Article
Impact of PHI TOF-SIMS instruments on scientific discovery
The Physical Electronics nanoTOF TOF-SIMS instrument proves to be a versatile tool for surface analysis. We reflect on 2023 in our review, highlighting the nanoTOF’s widespread applications across various disciplines from battery1-3 and solar cell4-5 development to environmental science6 and biology7 as well as material development8-9, tribology10 and more. Here we will spotlight several groups who have used the nanoTOF in diverse ways to solve some vastly different problems.
Researchers at Maastricht University have studied a series of anti-cancer drugs containing Os(II) and Ru(II) arene complexes11. Previous development of these drugs using phosphine ligands revealed challenges including low anti-cancer activity. However, using stibine and arsine co-ligands, they succeeded in increasing the anti-cancer activity of the Os(II) and Ru(II) complexes. In the positive ion mode, the researchers were able to confirm the structure of the ligand complexes by leveraging the PHI nanoTOF's unique tandem MS capabilities, allowing them to identify organo-metallic fragmentation patterns and match isotopic patterns of the heavy metal ions (Figure 1). The role of the nanoTOF TOF-SIMS instrument was highlighted in the investigation of this highly promising class anti-cancer complexes.
Figure 1 - TOF-SIMS spectra showing tandem MS fragmentation and heavy metal isotope distribution patterns.
The imaging capabilities of the nanoTOF are also frequently used to monitor the stability of innovative technologies, and here we will briefly sample a few different studies that utilized TOF-SIMS imaging. At the Beijing Institute of Technology, researchers tested new perovskite solar cell films by observing the difference in aggregation of lithium compounds between the different films by mapping the lithium ions before and after aging5 (Figure 2). Researchers at Nanjing University have used the nanoTOF II to monitor the corrosion of a β-Fe2O3 photoanode used in seawater electrolysis by monitoring the accumulation of chloride ions12 (Figure 3), and at Case Western University, a nanoTOF TRIFT V was used to image contamination of chromatographic stationary phase particles, and to confirm the restoration of the particles after chemical treatment13 (Figure 4).
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Figure 2 - TOF-SIMS images of lithium ion in a perovskite solar cell film before and after. |
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| Figure 3 - TOF-SIMS images of Cl and 18 OH content in a β-Fe2O3 photoanode before and after degradation. |
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Figure 4 - TOF-SIMS images of chlorine contamination on chromatography stationary phase particles before and after chemical cleaning. |
| Finally, nanoTOF instrumentation can be used to provide chemical and elemental information beyond the surface of a sample by sputtering with a variety of ion beams to collect a depth profile. Once such example in 2023 is from the Laboratoire Interdisciplinaire Carnot de Bourgogne (ICB) in Dijon, France14. ICB researchers are developing a method to remove toxic synthetic dyes from wastewater using the photocatalytic properties of titanium dioxide (TiO2). However, the photocatalytic activity of TiO2 is hindered by charge photocarrier recombination and limited UV absorption. To overcome these limitations, they have synthesized photocatalysts using atomic layer deposition to deposit Au nanoparticles onto a TiO2 film. Flat silicon wafers or spherical spherical polystyrene beads were used as the substrate, and these synthetic photocatalysts showed a 300% increase in the degradation of the toxic dyes as compared to natural degradation. During the development of these photocatalysts, the nanoTOF II was used to characterize the distribution of gold, titanium oxide, and silicon below the surface of the materials (Figure 5). Using the depth profiling capabilities, they were able to show that the flat wafers contained a thin layer of Au nanoparticles on the surface (Figure 5a) and the photocatalysts grown on polystyrene beads contained Au nanoparticles at the surface of the particles as well as in the voids between the beads and the silicon substrate (Figure 5b). |
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Figure 5 - Depth profile of TiO2-Au flat wafer (a) and spherical bead (b). |
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