Name: preparation of silica nanoparticles through microwave-assisted acid-catalysis
Uploaded: 2013-12-16T14:15:00
Description: Watch this Scientific Journal Video about Preparation of Silica Nanoparticles Through Microwave-assisted Acid-catalysis at JoVE.com

Funding was provided by the Defense Threat Reduction Agency, Physical Science and Technology Division, Protection and Hazard Mitigation technical area. This research was supported in part by an appointment to the Postgraduate Research Participation Program at the Air Force Research Laboratory administered by the Oak Ridge Institute for Science and Education (ORISE) through an interagency agreement between the U.S. Department of Energy and the Air Force Research Laboratory, Materials and Manufacturing Directorate, Airbase Technologies Division (AFRL/RXQ).

1.&#160;Preparation and Calculations
<ol>
	<li>Prepare 1 mM HCl solution using concentrated hydrochloric acid, 37%, and water. 
	Note: Caution should always be used when handling concentrated acids. Concentrated acid should always be added to water, never add water to concentrated acid.</li>
	<li>Determine the desired concentration of TMOS, siloxane precursor, for the microwave reaction. A TMOS concentration of 25 mM will be used for procedural demonstrations.</li>
</ol>
2.&#160;Hydrolysis of...

<ol>
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The microwave-assisted methods described in this manuscript are advantageous over conventional heating methods because SiO2 NPs can be synthesized accurately, precisely, and quickly. The following criteria should be followed to eliminate any potential issues associated with SiO2 NPs formation by these microwave-associated techniques: 1) use of a catalyst such as 1 mM HCl, 2) hydrolysis of the TMOS should be completed before addition of acetone, 3) use of an aprotic solvent such as acetone, 4) use of...

Silica nanoparticles (SiO2 NPs) were first synthesized by St&#246;ber1 and through modifications2-7 have become the preferred method for SiO2 NPs synthesis. Typically, St&#246;ber reactions are catalyzed by alkaline conditions where silica sols are formed. Acid-catalyzed reactions are used less frequently than alkaline-catalyzed reactions due to the greater degree of difficulty of hydrolysis of the siloxane precursor. Unlike alkaline-catalyzed reactions, acid-catalyzed reactions preferentially form silica gels.8
Microwave-assisted chemical reactions are an emerging technique within the scientific community and in literature due to the associated benefits to the techniques9-18. Specifically, microwave-assisted techniques have been shown to be advantageous in the synthesis of nanomaterials where the promotion of spontaneous nucleation events is desired. Microwave conditions are advantageous because microwave reactors deliver controlled power quickly to the reaction10. Until recently19, the synthesis of SiO2 NPs using microwave reactors have been used with limited success mainly as a result of issues with reproducibility20-22.
The details and procedural methods often reported in the literature on the synthesis of nanomaterials often tend to be obscure and sometimes seen as an &#34;art-form.&#34; Combining microwave-assisted synthetic techniques and nanomaterial synthesis can compound the subject even further. The purpose of this manuscript is to guide researchers in the synthesis of nanomaterials by microwave-assisted techniques, eliminate obscurity associated with these techniques, and point out common mistakes associated with these techniques.
In a microwave chemical reaction, any molecular species containing a permanent dipole is capable of interacting and perturbing the electromagnetic (EM) field. These species are not limited solely to the reagents and solvents used within the reaction, but can be any substance placed in the EM field i.e. glass vials, salts, ionic liquids.
The ability for a specific substance to effectively convert EM energy into heat is defined as the loss factor of a material or tan &#948;. Solvents are commonly classified by their loss factor where values for tan &#948; &#62; 0.5 are considered high, 0.1 &#62; tan &#948; &#62; 0.5 are considered medium, and tan &#948; &#60; 0.1 are considered low. These loss factors values relate the ability for a particular solvent to couple or absorb microwave energy and convert that energy into heat. Thermal energy is generated through molecular friction of species attempting to align with the oscillating EM field. If solvents with high tan &#948; values are used within a reaction, the solvent will dominate the microwave absorption events, masking the precursor or reagents, leading to bulk heating as a result of the solvent strongly coupling with the EM field.
Typically, polar solvents are used in SiO2 NP synthesis to ensure reagent solubility and for donation of labile protons23. Common solvents used in SiO2 NP syntheses are alcohol solvents such as ethanol, methanol or 2-propanol. These solvents all have high tan &#948; values (0.941, 0.799, and 0.659 for ethanol, 2-propanol and methanol, respectively) making them poor solvent choices for microwave-assisted chemical reactions of SiO2 NPs as they efficiently couple with the EM field. It is our belief that microwave-assisted reactions are most effective when low tan &#948; solvents are used in combination with polar molecular precursors in synthetic reactions. These circumstances allow for the molecular precursors to couple with the EM field, providing molecular heating, while the solvent interacts minimally. For microwave-assisted reactions in this manuscript, acetone is used as an alternative to the commonly used alcohol solvents associated with SiO2 NPs synthesis. Acetone is considered a low loss factor solvent (tan &#948; = 0.054), which limits the solvent interactions within the EM field allowing selective microwave absorption with the reactants meditating silica condensation reactions.
In this manuscript, we outline the procedures associated with the microwave-assisted synthesis of SiO2 NPs which are accurate, precise and quick. SiO2 NP growth is achieved by effective coupling of the precursor with the EM field while the solvent has a minimal role in heating. Hydrolysis of the siloxane precursor is achieved by using hydrochloric acid, which leads to slower rates of hydrolysis and limits further condensation reactions. Alkaline-catalyzed reactions have much faster reaction rates and can complicate growth processes when used with microwave-assisted techniques. The resultant SiO2 NPs synthesized by these techniques range in diameters from 30 nm up to diameters greater than 250 nm. SiO2 NP size is controlled by varying the precursor concentration and exposure time to the microwave radiation.

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			<td height="25" style="height:25px;width:247px;">Name of the reagent</td>
			<td style="width:207px;">Company</td>
			<td style="width:153px;">Catalogue number</td>
			<td style="width:161px;">Comments (optional)</td>
		</tr>
		<tr height="25">
			<td height="25" style="height:25px;width:247px;">Tetramethylorthosilicate</td>
			<td style="width:207px;">Sigma Aldrich</td>
			<td style="width:153px;">218472</td>
			<td style="width:161px;"></td>
		</tr>
		<tr height="25">
			<td height="25" style="height:25px;width:247px;">Hydrochloric acid, 37%</td>
			<td style="width:207px;">Sigma Aldrich</td>
			<td style="width:153px;">435570</td>
			<td style="width:161px;"></td>
		</tr>
		<tr height="25">
			<td height="25" style="height:25px;width:247px;">Acetone</td>
			<td style="width:207px;">Fisher</td>
			<td style="width:153px;">A949SK</td>
			<td style="width:161px;"></td>
		</tr>
		<tr height="25">
			<td height="25" style="height:25px;width:247px;">Sulfuric acid</td>
			<td style="width:207px;">EMD Millipore</td>
			<td style="width:153px;">SX1244</td>
			<td style="width:161px;"></td>
		</tr>
		<tr height="25">
			<td height="25" style="height:25px;width:247px;">Hydrogen peroxide, 30%</td>
			<td style="width:207px;">EMD Millipore</td>
			<td style="width:153px;">HX0635</td>
			<td style="width:161px;"></td>
		</tr>
		<tr height="25">
			<td height="25" style="height:25px;width:247px;">Discover microwave reactor</td>
			<td style="width:207px;">CEM</td>
			<td style="width:153px;"></td>
			<td style="width:161px;"></td>
		</tr>
		<tr height="25">
			<td height="25" style="height:25px;width:247px;">10 ml Borosilicate reaction vial</td>
			<td style="width:207px;">CEM</td>
			<td style="width:153px;">908035</td>
			<td style="width:161px;"></td>
		</tr>
		<tr height="25">
			<td height="25" style="height:25px;width:247px;">10 ml Snap cap</td>
			<td style="width:207px;">CEM</td>
			<td style="width:153px;">909210</td>
			<td style="width:161px;"></td>
		</tr>
		<tr height="25">
			<td height="25" style="height:25px;width:247px;">3 mm Stir bar</td>
			<td style="width:207px;">Fisher Scientific</td>
			<td style="width:153px;">14-513-65</td>
			<td style="width:161px;"></td>
		</tr>
		<tr height="25">
			<td height="25" style="height:25px;width:247px;">Highly polished silicon wafers</td>
			<td style="width:207px;">Broker</td>
			<td style="width:153px;">SP064483</td>
			<td style="width:161px;"></td>
		</tr>
		<tr height="25">
			<td height="25" style="height:25px;width:247px;">S4800 SEM</td>
			<td style="width:207px;">Hitachi</td>
			<td style="width:153px;"></td>
			<td style="width:161px;"></td>
		</tr>
		<tr height="25">
			<td height="25" style="height:25px;width:247px;">Zetasizer Nano90</td>
			<td style="width:207px;">Malvern</td>
			<td style="width:153px;"></td>
			<td style="width:161px;"></td>
		</tr>
		<tr height="25">
			<td height="25" style="height:25px;width:247px;">Polystyrene cuvette, (10 mm x 10 mm x 45mm)</td>
			<td style="width:207px;">Sarstedt</td>
			<td style="width:153px;">67.754</td>
			<td style="width:161px;"></td>
		</tr>
		<tr height="25">
			<td height="25" style="height:25px;width:247px;">5415D centrifuge</td>
			<td style="width:207px;">Eppendorf</td>
			<td></td>
			<td></td>
		</tr>
		<tr height="25">
			<td height="25" style="height:25px;width:247px;">Hummer 6.2 sputter system</td>
			<td style="width:207px;">Anatech</td>
			<td></td>
			<td></td>
		</tr>
	</tbody>
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preparation of silica nanoparticles through microwave-assisted acid-catalysis

С помощью микроволн синтетические методы были использованы, чтобы быстро и воспроизводимо создавать кремнезем наночастиц золей с использованием кислотного катализатора с диаметром наночастиц в диапазоне от 30-250 нм при варьировании условий реакции. Через выбора микроволновой совместимом растворителе, предшественника кремниевой кислоты, катализатора, и время микроволнового облучения, эти помощью микроволн методы были способны преодолеть сообщалось ранее недостатки, связанные с синтезом оксида кремния наночастиц с использованием микроволновой реакторов. Силоксан предшественник гидролизовали с помощью кислотного катализатора, HCl. Ацетон, низкий-тан δ растворитель, посредником на конденсацию и имеет минимальное взаимодействие с электромагнитным полем. Реакции конденсации начинаются тогда, когда кислые пары предшественники кислоты с микроволнового излучения, что приводит к образованию диоксида кремния наночастиц Соль. Наночастицы кремнезема характеризуется динамичным данных рассеяния света и сканировг электронная микроскопия, которые показывают морфология и размер Материалы &quot;, зависит от условий реакции. С помощью микроволн реакции производят диоксида кремния наночастиц с шероховатыми текстурированных поверхностей, которые являются нетипичными для кремниевых золей, полученных методами Stober в, которые имеют гладкие поверхности.

Temperature, pressure, and microwave power traces for a representative SiO2 NP microwave-assisted reaction are presented in Figure 1. The microwave reaction plot is divided into three sections - ramping, reaction, and cooling. A reaction temperature of 125 &#176;C and reaction time of 60 sec are used in this representative SiO2 NP reaction. During the ramping portion, the power is maximized at 300 W (or near max power) so that the reaction temperature can be reached quickly without ...

Watch this Scientific Journal Video about Preparation of Silica Nanoparticles Through Microwave-assisted Acid-catalysis at JoVE.com

Preparation of Silica Nanoparticles Through Microwave-assisted Acid-catalysis

Silica nanoparticles were prepared using acid-catalysis of a siloxane precursor and microwave-assisted synthetic techniques resulting in the controlled growth of nanomaterials ranging from 30-250 nm in diameter. The growth dynamics can be controlled by varying the initial silicic acid concentration, time of the reaction, and temperature of reaction.

Подготовка Silica наночастиц Через СВЧ-помощь кислотно-катализа

Microwave-assisted synthetic techniques were used to quickly and reproducibly produce silica nanoparticle sols using an acid catalyst with nanoparticle ...

Research

JoVE Journal

Chemistry

Microwave-assisted Intramolecular Dehydrogenative Diels-Alder Reactions for the Synthesis of Functionalized Naphthalenes/Solvatochromic Dyes

Микроволновая печь при содействии Внутримолекулярная Dehydrogenative Дильса-Альдера реакций синтеза функционализированных Нафталины / сольватохромные Красители

Functionalized naphthalenes have applications in a variety of research fields ranging from the synthesis of natural or biologically active molecules to ...

Microwave-assisted Functionalization of Poly(ethylene glycol) and On-resin Peptides for Use in Chain Polymerizations and Hydrogel Formation

Microwave-assisted Functionalization of Polyethylene glycol and On-resin Peptides for Use in Chain Polymerizations and Hydrogel Formation

Микроволновая печь-помощь Функционализация поли (этиленгликоль) и On-смолы пептиды для использования в цепных полимеризации и гидрогеля формирования

One of the main benefits to using poly(ethylene glycol) (PEG) macromers in hydrogel formation is synthetic versatility. The ability to draw from a large ...

Preparation and Characterization of SDF-1&#945;-Chitosan-Dextran Sulfate Nanoparticles

Preparation and Characterization of SDF-1ÃƒÅ½Ã‚Â±-Chitosan-Dextran Sulfate Nanoparticles

Подготовка и характеристика SDF-1α-хитозан-Декстрансульфат наночастиц

Chitosan (CS) and dextran sulfate (DS) are charged polysaccharides (glycans), which form polyelectrolyte complex-based nanoparticles when mixed under ...

One-pot Microwave-assisted Conversion of Anomeric Nitrate-esters to Trichloroacetimidates

Один горшок Микроволновая печь помощь преобразование Anomeric нитрат-эфиры Trichloroacetimidates

The goal of the following procedure is to provide a demonstration of the one-pot conversion of a 2-azido-1-nitrate-ester to a trichloroacetimidate ...

Preparation of Functional Silica Using a Bioinspired Method

Подготовка функциональной кремнезема, с помощью метода Bioinspired

The goal of the protocols described herein is to synthesize bioinspired silica materials, perform enzyme encapsulation therein, and partially or totally ...

Reducing Willow Wood Fuel Emission by Low Temperature Microwave Assisted Hydrothermal Carbonization

Снижение ивы древесины топлива выбросов низкой температурой Микроволновая помощь гидротермических карбонизации

Biomass is a sustainable fuel, as its CO2 emissions are reintegrated in biomass growth. However, the inorganic precursors in the biomass cause a negative ...

Microwave-Assisted Preparation of 1-Aryl-1H-pyrazole-5-amines

Microwave-Assisted Preparation of 1-Aryl-1H-pyrazole-5-amines

Микроволновая подготовка 1-Арил-1H-пиразол-5-аминов

A synthetic process for the preparation of a variety of 1-aryl-1H-pyrazole-5-amines was developed. The microwave-mediated nature of this method makes it ...

A Microwave-Assisted Direct Heteroarylation of Ketones Using Transition Metal Catalysis

Микроволновая помощь Прямая Heteroarylation кетонов использованиеперехода металлический катализ

Heteroarylation introduces heteroaryl fragments to organic molecules. Despite the numerous available reactions reported for arylation via transition metal ...

Nanoparticle Tracking Analysis of Gold Nanoparticles in Aqueous Media through an Inter-Laboratory Comparison

Анализ слежения за наночастицами золота в Aqueous Media с помощью межлабораторного сравнения

In the field of nanotechnology, analytical characterization plays a vital role in understanding the behavior and toxicity of nanomaterials (NMs). ...

Preparation of Nanoparticles for ToF-SIMS and XPS Analysis

Подготовка наночастиц для анализа ToF-SIMS и XPS

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