Graphene Nanoplatelets Synthesized and Dispersed via Probe-Sonication

Graphene nanoplatelets (GNPs) can be synthesized and dispersed with high efficiency and reliability using sonicators. High-intensity ultrasonication is employed to exfoliate graphite and obtain few-layer graphene, often referred to as graphene nanoplatelets. Sonication also excels in achieving excellent graphene nanoplatelet distribution in both low and highly viscous suspensions.

Graphene Nanoplatelet ProcessingSuperior Results with Sonication

For graphene nanoplatelet processing, probe-type sonicators are most efficient, reliable and easy-to-use tool. Since ultrasonication can be applied for synthesis, dispersion and functionalization of graphene nanoplatelets, sonicators are used for numerous graphene-related applications:

  • Exfoliation and Synthesis Probe-type sonicators are used to exfoliate graphite into few-layer graphene or graphene nanoplatelets. The high-intensity ultrasonication disrupts the interlayer forces and breaks down the graphite into smaller, individual sheets of graphene.
  • Dispersion: Achieving uniform dispersion of graphene nanoplatelets in a liquid medium is crucial for all graphene-related applications. Probe-type sonicators can disperse the nanoplatelets evenly throughout the liquid, preventing agglomeration and ensuring a stable suspension.
  • Functionalization: Sonication facilitates the functionalization of graphene nanoplatelets by promoting the attachment of functional groups or molecules to their surfaces. This functionalization enhances their compatibility with specific polymers or materials.

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Ultrasonic disperser MultiSonoReactor with 16,000 watts dispersing capacity for mixing of graphene nano-platelets into expoy resins or cement.

Ultrasonic dispersion system for the industrial inline dispersion of graphene nanoplatelets

Graphene Nanoplatelet Synthesis via Sonication

Graphene nanoplatelets can be synthesized by ultrasonically-assisted graphite exfoliation. Therefore, a graphite suspension is sonicated using a probe-type ultrasonic homogenizer. This procedure has been tested with very low (e.g. 4wt% or lower) to high solid (e.g. 10wt% or higher) concentrations.
 
Ghanem and Rehim (2018) report the ultrasonic exfoliation of graphite in water with the aid of sodium dodecyl benzene sulfonate (SDS) in order to prepare dispersed graphene nanoplatelets using a the probe-type sonicator UP 100H allowed for the successful preparation of defect-free few-layer graphene (>5). The following precursor was used: reduced graphene nanosheets were prepared via Hummer method and treated with two additional steps, oxidation of graphite followed by reduction of graphene oxide. Thereby, dispersed graphene nanoplatelets were obtained in water via solvent dispersion method (see scheme below). Graphite layers were exfoliated with sonication using the probe-type sonicator UP100H (100 W). 0.25 g SDS was dissolved in 150 mL deionized water and then 0.5 g of graphite was added. The graphite solution was sonicated for 12h in an ice bath and then the suspension solution was centrifuged at 686× g for 30 min to remove the large particles. The precipitate was discarded and supernatant was re-centrifuged for 90 min at 12,600× g. The obtained dispersed graphene nanoplatelets were washed well several times to get rid of the surfactant. Finally, the product was dried at 60ºC under vacuum.

Defect-free few-layer stacked graphene nanoplatelets are produced via sonication

High resolution transmission electron microscope images of graphene nanosheets obtained
via ultrasonically-assisted aqueous phase dispersion and Hummer method.
(Study and graphic: Ghanem and Rehim, 2018)

 

Ultrasonically synthesized nanofluids are efficient coolants and heat exchanger liquids. Thermoconductive nanomaterials such as graphene nanoplatelets increase heat transfer and heat dissipation capacity significantly. Sonication is well established in the synthesis and functionalization of thermoconductive nanoparticles such as graphene nanoplatelets.

Dispersing CNTs in Polyethylene Glycol (PEG) - Hielscher Ultrasonics

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What is the Difference between Graphene Sheets and Nanoplatelets?

Graphene sheets and graphene nanoplatelets are both nanomaterials composed of graphene, which is a single layer of carbon atoms arranged in a hexagonal lattice. Sometimes, graphene sheets and graphene nanoplatelets are used as interchangeable terms. But scientifically, there are a few differences between these graphene nanomaterials: The primary difference between graphene sheets and graphene nanoplatelets lies in their structure and thickness. Graphene sheets consist of a single layer of carbon atoms and are exceptionally thin, while graphene nanoplatelets are thicker and composed of multiple stacked graphene layers. These structural differences can impact their properties and suitability for specific applications. The use of probe-type sonicators is a highly effective and efficient technique to synthesize, disperse, and functionalize graphene single-layer graphene sheets as well as few-layer stacked graphene nanoplatelets.

Graphite exfoliation using the probe-type sonicator UP100H gave pristine graphene nanoplatelets

Graphic visualizing the ultrasonic synthesis of graphene nanoplatelets using the sonicator UP100H
(Study and graphic: Ghanem and Rehim, 2018)

Probe-type ultrasonicator UP400St for nanoparticle dispersion such as graphene nanoplatelets in a stable aqueous suspension.

Probe-type sonicator UP400St for the preparation of graphene nanoplatelet dispersions

Dispersion of Graphene Nanoplatelets using Sonication

The uniform dispersion of graphene nanoplatelets (GNPs) is crucial in various applications because it directly impacts the properties and performance of the resulting materials or products. Therefore, sonicators are installed for graphene nanoplatelet dispersions in various industries. The following industries are prominent examples for the use of power-ultrasound:
 

  • Nano-composites: Graphene nanoplatelets can be incorporated into various nanocomposite materials, such as polymers, to enhance their mechanical, electrical, and thermal properties. Probe-type sonicators aid in uniformly dispersing the nanoplatelets within the polymer matrix, resulting in improved material performance.
  • Electrodes and Batteries: Graphene nanoplatelets are used in the development of high-performance electrodes for batteries and supercapacitors. Sonication helps create well-dispersed graphene-based electrode materials with increased surface area, which improves energy storage capabilities.
  • Catalysis: Sonication can be used to prepare catalytic materials based on graphene nanoplatelets. The uniform dispersion of catalytic nanoparticles on the graphene surface can enhance catalytic activity in various reactions.
  • Sensors: Graphene nanoplatelets can be employed in the fabrication of sensors for various applications, including gas sensing, biosensing, and environmental monitoring. Sonication ensures homogeneous distribution of the nanoplatelets in sensor materials, leading to improved sensitivity and performance.
  • Coatings and Films: Probe-type sonicators are used to prepare graphene nanoplatelet-based coatings and films for applications in electronics, aerospace, and protective coatings. Uniform dispersion and proper adhesion to substrates are crucial for these applications.
  • Biomedical Applications: In biomedical applications, graphene nanoplatelets can be used for drug delivery, imaging, and tissue engineering. Sonication helps in the preparation of graphene-based nanoparticles and composites used in these applications.
Graphene nanoplatelets can be successfully synthesized and dispersed via ultrasonic processing.

SEM images of graphene nanoplatelets at (b) X3000 and (c) X8000
(Study and images: ©Alizadeh et al., 2018)

Ultrasonically synthesized nanofluids are efficient coolants and heat exchanger liquids. Thermoconductive nanomaterials increase heat transfer and heat dissipation capacity significantly. Sonication is well established in the synthesis and functionalization of thermoconductive nanoparticles as well as the production of stable high-performant nanofluids for cooling applications.

Dispersing CNTs in Polyethylene Glycol (PEG)

Video Miniature

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Science-Proven Results for Ultrasonic Graphene Nanoplatelet Dispersions

Scientists have used Hielscher sonicators for the synthesis and dispersion of graphene nanoplatelets in numerous studies and tested the effects of ultrasonication vigorously. Below, you can find a few examples for the successful mixing of graphene nanoplatelets into different mixtures such as aqueous slurries, expoy resins or mortar.
 
A common procedure for the reliable, quick an uniform dispersion of graphene nanoplatelets is the following procedure:
For dispersion, the graphene nanoplatelets were sonicated within pure acetone using the Hielscher ultrasonic mixer UP400S for almost one hour in order to prevent an agglomeration of graphene sheets. Acetone was completely removed by evaporation. Then, the graphene nanoplatelets were added at 1 wt % of the epoxy system and were sonicated in the epoxy resin at 90W for 15 minutes.
(cf. Cakir et al., 2016)
 
Another study investigates the reinforcement of ionic liquid-based nanofluids (ionanofluids) by adding graphene nanoplatelets. For superior dispersion, the mixture of graphene nanoplatelets, ionic liquid and sodium dodecyl benzene sulfonate was homogenized using the Hielscher probe-type sonicator UP200S for around 90 min.
(cf. Alizadeh et al., 2018)

 
Tragazikis et al. (2019) report the effective incorporation of graphene nanoplatelets into mortar. Therefore, aqueous graphene suspensions were produced by addition of nanoplatelets – at weights inscribed by the desirable target contents in the resultant materials – in mixtures of regular tap water and plasticizer and subsequent magnetic stirring for 2 min. The suspensions were homogenized by ultrasonication for 90 min at room temperature, using a Hielscher UP400S device (Hielscher Ultrasonics GmbH) equipped with a 22mm-sonotrode delivering a power throughput of 4500 J/min at a frequency of 24 kHz. The specific combination of energy rate and sonication duration was established as optimum following a meticulous investigation of the effect of ultrasonication parameters of suspension quality.
(cf. Tragazikis et al., 2019)
 
Zainal et al. (2018) state in their research that a proper dispersion technique such as sonication ensures that nanomaterials such as graphene nanoplatetelets can enhance the properties of infill materials. This is due to the fact that dispersion is one of the most important factors for the production of high-quality nanocomposites such as epoxy grout.

Graphene nanoplatelets enhance the thermal characteristics of ionic nanofluids. For best dispersion results, the nanoplatelets were dispersed ultrasonically into the nanofluid using the Hielscher probe-type sonicator UP400S

Sample of pure BMIM-PF6 (left) and ultrasonically prepared ionanofluid at 2% wt. (right).
(Study and images: ©Alizadeh et al., 2018)

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High-Performance Sonicators for Graphene Nanoplatelet Processing

Hielscher Ultrasonics is the market leader when it comes to high-performance ultrasonicators for nanomaterial processing. Hielscher probe-type sonicators are used worldwide in laboratories and industrial settings for various applications, including the processing of graphene nanoplatelets.
State-of-the-art technology, German craftsmanship and engineering as well as long-time technical experience make Hielscher Ultrasonics your preferred partner for succesful ultrasonic application.

Why Hielscher Ultrasonics?

  • high efficiency
  • state-of-the-art technology
  • reliability & robustness
  • adjustable, precise process control
  • batch & inline
  • for any volume
  • intelligent software
  • smart features (e.g., programmable, data protocolling, remote control)
  • easy and safe to operate
  • lav vedligeholdelse
  • CIP (clean-in-place)

Design, Manufacturing and ConsultingQuality Made in Germany

Hielscher ultrasonicators are well-known for their highest quality and design standards. Robustness and easy operation allow the smooth integration of our ultrasonicators into industrial facilities. Rough conditions and demanding environments are easily handled by Hielscher ultrasonicators.

Hielscher Ultrasonics is an ISO certified company and put special emphasis on high-performance ultrasonicators featuring state-of-the-art technology and user-friendliness. Of course, Hielscher ultrasonicators are CE compliant and meet the requirements of UL, CSA and RoHs.

Nedenstående tabel giver dig en indikation af den omtrentlige behandlingskapacitet for vores ultralydapparater:

Batch volumenFlowhastighedAnbefalede enheder
0.5 to 1.5mLn.a.VialTweeter
1 til 500 ml10 til 200 ml/minUP100H
10 til 2000 ml20 til 400 ml/minUP200Ht, UP400St
0.1 til 20L0.2 til 4 l/minUIP2000hdT
10 til 100L2 til 10 l/minUIP4000hdT
15 to 150L3 to 15L/minUIP6000hdT
n.a.10 til 100 l/minUIP16000
n.a.Størreklynge af UIP16000

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Facts Worth Knowing

Graphene Sheets vs Graphene Nanoplatelets

Both, graphene sheets and graphene nanoplatelets are graphite-derived nanostructures. The table below highlights the most prominent differences between graphene sheets and graphene nanoplatelets.
 

DifferentiationGraphene SheetsGraphene Nanoplatelets
StructureGraphene sheets are typically single layers of graphene with a two-dimensional structure. They can be very large and continuous, extending over macroscopic areas.Graphene nanoplatelets are smaller and thicker compared to individual graphene sheets. They consist of multiple layers of graphene stacked on top of each other, forming platelet-like structures. The number of layers in a nanoplatelet can vary, but it is typically in the range of a few to several dozen layers
ThicknessThese are single-layer graphene structures, so they are extremely thin, typically just one atom thick.These are thicker than single-layer graphene sheets because they consist of multiple graphene layers stacked together. The thickness of graphene nanoplatelets depends on the number of layers they contain.
PropertiesSingle-layer graphene sheets have exceptional properties, such as high electrical conductivity, thermal conductivity, and mechanical strength. They also exhibit unique electronic properties, like quantum confinement effects.Graphene nanoplatelets retain some of the excellent properties of graphene, such as high electrical and thermal conductivity, but they may not be as exceptional as single-layer graphene in these aspects due to the presence of multiple layers. However, they still offer advantages over traditional carbon materials.
ApplicationsSingle-layer graphene sheets have a wide range of potential applications, including in electronics, nanocomposites, sensors, and more. They are often used for their exceptional electronic properties.Graphene nanoplatelets are used in various applications, such as reinforcing materials in composites, lubricants, energy storage devices, and as additives to improve the properties of other materials. Their thicker structure makes them easier to disperse in certain matrices compared to single-layer graphene.

High performance ultrasonics! The Hielscher product range covers the full spectrum from the compact lab ultrasonicator over bench-top units to full-industrial ultrasonic systems.

Hielscher Ultrasonics manufactures high-performance ultrasonic homogenizers from lab to industrial size.


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