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A novel Infinitesimal Columns (IC) simulation model is introduced in this study for the quantitativeanalysis of core-shell nanoparticles (CSNP) by means of XPS, which combines the advantages of exist-ing approaches. The IC model is applied to stabilised Lumidot™CdSe/ZnS 610 CSNP for an extensiveinvestigation of their internal structure, i.e. calculation of the two shell thicknesses (ZnS and stabiliser)and exploration of deviations from the idealised CSNP composition. The observed discrepancies betweendifferent model calculations can be attributed to the presence of excess stabiliser as well as synthesisresidues, demonstrating the necessity of sophisticated purification methods. An excellent agreement isfound in the comparison of the IC model with established models from the existing literature, the Shardmodel and the software SESSA.
The certified reference material BAM-L200, a nanoscale stripe pattern for length calibration and specification of lateral resolution, is described. BAM-L200 is prepared from a cross-sectioned epitaxially grown layer stack of AlxGa1–xAs and InxGa1–xAs on a GaAs substrate. The surface of BAM-L200 provides a flat pattern with stripe widths ranging down to 1 nm. Calibration distances, grating periods and stripe widths have been certified by TEM with traceability to the length unit. The combination of gratings, isolated narrow stripes and sharp edges of wide stripes offers plenty of options for the determination of lateral resolution, sharpness and calibration of length scale at selected settings of imaging surface-analytical instruments. The feasibility of the reference material for an analysis of the lateral resolution is demonstrated in detail by evaluation of ToF-SIMS, AES and EDX images. Other applications developed in the community are summarized, too. BAM-L200 fully supports the implementation of the revised International Standard ISO 18516 (in preparation) which is based on knowledge outlined in the Technical Report ISO/TR 19319:2013.
Loss in efficiency of perovskite solar cells may be caused by structural and/or chemical alterations of the complex layered system. SEM/EDX combined with XPS were chosen as appropriate methodical approach to characterise perovskite laboratory cells in depth and complementary on top, before and after light exposure. The layered perovskite system investigated here is based on glass covered with fluorine doped tin oxide (FTO), followed by three porous thin films of TiO2, ZrO2 and a thick monolithic carbon. This layered system serves as the matrix for the perovskite. After infiltration of perovskite solution and annealing, EDX spectral maps on cross-sections of the specimen have been measured. The distribution of relevant elements – Si, Sn, Ti, Zr and C – correlates conclusively with layers visible in the acquired SEM images. Lead and iodine are distributed throughout the porous layers C, ZrO2 and TiO2. By EDX it was found that several weeks of ambient daylight did not change significantly the qualitative elemental composition of lead and iodine throughout the solar cell system. It was confirmed with EDX that nanoparticles identified in high-resolution SEM micrographs contain mainly Pb and I, indicating these to be the perovskite
crystals. However, a time-dependent compositional and chemical altering was observed with XPS for the near-surface region of the outermost ~10 nm after two months of illumination.
Manufacturing of new perovskite layered solar cells with constant high light conversion Efficiency over time may be hampered by the loss of efficiency caused by structural and/or chemical alterations of the complex layered system. SEM/EDX combined with XPS were chosen as an appropriate methodical approach to characterize perovskite laboratory cells in depth and at surface, before and after light exposure. The layered perovskite system investigated here is based on glass covered with fluorine doped tin oxide, followed by thin films of TiO2, ZrO2, and a thick monolithic carbon. TiO2 film is subdivided into a dense layer covered by porous one constituted of nanoparticles of truncated bipyramidal shape. This layered system serves as the matrix for the perovskite. EDX spectral maps on cross sections of specimen have shown that Pb and I are distributed homogeneously throughout the porous layers C, ZrO2, and TiO2. SEM/EDX data show that 20 weeks of ambient daylight did not change significantly the in‐depth distribution of the elemental composition of Pb and I throughout the entire solar cell system. It was confirmed with EDX that nanoparticles identified in high‐resolution SEM micrographs contain mainly Pb and I, indicating these to be the perovskite crystals. However, a compositional and chemical altering began in the near‐surface region of the outermost ~10 nm after 2 months of illumination which was observed with XPS.
Hydrothermal synthesis of anatase TiO2 nanosheets with a high fraction of exposed {001} facets and related high photocatalytic activity - as an alternative to bipyramidal anatase TiO2 nanoparticles mainly exposing the {101} facets. The scope of the material preparation work is the thermal reduction of residual fluorides from HF (capping agent) induced during the synthesis of TiO2 nanosheets by calcination at 873K. The analytical task consists of detection and localization of fluorine present at the surface and/or in the bulk of TiO2 nanosheets before and after calcination by SEM/EDX, Auger electron spectroscopy and ToF-SIMS.
Parameters of TiO2 coatings can greatly influence their final performance in largescale applications such as photocatalytic measurements, orthopedic and/or dental prostheses, cell cultures, and dye-sensitized solar cells. From different film deposition procedures, self-assembly of TiO2 NPs in multiple layers was selected for systematic characterization. EDX, AES and ToF-SIMS analysis have been carried out in order to evaluate the functionalization of several types of TiO2 NPs differing in size, shape and surface area.
Control of functionalization of supports for subsequent assembly of titania nanoparticle films
(2018)
For self‐assembling of TiO2 nanoparticles in multiple layers by layer‐by‐layer deposition to be applied to TiO2 thin films with defined and homogeneous thickness for large‐scale applications, the proper functionalization of substrate surface is a prerequisite to guarantee sufficient adhesion.
The substrates selected and tested in the present paper were conductive, fluorine‐doped tin oxide (FTO) glass, nonconductive silica glass, and titanium alloy. The current study focusses on the analytical control of the stepwise functionalization of the substrates with 3‐aminopropyltriethoxysilane and glutaraldehyde (GA) for both the FTO glass and silica glass and with 3‐aminepropyl phosphonic acid and GA for Ti alloy. The analyses have been conducted by means of surface sensitive methods, X‐ray photoelectron spectroscopy, Auger electron spectroscopy, and time‐of‐flight secondary ions mass spectrometry. Chemical composition of surface of functionalized substrates shows differences in the degree and type of modification in dependence on substrate. It could be demonstrated that the best functionalized substrates were the conductive FTO glasses. The analysis of the functionalized Ti substrates has revealed that the surface coverage with 3‐aminepropyl phosphonic acid and GA molecules is an inhomogeneous one, and further optimization of the two‐step functionalization on the Ti alloy substrate is necessary.
The physico-chemical characteristics of TiO2 coatings can greatly influence their final performance. In SETNanoMetro, different deposition procedures are being set for applying films of TiO2 NPs with defined and homogenous thickness on supports of interest for the applications studied in the project. The selected substrates are the following: (i) Silica glasses for photocatalytic measurements, (ii) Ti-alloys for orthopedic and/or dental prostheses, and for cell cultures, and (iii) Conductive glasses (e.g. Fluorine doped Tin Oxide, FTO) for dye-sensitized solar cells. From the different film deposition procedures studied within the project Self-assembly of TiO2 NPs in multiple layers was selected. For this, surface modification of the substrate and of TiO2 nanoparticles (NPs) with e.g. silane coupling agents is a prerequisite. First attempts to prepare the self-assembled coating on the functionalized glass substrates seem to indicate that the functionalized NPs adhere to the substrates, even if the final coatings were not homogenous and presented agglomerates. ToF-SIMS results support this outcome.
In order to use the layer-by-layer deposition technique for the formation of TiO2 films by controlled self-assembly of the TiO2 NPs, the proper complementary moieties for the functionalization of the NPs were chosen. A first set of NPs has been produced by reaction with (3-aminopropyl)phosphonic acid (APPA) in order to functionalize the surface with free amino-groups. Then, the complementary NP set can be obtained from an aliquot of the first one, through the conversion of free surface amino-groups to aldehydes by reaction with glutaraldehyde. A proper approach for the functionalization of two types of TiO2, commercial P25 (Evonik) and SETNanoMetro-sample labelled UT001, with APPA was developed. A second set of NPs consisting of three types of TiO2 NPs, P25 and SETNanoMetro NPs (TiO2 NPs with high specific surface area > 150 m2/g and TiO2 NPs with low size < 20 nm) was functionalized with (3-aminopropyl)triethoxysilane (APTS). As for the previous set of NPs, the complementary NP set was obtained through the conversion of free surface amino-groups to aldehydes by reaction with glutaraldehyde. EDX, AES and ToF-SIMS spectra were collected and analyzed to demonstrate the presence of the surface functionalization of the different types of TiO2 NPs.
The synthesis of TiO2 nanoplatelets with fluorine-containing reactants is carried out using titanium (IV) butoxide as precursor and concentrated HF as shape controller, the final product requires a working up in order to eliminate or at least to reduce the amount of residual fluorides, which is realized here by well-defined thermal treatment of the samples. Bulk and surface sensitive methods namely scanning electron microscopy with energydispersive X-ray spectroscopy (SEM-EDX), Auger electron spectroscopy (AES) and time-of-flight secondary ion mass spectrometry (ToF-SIMS) have been applied to trace the presence of any fluorides in dependence on different information depths and measurement sensitivities of these methods.
Parameters of TiO2 coatings can greatly influence their final performance in largescale applications such as photocatalytic measurements, orthopedic and/or dental prostheses, cell cultures, and dye-sensitized solar cells. From different film deposition procedures, self-assembly of TiO2 NPs in multiple layers was selected for systematic characterization. EDX, AES and ToF-SIMS analysis have been carried out in order to evaluate the functionalization of several types of TiO2 NPs differing in size, shape and surface area.