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Synthesis and Printing of 2D Materials

The increasing demand for electronic devices driven by the Internet-of-Things (IoT), environmental and health monitoring, radio-frequency indentification tags and antennas for tracking have propelled research in the field of printed electronics. A promising class of materials are the 2D materials, on one side, these single or few layer nanomaterials can be exfoliated in solution from their parent crystals, which makes them an ideal candidate to formulate them as ink which can be applied via printing and coating techniques. On the other side, a large number of 2D materials with exciting electro-optical properties have been discovered. The most common 2D material is graphene and its derivatives, followed by the transition matel dichalcogenides (TMDs), transition metal oxides/hydroxides, transition metal carbides/nitrides (MXenes), and 2D metal-organic frameworks. 

 

Our research:

The increasing We formulated inks from numerous 2D materials including graphene, and transition metal dichalcogenides, (MoS2, WS2,MoSe2, MoTe2). Printed 2D materials based devices include transistors, supercapacitors, and sensors for realizing accessible and affordable healthcare.

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From left to right: Slot-die coated graphene film on a PET substrate (size of the substrate: DIN-A5), graphene patterns by gravure and flexographic printing on glossy photo paper and PET, extrusion printed WSe2 on a PET substrate (scale bar: 1 cm).Reproduced from Ref [5] (CC-BY).

Additive-free functional inks for room-temperature fabrication of electronics

Conventional inks contain enormous amounts of additives such as binders and surfactant, which drastically degrade the electronic properties of the functional materials. To remove the additives and recover the electronic properties, high-temperature post-treatments (>300°C) are required, limiting the choice of materials (e.g., no heat sensitive material). Furthermore, conventional 2D material inks (e.g., graphene inks) are usually produced using hazardous solvents (e.g., NMP) and have low solid contents that complicates the fabrication process and increases the production cost/time. We developed a simple yet efficient method for processing pristine 2D materials into additive-free high-solid-content inks with diverse rheological properties for various printing and coating methods.

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Graphene inks optimized for different printing techniques: flexographic printing (left), screen printing (middle) and extrusion printing (right).

 

The inks are based on percolated 3D networks of 2D materials (e.g., graphene) in which a solvent is dispersed. Inks based on this novel concept show high colloidal stability, exhibit exceptional adhesion to a wide range of substrates, and are producible using almost any solvent (including green solvents).

 

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Binary X-ray tomogram (scale bar: 40 µm) and  SEM image (scale bar: 2 µm) of a freeze-dried graphene ink. Reproduced from Ref [5] (CC-BY).

 

Synthesis of a deep metastable emulsion of 2D materials


Additive-free 2D materials inks can be produced on kg scale with low cost and can have vast applications in printing of electronics or fabrication of functional devices.

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Schematics of the synthesis of deep metastable emulsions of 2D materials. The emulsions form the basis of ink preparation [4]. 
 
 
MXenes
A family of 2D transition metal carbides and nitrides known as MXenes has received increasing attention since the discovery of Ti3C2 in 2011. To date, about 30 different MXenes with well‐defined structures and properties have been synthesized and many more are theoretically predicted to exist. Due to the numerous assets including excellent mechanical properties, metallic conductivity, unique in‐plane anisotropic structure, tunable band gap and so on, MXenes rapidly positioned themselves at the forefront of the 2D materials world and have found numerous promising applications. Particular interest is devoted to applications in electrochemical energy storage, whereby 2D MXenes work either as electrodes, additives, separators, or hosts.
 
Our research:
By adjusting the material synthesis conditions and exfoliation processes, high-quality, single-layered MXene nanosheets can be produced with high concentration, forming highly viscous MXene aqueous or organic inks.
We apply Mxenes in
o Printed supercapacitors
o Catalysts for Nitrogenfixation
o Catalytic conversion of poysulfides in LiS batteries
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Image of an aqueous Mxene ink, SEM image of a printed interdigitated Mxene electrode and optical image of printed Mxene supercapacitors powering an LED. 
 

 

References: 

[1] S. Abdolhosseinzadeh et al., Additive Free MXene Sediment Inks for Screen‐Printed Micro-Supercapacitors. Adv. Mater. 2020, 2000716, https://doi.org/10.1002/adma.202000716

[2] S. Abdolhosseinzadeh et al., Coating Porous MXene Films with Tunable Porosity for High-Performance Solid-State Supercapacitors, ChemElectroChem 2021, 8, 1911, https://doi.org/10.1002/celc.202100558

[3] C. Zhang et al.,Two‐dimensional MXenes for lithium‐sulfur batteries. InfoMat, 2020, 1, https://doi.org/10.1002/inf2.12080

[4] Homogeneous emulsions and suspensions of 2-dimensional materials, Patent publication EP3848420A1

[5] S. Abdolhosseinzadeh et al., A Universal Approach for Room-temperature Printing and Coating of Two-dimensional Materials, Advanced Materials 2021, 2103660, https://doi.org/10.1002/adma.202103660

[6] Z. Zeng et al. Nanocellulose-MXene Biomimetic Aerogels with Orientation-Tunable Electromagnetic Interference Shielding Performance. Advanced Science, 2020, 2000979, https://doi.org/10.1002/advs.202000979