The authors acknowledge support from Samsung, the NC State Chancellors Innovation Funds, NSF (CAREER CMMI-0954321 and Triangle MRSEC DMR-1121107), and Air Force Research Labs.

1. Manipulation der Grenzflächenspannung des flüssigen Metalls in Electrolyte <ol><li> Oxidation <ol><li> Gießen einer wässrigen Elektrolyten (sauer oder basisch) in eine Petrischale. Um sicherzustellen, daß das Oxid vollständig entfernt wird, verwenden eine Säure oder Base mit einer Konzentration von mehr als 0,1 M 24 (beispielsweise 1 M NaOH oder 1 M HCl). Verwenden Sie ein Volumen, das die Schale bis zu einer Tiefe von ca. 1-3 mm füllen wird. Vermeiden Sie Kontakt mit der Haut mit diesen Lösungen. </li><li> Mit einer Spritze, um einen Tropfen (optimal zwischen 10-500 ul) einer Gallium-Basis-Legierung im Elektrolyt zu platzieren. Beispiele hierfür sind eutektische Gallium-Indium (eGain) oder Gallium-Indium-Zinn (Galinstan). Wenn reinem Gallium verwendet wird, zu erwärmen, daß der Elektrolyt mindestens 30 ° C, um ein Einfrieren zu verhindern. </li><li> Platzieren eines Kupferdrahtes in das flüssige Metall auf die Arbeitselektrode herzustellen. Einen Kupferleiter mit einem Durchmesser kleiner als der der Tropfen, und mit einem Digital-Multimeter nach den Anweisungen des Herstellers, um ENsure, dass der Draht einen Widerstand von &lt;1 Ω. In Säure oder Base, wird das flüssige Metall der Kupfer benetzen und dadurch ein ausgezeichneter elektrischer Kontakt. </li><li> Platzieren eines leitenden Gegenelektrode (beispielsweise Kupfer, Graphit, Platin, etc.) in die Lösung, jedoch nicht in Kontakt mit dem flüssigen Metall. Wenn die Gegenelektrode einen Widerstand von &lt;1 Ω, sind seine Abmessungen irrelevant. </li><li> Verbinden Sie die Kabel mit einer Spannungsquelle und wenden ein positives Potential an das flüssige Metall. Für kleine Form Verformung gelten positive Spannungen &lt;1 V. Bei größeren Form Deformation (und die Bewegung des flüssigen Metalls in Richtung der Gegenelektrode), gelten&gt; 1 V. Anmerkung: Die Konzentration der Lösung und die Entfernung des Abfalls von der Gegenelektrode die Spannung erforderlich, Veränderungen der Grenzflächenspannung zu induzieren, da die Rate der elektrochemischen Oberflächenoxidation konkurriert mit der Rate von Oxidauflösung durch den Elektrolyten zu diktieren. </li></ol></li&gt; <li> Die Ermäßigung <ol><li> Ausgeben einer Abfall (10-500 ul) des flüssigen Metalls von einer Spritze in eine leere Petrischale. </li><li> Gießen einer neutralen wässerigen Elektrolyten in die Petrischale (beispielsweise 1 M Natriumfluorid (NaF) oder 1 M Natriumchlorid (NaCl)) auf ein Niveau, das Metall eintaucht. Anmerkung: Die Verwendung eines sauren (pH &lt;3) oder basischen Lösung (pH&gt; 10) bewirkt, dass das Oxid, spontan zu lösen. </li><li> Platzieren eines Kupferdrahtes in das flüssige Metall als eine Arbeitselektrode und eine stromführende Leitung (beispielsweise Kupfer) in den Elektrolyten, die als Gegenelektrode fungieren zu handeln. </li><li> Verbinden Sie die Kabel mit einer Spannungsquelle und wenden Sie ein negatives Potential an das flüssige Metall. Gelten etwa -1 V, um die Oberflächenoxide zu entfernen, und daß das Metall aus dem Substrat entnetzen. Das Metall sollte auf der Seite, die der Gegenelektrode entnetzen. </li><li> Gelten negativeren Potentialen (&lt;-1 V), um die Oxidschicht vollständig zu entfernen. Vermeiden Sie die Anwendung exceslich große negative Spannungen an Wasserstoffblasen auf das flüssige Metall erscheinen aufgrund der Reduktion des Elektrolyten zu verhindern. </li></ol></li></ol> 2. Oberflächenspannungsmessung über Trauben Droplet <ol><li> Mit Hilfe eines Laser-Cutter oder Fräswerkzeug, schneiden einen direkten Weg von der Mitte bis zum Rand ein Stück Polymethylmethacrylat (PMMA) (~ 1 mm dick) Sie den Pfad zu schneiden nicht den ganzen Weg durch die Dicke der PMMA. nur etwa zur Hälfte geschnitten. Dieses Stück wird als Substrat für das Flüssigmetall zu dienen. Andere flach und elektrisch isolierende Materialien, wie Glas, Keramik oder Polymere können auch als Substrat dienen. </li><li> Mit dem gleichen Werkzeug, schneiden Sie ein 1 mm 2 Loch durch die Mitte des PMMA. </li><li> Verwenden Sie den Pfad als Leitfaden, führen Sie einen isolierten Kupferdraht nur mit der Spitze in die Mitte des PMMA ausgesetzt. Positionieren des Drahtes, so daß er über die PMMA-Oberfläche vorsteht. Verschließen Sie den Draht an Ort und Stelle mit einem dichten Klebstoff. Schneidender Draht gerade über die Oberfläche des PMMA, aber lassen Sie es nicht zu weit zu verlängern (über ~ 100 &amp; mgr; m), oder es wird die Form der Tropfen stören. </li><li> Kleben Sie die PMMA-Stück nach unten in einem transparenten Behälter, durch die ein klares Bild erhalten werden kann. Füllen Sie den Behälter mit 1 M NaOH, und legen Sie eine 25-50 ul Tropfen flüssigen Metalls auf dem hervorstehenden Kupferdraht. Dieser Draht wird als Arbeitselektrode dienen und das Tröpfchen benetzen. </li><li> Platzieren eines Platinnetzes Gegenelektrode und einer gesättigten Silber / Silberchlorid (Ag / AgCl) Referenzelektrode in der Lösung. Verbinden alle Elektroden mit einem Potentiostaten. </li><li> Platzieren des Behälters in einem Kontaktwinkel-Goniometer, so dass das Oberflächenprofil des Tropfens deutlich sichtbar ist. Verwenden des Potentiostaten, um die Spannung in Bezug auf die Referenzelektrode zu steuern, und Verwenden des Goniometers um die Form und damit die Grenzflächenspannung des Tropfens zu messen. Stellen Sie sicher, dass die Winkelmesser für die Messung von ruhenden Tropfens Grenz Tensi istam; es ist auch möglich, benutzerdefinierte achsensymmetrischen Formanalyse Drop Bilder aus einem horizontal angebrachten Kamera 25 aufgenommen zu verwenden. </li></ol> 3. Kapillarinjektion <ol><li> Füllen einer Glaskapillare mit einer Lösung von 1 M NaOH. Kapillardurchmesser sollte ~ 1 mm. </li><li> Platzieren eines Endes der Kapillare bündig mit einem Tropfen des flüssigen Metalls. Ausrichten der Kapillaren, so daß sie parallel zur Oberfläche des Tisches (dh senkrecht zur Schwerkraft) ist. Keine Luftspalten zwischen dem flüssigen Metall Abfall und Elektrolyt-gefüllten Kapillare. Mit einem Wischen, Tupfen Sie überschüssiges Elektrolyt, der während der Montage ausgetreten sein könnten. </li><li> Platzieren eines Kupferdrahtes (Arbeitselektrode) in dem flüssigen Metall und einer leitenden Gegenelektrode (zB Kupferdraht) in das offene Ende der Kapillare, so dass er in Kontakt mit der Lösung. </li><li> Verbinden Sie die Kabel mit einer Spannungsquelle und wenden ein positives Potential an das flüssige Metall. Das flüssige Metall sollte Füllen des c beginnenapillary (vermeiden Sie große Potenziale, die überschüssige Blasenbildung auf der Gegenelektrode verursacht). </li></ol> 4. Kapillar Widerrufsrecht <ol><li> Nutzen softlithographischer 26 und Replika Formtechniken zur mikrofluidischen Kanälen aus Polydimethylsiloxan (PDMS) besteht herzustellen. Herzustellen Kanäle, die etwa 100 bis 1.000 &amp; mgr; m breit sind, 100 um groß, und 25 bis 65 mm lang. Hinweis: Kanalabmessungen 1000 um breit, 100 &amp; mgr; m groß und 65 mm langen Kanal produziert konsistente Ergebnisse, aber andere können auch funktionieren. Alternativ können Glaskapillaren (beispielsweise 1 mm Durchmesser, Borosilikatglas) anstelle des PDMS Mikrokanälen. </li><li> Injizieren Flüssigmetall entweder manuell oder mit Hilfe einer Spritzenpumpe, um den Kanal vollständig zu füllen (dh 6,5 mm 3 für eine 1000 um breit, 100 &amp; mgr; m groß und 65 mm langen Kanal). </li><li> Mit einem Wattestäbchen, das in 1 M NaOH oder 1 M HCl eingetaucht worden ist, entfernen Sie überschüssigen Mengen an liquid Metall von dem Einlass (und, falls erforderlich, der Auslass) des Kanals, so dass das Metall weiterhin bündig mit der oberen Oberfläche der PDMS. </li><li> Unterzutauchen einem Ende des Kanals in dem Elektrolyten (beispielsweise 1 M NaCl) und legen die Anode (beispielsweise Drähte aus Kupfer, Platin oder Wolfram), daß sie den Elektrolyt aber nicht das Metall berührt. </li><li> Am anderen Ende des Kanals, an einen getrennten Elektrode (zB Cu-Draht) auf die Metalloberfläche, so daß flüssiges Metall selbst als Kathode wirkt. </li><li> Verbinden Sie diese Leitungen (dh Anode und Kathode) mit einer Spannungsquelle oder Potentiostaten, und füllen Sie den Stromkreis. Für einen Drei-Elektroden-System, legen Sie die Referenzelektrode, so dass er kaum taucht in den Tropfen des Elektrolyten. </li><li> Vor der Anwendung eines Reduktionsspannung, montieren Sie eine Videokamera auf einem Stativ oder in einem Mikroskop, um die Experimente zu erfassen. Verwenden Sie Autofokus-Modus, um alles im Blick zu bekommen. Nutzen Sie den manuellen Fokus, um eine bessere Kontrolle zu haben überSchärfentiefe, Weißabgleich und ISO. Nutzen Sie gegebenenfalls höhere F Anschlag (dh 11 oder höher), 1/100 Shutter, automatischer Weißabgleich und Auto ISO. </li><li> Starten Sie die Aufnahme des Experiments. Gelten etwa -1 V, um das Flüssigmetall aus den Mikrokanälen zu entziehen. Schalten Sie die Spannung ab, um das Metall verursachen Bewegung in neutralen Elektrolyten zu stoppen. </li></ol>

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The authors have nothing to disclose.

<html> Dieses Verfahren steuert die Oberflächenspannung von Gallium basierenden flüssigen Metallen mit kleinen Spannungen, um die Abscheidung und Entfernung einer Oberflächenoxidschicht zu fahren. Obwohl das Verfahren funktioniert nur in Elektrolytlösungen, es ist einfach und arbeitet in einer Vielzahl von verschiedenen Bedingungen, aber es gibt Feinheiten erwähnenswert. In Abwesenheit von elektrischem Potential, sowohl saure als auch basische Lösungen Wegätzen des Oxids 27. Die Anwendung eines Oxidatio...

This method provides a simple way to control the surface tension of liquid metals containing gallium. The method uses modest voltages (~1 V) applied directly to the liquid metal (relative to a counter electrode in the presence of electrolyte) to achieve enormous and reversible changes to the surface tension of the metal1. 
Surface tension is a dominant force for liquids at small length scales and is important for a number of capillary phenomena including wetting, spreading, and surface-tension driven flow. Consequently, the ability to control surface tension is a sensible way to manipulate the shape, position, and flow of liquids at sub-mm length scales. The most common way to alter surface tension between two fluids is to use a surfactant, which is a molecule that spans the interface between the fluids. Surfactants lower surface tension, but in a way that is not easy to reverse since it is difficult to remove surfactants from the interface. Surface tension can also be altered using a variety of techniques, including temperature gradients2,3, light4, surface chemistry5-7,and voltage8. But most of these methods result in modest changes to surface tension, particularly for liquid metals, which have notably large surface tensions.
The ability to control the surface tension of liquid metal could enable new opportunities for creating shape reconfigurable structures with metallic properties for electronic, thermal, and optical applications9-14. The most common liquid metal is Hg, which is noted for its toxicity. The methods described here are relevant for liquid metals based on gallium. These metals have low viscosity, large surface tension, low volatility (low vapor pressure), and low toxicity15. Importantly, these metals form surface oxides composed of gallium oxide that are a few nm thick in air16. This oxide layer creates a physical skin that historically has been a nuisance for electrochemical and fluid dynamic applications17. The method here utilizes the oxide in new ways to control surface tension.
The most common way to manipulate liquid metals in electrolyte is to apply a potential to the metal relative to a counter electrode18. Oppositely charged ions from the electrolyte match the charges on the metal, causing the interfacial tension to drop. This phenomenon-termed electrocapillarity-has been known since the 1870s as described by Lippman19and has been utilized for alloys of gallium20. Typically, electrocapillarity achieves modest changes to surface tension, since undesirable electrochemical reactions limit the range of voltages applied to the metal. In contrast, the method described here utilizes the surface oxidation of the metal (or conversely, the reduction of the surface oxide) as a way to achieve enormous changes in surface tension above and beyond changes resulting from electrocapillarity. The leading explanation for this phenomenon is that the oxide is asymmetric; that is, the outer surface of the oxide terminates with hydroxyl groups (making a low interfacial tension interface with the aqueous electrolyte), and the interior surface of the oxide terminates with gallium atoms (making a low interfacial tension interface with the metal). In contrast, the removal of the oxide via electrochemical reduction results in a bare metal-electrolyte interface, which returns the metal back to a state of high surface tension. We characterize the interfacial tension of the metal by analyzing the shape of sessile droplets as a function of voltage while assuming that gravity and surface tension are the dominant forces that define the curvature of its surface. 
The advantage of this technique relative to classic electrocapillarity is that it can reversibly tune the tension of low toxicity liquid metals over enormous ranges (from ~500 mN/m to near zero). This delta change in surface tension may be the largest ever reported in literature for any fluid and it can be accomplished in a tunable and reversible manner. These large changes in surface tension are useful for manipulating the capillary behavior of metals; for example, it can induce the metal to spread on a surface, withdraw the metal from microchannels, fill microchannels with metal, and overcome the Rayleigh instabilities to form liquid metal fibers1,21. 
A drawback of this technique is that it requires electrolyte. It works best in acidic or basic conditions, because these electrolytes remove excess surface oxide that would otherwise contaminate the surface of the metal and mechanically restrict the movement of the metal. The simultaneous removal and deposition of the oxide layer complicates the analysis of the interfacial phenomena and it is our hope the methods described in this paper empowers additional analysis. Another disadvantage is that the electrochemical reactions at the surface of the metal must be matched by complimentary half-reactions at the counter electrode22,23. This can lead to hydrogen bubbles forming at the counter electrode.

<table>
	<tbody>
		<tr>
			<td>Eutectic Gallium Indium</td>
			<td>Indium Corporation</td>
			<td></td>
			<td></td>
		</tr>
		<tr>
			<td>Sodium Hydroxide</td>
			<td>Fisher Scientific</td>
			<td>2318-3</td>
			<td></td>
		</tr>
		<tr>
			<td>Hydrochloric Acid</td>
			<td>Fisher Scientific</td>
			<td>A481-212</td>
			<td></td>
		</tr>
		<tr>
			<td>Sodium Fluoride</td>
			<td>Sigma-Aldrich</td>
			<td>201154</td>
			<td></td>
		</tr>
		<tr>
			<td>Optical Adhesive</td>
			<td>Norland</td>
			<td>NOA81</td>
			<td></td>
		</tr>
		<tr>
			<td>Polydimethylsiloxane (Sylgard-184)</td>
			<td>Dow Corning</td>
			<td></td>
			<td>Silicone Elastomer Kit</td>
		</tr>
		<tr>
			<td>Borosilicate Glass Capillaries</td>
			<td>Friedrich and Dimmoch</td>
			<td>B41972</td>
			<td></td>
		</tr>
		<tr>
			<td>Ag/AgCl Reference Electrode</td>
			<td>Microelectrodes Inc.</td>
			<td>MI-401F</td>
			<td></td>
		</tr>
		<tr>
			<td>Voltage Source</td>
			<td>Keithley</td>
			<td>3390</td>
			<td></td>
		</tr>
		<tr>
			<td>Potentiostat</td>
			<td>Gamry</td>
			<td>Ref 600</td>
			<td></td>
		</tr>
		<tr>
			<td>Laser Cutter</td>
			<td>Universal Laser Systems</td>
			<td>VLS 3.50</td>
			<td></td>
		</tr>
	</tbody>
</table>

a method to manipulate surface tension of a liquid metal via surface oxidation and reduction

Steuern der Grenzflächenspannung ist eine wirksame Methode zur Manipulation der Form, Position und den Fluss von Fluiden bei Submillimeterbereich Längenskalen, wobei die Grenzflächenspannung ist eine dominierende Kraft. Eine Vielzahl von Verfahren existieren zur Steuerung der Grenzflächenspannung von wässrigen und organischen Flüssigkeiten auf dieser Skala; Jedoch wurden diese Techniken Dienstprogramm für flüssige Metalle aufgrund ihrer großen Grenzflächenspannung begrenzt. Flüssige Metalle weich, elastisch und form rekonfigurierbare Komponenten in elektronischen und elektromagnetischer Geräte bilden. Obwohl es möglich ist, um diese Flüssigkeiten durch mechanische Verfahren (zB Pumpen) zu manipulieren, sind elektrische Verfahren einfacher zu miniaturisieren, zu steuern und zu realisieren. Allerdings haben die meisten elektrischen Techniken ihre eigenen Einschränkungen: Electrowetting-on-dielektrischen groß (kV) Potentiale für bescheidene Betätigung kann Elektrokapillarität relativ kleine Änderungen in der Oberflächenspannung beeinflussen und erfordert kontinuierliche electrowetting an Steckern des flüssigen Metalls in Kapillaren beschränkt. Hier stellen wir ein Verfahren zum Betätigen Gallium und Gallium basierenden flüssigen Metalllegierungen mittels einer elektrochemischen Oberflächenreaktion. Steuerung des elektrochemischen Potentials an der Oberfläche des flüssigen Metalls in Elektrolyten schnell und reversibel ändert die Grenzflächenspannung um mehr als zwei Grßenordnungen (̴500 mN / m, um in der Nähe von Null). Weiterhin erfordert dieses Verfahren nur eine sehr bescheidene Potential (&lt;1 V) relativ zu einer Gegenelektrode angelegt. Die resultierende Änderung in der Spannung ist im Wesentlichen auf die elektrochemische Abscheidung einer Oxidschicht auf der Oberfläche, die als ein oberflächenaktives Mittel wirkt; Entfernung des Oxids steigt die Grenzflächenspannung, und umgekehrt. Diese Technik kann in einer Vielzahl von Elektrolyten angewendet werden und ist unabhängig von dem Substrat, auf dem sie ruht.

Figur 1 A zeigt ein Beispiel eines einfachen Zwei-Elektroden-Verfahren für die Oxidation und Reduktion. In diesem Fall wird ein 70 ul Tropfen des flüssigen Metalls in einer 1 M NaOH-Lösung in Kontakt gebracht einen Kupferdraht eine elektrische Verbindung zu etablieren. Das 1 M NaOH beseitigt die Oberflächenoxidschicht von dem Metall und ermöglicht es dem Metall zu perlen aufgrund ihrer Grenzflächenspannung. Aufbringen einer 2,...

Watch this Scientific Journal Video about A Method to Manipulate Surface Tension of a Liquid Metal via Surface Oxidation and Reduction at JoVE.com

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

Eine Methode, die Oberflächenspannung eines Liquid Metal manipulieren via Oberfläche Oxidation und Reduktion

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 ...

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Liquids, Solids, and Intermolecular Forces

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15.2K Aufrufe.  North Carolina State University. 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.

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

Exploring the Radical Nature of a Carbon Surface by Electron Paramagnetic Resonance and a Calibrated Gas Flow

While the first Electron Paramagnetic Resonance (EPR) studies regarding the effects of oxidation on the structure and stability of carbon radicals date back to the early 1980s the focus of these early papers primarily characterized the changes to the structures under extremely harsh conditions (pH or temperature)1-3. It is also known that paramagnetic molecular oxygen undergoes a Heisenberg spin exchange interaction with stable radicals that extremely broadens the EPR signal4-6. Recently, we reported interesting results where this interaction of molecular oxygen with a certain part of the existing stable radical structure can be reversibly affected simply by flowing a diamagnetic gas through the carbon samples at STP7. As flows of He, CO2, and N2 had a similar effect these interactions occur at the surface area of the macropore system.
This manuscript highlights the experimental techniques, work-up, and analysis towards affecting the existing stable radical nature in the carbon structures. It is hoped that it will help towards further development and understanding of these interactions in the community at large.

Stable radicals that are present in carbon substrates interact with paramagnetic oxygen through a Heisenberg spin exchange. This interaction can be significantly reduced under STP conditions by flowing a diamagnetic gas over the carbon system. This manuscript describes a simple method to characterize the nature of those radicals.

Exploring the Radical Nature einer Kohlenstoffoberfläche durch Elektronenspinresonanz und einem kalibrierten Gasdurchfluss

While the first Electron Paramagnetic Resonance (EPR) studies regarding the effects of oxidation on the structure and stability of carbon radicals date ...

Forschung

Chemie

Transport of Surface-modified Carbon Nanotubes through a Soil Column

Carbon nanotubes (CNTs) are widely manufactured nanoparticles, which are being utilized in a number of consumer products, such as sporting goods, electronics and biomedical applications. Due to their accelerating production and use, CNTs constitute a potential environmental risk if they are released to soil and groundwater systems. It is therefore essential to improve the current understanding of environmental fate and transport of CNTs. The transport and retention of CNTs in both natural and artificial media have been reported in literature, but the findings widely vary and are thus not conclusive. There are a number of physical and chemical parameters responsible for variation in retention and transport. In this study, a complete procedure of selected multiwalled carbon nanotubes (MWCNTs) is presented starting from their surface modification to a complete set of laboratory column experiments at critical physical and chemical scenarios. Results indicate that the stability of the commercially available MWCNTs are critical with their attached surface functional group which can also influence the transport and retention of MWCNT through the surrounding medium.

Surface properties of a nanoparticle are important for their interaction with the surrounding medium. Therefore the surface modification of carbon nanotubes can be critical for their transport and retention through porous media. Here, lab scale column experiments are used to understand the possible transport and retention of these nanoparticles.

Transport von oberflächenmodifizierte Kohlenstoff-Nanoröhren durch eine Bodensäule

Carbon nanotubes (CNTs) are widely manufactured nanoparticles, which are being utilized in a number of consumer products, such as sporting goods, ...

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

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

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

Synthese und Exfoliation von diskotischen Zirkoniumphosphaten Erhalten Kolloidales Liquid Crystals

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

Failure of Cleaning Verification in Pharmaceutical Industry Due to Uncleanliness of Stainless Steel Surface

The aim of this work is to identify the parameters that affect the recovery of pharmaceutical residues from the surface of stainless steel coupons. A series of factors were assessed, including drug product spike levels, spiking procedure, drug-excipient ratios, analyst-to-analyst variability, intraday variability, and cleaning procedure of the coupons. The lack of a well-defined procedure that consistently cleaned the coupon surface was identified as the major contributor to low and variable recoveries. Assessment of cleaning the surface of the coupons with clean-in-place solutions (CIP) gave high recovery (&#62;90%) and reproducible results (Srel&#8804;4%) regardless of the conditions that were assessed previously. The approach was successfully applied for cleaning verification of small molecules (MW &#60;1,000 Da) as well as large biomolecules (MW up to 50,000 Da).

The lack of a well-defined procedure that consistently cleaned coupon surfaces was identified as the major contributor to low and variable recoveries in cleaning verification. This manuscript describes the correct protocol of cleaning stainless steel coupons.

Mangelnde Reinigung Überprüfung in der pharmazeutischen Industrie wegen Unreinheit des Edelstahl-Oberfläche

The aim of this work is to identify the parameters that affect the recovery of pharmaceutical residues from the surface of stainless steel coupons. A ...

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.

Synthese von Substrat-gebundenen Au Nanodrähten über eine aktive Oberfläche Wachstumsmechanismus

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

A Rapid Synthesis Method for Au, Pd, and Pt Aerogels Via Direct Solution-Based Reduction

Here, a method to synthesize gold, palladium, and platinum aerogels via a rapid, direct solution-based reduction is presented. The combination of various precursor noble metal ions with reducing agents in a 1:1 (v/v) ratio results in the formation of metal gels within seconds to minutes compared to much longer synthesis times for other techniques such as sol-gel. Conducting the reduction step in a microcentrifuge tube or small volume conical tube facilitates a proposed nucleation, growth, densification, fusion, equilibration model for gel formation, with final gel geometry smaller than the initial reaction volume. This method takes advantage of the vigorous hydrogen gas evolution as a by-product of the reduction step, and as a consequence of reagent concentrations. The solvent accessible specific surface area is determined with both electrochemical impedance spectroscopy and cyclic voltammetry. After rinsing and freeze drying, the resulting aerogel structure is examined with scanning electron microscopy, X-ray diffractometry, and nitrogen gas adsorption. The synthesis method and characterization techniques result in a close correspondence of aerogel ligament sizes. This synthesis method for noble metal aerogels demonstrates that high specific surface area monoliths may be achieved with a rapid and direct reduction approach.

A rapid, direct solution-based reduction synthesis method to obtain Au, Pd, and Pt aerogels is presented.

Eine schnelle Synthese-Methode für Au, Pd und Pt-Aerogelen über lösungsorientierte Direktreduktion

Here, a method to synthesize gold, palladium, and platinum aerogels via a rapid, direct solution-based reduction is presented. The combination of various ...

Surface Functionalization of Metal-Organic Frameworks for Improved Moisture Resistance

Metal-organic frameworks (MOFs) are a class of porous inorganic materials with promising properties in gas storage and separation, catalysis and sensing. However, the main issue limiting their applicability is their poor stability in humid conditions. The common methods to overcome this problem involve the formation of strong metal-linker bonds by using highly charged metals, which is limited to a number of structures, the introduction of alkylic groups to the framework by post-synthetic modification (PSM) or chemical vapour deposition (CVD) to enhance overall hydrophobicity of the framework. These last two usually provoke a drastic reduction of the porosity of the material. These strategies do not permit to exploit the properties of the MOF already available and it is imperative to find new methods to enhance the stability of MOFs in water while keeping their properties intact. Herein, we report a novel method to enhance the water stability of MOF crystals featuring Cu2(O2C)4&#160;paddle-wheel units, such as HKUST (where HKUST stands for Hong Kong University of Science &#38; Technology), with the catechols functionalized with alkyl and fluoro-alkyl chains. By taking advantage of the unsaturated metal sites and the catalytic catecholase-like activity of CuII ions, we are able to create robust hydrophobic coatings through the oxidation and subsequent polymerization of the catechol units on the surface of the crystals under anaerobic and water-free conditions without disrupting the underlying structure of the framework. This approach not only affords the material with improved water stability but also provides control over the function of the protective coating, which enables the development of functional coatings for the adsorption and separations of volatile organic compounds. We are confident that this approach could also be extended to other unstable MOFs featuring open metal sites.

Robust functional catechol coatings were produced in one step by direct reaction of the material known as HKUST with synthetic catechols under anaerobic conditions. The formation of homogeneous coatings surrounding the entire crystal is ascribed to the biomimetic catalytic activity of Cu(II) dimers on the external surface of the crystals.

Oberfläche Funktionalisierung der Metall-organischen Frameworks für verbesserte Feuchtigkeitsbeständigkeit

Metal-organic frameworks (MOFs) are a class of porous inorganic materials with promising properties in gas storage and separation, catalysis and sensing. ...

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.

Oberflächeneigenschaften von synthetisierten nanoporöse Carbon und Silica-Matrizen

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

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.

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

Bio-inspirierte Polydopamine Oberflächenmodifizierung von Nano-Diamanten und der Reduktion von Silber-Nanopartikeln

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

U2O5 Film Preparation via UO2 Deposition by Direct Current Sputtering and Successive Oxidation and Reduction with Atomic Oxygen and Atomic Hydrogen

We describe a method to produce U2O5 films in situ using the Labstation, a modular machine developed at JRC Karlsruhe. The Labstation, an essential part of the Properties of Actinides under Extreme Conditions laboratory (PAMEC), allows the preparation of films and studies of sample surfaces using surface analytical techniques such as X-ray and ultra-violet photoemission spectroscopy (XPS and UPS, respectively). All studies are made in situ, and the films, transferred under ultra-high vacuum from their preparation to an analyses chamber, are never in contact with the atmosphere. Initially, a film of UO2 is prepared by direct current (DC) sputter deposition on a gold (Au) foil then oxidized by atomic oxygen to produce a UO3 film. This latter is then reduced with atomic hydrogen to U2O5. Analyses are performed after each step involving oxidation and reduction, using high-resolution photoelectron spectroscopy to examine the oxidation state of uranium. Indeed, the oxidation and reduction times and corresponding temperature of the substrate during this process have severe effects on the resulting oxidation state of the uranium. Stopping the reduction of UO3 to U2O5 with single U(V) is quite challenging; first, uranium-oxygen systems exist in numerous intermediate phases. Second, differentiation of the oxidation states of uranium is mainly based on satellite peaks, whose intensity peaks are weak. Also, experimenters should be aware that X-ray spectroscopy (XPS) is a technique with an atomic sensitivity of 1% to 5%. Thus, it is important to obtain a complete picture of the uranium oxidation state with the entire spectra obtained on U4f, O1s, and the valence band (VB). Programs used in the Labstation include a linear transfer program developed by an outside company (see Table of Materials) as well as data acquisition and sputter source programs, both developed in-house.

U2O5 Film Preparation via UO2 Deposition by Direct Current Sputtering and Successive Oxidation and Reduction with Atomic Oxygen and Atomic Hydrogen

This protocol presents the preparation of U2O5 thin films obtained in situ under ultra-high vacuum. The process involves oxidation and reduction of UO2 films with atomic oxygen and atomic hydrogen, respectively.

U2O5 Film Vorbereitung über UO2 Ablagerung von Gleichstrom-Sputtern und aufeinanderfolgenden Oxidation und Reduktion mit atomarem Sauerstoff und atomarer Wasserstoff

We describe a method to produce U2O5 films in situ using the Labstation, a modular machine developed at JRC Karlsruhe. The Labstation, an essential part ...