News from the world of materials science: Graphene

Determination of functionalisation using XPS and HAXPES in one device

What is graphene?

Graphene is a single layer of carbon atoms arranged in a two-dimensional honeycomb lattice. It is often considered to be the basic building block for other carbon allotropes such as graphite, carbon nanotubes and fullerenes.

Graphene has become a focus of interest and research because of its remarkable properties

  • Exceptional electrical conductivity
  • Excellent thermal conductivity
  • Mechanical strength (harder than diamond)
  • Transparency
  • Flexibility
  • Impermeability
  • Large surface area

Graphene's unique properties are the subject of extensive research in a wide range of fields, including electronics, materials science, energy storage and biotechnology. Graphene has the potential to revolutionise a wide range of industries. However, there are still some challenges to large-scale production and integration into commercial products.

Some reasons for functionalised graphene layers

  • Tailoring electronic properties, e.g. applications in transistors, sensors and other electronic devices
  • Improving chemical reactivity, e.g. in catalysis and chemical sensing applications
  • Enhancing solubility, e.g. for easier processing and incorporation into various materials
  • Biological and medical applications, e.g. use in drug delivery systems, as biosensors or for medical imaging applications
  • Improving mechanical properties, e.g. for the development of stronger and more durable materials
  • Tuning thermal conductivity, e.g. for applications such as thermal interface materials and heat dissipation
  • Improving chemical stability, e.g. to increase stability and durability
  • Controlled drug release, e.g. for controlled and timed drug delivery
  • Gas sensor technology, e.g. for the production of selective and reactive sensors
  • Energy storage, e.g. to improve electrical conductivity and charge storage in batteries, supercapacitors and fuel cells.

Why functionalise graphene layers?

The functionalisation of graphene layers can serve several purposes and be useful for a variety of applications. Graphene is a single layer of carbon atoms arranged in a two-dimensional honeycomb lattice and is known for its remarkable properties, including high electrical and thermal conductivity, mechanical strength and flexibility. Functionalisation involves the application of various chemical groups or molecules to the surface of graphene, which can specifically alter its properties.

The specific reasons for functionalising graphene layers depend on the desired application and the properties to be achieved. It is important to choose the right functionalisation method and groups to achieve the desired results.

Composite materials

Development of stronger, lighter and more conductive materials for aerospace, automotive, construction, etc.

Energy storage

Development of stronger, lighter and more conductive materials for aerospace, automotive, construction, etc.


Increasing the efficiency of various catalytic processes

Conductive inks and coatings

Production of flexible and transparent conductive films for applications such as touch screens, solar panels and flexible electronic


Use in gas sensors, biosensors and other types of sensors

Water treatment

Absorption of impurities and salts, efficient water treatment design

Medical applications

Biocompatibility and the ability to transport medicines to specific locations

Anti-corrosion coatings

Extending the service life of various infrastructure components

Lubricant and polymer additives

Reduction of friction and wear in lubricants

What is functionalisation and what is the added value of using functionalised graphene?

Functionalised graphene refers to graphene sheets that have been chemically modified by adding different functional groups or molecules to their structure. This modification improves the properties and potential applications of graphene in various fields.

Some of the additional benefits of functionalised graphene are

  • Improved solubility
  • Better mechanical properties
  • Tailored electrical properties
  • Improved chemical reactivity
  • Biocompatibility
  • Optimised thermal properties
  • Gas barrier properties
  • Corrosion protection and coatings
  • Improved adsorption properties
  • Adaptability

The ability to customise functionalisation allows for a wide range of applications and the optimisation of graphene properties for specific requirements.

Why is the morphology of graphene layers important for functionalisation?

The morphology of graphene layers, including factors such as their size, shape, orientation and defects, plays a crucial role in the functionalisation process and can significantly influence the resulting properties and applications of functionalised graphene.

Please read the publication by our esteemed client Jörg Radnik et al. from BAM (Bundesanstalt für Materialforschung und -prüfung): "Influence of morphology on the functionalisation of graphene nanoplatelets analysed by comparative photoelectron spectroscopy with soft and hard X-rays".

The material analyses were carried out using the PHI Quantes, which, like the more advanced PHI Genesis, combines XPS and XAXPES in a single instrument.

Some of the main reasons why the morphology of graphene sheets is important for functionalisation

  • Surface area: The surface area of graphene sheets has a direct effect on the number of functional groups that can be attached. Larger surfaces provide more sites for functionalisation, which can lead to higher reactivity and greater functionality.

  • Accessibility: The orientation and stacking of the graphene layers can influence the accessibility of the functional groups to the graphene surface. In some cases, the layers can be densely stacked, limiting access to the graphene edges or basal planes for functionalisation. Optimising the morphology can ensure that the functional groups can reach the desired locations.

  • Defects: The presence of defects in graphene layers, such as vacancies, grain boundaries or edge sites, can serve as preferential sites for functionalisation. Defects can increase the chemical reactivity of graphene, making it more amenable to functionalisation. The control of defects can be important to tune the functionalisation process.

  • Layer thickness: The number of graphene layers in a material can affect its properties. For example, graphene with few layers or single layer graphene can have different electronic and optical properties than thicker graphene stacks. The morphology can be adjusted to achieve the desired layer thickness for specific applications.

  • Orientation and alignment: For some applications it is important that the graphene layers are well aligned or oriented. The morphology can be controlled to ensure that the functionalised graphene has the desired orientation, which is important for applications such as conductive films or electronic devices.

  • Uniformity: Uniform morphology in a graphene sample is important for consistency of functionalisation and subsequent performance. Irregularities in layer size or distribution can lead to variations in functionalisation efficiency and material properties.

  • Stability: Morphology can affect the stability of functionalised graphene. For example, the presence of defects can affect the long-term stability of the functional groups on the graphene surface. Careful control of the morphology can help to ensure the long-term stability of the functionalised material.

  • Specific applications: Different applications may require specific morphologies. For example, graphene oxide (GO) and reduced graphene oxide (rGO) have different morphologies and properties. GO has oxygen-containing functional groups and a layered structure, whereas rGO is a reduced form with fewer oxygen groups. The choice of morphology depends on the application.

  • Substrate compatibility: The choice of substrate or support for the graphene can influence the morphology. Functionalisation can be tailored to achieve compatibility with the substrate and ensure proper adhesion and performance.

In summary, the morphology of graphene layers plays a crucial role in the functionalisation of graphene. Tailoring the morphology to the specific requirements of an application can lead to improved functionalisation efficiency and produce graphene materials with enhanced properties and performance in various fields such as electronics, materials science, energy storage and others.