This material is based upon work supported by the Department of&#160;Energy, National Nuclear Security Administration,&#160;under Award Number DE-NA0002377. Funding from the Defense Threat Reduction Agency (DTRA), Grant Number HDTRA1-10-1-0119. Counter-WMD basic research program, Dr. Suhithi M. Peiris, program director is gratefully acknowledged. This work was also supported by the Ministry of Education and Science and Education of the Russian Federation in the framework of Increase Competitiveness Program of NUST &#8220;MISIS&#8221; grant No. K2-2014-001.

1. High-energy Ball Milling
<ol>
	<li>Prepare 35 g of the initial 1:1 molar ratio Ni+Al mixture. In this case, weigh 11.02 g of Al and 23.98 g of Ni powders.</li>
	<li>Use a steel milling jar for HEBM of this system. Ensure that the jar has a higher hardness than the powders to be added, otherwise the powders will damage the jar and contamination will arise. Note: Typical jar choices include steel, zirconium oxide, or tungsten carbide.</li>
	<li>Use a 5:1 ball:powder (charge ratio) for this system, i.e., 175 g of 10 mm steel balls. Ensure that the balls are made of the same material as the jar otherwise either the balls or the jar will be damaged. 
	Note: The charge ratio defines the intensity of interaction between powder and the milling agents.</li>
	<li>Add balls and powders to the jar.</li>
	<li>Seal the jar and pump the atmospheric gas from the jar by mechanical pump and purge by argon. Conduct four cycles of filling and purging with Ar gas (this ensures that there is no oxygen remaining in the jar). Finally, fill the jar with argon gas slightly above (0.13 MPa) atmospheric pressure.</li>
	<li>Insert the jar into a planetary ball mill.</li>
	<li>Choose 650 revolution per minute (rpm) for the rate of revolution of jar and 1,400 rpm for the internal rotation (sun wheel). 
	Note: In some cases, the rotation ratio (k) of sum wheel (1,400 rpm) and milling jar (from 700 to 1,300 rpm) was varied to regulate the microstructure of composite particles.</li>
	<li>Run the HEBM procedure for 15 min. Note: Systems have a critical time, which, for the described conditions, equals 17 min. There is a finite amount of milling that can be conducted on the system before the reaction occurs in the jar. If HEBM is conducted longer than the critical time, a reaction will occur in the ball-milling jar, ruining the experiment.</li>
	<li>Following completion of milling time, cool the jar to RT, and then move the jar to a fume hood.
	<ol>
		<li>Vent the jar to remove excess gas pressure from initial pressurization and possible gas released during milling.</li>
		<li>Remove the lid from the jar under the fume hood. Take caution when opening the jar, as the powder formed is very reactive. Open the jar wearing heat resistant gloves and safety goggles.</li>
		<li>Before collecting powder, expose it to air for at least 5 min for &#8220;passivation&#8221;. 
		Note: This prevents spontaneous reaction that may occur while handling the mixture.</li>
	</ol>
	</li>
</ol>
2. Reactivity Characterization of Energetic Materials
<ol>
	<li>Collect the powder from the jar. Do not use a metallic spatula for this procedure.
	<ol>
		<li>If classification and separation of the particles is desired, utilize sieves. To ensure that proper separation is done, use a sieve shaker for an extended period of time (12+ hr). Classify the powder into various size bins (under 10 &#181;m, 10-20 &#181;m, 20-53 &#181;m, above 53 &#181;m). From this point onwards, use 20-53 &#181;m sized particles.</li>
	</ol>
	</li>
	<li>Press the sieved powders into a pellet using a uniaxial press set to 1,100 kg on a 5 mm stainless steel press die (1,360 MPa) for a dwell time of 2.0 min. Record the height (h) and the diameter (d) of the pellet with a micrometer. Record the weight of the sample (m) with a scale. From here, determine the density of the pellet. Calculate the theoretical max density percent (TMD%) by the following formula: 
	<img alt="Equation 1" src="/files/ftp_upload/52624/52624eq1.jpg" width="400" /> 
	where AAl, ANi &#8212; atom weight of Al and Ni; &#961;Al and &#961;Ni &#8212; density of Al and Ni. Assume that the stoichiometric ratio of the powders retains the ratio of the initial powders added.
	<ol>
		<li>If the cylindrical pellet is being used to determine a combustion front propagation velocity and temperature profile in the reaction front, ensure that it is tall enough, determined by the ratio between height and diameter which should be &#8805;2 (e.g., d = 5 mm; h &#8805; 10 mm).</li>
		<li>If the pellet is being used to define ignition parameters, use a thin disk (e.g., diameter = 5 mm, thickness = 1 mm).</li>
	</ol>
	</li>
	<li>To define combustion characteristics, place the sample onto a graphite plate.</li>
	<li>Make a coiled tungsten wire attached to a variable transformer.</li>
	<li>Position the W coil such that the coiled portion of the wire rests on the top of the pellet. If the reactive system is oxygen sensitive, do this in an oxygen-free reaction chamber, otherwise perform the reaction in open air.</li>
	<li>In order to determine the combustion wave velocity, use the recording from the high-speed camera. Position and focus the high-speed thermal camera on the tested sample and start recording. This will enable accurate temperature and combustion velocity information to be gathered.</li>
	<li>Slowly turn the variable transformer on, causing the tungsten wire to heat up. The reaction will initiate, and then propagate.</li>
	<li>To obtain the desired parameters of the combustion process, conduct frame by frame analysis of the recorded IR movie.
	<ol>
		<li>Plot the position of the reaction front propagation vs. time. Obtain the average combustion velocity from the slope of the plot.</li>
		<li>Plot the temperature changes in a spot in the middle of the sample. Use the obtained graph to gain information about the temperature time profile of the reaction wave.</li>
	</ol>
	</li>
	<li>To define ignition characteristics (ignition temperature and ignition delay time) put the thin disk on a hot plate preheated to the desired temperature (e.g., 800 K). Note that the exact values obtained from this experiment will vary significantly if any parameters are changed, whether they are size of the pellet, temperature of the hotplate, or TMD. This analysis is useful for determination of trends.
	<ol>
		<li>In order to determine the ignition parameters use the high-speed camera. Position and focus the high-speed thermal camera on the area where the sample will be placed on the hot plate and start recording. 
		Note: This will enable accurate temperature information during the process.
		<ol>
			<li>If the reaction is oxygen sensitive, perform this in an oxygen free reaction chamber. IMPORTANT: Run this experiment multiple times to gain a good statistical dataset.</li>
		</ol>
		</li>
		<li>Put the pellet into the zone of focus. Do this in a way that the particle could be seen on every frame &#8212; it is important to see the first frame that the pellet touches the hot plate.</li>
		<li>To obtain the desired ignition parameters, conduct frame by frame analysis of the recorded IR movie.</li>
		<li>To determine the ignition delay time, determine the time between the first frame, when the pellet touches the surface of the hotplate, to the reaction initiation.</li>
		<li>To determine the ignition temperature, plot the highest temperature spot on the particle. When the time-temperature profile switches from that of a preheating temperature profile to that of a thermal explosive regime, the point of inflection matches the ignition temperature.</li>
	</ol>
	</li>
</ol>
3. Microstructure Analysis Using Field Emission Scanning Electron Microscope (FESEM) Equipped by Focus Ion Beam (FIB)
<ol>
	<li>Suspend 0.1 g of the fabricated particles in 10 ml ethanol and deposit one drop of the suspension onto a surface of scanning electron microscopy (SEM) sample holder.</li>
	<li>Dry the sample holder at 90 &#176;C for 5 min.</li>
	<li>Insert the sample into a dual beam FIB/SEM system.</li>
	<li>Conduct sample plasma cleaning for 5 min. Note: This reduces the amount of damage that the sample will experience from exposure to the electron beam (E-beam).</li>
	<li>Turn on the E-beam (5 kV, 3.5 nA) and focus on a single particle. Link the z-height to the working distance, then raise the sample to eucentric height.</li>
	<li>Using the E-beam with the gas injection needle, deposit an initial layer of platinum (70 nm) onto the sample to protect from degradation from use of the gallium ion-beam (I-beam).</li>
	<li>Tilt the sample to 52&#176;, and then turn on the I-beam. Using the I-beam (5 kV, 0.28 nA), again with the gas injection needle, deposit an additional layer of platinum (0.5 &#181;m) onto the sample for protection.</li>
	<li>Cut fiduciary marks on the sample. Mill the particle into a rectangular shape. This vastly increases the chance that there will be an adequate fiduciary, since there will be multiple cuts and corners to use.</li>
	<li>With the aid of a program, slice the particle with the I-beam.
	<ol>
		<li>Select &#8220;File&#8221; then &#8220;Image Save Location&#8221; to choose a directory where the images will be stored.</li>
		<li>Depending on the individual particle, select the appropriate width, length, and depth; choose these to completely mill through the entire volume of the particle. Additionally, select the number of slices, as well as the number of slices per image. These options can be found in the &#8220;Slice&#8221; tab.</li>
		<li>Set the beam current by selecting &#8220;Utilities&#8221; then &#8220;Suggest Currents&#8221;. Note: This will allow the program to select the appropriate beam current to mill the sample in a reasonable time while guarding against sample damage.</li>
		<li>Click &#8220;Show&#8221; and the software will provide a visual milling grid that shows what portion of the particle will be milled; ensure that the milling grid is placed accurately over the particle in the portion that is to be milled.</li>
		<li>After each slice take a high-quality e-beam image for later reconstruction. To select the appropriate e-beam parameters, select the &#8220;Setup&#8221; menu and choose &#8220;EBeam Image Scan Parameters&#8221;. 
		Note: This will give a grid to select resolution and dwell time. The higher the dwell time, the more time it takes to collect the image.</li>
	</ol>
	</li>
	<li>Utilizing a 3D reconstruction software package, reconstruct the set of images collected from the FIB/SEM as described previously25. Note: This yields a complete 3D virtual copy of the particle, which can then be used to calculate surface area contact, porosity of the individual particles, diffusive layer thickness, as well as countless other useful parameters.</li>
</ol>

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The authors have nothing to disclose.

The protocol provides a detailed description for preparation of reactive energetic (Ti+C, Ta+C, Ni+Al) nanocomposites with tailored microstructure by using the short-term HEBM method. HEBM of gasless heterogeneous mixtures involve their processing in a high-speed planetary ball mill, where the particles of the mixture are subjected to mechanical impact with a force sufficient for breakdown of brittle components (e.g. graphite) and deformation of plastic components (e.g., Al, Ti, Ta, Ni). Brittle reactan...

Classical energetic materials, i.e., explosives, propellants and pyrotechnics are a class of material with a high amount of stored chemical energy that can be released during rapid exothermic reaction1-5. For example, explosives are usually generated by combining fuel and oxidizer groups into one molecule. The energy density of those materials is very high. For example, upon decomposition trinitrotoluene (TNT) releases 7.22 kJ/cm3 and forms 8.36 moles of gases per 100 g (Table 1) in a very short period of time. These materials are composed of micrometer-scale organic and inorganic species (fuels and oxidizers).
Thermite systems, where reactions take place between the inorganic compound, i.e., reducing metals (e.g., Al) and oxides (Fe2O3, CuO, Bi2O3), belong to another type of energetic materials. The energy density (15-21 kJ/cm3) of such systems exceeds that of TNT, however the amount of gas products (0.15-0.6 moles per 100 g) is typically much less than for explosives (Table 1). Also, the nano-thermites may show extremely high velocity of combustion wave propagation (&#62;1,000 m/sec)2-5.
It was recently shown6-12 that a number of gasless heterogeneous reactive systems (Ni+Al, Ti+C, Ti+B) that form intermetallic or refractory compounds could also be considered as energetic materials. The energy densities (kJ/cm3) of those systems are closer or higher than that of TNT (Table 1). At the same time, the absence of gas products during the reaction makes such materials excellent candidates for a variety of applications including synthesis of nanomaterials, reactive bonding of refractory and dissimilar parts, gasless micro power generators, etc.11-17. However, the relatively high ignition temperature of those systems (900-3,000 K, see Table 1) compared to thermites (~1,000 K) hinders their applications. The preparation of engineered nanostructured composites could significantly enhance the ignition and combustion characteristics of gasless heterogeneous systems12-14, 17.
Many methods have been developed to fabricate the engineered energetic nanocomposites, such as ultrasonic mixing18,19, self-assembly approaches5, sol-gel20-22, vapor deposition techniques16,17,23,24, as well as high-energy ball milling (HEBM)1,5. The disadvantage of ultrasonic mixing of nano-powder is that a thick (5-10 nm) oxide shell on metal nanoparticles reduces energy density and degrades the combustion performance of reactive mixtures. Also, the distribution of fuel and oxidizer is not uniform, and the interfacial contact between reactants is not intimate. Sol-gel and self-assembly strategies were developed for preparation of specific thermite nanocomposites. Despite being low-cost techniques, those strategies are not green from an environmental standpoint. Moreover, large amounts of impurities are introduced into prepared composites. Vapor deposition or magnetron sputtering is used to prepare reactive multi-layer foils and core-shell energetic materials. It provides a pore-free and well-defined geometry of composites that simplifies theoretical modeling and enhances accuracy. However, this technology is expensive and difficult to scale up. Furthermore, the prepared layered nanocomposites are unstable in certain conditions.
High-Energy Ball Milling (HEBM) is an environmentally friendly, easily scalable approach that allows effective fabrication of nanostructured energetic composites5,9-14. HEBM is inexpensive and can be used with various reactive material compositions (e.g., thermites, reactions that form intermetallics, carbides, borides, etc.).
The protocol provides a detailed description for preparation of reactive energetic (Ni+Al, Ti+C, Ta+C) nanocomposites with tailored microstructure by using the short-term HEBM method. It also describes a high-speed thermal imaging technique to determine the ignition/combustion characteristics of as-fabricated energetic materials. Finally it shows the analysis of the microstructure of the nanocomposites using Field Emission Scanning Electron Microscope (FESEM) Equipped by Focused Ion Beam (FIB). The protocol is an important guide for the preparation of different energetic nanomaterials (gasless and thermite systems) that could be used as either high energy density sources or for synthesis and processing of advanced nanomaterials by combustion-based approaches.

<table border="0" cellpadding="0" cellspacing="0">
	<tbody>
		<tr>
			<td>Titanium</td>
			<td>Alfa Aesar</td>
			<td>42624</td>
			<td>Particle size: -325 mesh</td>
			<td>Purity, 99.5%</td>
		</tr>
		<tr>
			<td>Graphite</td>
			<td>Alfa Aesar</td>
			<td>46304</td>
			<td>Particle size: 7-11 micron</td>
			<td>Purity, 99%</td>
		</tr>
		<tr>
			<td>Nickel</td>
			<td>Alfa Aesar</td>
			<td>10256</td>
			<td>Particle size: 3-7 micron</td>
			<td>Purity, 99.9%</td>
		</tr>
		<tr>
			<td>Aluminum</td>
			<td>Alfa Aesar</td>
			<td>11067</td>
			<td>Particle size: -325 mesh</td>
			<td>Purity, 99.5%</td>
		</tr>
		<tr>
			<td>Tantalum</td>
			<td>Materion advanced chemicals</td>
			<td>T-2017</td>
			<td>Particle size: 325 mesh</td>
			<td>Purity, 99.9%</td>
		</tr>
		<tr>
			<td>Carbon lampblack</td>
			<td>Fisher scientific</td>
			<td>C198-500</td>
			<td>Particle size: 0.1 micron</td>
			<td>Purity, 99.9%</td>
		</tr>
		<tr>
			<td>Tungsten wire</td>
			<td>Mcmaster Carr</td>
			<td>n/a</td>
			<td>0.032&#34; diameter</td>
			<td>n/a</td>
		</tr>
		<tr>
			<td>Planetary Ball Mill</td>
			<td>Retsch GmbH, Germany</td>
			<td>n/a</td>
			<td>n/a</td>
			<td>n/a</td>
		</tr>
		<tr>
			<td>Uniaxial press</td>
			<td>Carver Hydraulic</td>
			<td>n/a</td>
			<td>n/a</td>
			<td>n/a</td>
		</tr>
		<tr>
			<td>Sieve shaker</td>
			<td>Gilson performer</td>
			<td>n/a</td>
			<td>5mm diameter</td>
			<td>n/a</td>
		</tr>
		<tr>
			<td>Cylindrical stainless steel press die</td>
			<td>Action Machine</td>
			<td>n/a</td>
			<td>n/a</td>
			<td>n/a</td>
		</tr>
		<tr>
			<td>Stainless steel sieves</td>
			<td>Mcmaster Carr</td>
			<td>Type 304</td>
			<td>n/a</td>
			<td>n/a</td>
		</tr>
		<tr>
			<td>High-speed thermal camera (SC6000)</td>
			<td>FLIR</td>
			<td>n/a</td>
			<td>n/a</td>
			<td>n/a</td>
		</tr>
		<tr>
			<td>Helios NanoLab 600, Field Emission Scanning Electron Microscope (FESEM) Equipped by Focus Ion Beam (FIB)</td>
			<td>FEI</td>
			<td>n/a</td>
			<td>n/a</td>
			<td>n/a</td>
		</tr>
		<tr>
			<td>Cylindrical reactor with a vacuum pomp</td>
			<td>Action Machine</td>
			<td>n/a</td>
			<td>n/a</td>
			<td>n/a</td>
		</tr>
		<tr>
			<td>Autoslice and View (S&#38;V)</td>
			<td>FEI</td>
			<td>n/a</td>
			<td>n/a</td>
			<td>n/a</td>
		</tr>
		<tr>
			<td>Avizo Fire</td>
			<td>FEI</td>
			<td>n/a</td>
			<td>n/a</td>
			<td>n/a</td>
		</tr>
	</tbody>
</table>

preparation and reactivity of gasless nanostructured energetic materials

High-Energy Ball Milling (HEBM) is a ball milling process where a powder mixture placed in the ball mill is subjected to high-energy collisions from the balls. Among other applications, it is a versatile technique that allows for effective preparation of gasless reactive nanostructured materials with high energy density per volume (Ni+Al, Ta+C, Ti+C). The structural transformations of reactive media, which take place during HEBM, define the reaction mechanism in the produced energetic&#160;composites. Varying the processing conditions permits fine tuning of the milling-induced microstructures of the fabricated composite particles. In turn, the reactivity, i.e., self-ignition temperature, ignition delay time, as well as reaction kinetics, of high energy density materials depends on its microstructure. Analysis of the milling-induced microstructures suggests that the formation of fresh oxygen-free intimate high surface area contacts between the reagents is responsible for the enhancement of their reactivity. This manifests itself in a reduction of ignition temperature and delay time, an increased rate of chemical reaction, and an overall decrease of the effective activation energy of the reaction. The protocol provides a detailed description for the preparation of reactive nanocomposites with tailored microstructure using short-term HEBM method. It also describes a high-speed thermal imaging technique to determine the ignition/combustion characteristics of the energetic materials. The protocol can be adapted to preparation and characterization of a variety of nanostructured energetic composites.

To prepare nanostructured energetic composites, a mixture of desired powdered components (typically micrometer-sized) is mechanically treated under preset milling conditions. Processing time (typically minutes) is accurately controlled to generate the compositionally homogenized nanocomposite particles but not permitting the self-sustaining chemical reaction to initiate during milling.
Figure 1 and Video 1 show that contact surface area between the reactants i...

Watch this Scientific Journal Video about Preparation and Reactivity of Gasless Nanostructured Energetic Materials at JoVE.com

Preparation and Reactivity of Gasless Nanostructured Energetic Materials

This protocol describes the preparation of gasless nanostructured energetic materials (Ni+Al, Ta+C, Ti+C) using the short-term high-energy ball milling (HEBM) technique. It also describes a high-speed thermal imaging method to study the reactivity of mechanically fabricated nanocomposites. These protocols can be extended to other reactive nanostructured energetic materials.

High-Energy Ball Milling (HEBM) is a ball milling process where a powder mixture placed in the ball mill is subjected to high-energy collisions from the ...

preparation-reactivity-gasless-nanostructured-energetic

Research

JoVE Journal

Engineering

10.1K Views.  University of Notre Dame.  يصف هذا البروتوكول إعداد gasless ذات البنية النانومترية المواد النشيطة (ني + القاعدة، تا + C، C + تي) باستخدام الكرة قصيرة الأجل عالية الطاقة طحن (HEBM) تقنية. كما يصف عالية السرعة طريقة التصوير الحراري لدراسة التفاعل من nanocomposites ملفقة ميكانيكيا. هذه...

Video: Preparation and Reactivity of Gasless Nanostructured Energetic Materials

Nanomoulding of Functional Materials, a Versatile Complementary Pattern Replication Method to Nanoimprinting

We describe a nanomoulding technique which allows low-cost nanoscale patterning of functional materials, materials stacks and full devices. Nanomoulding combined with layer transfer enables the replication of arbitrary surface patterns from a master structure onto the functional material. Nanomoulding can be performed on any nanoimprinting setup and can be applied to a wide range of materials and deposition processes. In particular we demonstrate the fabrication of patterned transparent zinc oxide electrodes for light trapping applications in solar cells.

We describe a nanomoulding technique which allows low-cost nanoscale patterning of functional materials, materials stacks and full devices. Nanomoulding can be performed on any nanoimprinting setup and can be applied to a wide range of materials and deposition processes.

We describe a nanomoulding technique which  allows low-cost nanoscale patterning of functional materials, materials stacks  and full devices. Nanomoulding ...

Concurrent Quantitative Conductivity and Mechanical Properties Measurements of Organic Photovoltaic Materials using AFM

Organic photovoltaic (OPV) materials are inherently inhomogeneous at the nanometer scale. Nanoscale inhomogeneity of OPV materials affects performance of photovoltaic devices. Thus, understanding of spatial variations in composition as well as electrical properties of OPV materials is of paramount importance for moving PV technology forward.1,2 In this paper, we describe a protocol for quantitative measurements of electrical and mechanical properties of OPV materials with sub-100 nm resolution. Currently, materials properties measurements performed using commercially available AFM-based techniques (PeakForce, conductive AFM) generally provide only qualitative information. The values for resistance as well as Young's modulus measured using our method on the prototypical ITO/PEDOT:PSS/P3HT:PC61BM system correspond well with literature data. The P3HT:PC61BM blend separates onto PC61BM-rich and P3HT-rich domains. Mechanical properties of PC61BM-rich and P3HT-rich domains are different, which allows for domain attribution on the surface of the film. Importantly, combining mechanical and electrical data allows for correlation of the domain structure on the surface of the film with electrical properties variation measured through the thickness of the film.

Organic photovoltaic (OPV) materials are inherently inhomogeneous at the nanometer scale. Nanoscale inhomogeneity of OPV materials affects performance of photovoltaic devices. In this paper, we describe a protocol for quantitative measurements of electrical and mechanical properties of OPV materials with sub-100 nm resolution.

Organic photovoltaic  (OPV) materials are inherently inhomogeneous at the nanometer scale. Nanoscale  inhomogeneity of OPV materials affects performance ...

Preparation and Friction Force Microscopy Measurements of Immiscible, Opposing Polymer Brushes

Solvated polymer brushes are well known to lubricate high-pressure contacts, because they can sustain a positive normal load while maintaining low friction at the interface. Nevertheless, these systems can be sensitive to wear due to interdigitation of the opposing brushes. In a recent publication, we have shown via molecular dynamics simulations and atomic force microscopy experiments, that using an immiscible polymer brush system terminating the substrate and the slider surfaces, respectively, can eliminate such interdigitation. As a consequence, wear in the contacts is reduced. Moreover, the friction force is two orders of magnitude lower compared to traditional miscible polymer brush systems. This newly proposed system therefore holds great potential for application in industry. Here, the methodology to construct an immiscible polymer brush system of two different brushes each solvated by their own preferred solvent is presented. The procedure how to graft poly(N-isopropylacrylamide) (PNIPAM) from a flat surface and poly(methyl methacrylate) (PMMA) from an atomic force microscopy (AFM) colloidal probe is described. PNIPAM is solvated in water and PMMA in acetophenone. Via friction force AFM measurements, it is shown that the friction for this system is indeed reduced by two orders of magnitude compared to the miscible system of PMMA on PMMA solvated in acetophenone.

The methodology to perform friction force microscopy experiments for contacting brushes is presented: Two polymer brushes that are grafted from (a) substrates and (b) colloidal probes are slid to show that, by using two contacting immiscible brush systems, friction in sliding contacts is reduced compared to miscible brush systems.

Solvated polymer brushes are well known to lubricate high-pressure contacts, because they can sustain a positive normal load while maintaining low ...

Surface Enhanced Raman Spectroscopy Detection of Biomolecules Using EBL Fabricated Nanostructured Substrates

Fabrication and characterization of conjugate nano-biological systems interfacing metallic nanostructures on solid supports with immobilized biomolecules is reported. The entire sequence of relevant experimental steps is described, involving the fabrication of nanostructured substrates using electron beam lithography, immobilization of biomolecules on the substrates, and their characterization utilizing surface-enhanced Raman spectroscopy (SERS). Three different designs of nano-biological systems are employed, including protein A, glucose binding protein, and a dopamine binding DNA aptamer. In the latter two cases, the binding of respective ligands, D-glucose and dopamine, is also included. The three kinds of biomolecules are immobilized on nanostructured substrates by different methods, and the results of SERS imaging are reported. The capabilities of SERS to detect vibrational modes from surface-immobilized proteins, as well as to capture the protein-ligand and aptamer-ligand binding are demonstrated. The results also illustrate the influence of the surface nanostructure geometry, biomolecules immobilization strategy, Raman activity of the molecules and presence or absence of the ligand binding on the SERS spectra acquired.

We describe the fabrication and characterization of nano-biological systems interfacing nanostructured substrates with immobilized proteins and aptamers. The relevant experimental steps involving lithographic fabrication of nanostructured substrates, bio-functionalization, and surface-enhanced Raman spectroscopy (SERS) characterization, are reported. SERS detection of surface-immobilized proteins, and probing of protein-ligand and aptamer-ligand binding is demonstrated.

Fabrication and characterization of conjugate nano-biological systems interfacing metallic nanostructures on solid supports with immobilized biomolecules ...

Synthesis and Functionalization of 3D Nano-graphene Materials: Graphene Aerogels and Graphene Macro Assemblies

Efforts to assemble graphene into three-dimensional monolithic structures have been hampered by the high cost and poor processability of graphene. Additionally, most reported graphene assemblies are held together through physical interactions (e.g., van der Waals forces) rather than chemical bonds, which limit their mechanical strength and conductivity. This video method details recently developed strategies to fabricate mass-producible, graphene-based bulk materials derived from either polymer foams or single layer graphene oxide. These materials consist primarily of individual graphene sheets connected through covalently bound carbon linkers. They maintain the favorable properties of graphene such as high surface area and high electrical and thermal conductivity, combined with tunable pore morphology and exceptional mechanical strength and elasticity. This flexible synthetic method can be extended to the fabrication of polymer/carbon nanotube (CNT) and polymer/graphene oxide (GO) composite materials. Furthermore, additional post-synthetic functionalization with anthraquinone is described, which enables a dramatic increase in charge storage performance in supercapacitor applications.

This video method describes the synthesis of high surface area, monolithic 3D graphene-based materials derived from polymer precursors as well as single layer graphene oxide.

Efforts to assemble graphene into three-dimensional monolithic structures have been hampered by the high cost and poor processability of graphene. ...

Advanced Experimental Methods for Low-temperature Magnetotransport Measurement of Novel Materials

Novel electronic materials are often produced for the first time by synthesis processes that yield bulk crystals (in contrast to single crystal thin film synthesis) for the purpose of exploratory materials research. Certain materials pose a challenge wherein the traditional bulk Hall bar device fabrication method is insufficient to produce a measureable device for sample transport measurement, principally because the single crystal size is too small to attach wire leads to the sample in a Hall bar configuration. This can be, for example, because the first batch of a new material synthesized yields very small single crystals or because flakes of samples of one to very few monolayers are desired. In order to enable rapid characterization of materials that may be carried out in parallel with improvements to their growth methodology, a method of device fabrication for very small samples has been devised to permit the characterization of novel materials as soon as a preliminary batch has been produced. A slight variation of this methodology is applicable to producing devices using exfoliated samples of two-dimensional materials such as graphene, hexagonal boron nitride (hBN), and transition metal dichalcogenides (TMDs), as well as multilayer heterostructures of such materials. Here we present detailed protocols for the experimental device fabrication of fragments and flakes of novel materials with micron-sized dimensions onto substrate and subsequent measurement in a commercial superconducting magnet, dry helium close-cycle cryostat magnetotransport system at temperatures down to 0.300 K and magnetic fields up to 12 T.

We describe the methodology of mechanical exfoliation and deposition of flakes of novel materials with micron-sized dimensions onto substrate, fabrication of experimental device structures for transport experimentation, and the magnetotransport measurement in a dry helium close-cycle cryostat at temperatures down to 0.300 K and magnetic fields up to 12 T.

Novel electronic materials are often produced for the first time by synthesis processes that yield bulk crystals (in contrast to single crystal thin film ...

Nanostructured Ag-zeolite Composites as Luminescence-based Humidity Sensors

Small silver clusters confined inside zeolite matrices have recently emerged as a novel type of highly luminescent materials. Their emission has high external quantum efficiencies (EQE) and spans the whole visible spectrum. It has been recently reported that the UV excited luminescence of partially Li-exchanged sodium Linde type A zeolites [LTA(Na)] containing luminescent silver clusters can be controlled by adjusting the water content of the zeolite. These samples showed a dynamic change in their emission color from blue to green and yellow upon an increase of the hydration level of the zeolite, showing the great potential that these materials can have as luminescence-based humidity sensors at the macro and micro scale. Here, we describe the detailed procedure to fabricate a humidity sensor prototype using silver-exchanged zeolite composites. The sensor is produced by suspending the luminescent Ag-zeolites in an aqueous solution of polyethylenimine (PEI) to subsequently deposit a film of the material onto a quartz plate. The coated plate is subjected to several hydration/dehydration cycles to show the functionality of the sensing film.

A protocol for the synthesis of moisture-responsive luminescent Ag-zeolite composites is described in this report.

Small silver clusters confined inside zeolite matrices have recently emerged as a novel type of highly luminescent materials. Their emission has high ...

High Temperature Fabrication of Nanostructured Yttria-Stabilized-Zirconia (YSZ) Scaffolds by In Situ Carbon Templating Xerogels

We demonstrate a method for the high temperature fabrication of porous, nanostructured yttria-stabilized-zirconia (YSZ, 8 mol% yttria - 92 mol% zirconia) scaffolds with tunable specific surface areas up to 80 m2&#183;g-1. An aqueous solution of a zirconium salt, yttrium salt, and glucose is mixed with propylene oxide (PO) to form a gel. The gel is dried under ambient conditions to form a xerogel. The xerogel is pressed into pellets and then sintered in an argon atmosphere. During sintering, a YSZ ceramic phase forms and the organic components decompose, leaving behind amorphous carbon. The carbon formed in situ serves as a hard template, preserving a high surface area YSZ nanomorphology at sintering temperature. The carbon is subsequently removed by oxidation in air at low temperature, resulting in a porous, nanostructured YSZ scaffold. The concentration of the carbon template and the final scaffold surface area can be systematically tuned by varying the glucose concentration in the gel synthesis. The carbon template concentration was quantified using thermogravimetric analysis (TGA), the surface area and pore size distribution was determined by physical adsorption measurements, and the morphology was characterized using scanning electron microscopy (SEM). Phase purity and crystallite size was determined using X-ray diffraction (XRD). This fabrication approach provides a novel, flexible platform for realizing unprecedented scaffold surface areas and nanomorphologies for ceramic-based electrochemical energy conversion applications, e.g. solid oxide fuel cell (SOFC) electrodes.

High Temperature Fabrication of Nanostructured Yttria-Stabilized-Zirconia YSZ Scaffolds by In Situ Carbon Templating Xerogels

A protocol for fabricating porous, nanostructured yttria-stabilized-zirconia (YSZ) scaffolds at temperatures between 1,000 &#176;C and 1,400 &#176;C is presented.

We demonstrate a method for the high temperature fabrication of porous, nanostructured yttria-stabilized-zirconia (YSZ, 8 mol% yttria - 92 mol% zirconia) ...

Characterization of Ultra-fine Grained and Nanocrystalline Materials Using Transmission Kikuchi Diffraction

One of the challenges in microstructure analysis nowadays resides in the reliable and accurate characterization of ultra-fine grained (UFG) and nanocrystalline materials. The traditional techniques associated with scanning electron microscopy (SEM), such as electron backscatter diffraction (EBSD), do not possess the required spatial resolution due to the large interaction volume between the electrons from the beam and the atoms of the material. Transmission electron microscopy (TEM) has the required spatial resolution. However, due to a lack of automation in the analysis system, the rate of data acquisition is slow which limits the area of the specimen that can be characterized. This paper presents a new characterization technique, Transmission Kikuchi Diffraction (TKD), which enables the analysis of the microstructure of UFG and nanocrystalline materials using an SEM equipped with a standard EBSD system. The spatial resolution of this technique can reach 2 nm. This technique can be applied to a large range of materials that would be difficult to analyze using traditional EBSD. After presenting the experimental set up and describing the different steps necessary to realize a TKD analysis, examples of its use on metal alloys and minerals are shown to illustrate the resolution of the technique and its flexibility in term of material to be characterized.

This paper provides a detailed method to characterize the microstructure of ultra-fine grained and nanocrystalline materials using a scanning electron microscope equipped with a standard electron backscatter diffraction system. Metal alloys and minerals presenting refined microstructures are analyzed using this technique, showing the diversity of its possible applications.

One of the challenges in microstructure analysis nowadays resides in the reliable and accurate characterization of ultra-fine grained (UFG) and ...

Preparation of Liquid Crystal Networks for Macroscopic Oscillatory Motion Induced by Light

A strategy based on doped liquid crystalline networks is described to create mechanical self-sustained oscillations of plastic films under continuous light irradiation. The photo-excitation of dopants that can quickly dissipate light into heat, coupled with anisotropic thermal expansion and self-shadowing of the film, gives rise to the self-sustained deformation. The oscillations observed are influenced by the dimensions and the modulus of the film, and by the directionality and intensity of the light. The system developed offers applications in energy conversion and harvesting for soft-robotics and automated systems.
The general method described here consists of creating free-standing liquid crystalline films and characterizing the mechanical and thermal effects observed. The molecular alignment is achieved using alignment layers (rubbed polyimide), commonly used in the display manufacturing industry. To obtain actuators with large deformation, the mesogens are aligned and polymerized in a splay/bend configuration, i.e., with the director of the liquid crystals (LCs) going gradually from planar to homeotropic through the film thickness. Upon irradiation, the mechanical and thermal oscillations obtained are monitored with a high-speed camera. The results are further quantified by image analysis using an image processing program.

The goal of the protocol is to create liquid crystalline polymer films that can mechanically oscillate under continuous light irradiation. We describe in great detail the conception of free-standing films, from the liquid crystal alignment method to the photo-actuation. The experimental protocol applied to prepare this material is broadly applicable.

A strategy based on doped liquid crystalline networks is described to create mechanical self-sustained oscillations of plastic films under continuous ...