This work was supported by the National Nature Science Foundation of China (Grant&nbsp;No. 21776095), the Guangzhou Science and Technology Key Program (Grant&nbsp;No. 201804020048), and Guangdong Key Laboratory of Clean Energy Technology (Grant No. 2008A060301002). We thank LetPub (www.letpub.com) for its linguistic assistance during the preparation of this manuscript.

1. Exfoliation of graphite in a liquid phase
<ol>
	<li>Preparation of reagents
	<ol>
		<li>In a dry clean flat-bottom flask, add 20 g of polyvinyl alcohol (PVA), and then add 1,000 mL of distilled water. 
		NOTE: If the suspension was not processed to satisfaction, the step could be repeated to obtain an additional suspension.</li>
		<li>Gently swirl the flask until the PVA fully dissolves. 
		CAUTION: PVA is harmful to humans; thus, protective gloves and surgical&#160;masks should be used.</li>
		<li>Add 50 g of graphite powder to the flat-bottom flask, and gently swirl the flask until the graphite powder fully disperses in the suspension.</li>
		<li>Transfer 500 mL of the resulting suspension to a 500 mL beaker.</li>
		<li>Place the beaker under a shear mixer, positioning the beaker near the center of the mixing vessel to prevent the formation of a vortex. 
		NOTE: All chemical reagents used are of analytical grade.</li>
	</ol>
	</li>
	<li>Equipment setup
	<ol>
		<li>Lower the mixing head to its lowest position (30 mm from the base plane).</li>
		<li>Make a water bath by filling a 5,000 mL beaker with room temperature (25 &#176;C) water and position the 500 mL beaker in the bath. Change the water every 30 min.</li>
	</ol>
	</li>
	<li>Exfoliation
	<ol>
		<li>Start the mixer and increase the speed gradually to 4,500 rpm; mix at this speed for 120 min.</li>
		<li>Perform the exfoliation step five times for five predetermined times: 40 min, 60 min, 80 min, 100 min, and 120 min. The mixing time determines the lower lateral size limit of the graphene nanoflakes.</li>
		<li>Collect the suspensions after each exfoliation step. Each exfoliation step will generate a 500 mL suspension. Label each suspension with the exfoliation time for further treatment.</li>
		<li>Centrifuge the collected suspension at 140 x g for 45 min to remove the unexfoliated graphite.</li>
		<li>Collect the top 80% of the supernatant from each centrifuge tube for an additional centrifugation step.</li>
	</ol>
	</li>
</ol>
2. Centrifugation
<ol>
	<li>Centrifuge the resulting suspension at 8,951 x g for 45 min.</li>
	<li>Collect the upper 50% of the supernatant in the centrifuge tube, and label the sample with a number.</li>
	<li>Recycle the sediment on the bottom of the centrifuge tube from step 2.2. Add the PVA/water reagent prepared in step 1.1.1 to the sediments and shake the tube vigorously by hand until the sediment is well dispersed in the suspension.</li>
	<li>Centrifuge the suspension at 8,951 x g for 45 min; collect the upper 80% for further measurements.</li>
	<li>Repeat the abovementioned centrifugation step four times with four different centrifugation speeds: 5,035 x g, 2,238 x g, 560 x g, and 140 x g. The centrifugation speed determines the upper lateral size limit of the graphene nanoflakes. 
	NOTE: The protocol can be paused here.</li>
</ol>
3. Concentration measurements of the resulting nanofluids
<ol>
	<li>Obtain absorption spectra at a wavelength of 660 nm using ultraviolet-visible (UV-Vis) spectroscopy.
	<ol>
		<li>Use the PVA/water solution prepared in step 1.1.1 to calibrate a UV-Vis spectrometer; set the PVA/water concentrations to 0%.</li>
		<li>Add the PVA/water suspension to a dry clean sample cell with a path length of 10 mm and obtain a readout using the manufacturer&#8217;s software. Click the obtain button to get the measurement results graph and save the results.</li>
		<li>Repeat step 3.1.2 for each of the different samples prepared in step 2.5. 
		NOTE: The sample cell must be cleaned carefully with distilled water and dried before use each time.</li>
	</ol>
	</li>
	<li>Determine the graphene weight in the resulting suspension.
	<ol>
		<li>Vacuum filter the 100 mL sample suspension using a nylon membrane with a pore size of 0.2 &#181;m.</li>
		<li>Wash the membrane film with approximately 1,000 mL of water; repeat this step three times until all the solids are washed from the membrane.</li>
		<li>Determine the washed water mass with a high-precision microbalance to obtain the weight of the solids in the 100 mL suspension. 
		NOTE: The weights include both the weight of the graphene nanoflakes and the PVA polymers.</li>
		<li>Analyze the water with thermogravimetric analysis (TGA)18 to determine the PVA concentration.</li>
		<li>Calculate the mean extinction coefficient values of the PVA-stabilized system: 
		<img alt="Equation 1" src="/files/ftp_upload/59740/59740equ01.jpg" /> 
		where A is the absorbance measured at 660 nm using UV-Vis spectroscopy, and I is the path length travelled by the UV light during the measurement; the relationship between the absorbance A and the graphene concentration CG is linear. The extinction coefficient &#949; is the slope of the curve plotted for the absorbance A as a function of the graphene concentration CG. When the extinction coefficient &#949; is determined, CG can be determined by the absorbance A.</li>
	</ol>
	</li>
</ol>
4. Adjusting the concentration of resulting nanofluids
<ol>
	<li>Vacuum-filter the suspensions using a nylon membrane with a pore size of 0.2 &#181;m.</li>
	<li>Dry the membrane at room temperature for over 12 h.</li>
	<li>Subsequently, rinse the film with hot deionized water.</li>
	<li>Dry the deionized water under a vacuum for 24 h to obtain the graphene nanosheets. 
	NOTE: The production rate of graphene is approximately 1 mg/mL. If the desired concentration is lower than this, then it is easy to obtain it only by adding PVA/water. If the desired concentration is higher than 1%, then the drying process is necessary. Here, we demonstrate a condition with a desired concentration of 2%.</li>
	<li>Add the PVA/water solution or graphene nanosheets to adjust the concentration.</li>
	<li>If the desired concentration is less than the production rate, add the PVA/water solution prepared in step 1.1.1 to obtain the desired concentration.</li>
</ol>
5. Measuring the size distributions with dynamic light scattering
<ol>
	<li>Turn on the nanoparticle analyzer and adjust the detector to C label. Place the sample suspension on the test panel.</li>
	<li>Open the correlator control window software.</li>
	<li>Click Non-Negative Constrained least square: Multiple Pass in the menu.</li>
	<li>Set the elapsed time to 2 min.</li>
	<li>Select water as the solvent type.</li>
	<li>Change the diameter of the detector to 100 nm.</li>
	<li>Click the test button to obtain the readout and save the results.</li>
	<li>Repeat steps 5.1-5.7 for each of the samples prepared after step 4.</li>
</ol>

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The authors have nothing to disclose.

We have proposed a methodology for synthesizing graphene nanofluids with controllable flake size distributions. The method combines two procedures: exfoliation and centrifugation. Exfoliation controls the lower size limit of the nanoparticles, and centrifugation controls the upper size limit of the nanoparticles.
Although we employed liquid-phase exfoliation of graphite to produce graphene nanoparticles, the following modifications to the protocol should be considered. Additional exfoliation p...

Traditional methods used to synthesize graphene nanofluids often use sonication to disperse graphene powder1 in fluids, and sonication has been proven to change the size distribution of graphene nanoparticles2. Since the thermal conductivity of graphene depends on the flake length3,4, the synthesis of graphene nanofluids with controllable flake size distributions is vital to heat-transfer applications. Controlled centrifugation has been successfully applied to liquid exfoliated graphene dispersions to separate suspensions into fractions with different mean flake sizes5,6. Different terminal velocities used in centrifugation lead to different critical settling particle sizes7. The terminal velocity could be used to eliminate large graphene nanoparticles8.
Recently, size-controllable methods used to synthesize graphene via liquid-phase exfoliation have been introduced to overcome the fundamental problems encountered by conventional methods9,10,11,12,13. Liquid phase exfoliation of graphite has been proven to be an effective way to produce graphene suspensions14,15,16, and the underlying mechanism shows that the process parameters are related to the lower limits of the graphene nanoparticles size distributions. The graphene nanofluids were synthesized by the liquid exfoliation of the graphite with the help of surfactants17.While the lower limits of the graphene nanoparticle size distribution could be controlled by adjusting the parameters during the exfoliation, less attention is paid to the upper limits of the graphene nanoparticle size distribution.
The goal of this work is to develop a protocol that can be used to synthesize graphene nanofluids with controllable flake size distributions. Because exfoliation is responsible only for the lower size limit of the resulting graphene nanoflakes, additional centrifugation is introduced to control the upper size limit of the resulting graphene nanoflakes. However, the proposed method is not specific to graphene and could be appropriate for any other layered compounds that cannot be synthesized using traditional methods.

<table><tbody><tr><td>Beaker</td><td>China Jiangsu Mingtai Education Equipments Co., Ltd.</td><td>500 mL</td><td></td></tr><tr><td>Beaker</td><td>China Jiangsu Mingtai Education Equipments Co., Ltd.</td><td>5000 mL</td><td></td></tr><tr><td>Deionized water</td><td>Guangzhou Yafei Water Treatment Equipment Co., Ltd.</td><td></td><td>analytical grade</td></tr><tr><td>Electronic balance</td><td>Shanghai Puchun Co., Ltd.</td><td>JEa10001</td><td></td></tr><tr><td>Filter membrane</td><td>China Tianjin Jinteng Experiment Equipments Co., Ltd.</td><td>0.2 micron</td><td></td></tr><tr><td>Graphite powder</td><td>Tianjin Dengke chemical reagent Co., Ltd.</td><td></td><td>analytical grade</td></tr><tr><td>Hand gloves</td><td>China Jiangsu Mingtai Education Equipments Co., Ltd.</td><td></td><td></td></tr><tr><td>Laboratory shear mixer</td><td>Shanghai Specimen and Model Factory</td><td>jrj-300</td><td></td></tr><tr><td>Long neck flat bottom flask</td><td>China Jiangsu Mingtai Education Equipments Co., Ltd.</td><td>1000 ml</td><td></td></tr><tr><td>Nanoparticle analyzer</td><td>HORIBA, Ltd.</td><td>SZ-100Z</td><td></td></tr><tr><td>PVA</td><td>Shanghai Yingjia Industrial Development Co., Ltd.</td><td>1788</td><td>analytical grade</td></tr><tr><td>Raman spectrophotometer</td><td>HORIBA, Ltd.</td><td>Horiba LabRam 2</td><td></td></tr><tr><td>Scanning electron microscope</td><td>Zeiss Co., Ltd.</td><td>LEO1530VP</td><td>SEM</td></tr><tr><td>Surgical mask</td><td>China Jiangsu Mingtai Education Equipments Co., Ltd.</td><td>for one-time use</td><td></td></tr><tr><td>Thermal Gravimetric Analyzer</td><td>German NETZSCH Co., Ltd.</td><td>NETZSCH TG 209 F1 Libra</td><td>TGA analysis</td></tr><tr><td>Transmission electron microscope</td><td>Japan Electron Optics Laboratory Co., Ltd.</td><td>JEM-1400plus</td><td>TEM</td></tr><tr><td>UV-Vis spectrophotometer</td><td>Agilent Technologies, Inc.+BB2:B18</td><td>Varian Cary 60</td><td></td></tr><tr><td></td><td></td><td></td><td></td></tr><tr><td colspan="4">&lt;p class=&quot;jove_content&quot;&gt;Try the professional online HTML editor&lt;/p&gt;</td></tr></tbody></table>

synthesis of graphene nanofluids with controllable flake size distributions

A method for synthesizing graphene nanofluids with controllable flake size distributions is presented. Graphene nanoflakes can be obtained by the exfoliation of graphite in the liquid phase, and the exfoliation time is used to control the lower limits of the graphene nanoflake size distributions. Centrifugation is successfully used to control the upper limits of the nanoparticle size distributions. The objective of this work is to combine exfoliation and centrifugation to control the graphene nanoflake size distributions in the resulting suspensions.

The existence of graphene nanosheets can be validated by various characteristic techniques. Figure 1 shows the results of the UV-Vis measurement for the various flake size distributions produced by the abovementioned protocol. The spectra absorbance peak obtained at a wavelength of 270 nm is evidence of the graphene flakes. Different absorbances correspond to different concentrations. The lowest absorbance observed corresponds to the highest centrifugation speed. The spectra strongly confirm...

Watch this Scientific Journal Video about Synthesis of Graphene Nanofluids with Controllable Flake Size Distributions at JoVE.com

Synthesis of Graphene Nanofluids with Controllable Flake Size Distributions

A method for synthesizing graphene nanofluids with controllable flake size distributions is presented.

A method for synthesizing graphene nanofluids with controllable flake size distributions is presented. Graphene nanoflakes can be obtained by the ...

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6.6K Views.  South China University of Technology. A method for synthesizing graphene nanofluids with controllable flake size distributions is presented.

Video: Synthesis of Graphene Nanofluids with Controllable Flake Size Distributions

Simultaneous Synthesis of Single-walled Carbon Nanotubes and Graphene in a Magnetically-enhanced Arc Plasma

Carbon nanostructures such as single-walled carbon nanotubes (SWCNT) and graphene attract a deluge of interest of scholars nowadays due to their very promising application for molecular sensors, field effect transistor and super thin and flexible electronic devices1-4. Anodic arc discharge supported by the erosion of the anode material is one of the most practical and efficient methods, which can provide specific non-equilibrium processes and a high influx of carbon material to the developing structures at relatively higher temperature, and consequently the as-synthesized products have few structural defects and better crystallinity.
 To further improve the controllability and flexibility of the synthesis of carbon nanostructures in arc discharge, magnetic fields can be applied during the synthesis process according to the strong magnetic responses of arc plasmas. It was demonstrated that the magnetically-enhanced arc discharge can increase the average length of SWCNT 5, narrow the diameter distribution of metallic catalyst particles and carbon nanotubes 6, and change the ratio of metallic and semiconducting carbon nanotubes 7, as well as lead to graphene synthesis 8. 
 Furthermore, it is worthwhile to remark that when we introduce a non-uniform magnetic field with the component normal to the current in arc, the Lorentz force along the J&times;B direction can generate the plasmas jet and make effective delivery of carbon ion particles and heat flux to samples. As a result, large-scale graphene flakes and high-purity single-walled carbon nanotubes were simultaneously generated by such new magnetically-enhanced anodic arc method. Arc imaging, scanning electron microscope (SEM), transmission electron microscope (TEM) and Raman spectroscopy were employed to analyze the characterization of carbon nanostructures. These findings indicate a wide spectrum of opportunities to manipulate with the properties of nanostructures produced in plasmas by means of controlling the arc conditions.

Anodic arc discharge is one of the most practical and efficient methods to synthesize various carbon nanostructures. To increase the arc controllability and flexibility, a non-uniform magnetic field was introduced to process the one-step synthesis of large-scale graphene flakes and high-purity single-walled carbon nanotubes.

Carbon nanostructures such as single-walled carbon nanotubes (SWCNT) and graphene attract a deluge of interest of scholars nowadays due to their very ...

Bioengineering

Synthesis and Functionalization of 3D Nano-graphene Materials: Graphene Aerogels and Graphene Macro Assemblies

Efforts to assemble graphene into three-dimensional monolithic structures have been hampered by the high cost and poor processability of graphene. Additionally, most reported graphene assemblies are held together through physical interactions (e.g., van der Waals forces) rather than chemical bonds, which limit their mechanical strength and conductivity. This video method details recently developed strategies to fabricate mass-producible, graphene-based bulk materials derived from either polymer foams or single layer graphene oxide. These materials consist primarily of individual graphene sheets connected through covalently bound carbon linkers. They maintain the favorable properties of graphene such as high surface area and high electrical and thermal conductivity, combined with tunable pore morphology and exceptional mechanical strength and elasticity. This flexible synthetic method can be extended to the fabrication of polymer/carbon nanotube (CNT) and polymer/graphene oxide (GO) composite materials. Furthermore, additional post-synthetic functionalization with anthraquinone is described, which enables a dramatic increase in charge storage performance in supercapacitor applications.

This video method describes the synthesis of high surface area, monolithic 3D graphene-based materials derived from polymer precursors as well as single layer graphene oxide.

Efforts to assemble graphene into three-dimensional monolithic structures have been hampered by the high cost and poor processability of graphene. ...

Engineering

Millifluidics for Chemical Synthesis and Time-resolved Mechanistic Studies

Procedures utilizing millifluidic devices for chemical synthesis and time-resolved mechanistic studies are described by taking three examples. In the first, synthesis of ultra-small copper nanoclusters is described. The second example provides their utility for investigating time resolved kinetics of chemical reactions by analyzing gold nanoparticle formation using in situ X-ray absorption spectroscopy. The final example demonstrates continuous flow catalysis of reactions inside millifluidic channel coated with nanostructured catalyst.

Millifluidic devices are utilized for controlled synthesis of nanomaterials, time-resolved analysis of reaction mechanisms and continuous flow catalysis.

Procedures utilizing millifluidic devices for chemical synthesis and time-resolved mechanistic studies are described by taking three examples. In the ...

Preparation of Liquid-exfoliated Transition Metal Dichalcogenide Nanosheets with Controlled Size and Thickness: A State of the Art Protocol

We summarize recent advances in the production of liquid-exfoliated transition metal dichalcogenide (TMD) nanosheets with controlled size and thickness. Layered crystals of molybdenum disulphide (MoS2) and tungsten disulphide (WS2) are exfoliated in aqueous surfactant solution by sonication. This yields highly polydisperse mixtures containing nanosheets with broad size and thickness distributions. However, for most purposes, specific sizes (in terms of both lateral dimension and thickness) are required. For example, large and thin nanosheets are desired for (opto) electronic applications, while laterally small nanosheets are interesting for catalytic applications. Therefore, post-exfoliation size selection is an important step that we address here. We provide a detailed protocol on the efficient size selection in large quantities by liquid cascade centrifugation and the size and thickness quantification by statistical microscopic analysis (atomic force microscopy and transmission electron microscopy). The comparison of MoS2 and WS2 shows that both materials are size-selected in a similar way by the same procedure. Importantly, the dispersions of size-selected nanosheets show systematic changes in their optical extinction spectra with size due to edge and confinement effects. We show how these optical changes are related quantitatively to the nanosheets dimensions and describe how mean nanosheets length and layer number can be extracted reliably from the extinction spectra. The exfoliation and size selection protocol can be applied to a broad range of layered crystals as we have previously demonstrated for graphene, gallium sulphide (GaS) and black phosphorus.

A protocol for the liquid exfoliation of layered materials to nanosheets, their size selection and size measurement by microscopic and spectroscopic techniques is presented.

We summarize recent advances in the production of liquid-exfoliated transition metal dichalcogenide (TMD) nanosheets with controlled size and thickness. ...

Fabricating High-viscosity Droplets using Microfluidic Capillary Device with Phase-inversion Co-flow Structure

The generation of monodisperse droplets with high viscosity has always been a challenge in droplet microfluidics. Here, we demonstrate a phase-inversion co-flow device to generate uniform high-viscosity droplets in a low-viscosity fluid. The microfluidic capillary device has a common co-flow structure with its exit connecting to a wider tube. Elongated droplets of the low-viscosity fluid are first encapsulated by the high-viscosity fluid in the co-flow structure. As the elongated low-viscosity droplets flow through the exit, which is treated to be wetted by the low-viscosity fluid, phase inversion is then induced by the adhesion of the low viscosity droplets to the tip of the exit, which results in the subsequent inverse encapsulation of the high-viscosity fluid. The size of the resultant high-viscosity droplets can be adjusted by changing the flow rate ratio of the low-viscosity fluid to the high-viscosity fluid. We demonstrate several typical examples of the generation of high-viscosity droplets with a viscosity up to 11.9 Pas, such as glycerol, honey, starch, and polymer solution. The method provides a simple and straightforward approach to generate monodisperse high-viscosity droplets, which may be used in a variety of droplet-based applications, such as materials synthesis, drug delivery, cell assay, bioengineering, and food engineering.

A phase-inversion co-flow device is demonstrated to generate monodisperse high-viscosity droplets above 1 Pas, which is difficult to realize in droplet microfluidics.

The generation of monodisperse droplets with high viscosity has always been a challenge in droplet microfluidics. Here, we demonstrate a phase-inversion ...

Fabrication of Three-Dimensional Graphene-Based Polyhedrons via Origami-Like Self-Folding

The assembly of two-dimensional (2D) graphene into three-dimensional (3D) polyhedral structures while preserving the graphene's excellent inherent properties has been of great interest for the development of novel device applications. Here, fabrication of 3D, microscale, hollow polyhedrons (cubes) consisting of a few layers of 2D graphene or graphene oxide sheets via an origami-like self-folding process is described. This method involves the use of polymer frames and hinges, and aluminum oxide/chromium protection layers that reduce tensile, spatial, and surface tension stresses on the graphene-based membranes when the 2D nets are transformed into 3D cubes. The process offers control of the size and shape of the structures as well as parallel production. In addition, this approach allows the creation of surface modifications by metal patterning on each face of the 3D cubes. Raman spectroscopy studies show the method allows the preservation of the intrinsic properties of the graphene-based membranes, demonstrating the robustness of our method.

Fabrication of Three-Dimensional Graphene-Based Polyhedrons via Origami-Like Self-Folding

Here, we present a protocol for fabrication of 3D graphene-based polyhedrons via origami-like self-folding.

The assembly of two-dimensional (2D) graphene into three-dimensional (3D) polyhedral structures while preserving the graphene's excellent inherent ...

A Continuous-flow Photocatalytic Reactor for the Precisely Controlled Deposition of Metallic Nanoparticles

In this work, a novel photocatalytic reactor for the pulsed and controlled excitation of the photocatalyst and the precise deposition of metallic nanoparticles is developed. Guidelines for the replication of the reactor and its operation are provided in detail. Three different composite systems (Pt/graphene, Pt/TiO2, and Au/TiO2) with monodisperse and uniformly distributed particles are produced by this reactor, and the photodeposition mechanism, as well as the synthesis optimization strategy, are discussed. The synthesis methods and their technical aspects are described comprehensively. The role of the ultraviolet (UV) dose (in each excitation pulse) on the photodeposition process is investigated and the optimum values for each composite system are provided.

For a continuous and scalable synthesis of noble-metal-based nanocomposites, a novel photocatalytic reactor is developed and its structure, operation principles, and product quality optimization strategies are described.

In this work, a novel photocatalytic reactor for the pulsed and controlled excitation of the photocatalyst and the precise deposition of metallic ...

Microscopic Visualization of Porous Nanographenes Synthesized through a Combination of Solution and On-Surface Chemistry

On-surface synthesis has recently been regarded as a promising approach for the generation of new molecular structures. It has been particularly successful in the synthesis of graphene nanoribbons, nanographenes and intrinsically reactive and instable, yet attractive species. It is based on the combination of solution chemistry aimed at preparation of appropriate molecular precursors for further ultra-high vacuum surface assisted transformations. This approach also owes its success to an incredible development of characterization techniques, such as scanning tunneling/atomic force microscopy and related methods, which allow detailed, local characterization at atomic scale. While the surface-assisted synthesis can provide molecular nanostructures with outstanding precision, down to single atoms, it suffers from basing on metallic surfaces and often limited yield. Therefore, the extension of the approach away from metals and the struggle to increase productivity seem to be significant challenges toward wider applications. Herein, we demonstrate the on-surface synthesis approach for generation of non-planar nanographenes, which are synthesized through a combination of solution chemistry and sequential surface-assisted processes, together with the detailed characterization by scanning probe microscopy methods.

A combination of solution and surface assisted synthesis opens new directions in the atomically precise synthesis of nanostructures. Scanning tunneling microscopy (STM) supplemented by non-contact atomic force microscopy (nc-AFM) enables detailed characterization of newly designed and generated carbon-based nano-objects.

On-surface synthesis has recently been regarded as a promising approach for the generation of new molecular structures. It has been particularly ...

Stable Aqueous Suspensions of Manganese Ferrite Clusters with Tunable Nanoscale Dimension and Composition

Manganese ferrite clusters (MFCs) are spherical assemblies of tens to hundreds of primary nanocrystals whose magnetic properties are valuable in diverse applications. Here we describe how to form these materials in a hydrothermal process that permits the independent control of product cluster size (from 30 to 120 nm) and manganese content of the resulting material. Parameters such as the total amount of water added to the alcoholic reaction media and the ratio of manganese to iron precursor are important factors in achieving multiple types of MFC nanoscale products. A fast purification method uses magnetic separation to recover the materials making production of grams of magnetic nanomaterials quite efficient. We overcome the challenge of magnetic nanomaterial aggregation by applying highly charged sulfonate polymers to the surface of these nanomaterials yielding colloidally stable MFCs that remain non-aggregating even in highly saline environments. These non-aggregating, uniform, and tunable materials are excellent prospective materials for biomedical and environmental applications.

We report a one-pot hydrothermal synthesis of manganese ferrite clusters (MFCs) that offers independent control over material dimension and composition. Magnetic separation allows rapid purification while surface functionalization using sulfonated polymers ensures the materials are non-aggregating in biologically relevant medium. The resulting products are well positioned for biomedical applications.

Manganese ferrite clusters (MFCs) are spherical assemblies of tens to hundreds of primary nanocrystals whose magnetic properties are valuable in diverse ...

Asymmetrical Flow Field-Flow Fractionation for Sizing of Gold Nanoparticles in Suspension

Particle size is arguably the most important physico-chemical parameter associated with the notion of a nanoparticle. Precise knowledge of the size and size distribution of nanoparticles is of utmost importance for various applications. The size range is also important, as it defines the most &#8220;active&#8221; component of a nanoparticle dose.
Asymmetrical Flow Field-Flow Fractionation (AF4) is a powerful technique for sizing of particles in suspension in the size range of approximately 1&#8211;1000 nm. There are several ways to derive size information from an AF4 experiment. Besides coupling AF4 online with size-sensitive detectors based on the principles of Multi-Angle Light Scattering or Dynamic Light Scattering, there is also the possibility to correlate the size of a sample with its retention time using a well-established theoretical approach (FFF theory) or by comparing it with the retention times of well-defined particle size standards (external size calibration).
We here describe the development and in-house validation of a standard operating procedure (SOP) for sizing of an unknown gold nanoparticle sample by AF4 coupled with UV-vis detection using external size calibration with gold nanoparticle standards in the size range of 20&#8211;100 nm. This procedure provides a detailed description of the developed workflow including sample preparation, AF4 instrument setup and qualification, AF4 method development and fractionation of the unknown gold nanoparticle sample, as well as the correlation of the obtained results with the established external size calibration. The SOP described here was eventually successfully validated in the frame of an interlaboratory comparison study highlighting the excellent robustness and reliability of AF4 for sizing of nanoparticulate samples in suspension.

This protocol describes the use of Asymmetrical Flow Field-Flow Fractionation coupled with UV-vis detection for the determination of the size of an unknown gold nanoparticle sample.

Particle size is arguably the most important physico-chemical parameter associated with the notion of a nanoparticle. Precise knowledge of the size and ...

Synthesis of Graphene Nanofluids with Controllable Flake Size Distributions

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Fabrication of Three-Dimensional Graphene-Based Polyhedrons via Origami-Like Self-Folding

A Continuous-flow Photocatalytic Reactor for the Precisely Controlled Deposition of Metallic Nanoparticles

Microscopic Visualization of Porous Nanographenes Synthesized through a Combination of Solution and On-Surface Chemistry

Stable Aqueous Suspensions of Manganese Ferrite Clusters with Tunable Nanoscale Dimension and Composition

Asymmetrical Flow Field-Flow Fractionation for Sizing of Gold Nanoparticles in Suspension