Time-of-flight Secondary Ion Mass Spectrometry Research Articles

The Application of a Random Forest Classifier to ToF-SIMS Imaging Data.

Time-of-flight secondary ion mass spectrometry (ToF-SIMS) imaging is a potent analytical tool that provides spatially resolved chemical information on surfaces at the microscale. However, the hyperspectral nature of ToF-SIMS datasets can be challenging to analyze and interpret. Both supervised and unsupervised machine learning (ML) approaches are increasingly useful to help analyze ToF-SIMS data. Random Forest (RF) has emerged as a robust and powerful algorithm for processing mass spectrometry data. This machine learning approach offers several advantages, including accommodating nonlinear relationships, robustness to outliers in the data, managing the high-dimensional feature space, and mitigating the risk of overfitting. The application of RF to ToF-SIMS imaging facilitates the classification of complex chemical compositions and the identification of features contributing to these classifications. This tutorial aims to assist nonexperts in either machine learning or ToF-SIMS to apply Random Forest to complex ToF-SIMS datasets.

Effects of Pt doping on surface properties and quenching of band edge emission in ZnO

Pt doped ZnO thin films were synthesized on soda-lime glass substrates using a cost-effective sol-gel method, followed by spin coating and thermal annealing at various temperatures. Several characterization techniques such as UV–Vis absorption spectroscopy, photoluminescence (PL), field emission scanning electron microscopy (FESEM), time-of-flight secondary ion mass spectroscopy (ToF-SIMS), Raman spectroscopy, and X-ray photoelectron spectroscopy (XPS) are exploited to investigate the Pt doping effects on surface and optical properties of ZnO thin films. UV–Vis analysis demonstrated a slight decrease in the optical band gap from 3.3 eV to 3.2 eV with increased annealing, indicating enhanced suitability for optoelectronic applications. FESEM imaging revealed distinct worm-like structures and small Pt metal nanoparticles in unannealed samples, while thermal treatment supported the formation of spherical Pt nanoparticles and improved conductive pathways in the films. The Wagner diagram, coupled with Auger line transitions from XPS, quantified the oxidation states and chemical environments of Zn and Pt, respectively. Notably, the observed changes in the binding energy of the Zn-2p junction and the kinetic energy of the Zn-LMM Auger junction were significantly influenced by the Pt doping and the electronic properties of the substrate. The Wagner diagram provided a comprehensive visual representation of the parameters, facilitating a deeper understanding of electronic interactions and structural dynamics at the atomic level. XPS results confirmed the presence of ZnO, Zn(OH)2, Pt0 and PtO2 phases, indicating stability and constutient's interactions. ToF-SIMS also validated the uniform distribution of Pt nanoparticles within the ZnO thin film, confirming the effectiveness of the sol-gel method. As a result of Pt doping, PL studies revealed a large quenching effect on band edge emission in the UV and visible emission region of ZnO thin film, which is due to Pt acting as a recombination center for photogenerated carriers. Overall, our results highlight the influence of annealing and Pt incorporation on the optical and structural properties of ZnO thin films and highlight their potential applications for photonics and catalysis.

Ultra-High Adsorption Capacity of Calcium-Iron Layered Double Hydroxides for HEDP Removal through Phase Transition Processes.

Antiscalant disposal in reverse osmosis concentrate (ROC) treatment is a significant obstacle in desalination. This study investigated the adsorption performance of LDHs for removing 1-hydroxyethylidene-1,1-diphosphonic acid (HEDP). CaFe-LDH presented a specific adsorption behavior and ultrahigh adsorption capacity for HEDP, with a maximum adsorption capacity of 335.7 mg P/g (1116.5 mg HEDP/g) at pH 7.0. X-ray diffraction (XRD) demonstrated that HEDP adsorption induced a structural transformation of CaFe-LDH from a layered configuration to a highly ordered structure, leading to a noticeable phase transition. Time-of-flight secondary ion mass spectrometry (ToF-SIMS) and Raman spectroscopy further confirmed that two distinct binding modes of HEDP, relating to chelation with Ca2+ and adsorption on Fe3+ simultaneously, are connected by phosphonic acid groups (-C-PO(OH)2), forming the CaFe-HEDP complex. X-ray fluorescence (XRF) and X-ray photoelectron spectroscopy (XPS) analyses revealed that the CaFe-HEDP ternary complex exhibits a highly ordered arrangement in an oxygen-bridged framework. The construction of an oxygen-coordinated framework contributes to the incorporation of more HEDP into CaFe-LDH, leading to a well-aligned lattice in the new phase. These findings provide valuable insights into developing novel LDH-based adsorbents for removing phosphorus-containing antiscalants, establishing a sustainable approach to ROC management, and potential environmental risk reduction.

Development of Peptide Identification System for ToF-SIMS Spectra Using Supervised Machine Learning.

Time-of-flight secondary ion mass spectrometry (ToF-SIMS) data interpretation for organic materials is complicated because of various fragment ions produced from each molecule and the overlapping of certain mass peaks from different molecules. Fragmentation mechanisms in SIMS are complex because different sputtering and ionization processes can simultaneously occur. Therefore, a prediction system that can identify materials in a sample is required. A novel prediction system for peptides based on ToF-SIMS and amino-acid-based teaching information (labels) for supervised machine learning was developed. To develop the prediction system for general organic materials, the annotation of materials is crucial to creating effective labels for supervised learning. Peptides are composed of 20 amino acid residues, which can be used as labels. We previously developed a peptide prediction system using Random Forest, a supervised machine-learning method. However, only the amino acids contained in the target peptide were predicted, and the amino acid sequence was unable to be assumed. In this study, the amino acid sequence of the test peptide was determined by adding the information on two adjacent amino acids to the labels. Once the prediction system learned the target peptide spectra, the peptides in the newly obtained ToF-SIMS spectra could be identified. The new prediction system also provides useful information for the identification of unknown peptides. The prediction results indicate that two adjacent permutations of amino acids are effective pieces of teaching information for expressing the amino acid sequence of a peptide.

Identifying Process Differences with ToF-SIMS: An MVA Decomposition Strategy.

In time-of-flight secondary ion mass spectrometry (ToF-SIMS), multivariate analysis (MVA) methods such as principal component analysis (PCA) are routinely employed to differentiate spectra. However, additional insights can often be gained by comparing processes, where each process is characterized by its own start and end spectra, such as when identical samples undergo slightly different treatments or when slightly different samples receive the same treatment. This study proposes a strategy to compare such processes by decomposing the loading vectors associated with them, which highlights differences in the relative behavior of the peaks. This strategy identifies key information beyond what is captured by the loading vectors or the end spectra alone. While PCA is widely used, partial least-squares discriminant analysis (PLS-DA) serves as a supervised alternative and is the preferred method for deriving process-related loading vectors when classes are narrowly separated. The effectiveness of the decomposition strategy is demonstrated using artificial spectra and applied to a ToF-SIMS materials science case study on the photodegradation of N719 dye, a common dye in photovoltaics, on a mesoporous TiO2 anode. The study revealed that the photodegradation process varies over time, and the resulting fragments have been identified accordingly. The proposed methodology, applicable to both labeled (supervised) and unlabeled (unsupervised) spectral data, can be seamlessly integrated into most modern mass spectrometry data analysis workflows to automatically generate a list of peaks whose relative behavior varies between two processes, and is particularly effective in identifying subtle differences between highly similar physicochemical processes.

Revealing the Role of Ruthenium on the Performance of P2-Type Na0.67Mn1-xRuxO2 Cathodes for Na-Ion Full-Cells.

Herein, P2-type layered manganese and ruthenium oxide is synthesized as an outstanding intercalation cathode material for high-energy density Na-ion batteries (NIBs). P2-type sodium deficient transition metal oxide structure, Na0.67Mn1-xRuxO2 cathodes where x varied between 0.05 and 0.5 are fabricated. The partially substituted main phase where x = 0.4 exhibits the best electrochemical performance with a discharge capacity of ≈170mAhg-1. The in situ X-ray Absorption Spectroscopy (XAS) and time-resolved X-ray Diffraction (TR-XRD) measurements are performed to elucidate the neighborhood of the local structure and lattice parameters during cycling. X-ray photoelectron spectroscopy (XPS) revealed the oxygen-rich structure when Ru is introduced. Density of States (DOS) calculations revealed the Fermi-Level bandgap increases when Ru is doped, which enhances the electronic conductivity of the cathode. Furthermore, magnetization calculations revealed the presence of stronger Ru─O bonds and the stabilizing effect of Ru-doping on MnO6 octahedra. The results of Time-of-flight secondary-ion mass spectroscopy (TOF-SIMS) revealed that the Ru-doped sample has more sodium and oxygenated-based species on the surface, while the inner layers mainly contain Ru-O and Mn-O species. The full cell study demonstrated the outstanding capacity retention where the cell maintained 70% of its initial capacity at 1C-rate after 500 cycles.

Enhanced imaging of developed fingerprints and its contaminated substance using ToF-SIMS

Fingerprint is a common form of evidence utilized in crime cases, providing crucial information for suspect identification and the proof of key facts. However, traditional development methods are often ineffective for challenging fingerprints due to variations in information and surface characteristics, potentially causing damage to the fingerprint substance. Time-of-flight secondary ion mass spectrometry (ToF-SIMS) offers a non-destructive approach that combines spatial imaging with mass spectrometry capabilities. This study employed ToF-SIMS to enhance natural fingerprints that showed poor visualization when treated with 1,2-indandione and ninhydrin on porous surfaces such as printing paper, kraft paper, newspaper, and thermal paper, especially on challenging textiles. We also imaged fingerprints on nonporous surfaces that were deposited over 30 days ago using ToF-SIMS, like aluminum foil, express packaging bags, and slides. We then extended the age of fingerprint detection to 3 months to explore the relationship between the aging of fingerprints and the morphological characteristics of sweat pores. Furthermore, the study examined the detection capabilities of ToF-SIMS on fingerprints contaminated with compound econazole nitrate cream after being interfered with by development agents, illustrating its effectiveness in extracting comprehensive fingerprint information.

Lanthanum doped hafnium oxide thin films deposited on a lateral high aspect ratio structure using atomic layer deposition: A comparative study of surface composition and uniformity using x-ray photoelectron spectroscopy and time-of-flight secondary ion mass spectrometry

Hafnium oxide (HfO2) thin films doped with lanthanum (La) can achieve ferroelectricity, making the material applicable in transistor and memory technologies. To downscale future devices in the semiconductor industry, the application of the doped HfO2 material requires deposition on complex microscopic three-dimensional (3D) structures. A widely used process for the preparation of doped HfO2 thin films is atomic layer deposition (ALD). With 3D geometries, it is challenging to deposit materials homogeneously and to effectively characterize them. To forego the difficulties in film characterization, two-dimensional (2D) PillarHall lateral high aspect ratio (LHAR) test structures are used. These structures expose a lateral surface to facilitate the conformality analysis of thin films deposited using two different ALD processes. In this work, we aim to further advance the arsenal of analysis techniques used to characterize La doped HfO2 thin films by using x-ray photoelectron spectroscopy (XPS) and time-of-flight secondary ion mass spectrometry (ToF-SIMS) to analyze uniformity and composition. The XPS technique can be applied and established as a method for the optimal analysis of thin films deposited on LHAR structures. Both techniques provide a complementary analysis of material formation, elemental distribution, measurement along the LHAR depth range, and can probe differences between deposition processes.

Engineering a superamphiphilic surface for enhanced interfacial bonding in metal-polymer hybrid structure

Insufficient wetting of polymer due to its poor compatibility with metals leads to non-intimate interfacial mutual contact during the thermal-direct bonding process, thus hindering the establishment of effective mechanical interlocking and substantial chemical bonding at the interface, resulting in deficient performance of metal-polymer hybrid structures. To achieve high-quality bonding between non-polar ultra-high molecular weight polyethylene (UHMWPE) and Ti6Al4V titanium alloy (TC4) for the application of artificial joint prostheses, this study innovatively engineered a superamphiphilic (simultaneously superhydrophilic and superlipophilic) TC4 surface, which was achieved through a morphology-chemistry dual regulation strategy. This pretreatment strategy aimed at improving the interfacial compatibility between in-situ oxidized UHMWPE and TC4 and ensuring intimate contact between these two materials during thermal-direct bonding, thus facilitating chemical reactions and mechanical interlocking at the interface. Defect-free and ultra-high-performance TC4-UHMWPE hybrid joints were successfully obtained via friction spot joining (FSpJ) with the lap shear strength reaching 18.05 MPa (higher than all those similar hybrid joints reported in existing literature) and the fracture was confined to the UHMWPE matrix, effectively avoiding interfacial failure. The formation of chemical bonds in the form of COTi at TC4/UHMWPE interface was solidly confirmed based on X-ray photoelectron spectroscopy (XPS) and time-of-flight secondary ion mass spectrometry (ToF-SIMS) analyses. This research presents a compelling strategy for improving interfacial compatibility between polymer and metal for thermal-direct bonding, to overcome the general difficulties in achieving effective interfacial bonding between these two categories of materials with significantly different physiochemical properties.

Selective control of surface characteristics of magnesite and quartz by a novel silicophilic collector stearylamine acetate

Reverse flotation desiliconization from magnesite is significant for the exploitation of complex and barren magnesite resources. In this process, a critical issue is to find efficient and selective chemicals as flotation collectors. Herein, a cationic surfactant stearylamine acetate (SAA) was first used as a collector for the separation of magnesite and quartz. Micro-flotation experiments demonstrate that quartz can be separated from magnesite with a high Gaudin’s selectivity index of 6.51 at slurry pH 5.0 and 70 mg/L SAA. Measurements of zeta potential and contact angle show that SAA selectively increased the surface charge and hydrophobicity of quartz. Field emission scanning electron microscopy (FESEM/EDS) and atomic force microscope (AFM) imaging indicate greater adsorption density of SAA on quartz than magnesite, with significantly higher nitrogen element content and RMS surface roughness of quartz. We also used surface-sensitive time of flight secondary ion mass spectrometry (TOF-SIMS) and FTIR spectroscopy to characterize the selective adsorption of SAA on quartz from quartz-magnesite mixtures. Apart from electrostatic attraction, it is found that the selective adsorption was attributed to hydrogen bonding formed between the −N–H group of SAA and the oxygen atom of the O-Si-O group on quartz surface.

Efficient Flotation Separation of Ilmenite and Olivine in a Weak Alkaline Pulp Using a Ternary Combination Collector Centered around Al3.

Due to the similar physical and chemical properties of ilmenite and olivine, separating them is challenging. The flotation process, with the use of collectors, is an effective method. In this study, a ternary collector consisting of aluminum ion (III), benzohydroxamic acid (BHA), and sodium oleate (NaOL) was prepared for the flotation separation of ilmenite and olivine. Through micro-flotation experiments, molecular dynamics simulation (MD), density functional theory (DFT), scanning electron microscopy (SEM), X-ray photoelectron spectroscopy (XPS), and time-of-flight secondary ion mass spectrometry (TOF-SIMS) analysis, the synergistic effect between the components of the ternary collector and the adsorption configuration on the surface of ilmenite was investigated. The results revealed that at pH = 8, Al (III), BHA, and NaOL could coordinate and adsorb effectively on the surface of ilmenite, enhancing its floatability for separation from olivine. The adsorption configuration differed from previous reports, showing a co-adsorption of multiple forms on the surface of ilmenite.

Reactive Gas Cluster Ion Beams for Enhanced Drug Analysis by Secondary Ion Mass Spectrometry.

In this study, we investigate the formation and composition of Gas Cluster Ion Beams (GCIBs) and their application in Time-of-Flight Secondary Ion Mass Spectrometry (ToF-SIMS) analysis. We focus on altering the carrier gas composition, leading to the formation of (Ar/CO2)n or (H2O)n GCIBs. Our results demonstrate that the addition of a reactive species (CO2) to water GCIBs significantly enhances the secondary ion yield of small pharmaceutical compounds in the positive ion mode. In negative ion mode, the addition of CO2 resulted in either a positive enhancement or no effect, depending on the sample. However, an excess of CO2 in the carrier gas leads to the formation of carbon dioxide clusters, resulting in reduced yields compared to that of water cluster beams. Cluster size also plays a crucial role in overall yields. In a simple two-drug system, CO2-doped water clusters prove effective in mitigating matrix effects in positive ion mode compared to pure water cluster, while in negative ion mode, this effect is limited. These clusters are also applied to the analysis of drugs in a biological matrix, leading to more quantitative measurements as shown by a better fitting calibration curve. Overall, the doping of water clusters with small amounts of a reactive gas demonstrates promising benefits for higher sensitivity, higher resolution molecular analysis, and imaging using ToF-SIMS. The effectiveness of these reactive cluster beams varies depending on the experimental parameters and sample type.

Enhanced marmatite activation by copper with ammonium sulfate: An experimental and DFT investigation

The presence of iron atoms on the marmatite surface hinders effective interaction between the activator and the mineral, leading to unsatisfactory flotation performance through direct copper (Cu) activation. Hence, this study introduced ammonium sulfate to enhance the marmatite-activation capability by Cu ions. Additionally, the reinforcement mechanism was investigated through microflotation tests, atomic force microscopy (AFM), scanning electron microscopy-energy-dispersive X-ray spectroscopy (SEM-EDS), X-ray photoelectron spectroscopy (XPS), time-of-flight secondary ion mass spectrometry (ToF-SIMS), and density-functional theory (DFT) calculations. Microflotation results demonstrated that the addition of ammonium sulfate as a complexing reagent increased the flotation recovery of marmatite by 17.36%. AFM analysis revealed that marmatite subjected to enhanced activation (i.e., in the presence of ammonium sulfate) exhibited a considerably higher surface roughness than that subjected to direct Cu activation. Moreover, the average height of hill-shaped materials on the marmatite surface notably increased to 9.6 nm after enhanced Cu activation. SEM-EDS analysis revealed that the concentration of Cu atoms (2.2%) on the marmatite surface after enhanced Cu activation was nearly three times that (0.8%) after direct Cu activation. Additionally, XPS results indicated a considerably higher presence of the Cu–S component on the marmatite surface after enhanced Cu activation than after direct Cu activation. ToF-SIMS analysis indicated an increase in the fragment peaks of Cu+, CuOCS2+, OCS2−, and OC2H2S2− on the surface of enhanced-activated marmatite. Additionally, DFT calculations indicated that the presence of NH3 molecules enhanced electron transfer between Cu and S on the hydrated marmatite surface. The marmatite (1 1 0) surface exhibited more negative adsorption energy of Cu ions after the action of NH3 molecules, and NH3–Cu showed a more stable adsorption configuration than Cu. Therefore, the addition of ammonium sulfate enhanced the Cu activation for marmatite, thereby improving flotation performance.

Regulation of Ir Dopant in Mo Oxides by Flame Spray Pyrolysis for Efficient CO2 Hydrogenation.

Mo carbide is recognized as one of the most promising catalyst for CO2 utilization via reverse water-gas shift (RWGS). However, it always suffered from low processing capacity, undesired products and deactivation. Herein, an Ir modified MoO3 synthesized by the flame spray pyrolysis (FSP) method exhibits higher reaction rate (63.0 gCO2·gcat-1·h-1) compared to the one made by traditional impregnation method (45.8 gCO2·gcat-1·h-1) over the RWGS reaction at 600°C. The distinguishing feature between the two catalysts lies in the chemical state and space distribution of Ir species. Ir species predominated in the bulk phase of MoO3 during the quenching process of the FSP method and were mainly in the metallic states, which revealed by X-ray absorption spectroscopy (XAS), X-ray photoelectron spectroscopy (XPS), and time-of-flight secondary ion mass spectroscopy (ToF-SIMS) characterizations. In contrast, the Ir introduced via impregnation method were mainly on the surface of MoO3 and in oxidized state. The regulation of Ir dopant in MoO3 catalyst by different methods determines the carbonization process to Mo carbides, and thus affects the catalytic performance. This work sheds light on the superiority of the FSP method in synthesizing Mo oxides with heteroatoms and further creating an efficient Mo-based catalyst for CO2 conversion.

Study on the interstitial oxygen diffusion to understand the reduction of cryogenic RF loss for the superconducting radio-frequency niobium cavities

Abstract Medium-temperature baking (Mid-T baking) is an innovative method employed to enhance the unloaded quality factor Q0 of superconducting radio-frequency (SRF) niobium (Nb) cavities at cryogenic temperatures. This study presents an interstitial oxygen diffusion model based on the decomposition of the natural oxide to clarify the improved performance of the Nb cavities after undergoing Mid-T baking. Additionally, the correlation between the interstitial oxygen within the RF penetration depth and the surface resistance of the Nb cavities has been explored. The parameter for the oxide decomposition was determined using in-situ X-ray photoelectron spectroscopy (XPS), where the thickness of the oxide/carbide layer was calculated from the peak fitting of Nb 3d spectra and the attenuation law of the photoelectron beam. The interstitial oxygen diffusion model, validated by the semi-quantitative distribution along the depth determined by Time of Flight Secondary Ion Mass Spectrometry (ToF-SIMS), quantifies the oxygen atomic concentration within the RF penetration depth in Mid-T baked Nb material. In the baking temperature range of 300~400 ℃, the calculated oxygen concentration from the interstitial oxygen diffusion model demonstrates a more pronounced dependence on the baking temperature than the baking time. This suggests that more precise control of the interstitial oxygen concentration can be achieved by adjusting the baking temperature. Furthermore, it has been observed that maintaining a uniform and moderate oxygen concentration throughout the depth is essential for optimal BCS resistance. This study paves the way for more efficient processing optimization and enhancing understanding of the mechanism behind RF loss in Nb cavities.

Studying microbially induced corrosion on glass using ToF-SIMS.

Microbially induced corrosion (MIC) is an emerging topic that has huge environmental impacts, such as long-term evaluation of microbial interactions with radioactive waste glass, environmental cleanup and disposal of radioactive material, and weathering effects of microbes. Time-of-flight secondary ion mass spectrometry (ToF-SIMS), a powerful mass spectral imaging technique with high surface sensitivity, mass resolution, and mass accuracy, can be used to study biofilm effects on different substrates. Understanding how to prepare biofilms on MIC susceptible substrates is critical for proper analysis via ToF-SIMS. We present here a step-by-step protocol for preparing bacterial biofilms for ToF-SIMS analysis, comparing three biofilm preparation techniques: no desalination, centrifugal spinning (CS), and water submersion (WS). Comparisons of two desalinating methods, CS and WS, show a decrease in the media peaks up to 99% using CS and 55% using WS, respectively. Proper desalination methods also can increase biological signals by over four times for fatty acids using WS, for example. ToF-SIMS spectral results show chemical compositional changes of the glass exposed in a Paenibacillus polymyxa SCE2 biofilm, indicating its capability to probe microbiologically induced corrosion of solid surfaces. This represents the proper desalination technique to use without significantly altering biofilm structure and substrate for ToF-SIMS analysis. ToF-SIMS spectral results showed chemical compositional changes of the glass exposed by a Paenibacillus bacterial biofilm over 3-month inoculation. Possible MIC products include various phosphate phase molecules not observed in any control samples with the highest percent increases when experimental samples were compared with biofilm control samples.

NST3 induces ectopic transdifferentiation, forming secondary walls with diverse patterns and composition in Arabidopsis thaliana.

The master transcription factor NAC SECONDARY WALL THICKENING PROMOTING FACTOR3 (NST3), also known as SND1, plays a pivotal role in regulating secondary cell wall (SCW) development in interfascicular and xylary fibers in Arabidopsis thaliana. Despite progress in understanding SCW assembly in xylem vessel-like cells, the mechanisms behind its assembly across different cell types remain unclear. Overexpressing NST3 or its homolog NST1 leads to reduced fertility, posing challenges for studying their impact on secondary wall formation. This study aimed at developing a tightly regulated dexamethasone (DEX)-inducible expression system for NST3 and NST1 to elucidate the structure and assembly of diverse SCWs. Using the DEX-inducible system, we characterized ectopically formed SCWs for their diverse patterns, mesoscale organization, cellulose microfibril orientation, and molecular composition using spinning disk confocal microscopy, field emission scanning electron microscopy (FESEM), vibrational sum-frequency generation (SFG) spectroscopy and, histochemical staining and time-of-flight secondary ion mass spectrometry (ToF-SIMS), respectively. Upon DEX treatment, NST3 and NST1 transgenic hypocotyls underwent time-dependent transdifferentiation, progressing from protoxylem-like to metaxylem-like cells. NST3-induced plants exhibited normal growth but had rough secondary wall surfaces with delaminating S2 and S3 layers. Mesoscale examination of induced SCWs in epidermal cells revealed that macrofibril thickness and orientation were comparable to xylem vessels, while wall thickness resembled that of interfascicular fibers. Additionally, induced epidermal cells formed SCWs with altered cellulose and lignin contents. These findings suggest NST3 and/or NST1 induce SCWs with shared characteristics of both xylem and fiber-like cells forming loosely arranged cell wall layers and cellulose organized at multiple angles relative to the cell growth axis and with varied cellulose and lignin abundance. This inducible system opens avenues to explore ectopic SCWs for bioenergy and bioproducts, offering valuable insights into SCW patterning across diverse cell types and developmental stages.

Nanoparticle Diffusion in Crowded Polymer Nanocomposite Melts.

This study examines nanoparticle diffusion in crowded polymer nanocomposites by diffusing small Al2O3 nanoparticles (NPs) in SiO2-loaded P2VP matrices. Time-of-flight secondary ion mass spectroscopy (ToF-SIMS) measures Al2O3 NP diffusion coefficients within a homogeneous PNC background of larger, immobile SiO2 NPs. By developing a geometric model for the average interparticle distance in a system with two NP sizes, we quantify nanocomposite confinement relative to the Al2O3 NP size with a bound layer. At low SiO2 concentrations, Al2O3 NP diffusion aligns with the neat polymer results. In more crowded nanocomposites with higher SiO2 concentrations where the interparticle distance approaches the size of the mobile Al2O3 NP, the 6.5 nm Al2O3 NPs diffuse faster than predicted by both core-shell and vehicular diffusion models. Relative to our previous studies of NPs diffusing into polymers, these findings demonstrate that the local environment in crowded systems significantly complicates NP diffusion behavior and the bound layer lifetimes.

Gradient conducting polymer surfaces with netrin-1-conjugation promote axon guidance and neuron transmission of human iPSC-derived retinal ganglion cells

Major advances have been made in utilizing human-induced pluripotent stem cells (hiPSCs) for regenerative medicine. Nevertheless, the delivery and integration of hiPSCs into target tissues remain significant challenges, particularly in the context of retinal ganglion cell (RGC) restoration. In this study, we introduce a promising avenue for providing directional guidance to regenerated cells in the retina. First, we developed a technique for construction of gradient interfaces based on functionalized conductive polymers, which could be applied with various functionalized ehthylenedioxythiophene (EDOT) monomers. Using a tree-shaped channel encapsulated with a thin PDMS and a specially designed electrochemical chamber, gradient flow generation could be converted into a functionalized-PEDOT gradient film by cyclic voltammetry. The characteristics of the successfully fabricated gradient flow and surface were analyzed using fluorescent labels, time of flight secondary ion mass spectrometry (TOF-SIMS), and X-ray photoelectron spectroscopy (XPS). Remarkably, hiPSC-RGCs seeded on PEDOT exhibited improvements in neurite outgrowth, axon guidance and neuronal electrophysiology measurements. These results suggest that our novel gradient PEDOT may be used with hiPSC-based technologies as a potential biomedical engineering scaffold for functional restoration of RGCs in retinal degenerative diseases and optic neuropathies.

Efficient flotation separation of chalcopyrite from molybdenite and adsorption mechanism by green depressant pyrogallic acid

Chalcopyrite and molybdenite are the primary minerals from which copper and molybdenum are extracted. However, the separation of chalcopyrite and molybdenite is restricted because of their inherent floatability. This study explores the separation effects of the addition of a green depressant, pyrogallic acid (PA), on chalcopyrite and molybdenite. The feasibility of flotation separation was verified by flotations tests with chalcopyrite and molybdenite under weak acid conditions at pH 6. The zeta potential and total organic carbon (TOC) illustrated that PA could have strong chemical adsorption on the surface of chalcopyrite and weak adsorption on the surface of molybdenite. Fourier-transform infrared (FTIR) spectroscopy illustrated that PA had a strong redox reaction at the surface of chalcopyrite. X-ray photoelectron spectroscopy (XPS) results illustrated that the reaction occurred through the generation of Cu/Fe-OH complexes covered on the chalcopyrite surface to reduce the active adsorption sites, which led to a decrease in the collection capacity for chalcopyrite. Moreover, time-of-flight secondary ion mass spectrometry (ToF-SIMS) results showed that the Cu and Fe sites on the surface of chalcopyrite were oxidized by PA. The intensities of FeOH− and CuOH− were found to be enhanced in the fragmentation peaks. Accordingly, a new selective adsorption model of PA on chalcopyrite and molybdenite was proposed.