Sample holders for transmission electron microscopy (TEM) based on micro‐electro‐mechanical systems (MEMS) have recently become popular for investigating the behavior of nanomaterials under in situ or environmental conditions. The accuracy and reproducibility of these in situ holders are essential to ensure the reliability of experimental results. In addition, the uniformity of an applied temperature trigger across the MEMS chip is a crucial parameter. In this work, it is measured the temperature homogeneity of MEMS‐based heating sample supports by locally analyzing the dynamics of heat‐induced alloying of Au@Ag nanoparticles located in different regions of the support through quantitative fast high‐angle annular dark‐field scanning TEM tomography. These results demonstrate the superior temperature homogeneity of a microheater design based on a heating element shaped as a circular spiral with a width decreasing outwards compared to a double spiral‐shaped designed microheater. The proposed approach to measure the local temperature homogeneity based on the thermal properties of bimetallic nanoparticles will support the future development of MEMS‐based heating supports with improved thermal properties and in situ studies where high precision in the temperature at a certain position is required.

Journal Article Benefits of Using a 4 srad XEDS Detector in Quantitative 3D-Compositional Analysis of Core@shell Nanoparticles Get access Qiongyang Chen, Qiongyang Chen Electron Microscopy for Materials Science, University of Antwerp, Antwerp, Belgium Search for other works by this author on: Oxford Academic Google Scholar Adrian Pedrazo-Tardajos, Adrian Pedrazo-Tardajos Electron Microscopy for Materials Science, University of Antwerp, Antwerp, Belgium Search for other works by this author on: Oxford Academic Google Scholar Maarten Wirix, Maarten Wirix Thermo Fisher Scientific, Eindhoven, The Netherlands Search for other works by this author on: Oxford Academic Google Scholar Lin Jiang, Lin Jiang Thermo Fisher Scientific, Hillsboro, OR, USA Search for other works by this author on: Oxford Academic Google Scholar Bert Freitag, Bert Freitag Thermo Fisher Scientific, Eindhoven, The Netherlands Search for other works by this author on: Oxford Academic Google Scholar Sara Bals Sara Bals Electron Microscopy for Materials Science, University of Antwerp, Antwerp, Belgium Corresponding author: sara.bals@uantwerpen.be Search for other works by this author on: Oxford Academic Google Scholar Microscopy and Microanalysis, Volume 28, Issue S1, 1 August 2022, Pages 554–555, https://doi.org/10.1017/S143192762200280X Published: 01 August 2022

Understanding the thermal stability of bimetallic nanoparticles is of vital importance to preserve their functionalities during their use in a variety of applications. In contrast to well-studied bimetallic systems such as Au@Ag, heat-induced morphological and compositional changes in Au@Pt nanoparticles are insufficiently understood, even though Au@Pt is an important material for catalysis. To investigate the thermal instability of Au@Pt nanorods at temperatures below their bulk melting point, we combined in situ heating with two- and three-dimensional electron microscopy techniques, including three-dimensional energy-dispersive X-ray spectroscopy. The experimental results were used as input for molecular dynamics simulations, to unravel the mechanisms behind the morphological transformation of Au@Pt core-shell nanorods. We conclude that thermal stability is influenced not only by the degree of coverage of Pt on Au but also by structural details of the Pt shell.

Journal Article Thermal Stability of Au@Pt Nanoparticles Investigated by Electron Tomography Get access Adrián Pedrazo-Tardajos, Adrián Pedrazo-Tardajos EMAT, University of Antwerp, Antwerp, BelgiumNANOlab Center of Excellence, University of Antwerp, Belgium Search for other works by this author on: Oxford Academic Google Scholar Ece Arslan Irmak, Ece Arslan Irmak EMAT, University of Antwerp, Antwerp, BelgiumNANOlab Center of Excellence, University of Antwerp, Belgium Search for other works by this author on: Oxford Academic Google Scholar Vished Kumar, Vished Kumar CIC biomaGUNE, Basque Research and Technology Alliance (BRTA), Donostia-San Sebastián, Spain Search for other works by this author on: Oxford Academic Google Scholar Ana Sánchez-Iglesias, Ana Sánchez-Iglesias CIC biomaGUNE, Basque Research and Technology Alliance (BRTA), Donostia-San Sebastián, SpainCIBER de Bioingeniería, Biomateriales y Nanomedicina (CIBER-BBN), Donostia-San Sebastián, Spain Search for other works by this author on: Oxford Academic Google Scholar Qiongyang Chen, Qiongyang Chen EMAT, University of Antwerp, Antwerp, BelgiumNANOlab Center of Excellence, University of Antwerp, Belgium Search for other works by this author on: Oxford Academic Google Scholar Bert Freitag, Bert Freitag Thermo Fisher Scientific, Strijp-T, Eindhoven, The Netherlands Search for other works by this author on: Oxford Academic Google Scholar Wiebke Albrecht, Wiebke Albrecht EMAT, University of Antwerp, Antwerp, BelgiumNANOlab Center of Excellence, University of Antwerp, Belgium Search for other works by this author on: Oxford Academic Google Scholar Sandra Van Aert, Sandra Van Aert EMAT, University of Antwerp, Antwerp, BelgiumNANOlab Center of Excellence, University of Antwerp, Belgium Search for other works by this author on: Oxford Academic Google Scholar Luis M Liz-Marzán, Luis M Liz-Marzán CIC biomaGUNE, Basque Research and Technology Alliance (BRTA), Donostia-San Sebastián, SpainIkerbasque, Basque Foundation for Science, Bilbao, SpainCIBER de Bioingeniería, Biomateriales y Nanomedicina (CIBER-BBN), Donostia-San Sebastián, Spain Search for other works by this author on: Oxford Academic Google Scholar Sara Bals Sara Bals EMAT, University of Antwerp, Antwerp, BelgiumNANOlab Center of Excellence, University of Antwerp, Belgium Corresponding author: sara.bals@uantwerpen.be Search for other works by this author on: Oxford Academic Google Scholar Microscopy and Microanalysis, Volume 28, Issue S1, 1 August 2022, Pages 314–316, https://doi.org/10.1017/S1431927622002033 Published: 01 August 2022

Transmission electron microscopy (TEM) combined with micro-electro-mechanical systems (MEMS) can be used to directly observe the dynamic behavior of materials under different stimuli. For example, in-situ microheaters enable researchers to investigate the thermal stability of heterogeneous nanoparticles. Hereby, accurate knowledge of the local temperature during the TEM experiments is critical. However, external-based temperature calibrations using Raman spectroscopy or infrared pyrometry might show a deviation in comparison to the actual temperature when the nanochip is used inside the TEM. Together with the possible errors introduced by the aforementioned calibration procedures, the temperature inhomogeneity that can be intrinsically present in a microheater design also limits its temperature accuracy. Moreover, these temperature measurements are usually available at the scale that is too large for tracking the local temperature of nanoparticles on a nanochip. Additionally, when using insitu microheaters, the nanoparticles are deposited on the SiNx film of the nanochip and the local heat transfer from the SiNx film to the nanoparticles remains unclear. Here, we propose a method to measure the local temperature of the individual nanoparticle during in-situ heating experiments by using quantitative high-angle annular darkfield scanning TEM (HAADF-STEM) tomography.

Single-atom catalysts (SACs) have recently attracted broad scientific interests due to their unique structural feature, the single-atom dispersion. Optimized electronic structure as well as high stability are required for single-atom catalysts to enable efficient electrochemical production of H2O2. Herein, we report a facile synthesis method that stabilizes atomic Pd species on the reduced graphene oxide/Ndoped carbon hollow carbon nanospheres (Pd1/N-C). Pd1/N-C exhibited remarkable electrochemical H2O2 production rate with high faradaic efficiency, reaching 80%. The single-atom structure and its high H2O2 production rate were maintained even after 10,000 cycle stability test. The existence of single-atom Pd as well as its coordination with N species is responsible for its high activity, selectivity, and stability. The N coordination number and substrate doping around Pd atoms are found to be critical for an optimized adsorption energy of intermediate *OOH, resulting in efficient electrochemical H2O2 production. (C) 2020 Elsevier Inc. All rights reserved.

Strain engineering is a highly effective tool for tuning the lattice parameter and in turn optimizing the optical, electronic, and chemical properties of numerous functional materials. In conventional methods, the strain is imposed from an additional heterogeneous substrate, bringing extra composition/phase that disturbs the mechanism investigations of the effects of lattice parameters on material properties. Here, we report a convertible-precursor-induced growing method to fulfill the elongation of the uniaxial lattice parameter of anatase TiO2 with a complex structure of single-crystal-like hierarchical arrays, without changing the composition, morphology, phase, and surface states. This methodology relies on a precursor-induced oriented growth and lattice parameter modulation on the basis of the lattice mismatch from the precursor. Unlike conventional substrate-manipulating methods, the employed precursor can be converted to the final materials (i.e., anatase TiO2), which can eliminate the effects of the additional substrate. It is found that for anatase TiO2, the elongation of lattice parameter a leads to the shift-up of the conduction band bottom and can thus accelerate the reduction reactions of O2. The elongation of lattice parameter a and unique structural features make the TiO2 arrays highly active for photocatalytic degradation of toluene in air, with a turnover frequency (TOF) 3.8 times and 2.1 times, respectively, that of the normal TiO2 arrays and P25 powder under ultraviolet irradiation. The enhanced reduction capability is further confirmed by the much-improved efficiency to assist the photoreduction of Cr(VI) in water.

In computed tomography, the reconstruction is typically obtained on a voxel grid. In this work, however, we propose a mesh-based reconstruction method. For tomographic problems, 3D meshes have mostly been studied to simulate data acquisition, but not for reconstruction, for which a 3D mesh means the inverse process of estimating shapes from projections. In this paper, we propose a differentiable forward model for 3D meshes that bridge the gap between the forward model for 3D surfaces and optimization. We view the forward projection as a rendering process, and make it differentiable by extending recent work in differentiable rendering. We use the proposed forward model to reconstruct 3D shapes directly from projections. Experimental results for single-object problems show that the proposed method outperforms traditional voxel-based methods on noisy simulated data. We also apply the proposed method on electron tomography images of nanoparticles to demonstrate the applicability of the method on real data.

本文通过一步高温烧结石墨烯量子点制备了一种具有转角石墨烯结构的碳纳米材料,并利用球差矫正电子显微镜进行表征.该碳纳米材料中存在大量纳米尺度的孔隙和由几层小片层的石墨烯以随机旋转角堆垛形成的结构.通过HRTEM图像的快速傅立叶变换(FFT)分析来区分每个旋转角度的石墨烯层,并且多层石墨烯的堆叠还能引起更复杂的层状结构.纳米尺度的局域型转角堆叠结构、孔隙意味着其具有多种可能的带隙结构,使这种碳材料有可能作为转角石墨烯结构与性能关联的研究平台;并且此类碳材料在碱溶液处理后,表现出类似于Pt催化剂的催化特性和一种商业化的20％Pt/C催化剂的催化活性.

Adjacent C–O−–K+ (Na+) groups in the surface of non-doped carbon materials create active sites for the oxygen reduction reaction.

纳米线及纳米管材料常被用于透射电镜中进行原位偏压下的电学测试,例如,对其场发射性能与电学击穿性质的测量,电场下电荷非均匀分布的信息可以使得我们对单根纳米线的性质做出更加定量的监控与判断.本文作者使用了同轴电子全息的方法,可以简单快捷地仅从单张离焦像中计算出沿纳米线的电荷分布.通过结合此方法与原位偏压技术,可以对在电场作用下碳化硅纳米线中的电荷分布进行成像,从无偏压时的均匀分布到受到电场调制后呈现出增大的梯度均可以被定量算出,且对电荷的灵敏度可优于1 e/nm.本方法可以应用于原位条件下进行快捷高效的动态电荷表征.

Mapping the charge distribution in nano scale systems still is a difficult task, but is important to provide fundamental insights into the properties of materials. We demonstrate how in-line holography in transmission electron microscopy can be used to extract the charge distribution in the nanowire in a quantitative way. This technique can realize a fast acquisition of delicate charge variations. By taking advantage of the possibilities of in-situ electron microscopy, variations of the external field can be used to modulate the charge distribution. Because of the fast response to charge variations, this method provides an efficient probing tool for detecting dynamic charge redistribution.

Small molecules play critical roles in life science, yet their facile detection and imaging in physiological or pathological settings remain a challenge. Matrix-assisted laser desorption ionization mass spectrometry (MALDI MS) is a powerful tool for molecular analysis. However, conventional organic matrices (CHCA, DHB, etc.) used in assisting analyte ionization suffer from intensive background noise in the mass region below m/z 700, which hinders MALDI MS applications for small-molecule detection. Here, we report that a hydroxyl-group dominated graphite dot (GD) matrix overcomes limitations of conventional matrices and allows MALDI MS to be used in fast and high throughput analysis of small biomolecules. GDs exhibit extremely low background noise and ultrahigh sensitivity (with limit of detection <1 fmol) in MALDI MS. This approach allows identification of complex oligosaccharides, detection of low-molecular weight components in traditional Chinese herbs, and facile analysis of puerarin and its metabolites in serum without purification. Moreover, we show that the GDs provide an effective matrix for the direct imaging or spatiotemporal mapping of small molecules and their metabolites (m/z < 700) simultaneously at the suborgan tissue level. Density functional theory calculations further provide the mechanistic basis of GDs as an effective MALDI matrix in both the positive-ion and negative-ion modes. Collectively, our work uncovered a useful matrix which reshapes MALDI MS technology for a wide range of applications in biology and medicine.