This research was supported by National Science Foundation (CCF 1814797) and University of Missouri Research Board, Material Research Center, and the College of Arts and Science at Missouri University of Science and Technology

1 . Preparation of Reagents
CAUTION: Please read and understand all relevant material safety data sheets (MSDS) before use. Some of the chemicals are toxic and volatile. Please follow special handling procedures and storage requirements. During the experimental procedure, use personal protective equipment, such as gloves, safety glasses, and a lab coat to avoid potential hazards.
<ol>
	<li>Preparation of Tris-HCl buffer
	<ol>
		<li>Dissolve 30.29 g of Tris powder in 100 mL of deionized H<sub...

<ol>
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M., Miller, W. M., Messersmith, P. B. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Mussel-inspired+surface+chemistry+for+multifunctional+coatings.">Mussel-inspired surface chemistry for multifunctional coatings.</a> Science. 318 (5849), 426-430 (2007).</li><li>Wang, C., Zhou, J., Wang, P., He, W., Duan, H. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Robust+Nanoparticle-DNA+Conjugates+Based+on+Mussel-Inspired+Polydopamine+Coating+for+Cell+Imaging+and+Tailored+Self-Assembly.">Robust Nanoparticle-DNA Conjugates Based on Mussel-Inspired Polydopamine Coating for Cell Imaging and Tailored Self-Assembly.</a> Bioconjugate Chemistry. 27 (3), 815-823 (2016).</li><li>Liu, R., Guo, Y., Odusote, G., Qu, F., Priestley, R. D. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Core-shell+Fe3O4+polydopamine+nanoparticles+serve+multipurpose+as+drug+carrier,+catalyst+support+and+carbon+adsorbent.">Core-shell Fe3O4 polydopamine nanoparticles serve multipurpose as drug carrier, catalyst support and carbon adsorbent.</a> ACS Applied Materials and Interfaces. 5 (18), 9167-9171 (2013).</li><li>Liu, 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=Dopamine+as+a+Carbon+Source:+The+Controlled+Synthesis+of+Hollow+Carbon+Spheres+and+Yolk-Structured+Carbon+Nanocomposites.">Dopamine as a Carbon Source: The Controlled Synthesis of Hollow Carbon Spheres and Yolk-Structured Carbon Nanocomposites.</a> Angewandte Chemie International Edition. 50 (30), 6799-6802 (2011).</li><li>Zeng, Y., Liu, W., Wang, Z., Singamaneni, S., Wang, R. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Multifunctional+surface+modification+of+nanodiamonds+based+on+dopamine+polymerization.">Multifunctional surface modification of nanodiamonds based on dopamine polymerization.</a> Langmuir. 34 (13), 4036-4042 (2018).</li><li>Qin, S., 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=Dopamine@Nanodiamond+as+novel+reinforcing+nanofillers+for+polyimide+with+enhanced+thermal,+mechanical+and+wear+resistance+performance.">Dopamine@Nanodiamond as novel reinforcing nanofillers for polyimide with enhanced thermal, mechanical and wear resistance performance.</a> RSC Advances. 8 (7), 3694-3704 (2018).</li><li>Barras, A., Lyskawa, J., Szunerits, S., Woisel, P., Boukherroub, R. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Direct+functionalization+of+nanodiamond+particles+using+dopamine+derivatives.">Direct functionalization of nanodiamond particles using dopamine derivatives.</a> Langmuir. 27 (20), 12451-12557 (2011).</li><li>Khanal, 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=Toward+Multifunctional+"Clickable"+Diamond+Nanoparticles.">Toward Multifunctional "Clickable" Diamond Nanoparticles.</a> Langmuir. 31 (13), 3926-3933 (2015).</li><li>Rad, M. H., Zamanian, A., Hadavi, S. M. M., Khanlarkhani, A. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=A+Two-Stage+Kinetics+Model+for+Polydopamine+Layer+Growth.+A+Two-Stage+Kinetics+Model+for+Polydopamine+Layer+Growth.">A Two-Stage Kinetics Model for Polydopamine Layer Growth. A Two-Stage Kinetics Model for Polydopamine Layer Growth.</a> Macromolecular Chemistry and Physics. , 1700505 (2018).</li><li>Ball, V., Frari, D. D., Toniazzo, V., Ruch, D. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Kinetics+of+polydopamine+film+deposition+as+a+function+of+pH+and+dopamine+concentration:+Insights+in+the+polydopamine+deposition+mechanism.">Kinetics of polydopamine film deposition as a function of pH and dopamine concentration: Insights in the polydopamine deposition mechanism.</a> Journal of Colloid and Interface Science. 386 (1), 366-372 (2012).</li><li>Liu, Y., Ai, K., Lu, L. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Polydopamine+and+its+derivative+materials:+synthesis+and+promising+applications+in+energy,+environmental,+and+biomedical+fields.">Polydopamine and its derivative materials: synthesis and promising applications in energy, environmental, and biomedical fields.</a> Chemical Reviews. 114 (9), 5057-5115 (2014).</li><li>Hu, J., Wu, S., Cao, Q., Zhang, W. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Synthesis+of+core-shell+structured+alumina/Cu+microspheres+using+activation+by+silver+nanoparticles+deposited+on+polydopamine-coated+surfaces.">Synthesis of core-shell structured alumina/Cu microspheres using activation by silver nanoparticles deposited on polydopamine-coated surfaces.</a> RSC Advances. 6 (85), 81767-81773 (2016).</li><li>Orishchin, N., 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=Rapid+Deposition+of+Uniform+Polydopamine+Coatings+on+Nanoparticle+Surfaces+with+Controllable+Thickness.">Rapid Deposition of Uniform Polydopamine Coatings on Nanoparticle Surfaces with Controllable Thickness.</a> Langmuir. 33, 6046-6053 (2017).</li><li>Gonza&#769;lez, A. 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This article provides a detailed protocol for the surface functionalization of NDs with self-polymerized DA coating, and the reduction of Ag[(NH3)2]+ to AgNPs on PDA layers (Figure 3). The strategy is capable of producing various thicknesses of PDA layers by simply changing the concentration of DA. The size of the AgNPs can also be controlled by altering the original concentration of metal ion solution. The TEM image in Figure 1<...

Nanodiamonds (NDs), a novel carbon-based material, have attracted considerable attention in recent years for use in various applications1,2. For instance, the high surface areas of NDs provide excellent catalyst support for metal nanoparticles (NPs) because of their super-chemical stability and thermal conductivity3. Furthermore, NDs play significant roles in bio-imaging, bio-sensing, and drug delivery due to their outstanding biocompatibility and nontoxicity4,5.
To efficiently extend their capabilities, it is valuable to conjugate functional species on the surfaces of NDs, such as proteins, nucleic acids, and nanoparticles6. Although a variety of functional groups (e.g., hydroxyl, carboxyl, lactone, etc.) are created on the surfaces of NDs during their purification, the conjugation yields of the functional groups are still very low because of the low density of each active chemical group7. This results in unstable NDs, which tend to aggregate, limiting further application8.
Currently, the most common methods used to functionalize NDs, are covalent conjugation by using copper-free click chemistry9, covalent linkage of peptide nucleic acids (PNA)10, and self-assembled DNA11. The non-covalent wrapping of NDs has also been proposed, including carbohydrate-modified BSA4, and HSA12coating. However, because these methods are time consuming and inefficient, it is desirable that a simple and generally applicable method can be developed to modify the surfaces of NDs.
Dopamine (DA)13, known as a natural neurotransmitter in the brain, was widely used for adhering and functionalizing nanoparticles, such as gold nanoparticles (AuNPs)14, Fe2O315, and SiO216. Self-polymerized PDA layers enrich amino and phenolic groups, which can be further utilized to directly reduce metal nanoparticles or to easily immobilize thiol/amine-containing biomolecules on an aqueous solution. This simple approach was recently applied to functionalize NDs by Qin et al. and our laboratory17,18, although DA derivatives were employed to modify NDs via Click Chemistry in earlier studies19,20.
Here, we describe a simple PDA-based surface modification method that efficiently functionalizes NDs. By varying the concentration of DA, we can control the thickness of a PDA layer from a few nanometers to tens of nanometers. In addition, the metal nanoparticles are directly reduced and stabilized on the PDA surface without the need for additional toxic reduction agents. The sizes of the silver nanoparticles depend on the initial concentrations of Ag[(NH3)2]+. This method allows the well-controlled deposition of PDA on the surfaces of NDs and the synthesis of ND conjugated AgNPs, which dramatically extends the functionality of NDs as excellent nano-platforms of catalyst supports, bio-imaging, and bio-sensors.

<table border="0" cellpadding="0" cellspacing="0" style="width:839px;" width="838">
	<colgroup>
		<col />
		<col />
		<col />
		<col />
	</colgroup>
	<tbody>
		<tr height="21">
			<td height="21" style="height:21px;width:216px;">Nanodiamond</td>
			<td style="width:121px;">FND Biotech, Inc.</td>
			<td style="width:136px;">brFND-100</td>
			<td style="width:365px;">dispersed in water, and used without further purification</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:216px;">Dopamine hydrochloride</td>
			<td style="width:121px;">Sigma</td>
			<td style="width:136px;">H8502-25G</td>
			<td>prepare freshly</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:216px;">Silver Nitrate</td>
			<td style="width:121px;">Fisher</td>
			<td style="width:136px;">S181-25</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:216px;">Ammonium Hydroxide</td>
			<td style="width:121px;">Fisher</td>
			<td style="width:136px;">A669S-500</td>
			<td>highly toxic</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:216px;">Tris Hydrochloride</td>
			<td style="width:121px;">Fisher</td>
			<td style="width:136px;">BP153-500</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:216px;">TEM grid carbon film</td>
			<td style="width:121px;">Ted Pella</td>
			<td style="width:136px;">01843-F</td>
			<td>300 mesh copper</td>
		</tr>
	</tbody>
</table>

bio-inspired polydopamine surface modification of nanodiamonds and its reduction of silver nanoparticles

Surface functionalization of nanodiamonds (NDs) is still challenging due to the diversity of functional groups on the ND surfaces. Here, we demonstrate a simple protocol for the multifunctional surface modification of NDs by using mussel-inspired polydopamine (PDA) coating. In addition, the functional layer of PDA on NDs could serve as a reducing agent to synthesize and stabilize metal nanoparticles. Dopamine (DA) can self-polymerize and spontaneously form PDA layers on ND surfaces if the NDs and dopamine are simply mixed together. The thickness of a PDA layer is controlled by varying the concentration of DA. A typical result shows that a thickness of ~5 to ~15 nm of the PDA layer can be reached by adding 50 to 100 &#181;g/mL of DA to 100 nm ND suspensions. Furthermore, the PDA-NDs are used as a substrate to reduce metal ions, such as Ag[(NH3)2]+, to silver nanoparticles (AgNPs). The sizes of the AgNPs rely on the initial concentrations of Ag[(NH3)2]+. Along with an increase in the concentration of Ag[(NH3)2]+, the number of NPs increases, as well as the diameters of the NPs. In summary, this study not only presents a facile method for modifying the surfaces of NDs with PDA, but also demonstrates the enhanced functionality of NDs by anchoring various species of interest (such as AgNPs) for advanced applications.

The formation of PDA layers on ND surfaces were analyzed by TEM (Figure 1). Different thicknesses of PDA layers were observed as higher concentrations of DA led to thicker PDA layers. In addition, after an encapsulating reaction, the color of the NDs solution changed from colorless to dark, while the higher the initial concentration of DA was, the darker the solution became.
Fig...

Watch this Scientific Journal Video about Bio-inspired Polydopamine Surface Modification of Nanodiamonds and Its Reduction of Silver Nanoparticles at JoVE.com

Bio-inspired Polydopamine Surface Modification of Nanodiamonds and Its Reduction of Silver Nanoparticles

A facile protocol is presented to functionalize the surfaces of nanodiamonds with polydopamine.

Surface functionalization of nanodiamonds (NDs) is still challenging due to the diversity of functional groups on the ND surfaces. Here, we demonstrate a ...

This method can help answer key questions about effective surface functionalization of nanodiamond, which have broad applications in material science and biomedicine. This method can be used for nanodiamonds. It can also be applied for other materials, such as metal nanoparticles, magnetic nanoparticles, or surfaces that need an active biopolymer coating.In this method, nanodiamonds are funtionalized with a coating of polydopamine, a universal adhesive. The thickness of the PDA layer is well controlled by varying the concentration of dopamine. To begin, dissolve 30.29 grams of tris HCl powder in 100 microliters of deionized water.Transfer the solution to a 250 milliliter volumetric flask. Fill the flask to the line with deionized water, and mix it to obtain a one molar tris HCl buffer. From this stock solution, prepare 20 milliliters of 0.1 molar tris HCl buffer by serial dilution.While monitoring the buffer with a pH meter, adjust the pH to 8.5 using one molar hydrochloric acid. Next, dilute 0.02 milliliters of a one milligram per milliliter suspension of 100 nanometer monocrystalline nanodiamonds to one milliliter with the pH 8.5 tris buffer. Stir the mixture for 10 minutes to obtain a 0.02 milligram per milliliter nanodiamond suspension.Then, dissolve 20 milligrams of dopamine hydrochloride in two milliliters of pH 8.5 tris buffer, by vortexing for 30 seconds to obtain a buffered 10 milligram per milliliter dopamine hydrochloride solution. Add five, 7.5, or 10 microliters of the freshly prepared dopamine solution to the nanodiamond solution, depending on whether a final dopamine hydrochloride concentration of 50, 75, or 100 milligram per milliliter is desired. After adjusting the reaction volume, vigorously stir the mixture at 25 degrees Celsius for 12 hours in the dark.Then, transfer the suspension of polydopamine-coated nanodiamonds to a 1.5 milliliter centrifuge tube, and centrifuge it at 16, 000 g for two hours. Remove the supernatant and wash the nanodiamonds three times with one milliliter portions of deionized water at 16, 000 g for one hour each time. Then add 200 microliters of deionized water to the washed solids, and sonicate the mixture for 30 seconds to redisperse the polydopamine-coated nanodiamonds.Serially dilute 40 microliters of a suspension of polydopamine-coated nanodiamonds twice with deionized water. Then, dissolve 100 milligrams of silver nitrate in 10 milliliters of deionized water by vortexing. In a fume hood, add one molar aqueous ammonia to the silver nitrate solution, dropwise, until a yellow precipitate forms, periodically shaking the solution.Continue adding ammonia until the precipitate disappears to obtain a solution of diamine silver hydroxide. Immediately add either 4.3 or 6.4 microliters of the diamine silver solution to 40 microliters of the diluted nanodiamond dispersion, for a final concentration of 0.4 or 0.6 milligrams per milliliter respectively. After this, adjust the volume to 100 microliters with deionized water.Sonicate the mixture for 10 minutes. Then, centrifuge the dispersion for 15 minutes at 16, 000 g to remove free silver ions. Discard the supernatant and wash the silver nanoparticle-decorated polydopamine-coated nanodiamonds by centrifuging them three times in 100 microliter portions of deionized water at 16, 000 g for five minutes each time.Add 100 microliters of deionized water to the silver nanoparticle-decorated nanodiamonds and redisperse them by sonication for 30 seconds. Characterize the nanodiamonds with UV-Vis spectroscopy scanning from 250 to 550 nanometers. Next, deposit five microliters of the silver nanoparticle-decorated nanodiamonds on plasma-cleaned carbon-coated copper grids, and let them sit for three minutes.Then, wick away excess solution with filter paper. Wash each grid three times by applying a drop of deionized water, letting it sit for 15 seconds, and then wicking it away with filter paper. Let the grids air dry before visualizing the samples with transmission electron microscopy.The uncoated nanodiamonds tended to form microclusters and aggregates, while polydopamine-coated nanodiamonds formed good dispersions. Higher dopamine concentrations resulted in the formation of thicker polydopamine layers in the nanodiamond surfaces. The uncoated nanodiamond dispersion was clear and colorless.Upon coating the nanodiamonds with a five nanometer thick polydopamine layer, the dispersion appeared cloudy and brown. The dispersion appearance became progressively darker with thicker polydopamine coatings. The reduction of diamine silver on nanodiamonds coated with a 15 nanometer thick polydopamine layer was most successful when the diamine silver hydroxide concentration was 0.4 to 0.6 milligrams per milliliter.The nanodiamonds formed at lower concentrations were too small to be studied effectively. The maximum absorbance values indicated that the nanoparticles formed from the 0.4 to 0.6 milligram per milliliter solutions had diameters of roughly 20 and 30 nanometers respectively. TEM showed that the silver nanoparticles generated from the 0.4 milligram per milliliter diamine silver solution were about 24 nanometers wide, while the nanoparticles generated from the 0.6 milligram per milliliter solution were about 28 nanometers wide.The number of nanoparticles on the nanodiamond surfaces was also greater at the higher diamine silver concentration. After using this procedure, well-dispersed nanodiamonds with a controllable PDA thickness were formed. This technique paves the way for researchers to explore nanodiamond applications for catalyst, biosensors, and nanocarriers.Without using any additional reducing agent, the PDA-assisted materialization process can induce the formation of silver nanoparticles upon the reduction of metal precursors and immobilize them on the PDA-coated surface. In addition, the PDA layers contain open functional groups which can be further utilized to conjugate serial and amine-modified biomolecules.

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JoVE Journal

Chemistry

8.0K ビュー.  Missouri University of Science and Technology. この方法は、材料科学と生物医学に幅広い応用を有するナノダイヤモンドの効果的な表面機能化に関する重要な質問に答える助けとなる。この方法はナノダイヤモンドに使用できます。また、金属ナノ粒子、磁性ナノ粒子、または活性バイオポリマーコーティングを必要とする表面などの他の材料にも適用できます。この方法では、ナノダイヤモンドは、普遍的な?...

ビデオ: Bio-inspired Polydopamine Surface Modification of Nanodiamonds and Its Reduction of Silver Nanoparticles

A Method to Manipulate Surface Tension of a Liquid Metal via Surface Oxidation and Reduction

Controlling interfacial tension is an effective method for manipulating the shape, position, and flow of fluids at sub-millimeter length scales, where interfacial tension is a dominant force. A variety of methods exist for controlling the interfacial tension of aqueous and organic liquids on this scale; however, these techniques have limited utility for liquid metals due to their large interfacial tension.
Liquid metals can form soft, stretchable, and shape-reconfigurable components in electronic and electromagnetic devices. Although it is possible to manipulate these fluids via mechanical methods (e.g., pumping), electrical methods are easier to miniaturize, control, and implement. However, most electrical techniques have their own constraints: electrowetting-on-dielectric requires large (kV) potentials for modest actuation, electrocapillarity can affect relatively small changes in the interfacial tension, and continuous electrowetting is limited to plugs of the liquid metal in capillaries.
Here, we present a method for actuating gallium and gallium-based liquid metal alloys via an electrochemical surface reaction. Controlling the electrochemical potential on the surface of the liquid metal in electrolyte rapidly and reversibly changes the interfacial tension by over two orders of magnitude ( &#820;500 mN/m to near zero). Furthermore, this method requires only a very modest potential (&#60; 1 V) applied relative to a counter electrode. The resulting change in tension is due primarily to the electrochemical deposition of a surface oxide layer, which acts as a surfactant; removal of the oxide increases the interfacial tension, and vice versa. This technique can be applied in a wide variety of electrolytes and is independent of the substrate on which it rests.

We present a method to control the interfacial energy of a liquid metal in an electrolyte via electrochemical deposition (or removal) of a surface oxide layer. This simple method can control the capillary behavior of gallium-based liquid metals by tuning the interfacial energy rapidly, significantly, and reversibly using modest voltages.

Controlling interfacial tension is an effective method for manipulating the shape, position, and flow of fluids at sub-millimeter length scales, where ...

Microfluidic Dry-spinning and Characterization of Regenerated Silk Fibroin Fibers

The protocol demonstrates a method for mimicking the spinning process of silkworm. In the native spinning process, the contracting spinning duct enables the silk proteins to be compact and ordered by shearing and elongation forces. Here, a biomimetic microfluidic channel was designed to mimic the specific geometry of the spinning duct of the silkworm. Regenerated silk fibroin (RSF) spinning doped with high concentration, was extruded through the microchannel to dry-spin fibers at ambient temperature and pressure. In the post-treated process, the as-spun fibers were drawn and stored in ethanol aqueous solution. Synchrotron radiation wide-angle X-ray diffraction (SR-WAXD) technology was used to investigate the microstructure of single RSF fibers, which were fixed to a sample holder with the RSF fiber axis normal to the microbeam of the X-ray. The crystallinity, crystallite size, and crystalline orientation of the fiber were calculated from the WAXD data. The diffraction arcs near the equator of the two-dimensional WAXD pattern indicate that the post-treated RSF fiber has a high orientation degree.

A protocol for the microfluidic spinning and microstructure characterization of regenerated silk fibroin monofilament is presented.

The protocol demonstrates a method for mimicking the spinning process of silkworm. In the native spinning process, the contracting spinning duct enables ...

Synthesis and Performance Characterizations of Transition Metal Single Atom Catalyst for Electrochemical CO2 Reduction

This protocol presents both the synthesis method of the Ni single atom catalyst, and the electrochemical testing of its catalytic activity and selectivity in aqueous CO2 reduction. Different from traditional metal nanocrystals, the synthesis of metal single atoms involves a matrix material that can confine those single atoms and prevent them from aggregation. We report an electrospinning and thermal annealing method to prepare Ni single atoms dispersed and coordinated in a graphene shell, as active centers for CO2 reduction to CO. During the synthesis, N dopants play a critical role in generating graphene vacancies to trap Ni atoms. Aberration-corrected scanning transmission electron microscopy and three-dimensional atom probe tomography were employed to identify the single Ni atomic sites in graphene vacancies. Detailed setup of electrochemical CO2 reduction apparatus coupled with an on-line gas chromatography is also demonstrated. Compared to metallic Ni, Ni single atom catalyst exhibit dramatically improved CO2 reduction and suppressed H2 evolution side reaction.

Synthesis and Performance Characterizations of Transition Metal Single Atom Catalyst for Electrochemical CO2 Reduction

Here, we present a protocol for the synthesis and electrochemical testing of transition metal single atoms coordinated in graphene vacancies as active centers for selective carbon dioxide reduction to carbon monoxide in aqueous solutions.

This protocol presents both the synthesis method of the Ni single atom catalyst, and the electrochemical testing of its catalytic activity and selectivity ...

Ligand-Mediated Nucleation and Growth of Palladium Metal Nanoparticles

The size, size distribution and stability of colloidal nanoparticles are greatly affected by the presence of capping ligands. Despite the key contribution of capping ligands during the synthesis reaction, their role in regulating the nucleation and growth rates of colloidal nanoparticles is not well understood. In this work, we demonstrate a mechanistic investigation of the role of trioctylphosphine (TOP) in Pd nanoparticles in different solvents (toluene and pyridine) using in situ SAXS and ligand-based kinetic modeling. Our results under different synthetic conditions reveal the overlap of nucleation and growth of Pd nanoparticles during the reaction, which contradicts the LaMer-type nucleation and growth model. The model accounts for the kinetics of Pd-TOP binding for both, the precursor and the particle surface, which is essential to capture the size evolution as well as the concentration of particles in situ. In addition, we illustrate the predictive power of our ligand-based model through designing the synthetic conditions to obtain nanoparticles with desired sizes. The proposed methodology can be applied to other synthesis systems and therefore serves as an effective strategy for predictive synthesis of colloidal nanoparticles.

The main goal of this work is to elucidate the role of capping agents in regulating the size of palladium nanoparticles by combining in situ small angle x-ray scattering (SAXS) and ligand-based kinetic modeling.

The size, size distribution and stability of colloidal nanoparticles are greatly affected by the presence of capping ligands. Despite the key contribution ...

Surface Properties of Synthesized Nanoporous Carbon and Silica Matrices

In this work, we report the synthesis and characterization of ordered nanoporous carbon material (also called ordered mesoporous carbon material [OMC]) with a 4.6 nm pore size, and ordered silica porous matrix, SBA-15, with a 5.3 nm pore size. This work describes the surface properties of nanoporous molecular sieves, their wettability, and the melting behavior of D2O confined in the differently ordered porous materials with similar pore sizes. For this purpose, OMC and SBA-15 with highly ordered nanoporous structures are synthesized via impregnation of the silica matrix by applying a carbon precursor and by the sol-gel method, respectively. The porous structure of investigated systems is characterized by an N2 adsorption-desorption analysis at 77 K. To determine the electrochemical character of the surface of synthesized materials, potentiometric titration measurements are conducted; the obtained results for OMC shows a significant pHpzc shift toward the higher values of pH, relative to SBA-15. This suggests that investigated OMC has surface properties related to oxygen-based functional groups. To describe the surface properties of the materials, the contact angles of liquids penetrating the studied porous beds are also determined. The capillary rise method has confirmed the increased wettability of the silica walls relative to the carbon walls and an influence of the pore roughness on the fluid/wall interactions, which is much more pronounced for silica than for carbon mesopores. We have also studied the melting behavior of D2O confined in OMC and SBA-15 by applying the dielectric method. The results show that the depression of the melting temperature of D2O in the pores of OMC is about 15 K higher relative to the depression of the melting temperature in SBA-15 pores with a comparable 5 nm size. This is caused by the influence of adsorbate/adsorbent interactions of the studied matrices.

Here we report the synthesis and characterization of ordered nanoporous carbon (with a 4.6 nm pore size) and SBA-15 (with a 5.3 nm pore size). The work describes the surface and textural properties of nanoporous molecular sieves, their wettability, and the melting behavior of D2O confined in the materials.

In this work, we report the synthesis and characterization of ordered nanoporous carbon material (also called ordered mesoporous carbon material [OMC]) ...

Synthesis and Characterization of Amphiphilic Gold Nanoparticles

Gold nanoparticles covered with a mixture of 1-octanethiol (OT) and 11-mercapto-1-undecane sulfonic acid (MUS) have been extensively studied because of their interactions with cell membranes, lipid bilayers, and viruses. The hydrophilic ligands make these particles colloidally stable in aqueous solutions and the combination with hydrophobic ligands creates an amphiphilic particle that can be loaded with hydrophobic drugs, fuse with the lipid membranes, and resist nonspecific protein adsorption. Many of these properties depend on nanoparticle size and the composition of the ligand shell. It is, therefore, crucial to have a reproducible synthetic method and reliable characterization techniques that allow the determination of nanoparticle properties and the ligand shell composition. Here, a one-phase chemical reduction, followed by a thorough purification to synthesize these nanoparticles with diameters below 5 nm, is presented. The ratio between the two ligands on the surface of the nanoparticle can be tuned through their stoichiometric ratio used during synthesis. We demonstrate how various routine techniques, such as transmission electron microscopy (TEM), nuclear magnetic resonance (NMR), thermogravimetric analysis (TGA), and ultraviolet-visible (UV-Vis) spectrometry, are combined to comprehensively characterize the physicochemical parameters of the nanoparticles.

Amphiphilic gold nanoparticles can be used in many biological applications. A protocol to synthesize gold nanoparticles coated by a binary mixture of ligands and a detailed characterization of these particles is presented.

Gold nanoparticles covered with a mixture of 1-octanethiol (OT) and 11-mercapto-1-undecane sulfonic acid (MUS) have been extensively studied because of ...

Fabrication of Thin Film Silver/Silver Chloride Electrodes with Finely Controlled Single Layer Silver Chloride

This paper aims to present a protocol to form smooth and well-controlled films of silver/silver chloride (Ag/AgCl) with designated coverage on top of thin film silver electrodes. Thin film silver electrodes sized 80 &#181;m x 80 &#181;m and 160 &#181;m x 160 &#181;m were sputtered on quartz wafers with a chromium/gold (Cr/Au) layer for adhesion. After passivation, polishing and cathodic cleaning processes, the electrodes underwent galvanostatic oxidation with consideration of Faraday&#39;s Law of Electrolysis to form smooth layers of AgCl with a designated degree of coverage on top of the silver electrode. This protocol is validated by inspection of scanning electron microscope (SEM) images of the surface of the fabricated Ag/AgCl thin film electrodes, which highlights the functionality and performance of the protocol. Sub-optimally fabricated electrodes are fabricated as well for comparison. This protocol can be widely used to fabricate Ag/AgCl electrodes with specific impedance requirements (e.g., probing electrodes for impedance sensing applications like impedance flow cytometry and interdigitated electrode arrays).

This paper aims to present a method to form smooth and well-controlled films of silver chloride (AgCl) with designated coverage on top of thin film silver electrodes.

This paper aims to present a protocol to form smooth and well-controlled films of silver/silver chloride (Ag/AgCl) with designated coverage on top of thin ...

Synthesis of Functionalized Magnetic Nanoparticles, Their Conjugation with the Siderophore Feroxamine and its Evaluation for Bacteria Detection

In the present work, the synthesis of magnetic nanoparticles, its coating with SiO2, followed by its amine functionalization with (3-aminopropyl)triethoxysilane (APTES) and its conjugation with deferoxamine, a siderophore recognized by Yersinia enterocolitica, using a succinyl moiety as a linker are described.
Magnetic nanoparticles (MNP) of magnetite (Fe3O4) were prepared by solvothermal method and coated with SiO2 (MNP@SiO2) using the St&#246;ber process followed by functionalization with APTES (MNP@SiO2@NH2). Then, feroxamine was conjugated with the MNP@SiO2@NH2 by carbodiimide coupling to give MNP@SiO2@NH2@Fa. The morphology and properties of the conjugate and intermediates were examined by eight different methods including powder X-Ray diffraction (XRD), Fourier transform infrared spectroscopy (FT-IR), Raman spectroscopy, X-ray photoelectron spectroscopy (XPS), transmission electron microscopy (TEM) and energy dispersive X-Ray (EDX) mapping. This exhaustive characterization confirmed the formation of the conjugate. Finally, in order to evaluate the capacity and specificity of the nanoparticles, they were tested in a capture bacteria assay using Yersinia enterocolitica.

This work describes protocols for the preparation of magnetic nanoparticles, its coating with SiO2, followed by its amine functionalization with (3-aminopropyl)triethoxysilane (APTES) and its conjugation with deferoxamine using a succinyl moiety as a linker. A deep structural characterization description and a capture bacteria assay using Y. enterocolitica for all the intermediate nanoparticles and the final conjugate are also described in detail.

In the present work, the synthesis of magnetic nanoparticles, its coating with SiO2, followed by its amine functionalization with ...

Preparation of Silver-Palladium Alloyed Nanoparticles for Plasmonic Catalysis under Visible-Light Illumination

Localized surface plasmon resonance (LSPR) in plasmonic nanoparticles (NPs) can accelerate and control the selectivity of a variety of molecular transformations. This opens possibilities for the use of visible or near-IR light as a sustainable input to drive and control reactions when plasmonic nanoparticles supporting LSPR excitation in these ranges are employed as catalysts. Unfortunately, this is not the case for several catalytic metals such as palladium (Pd). One strategy to overcome this limitation is to employ bimetallic NPs containing plasmonic and catalytic metals. In this case, the LSPR excitation in the plasmonic metal can contribute to accelerate and control transformations driven by the catalytic component. The method reported herein focuses on the synthesis of bimetallic silver-palladium (Ag-Pd) NPs supported on ZrO2 (Ag-Pd/ZrO2) that acts as a plasmonic-catalytic system. The NPs were prepared by co-impregnation of corresponding metal precursors on the ZrO2 support followed by simultaneous reduction leading to the formation of bimetallic NPs directly on the ZrO2 support. The Ag-Pd/ZrO2 NPs were then used as plasmonic catalysts for the reduction of nitrobenzene under 425 nm illumination by LED lamps. Using gas chromatography (GC), the conversion and selectivity of the reduction reaction under the dark and light irradiation conditions can be monitored, demonstrating the enhanced catalytic performance and control over selectivity under LSPR excitation after alloying non-plasmonic Pd with plasmonic metal Ag. This technique can be adapted to a wide range of molecular transformations and NPs compositions, making it useful for the characterization of the plasmonic catalytic activity of different types of catalysis in terms of conversion and selectivity.

Presented here is a protocol for the synthesis of silver-palladium (Ag-Pd) alloy nanoparticles (NPs) supported on ZrO2 (Ag-Pd/ZrO2). This system allows for harvesting energy from visible light irradiation to accelerate and control molecular transformations. This is illustrated by nitrobenzene reduction under light irradiation catalyzed by Ag-Pd/ZrO2 NPs.

Localized surface plasmon resonance (LSPR) in plasmonic nanoparticles (NPs) can accelerate and control the selectivity of a variety of molecular ...

Preparation of Nanoparticles for ToF-SIMS and XPS Analysis

Nanoparticles have gained increasing attention in recent years due to their potential and application in different fields including medicine, cosmetics, chemistry, and their potential to enable advanced materials. To effectively understand and regulate the physico-chemical properties and potential adverse effects of nanoparticles, validated measurement procedures for the various properties of nanoparticles need to be developed. While procedures for measuring nanoparticle size and size distribution are already established, standardized methods for analysis of their surface chemistry are not yet in place, although the influence of the surface chemistry on nanoparticle properties is undisputed. In particular, storage and preparation of nanoparticles for surface analysis strongly influences the analytical results from various methods, and in order to obtain consistent results, sample preparation must be both optimized and standardized. In this contribution, we present, in detail, some standard procedures for preparing nanoparticles for surface analytics. In principle, nanoparticles can be deposited on a suitable substrate from suspension or as a powder. Silicon (Si) wafers are commonly used as substrate, however, their cleaning is critical to the process. For sample preparation from suspension, we will discuss drop-casting and spin-coating, where not only the cleanliness of the substrate and purity of the suspension but also its concentration play important roles for the success of the preparation methodology. For nanoparticles with sensitive ligand shells or coatings, deposition as powders is more suitable, although this method requires particular care in fixing the sample.

A number of different procedures for preparing nanoparticles for surface analysis are presented (drop casting, spin coating, deposition from powders, and cryofixation). We discuss the challenges, opportunities, and possible applications of each method, particularly regarding the changes in the surface properties caused by the different preparation methods.

Nanoparticles have gained increasing attention in recent years due to their potential and application in different fields including medicine, cosmetics, ...