We developed a Monte Carlo simulation workflow to investigate the effects of sample thickness, membrane thickness, sample composition, and incident electron energy on the visibility of samples in liquid-phase scanning electron microscopy based on electron-transparent Si3N4 membranes. By using a thin wedge as the sample geometry and non-uniform spacing of the scan points, we avoided the need to generate numerous geometries for each configuration and reduced the computation time by up to 2 orders of magnitude. Quantitative analyses of the threshold current for visible contrast and the spatial resolution revealed that secondary electrons may visualize thin samples more effectively than BSEs at incident electron energies down to 3 keV when aided by efficient in-lens detectors and Si3N4 membranes with a thickness of 20 nm or lower. The simulations also supported the trends of decreasing spatial resolution with the thickness of both the membrane and the sample material.

Electrically non-conducting wood-based and -derived materials often suffer from charging artifacts in scanning electron microscopy (SEM). Ionic liquids (ILs) can dissipate the excess charges but have not replaced conventional coatings. In this study, we addressed the lack of low-cost options and attention to true nanoscale features by applying 1-ethyl-3-methylimidazolium methane sulfonate ([EMI][MeSO3]) to different wood-based and -derived materials. Aqueous IL treatment of microcrystalline cellulose (MCC) improved the visibility of the particles and surface microfibrils and simplified sample preparation compared to gold and carbon coatings. Tailored IL solutions restored topographic contrast without significantly altering the surface morphology of sugar maple sawdust and pinecone scales. Imaging at 1 kV on treated samples revealed more nanoscale features than at the standard 5 kV, enabled by the thin surface layer of IL. The IL treatment outperformed variable-pressure SEM in spatial resolution and signal-to-noise ratio. This convenient and affordable method can benefit rapid, high-resolution, and high-fidelity SEM imaging of non-conducting materials.

Crystalline two-dimensional (2D) semiconductors often combine high elasticity and in-plane strength, making them ideal for strain-induced tuning of electronic characteristics, akin to strategies used in silicon electronics. However, existing techniques have not achieved strain in 2D materials that is simultaneously high in magnitude (>1

Beam current measurement is a crucial step in estimating the electron dose when studying beam-sensitive samples in electron microscopy. A Faraday cup is a standard tool for measuring beam current; however, commercially available Faraday cups for transmission electron microscopes (TEM) are limited, expensive, and often difficult to use as the cup itself is invisible in the TEM. We herein present a new Faraday cup design that fits into an insulated TEM holder of Hitachi HT7700 and HT7800 series and can be easily located using four symmetrical through holes around the cup. This design also accommodates the 3 mm TEM mesh grid in the holder and allows both sample imaging and access to the Faraday cup within the TEM stage movement range. We evaluated the effectiveness of our Faraday cup in capturing the electron beam by varying the diameter to depth ratio and material of the Faraday cup through experimental measurements and Monte Carlo simulations, demonstrating an accuracy better than 1-2 %. The preferred configuration is an aluminum cup with a diameter of 0.2 mm and a depth of 0.8 mm. Monte Carlo simulations also suggest that this Faraday cup provides accurate beam current measurement at different electron energies. Our novel Faraday cup design provides a practical, simple, and cost-effective solution for beam current measurement in a TEM.

Bronze disease is a severe type of degradation in ancient copper-based artifacts and poses challenges to their preservation. This "disease" is an active cyclic corrosion process primarily caused by chlorine, oxygen and moisture. Products formed during this process, such as cuprous chloride (CuCl), continue to spread across the artifact's surface until all available oxygen is consumed, resulting in irreversible destruction. Bronze disease is difficult to distinguish from other corrosion processes, leading to inaccurate assessments of the degradation mechanisms affecting the artifact. Combined scanning electron microscopy (SEM) and energy-dispersive x-ray spectroscopy (EDS) is a viable method for analyzing bronze disease in ancient artifacts and for differentiating it from other forms of degradation. This study investigated suspected bronze disease on a Chinese cast bronze vessel dating from the 11th - 10th century BCE, part of the collection at the Royal Ontario Museum in Toronto, Canada. Corrosion product sampled from the vessel using two different methods, was chemically and topographically analyzed using SEM-EDS. The first method involved the removal of corrosion product using a scalpel, resulting in the collection of mixed particles. The second method, involving the creation of replicas, utilized an adhesive to directly remove the corrosion product, capturing the particles in their original locations. The sampled material contained copper and chlorine, consistent with the presence of bronze disease, though further work is required for confirmation. Although both techniques can investigate bronze disease, the replica technique offers a more promising approach, as it enables more precise, site-specific analysis of the corrosion product.

Scanning electron microscopy (SEM) is the premier method for characterizing the nanoscale surface pores in ultrafiltration (UF) membranes and the support layers of reverse osmosis (RO) membranes. Based on SEM, the conventional understanding is that membranes typically have low surface porosities of <10%. We demonstrated and quantified how the high acceleration voltage during SEM imaging and the sputtered-metal coating thickness required for SEM systematically underestimate membrane surface porosity and pore size. We showed that imaging a commercial UF membrane at 1, 5, and 10 kV reduced the measured surface porosity from 10.3 ± 0.3% (1 kV) to 6.3 ± 0.4% (10 kV), while increasing the Pt coating thickness from 1.5 to 5 nm reduced the porosity by 54% for the UF membrane (12.9 ± 0.9% to 5.8 ± 0.6%) and 46% for an RO support (13.1 ± 0.6% to 7.0 ± 0.2%). To account for the coating thickness, we then developed a digital correction method that simulates pore dilation, enabling the surface pore structure to be estimated for uncoated membranes. Pore dilation yielded uncoated surface porosity values of 23% for the UF membrane and 20% for the RO support, which are approximately 3-fold greater than the directly observed values for a typical coating thickness of 4 nm. Similarly, mean pore diameters for uncoated membranes were 2-fold greater for the UF membrane and 1.5-fold greater for the RO support than directly observed. Critically, the dilation-derived pore-size distributions agreed with low-flux dextran-retention measurements fitted with the Bungay-Brenner model. Our results suggest that the surface porosities and pore sizes of nanoporous membranes are much larger than previously understood, which has major implications for structure/transport relationships. For future nanoscale pore analysis of membranes (and other nanoporous materials), we recommend low acceleration voltage (1 kV), minimal coatings (1-2 nm), and digital dilation to account for coating-induced artifacts.

Scanning/transmission electron microscopy (STEM) is a powerful characterization tool for a wide range of materials. Over the years, STEMs have been extensively used for in situ studies of structural evolution and dynamic processes. A limited number of STEM instruments are equipped with a secondary electron (SE) detector in addition to the conventional transmitted electron detectors, i.e. the bright-field (BF) and annular dark-field (ADF) detectors. Such instruments are capable of simultaneous BF-STEM, ADF-STEM and SE-STEM imaging. These methods can reveal the 'bulk' information from BF and ADF signals and the surface information from SE signals for materials <200 nm thick. This review first summarizes the field of in situ STEM research, followed by the generation of SE signals, SE-STEM instrumentation and applications of SE-STEM analysis. Combining with various in situ heating, gas reaction and mechanical testing stages based on microelectromechanical systems (MEMS), we show that simultaneous SE-STEM imaging has found applications in studying the dynamics and transient phenomena of surface reconstructions, exsolution of catalysts, lunar and planetary materials and mechanical properties of 2D thin films. Finally, we provide an outlook on the potential advancements in SE-STEM from the perspective of sample-related factors, instrument-related factors and data acquisition and processing.

Organic redox-active carbon composites can be used as sustainable electrode materials in electrochemical energy storage systems. Among numerous redox active species, peripherally dodecafluorinated boron subphthalocyanines (F12BsubPcs) have shown electrochemical redox activities in the solution phase. Nonetheless, the electrochemical properties of solid F12BsubPcs when compositing with nano carbon warrants further investigation for potential applications in energy storage. In this work, nanometer scale axially brominated F12BsubPcs (Br-F12BsubPcs) were coated onto bare graphitized multiwalled carbon nanotubes (GCNT) and COOH-functionalized GCNT (COOH-GCNT) by a facile dip coating method to produce two composites and to compare the effects of the surface functional group interactions with Br-F12BsubPcs. While the surface chemical and morphological characterizations confirmed the presence of Br-F12BsubPc coating on both bare and COOH-GCNTs, the coverage on the latter was higher. Cyclic voltammetric studies in acidic electrolyte revealed a highly reversible redox couple on both composites with Br-F12BsubPc coated COOH-GCNT demonstrating up to c.a. 70% higher redox peak currents than with Br-F12BsubPc coated GCNT. Further analyses of the coated COOH-GCNT suggested a 2-electron transfer process. The charge transfer has fast-kinetics and a strong dependence on the proton concentration. The composites produced in this work demonstrate potential for future application in energy storage and can provide a strategy for developing BsubPc-based carbon composites.

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With the rapid development of flexible wearable electronics,the demand for stretchable energy storage devices has surged.In this work,a novel gradient-layered architecture was design based on single-pore hollow lignin nanospheres(HLNPs)-intercalated two-dimensional transition metal carbide(Ti3C2Tx MXene)for fabricating highly stretchable and durable supercapacitors.By depositing and inserting HLNPs in the MXene layers with a bottom-up decreasing gradient,a multilayered porous MXene structure with smooth ion channels was constructed by reducing the overstacking of MXene lamella.Moreover,the micro-chamber architecture of thin-walled lignin nano-spheres effectively extended the contact area between lignin and MXene to improve ion and electron accessibility,thus better utilizing the pseudocapacitive property of lignin.All these strategies effectively enhanced the capacitive performance of the electrodes.In addition,HLNPs,which acted as a protective phase for MXene layer,enhanced mechanical properties of the wrinkled stretchable electrodes by releasing stress through slip and deformation during the stretch-release cycling and greatly improved the struc-tural integrity and capacitive stability of the electrodes.Flexible electrodes and sym-metric flexible all-solid-state supercapacitors capable of enduring 600％uniaxial tensile strain were developed with high specific capacitances of 1273 mF cm-2(241 F g-1)and 514 mF cm-2(95 F g-1),respectively.Moreover,their capacitances were well preserved after 1000 times of 600％stretch-release cycling.This study showcased new possibilities of incorporating biobased lignin nanospheres in energy storage devices to fabricate stretchable devices leveraging synergies among various two-dimensional nanomaterials.

Redox-active carbon composite-based electrodes, especially nitrogen-based redox active materials, can provide high power and energy storage in electrochemical capacitors. These materials include porphyrin macrocycles which are found in nature and possess unique electronic and redox-active properties from their large π-conjugated systems [1], [2]. When compositing with carbon-based materials such as carbon nanotubes (CNTs), they have shown increased stability and long-term performance. Previous work using macrocyclic tetraphenyl porphyrin sulfonate (TPPS) in CNT-based composites demonstrated improved capacitive profiles, better interfacial kinetics, and charge retention introduced in capacitive electrodes [3], [4]. On the other hand, conducting polymers with π-conjugated backbones also enabled high charge storage when used in composites [5]. To further advance these capabilities, the effects and mechanisms of surface functionalities of carbon substrates need to be investigated. For example, the presence of carboxyl groups on CNTs has been shown to improve charge storage through favourable interfacial interactions in some conducting polymers [6], [7]. The challenge as highlighted in Figure 1 lies in understanding which redox-active species, e.g. macrocycle or conducting polymer, will favour certain surface functionalities based on the nature of their interactions. Thus, a systematic investigation to design and create desirable composites and interactions for high energy and power densities, and to extend to low-cost carbon sources including waste biomass-based activated carbons. In this work, we conducted a systematic study comparing the effect of several surface functionalities like carboxyl groups on TPPS macrocycles and on conducting polymer-based carbon composites to answer the question on why certain surface functionalities are favored for each species. Preliminary studies have shown presence of TPPS has increased the capacitive profiles, reaction kinetics and rate capabilities of CNT composites, exceeding the conducting polymer counterparts. But this capacitive increase can be further improved through surface modification. This study leveraged layer-by-layer deposition approaches to fabricate redox-active carbon composites, followed by electrochemical characterizations using cyclic voltammetry and electrochemical impedance spectroscopy. Surface morphology was studied using electron microscopy while surface functional groups were investigated using x-ray photoelectron spectroscopy. The findings from this study can be used to implement systematic surface modification for redox-active carbon composites to improve energy storage, towards a more sustainable future. References [1] P. Gao et al., “A Porphyrin Complex as a Self-Conditioned Electrode Material for High-Performance Energy Storage,” Angewandte Chemie International Edition, vol. 56, no. 35, pp. 10341–10346, Aug. 2017, doi: 10.1002/ANIE.201702805. [2] H. M. Castro-Cruz, L. R. Arias-Aranda, N. Farfán, E. Xochitiotzi-Flores, and N. A. Macías-Ruvalcaba, “Elucidating the Electroreduction Mechanism of the Monoprotonated Octaethylporphyrin. A Comparative Study with the Diprotonated Octaethyl- and meso-Tetraphenyl-porphyrins,” J Electrochem Soc, vol. 167, no. 15, p. 155507, Aug. 2020, doi: 10.1149/1945-7111/ABAAE4. [3] J. N’Diaye, M. Elshazly, and K. Lian, “Capacitive charge storage of tetraphenylporphyrin sulfonate-CNT composite electrodes,” Electrochim Acta, vol. 389, p. 138593, Sep. 2021, doi: 10.1016/J.ELECTACTA.2021.138593. [4] J. N’Diaye, M. Elshazly, and K. Lian, “Unraveling Synergistic Redox Interactions in Tetraphenylporphyrin-Polyluminol-Carbon Nanotube Composite for Capacitive Charge Storage,” ACS Appl Mater Interfaces, vol. 14, no. 24, pp. 28359–28369, Jun. 2022, doi: 10.1021/ACSAMI.2C04882/SUPPL_FILE/AM2C04882_SI_001.PDF. [5] J. Yang, Y. Liu, S. Liu, L. Li, C. Zhang, and T. Liu, “Conducting polymer composites: material synthesis and applications in electrochemical capacitive energy storage,” Mater Chem Front, vol. 1, no. 2, pp. 251–268, Feb. 2017, doi: 10.1039/C6QM00150E. [6] R. Bagchi, M. Elshazly, J. N’Diaye, D. Yu, J. Y. Howe, and K. Lian, “Effects of Carboxyl Functionalized CNT on Electrochemical Behaviour of Polyluminol-CNT Composites,” Chemistry 2022, Vol. 4, Pages 1561-1575, vol. 4, no. 4, pp. 1561–1575, Nov. 2022, doi: 10.3390/CHEMISTRY4040103. [7] B. Zhang et al., “A facile synthesis of polypyrrole/carbon nanotube composites with ultrathin, uniform and thickness-tunable polypyrrole shells,” Nanoscale Res Lett, vol. 6, no. 1, pp. 1–9, Jun. 2011, doi: 10.1186/1556-276X-6-431/FIGURES/7. Figure 1

Journal Article Facile Low-voltage SEM Imaging of Lignocellulosic Biomass using a Low-cost Methanesulfonate Ionic Liquid Get access Dian Yu, Dian Yu Department of Materials Science and Engineering, University of Toronto, Toronto, ON, Canada Corresponding author: dianjack.yu@utoronto.ca Search for other works by this author on: Oxford Academic Google Scholar Patrick Woo, Patrick Woo Hitachi High-Tech Canada, Inc., Toronto, ON, Canada Search for other works by this author on: Oxford Academic Google Scholar Keryn Lian, Keryn Lian Department of Materials Science and Engineering, University of Toronto, Toronto, ON, Canada Search for other works by this author on: Oxford Academic Google Scholar Jane Howe Jane Howe Department of Materials Science and Engineering, University of Toronto, Toronto, ON, CanadaHitachi High-Tech Canada, Inc., Toronto, ON, Canada Search for other works by this author on: Oxford Academic Google Scholar Microscopy and Microanalysis, Volume 29, Issue Supplement_1, 1 August 2023, Pages 880–882, https://doi.org/10.1093/micmic/ozad067.435 Published: 22 July 2023

We used a novel Peltier anticontamination device (PAC) to reduce carbon contamination upon electron beam irradiation in scanning electron microscopy through a reduction of hydrocarbon molecules in the specimen chamber. Unlike liquid-nitrogen based cold traps, the PAC operates free of user maintenance and is suitable for lengthy imaging sessions without degradation of the anticontamination performance. Its performance as an alternative cold trap method provides considerable reduction of electron beam-assisted carbon build-up. We compared the thickness of carbon contamination deposited upon prolonged electron beam scans with the PAC system on and off. Topographical structures of the carbon build-up were characterized using atomic force microscopy. We report that under identical beam parameters, thickness of the carbon contamination was reduced by over 79 % for area scans (1.2 × 1.2 µm2), and by two orders of magnitude for stationary point scans when the PAC cooling mode is engaged.

The effect of carboxyl groups on the redox activity of polyluminol-carbon nanotube composites was studied. Carboxyl groups were selected due to their known contributions toward surface wettability and pseudocapacitance while often present on naturally derived low-cost porous carbons. Density functional theory (DFT) predicted energetically favoured bonding and a significantly reduced band gap between the luminol and carboxylated graphene relative to that of bare graphene, suggesting improved charge storage for carboxylated carbon substrates. The prediction was validated using bare carbon nanotubes (CNTs) and carboxylated CNTs (COOH-CNTs) as the substrates for in situ chemical polymerized luminol (CpLum). Surface morphological studies showed a ca. 1.1 nm thick coating of CpLum on CNT (CpLum/CNT) and a ca. 1.3 nm on COOH-CNT (CpLum/COOH-CNT), while surface chemical analysis revealed ca. 10% nitrogen from CpLum on both CpLum/CNT and CpLum/COOH-CNT. However, with merely 4.4% of COOH functionalization, CpLum/COOH-CNT was able to store more charge (137.1 ± 17.1 C cm−3) relative to CpLum/CNT (86.1 ± 14.1 C cm−3) and had increased charge retention over 5000 cycles. The insights from these studies can be used to engineer the surface of carbons such as CNTs and ACs to improve the interfacial properties for redox active materials and composites.

Microplastics quantification and classification are demanding jobs to monitor microplastic pollution and evaluate the potential health risks. In this paper, microplastics from daily supplies in diverse chemical compositions and shapes are imaged by scanning electron microscopy. It offers a greater depth and finer details of microplastics at a wider range of magnification than visible light microscopy or a digital camera, and permits further chemical composition analysis. However, it is labour-intensive to manually extract microplastics from micrographs, especially for small particles and thin fibres. A deep learning approach facilitates microplastics quantification and classification with a manually annotated dataset including 237 micrographs of microplastic particles (fragments or beads) in the range of 50 μm-1 mm and fibres with diameters around 10 μm. For microplastics quantification, two deep learning models (U-Net and MultiResUNet) were implemented for semantic segmentation. Both significantly outmatched conventional computer vision techniques and achieved a high average Jaccard index over 0.75. Especially, U-Net was combined with object-aware pixel embedding to perform instance segmentation on densely packed and tangled fibres for further quantification. For shape classification, a fine-tuned VGG16 neural network classifies microplastics based on their shapes with high accuracy of 98.33%. With trained models, it takes only seconds to segment and classify a new micrograph in high accuracy, which is remarkably cheaper and faster than manual labour. The growing datasets may benefit the identification and quantification of microplastics in environmental samples in future work.