Gustavo Ferraz Trindade

Secondary ion mass spectrometry (SIMS) is increasingly used to study the surface and interfacial chemistry of battery materials owing to its ppm sensitivity and nanometer depth resolution. To support the community and help improve measurement quality, we measured the sputter yield volumes (SYVs) of a typical LiNi0.6Mn0.2Co0.2O2 (NMC622) cathode composed of compressed particles of active material on a foil current collector support. A time-of-flight (ToF)-SIMS instrument with an in situ atomic force microscope allowed accurate depth measurements giving an SYV for 2 keV Cs+ of 0.040 ± 0.005 nm3/ion and a SYV for 2 keV O2+ of 0.026 ± 0.003 nm3/ion. No evidence of SYV heterogeneity was found. We find that a previously reported sputter rate value in the literature is an order of magnitude lower, highlighting the need for better data. We also determined the Relative Sensitivity Factors (RSFs) for 2 keV O2+ sputtering with a 45° angle of incidence for a 50 keV Co+ implant with a fluence of 1 × 1015 ions/cm2 into silicon and graphite (carbon) as model anode materials. The RSF for silicon (Co+/Si+) is 1.5 ± 0.1 × 1022 atoms/cm3, and the RSF for graphite (carbon) (Co+/C+) is 2.8 ± 0.8 × 1020 atoms/cm3. For graphite, a correction was applied to the C+ signal in the region of the Co+ implant owing to enhanced C+ intensities caused by fragmentation of the carbon lattice.

Many biologically important molecules are structural isomers that share the same molecular mass yet differ in shape, bonding and function. This creates an ambiguity for mass spectrometry imaging (MSI), where chemically distinct species can be indistinguishable on the mass-to-charge ( m/z) scale and therefore cannot be reliably mapped in heterogeneous materials. Here we demonstrate that Orbitrap secondary ion mass spectrometry (OrbiSIMS) can provide an orthogonal contrast that enables both identification and spatial separation of isomeric molecules directly on surfaces. By exploiting structure-dependent secondary-ion dissociation and gas-phase collisional effects during ion transmission, we discriminate isomeric trisaccharides raffinose, maltotriose and melezitose and spatially resolve raffinose and maltotriose in mixtures. We benchmark these measurements against ion mobility spectrometry and observe consistent trends between OrbiSIMS transmission behaviour and ion mobility separation. These results establish OrbiSIMS as an approach for isomer-resolved MSI at surfaces and interfaces, opening opportunities to map isomeric biomolecules in complex systems where spatial distribution is central to function.

Orbitrap secondary ion mass spectrometry (OrbiSIMS) combines high-resolution mass analysis with surface- and depth-resolved chemical imaging, enabling confident molecular identification across a wide range of materials and biological systems. As the number of OrbiSIMS instruments in operation continues to grow, establishing reproducible and comparable performance across laboratories has become increasingly important. Here, we report the results of a Versailles Project on Advanced Materials and Standards (VAMAS) interlaboratory comparison designed to assess Orbitrap noise characteristics, detection limits, and intensity scale calibration in OrbiSIMS. Using replicated spectra acquired from a common silver reference sample across ten instruments worldwide, we quantify the noise structure of the Orbitrap analyzer and determine scaling parameters that convert arbitrary intensity units into true ion counts. The results confirm that Orbitrap noise behavior is governed by the total ion population in the trap and exhibits consistent characteristics across instruments and Orbitrap models operated below saturation. The ratio between the calibration scaling parameter and the detector noise parameter (A/σ) is shown to be largely intensity-independent in the linear regime, providing a robust metric for comparing instrument performance. From the measured noise properties, detection limits are estimated for each instrument, highlighting the influence of ion load and thresholding on analytical sensitivity. In addition, instrument-specific weighted sum of Rician (WSoR) noise models are derived and shown to yield consistent scaling behavior, enabling noise-unbiased multivariate statistical analysis and machine learning. Together, these results establish a metrological framework for reproducible OrbiSIMS measurements, support meaningful cross-laboratory comparison, and provide a foundation for future studies addressing Orbitrap linearity and performance across the full dynamic range required for advanced SIMS imaging and depth-profiling applications. The concepts and metrics introduced are directly applicable to Orbitrap mass spectrometry more broadly and are a foundation for a robust framework that can be incorporated into QA/QC workflows.

An integrated multimodal imaging workflow of cryogenic super-resolution fluorescence microscopy and soft X-ray tomography, Orbitrap secondary ion mass spectrometry, and inductively coupled plasma-mass spectrometry has revealed the unexpected targeting of a half-sandwich cyclopentadienyl Rh(III) phenylazopyridine anticancer complex to cellular lipid membranes and lipid droplets. The complex accumulates in plasma membranes with a surprisingly intense switch-on luminescence in living cancer cells, drives remodeling of lipid droplet architecture, and penetrates deeply into lipid-rich tissue environments. DFT modeling shows strong supramolecular interactions between the complex and glycerophosphorylcholine lipids.

Orbitrap mass spectrometry is widely used in the life-sciences. However, like all mass spectrometers, non-uniform (heteroscedastic) noise introduces bias in multivariate analysis complicating data interpretation. Here, we study the noise structure of an Orbitrap mass analyser integrated into a secondary ion mass spectrometer (OrbiSIMS). Using a stable primary ion beam to provide a well-controlled source of ions from a silver sample, we find that noise has three characteristic regimes: at low signals the Orbitrap detector noise and a censoring algorithm dominates; at intermediate signals counting noise specific to the ion emission process is most significant; and at high signals additional sources of measurement variation become important. Using this understanding, we developed a generative model for Orbitrap data that accounts for the noise distribution and introduce a scaling method, termed WSoR, to reduce the effects of noise bias in multivariate analysis. We compare WSoR performance with no-scaling and existing scaling methods for three biological imaging data sets including drosophila central nervous system, mouse testis and a desorption electrospray ionisation (DESI) image of a rat liver. WSoR consistently performed best at discriminating chemical information from noise. The performance of the other methods varied on a case-by-case basis, complicating the analysis.

Orbitrap secondary ion mass spectrometry (OrbiSIMS) is growing in popularity in a wide range of applications in life sciences and materials science, with the ability to provide high confidence in molecular identification simultaneously with high confidence in localisation (spatially at the microscale and at the nanoscale within a layer). In OrbiSIMS, transmission of secondary ions depends on two key parameters, the target voltage and helium gas pressure in a cooling cell. Here, we show that controlling these parameters gives OrbiSIMS the capability to couple phenomena that enable the separation of molecules based on their dissociation patterns and transmission after gas-phase collisions, which are related to molecular structure. We show that these phenomena can be leveraged and used analytically to take OrbiSIMS beyond the limitations of the mass scale and spatially resolve the signal of mixtures of structural isomeric trisaccharides (raffinose, maltotriose and melezitose). We benchmarked our results with ion mobility spectrometry and showed a correspondence between the methods to distinguish structural isomers. The ability to spatially resolve isomeric molecules in mixtures and on surfaces using OrbiSIMS can be transformative as these types of molecules play important biological roles.

Development of printed electronics requires understanding and control of the interfaces in heterostructure devices. However, investigation of the interfaces between dissimilar materials to achieve control of intermixing presents challenges. Here, we report investigation of interfaces in inkjet printed heterostructures by time-of-flight secondary ion mass spectrometry (ToF-SIMS), focused ion beam scanning electron microscopy (FIB-SEM), and energy dispersive X-ray (EDX) analysis to provide complementary insights into the intermixing phenomena. By examining various heterostructures of 0D (CsPbBr₃ nanocrystal), 2D (inkjet printed graphene, iGr), and polymeric (PEDOT:PSS) materials deposited with different printing parameters, we established the effect of ink composition and printing parameters on the intermixing depth. We demonstrated that in the heterostructures where the intermixing is dominated by layer porosity, the intermixing depth does not affect the electrical properties of the device, while intermixing by layer redispersion results in the decrease of the effective layer thickness accompanied by an increase of electrical resistance. The strategy for control over the interfacial composition and morphology in printed heterostructures could enable improved design and performance of printed devices.

Managing iodine formation is crucial for realising efficient and stable perovskite photovoltaics. Poly(3,4-ethylenedioxythiophene) polystyrene sulfonate (PEDOT:PSS) is a widely adopted hole transport material, particularly for perovskite solar cells (PSCs). However, Improving the performance and stability of PEDOT:PSS based perovskite optoelectronics remains a key challenge. We show that amine-containing organic cations de-dope PEDOT:PSS, causing performance loss, which is partially recovered with thiocyanate additives. However, this comes at the expense of device stability due to cyanogen formation from thiocyanate-iodine interaction which is accelerated in the presence of moisture. To mitigate this degradation pathway, we incorporate an iodine reductant in lead-tin PSCs. The resulting devices show an improved power conversion efficiency of 23.2% which is among the highest reported for lead-tin PSCs, and ~66% enhancement for the T_S80 lifetime under maximum power point tracking in ambient conditions. These findings offer insights for designing next-generation hole extraction materials for more efficient and stable PSCs.

Spray drying is one of the leading manufacturing methods for active pharmaceutical ingredients (APIs) owing to its rapid, single-step, and cost-effective nature. It also has the capacity to generate microspheres capable of controlled release of APIs including biomolecules and vaccines. However, one of the key challenges of spray-dried formulations especially with poly(lactic-co-glycolic acid) (PLGA)-based controlled-release injectables is burst release, where a significant fraction of the API is released prematurely within a short period of time following administration, leading to detrimental impact on the performance and quality of end products. This study uses a model API, bovine serum albumin (BSA) protein, to identify the sources of burst release that may affect the kinetics and performance of long-acting injectable microsphere formulations. Spray-dried microspheres with various formulations (i.e., variable BSA/PLGA ratios) were characterized in terms of their morphology, particle size, surface area, thermal properties, moisture content, as well as chemical compositions and their distributions to investigate the impact of spray drying on the burst release phenomenon. The results suggest that a relatively high initial release (85%) observed is mainly attributed to the protein distribution close to the particle surface. Morphology analysis provided evidence that the microspheres retained their spherical structure during the burst release phase. X-ray photoelectron spectroscopy, hard X-ray photoelectron spectroscopy, and argon cluster sputtering-assisted time-of-flight secondary ion mass spectrometry analysis suggest an enrichment of PLGA on particle surfaces with buried BSA protein. The statistically significant difference in particle size and surface area between three different formulations may be responsible for an initial variation in release but did not seem to alter the overall burst release profile. Considering the suggested source of burst release, the two-fluid spray-drying method, characterized by a single liquid feed delivering a preprepared emulsion, generated matrix-type microspheres with a surface layer of PLGA, as evidenced by surface analysis. The PLGA surface layer proved to be prone to degradation and pore formation, allowing for faster diffusion of BSA out of the microspheres, resulting in a burst release. Increasing the polymer concentration did not seem to halt this process.

OrbiSIMS is a secondary ion mass spectrometry method with dual mass analyzers: a time-of-flight (ToF) mass spectrometer for high-speed imaging and an Orbitrap™ for high mass resolving power and mass accuracy. Originally developed for biological imaging, there is now growing interest in the application to semiconductor materials to resolve peak interferences that obfuscate analysis in traditional SIMS depth profiling experiments. We use a new method to calibrate the Orbitrap intensity scale to true counts, which allows comparison of the useful yield and duty cycle with a magnetic sector instrument and a time-of-flight instrument using an Sb implant in the silicon sample. The useful yield of the Orbitrap and magnetic sector instruments (for one detected peak) are similar. However, since the magnetic sector instrument has serial mass detection, its useful yield reduces as more peaks are analyzed. While the ToF instrument has parallel detection, it has a low duty cycle and the useful yield is two orders of magnitude lower for 1000 eV Cs+ sputtering. The depth resolution was also compared from the measurement of the downslope from depth profiles of an Sb delta multilayer. For 1000 eV Cs+ sputtering, the downslopes are 3.9, 2.3, and 2.7 nm/decade for Orbitrap, magnetic sector, and ToF instruments, respectively. Ion trajectory simulation shows that the poorer depth resolution of the OrbiSIMS is in part due to ion beam distortion at low energy.