Name: synthesis and exfoliation of discotic zirconium phosphates to obtain colloidal liquid crystals
Uploaded: 2016-05-25T13:00:00
Description: Watch this Scientific Journal Video about Synthesis and Exfoliation of Discotic Zirconium Phosphates to Obtain Colloidal Liquid Crystals at JoVE.com

This work is partially supported by NSF (DMR-1006870) and NASA (NASA-NNX13AQ60G). X. Z. Wang acknowledges support from the Mary Kay O'Connor Process Safety Center (MKOPSC) at Texas A&amp;M University. We also thank Min Shuai for her guidance.

1. Synthesis of &#945;-ZrP Using Hydrothermal Method
<ol>
	<li>Dissolve 6&#160;g of zirconyl chloride octahydrate (ZrOCl2&#183;8H2O) in 3.75&#160;ml deionized (DI) water in a 150 ml round bottom flask.</li>
	<li>Add 48&#160;ml of 15&#160;M phosphoric acid (H3PO4) dropwise to the ZrOCl2 solution prepared in step 1.1 followed by adding 8.25 ml&#160; deionized (DI) water under vigorous stirring.</li>
	<li>Pour resulting gel-like mixture into Teflon-lined pressure vess...

<ol>
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A. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=The+preparation+of+crystalline+zirconium+phosphate+and+some+observations+on+its+ion+exchange+behaviour.">The preparation of crystalline zirconium phosphate and some observations on its ion exchange behaviour.</a> J. Inorg. Nucl. Chem. 26, 117-129 (1964).</li><li>Shuai, M., Mejia, A. F., Chang, Y. W., Cheng, Z. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Hydrothermal+synthesis+of+layered+alpha-zirconium+phosphate+disks:+control+of+aspect+ratio+and+polydispersity+for+nano-architecture.">Hydrothermal synthesis of layered alpha-zirconium phosphate disks: control of aspect ratio and polydispersity for nano-architecture.</a> Crystengcomm. 15, 1970-1977 (2013).</li><li>Sun, L., Boo, W. J., Sue, H. -. J., Clearfield, A. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Preparation+of+&#945;-zirconium+phosphate+nanoplatelets+with+wide+variations+in+aspect+ratios.">Preparation of &#945;-zirconium phosphate nanoplatelets with wide variations in aspect ratios.</a> New J. Chem. 31, 39-43 (2007).</li><li>Gawande, M. B., Shelke, S. N., Zboril, R., Varma, R. S. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Microwave-sssisted+chemistry:+synthetic+applications+for+rapid+assembly+of+nanomaterials+and+organics.">Microwave-sssisted chemistry: synthetic applications for rapid assembly of nanomaterials and organics.</a> Accounts Chem. Res. 47, 1338-1348 (2014).</li><li>Chang, Y. -. W., Mejia, A. F., Cheng, Z., Di, X., McKenna, G. B. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Gelation+via+Ion+Exchange+in+Discotic+Suspensions.">Gelation via Ion Exchange in Discotic Suspensions.</a> Phys. Rev. Lett. 108, 247802 (2012).</li><li>Wang, 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=Thermo-sensitive+discotic+colloidal+liquid+crystals.">Thermo-sensitive discotic colloidal liquid crystals.</a> Soft Matter. 10, 7692-7695 (2014).</li><li>Li, H., Wang, X., Chen, Y., Cheng, Z. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Temperature-dependent+isotropic-to-nematic+of+charged+nanoplates.">Temperature-dependent isotropic-to-nematic of charged nanoplates.</a> Phys. Rev. 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E. 80, 041704 (2009).</li><li>Wong, 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=Large-scale+self-assembled+zirconium+phosphate+smectic+layers+via+a+simple+spray-coating+process.">Large-scale self-assembled zirconium phosphate smectic layers via a simple spray-coating process.</a> Nat. Commun. 5, 3589 (2014).</li><li>Diaz, A., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Zirconium+phosphate+nano-platelets:+a+novel+platform+for+drug+delivery+in+cancer+therapy.">Zirconium phosphate nano-platelets: a novel platform for drug delivery in cancer therapy.</a> Chem. Commun. 48, 1754-1756 (2012).</li><li>Kim, H. -. N., Keller, S. W., Mallouk, T. 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The reflux method is a good option for making a smaller size of &#945;-ZrP with a uniform diameter and thickness. Similar to the hydrothermal method, the reflux method is limited by the preparation time. In general, it takes longer time for the crystals to grow.
The longer reaction time required for reflux method may result in nanodisks with a larger size. The average size of exfoliated nanodisks is measured by dynamic light scattering (DLS). In this study, the size of exfoliated ZrP nanodisks...

Discotic colloids are naturally abundant in the form of clay, asphaltene, red blood cells, and nacre. A range of applications in many engineered systems, including polymer nanocomposites1, biomimetic materials, functional membranes2, discotic liquid crystal studies3 and Pickering emulsion stabilizers4 are developed based on discotic colloidal nanodisks. Nanodisks with uniformity and low polydispersity is important for studying phases and transformations of liquid crystals. Zirconium phosphate (ZrP) is a synthetic nanodisks with well-ordered layered structure and controllable aspect ratio (thickness over diameter). Therefore, the exploration of different synthesis of ZrP helps to establish fundamental understanding of discotic liquid crystal system.
The structure of ZrP was elucidated by Clearfield and Stynes in 19645. For the synthesis of layered crystals of ZrP, hydrothermal and reflux methods are commonly adopted6,7. Hydrothermal method gives a good control on size ranging from 400 to 1,500 nm and polydispersity within 25%6, while reflux method gives smaller crystals for the same duration time. Microwave heating has been proven to be a promising method for synthesis of nanomaterials8. However, there are no papers describing synthesis of ZrP based on microwave-assisted route. The effective control over size, aspect ratio, and mechanism of the crystal growth by hydrothermal method was systematically studied by our group6.
ZrP can be easily exfoliated into monolayers in aqueous suspensions, and the exfoliated ZrP have been well established as liquid crystal materials in Cheng&#39;s group3,9-13. So far, exfoliated ZrP nanodisks with various diameters, say different aspect ratios, have been studied to conclude that larger ZrP had the I (isotropic)-N (nematic) transition at lower concentration compared to smaller ZrP3. The polydispersity3, salt9 and temperature10,11 effects on the formation of nematic liquid crystal phase have been also considered. Moreover, other phases, such as sematic liquid crystal phase, have been investigated as well13,14.
In this article, we demonstrate experimental realization of such a colloidal ZrP nanodisks suspension. Layered ZrP crystals are synthesized via different methods, and then are exfoliated in aqueous media to obtain monolayer nanodisks. At the end, we show liquid crystal phase transitions exhibited by this system. A notable aspect of these disks is their highly anisotropic nature that the thickness to diameter ratio is in the range of 0.0007 to 0.05 depending on the size of disks3. The highly anisotropic monolayer nanodisks establish a model system to study phase transitions in the suspensions of nanodisks.

<table border="0" cellpadding="0" cellspacing="0" height="202" width="928">
	<tbody>
		<tr height="21">
			<td height="21" style="height:21px;width:209px;">Material</td>
			<td style="width:208px;"></td>
			<td style="width:164px;"></td>
			<td style="width:352px;"></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">Zirconyl Chloride Octahydrate</td>
			<td>Fischer Scientific (Acros Organics)</td>
			<td>AC20837-5000</td>
			<td>98% +&#160;</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">o-Phosphoric Acid</td>
			<td>Fischer Scientific</td>
			<td>A242-1</td>
			<td>&#62;= 85 %</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">Tetra Butyl Ammonium Hydroxide</td>
			<td>Acros Organics (Acros Organics)</td>
			<td>AC176610025</td>
			<td>40% wt. (1.5M)</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">Name</td>
			<td>Company</td>
			<td>Catalog Number</td>
			<td>Comments</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">Equipment</td>
			<td></td>
			<td></td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">Reaction Oven</td>
			<td>Fischer Scientific</td>
			<td>CL2 centrifuge</td>
			<td>Isotemperature Oven (Temperature Upto 350&#160;C)</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">Centrifuge&#160;</td>
			<td>Thermo Scientific</td>
			<td>Not Available&#160;</td>
			<td>Rotation Speed : 100 - 4000 rpm</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">Microwave Reactor</td>
			<td>CEM Corporation</td>
			<td>Discover and Explorer SP</td>
			<td>Temp. Upto 300oC, Power upto 300W, Pressure upto 30bar</td>
		</tr>
	</tbody>
</table>

synthesis and exfoliation of discotic zirconium phosphates to obtain colloidal liquid crystals

Due to their abundance in natural clay and potential applications in advanced materials, discotic nanoparticles are of interest to scientists and engineers. Growth of such anisotropic nanocrystals through a simple chemical method is a challenging task. In this study, we fabricate discotic nanodisks of zirconium phosphate [Zr(HPO4)2&#183;H2O] as a model material using hydrothermal, reflux and microwave-assisted methods. Growth of crystals is controlled by duration time, temperature, and concentration of reacting species. The novelty of the adopted methods is that discotic crystals of size ranging from hundred nanometers to few micrometers can be obtained while keeping the polydispersity well within control. The layered discotic crystals are converted to monolayers by exfoliation with tetra-(n)-butyl ammonium hydroxide [(C4H9)4NOH, TBAOH]. Exfoliated disks show isotropic and nematic liquid crystal phases. Size and polydispersity of disk suspensions is highly important in deciding their phase behavior.

Figure 1a-c show SEM images of &#945;-ZrP nanodisks obtained from hydrothermal, reflux, and microwave-assisted methods, respectively. It was observed that &#945;-ZrP nanodisks show hexagonal in shape and different thickness depending on synthesis conditions and prepared methods. A previously reported study from our group6 suggests that for the crystal growth time 48 hours or above, the edge of the disks become sharper. Usually, the reflux method yields nanodisk...

Watch this Scientific Journal Video about Synthesis and Exfoliation of Discotic Zirconium Phosphates to Obtain Colloidal Liquid Crystals at JoVE.com

Synthesis and Exfoliation of Discotic Zirconium Phosphates to Obtain Colloidal Liquid Crystals

A two dimensional model material of discotic zirconium phosphate was developed. The inorganic crystal with lamellar structure was synthesized by hydrothermal, reflux, and microwave-assisted methods. On exfoliation with organic molecules, layered crystals can be converted to monolayers, and nematic liquid crystal phase was formed at sufficient concentration of monolayers.

Due to their abundance in natural clay and potential applications in advanced materials, discotic nanoparticles are of interest to scientists and ...

The overall goal of this zirconium phosphate synthesis by three methods and its exfoliation is to obtain various aspect ratio nano platelets which can serve as a model discotic liquid crystal system. This method can help answer key questions in the synthesis of different sizes of zirconium phosphate in the exfoliation techniques field. Such is how to control the aspect ratio of the zirconium phosphate by various synthesis methods, and importantly how to obtain nearly mono dispersed zirconium phosphate nano platelets.The minute one day of the technique that we demonstrated is that where they will obtain zirconium phosphate nano plates off sizes ranging from 200 nanometers to 2, 000 nanometers with good control and for proper disposary. This method provide insight into liquid crystal model materials it can also be applied for other systems such as pickling emulsifiers. To synthesize alpha zirconium phosphate using the hydrothermal method dissolve six grams of zirconochloride octahydrate in 3.75 mL of deionized water in a beaker.Add 48 mL of 15 molar phosphoric acid into a teflon lined pressure vessel followed by 8.25 mL of water. Then add the zirconochloride solution drop wise to the phosphoric acid solution under vigorous stirring. Place the vessel into a hydrothermal autoclave composed of a stainless steel shell, pressure plate, and lid and then tighten it well.Place the hydrothermal autoclave into a convection oven at 200 degrees Celsius for 24 hours. After the reaction, allow the hydrothermal autoclave to cool down eight hours to room temperature under ambient cooling. Transfer the supernatant liquid portion in the reactor to a waste disposal container since it contains unreacted phosphoric acid which is corrosive.Collect alpha zirconium phosphate nano platelets in two centrifuge tubes. Add 40 mL of water to each centrifuge tube and vortex for one minute. After centrifuging the tubes at 2, 500 x g for five minutes, remove the top liquid in the tubes.Repeat this step three times to ensure that all of the acid is washed away. Dry the zirconium phosphate water sticky mixture in an oven at 65 degrees Celsius for eight hours and then grind it using a mortar and pestle. To synthesize alpha zirconium phosphate using the reflux method, mix six grams of zirconochloride octahydrate with 60 mL of 12 molar phosphoric acid in a 150 mL round bottom flask.Reflux the prepared mixture in an oil bath at 94 degrees Celsius for 24 hours. Wash the product with deionized water three times as done for hydrothermal synthesis and then dry the zirconium phosphate water sticky mixture in the oven at 65 degrees Celsius for eight hours. Grind the dried bulky sample into powder using a mortar and pestle and stock for later use.To synthesize alpha zirconium phosphate using the microwave assisted method add one gram of zirconochloride octahydrate into 10 mL of 12 molar phosphoric acid solution and stir the resulting mixture well in a 20 mL scintillation vial. Pour 5 mL of the resulting mixture into a 10 mL glass vessel specified for a microwave reactor. Set the reaction temperature to 150 degrees Celsius, set the pressure limit to 300 psi and allow the reaction to happen for one hour.After the reaction, let the glass vessel cool down for about 15 minutes and then follow the same procedure as before for acid washing and drying of alpha zirconium phosphate crystals. Disperse one gram of alpha zirconium phosphate into 7.8 mL of deionized water in a 45 mL centrifuge tube. Add 2.2 mL of TBAOH then vortex for at least 40 seconds.Notice that the molar ratio of zirconium to TBAOH is kept at 1:1. Sonicate the resulting concentrated suspension for one to two hours. Leave the sonicated suspension for two to three days to allow full intercalation of tetrabutyl ammonium cations and complete exfoliation of crystals.Optionally, concentrated suspension can be diluted with water to obtain better exfoliation. In this case, add 20 mL of water to 10 mL of exfoliated suspension. Centrifuge the exfoliated samples at high rotation speed for half an hour to remove the bottom sediment and the top liquid.Collect the middle part in another container. Add another five mL of water and centrifuge again for half an hour. After letting the suspension settle over night remove the top liquid and stock the remaining suspension for liquid crystal study.The suspension can be diluted at different ratios to see isotropic, nomadic and other possible phases. Scanning electron microscopy, or SCM, images of pristine alpha zirconium phosphate prepared via the hydrothermal method, the reflux method, and the microwave assisted method are shown. Shown here are transmission electron microscopy images of the microwave assisted growth of zirconium phosphate crystals at 150 degrees Celsius.The phosphate nano platelet is shown at 10 minutes and at 60 minutes. In this image the left bottle contains unexfoliated zirconium phosphate suspended in water and the right bottle has exfloliated zirconium phosphate nano platelets. Different dilutions of stock suspension are shown to exhibit liquid crystal and isotropic nomadic co-existent phase except for the last two vials which are fully nomadic.The image is a snapshot of the suspensions placed between crossed polarizers. Once mastered this technique can be done in one hour to synthesize layered zirconium phoshate nano platelets in the four days to obtain liquid crystals if it is performed properly. While working out this procedure, one should make sure that the precursors are mixed well.Following this procedure other studies like nano plates stabilize pickling motion can be also performed in other through answer additional questions such as two dimensional materials in pickling emulsifications. After its development this technique for the researchers in the field of software and condense matter to explore liquid crystals of inorganic and aquatic systems. After watching this video you should have the understanding how to synthesize nearly mono dispersed zirconium phosphate nano platelets.And then use them for different applications in the fundamental studies on liquid crystals. Don't forget working with phosphoric acid can be extremely hydrous so when you are doing experiments don't forget the personal protective equipment and also you need to deal with the wasted acid properly.

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Research

JoVE Journal

Chemistry

Nucleoside Triphosphates - From Synthesis to Biochemical Characterization

The traditional strategy for the introduction of chemical functionalities is the use of solid-phase synthesis by appending suitably modified phosphoramidite precursors to the nascent chain. However, the conditions used during the synthesis and the restriction to rather short sequences hamper the applicability of this methodology. On the other hand, modified nucleoside triphosphates are activated building blocks that have been employed for the mild introduction of numerous functional groups into nucleic acids, a strategy that paves the way for the use of modified nucleic acids in a wide-ranging palette of practical applications such as functional tagging and generation of ribozymes and DNAzymes. One of the major challenges resides in the intricacy of the methodology leading to the isolation and characterization of these nucleoside analogues.
	
	In this video article, we present a detailed protocol for the synthesis of these modified analogues using phosphorous(III)-based reagents. In addition, the procedure for their biochemical characterization is divulged, with a special emphasis on primer extension reactions and TdT tailing polymerization. This detailed protocol will be of use for the crafting of modified dNTPs and their further use in chemical biology.

The protocol described herein aims to explain and abridge the numerous obstacles in the way of the intricate route leading to modified nucleoside triphosphates. Consequently, this protocol facilitates both the synthesis of these activated building-blocks and their availability for practical applications.

The  traditional strategy for the introduction of chemical functionalities is the  use of solid-phase synthesis by appending suitably modified ...

Exfoliation of Egyptian Blue and Han Blue, Two Alkali Earth Copper Silicate-based Pigments

In a visualized example of the ancient past connecting with modern times, we describe the preparation and exfoliation of CaCuSi4O10 and BaCuSi4O10, the colored components of the historic Egyptian blue and Han blue pigments. The bulk forms of these materials are synthesized by both melt flux and solid-state routes, which provide some control over the crystallite size of the product. The melt flux process is time intensive, but it produces relatively large crystals at lower reaction temperatures. In comparison, the solid-state method is quicker yet requires higher reaction temperatures and yields smaller crystallites. Upon stirring in hot water, CaCuSi4O10 spontaneously exfoliates into monolayer nanosheets, which are characterized by TEM and PXRD. BaCuSi4O10 on the other hand requires ultrasonication in organic solvents to achieve exfoliation. Near infrared imaging illustrates that both the bulk and nanosheet forms of CaCuSi4O10 and BaCuSi4O10 are strong near infrared emitters. Aqueous CaCuSi4O10 and BaCuSi4O10 nanosheet dispersions are useful because they provide a new way to handle, characterize, and process these materials in colloidal form.

The preparation and exfoliation of CaCuSi4O10&#160;and BaCuSi4O10 are described. Upon stirring in hot water, CaCuSi4O10 spontaneously exfoliates into monolayers, whereas BaCuSi4O10&#160;requires ultrasonication in organic solvents. Near infrared (NIR) imaging illustrates the NIR emission properties of these materials, and aqueous dispersions of these nanomaterials are useful for solution processing.

In a visualized example of the ancient past connecting with modern times, we describe the preparation and exfoliation of CaCuSi4O10 and BaCuSi4O10, the ...

Quantitative and Qualitative Examination of Particle-particle Interactions Using Colloidal Probe Nanoscopy

Colloidal Probe Nanoscopy (CPN), the study of the nano-scale interactive forces between a specifically prepared colloidal probe and any chosen substrate using the Atomic Force Microscope (AFM), can provide key insights into physical interactions present within colloidal systems. Colloidal systems are widely existent in several applications including, pharmaceuticals, foods, paints, paper, soil and minerals, detergents, printing and much more.1-3 Furthermore, colloids can exist in many states such as emulsions, foams and suspensions. Using colloidal probe nanoscopy one can obtain key information on the adhesive properties, binding energies and even gain insight into the physical stability and coagulation kinetics of the colloids present within. Additionally, colloidal probe nanoscopy can be used with biological cells to aid in drug discovery and formulation development. In this paper we describe a method for conducting colloidal probe nanoscopy, discuss key factors that are important to consider during the measurement, and show that both quantitative and qualitative data that can be obtained from such measurements.

Colloidal probe nanoscopy can be used within a variety of fields to gain insight into the physical stability and coagulation kinetics of colloidal systems and aid in drug discovery and formulation sciences using biological systems. The method described within provides a quantitative and qualitative means to study such systems.

Colloidal Probe Nanoscopy (CPN), the study of the nano-scale interactive forces between a specifically prepared colloidal probe and any chosen substrate ...

From Constructs to Crystals &#8211; Towards Structure Determination of &#946;-barrel Outer Membrane Proteins

Membrane proteins serve important functions in cells such as nutrient transport, motility, signaling, survival and virulence, yet constitute only ~1% percent of known structures. There are two types of membrane proteins, &#945;-helical and &#946;-barrel. While &#945;-helical membrane proteins can be found in nearly all cellular membranes, &#946;-barrel membrane proteins can only be found in the outer membranes of mitochondria, chloroplasts, and Gram-negative bacteria. One common bottleneck in structural studies of membrane proteins in general is getting enough pure sample for analysis. In hopes of assisting those interested in solving the structure of their favorite &#946;-barrel outer membrane protein (OMP), general protocols are presented for the production of target &#946;-barrel OMPs at levels useful for structure determination by either X-ray crystallography and/or NMR spectroscopy. Here, we outline construct design for both native expression and for expression into inclusion bodies, purification using an affinity tag, and crystallization using detergent screening, bicelle, and lipidic cubic phase techniques. These protocols have been tested and found to work for most OMPs from Gram-negative bacteria; however, there are some targets, particularly for mitochondria and chloroplasts that may require other methods for expression and purification. As such, the methods here should be applicable for most projects that involve OMPs from Gram-negative bacteria, yet the expression levels and amount of purified sample will vary depending on the target OMP.

From Constructs to Crystals &amp;#8211; Towards Structure Determination of &amp;#946;-barrel Outer Membrane Proteins

&#946;-barrel outer membrane proteins (OMPs) serve many functions within the outer membranes of Gram-negative bacteria, mitochondria, and chloroplasts. Here, we hope to alleviate a known bottleneck in structural studies by presenting protocols for the production of &#946;-barrel OMPs in sufficient quantities for structure determination by X-ray crystallography or NMR spectroscopy.

Membrane proteins serve important functions in cells such as nutrient transport, motility, signaling, survival and virulence, yet constitute only ~1% ...

Synthesis of Programmable Main-chain Liquid-crystalline Elastomers Using a Two-stage Thiol-acrylate Reaction

This study presents a novel two-stage thiol-acrylate Michael addition-photopolymerization (TAMAP) reaction to prepare main-chain liquid-crystalline elastomers (LCEs) with facile control over network structure and programming of an aligned monodomain. Tailored LCE networks were synthesized using routine mixing of commercially available starting materials and pouring monomer solutions into molds to cure. An initial polydomain LCE network is formed via a self-limiting thiol-acrylate Michael-addition reaction. Strain-to-failure and glass transition behavior were investigated as a function of crosslinking monomer, pentaerythritol tetrakis(3-mercaptopropionate) (PETMP). An example non-stoichiometric system of 15 mol% PETMP thiol groups and an excess of 15 mol% acrylate groups was used to demonstrate the robust nature of the material. The LCE formed an aligned and transparent monodomain when stretched, with a maximum failure strain over 600%. Stretched LCE samples were able to demonstrate both stress-driven thermal actuation when held under a constant bias stress or the shape-memory effect when stretched and unloaded. A permanently programmed monodomain was achieved via a second-stage photopolymerization reaction of the excess acrylate groups when the sample was in the stretched state. LCE samples were photo-cured and programmed at 100%, 200%, 300%, and 400% strain, with all samples demonstrating over 90% shape fixity when unloaded. The magnitude of total stress-free actuation increased from 35% to 115% with increased programming strain. Overall, the two-stage TAMAP methodology is presented as a powerful tool to prepare main-chain LCE systems and explore structure-property-performance relationships in these fascinating stimuli-sensitive materials.

A novel methodology is presented to synthesize and program main-chain liquid-crystalline elastomers using commercially available starting monomers. A wide range of thermomechanical properties was tailored by adjusting the amount of crosslinker, while the actuation performance was dependent on the amount of applied strain during programming.

This study presents a novel two-stage thiol-acrylate Michael addition-photopolymerization (TAMAP) reaction to prepare main-chain liquid-crystalline ...

From Molecules to Materials: Engineering New Ionic Liquid Crystals Through Halogen Bonding

Herein, we demonstrate that a bottom-up approach, based on halogen bonding (XB), can be successfully applied for the design of a new type of ionic liquid crystals (ILCs). Taking advantages of the high specificity of XB for haloperfluorocarbons and the ability of anions to act as XB-acceptors, we obtained supramolecular complexes based on 1-alkyl-3-methylimidazolium iodides and iodoperfluorocarbons, overcoming the well-known immiscibility between hydrocarbons (HCs) and perfluorocarbons (PFCs). The high directionality of the XB combined with the fluorophobic effect, allowed us to obtain enantiotropic liquid crystals where a rigid, non-aromatic, XB supramolecular anion acts as mesogenic core.
X-ray structure analysis of the complex between 1-ethyl-3-methylimidazolium iodide and iodoperfluorooctane showed the presence of a layered structure, which is a manifestation of the well-known tendency to segregation of perfluoroalkyl chains. This is consistent with the observation of smectic mesophases. Moreover, all the reported complexes melt below 100 &#176;C, and most are mesomorphic even at room temperature, despite that the starting materials were non-mesomorphic in nature.
The supramolecular strategy reported here provides new design principles for mesogen design allowing a totally new class of functional materials.

A protocol for the synthesis of a new type of mesogens, based on the halogen-bonded supramolecular anion [CnF2n+1-I&#183;&#183;&#183;I&#183;&#183;&#183;I-CnF2n+1]&#8722;, is reported.

Herein, we demonstrate that a bottom-up approach, based on halogen bonding (XB), can be successfully applied for the design of a new type of ionic liquid ...

Facet-to-facet Linking of Shape-anisotropic Colloidal Cadmium Chalcogenide Nanostructures

Here, we describe a protocol that allows for shape-anisotropic cadmium chalcogenide nanocrystals (NCs), such as nanorods (NRs) and tetrapods (TPs), to be covalently and site-specifically linked via their end facets, resulting in polymer-like linear or branched chains. The linking procedure begins with a cation-exchange process in which the end facets of the cadmium chalcogenide NCs are first converted to silver chalcogenide. This is followed by the selective removal of ligands at their surface. This results in cadmium chalcogenide NCs with highly reactive silver chalcogenide end facets that spontaneously fuse upon contact with each other, thereby establishing an interparticle facet-to-facet attachment. Through the judicious choice of precursor concentrations, an extensive network of linked NCs can be produced. Structural characterization of the linked NCs is carried out via low- and high-resolution transmission electron microscopy (TEM), as well as energy-dispersive X-ray spectroscopy, which confirm the presence of silver chalcogenide domains between chains of cadmium chalcogenide NCs.

A protocol detailing how shape-anisotropic colloidal cadmium chalcogenide nanocrystals can be covalently linked via their end facets is presented here.

Here, we describe a protocol that allows for shape-anisotropic cadmium chalcogenide nanocrystals (NCs), such as nanorods (NRs) and tetrapods (TPs), to be ...

Novel Techniques for Observing Structural Dynamics of Photoresponsive Liquid Crystals

We discuss in this article the experimental measurements of the molecules in liquid crystal (LC) phase using the time-resolved infrared (IR) vibrational spectroscopy and time-resolved electron diffraction. Liquid crystal phase is an important state of matter that exists between the solid and liquid phases and it is common in natural systems as well as in organic electronics. Liquid crystals are orientationally ordered but loosely packed, and therefore, the internal conformations and alignments of the molecular components of LCs can be modified by external stimuli. Although advanced time-resolved diffraction techniques have revealed picosecond-scale molecular dynamics of single crystals and polycrystals, direct observations of packing structures and ultrafast dynamics of soft materials have been hampered by blurry diffraction patterns. Here, we report time-resolved IR vibrational spectroscopy and electron diffractometry to acquire ultrafast snapshots of a columnar LC material bearing a photoactive core moiety. Differential-detection analyses of the combination of time-resolved IR vibrational spectroscopy and electron diffraction are powerful tools for characterizing structures and photoinduced dynamics of soft materials.

Here, we present the protocols of differential-detection analyses of time-resolved infrared vibrational spectroscopy and electron diffraction which enable observations of the deformations of local structures around photoexcited molecules in a columnar liquid crystal, giving an atomic perspective on the relationship between the structure and the dynamics of this photoactive material.

We discuss in this article the experimental measurements of the molecules in liquid crystal (LC) phase using the time-resolved infrared (IR) vibrational ...

Synthesis of Substrate-Bound Au Nanowires Via an Active Surface Growth Mechanism

Advancing synthetic capabilities is important for the development of nanoscience and nanotechnology. The synthesis of nanowires has always been a challenge, as it requires asymmetric growth of symmetric crystals. Here, we report a distinctive synthesis of substrate-bound Au nanowires. This template-free synthesis employs thiolated ligands and substrate adsorption to achieve the continuous asymmetric deposition of Au in solution at ambient conditions. The thiolated ligand prevented the Au deposition on the exposed surface of the seeds, so the Au deposition only occurs at the interface between the Au seeds and the substrate. The side of the newly deposited Au nanowires is immediately covered with the thiolated ligand, while the bottom facing the substrate remains ligand-free and active for the next round of Au deposition. We further demonstrate that this Au nanowire growth can be induced on various substrates, and different thiolated ligands can be used to regulate the surface chemistry of the nanowires. The diameter of the nanowires can also be controlled with mixed ligands, in which another &#34;bad&#34; ligand could turn on the lateral growth. With the understanding of the mechanism, Au nanowire-based nanostructures can be designed and synthesized.

We report a solution-based method to synthesize substrate-bound Au nanowires. By tuning the molecular ligands used during the synthesis, the Au nanowires can be grown from various substrates with different surface properties. Au nanowire-based nanostructures can also be synthesized by adjusting the reaction parameters.

Advancing synthetic capabilities is important for the development of nanoscience and nanotechnology. The synthesis of nanowires has always been a ...

Exfoliation and Analysis of Large-area, Air-Sensitive Two-Dimensional Materials

We describe methods for producing and analyzing large, thin flakes of air-sensitive two-dimensional materials. Thin flakes of layered or van der Waals crystals are produced using mechanical exfoliation, in which layers are peeled off a bulk crystal using adhesive tape. This method produces high-quality flakes, but they are often small and can be hard to find, particularly for materials with relatively high cleavage energies such as black phosphorus. By heating the substrate and the tape, two-dimensional material adhesion to the substrate is promoted, and the flake yield can be increased by up to a factor of ten. After exfoliation, it is necessary to image or otherwise analyze these flakes but some two-dimensional materials are sensitive to oxygen or water and will degrade when exposed air. We have designed and tested a hermetic transfer cell to temporarily maintain the inert environment of a glovebox so that air-sensitive flakes can be imaged and analyzed with minimal degradation. The compact design of the transfer cell is such that optical analysis of sensitive materials can be performed outside of a glovebox without specialized equipment or modifications to existing equipment.

A method for exfoliating large thin flakes of air sensitive two-dimensional materials and safely transporting them for analysis outside of a glovebox is presented.

We describe methods for producing and analyzing large, thin flakes of air-sensitive two-dimensional materials. Thin flakes of layered or van der Waals ...