Name: synthesis and reaction chemistry of nanosize monosodium titanate
Uploaded: 2016-02-23T14:00:00
Description: Watch this Scientific Journal Video about Synthesis and Reaction Chemistry of Nanosize Monosodium Titanate at JoVE.com

The authors thank the Laboratory Directed Research and Development program at the Savannah River National Laboratory (SRNL) for funding. We thank Dr. Fernando Fondeur for collection and interpretation of the FT-IR spectra and Dr. John Seaman of the Savannah River Ecology Laboratory for the use of the DLS instrument for particle size measurements. We also thank the Dr. Daniel Chan of the University of Washington and the National Institute of Health (Grant #1R01DE021373-01), for funding experiments investigating the ion exchange reactions with Au(III). The Savannah River National Laboratory is operated by Savannah River Nuclear Solutions, LLC for the Department of Energy under contract DE-AC09-08SR22470.

1. Synthesis of Nano-monosodium Titanate (nMST)
<ol>
	<li>Prepare 10 ml of solution #1 by adding 0.58 ml of 25 wt % sodium methoxide solution to 7.62 ml of isopropanol followed by 1.8 ml of titanium isopropoxide.</li>
	<li>Prepare 10 ml of solution #2 by adding 0.24 ml of ultrapure water to 9.76 ml of isopropanol.</li>
	<li>Add 280 ml of isopropanol to a 3-neck 500-ml round bottom flask, followed by 0.44 ml of Triton X-100 (average MW: 625 g/mol). Stir the solution well with a magnetic stir bar.</li>
	<li>Prepare a dua...

<ol>
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P. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Delaminated+titanate+and+peroxotitanate+photocatalysts.">Delaminated titanate and peroxotitanate photocatalysts.</a> Appl. Catal. B. 105 (1-2), 69-76 (2011).</li><li>Rejman, J., Oberle, V., Zuhorn, I. S., Hoekstra, D. <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+internalization+of+particles+via+the+pathways+of+clathrin-+and+caveolae-mediated+endocytosis.">Size-dependent internalization of particles via the pathways of clathrin- and caveolae-mediated endocytosis.</a> Biochem. J. 377 (1), 159-169 (2004).</li><li>Hobbs, D. T., Taylor-Pashow, K. M. L., Elvington, M. C. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Formation+of+nanosized+metal+particles+on+a+titanate+carrier.">Formation of nanosized metal particles on a titanate carrier.</a> US patent application. , (2015).</li><li>Elvington, M. C., Tosten, M., Taylor-Pashow, K. M. L., Hobbs, D. T. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Synthesis+and+characterization+of+nanosize+sodium+titanates.">Synthesis and characterization of nanosize sodium titanates.</a> J. Nanopart. Res. 14, 1114 (2012).</li><li>Duff, M. C., Hunter, D. B., Hobbs, D. T., Fink, S. D., Dai, Z., Bradley, J. P. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Mechanisms+of+strontium+and+uranium+removal+from+high-level+radioactive+waste+simulant+solutions+by+the+sorbent+monosodium+titanate.">Mechanisms of strontium and uranium removal from high-level radioactive waste simulant solutions by the sorbent monosodium titanate.</a> Environ. Sci. Technol. 38 (19), 5201-5207 (2004).</li><li>Puangpetch, T., Sreethawong, T., Chavadej, S. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Hydrogen+production+over+metal-loaded+mesoporous-assembled+SrTiO3+nanocrystal+photocatalysts:+effects+of+metal+type+and+loading.">Hydrogen production over metal-loaded mesoporous-assembled SrTiO3 nanocrystal photocatalysts: effects of metal type and loading.</a> Int. J. Hydrogen Energy. 35 (13), 6531-6540 (2010).</li><li>Fan, 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=Facile+method+to+synthesize+mesoporous+multimetal+oxides+(ATiO3,+A+=+Sr,+Ba)+with+large+specific+surface+areas+and+crystalline+pore+walls.">Facile method to synthesize mesoporous multimetal oxides (ATiO3, A = Sr, Ba) with large specific surface areas and crystalline pore walls.</a> Chem. Mater. 22 (4), 1276-1278 (2010).</li><li>Rossmanith, R., 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=Porous+anatase+nanoparticles+with+high+specific+area+prepared+by+miniemulsion+technique.">Porous anatase nanoparticles with high specific area prepared by miniemulsion technique.</a> Chem. 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Acta. 52 (23), 6470-6475 (2007).</li><li>Bouras, P., Stathatos, E., Lianos, P. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Pure+versus+metal-ion-doped+nanocrystalline+titania+for+photocatalysis.">Pure versus metal-ion-doped nanocrystalline titania for photocatalysis.</a> Appl. Catal. B. 73 (1-2), 51-59 (2007).</li><li>Bonino, R., 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=Ti-Peroxo+species+in+the+TS-1/H2O2/H2O+system.">Ti-Peroxo species in the TS-1/H2O2/H2O system.</a> J. Phys. Chem. 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The presence of extraneous water, for example from impure reagents, can alter the outcome of the reaction, leading to larger or more polydisperse particles. Therefore, care should be taken to ensure dry reactants are used. The titanium isopropoxide and sodium methoxide should be stored in a desiccator when not in use. High purity isopropanol should also be used for the synthesis.
Temperature was found to play a key role in the conversion of the product from a gel to particulate form. TEM image...

Titanium dioxide and alkali metal titanates are widely used in a variety of applications such as pigments in paint and skin care products and as photocatalysts in energy conversion and utilization.1-3 Sodium titanates have been shown to be effective materials to remove a range of cations over a wide range of pH conditions through cation exchange reactions.4-7
In addition to the applications just described, micron-sized sodium titanates and sodium peroxotitanates have recently been shown to also serve as a therapeutic metal delivery platform. In this application, therapeutic metal ions such as Au(III), Au(I), and Pt(II) are exchanged for the sodium ions of monosodium titanate (MST). In vitro tests with the noble metal-exchanged titanates indicate suppression of the growth of cancer and bacterial cells by an unknown mechanism.8,9
Historically, sodium titanates have been produced using both sol-gel and hydrothermal synthetic techniques resulting in fine powders with particle sizes ranging from a few to several hundred microns.4,5,10,11 More recently, synthetic methods have been reported that produced nanosize titanium dioxide, metal-doped titanium oxides, and a variety of other metal titanates. Examples include sodium titanium oxide nanotubes (NaTONT) or nanowires by reaction of titanium dioxide in excess sodium hydroxide at elevated temperature and pressure,12-14 sodium titanate nanofibers by reaction of peroxotitanic acid with excess sodium hydroxide at elevated temperature and pressure,15 and sodium and cesium titanate nanofibers by delamination of acid-exchanged micron-sized titanates.16
The synthesis of nanosize sodium titanates and sodium peroxotitanates is of interest to enhance ion exchange kinetics, which are typically controlled by film diffusion or intraparticle diffusion. These mechanisms are largely controlled by the particle size of the ion exchanger. In addition, as a therapeutic metal delivery platform, the particle size of the titanate material would be expected to significantly affect the nature of the interaction between the metal-exchanged titanate and the cancer and bacterial cells. For example, bacterial cells, which are typically on the order of 0.5 &#8211; 2 &#181;m, would likely have different interactions with micron size particles versus nanosized particles. In addition, non-phagocytic eukaryotic cells have been shown to only internalize particles with a size of less than 1 micron.17 Thus, the synthesis of nanosize sodium titanates is also of interest to facilitate metal delivery and cellular uptake from the titanate delivery platform. Reducing the size of sodium titanates and peroxotitanates will also increase the effective capacity in metal ion separations and enhance photochemical properties of the material.16,18 This paper describes a protocol developed to synthesize nanosize monosodium titanate (nMST) under mild sol-gel conditions.19 The preparation of the corresponding peroxide modified nMST; along with an ion-exchange reaction to load the nMST with Au(III) are also described.

<table border="0" cellpadding="0" cellspacing="0" width="923">
	<tbody>
		<tr>
			<td>Titanium(IV) isopropoxide</td>
			<td>Sigma Aldrich</td>
			<td>377996</td>
			<td>99.999% trace metals basis</td>
		</tr>
		<tr>
			<td>Isopropyl alcholol, 99.9%</td>
			<td>Sigma Aldrich</td>
			<td>650447</td>
			<td>HPLC grade (Chomasolv)</td>
		</tr>
		<tr>
			<td>Sodium methoxide in methanol</td>
			<td>Sigma Aldrich</td>
			<td>156256</td>
			<td>25 wt%</td>
		</tr>
		<tr>
			<td>Triton X-100</td>
			<td>Sigma Aldrich</td>
			<td>T9284</td>
			<td>BioXtra</td>
		</tr>
		<tr>
			<td>hydrogen tetrachloroaurate(III) trihydrate</td>
			<td>Sigma Aldrich</td>
			<td>G4022</td>
			<td>ACS reagent grade</td>
		</tr>
		<tr>
			<td>hydrogen peroxide (30 wt%)</td>
			<td>Fisher</td>
			<td>H325</td>
			<td>Certified ACS</td>
		</tr>
		<tr>
			<td>10-mL syringes</td>
			<td>Fisher</td>
			<td>14-823-16E</td>
			<td></td>
		</tr>
		<tr>
			<td>Dual channel syringe pump</td>
			<td>Cole Parmer</td>
			<td>EW-74900-10</td>
			<td>Or equivalent programmable dual channel syringe pump</td>
		</tr>
		<tr>
			<td>Tygon tubing 1/8 inch ID, 1/4 inch OD</td>
			<td>Cole Parmer</td>
			<td>EW-0640776</td>
			<td></td>
		</tr>
		<tr>
			<td>Tygon tubing 1/16 inch ID, 1/8 inch OD</td>
			<td>Cole Parmer</td>
			<td>EW-0740771</td>
			<td></td>
		</tr>
		<tr>
			<td>0.1-&#181;m Nylon filter</td>
			<td>Fisher</td>
			<td>R01SP04700</td>
			<td></td>
		</tr>
		<tr>
			<td>Labquake shaker rotisserie</td>
			<td>Thermo Scientific</td>
			<td>4002110Q</td>
			<td></td>
		</tr>
	</tbody>
</table>

synthesis and reaction chemistry of nanosize monosodium titanate

This paper describes the synthesis and peroxide-modification of nanosize monosodium titanate (nMST), along with an ion-exchange reaction to load the material with Au(III) ions. The synthesis method was derived from a sol-gel process used to produce micron-sized monosodium titanate (MST), with several key modifications, including altering reagent concentrations, omitting a particle seed step, and introducing a non-ionic surfactant to facilitate control of particle formation and growth. The resultant nMST material exhibits spherical-shaped particle morphology with a monodisperse distribution of particle diameters in the range from 100 to 150&#160;nm. The nMST material was found to have a Brunauer-Emmett-Teller (BET) surface area of 285 m2g-1, which is more than an order of magnitude higher than the micron-sized MST. The isoelectric point of the nMST measured 3.34 pH units, which is a pH unit lower than that measured for the micron-size MST. The nMST material was found to serve as an effective ion exchanger under weakly acidic conditions for the preparation of an Au(III)-exchange nanotitanate. In addition, the formation of the corresponding peroxotitanate was demonstrated by reaction of the nMST with hydrogen peroxide.

MST is synthesized using a sol-gel method in which tetraisopropoxytitanium(IV) (TIPT), sodium methoxide, and water are combined and reacted in isopropanol to form seed particles of MST.4 Micron-sized particles are then grown by controlled addition of additional quantities of the reagents. The resultant particles feature an amorphous core and an outer fibrous region having dimensions of about 10 nm wide by 50 nm in length.20
Figure 1A shows a typical parti...

Watch this Scientific Journal Video about Synthesis and Reaction Chemistry of Nanosize Monosodium Titanate at JoVE.com

Synthesis and Reaction Chemistry of Nanosize Monosodium Titanate

The surfactant mediated sol-gel synthesis of nanosized monosodium titanate is described, along with preparation of the corresponding peroxide modified material. An ion-exchange reaction with Au(III) is also presented.

This paper describes the synthesis and peroxide-modification of nanosize monosodium titanate (nMST), along with an ion-exchange reaction to load the ...

The overall goal of the following experiment is to prepare nanosized sodium titanate materials including peroxide-modified and gold(III)loaded materials. This is achieved by first performing a surfactant-mediated sol-gel synthesis to prepare nanosized monosodium titanate particles in the range of 100 to 150 nanometers. As a second step, the nanosized monosodium titanate can be treated with hydrogen peroxide which converts a portion of the material to a peroxotitanate form.Next, an ion-exchange reaction can be performed to prepare metal-loaded titanates for various applications. An example is the addition of a solution of gold(III)chloride to the nanotitanate to produce the corresponding gold(III)exchanged titanate. Results are obtained that show spherical particles in the range of 100 to 150 nanometers can be prepared using the method, based on electron microscopy imaging and dynamic light scattering measurements.We first had the idea for this method when we began looking at the application of titanates in the biomedical field where particle size becomes more important. This method can be extended to materials normally synthesized using sol-gel techniques, allowing materials with a range of different particle sizes to be prepared. Nanosized particles, monosodium titanate, provide the opportunity to improve ion exchange performance due to their higher surface area to volume ratio.Use of metal exchange titanates as bactericides can be enhanced with nanosized materials. To begin the synthesis of nano monosodium titanate, or nMST, first add 0.58 milliliters of 25 weight percent sodium methoxide solution to 7.62 milliliters of isopropanol followed by 1.8 milliliters of titanium isopropoxide. Label the solution number one.Next, add 0.24 milliliters of ultra-pure water to 9.76 milliliters of isopropanol to make solution number two. Add 0.44 milliliters of Triton X-100 to 280 milliliters of isopropanol in a three-neck flask and stir well with a magnetic stirrer. Fit the syringe ends with tubing of sufficient length to deliver the solutions below the level of the liquid in the flask and load solutions one and two into two separate syringes.Next, place the syringes into a dual-channel syringe pump and deliver the solutions at a rate of 0.333 milliliters per minute to the flask. After addition, cap the flask and continue stirring for 24 hours at room temperature. Afterwards, uncap the flask and heat the mixture to reflux for 45 to 90 minutes.Purge the flask with nitrogen and add ultra-pure water in portions to replace evaporated isopropanol as heating is continued. After most of the isopropanol has evaporated and the volume of water added has reached approximately 50 milliliters, remove the heat from the flask and allow the mixture to cool. Filter the product through a 0.1 micron nylon filter paper and wash it several times with water.Finally, transfer the slurry from the filter into a pre-weighed bottle and store it at ambient temperature. To determine the yield, weigh an aliquot of the aqueous slurry before and after drying. To perform the exchange with gold(III)ions, first transfer 6.50 grams of the 4.23 weight percent slurry of nMST to a 50 milliliter centrifuge tube.Next, add about one milliliter of water to 0659 grams of hydrogen tetrachloro gold(III)trihydrate in a one dram glass vial. Transfer the solution to the centrifuge tube. Continue by rinsing the glass vial with water and adding it to the tube.Repeat this several times to ensure that all of the gold reagent is transferred. Add water to the tube to bring the total volume up to 11 milliliters. Wrap the tube in foil and then tumble it on a shaker for a minimum of four days.After tumbling the mixture, centrifuge the tube for 15 minutes. Discard the supernatant and re-suspend the solids in distilled water. Centrifuge the sample again and repeat the washing procedure twice more.Finally, re-suspend the solids in water and store in the dark at room temperature. To prepare peroxotitanate, begin by adding five grams of a 9.8 weight percent slurry of nMST to a flask and stir the slurry magnetically. Continue by adding dropwise 0.154 grams of a 30 weight percent hydrogen peroxide solution to the flask, which induces a color change from white to yellow.Continue stirring the mixture at ambient temperature for 24 hours. Next, filter the product through a 0.1 micron nylon filter paper and was the product several times with water to remove any un-reacted hydrogen peroxide. Finally, transfer the slurry from the filter into a pre-weighed bottle and store the aqueous slurry of peroxotitanate at ambient temperature.Shown here is a typical particle size distribution as measured by dynamic light scattering using the established sol-gel method. Note that this synthesis produces a multimodal distribution of particles with the majority around one micrometer. When reaction conditions that aimed to reduce the particle size of the monosodium titanate were employed, which involved removing the seeding step and using more dilute reagents, this resulted in a bimodal distribution of particle sizes centered at 50 to 100 nanometers and 500 nanometers after 24 hours.After 48 hours, a trimodal distribution of particles measuring up to 1000 nanometers was observed, as demonstrated in this graph. Importantly, the addition of Triton X-100 during the synthesis of nMST is critical for producing an almost uniform particle size distribution as measured by dynamic light scattering. Transmission and scanning electron microscopy showed that the Triton X-100 produced nMST particles at a more uniform size and morphology when compared to those of monosodium titanate.The surface modification of nMST particles by hydrogen peroxide was confirmed by the appearance of an absorption band at 883 wave numbers in its Fourier transform infrared spectrum. After its development, this technique paved the way for researchers in the field of biological applications of inorganic materials to explore the use of nanotitanates to deliver therapeutic metals and the metal exchange titanates to service bactericides. After watching this video, you should have good understanding of how to prepare nanoscale particles of monosodium titanate along with the peroxide-modified and metal-loaded forms.Remember that working with flammable solvents and reagents can be extremely hazardous. Precautions should be taken to prevent the buildup of flammable vapors. It is recommended that sol-gel synthesis be carried out in a chemical fume hood.

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Preparation and Use of Samarium Diiodide (SmI2) in Organic Synthesis: The Mechanistic Role of HMPA and Ni(II) Salts in the Samarium Barbier Reaction

Although initially considered an esoteric reagent, SmI2 has become a common tool for synthetic organic chemists. SmI2 is generated through the addition of molecular iodine to samarium metal in THF.1,2-3 It is a mild and selective single electron reductant and its versatility is a result of its ability to initiate a wide range of reductions including C-C bond-forming and cascade or sequential reactions. SmI2 can reduce a variety of functional groups including sulfoxides and sulfones, phosphine oxides, epoxides, alkyl and aryl halides, carbonyls, and conjugated double bonds.2-12 One of the fascinating features of SmI-2-mediated reactions is the ability to manipulate the outcome of reactions through the selective use of cosolvents or additives. In most instances, additives are essential in controlling the rate of reduction and the chemo- or stereoselectivity of reactions.13-14 Additives commonly utilized to fine tune the reactivity of SmI2 can be classified into three major groups: (1) Lewis bases (HMPA, other electron-donor ligands, chelating ethers, etc.), (2) proton sources (alcohols, water etc.), and (3) inorganic additives (Ni(acac)2, FeCl3, etc).3
Understanding the mechanism of SmI2 reactions and the role of the additives enables utilization of the full potential of the reagent in organic synthesis. The Sm-Barbier reaction is chosen to illustrate the synthetic importance and mechanistic role of two common additives: HMPA and Ni(II) in this reaction. The Sm-Barbier reaction is similar to the traditional Grignard reaction with the only difference being that the alkyl halide, carbonyl, and Sm reductant are mixed simultaneously in one pot.1,15 Examples of Sm-mediated Barbier reactions with a range of coupling partners have been reported,1,3,7,10,12 and have been utilized in key steps of the synthesis of large natural products.16,17 Previous studies on the effect of additives on SmI2 reactions have shown that HMPA enhances the reduction potential of SmI2 by coordinating to the samarium metal center, producing a more powerful,13-14,18 sterically encumbered reductant19-21 and in some cases playing an integral role in post electron-transfer steps facilitating subsequent bond-forming events.22 In the Sm-Barbier reaction, HMPA has been shown to additionally activate the alkyl halide by forming a complex in a pre-equilibrium step.23
Ni(II) salts are a catalytic additive used frequently in Sm-mediated transformations.24-27 Though critical for success, the mechanistic role of Ni(II) was not known in these reactions. Recently it has been shown that SmI2 reduces Ni(II) to Ni(0), and the reaction is then carried out through organometallic Ni(0) chemistry.28
These mechanistic studies highlight that although the same Barbier product is obtained, the use of different additives in the SmI2 reaction drastically alters the mechanistic pathway of the reaction. The protocol for running these SmI2-initiated reactions is described.

Preparation and Use of Samarium Diiodide SmI2 in Organic Synthesis: The Mechanistic Role of HMPA and NiII Salts in the Samarium Barbier Reaction

A straightforward procedure for the preparation of samarium diiodide (SmI2) in THF is described. The role of two main additives namely hexamethylphosphoramide (HMPA) and Ni(acac)2 in Sm mediated reactions is demonstrated in the Sm-Barbier reaction.

Although initially considered an esoteric reagent, SmI2 has become a common tool for synthetic organic chemists. SmI2 is generated through the addition of ...

Amide Coupling Reaction for the Synthesis of Bispyridine-based Ligands and Their Complexation to Platinum as Dinuclear Anticancer Agents

Amide coupling reactions can be used to synthesize bispyridine-based ligands for use as bridging linkers in multinuclear platinum anticancer drugs. Isonicotinic acid, or its derivatives, are coupled to variable length diaminoalkane chains under an inert atmosphere in anhydrous DMF or DMSO with the use of a weak base, triethylamine, and a coupling agent, 1-propylphosphonic anhydride. The products precipitate from solution upon formation or can be precipitated by the addition of water. If desired, the ligands can be further purified by recrystallization from hot water. Dinuclear platinum complex synthesis using the bispyridine ligands is done in hot water using transplatin. The most informative of the chemical characterization techniques to determine the structure and gross purity of both the bispyridine ligands and the final platinum complexes is 1H NMR with particular analysis of the aromatic region of the spectra (7-9 ppm). The platinum complexes have potential application as anticancer agents and the synthesis method can be modified to produce trinuclear and other multinuclear complexes with different hydrogen bonding functionality in the bridging ligand.

This protocol describes the use of amide coupling reactions of isonicotinic acid and diaminoalkanes to form bridging ligands suitable for use in the synthesis of multinuclear platinum complexes, which combine aspects of the anticancer drugs BBR3464 and picoplatin.

Amide coupling reactions can be used to synthesize bispyridine-based ligands for use as bridging linkers in multinuclear platinum anticancer drugs. ...

Synthesis and Characterization of Functionalized Metal-organic Frameworks

Metal-organic frameworks have attracted extraordinary amounts of research attention, as they are attractive candidates for numerous industrial and technological applications. Their signature property is their ultrahigh porosity, which however imparts a series of challenges when it comes to both constructing them and working with them. Securing desired MOF chemical and physical functionality by linker/node assembly into a highly porous framework of choice can pose difficulties, as less porous and more thermodynamically stable congeners (e.g., other crystalline polymorphs, catenated analogues) are often preferentially obtained by conventional synthesis methods. Once the desired product is obtained, its characterization often requires specialized techniques that address complications potentially arising from, for example, guest-molecule loss or preferential orientation of microcrystallites. Finally, accessing the large voids inside the MOFs for use in applications that involve gases can be problematic, as frameworks may be subject to collapse during removal of solvent molecules (remnants of solvothermal synthesis). In this paper, we describe synthesis and characterization methods routinely utilized in our lab either to solve or circumvent these issues. The methods include solvent-assisted linker exchange, powder X-ray diffraction in capillaries, and materials activation (cavity evacuation) by supercritical CO2 drying. Finally, we provide a protocol for determining a suitable pressure region for applying the Brunauer-Emmett-Teller analysis to nitrogen isotherms, so as to estimate surface area of MOFs with good accuracy.

Synthesis, activation, and characterization of intentionally designed metal-organic framework materials is challenging, especially when building blocks are incompatible or unwanted polymorphs are thermodynamically favored over desired forms. We describe how applications of solvent-assisted linker exchange, powder X-ray diffraction in capillaries and activation via supercritical CO2 drying, can address some of these challenges.

Metal-organic frameworks have attracted extraordinary amounts of research attention, as they are attractive candidates for numerous industrial and ...

Highly Stereoselective Synthesis of 1,6-Ketoesters Mediated by Ionic Liquids: A Three-component Reaction Enabling Rapid Access to a New Class of Low Molecular Weight Gelators

In organic chemistry ionic liquids (ILs) have emerged as safe and recyclable reaction solvents. In the presence of a base ILs can be deprotonated to form catalytically active N-Heterocyclic Carbenes (NHCs). Here we have used ILs as precatalysts in the addition of &#945;,&#946;-unsaturated aldehydes to chalcones to form 1,6-ketoesters, incorporating an anti-diphenyl moiety in a highly stereoselective fashion. The reaction has a broad substrate scope and several functional groups and heteroaromatics can be integrated into the ketoester backbone in generally good yields with maintained stereoselectivity. The reaction protocol is robust and scalable. The starting materials are inexpensive and the products can be obtained after simple filtration, avoiding solvent-demanding chromatography. Furthermore, the IL can be recycled up to 5 times without any loss of reactivity. Moreover, the 1,6-ketoester end product is a potent gelator in several hydrocarbon based solvents. The method enables rapid access to and evaluation of a new class of low molecular weight gelators (LMWGs) from recyclable and inexpensive starting materials.

Ionic liquids (ILs) mediate fast, simple and cheap access to 1,6-ketoesters in high diastereoselectivities and good yields. The reaction protocol is robust and the 1,6-ketoesters can be obtained in gram scale after a simple filtration protocol. Moreover, the 1,6-ketoesters are potent gelators in hydrocarbon solvents.

In organic chemistry ionic liquids (ILs) have emerged as safe and recyclable reaction solvents. In the presence of a base ILs can be deprotonated to form ...

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 ...

Synthesis and Characterization of Supramolecular Colloids

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

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

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

Synthesis of Protein Bioconjugates via Cysteine-maleimide Chemistry

The chemical linking or bioconjugation of proteins to fluorescent dyes, drugs, polymers and other proteins has a broad range of applications, such as the development of antibody drug conjugates (ADCs) and nanomedicine, fluorescent microscopy and systems chemistry. For many of these applications, specificity of the bioconjugation method used is of prime concern. The Michael addition of maleimides with cysteine(s) on the target proteins is highly selective and proceeds rapidly under mild conditions, making it one of the most popular methods for protein bioconjugation.
We demonstrate here the modification of the only surface-accessible cysteine residue on yeast cytochrome c with a ruthenium(II) bisterpyridine maleimide. The protein bioconjugation is verified by gel electrophoresis and purified by aqueous-based fast protein liquid chromatography in 27% yield of isolated protein material. Structural characterization with MALDI-TOF MS and UV-Vis is then used to verify that the bioconjugation is successful. The protocol shown here is easily applicable to other cysteine - maleimide coupling of proteins to other proteins, dyes, drugs or polymers.

Synthesis of Protein Bioconjugates via Cysteine-maleimide Chemistry

This protocol details the important steps required for the bioconjugation of a cysteine containing protein to a maleimide, including reagent purification, reaction conditions, bioconjugate purification and bioconjugate characterization.

The chemical linking or bioconjugation of proteins to fluorescent dyes, drugs, polymers and other proteins has a broad range of applications, such as the ...

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

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

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

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

Continuous Flow Chemistry: Reaction of Diphenyldiazomethane with p-Nitrobenzoic Acid

Continuous flow technology has been identified as instrumental for its environmental and economic advantages leveraging superior mixing, heat transfer and cost savings through the &#34;scaling out&#34; strategy as opposed to the traditional &#34;scaling up&#34;. Herein, we report the reaction of diphenyldiazomethane with p-nitrobenzoic acid in both batch and flow modes. To effectively transfer the reaction from batch to flow mode, it is essential to first conduct the reaction in batch. As a consequence, the reaction of diphenyldiazomethane was first studied in batch as a function of temperature, reaction time, and concentration to obtain kinetic information and process parameters. The glass flow reactor set-up is described and combines two types of reaction modules with &#34;mixing&#34; and &#34;linear&#34; microstructures. Finally, the reaction of diphenyldiazomethane with p-nitrobenzoic acid was successfully conducted in the flow reactor, with up to 95% conversion of the diphenyldiazomethane in 11 min. This proof of concept reaction aims to provide insight for scientists to consider flow technology&#39;s competitiveness, sustainability, and versatility in their research.

Continuous Flow Chemistry: Reaction of Diphenyldiazomethane with p-Nitrobenzoic Acid

Flow chemistry carries environmental and economic advantages by leveraging superior mixing, heat transfer and cost benefits. Herein, we provide a blueprint to transfer chemical processes from batch to flow mode. The reaction of diphenyldiazomethane (DDM) with p-nitrobenzoic acid, conducted in batch and flow, was chosen for proof of concept.

Continuous flow technology has been identified as instrumental for its environmental and economic advantages leveraging superior mixing, heat transfer and ...

Synthesis and Mass Spectrometry Analysis of Oligo-peptoids

Peptoids are sequence-controlled peptide-mimicking oligomers consisting of N-alkylated glycine units. Among many potential applications, peptoids have been thought of as a type of molecular information storage. Mass spectrometry analysis has been considered the method of choice for sequencing peptoids. Peptoids can be synthesized via solid phase chemistry using a repeating two-step reaction cycle. Here we present a method to manually synthesize oligo-peptoids and to analyze the sequence of the peptoids using tandem mass spectrometry (MS/MS) techniques. The sample peptoid is a nonamer consisting of alternating N-(2-methyloxyethyl)glycine (Nme) and N-(2-phenylethyl)glycine (Npe), as well as an N-(2-aminoethyl)glycine (Nae) at the N-terminus. The sequence formula of the peptoid is Ac-Nae-(Npe-Nme)4-NH2, where Ac is the acetyl group. The synthesis takes place in a commercially available solid-phase reaction vessel. The rink amide resin is used as the solid support to yield the peptoid with an amide group at the C-terminus. The resulting peptoid product is subjected to sequence analysis using a triple-quadrupole mass spectrometer coupled to an electrospray ionization source. The MS/MS measurement produces a spectrum of fragment ions resulting from the dissociation of charged peptoid. The fragment ions are sorted out based on the values of their mass-to-charge ratio (m/z). The m/z values of the fragment ions are compared against the nominal masses of theoretically predicted fragment ions, according to the scheme of peptoid fragmentation. The analysis generates a fragmentation pattern of the charged peptoid. The fragmentation pattern is correlated to the monomer sequence of the neutral peptoid. In this regard, MS analysis reads out the sequence information of the peptoids.

A protocol is described for the manual synthesis of oligo-peptoids followed by sequence analysis by mass spectrometry.

Peptoids are sequence-controlled peptide-mimicking oligomers consisting of N-alkylated glycine units. Among many potential applications, peptoids have ...