6.1 Oberflächen- und Dünnschichtanalyse
Filtern
Dokumenttyp
- Vortrag (221)
- Zeitschriftenartikel (196)
- Posterpräsentation (94)
- Forschungsdatensatz (26)
- Sonstiges (16)
- Beitrag zu einem Sammelband (10)
- Beitrag zu einem Tagungsband (7)
- Forschungsbericht (7)
- Handbuch (4)
- Sammelband (Herausgeberschaft für den kompletten Band) (2)
Sprache
- Englisch (588) (entfernen)
Schlagworte
- Nanoparticles (129)
- XPS (91)
- Electron microscopy (58)
- SEM (48)
- VAMAS (40)
- X-ray photoelectron spectroscopy (32)
- HAXPES (31)
- Particle size distribution (30)
- ToF-SIMS (27)
- NAP-XPS (23)
Organisationseinheit der BAM
- 6 Materialchemie (588)
- 6.1 Oberflächen- und Dünnschichtanalyse (588)
- 1 Analytische Chemie; Referenzmaterialien (52)
- 6.6 Physik und chemische Analytik der Polymere (45)
- 4 Material und Umwelt (32)
- 1.2 Biophotonik (27)
- 5 Werkstofftechnik (27)
- 6.3 Strukturanalytik (24)
- 6.7 Materialsynthese und Design (23)
- 6.2 Material- und Oberflächentechnologien (22)
Paper des Monats
- ja (7)
Recent years have seen increasing development of nanoparticles for applications in a wide range of fields, including but not limited to areas of great impact such as catalysis, medicine, energy, optoelectronics, cosmetics, and many others. In particular, nanoparticles bearing some form of coating layer, whether by design or due to incidental processes such as contamination or oxidation, are among the most commonly studied and utilised. In the characterisation of nanoparticles, the surface properties are of great importance, because a large proportion of the particle forms a part of the surface or interface. In the case of coated nanoparticles, the thickness of the coating is significant in determining the properties of the nanoparticle, and defines its interactions with its environment. Measurement of surface chemistry and coating thickness of nanoparticles is a challenge to which electron spectroscopies are well suited, due to high surface sensitivity, well-understood physical principles and accessibility.
Accurate and reproducible measurement of the structure and properties of high-value nanoparticles is extremely important for their commercialization. A significant proportion of engineered nanoparticle systems consist of some form of nominally core-shell structure, whether by design or unintentionally. Often, these do not form an ideal core-shell structure, with typical deviations including polydispersity of the core or shell, uneven or incomplete shells, noncentral cores, and others. Such systems may be created with or without intent, and in either case an understanding of the conditions for formation of such particles is desirable. Precise determination of the structure, composition, size, and shell thickness of such particles can prove challenging without the use of a suitable range of characterization techniques. Here, the authors present two such polymer core-shell nanoparticle systems, consisting of polytetrafluoroethylene cores coated with a range of thicknesses of either polymethylmethacrylate or polystyrene. By consideration of surface energy, it is shown that these particles are expected to possess distinctly differing coating structures, with the polystyrene coating being incomplete. A comprehensive characterization of these systems is demonstrated, using a selection of complementary techniques including scanning electron microscopy, scanning transmission electron microscopy, thermogravimetric analysis, dynamic light scattering, differential centrifugal sedimentation, and X-ray photoelectron spectroscopy. By combining the results provided by these techniques, it is possible to achieve superior characterization and understanding of the particle structure than could be obtained by considering results separately.
ISO Technical Report 23173 describes methods by which electron spectroscopies, including X-ray photoelectron spectroscopy (XPS), Auger electron spectroscopy (AES) and synchrotron techniques, can be employed to calculate the Coating thicknesses and compositions of nanoparticles. The document has been developed to review and outline the current state-of-the-art for such measurements. Such analyses of core–shell nanoparticles are common within the literature, however the
methods employed are varied; the relative advantages and disadvantages of These methods, and the optimal usage of each may not be clear to the general analyst. ISO Technical Report 23173 aims to clarify the methods that are available, describe them in clear terms, exhibit examples of their use, and highlight potential issues users may face. The information provided should allow analysts of electron spectroscopy data to make clear choices regarding the appropriate analysis of electron spectroscopy data from coated nanoparticle systems and provide a basis for understanding and comparing results from different methods and systems.
Before industrial grade graphene could reach comparable quality to the controlled laboratory scale material, many challenges must be overcome. In order to bridge the gap between lab-scale and industrial-scale production is necessary to develop processes, equipment and measurement procedures to control the material features. One of the most crucial reasons of graphene’s limited commercialization is the lack of standard procedures to properly characterize and define the material chemical and structural properties down to the nanometer level. This leads to many issues regarding material synthesis repeatability, inappropriateness choice of measurands and measurement reproducibility which heavily affect the consistency of the material performance. For example, among all the different industrially produced real-world graphene, it is crucial to determine how many layers of graphene build the material. Products that are built by more than 10 layers should be more correctly referred as nanosized graphite, a problem that is often regarded as the “fake graphene” issue.
In our study, a comparative analysis is performed on two different series (G5 and G6) of industrial graphene powders, each series produced with four types of functionalization: raw graphene, oxygen-functionalized, nitrogen-functionalized and fluorine-functionalized. All the 8 sample variants were analyzed from a chemical and morphological point of view in the form of powders prepared as slightly pressed in metallic sample holders.
The results of the comparative chemical analyses XPS and EDS show a good agreement in the concentration values for all the elements present in the samples, despite the different analysis volumes addressed by the two techniques. For this reason, the samples can be considered homogeneous in both lateral and vertical direction.
A clear influence of the morphology on the composition is evident. Therefore, such correlative measurements of morphology and composition are necessary for a comprehensive characterization of industrial graphene flakes. Protocols for reliable characterization of industrial graphene flakes are in progress.
The scientific and technological interest in graphene has been growing more and more in the late years due to its outstanding properties and diverse promising applications. However, graphene implementation into the industrial market is still limited and many challenges are yet to be addressed before this material can become suitable for the large-scale production. One of the most crucial challenge to overcome is to develop reliable and reproducible ways to characterize the material properties which can heavily affect the product performance. In our study the chemical composition of nine different samples of industrial graphene, graphene oxide and functionalized graphene were investigated. The samples were analysed both in form of powder and pellets. A comparative characterisation of the chemical composition was performed through X-ray Photoelectron Spectroscopy (XPS) and Energy Dispersive X-ray Spectroscopy (EDX). XPS depth resolution is in the order of 10 nm, while for EDX the analysis was performed at two different energy levels, i.e. 5 keV and 15 keV, and thus varying the analysis depth from 200 nm to 2000 nm. The XPS measurement area is 300x700 µm² while the EDX measurement was performed by analysing a grid of 25 locations (5x5) of 150 x 150 ?m2 area, covering the whole pellet surface of 5 mm diameter and then calculating the mean of the elemental concentration. The results of the elemental concentration values from XPS and EDX analyses show a good agreement for all the elements presents in the samples, despite the different spatial resolutions of the two techniques. Therefore, the samples appear homogeneous both in the lateral and vertical directions. The results relative to powder and pellets samples do not differ in a significant way except for a slight increase in the carbon content regarding the pellet samples, probably due to a minor contamination effect introduced through pressing. Nevertheless, pellets samples appear to be quite representative for the material while being much more convenient in terms of handling and safety compared to nano-powders and providing a regular flat surface for EDX analysis. Finally, this approach correlating XPS and EDS represents a simple, fast and reliable way for characterizing the chemical composition and the homogeneity of industrial graphene. This study is part of the project Standardisation of structural and chemical properties of graphene (ISO-G-SCoPe) which has received funding from the EMPIR programme co-financed by the Participating States and from the European Union?s Horizon 2020 research and innovation programme under Grant agreement No. 19NRM04.
The scientific and technological interest in graphene has been growing more and more in the late years due to its outstanding properties and diverse promising applications. However, graphene implementation into the industrial market is still limited and many challenges are yet to be addressed before this material can become suitable for the large-scale production. One of the most crucial challenge to overcome is to develop reliable and reproducible ways to characterize the material properties which can heavily affect the product performance. In our study the chemical composition of nine different samples of industrial graphene, graphene oxide and functionalized graphene were investigated. The samples were analysed both in form of powder and pellets. A comparative characterisation of the chemical composition was performed through X-ray Photoelectron Spectroscopy (XPS) and Energy Dispersive X-ray Spectroscopy (EDX). XPS depth resolution is in the order of 10 nm, while for EDX the analysis was performed at two different energy levels, i.e. 5 keV and 15 keV, and thus varying the analysis depth from 200 nm to 2000 nm. The XPS measurement area is 300x700 µm² while the EDX measurement was performed by analysing a grid of 25 locations (5x5) of 150 x 150 ?m2 area, covering the whole pellet surface of 5 mm diameter and then calculating the mean of the elemental concentration. The results of the elemental concentration values from XPS and EDX analyses show a good agreement for all the elements presents in the samples, despite the different spatial resolutions of the two techniques. Therefore, the samples appear homogeneous both in the lateral and vertical directions. The results relative to powder and pellets samples do not differ in a significant way except for a slight increase in the carbon content regarding the pellet samples, probably due to a minor contamination effect introduced through pressing. Nevertheless, pellets samples appear to be quite representative for the material while being much more convenient in terms of handling and safety compared to nano-powders and providing a regular flat surface for EDX analysis. Finally, this approach correlating XPS and EDS represents a simple, fast and reliable way for characterizing the chemical composition and the homogeneity of industrial graphene. This study is part of the project ?Standardisation of structural and chemical properties of graphene? (ISO-G-SCoPe) which has received funding from the EMPIR programme co-financed by the Participating States and from the European Union?s Horizon 2020 research and innovation programme under Grant agreement No. 19NRM04.
Since its discovery, graphene has got growing attention in the industrial and application research due to its unique properties . However, graphene has not been yet implemented into the industrial market, in particularly due to the difficulty of properly characterizing this challenging material. As most of other nanomaterials, graphene’s properties are closely linked to its chemical and structural properties, such as number of layers, flake thickness, degree of functionalisation and C/O ratio. For the commercialization, suitable procedures for the measurement and characterization of the ultrathin flakes, of lateral dimensions in the range from µm to tens of µm, are essential.Surface chemical methods, especially XPS, have an outstanding role of providing chemical information on the composition. Thereby, one well-known problem for surface analytical methods is the influence of contamination on the composition as in the case of adventitious carbon. The differentiation between carbon originated from the contamination or from the graphene sample itself is often not obvious, which can lead to altered results in the determination of the composition. To overcome this problem, Hard Energy X-ray Photoelectron Spectroscopy (HAXPES) offers new possibilities due to its higher information depth. Therefore, XPS measurement obtained with Al Kα radiation (E = 1486. 6 eV) were compared with analyses performed with a Cr Kα (E = 5414. 8 eV) excitation on functionalized graphene samples. Differences are discussed in terms of potential carbon contamination, but also of oxygen on the composition of the samples. Measurements are performed on O-, N- and F-functionalized graphene. Different preparation procedures (powder, pellet, drop cast from liquid suspension) will be also discussed, correlation of the results with the flakes morphology as well as their validation with other independent methods are in progress.
A comparative analysis is performed by XPS, HAXPES and SEM of industrial functionalised graphene powder of different morphology. The chemical analysis carried out by XPS, which probing depth is around 10nm, and HAXPES, which can reach up to 30nm probing depth. By combining these two techniques is possible to get a rough, non-destructive depth profiling of the sample's surface. The results show a higher concentration of the functionlisation elements on the surface of the sample and the influence of the morphology on the functionalisation process and the C/O ratio.
The presentation shows the results of the mini-interlaboratory comparison focused on the measurement of the morphology of graphene oxide flakes using scanning electron microscopy. In this work, a route for the sample preparation, SEM measurement and image analysis is proposed. The results of the image analysis, performed on 200+ flakes per sample, are presented by comparing the distributions of the size and shape descriptors calculated according to two different approaches. The influences of a different SEM measurement operator, analysis approach and analysis operator on the final size and shape distributions are highlighted.
Since its isolation, graphene has received growing attention from academia and industry due to its unique properties. However, the “what is my material” barrier hinders further commercialization. X-ray photoelectron spectroscopy (XPS) is considered as a method of choice for the determination of the elemental and chemical composition. In this work the influence of the morphology of graphene particles on the XPS results is studied and investigated as a function of X-ray energy, using conventional XPS with Al K𝜶 radiation and hard X-ray photoemission spectroscopy (HAXPES) using Cr K𝜶 radiation. Thereby, the information depth is varied between 10 and 30 nm. For this purpose, two commercial powders containing graphene nanoplatelets with lateral dimensions of either ≈100 nm or in the micrometer range are compared. These larger ones exist as stack of graphene layers which is inspected with scanning electron microscopy. Both kinds of particles are then functionalized with either oxygen or fluorine. The size of the graphene particles is found to influence the degree of functionalization. Only the combination of XPS and HAXPES allows to detect the functionalization at the outermost surface of the particles or even of the stacks and to provide new insights into the functionalization process.