The use of time-of-flight secondary ion mass spectrometry (SIMS) is of increasing interest for biological and medical applications due to its ability to provide chemical information on a submicrometer scale. However, the detection of larger biomolecules such as phospholipids and peptides is often inhibited by high fragmentation rates and low ionization efficiencies. One way to increase the secondary ion molecular yield is to chemically modify the surface using the matrix-enhanced SIMS approach, where an organic matrix is placed upon the surface. In this study, a Knudsen cell type matrix coater was developed in order to produce well-defined thicknesses of a matrix on a sample in order to study the effect of these matrix layers on the secondary ions. Using this technique, an order of magnitude enhancement of the useful ion yield for lipids was observed and clear enhancement of image contrast for lipids in brain tissue was demonstrated. The study shows that the layer thickness has a great influence on the emission of secondary ions, and therefore, its precise control is important for optimal yield enhancement.

In this study, the influence of two different cluster primary ions in laser secondary neutral mass spectrometry (Laser-SNMS) has been investigated. Despite the many advantages of Laser-SNMS, fragmentation of neutral organic molecules during both sputtering and photoionization has limited its efficiency for the study of large organic and biological molecules. Cluster ion sputtering, and in particular large argon gas cluster sputtering, has been proposed as a means of reducing this fragmentation. Molecules of 9-fluorenylmethoxycarbonyl-pentafluoro-l-phenylalanine were sputtered using Bi and Ar cluster primary ions, and the desorbed neutral species ("secondary neutrals") were postionized using a 7.87 eV vacuum ultraviolet laser light fluorine excimer laser. By varying timing parameters and laser power density, time-of-flight and laser power density distributions were obtained to investigate the fragmentation and energy distributions of the sputtered neutral species. Changing from 30 keV Bi sputtering to 10 keV Ar resulted in a significant reduction in fragmentation of the molecule as well as a suppression of the high background that results from metastable decay of highly excited ions, yielding significantly improved detection of the intact molecule and characteristic fragments. Analysis of the influence of laser power density and laser pulse delay time indicates a reduction of fragmentation in both the sputtering phase and the photoionization phase. This study demonstrates the importance of soft desorption for efficient laser postionization of large organic molecules and shows the potential for improving the efficiency of laser postionization by using large gas cluster ion sputtering.

Artificial lipid membranes play a growing role in technical applications such as biosensors in pharmacological research and as model systems in the investigation of biological lipid films. In the standard procedure for displaying the distribution of membrane components, fluorescence microscopy, the fluorophores used can influence the distribution of the components and usually not all substances can be displayed at the same time. The discriminant analysis-based algorithm used in combination with scanning time-of-flight secondary ion mass spectrometry (ToF-SIMS) enables marker-free, quantitative, simultaneous recording of all membrane components. These data are used for reconstruction of distribution patterns. In the model system used for this survey, a tear fluid lipid layer, the distribution patterns of all lipids correlate well in calculated ToF-SIMS images and epi-fluorescence microscopic images. All epi-fluorescence microscopically viewable structures are visible when using both positive and negative secondary ions and can be reproduced with high lateral resolution in the submicrometer range despite the very low signal intensity and a very low signal-to-noise ratio. In addition, three-dimensional images can be obtained with a subnanometer depth resolution. Furthermore, structures and the distribution of substances that cannot be made visible by epi-fluorescence microscopy can be displayed. This enables new insights that cannot be gained by epi-fluorescence microscopy alone.

Missions to planetary bodies require innovative techniques for the in situ investigation of their surfaces, especially when landings are planned. Therefore, Raman spectroscopy as an excellent laboratory tool for rapid mineralogical analysis of both terrestrial and extraterrestrial rocks has been successfully proposed for the investigation of planetary surfaces. Examples are the Raman laser spectrometer (RLS) of the joint ESA and Roscosmos mission ExoMars 2022 as well as Scanning Habitable Environments with Raman and Luminescence for Organics and Chemicals (SHERLOC) and SuperCam onboard NASA's Mars2020 Perseverance Rover; another is the Raman spectrometer for Martian Moons eXploration (MMX) (RAX), which is being developed for the in situ exploration of the Mars' moon Phobos. When preparing such space missions, it is essential to be prepared for all possible outcomes, such as samples exhibiting space weathering (SW). In this work, we study the influence of micrometeorite bombardment on bodies without atmosphere as one trigger of SW. This type of SW effect is simulated with an excimer laser irradiating the investigated samples with an energy density of $2.5 J/cm 2 for each pulse. As possible components on Phobos, we investigated the silicates olivine (Fo 91 ) and pyroxene (En 87 ) and their mixtures with Raman spectroscopy before and after laser irradiation. Surprisingly, the characteristic Raman bands of the individual minerals in the spectra are not influenced by this kind of SW. On the other hand, the fluorescence-dominated background signal induced by laser irradiation is reduced, possibly due to the formation of nanophase Fe, which then facilitates a better interpretation of the individual mineral peaks.

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