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 g of H3BO3 and combine in a vial together. See Table 1 for concentrations.</li>
	<li>Weigh out 1.800 g of SrAl2O4:Eu2+, Dy3+ phosphor or alternative phosphors including europium doped yttrium oxide, europium doped barium magnesium aluminate, or replace with alternative oxide, metal, or organic composite material depending on the desired effect. 
	NOTE: The amount added here may vary based on the properties of the composite material and the desired qualities of the metal-composite film.</li>
	<li>Using a porcelain mortar and pestle, grind the composite powder for approximately 10 minutes until it becomes a fine powder. 
	NOTE: This does not change the particle size, but does separate aggregated particles.</li>
	<li>Likewise, grind the salt mixture from step 1.1 in batches until it becomes a fine powder.</li>
	<li>Combine the ground phosphor with the ground salt mixture in a container for storage.</li>
	<li>Weigh out 0.188 grams of the mixture per cm2 of coating area, as prepared in step 1.5 and add to a container with an open top that is easy to access.</li>
	<li>To this, add 40 &#181;L of water per cm2 of coating area, and stir to partially dissolve the salts forming a thick paste. Set this aside. 
	NOTE: The protocol can be paused here.</li>
</ol>
2. Preparing the electrodes
<ol>
	<li>Using scissors, cut the anode to the size and shape that matches the object to be plated. In this example, we prepare a 4 cm2 nickel foil to be coated, and a 4 cm2 nickel anode is cut to match this. 
	NOTE: Other objects can be coated including large objects. In this case, select the area on the object to be coated, and cut out the anode to match the coating area.</li>
	<li>Using a cotton swab or a cloth, clean the surface of the anode foil and the cathode (coating object surface) with concentrated (10 M) potassium hydroxide or sodium hydroxide base to remove organic material. Next, rinse the surfaces with water to remove excess base.</li>
	<li>Using a cotton swab or a cloth, activate the object surface with concentrated acid. In the case of nickel, 37% vol/vol HCl is used, although for steel, 10% by volume aqueous HCl may be more appropriate. Please refer to the recommendations for activating metal surfaces provided elsewhere to determine the appropriate method for activating specific metals or alloys23,24. 
	NOTE: After this step, the metal surface is reactive and the surface will start to react with oxygen in the air to form an oxide layer. This will cause the surface to be inactive, so the following steps (2.4 &#8211; 3.5) should be performed in the next 5 minutes; otherwise, step 2.3 should be repeated before continuing. 
	CAUTION: This step should be performed in a fume hood to avoid exposure to HCl vapors.</li>
	<li>Quickly, deposit the coating paste onto the cathode object. In this case, the cathode is a 4 cm2 nickel foil on the benchtop. Cover the object area to be plated evenly and try to avoid gaps in the paste. 
	NOTE: In this example, we are painting on this paste with two scoopulas, however, other options may include spraying, dipping or doctor blading to increase the speed and efficiency of this step.</li>
	<li>Using a cotton swab or a cloth, activate the anode with concentrated acid by dipping the swab in the acid and gently rubbing the cathode surface. In the case of nickel, 70% vol/vol HNO3 can be used. 
	NOTE: However, other acids may be more appropriate for specific metals and alloys. Please refer to the recommendations provided elsewhere for the appropriate reagent to activate specific anode surfaces23,24. 
	CAUTION: This step should be performed in a fume hood to avoid exposure to NO2, a toxic brown gas that is formed during the reaction. Continue treating the surface until the surface becomes grey and textured. After this step, the metal surface is reactive and the surface will start to react with oxygen in the air to form an oxide layer, so the following steps should be performed quickly to avoid inactivation of the anode.</li>
	<li>If calculating the current efficiency is desired, use an analytical balance to record the mass of the anode and the cathode.</li>
</ol>
3. Assembly and coating
<ol>
	<li>Pre-set a power supply to the desired current in constant current mode or voltage, if constant voltage mode is desired. In this example, constant current mode is used with a current of 0.1 Amperes (0.1 A per 4 cm2 = 0.025 A/cm2). 
	NOTE: For larger or irregularly shaped objects, the coating area can be predetermined with a grid or using a photo with scale bar and an imaging software like ImageJ. The applied current can be scaled to deliver the same current density required for the coating area.</li>
	<li>Cut a piece of nylon sheet (or alternative hydrophilic membrane) to a size larger than the anode so that the anode does not make direct contact with the cathode object.
	<ol>
		<li>Place the nylon sheet on top of the coating paste, and then add a small amount of paste to this.</li>
	</ol>
	</li>
	<li>Next, add 1-2 drops of water from a pipette to allow the salt to partially dissolve. Steps 3.2.1 &#8211; 3.3 make the nylon sheet conductive and allow for the mass transport of ions through the electrolyte, which is necessary to balance charge in the coating reaction.</li>
	<li>Finally, add the activated anode on top and attach the negative lead to the cathode object and the positive lead to the anode. 
	NOTE: It might be helpful to tape down these leads so that the setup remains stationary, especially if the experiment involves small pieces of metal foil. This is less important for large objects.</li>
	<li>Cover the system with plastic or seal to help retain water, and apply moderate pressure (~100 g per cm2 area), turn on the power supply and continue coating for the desired duration.</li>
	<li>Turn off the power supply and expose the system.</li>
	<li>Disconnect the leads, separate the electrodes and rinse the cathode object with water into a waste container.
	<ol>
		<li>Soak the other items in water to remove salts and dispose of this aqueous solution in the properly labeled hazardous waste container</li>
		<li>Wearing gloves, gently rub the cathode object by hand to remove any uncoated composite particles. The coating is complete and ready for characterization.</li>
		<li>Using an analytical balance, record the mass of the anode and the cathode and find the difference between these values and their original mass.</li>
		<li>Use Faraday&#8217;s Laws of electrolysis to calculate the current efficiency. The theoretical moles of metal coating can be determined using Equation 1. 
		<img alt="Equation 1" src="/files/ftp_upload/61484/61484equ01.jpg" />&#160; &#160; Equation 1 
		where n is the amount of metal deposited (units: mol), I is the applied current, t is the coating time, F is Faraday&#8217;s constant (96485 coulombs per mole) and z is the charge of the metal ion. Calculate this value based on the experimental parameters.</li>
		<li>Divide the experimentally determined deposit mass obtained from the masses of the cathode or anode (Steps 2.6 and 3.7.3) by the theoretical mass lost (anode) or gained (cathode) to calculate the current efficiency using Equation 2. 
		<img alt="Equation 2" src="/files/ftp_upload/61484/61484equ02.jpg" />&#160; &#160; Equation 2 
		[NOTE: At a current efficiency of 100%, under constant voltage, a theoretical deposit mass is expected of approximately 1.095 g of nickel or 12.3 &#181;m of nickel per hour, given 0.04 A and 4 cm2 area. Likewise, under constant current, approximately 614.6 &#181;m nickel would theoretically deposit per unit of 1 A&#8729;cm-2 after 30 min.]</li>
	</ol>
	</li>
</ol>
4. Characterization with electrochemistry
<ol>
	<li>Use chronopotentiometry to monitor changes in voltage under constant current, and chronoamperometry to monitor changes in current under constant voltage.
	<ol>
		<li>Turn on the potentiostat and designate the duration and the applied current or voltage.</li>
		<li>Repeat steps 3.2 &#8211; 3.5 to prepare the coating.</li>
		<li>Use a calibrated 3-electrode system to normalize the voltage to a reference standard.
		<ol>
			<li>Place a platinum wire pseudo reference electrode between on top of the nylon sheet and below the anode. In order to ensure that the reference electrode does not make direct contact with the anode, use a separate nylon sheet (or alternative membrane) placed on top of the reference followed by a few drops of water, a small amount of coating paste (repeat steps 3.2 &#8211; 3.3) and then the anode.</li>
		</ol>
		</li>
		<li>Connect the leads to the electrodes, seal, press, begin coating and monitor changes in voltage or current.</li>
	</ol>
	</li>
</ol>
5. Characterization with quantum yield fluorescence spectroscopy
<ol>
	<li>If the coating contains fluorescent composite particles, use a fluorometer equipped with an integrating sphere to obtain absolute quantum yield measurements.
	<ol>
		<li>Place the coating into the fluorimeter stage with the fluorescent coating facing 45&#176; from the excitation source and 315&#176; from the detector.</li>
		<li>Record the fluorescence spectra starting at a wavelength below the excitation wavelength to record the areas of the excitation peak and the fluorescence peak.</li>
		<li>Remove the sample from the fluorometer, and repeat step 5.1.2 to record the blank excitation peak. Calculate the quantum yield (QY) from the ratios of the areas of the excitation and emission peaks (Equation 3 and Figure 3B). 
		<img alt="Equation 3" src="/files/ftp_upload/61484/61484equ03.jpg" />&#160; &#160; Equation 3 
		where Aem, Aex and Ao are the peak areas at the emission wavelength of the sample, the excitation wavelength of the sample and the excitation wavelength of the blank, respectively.</li>
	</ol>
	</li>
</ol>
6. Characterization with optical microscopy
<ol>
	<li>Place the sample on the stage of a calibrated optical microscope with the coating side facing the lenses and bring the surface into focus.</li>
	<li>Record surface images at the desired magnifications and surface sample sites.</li>
	<li>Using image analysis software (ex. ImageJ (IJ 1.46r)), calculate and plot the surface coverage and average composite particle size.</li>
	<li>To determine coating thickness and cross-section features, cut the cathode foil with scissors. Set the coating on the side and re-adjust the focus. Repeat steps 6.2 &#8211; 6.3.</li>
</ol>

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The authors have nothing to disclose.

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, ...

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

Research

JoVE Journal

Chemistry

4.1K Views.  St. Mary's College of Maryland. 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.

Video: Localized Bathless Metal-Composite Plating via Electrostamping

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 ...

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.

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

A Two-Step Protocol for Umpolung Functionalization of Ketones Via Enolonium Species

&#945;-Functionalization of ketones via umpolung of enolates by hypervalent iodine reagents is an important concept in synthetic organic chemistry. Recently, we have developed a two-step strategy for ketone enolate umpolung that has enabled the development of methods for chlorination, azidation, and amination using azoles. In addition, we have developed C-C bond&#8211;forming arylation and allylation reactions. At the heart of these methods is the preparation of the intermediate and highly reactive enolonium species prior to addition of a reactive nucleophile. This strategy is thus reminiscent of the preparation and use of metal enolates in classical synthetic chemistry. This strategy allows the use of nucleophiles that would otherwise be incompatible with the strongly oxidizing hypervalent iodine reagents. In this paper we present a detailed protocol for chlorination, azidation, N-heteroarylation, arylation, and allylation. The products include motifs prevalent in medicinally active products. This article will greatly assist others in using these methods.

A two step one-pot protocol for the umpolung of ketone enolates to enolonium species and addition of a nucleophile to the &#945;-position is described. Nucleophiles include chloride, azide, azoles, allyl-silanes, and aromatic compounds.

&#945;-Functionalization of ketones via umpolung of enolates by hypervalent iodine reagents is an important concept in synthetic organic chemistry. ...