Towards a Top-Down Approach in Materials Science

Motivated by their importance in chemistry, physics, astronomy and materials science, we investigate routes to the formation of large polycyclic aromatic hydrocarbon (PAH) molecules and the fullerene C60 from specific smaller PAH building blocks. The behaviour of selected PAH molecules under electron (using transmission electron microscopy, TEM) and laser irradiation is examined, where four specific PAHs—anthracene, pyrene, perylene and coronene—are assembling into larger structures and fullerenes. This contrasts with earlier TEM studies in which large graphene flakes were shown to transform into fullerenes via a top-down route. A new combined approach is presented in which spectrometric and microscopic experimental techniques exploit the stabilisation of adsorbed molecules through supramolecular interactions with a graphene substrate and enable the molecules to be characterised and irradiated sequentially. Thereby allowing initiation of transformation and characterisation of the resultant species by both mass spectrometry and direct-space imaging. We investigate the types of large PAH molecule that can form from smaller PAHs, and discuss the potential of a “bottom-up” followed by “top-down” mechanism for forming C60.

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Modular and Integrated Systems for Nanoparticle and Microparticle Synthesis—A Review

Biosensors ◽

10.3390/bios10110165 ◽

2020 ◽

Vol 10 (11) ◽

pp. 165

Author(s):

Hongda Lu ◽

Shi-Yang Tang ◽

Guolin Yun ◽

Haiyue Li ◽

Yuxin Zhang ◽

...

Keyword(s):

Physical Properties ◽

Materials Science ◽

Synthesis Method ◽

Integrated Systems ◽

Top Down ◽

Large Space ◽

Bottom Up ◽

On Demand ◽

Complex Operation ◽

Expensive Equipment

Nanoparticles (NPs) and microparticles (MPs) have been widely used in different areas of research such as materials science, energy, and biotechnology. On-demand synthesis of NPs and MPs with desired chemical and physical properties is essential for different applications. However, most of the conventional methods for producing NPs/MPs require bulky and expensive equipment, which occupies large space and generally need complex operation with dedicated expertise and labour. These limitations hinder inexperienced researchers to harness the advantages of NPs and MPs in their fields of research. When problems individual researchers accumulate, the overall interdisciplinary innovations for unleashing a wider range of directions are undermined. In recent years, modular and integrated systems are developed for resolving the ongoing dilemma. In this review, we focus on the development of modular and integrated systems that assist the production of NPs and MPs. We categorise these systems into two major groups: systems for the synthesis of (1) NPs and (2) MPs; systems for producing NPs are further divided into two sections based on top-down and bottom-up approaches. The mechanisms of each synthesis method are explained, and the properties of produced NPs/MPs are compared. Finally, we discuss existing challenges and outline the potentials for the development of modular and integrated systems.

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The destruction of the golden calf (Ex 32:20): A materials science perspective

Verbum et Ecclesia ◽

10.4102/ve.v42i1.2175 ◽

2021 ◽

Vol 42 (1) ◽

Author(s):

Tarcicio Gaitán Briceño ◽

Emigdio Mendoza Fandiño ◽

Piedad Gañán Rojo

Keyword(s):

Old Testament ◽

Materials Science ◽

Experimental Results ◽

Human Consumption ◽

Appropriate Use ◽

Top Down ◽

Technical Aspects ◽

Golden Calf ◽

It Impacts ◽

First Time

One of the most fascinating and heavily debated episodes involving gold in the Old Testament is the destruction of the golden calf described in Exodus 32:20. This study considers, for the first time, this episode from a materials science perspective. Textual analysis and experimental results indicate that it is plausible to make a gold mixture fit for later human consumption by using the three steps described in the passage. The results thus suggest that Exodus 32:20 could be an ancient reference to the most commented-upon materials processes of our day: reduce the size of matter through a top-down approach.Intradisciplinary and/or interdisciplinary implications: This article brings for the first time an approach between theological analysis and a support by materials sciences to evaluate the technical viability of the destruction of the golden calf described in Exodus 32:20. It impacts the obtained results and indicates the appropriate use of technical aspects of the writers of this text.

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Trends in Electron Energy Loss Spectroscopy

Proceedings, annual meeting, Electron Microscopy Society of America ◽

10.1017/s0424820100078675 ◽

1977 ◽

Vol 35 ◽

pp. 228-229

Author(s):

C. Colliex ◽

P. Trebbia

Keyword(s):

Energy Loss ◽

Electron Energy ◽

Electron Energy Loss Spectroscopy ◽

Materials Science ◽

Analytical Technique ◽

Recent Developments ◽

Quantitative Results ◽

Electron Microscopes ◽

Electron Energy Loss ◽

Primary Electrons

The physical foundations for the use of electron energy loss spectroscopy towards analytical purposes, seem now rather well established and have been extensively discussed through recent publications. In this brief review we intend only to mention most recent developments in this field, which became available to our knowledge. We derive also some lines of discussion to define more clearly the limits of this analytical technique in materials science problems.The spectral information carried in both low ( 0<ΔE<100eV ) and high ( >100eV ) energy regions of the loss spectrum, is capable to provide quantitative results. Spectrometers have therefore been designed to work with all kinds of electron microscopes and to cover large energy ranges for the detection of inelastically scattered electrons (for instance the L-edge of molybdenum at 2500eV has been measured by van Zuylen with primary electrons of 80 kV). It is rather easy to fix a post-specimen magnetic optics on a STEM, but Crewe has recently underlined that great care should be devoted to optimize the collecting power and the energy resolution of the whole system.

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Electron holography in materials science

Proceedings, annual meeting, Electron Microscopy Society of America ◽

10.1017/s0424820100087665 ◽

1991 ◽

Vol 49 ◽

pp. 670-671

Author(s):

Hannes Lichte ◽

Edgar Voelkl

Keyword(s):

Electron Microscopy ◽

Transmission Electron Microscopy ◽

Materials Science ◽

Fourier Spectrum ◽

Object Wave ◽

Electron Holography ◽

Reconstruction Procedure ◽

Numerical Reconstruction ◽

Transmission Electron ◽

Unique Interpretation

The object wave o(x,y) = a(x,y)exp(iφ(x,y)) at the exit face of the specimen is described by two real functions, i.e. amplitude a(x,y) and phase φ(x,y). In stead of o(x,y), however, in conventional transmission electron microscopy one records only the real intensity I(x,y) of the image wave b(x,y) loosing the image phase. In addition, referred to the object wave, b(x,y) is heavily distorted by the aberrations of the microscope giving rise to loss of resolution. Dealing with strong objects, a unique interpretation of the micrograph in terms of amplitude and phase of the object is not possible. According to Gabor, holography helps in that it records the image wave completely by both amplitude and phase. Subsequently, by means of a numerical reconstruction procedure, b(x,y) is deconvoluted from aberrations to retrieve o(x,y). Likewise, the Fourier spectrum of the object wave is at hand. Without the restrictions sketched above, the investigation of the object can be performed by different reconstruction procedures on one hologram. The holograms were taken by means of a Philips EM420-FEG with an electron biprism at 100 kV.

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Zero-loss omega-filtered REM and RHEED on the new Zeiss 912

Proceedings, annual meeting, Electron Microscopy Society of America ◽

10.1017/s0424820100087392 ◽

1991 ◽

Vol 49 ◽

pp. 616-617

Author(s):

J.C.H. Spence ◽

J. Mayer

Keyword(s):

Electron Microscopy ◽

Materials Science ◽

Surface States ◽

Ccd Camera ◽

Dark Field ◽

Ion Pump ◽

Magnetic Imaging ◽

Reflection Electron Microscopy ◽

Diffraction Patterns ◽

Large Background

The Zeiss 912 is a new fully digital, side-entry, 120 Kv TEM/STEM instrument for materials science, fitted with an omega magnetic imaging energy filter. Pumping is by turbopump and ion pump. The magnetic imaging filter allows energy-filtered images or diffraction patterns to be recorded without scanning using efficient parallel (area) detection. The energy loss intensity distribution may also be displayed on the screen, and recorded by scanning it over the PMT supplied. If a CCD camera is fitted and suitable new software developed, “parallel ELS” recording results. For large fields of view, filtered images can be recorded much more efficiently than by Scanning Reflection Electron Microscopy, and the large background of inelastic scattering removed. We have therefore evaluated the 912 for REM and RHEED applications. Causes of streaking and resonance in RHEED patterns are being studied, and a more quantitative analysis of CBRED patterns may be possible. Dark field band-gap REM imaging of surface states may also be possible.

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Dynamical Scattering in Crystalline Biological Specimens. I. Criteria of Validity for Scattering Approximations

Proceedings, annual meeting, Electron Microscopy Society of America ◽

10.1017/s042482010011458x ◽

1975 ◽

Vol 33 ◽

pp. 192-193

Author(s):

Robert M. Glaeser ◽

Bing K. Jap

Keyword(s):

Biological Sciences ◽

Electron Microscopy ◽

Electron Microscope ◽

Electron Diffraction ◽

Born Approximation ◽

Materials Science ◽

Image Data ◽

Dynamical Effect ◽

Crystallographic Structure ◽

Electron Microscope Image

The dynamical scattering effect, which can be described as the failure of the first Born approximation, is perhaps the most important factor that has prevented the widespread use of electron diffraction intensities for crystallographic structure determination. It would seem to be quite certain that dynamical effects will also interfere with structure analysis based upon electron microscope image data, whenever the dynamical effect seriously perturbs the diffracted wave. While it is normally taken for granted that the dynamical effect must be taken into consideration in materials science applications of electron microscopy, very little attention has been given to this problem in the biological sciences.

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Electron spectroscopic imaging and diffraction

Proceedings, annual meeting, Electron Microscopy Society of America ◽

10.1017/s0424820100087847 ◽

1991 ◽

Vol 49 ◽

pp. 706-707

Author(s):

M. Rühle ◽

J. Mayer ◽

J.C.H. Spence ◽

J. Bihr ◽

W. Probst ◽

...

Keyword(s):

Materials Science ◽

Electron Spectroscopic Imaging ◽

Magnetic Filter ◽

Magnetic Imaging ◽

Illumination System ◽

Probe Size ◽

Diffraction Patterns ◽

Fritz Haber ◽

Koehler Illumination ◽

First Time

A new Zeiss TEM with an imaging Omega filter is a fully digitized, side-entry, 120 kV TEM/STEM instrument for materials science. The machine possesses an Omega magnetic imaging energy filter (see Fig. 1) placed between the third and fourth projector lens. Lanio designed the filter and a prototype was built at the Fritz-Haber-Institut in Berlin, Germany. The imaging magnetic filter allows energy-filtered images or diffraction patterns to be recorded without scanning using efficient area detection. The energy dispersion at the exit slit (Fig. 1) results in ∼ 1.5 μm/eV which allows imaging with energy windows of ≤ 10 eV. The smallest probe size of the microscope is 1.6 nm and the Koehler illumination system is used for the first time in a TEM. Serial recording of EELS spectra with a resolution < 1 eV is possible. The digital control allows X,Y,Z coordinates and tilt settings to be stored and later recalled.

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Determination of interface width using EELS fine structure changes

Proceedings, annual meeting, Electron Microscopy Society of America ◽

10.1017/s0424820100087963 ◽

1991 ◽

Vol 49 ◽

pp. 730-731

Author(s):

Vinayak P. Dravid ◽

M.R. Notis ◽

C.E. Lyman

Keyword(s):

Fine Structure ◽

Materials Science ◽

Input Parameter ◽

Core Loss ◽

Directionally Solidified ◽

Interface Width ◽

Structure Changes ◽

Important Input ◽

Directionally Solidified Eutectics

The concept of interfacial width is often invoked in many materials science phenomena which relate to the structure and properties of internal interfaces. The numerical value of interface width is an important input parameter in diffusion equations, sintering theories as well as in many electronic devices/processes. Most often, however, this value is guessed rather than determined or even estimated. In this paper we present a method of determining the effective structural and electronic- structural width of interphase interfaces using low- and core loss fine structure effects in EELS spectra.The specimens used in the study were directionally solidified eutectics (DSEs) in the system; NiO-ZrO2(CaO), NiO-Y2O3 and MnO-ZrO2(ss). EELS experiments were carried out using a VG HB-501 FE STEM and a Hitachi HF-2000 FE TEM.

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Energy Dispersive X-Ray Measurements of thin Metal Foils

Proceedings, annual meeting, Electron Microscopy Society of America ◽

10.1017/s0424820100092098 ◽

1976 ◽

Vol 34 ◽

pp. 426-427

Author(s):

J. Bentley ◽

E. A. Kenik

Keyword(s):

Materials Science ◽

Energy Dispersive Spectrometer ◽

Thin Foil ◽

Thin Metal ◽

Energy Dispersive ◽

Thin Specimen ◽

X Ray ◽

Metal Foils ◽

Small Probe ◽

Scanning Transmission

Instruments combining a 100 kV transmission electron microscope (TEM) with scanning transmission (STEM), secondary electron (SEM) and x-ray energy dispersive spectrometer (EDS) attachments to give analytical capabilities are becoming increasingly available and useful. Some typical applications in the field of materials science which make use of the small probe size and thin specimen geometry are the chemical analysis of small precipitates contained within a thin foil and the measurement of chemical concentration profiles near microstructural features such as grain boundaries, point defect clusters, dislocations, or precipitates. Quantitative x-ray analysis of bulk samples using EDS on a conventional SEM is reasonably well established, but much less work has been performed on thin metal foils using the higher accelerating voltages available in TEM based instruments.

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