Secondary Ion Mass Spectrometry Analysis Research Articles

Selective depression mechanism of polyaspartic acid and calcium oxide on arsenopyrite after copper ions activation and its effect on flotation separation performance

The arsenopyrite activated by copper ions have similar flotation properties to chalcopyrite. Polyaspartic acid (PASP) and calcium oxide (CaO) using as combination depressants for the selective separation of copper-activated arsenopyrite and chalcopyrite were carried out by micro-flotation experiments, contact angle measurements, surface adsorption capacity tests, zeta potential measurements, X-ray photoelectron spectroscopy (XPS) analyses, inductively coupled plasma-optical emission spectrometer (ICP-OES) tests and time-of-flight secondary ion mass spectrometry (ToF-SIMS) analyses, and its depression mechanism was investigated. The results of flotation experiments showed that the recovery of arsenopyrite after addition of the depressants reached only 7.80 %, while the recovery of chalcopyrite reached 94.02 %. The results of contact angles, adsorption capacity tests and zeta potential measurements showed that the PASP-CaO can selectively enhance the hydrophilicity of arsenopyrite surface, but has little effect on the chalcopyrite. XPS analyses and ICP-OES tests further verified that the depressants first eliminated the activation of copper ions and then selectively adsorbed on the surface of arsenopyrite. ToF-SIMS analyses showed that the PASP-CaO would achieve selective depression of arsenopyrite in the form of PASP, PASP-Ca complexes and Ca(OH)+, respectively. Finally, the mechanism diagram of PASP-CaO selectively depressing arsenopyrite was derived. These results will provide an excellent theoretical reference for the flotation separation of copper arsenic sulfide ore.

Investigations of In2O3 Added SiC Semiconductive Thin Films and Manufacture of a Heterojunction Diode

This study involved direct doping of In2O3 into silicon carbide (SiC) powder, resulting in 8.0 at% In-doped SiC powder. Subsequently, heating at 500 °C was performed to form a target, followed by the utilization of electron beam (e-beam) technology to deposit the In-doped SiC thin films with the thickness of approximately 189.8 nm. The first breakthrough of this research was the successful deposition of using e-beam technology. The second breakthrough involved utilizing various tools to analyze the physical and electrical properties of In-doped SiC thin films. Hall effect measurement was used to measure the resistivity, mobility, and carrier concentration and confirm its n-type semiconductor nature. The uniform dispersion of In ions in SiC was as confirmed by electron microscopy energy-dispersive spectroscopy and secondary ion mass spectrometry analyses. The Tauc Plot method was employed to determine the Eg values of pure SiC and In-doped SiC thin films. Semiconductor parameter analyzer was used to measure the conductivity and the I-V characteristics of devices in In-doped SiC thin films. Furthermore, the third finding demonstrated that In2O3-doped SiC thin films exhibited remarkable current density. X-ray photoelectron spectroscopy and Gaussian-resolved spectra further confirmed a significant relationship between conductivity and oxygen vacancy concentration. Lastly, depositing these In-doped SiC thin films onto p-type silicon substrates etched with buffered oxide etchant resulted in the formation of heterojunction p-n junction. This junction exhibited the rectifying characteristics of a diode, with sample current values in the vicinity of 102 mA, breakdown voltage at approximately −5.23 V, and open-circuit voltage around 1.56 V. This underscores the potential of In-doped SiC thin films for various semiconductor devices.

Extreme shifts in pyrite sulfur isotope compositions reveal the path to bonanza gold

Pyrite is the most common sulfide mineral in hydrothermal ore-forming systems. The ubiquity and abundance of pyrite, combined with its ability to record and preserve a history of fluid evolution in crustal environments, make it an ideal mineral for studying the genesis of hydrothermal ore deposits, including those that host critical metals. However, with the exception of boiling, few studies have been able to directly link changes in pyrite chemistry to the processes responsible for bonanza-style gold mineralization. Here, we report the results of high-resolution secondary-ion mass spectrometry and electron microprobe analyses conducted on pyrite from the Brucejack epithermal gold deposit, British Columbia. Our δ34S and trace element results reveal that the Brucejack hydrothermal system experienced abrupt fluctuations in fluid chemistry, which preceded and ultimately coincided with the onset of ultra-high-grade mineralization. We argue that these fluctuations, which include the occurrence of extraordinarily negative δ34S values (e.g., -36.1‰) in zones of auriferous, arsenian pyrite, followed by sharp increases of δ34S values in syn-electrum zones of nonarsenian pyrite, were caused by vigorous, fault valve-induced episodic boiling (flashing) and subsequent inundation of the hydrothermal system by seawater. We conclude that the influx of seawater was the essential step to forming bonanza-grade electrum mineralization by triggering, through the addition of cationic flocculants and cooling, the aggregation of colloidal gold suspensions. Moreover, our study demonstrates the efficacy of employing high-resolution, in situ analytical techniques to map out individual ore-forming events in a hydrothermal system.

Multiple sources of water preserved in impact glasses from Chang'e-5 lunar soil.

The existence of molecular H2O and evolution of solar wind-derived water on the lunar surface remain controversial. We report that large amounts of OH and molecular H2O related to solar wind and other multiple sources are preserved in impact glasses from Chang'e-5 (CE5) lunar soil based on reflectance infrared spectroscopy and nanoscale secondary ion mass spectrometry analyses. The estimated water content contributed by impact glasses to CE5 lunar soil was ~72 ppm, including molecular H2O of up to 15 to 25 ppm. Our studies revealed that impact glasses are the main carrier of molecular H2O in lunar soils. Moreover, water in CE5 impact glasses provides a record of complex formation processes and multiple water sources, including water derived from solar wind, deposited by water-bearing meteorites/micrometeorites, and inherited from lunar indigenous water. Our study provides a better understanding of the evolution of surficial water on airless bodies and identifies potential source and storage pathways for water in the terrestrial planets.

Highly 28Si enriched silicon by localised focused ion beam implantation

Solid-state spin qubits within silicon crystals at mK temperatures show great promise in the realisation of a fully scalable quantum computation platform. Qubit coherence times are limited in natural silicon owing to coupling to the 29Si isotope which has a non-zero nuclear spin. This work presents a method for the depletion of 29Si in localised volumes of natural silicon wafers by irradiation using a 45 keV 28Si focused ion beam with fluences above 1 × 1019 ions cm−2. Nanoscale secondary ion mass spectrometry analysis of the irradiated volumes shows residual 29Si concentration down to 2.3 ± 0.7 ppm and with residual C and O comparable to the background concentration in the unimplanted wafer. After annealing, transmission electron microscopy lattice images confirm the solid phase epitaxial re-crystallization of the as-implanted amorphous enriched volume extending over 200 nm in depth.

Understanding the Solid-Electrolyte-Interface (SEI) Formation in Glyme Electrolyte Using Time-Of-Flight Secondary Ion Mass Spectrometry (ToF-SIMS).

Lithium-ion batteries are commonly used for energy storage due to their long lifespan and high energy density, but the use of unsafe electrolytes poses significant health and safety concerns. An alternative source is necessary to maintain electrochemical efficacy. This research demonstrates new safe glyme-based electrolytes for silica/carbon (SiOx/C) nanocomposite derived from Australian rice husk (RH). The quality of SiOx/C was preserved by using deep eutectic solvent-based pre-treatment and single-step carbonization, which was confirmed through the X-ray analysis of the crystalline phase of silica. The electrochemical assessment of SiOx/C anode using various glyme-based electrolytes for LIBs was carried out. Among them, the resultant half cells based on diglyme electrolyte is superior to others with the first discharge capacity at 1274 mAh/g and a reversible discharge capacity of 759.7 mAh/g. Ex-situ SEM and Time-of-Flight Secondary Ion Mass Spectrometry (ToF- SIMS) analysis of the electrode indicated that diglyme not only improves the capacity but also sustains the electrode architecture for longer cycle life with more LiF-based components and also showed the absence of HF components. Importantly, the addition of fluoroethylene carbonate (FEC) additive enhanced the cycling stability. These results provide a new perspective on developing advanced SiOx/C anode using glyme electrolytes for Li-ion batteries.

Quantitative analysis of molecular interactions in κ-carrageenan-Isovanillin biocomposite for biodegradable packaging and pharmaceutical applications using NMR, TOF-SIMS, and XPS approach

This study explores the molecular interactions and structural changes in κ-carrageenan crosslinked with isovanillin to create a biocomposite material suitable for hard capsule and bio-degradable packaging applications. Proton Nuclear Magnetic Resonance (1H NMR) spectroscopy revealed chemical changes in the conjugate molecule, indicating improved electronegativity due to intermolecular hydrogen bonding between κ-carrageenan and isovanillin. Time-of-flight Secondary Ion Mass Spectrometry (ToF-SIMS) analysis revealed enhanced ion intensity due to intermolecular interactions, particularly between sulphate and hydrogen ions. X-ray Photoelectron Spectroscopy (XPS) study demonstrated that κ-carrageenan and isovanillin form stronger hydrogen bonds, with a shift in binding energy indicating higher electronegativity. These findings shed light on the molecular mechanisms that underpin the formation of the biocomposite material, as well as its potential for use in hard capsule and biodegradable packaging materials, addressing the need for sustainable alternatives in the pharmaceutical and packaging industries while also contributing to environmental conservation.

Utilizing phosphonyl carboxylic acid copolymer as an efficient depressant for flotation separation of chalcopyrite from galena: Experimental and DFT study

The research proposes an innovative galena depressant, known as Phosphonyl carboxylic acid copolymer (POCA), to enhance the efficiency of flotation separation between chalcopyrite and galena. Mineral flotation tests were conducted to investigate the flotation performance of chalcopyrite and galena. The inhibition mechanism of POCA on galena was studied using multiple characterization techniques including Inductively Coupled Plasma Optical Emission Spectrometer (ICP-OES) testing, Zeta potential testing, X-ray photoelectron spectroscopy (XPS) analysis, atomic force microscopy (AFM) testing, contact angle testing, time-of-flight secondary ion mass spectrometry (ToF-SIMS) analysis, and density functional theory (DFT) calculations. In the flotation test, at a concentration of 10 mg/L sodium butyl xanthate (SBX) and pH 9, adding 50 mg/L POCA can reduce the flotation recovery of galena from 83.50 % to below 5 %, whereas the recovery of chalcopyrite was almost influenced. The testing conducted via ICP-OES revealed that POCA promotes the dissolution of Pb2+ from the galena surface. The adsorption of POCA on the galena surface was confirmed through zeta potential testing, XPS testing, contact angle, AFM testing, and ToF-SIMS analysis, it was noted that POCA exhibited high levels of adsorption on the galena surface. Density Functional Theory (DFT) calculations suggest that the chemical interaction between the sulfonic acid present in POCA and the Pb2+ active site of galena is regarded as the primary inhibition mechanism.

Geochemistry and volatile contents of olivine-hosted melt inclusions from Mt. Etna tholeiitic and alkaline magmatism

The analysis of olivine-hosted melt inclusions (MIs) from the whole sub-alkaline and alkaline magmatic suites of Mt. Etna provides fundamental information about the composition of undifferentiated magmas and their pristine volatile content. Olivine crystals (Fo88-66) were selected for Secondary Ion Mass Spectrometry (SIMS) analysis of volatile species (H2O, CO2, F, Cl and S) contained in their host MIs, after preliminary high-pressure/high-temperature re-homogenization, which allowed to reduce the developing of cracks in the host olivine and diffusion-driven outgassing of volatiles from the melt inclusions. This permitted to explore the compositional variability of volatiles of undifferentiated melts and the degassing behavior through the feeding system. The studied MIs show significant major elements compositional heterogeneities (44.57–52.37 wt% SiO2; 3.60–7.51 wt% Na2O + K2O). Fractionation modelling was performed with Rhyolite-MELTs under variable fO2 regimes (∆FMQ + 1.5 to + 3), starting from the less evolved MIs compositions and ultimately reproducing most of the observed compositional trends. Mantle melting modelling was used to replicate the observed MIs composition, starting from a spinel-lherzolitic source, accounting for the alkalinity and Fe content of reproduced melts by varying the eutectic contribution of Amph/Phlog and Opx/Cpx respectively. Although most of the studied MIs were degassed in an open-conduit regime, the observed range of volatile concentration in MIs (2.42–6.14 wt% H2O; 308–8474 ppm CO2; 132–697 ppm F; 221–1766 ppm Cl and 16–1992 ppm S) is correlated with a slight decrease in the molar H2O/(H2O + CO2) ratio from early tholeiites to the recent 2015 alkaline products. This observation allows to estimate a minimum 12,250 ppm CO2 and a maximum of 6.14 wt% H2O in primary melts of the current activity.

Ge doping of α-Ga2O3 thin films via mist chemical vapor deposition and their application in Schottky barrier diodes

We performed Ge doping of α-Ga2O3 thin films grown on m-plane sapphire substrates using mist chemical vapor deposition. Although the typical growth rate was high at 4 μm/h, the resultant α-Ga2O3 thin films exhibited high crystallinity. We controlled the carrier density in the range of 8.2 × 1016–1.6 × 1019 cm−3 using bis[2-carboxyethylgermanium(IV)]sesquioxide as the Ge source. The highest mobility achieved was 66 cm2 V−1 s−1 at a carrier concentration of 6.3 × 1017 cm−3. Through secondary ion mass spectrometry analysis, a linear relationship between the Ge concentration in the α-Ga2O3 thin films and the molar ratio of Ge to Ga in the source solution was established. The quasi-vertical Schottky barrier diode fabricated using the Ge-doped α-Ga2O3 thin films exhibited an on-resistance of 7.6 mΩ cm2 and a rectification ratio of 1010. These results highlight the good performance of the fabricated device and the significant potential of Ge-doped α-Ga2O3 for power-device applications.

Demystifying the Semiconductor‐to‐Metal Transition in Amorphous Vanadium Pentoxide: The Role of Substrate/Thin Film Interfaces

AbstractThe precise mechanism governing the reversible semiconductor‐to‐metal transition (SMT) in V2O5 remains elusive, yet its investigation is of paramount importance due to the remarkable potential of V2O5 as a versatile “smart” material in advancing optoelectronics, plasmonics, and photonics. In this study, distinctive experimental insights into the SMT occurring in amorphous V2O5 through the application of highly sensitive, temperature‐dependent, in situ analyses on a V2O5 thin film deposited on soda‐lime glass are presented. The ellipsometry measurements reveal that the complete SMT occurs at ≈340 °C. Remarkably, the refractive index and extinction coefficients exhibit reversible characteristics across visible and near‐infrared wavelengths, underscoring the switch‐like behavior inherent to V2O5. The findings obtained from ellipsometry are substantiated by calorimetry and in situ secondary ion mass spectrometry analyses. In situ electron microscopy observations unveil a separation of oxidation states within V2O5 at 320 °C, despite the thin film retaining its amorphous state. The comprehensive experimental investigations effectively demonstrate that alterations in electronic state can trigger the SMT in amorphous V2O5. It is revealed for the first time that the SMT in V2O5 is solely contingent upon electronic state changes, independent of structural transitions, and importantly, it is a reversible transformation within the amorphous state itself.

Reliable operation of Cr2O3:Mg/β-Ga2O3 p–n heterojunction diodes at 600 °C

Beta gallium oxide (β-Ga2O3)-based semiconductor heterojunctions have recently demonstrated improved performance at high voltages and elevated temperatures and are, thus, promising for applications in power electronic devices and harsh environment sensors. However, the long-term reliability of these ultra-wideband gap (UWBG) semiconductor devices remains barely addressed and may be strongly influenced by chemical reactions at the p–n heterojunction interface. Here, we experimentally demonstrate operation and evaluate the reliability of Cr2O3:Mg/β-Ga2O3 p–n heterojunction diodes during extended operation at 600 °C, as well as after 30 repeated cycles between 25 and 550 °C. The calculated pO2-temperature phase stability diagram of the Ga-Cr-O material system predicts that Ga2O3 and Cr2O3 should remain thermodynamically stable in contact with each other over a wide range of oxygen pressures and operating temperatures. The fabricated Cr2O3:Mg/β-Ga2O3 p–n heterojunction diodes show room-temperature on/off ratios >104 at ±5 V and a breakdown voltage (VBr) of −390 V. The leakage current increases with increasing temperature up to 600 °C, which is attributed to Poole–Frenkel emission with a trap barrier height of 0.19 eV. Over the course of a 140-h thermal soak at 600 °C, both the device turn-on voltage and on-state resistance increase from 1.08 V and 5.34 mΩ cm2 to 1.59 V and 7.1 mΩ cm2, respectively. This increase is attributed to the accumulation of Mg and MgO at the Cr2O3/Ga2O3 interface as observed from the time-of-flight secondary ion mass spectrometry analysis. These findings inform future design strategies of UWBG semiconductor devices for harsh environment operation and underscore the need for further reliability assessments for β-Ga2O3-based devices.

Growth of Spontaneous Nucleation AlN Crystals by Al-Base Alloy Evaporation in Nitrogen Atmosphere

Aluminum nitride (AlN) crystals with areas ranging from 1 mm2 to 2 mm2 were successfully grown through spontaneous nucleation at 1700 °C using a modified vapor transport method. In this approach, Cu–Al alloy served as the source of aluminum (Al), and nitrogen (N2) was employed as the nitrogen source. The morphology and crystalline quality of the AlN crystals were characterized by a stereo microscope, Raman spectrometer, photoluminescence (PL) and secondary-ion mass spectrometry (SIMS). Deposited on the graphite lid, the as-grown AlN crystals exhibited both rectangular and hexagonal shapes, identified as m-plane and c-plane AlN, respectively, based on Raman spectroscopy. The full width half maximum (FWHM) values of E2 (high) for the rectangular and hexagonal grains were measured to be 6.00 cm−1 and 6.06 cm−1, respectively, indicating high crystalline quality. However, PL and SIMS analysis indicated the presence of impurities associated with oxygen in the crystals. This paper elucidates the growth mechanism of the modified vapor transport method and highlights the role of the Cu–Al alloy in sustaining reactions at lower temperatures. The addition of copper (Cu) not only facilitates sustainable reactions, but also provides a novel perspective for the growth of AlN single crystals.

Enhancement of vertical phase separation in sequentially deposited organic photovoltaics through the independent processing of additives

Herein, the impact of the independent control of processing additives on vertical phase separation in sequentially deposited (SD) organic photovoltaics (OPVs) and its subsequent effects on charge carrier kinetics at the electron donor-acceptor interface are investigated. The film morphology exhibits notable variations, significantly depending on the layer to which 1,8-diiodooctane (DIO) was applied. Grazing incidence wide-angle X-ray scattering analysis reveals distinctly separated donor/acceptor phases and vertical crystallinity details in SD films. Time-of-flight secondary ion mass spectrometry analysis is employed to obtain component distributions in diverse vertical phase structures of SD films depending on additive control. In addition, nanosecond transient absorption spectroscopy shows that DIO control significantly affects the dynamics of separated charges in SD films. In SD OPVs, DIO appears to act through distinct mechanisms with minimal restriction, depending on the applied layer. This study emphasizes the significance of morphological optimization in improving device performance and underscores the importance of independent additive control in the advancement of OPV technology.

Dissolved organic carbon spurs bacterial-algal competition and phosphorus-paucity adaptation: Boosting Microcystis' phosphorus uptake capacity

Dissolved organic carbon (DOC) can alter the availability of background nutrients by affecting the proliferation of heterotrophic bacteria, which exerts a notable influence on algal growth and metabolism. However, the mechanism of how allochthonous DOC (aDOC) precipitates shifts in bacterial-algal interactions and modulates the occurrence of cyanobacteria blooms remains inadequately elucidated. Therefore, this study investigated the relationship between bacteria and algae under aDOC stimulation. We found that excess aDOC triggered the breakdown and reestablishment of the equilibrium between Microcystis and heterotrophic bacteria. The rapid proliferation of heterotrophic bacteria led to a dramatic decrease in soluble phosphorus and thereby resulted in the inhibition of the Microcystis growth. When the available DOC was depleted, the rapid death of heterotrophic bacteria released large amounts of dissolved phosphorus, which provided sufficient nutrients for the recovery of Microcystis. Notably, Microcystis rejuvenated and showed higher cell density compared to the carbon-absent group. This phenomenon can be ascribed that Microcystis regulated the compositions of extracellular polymeric substances (EPS) and the expression of relevant proteins to adapt to a nutrient-limited environment. Using time of flight secondary ion mass spectrometry (TOF-SIM) and proteomic analysis, we observed an enhancement of the signal of organic matter and metal ions associated with P complexation in EPS. Moreover, Microcystis upregulated proteins related to organic phosphorus transformation to increase the availability of phosphorus in various forms. In summary, this study emphasized the role of DOC in algal blooms, revealing the underestimated enhancement of Microcystis nutrient utilization through DOC-induced heterotrophic competition and providing valuable insights into eutrophication management and control.

Upside–Down Annealing of Oxide Thin‐Film Transistors and its Analysis Using Hydrogen‐Diffusion Model

Hydrogen plays a crucial role in controlling the electrical characteristics of oxide thin‐film transistors (TFTs). The conductivity of the semiconductor can be modulated by controlling the amount of hydrogen in the active layer. In this study, a thermal annealing of the sample in an inverted orientation (referred to as “upside‐down annealing”) is introduced. The impact of this approach on the hydrogen content within the In2O3 active layer is examined through the lens of a hydrogen diffusion model. By time‐of‐flight secondary ion mass spectrometry analysis, a hydrogen diffusion model for the TFT is established, and it is demonstrated that upside–down annealing is an effective method for preventing hydrogen depletion caused by out‐diffusion. A bottom‐gate bottom‐contact TFT is fabricated to analyze electrical characteristics. By employing different post‐thermal annealing methods on the device, it is discovered that the upside–down annealing enhances the device's performance significantly up to mobility of 22.3 cm2 V−1 s−1, which surpasses more than twice the mobility achieved with the traditionally oriented, “straight” annealed TFT.

Bridging New Observational Capabilities and Process-Level Simulation: Insights into Aerosol Roles in the Earth System

Abstract The spatial distribution of ambient aerosol particles significantly impacts aerosol–radiation–cloud interactions, which contribute to the largest uncertainty in global anthropogenic radiative forcing estimations. However, the atmospheric boundary layer and lower free troposphere have not been adequately sampled in terms of spatiotemporal resolution, hindering a comprehensive characterization of various atmospheric processes and impeding our understanding of the Earth system. To address this research data gap, we have leveraged the development of uncrewed aerial systems (UAS) and advanced measurement techniques to obtain mesoscale spatial data on aerosol microphysical and optical properties around the U.S. Southern Great Plains (SGP) atmospheric observatory. Our study also benefits from state-of-the-art laboratory facilities that include three-dimensional molecular imaging techniques enabled by secondary ion mass spectrometry and nanogram-level chemical composition analysis via micronebulization aerosol mass spectrometry. Through our study, we have developed a framework for observation–modeling integration, enabling an examination of how various assumptions about the organic–inorganic components mixing state, inferred from chemical analysis, affect clouds and radiation in observation-constrained model simulations. By integrating observational constraints (derived from offline chemical analysis of the aerosol surface using collected samples) with in situ UAS observations, we have identified a prominent role of organic-enriched nanometer layers located at the surface of aerosol particles in determining profiles of aerosol optical and hygroscopic properties over the SGP observatory. Furthermore, we have improved the agreement between predicted clouds and ground-based cloud lidar measurements. This UAS–model–laboratory integration exemplifies how these new advanced capabilities can significantly enhance our understanding of aerosol–radiation–cloud interactions.

Characteristics of the Discoloration Switching Phenomenon of 4H-SiC Single Crystals Grown by PVT Method Using ToF-SIMS and Micro-Raman Analysis.

The discoloration switching appearing in the initial and final growth stages of 4H-silicon carbide (4H-SiC) single crystals grown using the physical vapor transport (PVT) technique was investigated. This phenomenon was studied, investigating the correlation with linear-type micro-pipe defects on the surface of 4H-SiC single crystals. Based on the experimental results obtained using time-of-flight secondary ion mass spectrometry (ToF-SIMS) and micro-Raman analysis, it was deduced that the orientation of the 4H-SiC c-axis causes an axial change that correlates with low levels of carbon. In addition, it was confirmed that the incorporation of additional elements and the concentrations of these doped impurity elements were the main causes of discoloration and changes in growth orientation. Overall, this work provides guidelines for evaluating the discoloration switching in 4H-SiC single crystals and contributes to a greater understanding of this phenomenon.

Spatially Resolved Molecular Analysis of Host Response to Medical Device Implantation Using the 3D OrbiSIMS Highlights a Critical Role for Lipids.

A key goal for implanted medical devices is that they do not elicit a detrimental immune response. Macrophages play critical roles in the modulation of the host immune response and are the cells responsible for persistent inflammatory reactions to implanted biomaterials. Two novel immune-instructive polymers that stimulate pro- or anti-inflammatory responses from macrophages in vitro are investigated. These also modulate in vivo foreign body responses (FBR) when implanted subcutaneously in mice. Immunofluorescent staining of tissue abutting the polymer reveals responses consistent with pro- or anti-inflammatory responses previously described for these polymers. Three Dimensional OrbiTrap Secondary Ion Mass Spectrometry (3D OrbiSIMS) analysis to spatially characterize the metabolites in the tissue surrounding the implant, providing molecular histology insight into the metabolite response in the host is applied. For the pro-inflammatory polymer, monoacylglycerols (MG) and diacylglycerols (DG) are observed at increased intensity, while for the anti-inflammatory coating, the number of phospholipid species detected decreased, and pyridine and pyrimidine levels are elevated. Small molecule signatures from single-cell studies of M2 macrophages in vitro correlate with the in vivo observations, suggesting potential for prediction. Metabolite characterization by the 3D OrbiSIMS is shown to provide insight into the mechanism of bio-instructive materials as medical devices and to inform on the FBR to biomaterials.

Alkali-metal-based molecular-ion secondary ion mass spectrometry for precise quantitative analysis of low-dimensional materials without standards

Advancement in the understanding of fundamental aspects of Secondary Ion Mass Spectrometry (SIMS) has made this technique to be extremely powerful for quantitative materials analysis. The secondary ion emission process is a complex phenomenon involving various mechanisms to understand the mechanism. Among the existing mechanisms, the “electron-tunneling model” is the most accepted concept in the understanding of ionization probability for positive and negative ions. This model essentially concerns the survival probability of an ion emitted from the surface. As the intensity of secondary ions of a certain element depends strongly on the efficiency of ionization of a sputtered atom or molecule, the “local surface chemistry” plays a significant role in the secondary ion emission. This is purported as the “Matrix Effect” in SIMS, making the technique extremely challenging for quantification of materials in spite of the fact that it has the highest detection sensitivity (<ppb) and exceptional depth-resolution (<1[Formula: see text]nm). Therefore, it is required to correct the “matrix effect” for quantitative analysis. If the probing element (M) in its close proximity sees an alkali element (such as Li, Rb, K, Na and Cs, referred to as “A”) on the sample surface, the sputtered neutral atom (M0) of the probing element can attach an alkali-ion forming a quasi-molecular (MA)[Formula: see text] ion. Such a phenomenon can also occur if an alkali ion beam is chosen as the primary beam for sputtering. The MA[Formula: see text] molecular ion formation is directly related to the atomic polarizability of the element M. Since the sputtering of neutral atom (M0) is unconnected with the formation of MA[Formula: see text] ion, the “matrix effect” decreases dramatically in the analysis using MA[Formula: see text] ions. The phenomenon is very similar to the mechanism of “secondary neutral mass spectrometry” (SNMS). Although these (MA)[Formula: see text] molecular ions are potentially applicable in the direct quantification of materials without the need for “calibration standards”, it generally has a weak intensity. In such a case, the (MA)[Formula: see text] molecular ions are preferred in the analysis because of their higher detection sensitivity (by a few orders of magnitude in some cases), compared to that of (MA)[Formula: see text] molecular ions. Monitoring of the molecular ions is routinely preferred in conventional SIMS experiments to discriminate the sputtered ion species which are affected by mass interference or have poor dynamic ranges. For example, while making the SIMS analysis of GaAs, carbon as an impurity element is detected by monitoring (AsC)[Formula: see text] molecular ions instead of C− ions, because the C− ions have high background arising from the carbon-containing residual-gas species in the analysis chamber. Caesium is decidedly chosen for MCs[Formula: see text] or MCs[Formula: see text] molecular ions in SIMS because of the strongest reactivity and electropositive nature of caesium. This paper deals with a comprehensive discussion on the ion-emission phenomena in sputtering, the “matrix effect” and its compensation, and the potential application of the “MCs[Formula: see text]-SIMS” ([Formula: see text]) in the effective quantitative chemical analysis of materials. A special prominence has been given to the quantification of low-dimensional materials, superlattices and quantum-confined structures using this state-of-the-art “MCs[Formula: see text]-SIMS” approach in all complexities.