and calorimetry. Water tunnels that connect the active site with the surrounding solvent are key to solvent displacement and dynamics. The protocol herein allows for the engineering of these motifs for water transport, which affects specificity, activity and thermodynamics. By providing a biophysical framework founded on theory and experiments, the method presented herein can be used by researchers without previous expertise in computer modeling or biophysical chemistry. The method will advance our understanding of enzyme catalysis on the molecular level by measuring the enthalpic and entropic changes associated with catalysis by enzyme variants with obstructed water tunnels. The protocol can be used for the study of membrane-bound enzymes and other complex systems. This will enhance our understanding of the importance of solvent reorganization in catalysis as well as provide new catalytic strategies in protein design and engineering.

Channels for the transportation of water molecules in enzymes influence active site solvation and catalysis. Herein we present a protocol for the engineering of these additional catalytic motifs based on in silico computer modeling and experiments. This will enhance our understanding of the influence of solvent dynamics on enzyme catalysis.

Enzyme catalysis evolved in an aqueous environment. The influence of solvent dynamics on catalysis is, however, currently poorly understood and usually ...

Dissolution Dynamic Nuclear Polarization Instrumentation for Real-time Enzymatic Reaction Rate Measurements by NMR

The main limitation of NMR-based investigations is low sensitivity. This prompts for long acquisition times, thus preventing real-time NMR measurements of metabolic transformations. Hyperpolarization via dissolution DNP circumvents part of the sensitivity issues thanks to the large out-of-equilibrium nuclear magnetization stemming from the electron-to-nucleus spin polarization transfer. The high NMR signal obtained can be used to monitor chemical reactions in real time. The downside of hyperpolarized NMR resides in the limited time window available for signal acquisition, which is usually on the order of the nuclear spin longitudinal relaxation time constant, T1, or, in favorable cases, on the order of the relaxation time constant associated with the singlet-state of coupled nuclei, TLLS. Cellular uptake of endogenous molecules and metabolic rates can provide essential information on tumor development and drug response. Numerous previous hyperpolarized NMR studies have demonstrated the relevancy of pyruvate as a metabolic substrate for monitoring enzymatic activity in vivo. This work provides a detailed description of the experimental setup and methods required for the study of enzymatic reactions, in particular the pyruvate-to-lactate conversion rate in presence of lactate dehydrogenase (LDH), by hyperpolarized NMR.

The sensitivity enhancement provided by dissolution dynamic nuclear polarization (DNP) enables following metabolic processes in real time by NMR and MRI. The characteristics and performances of a dedicated dissolution DNP setup designed for study enzymatic reactions are discussed.

The main limitation of NMR-based investigations is low sensitivity. This prompts for long acquisition times, thus preventing real-time NMR measurements of ...

Capillary Electrophoresis to Monitor Peptide Grafting onto Chitosan Films in Real Time

Free-solution capillary electrophoresis (CE) separates analytes, generally charged compounds in solution through the application of an electric field. Compared to other analytical separation techniques, such as chromatography, CE is cheap, robust and effectively requires no sample preparation (for a number of complex natural matrices or polymeric samples). CE is fast and can be used to follow the evolution of mixtures in real time (e.g., chemical reaction kinetics), as the signals observed for the separated compounds are directly proportional to their quantity in solution.
Here, the efficiency of CE is demonstrated for monitoring the covalent grafting of peptides onto chitosan films for subsequent biomedical applications. Chitosan&#39;s antimicrobial and biocompatible properties make it an attractive material for biomedical applications such as cell growth substrates. Covalently grafting the peptide RGDS (arginine - glycine - aspartic acid - serine) onto the surface of chitosan films aims at improving cell attachment. Historically, chromatography and amino acid analysis have been used to provide a direct measurement of the amount of grafted peptide. However, the fast separation and absence of sample preparation provided by CE enables equally accurate yet real-time monitoring of the peptide grafting process. CE is able to separate and quantify the different components of the reaction mixture: the (non-grafted) peptide and the chemical coupling agents. In this way the use of CE results in improved films for downstream applications.
The chitosan films were characterized through solid-state NMR (nuclear magnetic resonance) spectroscopy. This technique is more time-consuming and cannot be applied in real time, but yields a direct measurement of the peptide and thus validates the CE technique.

Free solution capillary electrophoresis is a fast, cheap and robust analytical method that enables the quantitative monitoring of chemical reactions in real time. Its utility for rapid, convenient and precise analysis is demonstrated here through analysis of covalent peptide grafting onto chitosan films for improved cell adhesion.

Free-solution capillary electrophoresis (CE) separates analytes, generally charged compounds in solution through the application of an electric field. ...

Electrochemical Impedance Spectroscopy as a Tool for Electrochemical Rate Constant Estimation

Electrochemical impedance spectroscopy (EIS) was used for advanced characterization of organic electroactive compounds along with cyclic voltammetry (CV). In the case of fast reversible electrochemical processes, current is predominantly affected by the rate of diffusion, which is the slowest and limiting stage. EIS is a powerful technique that allows separate analysis of stages of charge transfer that have different AC frequency response. The capability of the method was used to extract the value of charge transfer resistance, which characterizes the rate of charge exchange on the electrode-solution interface. The application of this technique is broad, from biochemistry up to organic electronics. In this work, we are presenting the method of analysis of organic compounds for optoelectronic applications.

Electrochemical impedance spectroscopy (EIS) of species that undergo reversible oxidation or reduction in solution was used for determination of rate constants of oxidation or reduction.

Electrochemical impedance spectroscopy (EIS) was used for advanced characterization of organic electroactive compounds along with cyclic voltammetry (CV). ...

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.

We demonstrate a method of conformally coating conjugated polymers on arbitrary substrates using a custom-designed, low-pressure reaction chamber. ...

Solution-Processed "Silver-Bismuth-Iodine" Ternary Thin Films for Lead-Free Photovoltaic Absorbers

Bismuth-based hybrid perovskites are regarded as promising photo-active semiconductors for environment-friendly and air-stable solar cell applications. However, poor surface morphologies and relatively high bandgap energies have limited their potential. Silver-bismuth-iodine (Ag-Bi-I) is a promising semiconductor for optoelectronic devices. Therefore, we demonstrate the fabrication of Ag-Bi-I ternary thin films using material solution processing. The resulting thin films exhibit controlled surface morphologies and optical bandgaps according to their thermal annealing temperatures. In addition, it has been reported that Ag-Bi-I ternary systems crystallize to AgBi2I7, Ag2BiI5, etc. according to the ratio of the precursor chemicals. The solution-processed AgBi2I7 thin films exhibit a cubic-phase crystal structure, dense, pinhole-free surface morphologies with grains ranging in size from 200 to 800 nm, and an indirect bandgap of 1.87 eV. The resultant AgBi2I7 thin films show good air stability and energy band diagrams, as well as surface morphologies and optical bandgaps suitable for lead-free and air-stable single-junction solar cells. Very recently, a solar cell with 4.3% power conversion efficiency was obtained by optimizing the Ag-Bi-I crystal compositions and solar cell device architectures.

Solution-Processed &quot;Silver-Bismuth-Iodine&quot; Ternary Thin Films for Lead-Free Photovoltaic Absorbers

Herein, we present detailed protocols for solution-processed silver-bismuth-iodine (Ag-Bi-I) ternary semiconductor thin films fabricated on TiO2-coated transparent electrodes and their potential application as air-stable and lead-free optoelectronic devices.

Bismuth-based hybrid perovskites are regarded as promising photo-active semiconductors for environment-friendly and air-stable solar cell applications. ...