Name: localized bathless metal-composite plating via electrostamping
Uploaded: 2020-09-22T12:30:00
Description: Watch this Scientific Journal Video about Localized Bathless Metal-Composite Plating via Electrostamping at JoVE.com

This work was supported by the Aircraft Equipment Reliability and Maintainability Improvement Program and the Patuxent Partnership. Townsend was supported by an ONR Faculty Research Fellowship. The authors also acknowledge the general support of the SMCM Chemistry and Biochemistry Department faculty and students, including support from the SMCM football team.

1. Preparing coating salts
CAUTION: Nickel salts and boric acid are toxic and should be handled with proper personal protective equipment including nitrile gloves, goggles and a lab coat. Strong acids and bases should be handled in the fume hood, and all waste chemicals should be disposed of as hazardous waste.
<ol>
	<li>Using a balance, weigh out the following powders in these ratios: 10.000 g of NiSO4&#183;6H2O, 2.120 g of NiCl2&#183;6H2O, 1.600 ...

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T. J., Wills, R. G. A., Walsh, F. C. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Electrodeposition+of+composite+coatings+containing+nanoparticles+in+a+metal+deposit.">Electrodeposition of composite coatings containing nanoparticles in a metal deposit.</a> Surface and Coatings Technology. 201 (1), 371-383 (2006).</li><li>Gerwitz, C. N., David, H. M., Yan, Y., Shaw, J. P., Townsend, T. K. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Bathless+Inorganic+Composite+Nickel+Plating:+Dry-Cell+Stamping+of+Large+Hygroscopic+Phosphor+Crystals.">Bathless Inorganic Composite Nickel Plating: Dry-Cell Stamping of Large Hygroscopic Phosphor Crystals.</a> Advanced Materials Interfaces. 7 (4), (2020).</li><li>Bite, I., 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=Novel+method+of+phosphorescent+strontium+aluminate+coating+preparation+on+aluminum.">Novel method of phosphorescent strontium aluminate coating preparation on aluminum.</a> Materials and Design. 160 (15), 794-802 (2018).</li><li>Feldstein, M. D. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Coatings+with+identification+and+authentication+properties.">Coatings with identification and authentication properties.</a> US Patent. , (2012).</li><li>Rose, I., Whittingham, C. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=.">.</a> Nickel Plating Handbook. , (2014).</li><li>Anderson, D. 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=.">.</a> Electroplating Engineering Handbook. , (1996).</li><li>Helle, K., Walsh, F. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Electrodeposition+of+Composite+Layers+Consisting+of+Inert+Inclusions+in+a+Metal+Matrix.">Electrodeposition of Composite Layers Consisting of Inert Inclusions in a Metal Matrix.</a> Transactions of the Institute of Metal Finishing. 75 (2), 53-58 (1997).</li><li>Kerr, C., Barker, D., Walsh, F., Archer, J. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=The+Electrodeposition+of+Composite+Coatings+based+on+Metal+Matrix-Included+Particle+Deposits.">The Electrodeposition of Composite Coatings based on Metal Matrix-Included Particle Deposits.</a> Transactions of the Institute of Metal Finishing. 78 (5), 171-178 (2000).</li><li>Walsh, F. C., Wang, S., Zhou, N. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=The+electrodeposition+of+composite+coatings:+Diversity,+applications+and+challenges.">The electrodeposition of composite coatings: Diversity, applications and challenges.</a> Current Opinion in Electrochemistry. 20, 8-19 (2020).</li><li>Feldstein, N. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Functional+coatings+comprising+light+emitting+particles.">Functional coatings comprising light emitting particles.</a> US Patent. , (1996).</li><li>Feldstein, N. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Composite+plated+articles+having+light-emitting+properties.">Composite plated articles having light-emitting properties.</a> US Patent. , (1998).</li><li>Zimmerman, E. 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Critical steps of electrostamping. Bathless electrostamping shares many of the same critical steps with traditional bath electroplating. These include proper cleaning of the electrodes, mixing metal ions into the electrolyte and applying and external or chemical (electroless plating) potential to cause reduction of metal onto the cathode. In addition, the oxidation of the anode and cathode should be avoided after acid activation by quickly rinsing with water and adding these electrodes to the setup.
...

Traditional electroplating is widely used to deposit thin films of a variety of metals, alloys, and metal-composites onto conductive surfaces to functionalize them for the intended application1,2,3,4,5,6,7,8,9,10,11,12. This method adds a metal finish to parts used in the manufacturing of aerospace, automotive, military, medical, and electronic equipment. &#173;&#173;&#173;&#173;The object to be plated, the cathode, is submerged in an aqueous bath containing metal salt precursors, which are reduced to metal at the surface of the object by the application of a chemical or electrical potential. Non-charged composite particles can be incorporated into the metal film by adding these to the bath during coating to enhance the film properties for increased hardness in the case of metal oxides and carbides, smoothness with polymers or lubrication with liquid oils12,13. However, because these particles lack an inherent attraction to the cathode, the ratio of composite that is incorporated into the metal remains low for bath plating13,14,15. This is especially problematic for large particles that do not adsorb to the cathode long enough to be embedded by the growing metal film. Additionally, hygroscopic particles solvate in aqueous solutions and their hydration shell acts as a physical barrier impeding contact with the cathode16.
Some promising methods have been shown to mitigate this effect by using dry non-polar solvents to remove the hydration barrier completely17, or by decorating the composite particles with charged surfactant molecules16 that disrupt the hydration shell to allow contact between the particle and the cathode. However, because these methods involve organic materials, carbon contamination is possible in the film and breakdown of these organic materials could occur at the electrodes. For example, the organic solvents used (DMSO2 and acetamide) are heated to 130 &#176;C in an inert atmosphere for air-free coating; however, we found them to be unstable during coating in air. Due to resistive heating at the electrodes, redox reactions with organic materials may result in impurities or sites for heterogeneous nucleation and growth of metal nanoparticles18. As a result, there is a need for an organic-free aqueous electroplating method that addresses the long-standing challenge of particle-cathode adsorption. So far, metal-composite bath coating has been shown to embed particles up to a few micrometers in diameter19 and as high as 15 % loading16,17.
In response to this, we describe an inorganic bathless electrostamping method that forces composite particles to become embedded into the film at high surface coverages despite their large size and hygroscopic nature20. By removing the bath, the process does not involve containers of hazardous coating liquids and the object to be plated does not need to be submerged. Therefore, large, cumbersome or otherwise corrosion- or water-sensitive objects, can be plated or &#8220;stamped&#8221; in select areas with the composite material. In addition, the removal of excess water requires less clean-up of liquid hazardous waste.
Here, we demonstrate this method to produce bright fluorescent metal films by co-depositing non-toxic and air-stable europium and dysprosium doped, strontium aluminate (87 &#177; 30 &#181;m) with nickel at high loadings (up to 80%). This comes in contrast to previous examples that were plated in a bath and therefore were limited to small (nanometers to a few micrometers) phosphors12. In addition, previously reported electrodeposited films fluoresce only under short-wave UV-light, with the exception of a recent report that grew 1 &#8211; 5 &#181;m luminescent strontium aluminate crystals in an alumina film with plasma electrolyte oxidation21. Fluorescent metal films could have far-reaching applications in many industries involving dim-light environments including road sign illumination21, aircraft maintenance equipment location and identification20, automobile and toy decorations, invisible messages, product authentication22, safety lighting, mechanochromic stress identification10 and tribological wear visual inspection12,16. Despite these potential uses for glowing metal surfaces, this method could also be expanded to include additional large and/or hygroscopic composite particles to produce a new variety of metal-composite functional coatings that were previously not possible via electroplating.

<table>
	<tbody>
		<tr>
			<td>37% M Hydrochloric Acid (aq)</td>
			<td>SigmaAldrich</td>
			<td>320331-500ML</td>
			<td>corrosive - handle in fume hood</td>
		</tr>
		<tr>
			<td>70% Nitric Acid (aq)</td>
			<td>SigmaAldrich</td>
			<td>438073-500ML</td>
			<td>corrosive - handle in fume hood</td>
		</tr>
		<tr>
			<td>Barium magnesium aluminate, europium doped (s)</td>
			<td>SigmaAldrich</td>
			<td>756512-25G</td>
			<td>fine powder</td>
		</tr>
		<tr>
			<td>Boric Acid (s)</td>
			<td>SigmaAldrich</td>
			<td>B6768-500G</td>
			<td>toxic</td>
		</tr>
		<tr>
			<td>Cotton Swab</td>
			<td>Q-tips</td>
			<td>Q-tips Cotton Swabs</td>
			<td></td>
		</tr>
		<tr>
			<td>ImageJ</td>
			<td>National Institutes of Health</td>
			<td>IJ 1.46r</td>
			<td>free software</td>
		</tr>
		<tr>
			<td>Nickel (II) chloride hexahydrate (s)</td>
			<td>SigmaAldrich</td>
			<td>223387-500G</td>
			<td>toxic</td>
		</tr>
		<tr>
			<td>Nickel (II) sulfate hexahydrate (s)</td>
			<td>SigmaAldrich</td>
			<td>227676-500G</td>
			<td>toxic</td>
		</tr>
		<tr>
			<td>Nickel foil (s)</td>
			<td>AliExpress</td>
			<td>Ni99.999</td>
			<td></td>
		</tr>
		<tr>
			<td>Nitrile gloves</td>
			<td>Fisher Scientific</td>
			<td>19-149-863B</td>
			<td></td>
		</tr>
		<tr>
			<td>nylon membrane (s)</td>
			<td>Tisch Scientific</td>
			<td>RS10133</td>
			<td></td>
		</tr>
		<tr>
			<td>Optical Microscope equipped with FTIC filter (470 &#177; 20 nm)</td>
			<td>Nikon</td>
			<td>Eclipse 80i</td>
			<td></td>
		</tr>
		<tr>
			<td>Plastic Wrap</td>
			<td>Fisher Scientific</td>
			<td>22-305654</td>
			<td></td>
		</tr>
		<tr>
			<td>Porcelain Mortar</td>
			<td>Fisher Scientific</td>
			<td>FB961A</td>
			<td></td>
		</tr>
		<tr>
			<td>Porcelain Pestle</td>
			<td>Fisher Scientific</td>
			<td>FB961K</td>
			<td></td>
		</tr>
		<tr>
			<td>Potassium Hydroxide (s)</td>
			<td>SigmaAldrich</td>
			<td>221473-25G</td>
			<td>corrosive</td>
		</tr>
		<tr>
			<td>Potentiostat with platinum wire</td>
			<td>Gamry Instruments</td>
			<td>1000E</td>
			<td></td>
		</tr>
		<tr>
			<td>Scoopula</td>
			<td>Fisher Scientific</td>
			<td>14-357Q</td>
			<td></td>
		</tr>
		<tr>
			<td>Spectrofluorometer</td>
			<td>Photon Technology International</td>
			<td>QM-40</td>
			<td></td>
		</tr>
		<tr>
			<td>Strontium aluminate, europium and dysprosium doped (s)</td>
			<td>GloNation</td>
			<td>756539-25G</td>
			<td>powder</td>
		</tr>
		<tr>
			<td>Variable linear DC power supply</td>
			<td>Tekpower</td>
			<td>TP3005T</td>
			<td></td>
		</tr>
		<tr>
			<td>Yttrium oxide, europium doped (s)</td>
			<td>SigmaAldrich</td>
			<td>756490-25G</td>
			<td>fine powder</td>
		</tr>
	</tbody>
</table>

localized bathless metal-composite plating via electrostamping

Composite plating with particles embedded into the metal matrix can enhance the properties of the metal coating to make it more or less conductive, hard, durable, lubricated or fluorescent. However, it can be more challenging than metal plating, because the composite particles are either 1) not charged so they do not have a strong electrostatic attraction to the cathode, 2) are hygroscopic and are blocked by a hydration shell, or 3) too large to remain stagnate at the cathode while stirring. Here, we describe the details of a bathless plating method that involves anode and cathode nickel plates sandwiching an aqueous concentrated electrolyte paste containing large hygroscopic phosphorescent particles and a hydrophilic membrane. After applying a potential, the nickel metal is deposited around the stagnant phosphor particles, trapping them in the film. The composite coatings are characterized by optical microscopy for film roughness, thickness and composite surface loading. In addition, fluorescence spectroscopy can be used to quantify the illumination brightness of these films to assess the effects of various current densities, coating duration and phosphor loading.

After following this protocol, a thin coating of metal should become plated onto the cathode surface and contain the composite particles that were added to the coating paste. Fluorescent or colored particle incorporation can be observed by visual inspection as a result of a change in appearance compared to the uncoated surface (Figure 1A1-A3). To investigate the percent surface coverage of the composite particles and to observe the surface morphology of the coating, optical ...

Watch this Scientific Journal Video about Localized Bathless Metal-Composite Plating via Electrostamping at JoVE.com

Localized Bathless Metal-Composite Plating via Electrostamping

Presented here is a protocol of bathless electroplating, where a stagnant metal salt paste containing composite particles are reduced to form metal composites at high loading. This method addresses the challenges faced by other common forms of electroplating (jet, brush, bath) of embedding composites particles into the metal matrix.

Composite plating with particles embedded into the metal matrix can enhance the properties of the metal coating to make it more or less conductive, hard, ...

Electro stamping works by trapping composite particles in the electrolyte, forcing them to plate with the metal. With this new technique, high composite particle loadings are possible even on water sensitive objects. Unlike typical electroplating, this technique does not require submerging the object in a liquid bath.Any conductive object, regardless of its size or shape. Can be coated with functional materials. Fluorescent metal composite coatings have far reaching applications for dim light environments including aircraft maintenance equipment location, road sign illumination and travel logical markings in mechanically machine parts.To begin weigh nickel sulfate, nickel chloride hexahydrate and boric acid as mentioned in the text manuscript and combine them in a vial together. Grind this salt mixture thoroughly to a fine powder. Make sure to use proper protective equipment, fume hoods and a hazardous waste disposal system.Next, Weigh 1.8 grams of europium dysprosium doped strontium aluminate, europium doped yttrium oxide or europium doped barium, magnesium aluminate and grind it into a fine powder using a porcelain mortar and pestle for approximately 10 minutes. Combine the ground composite powder with the salt mixture in a container for storage. Weigh 0.188 grams of this mixture per square centimeter of the coating area and add it to an open top container add 40 microliters of water per square centimeter of coating area to this mixture and stir to dissolve the salt and form a thick paste.Using a scissor, cut the anode to a size and shape that matches the object to be plated in order to remove organic material from the surface of the anode foil and the cathode clean it with 10 Mueller potassium hydroxide or sodium hydroxide using a cotton swab or cloth. Rinse the surface with water to remove the excess base then activate the metal surface to receive the coating by wiping it with a selective concentrated acid using a cotton swab or cloth, following the recommendations for activating specific metal surfaces and alloys. perform this in the fume hood to avoid exposure to hydrogen chloride vapors quickly deposit the prepared coating paste onto the cathode object, covering the entire area and making sure to avoid gaps.Activate the anode surface by wiping it with concentrated acid using a cotton swab or cloth. If calculation of current efficiency is required record the mass of the anode and cathode using an analytical balance. preset a power supply to the desired current or voltage mode.Cut a piece of a hydrophilic membrane such as a nylon sheet and place it on top of the anode coating paste to avoid direct contact with the cathode. Add a small amount of paste or dry salt mixture onto the sheet. Next, add two drops of water to partially dissolve the salt.This process makes the nylon sheet conductive to allow the mass transport of ions through the electrolyte which is necessary to balance charge in the coating reaction. This can also be accomplished by dipping the nylon membrane in an aqueous nickel salt mixture. Place the activated anode on top and attach both the negative and positive leads to the cathode object.Cover the entire system with plastic to help retain water and apply moderate pressure. Turn on the power supply and continue coating for a desired duration. Turn off the power supply and expose the system.Disconnect the leads and rinse the cathode object with water wash the other components of the system by soaking them in water and then discard this aqueous solution in the properly labeled hazardous waste container. To remove any uncoated composite particles gently rubbed the cathode object by hand wearing gloves. Record the mass of the anode and cathode using an analytical balance and calculate the difference with their original mass.Observe fluorescent coatings with an ultraviolet lamp to verify the brightness and consistency of the metal composite. Use chronopotentiometry to monitor changes in voltage under constant current and chronoamperometry to monitor changes in current under constant voltage. Turn on the potential stud and designate the duration and the applied current or voltage.prepare the coating as previously described. Normalize the voltage to a reference standard using a calibrated three electrode system. Place a platinum wire as a pseudo reference electrode between the anode and the nylon sheet.And to cover it with a separate nylon sheet to avoid contact. Deposit a few drops of water and a small amount of coating paste on the anode. Finally connect the leads to the electrodes then seal press and begin coating as described in the text manuscript.Monitor the changes in voltage or current. Fluorescent or colored particle incorporation can be observed due to a change in appearance compared to the uncoated surface. Optical microscopy was used to investigate the surface coverage and to observe the surface morphology of the coating.Samples were observed top-down or cut to reveal the cross section the percent composite particle surface coverage as a function of time for Chronoamperometry and as a function of current density for chronopotentiometry increases during coating. Surface coverage is also correlated with thickness. Coating parameters can be monitored under constant voltage using chronoamperometry and under constant current using chronopotentiometry The brightness of the metal composite coatings was quantified with fluorescent spectroscopy and the calculation for luminescence quantum yield was done using the ratios of the peak areas.When attempting this protocol, it is important to properly clean and activate the electrodes before coating. In addition, thoroughly grinding the precursor electrolyte mixture will help lead to a smooth even coating. The precursor composite electrolyte paste can also be deposited by spray coating or powder coating to save time and materials.This way objects can be coated at a larger scale. This new technique may stimulate scientific exploration to incorporate other large or hygroscopic composite particles which were previously incompatible with bath, jet or brush plating.

localized-bathless-metal-composite-plating-via-electrostamping

Research

JoVE Journal

Chemistry

Preparing Silica Aerogel Monoliths via a Rapid Supercritical Extraction Method

A procedure for the fabrication of monolithic silica aerogels in eight hours or less via a rapid supercritical extraction process is described. The procedure requires 15-20 min of preparation time, during which a liquid precursor mixture is prepared and poured into wells of a metal mold that is placed between the platens of a hydraulic hot press, followed by several hours of processing within the hot press. The precursor solution consists of a 1.0:12.0:3.6:3.5 x 10-3 molar ratio of tetramethylorthosilicate (TMOS):methanol:water:ammonia. In each well of the mold, a porous silica sol-gel matrix forms. As the temperature of the mold and its contents is increased, the pressure within the mold rises. After the temperature/pressure conditions surpass the supercritical point for the solvent within the pores of the matrix (in this case, a methanol/water mixture), the supercritical fluid is released, and monolithic aerogel remains within the wells of the mold. With the mold used in this procedure, cylindrical monoliths of 2.2 cm diameter and 1.9 cm height are produced. Aerogels formed by this rapid method have comparable properties (low bulk and skeletal density, high surface area, mesoporous morphology) to those prepared by other methods that involve either additional reaction steps or solvent extractions (lengthier processes that generate more chemical waste).The rapid supercritical extraction method can also be applied to the fabrication of aerogels based on other precursor recipes.

This article describes a rapid supercritical extraction method for fabricating silica aerogels. By utilizing a confined mold and hydraulic hot press, monolithic aerogels can be made in eight hours or less.

A procedure for the fabrication of monolithic silica aerogels in eight hours or less via a rapid supercritical extraction process is described. The ...

Fluorescence-based Monitoring of PAD4 Activity via a Pro-fluorescence Substrate Analog

Post-translational modifications may lead to altered protein functional states by increasing the covalent variations on the side chains of many protein substrates. The histone tails represent one of the most heavily modified stretches within all human proteins. Peptidyl-arginine deiminase 4 (PAD4) has been shown to convert arginine residues into the non-genetically encoded citrulline residue. Few assays described to date have been operationally facile with satisfactory sensitivity. Thus, the lack of adequate assays has likely contributed to the absence of potent non-covalent PAD4 inhibitors. Herein a novel fluorescence-based assay that allows for the monitoring of PAD4 activity is described. A pro-fluorescent substrate analog was designed to link PAD4 enzymatic activity to fluorescence liberation upon the addition of the protease trypsin. It was shown that the assay is compatible with high-throughput screening conditions and has a strong signal-to-noise ratio. Furthermore, the assay can also be performed with crude cell lysates containing over-expressed PAD4.

PAD4 is an enzyme responsible for the conversion of peptidyl-arginine to peptidyl-citrulline. Dysregulation of PAD4 has been implicated in a number of human diseases. A facile and high-throughput compatible fluorescence based PAD4 assay is described.

Post-translational modifications may lead to altered protein functional states by increasing the covalent variations on the side chains of many protein ...

Facile and Efficient Preparation of Tri-component Fluorescent Glycopolymers via RAFT-controlled Polymerization

Synthetic glycopolymers are instrumental and versatile tools used in various biochemical and biomedical research fields. An example of a facile and efficient synthesis of well-controlled fluorescent statistical glycopolymers using reversible addition-fragmentation chain-transfer (RAFT)-based polymerization is demonstrated. The synthesis starts with the preparation of &#946;-galactose-containing glycomonomer 2-lactobionamidoethyl methacrylamide obtained by reaction of lactobionolactone and N-(2-aminoethyl) methacrylamide (AEMA). 2-Gluconamidoethyl methacrylamide (GAEMA) is used as a structural analog lacking a terminal &#946;-galactoside. The following RAFT-mediated copolymerization reaction involves three different monomers: N-(2-hydroxyethyl) acrylamide as spacer, AEMA as target for further fluorescence labeling, and the glycomonomers. Tolerant of aqueous systems, the RAFT agent used in the reaction is (4-cyanopentanoic acid)-4-dithiobenzoate. Low dispersities (&#8804;1.32), predictable copolymer compositions, and high reproducibility of the polymerizations were observed among the products. Fluorescent polymers are obtained by modifying the glycopolymers with carboxyfluorescein succinimidyl ester targeting the primary amine functional groups on AEMA. Lectin-binding specificities of the resulting glycopolymers are verified by testing with corresponding agarose beads coated with specific glycoepitope recognizing lectins. Because of the ease of the synthesis, the tight control of the product compositions and the good reproducibility of the reaction, this protocol can be translated towards preparation of other RAFT-based glycopolymers with specific structures and compositions, as desired.

An efficient, three-step synthesis of RAFT-based fluorescent glycopolymers, consisting of glycomonomer preparation, copolymerization, and post-modification, is demonstrated. This protocol can be used to prepare RAFT-based statistical glycopolymers with desired structures.

Synthetic glycopolymers are instrumental and versatile tools used in various biochemical and biomedical research fields. An example of a facile and ...

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 ...

The Preparation and Properties of Thermo-reversibly Cross-linked Rubber Via Diels-Alder Chemistry

A method for using Diels Alder thermo-reversible chemistry as cross-linking tool for rubber products is demonstrated. In this work, a commercial ethylene-propylene rubber, grafted with maleic anhydride, is thermo-reversibly cross-linked in two steps. The pending anhydride moieties are first modified with furfurylamine to graft furan groups to the rubber backbone. These pendant furan groups are then cross-linked with a bis-maleimide via a Diels-Alder coupling reaction. Both reactions can be performed under a broad range of experimental conditions and can easily be applied on a large scale. The material properties of the resulting Diels-Alder cross-linked rubbers are similar to a peroxide-cured ethylene/propylene/diene rubber (EPDM) reference. The cross-links break at elevated temperatures (&#62; 150 &#176;C) via the retro-Diels-Alder reaction and can be reformed by thermal annealing at lower temperatures (50-70 &#176;C). Reversibility of the system was proven with infrared spectroscopy, solubility tests and mechanical properties. Recyclability of the material was also shown in a practical way, i.e., by cutting a cross-linked sample into small parts and compression molding them into new samples displaying comparable mechanical properties, which is not possible for conventionally cross-linked rubbers.

A simple two-step approach involving rubber modification and cross-linking yields fully reworkable, elastic rubber products.

A method for using Diels Alder thermo-reversible chemistry as cross-linking tool for rubber products is demonstrated. In this work, a commercial ...

Synthesizing Sodium Tungstate and Sodium Molybdate Microcapsules via Bacterial Mineral Excretion

We present a method, the bacterial mineral excretion (BME), for synthesizing two kinds of microcapsules, sodium tungstate and sodium molybdate, and the two metal oxides&#39; corresponding nanoparticles&#8212;the former being as small as 22 nm and the latter 15 nm. We fed two strains of bacteria, Shewanella algae and Pandoraea sp., with various concentrations of tungstate or molybdate ions. The concentrations of tungstate and molybdate were adjusted to make microcapsules of different length-to-diameter ratios. We found that the higher the concentration the smaller the nanoparticles were. The nanoparticles came in with three length-to-diameter ratios: 10:1, 3:1 and 1:1, which were achieved by feeding the bacteria respectively with a low concentration, a medium concentration, and a high concentration. The images of the hollow microcapsules were taken via the scanning electron microsphere (SEM). Their crystal structures were verified by X-ray diffraction (XRD)&#8212;the crystal structure of molybdate microcapsules is Na2MoO4 and that of tungstate microcapsules is Na2WO4 with Na2W2O7. These syntheses all were accomplished under a near ambient condition.

This work presents a protocol for manufacture sodium tungstate and sodium molybdate microcapsules via bacteria and their corresponding nanoparticles.

We present a method, the bacterial mineral excretion (BME), for synthesizing two kinds of microcapsules, sodium tungstate and sodium molybdate, and the ...

Fabrication and Testing of Catalytic Aerogels Prepared Via Rapid Supercritical Extraction

Protocols for preparing and testing catalytic aerogels by incorporating metal species into silica and alumina aerogel platforms are presented. Three preparation methods are described: (a) the incorporation of metal salts into silica or alumina wet gels using an impregnation method; (b) the incorporation of metal salts into alumina wet gels using a co-precursor method; and (c) the addition of metal nanoparticles directly into a silica aerogel precursor mixture. The methods utilize a hydraulic hot press, which allows for rapid (&#60;6 h) supercritical extraction and results in aerogels of low density (0.10 g/mL) and high surface area (200-800 m2/g). While the work presented here focuses on the use of copper salts and copper nanoparticles, the approach can be implemented using other metal salts and nanoparticles. A protocol for testing the three-way catalytic ability of these aerogels for automotive pollution mitigation is also presented. This technique uses custom-built equipment, the Union Catalytic Testbed (UCAT), in which a simulated exhaust mixture is passed over an aerogel sample at a controlled temperature and flow rate. The system is capable of measuring the ability of the catalytic aerogels, under both oxidizing and reducing conditions, to convert CO, NO and unburned hydrocarbons (HCs) to less harmful species (CO2, H2O and N2). Example catalytic results are presented for the aerogels described.

Here we present protocols for preparing and testing catalytic aerogels by incorporating metal species into silica and alumina aerogel platforms. Methods for preparing materials using copper salts and copper-containing nanoparticles are featured. Catalytic testing protocols demonstrate the effectiveness of these aerogels for three-way catalysis applications.

Protocols for preparing and testing catalytic aerogels by incorporating metal species into silica and alumina aerogel platforms are presented. Three ...

Membrane Remodeling of Giant Vesicles in Response to Localized Calcium Ion Gradients

In a wide variety of fundamental cell processes, such as membrane trafficking and apoptosis, cell membrane shape transitions occur concurrently with local variations in calcium ion concentration. The main molecular components involved in these processes have been identified; however, the specific interplay between calcium ion gradients and the lipids within the cell membrane is far less known, mainly due to the complex nature of biological cells and the difficultly of observation schemes. To bridge this gap, a synthetic approach is successfully implemented to reveal the localized effect of calcium ions on cell membrane mimics. Establishing a mimic to resemble the conditions within a cell is a severalfold problem. First, an adequate biomimetic model with appropriate dimensions and membrane composition is required to capture the physical properties of cells. Second, a micromanipulation setup is needed to deliver a small amount of calcium ions to a particular membrane location. Finally, an observation scheme is required to detect and record the response of the lipid membrane to the external stimulation. This article offers a detailed biomimetic approach for studying the calcium ion-membrane interaction, where a lipid vesicle system, consisting of a giant unilamellar vesicle (GUV) connected to a multilamellar vesicle (MLV), is exposed to a localized calcium gradient formed using a microinjection system. The dynamics of the ionic influence on the membrane were observed using fluorescence microscopy and recorded at video frame rates. As a result of the membrane stimulation, highly curved membrane tubular protrusions (MTPs) formed inside the GUV, oriented away from the membrane. The described approach induces the remodeling of the lipid membrane and MTP production in an entirely contactless and controlled manner. This approach introduces a means to address the details of calcium ion-membrane interactions, providing new avenues to study the mechanisms of cell membrane reshaping.

We present a technique for contactless micromanipulation of vesicles, using localized calcium ion gradients. Microinjection of a calcium ion solution, in the vicinity of a giant lipid vesicle, is utilized to remodel the lipid membrane, resulting in the production of membrane tubular protrusions.

In a wide variety of fundamental cell processes, such as membrane trafficking and apoptosis, cell membrane shape transitions occur concurrently with local ...

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.