Coherent electron nanodiffraction from clean silver nano particles in a UHV STEM

1993 ◽  
Vol 51 ◽  
pp. 1058-1059
Author(s):  
J. Liu ◽  
M. Pan ◽  
G. E. Spinnler
Keyword(s):  
Supported Catalysts ◽  
Imaging Techniques ◽  
Nano Particles ◽  
Metal Particles ◽  
Shape Structure ◽  
Dynamical Simulations ◽  
Small Metal Particles ◽  
Extract Information

Small metal particles have peculiar chemical and physical properties as compared to bulk materials. They are especially important in catalysis since metal particles are common constituents of supported catalysts. The structural characterization of small particles is of primary importance for the understanding of structure-catalytic activity relationships. The shape and size of metal particles larger than approximately 5 nm in diameter can be determined by several imaging techniques. It is difficult, however, to deduce the shape of smaller metal particles. Coherent electron nanodiffraction (CEND) patterns from nano particles contain information about the particle size, shape, structure and defects etc. As part of an on-going program of STEM characterization of supported catalysts we report some preliminary results of CEND study of Ag nano particles, deposited in situ in a UHV STEM instrument, and compare the experimental results with full dynamical simulations in order to extract information about the shape of Ag nano particles.

The Characterization of Thin Platinum Films on Alumina

1986 ◽  
Vol 83 ◽  
Author(s):  
E. I. Altman ◽  
R. J. Gorte
Keyword(s):  
Particle Size ◽  
Catalytic Properties ◽  
Metal Particles ◽  
Small Particles ◽  
Oxide Substrate ◽  
Porous Oxide ◽  
Temperature Programmed ◽  
Thin Platinum ◽  
Small Metal Particles

ABSTRACTIndustrial metal catalysts are usually in the form of small metal particles supported on a porous oxide. The typical size of these metal particles ranges between 1.0 and 10.0 nm and it is well known that the particle size and the oxide substrate can affect the catalytic properties of the metal for some important reactions[1]. Previous work with adsorption on small particles has indicated that desorption temperatures[2–4] and the ability to dissociate CO[5,6] can also be affected by the particle size. To further investigate these size and substrate effects, we have examined the adsorption properties of several simple gases on small Pt particles supported on alumina using temperature programmed desorption (TPD). We will show that the desorption curves for CO, H2, and NO on these particles are very similar to curves measured on single crystals.

Preparation and Characterization of Polyimide-Silica Nanocomposites by Sol-Gel Process

2006 ◽  
Vol 111 ◽  
pp. 111-114 ◽  
Author(s):  
Yao Yi Cheng ◽  
Kun Chang Chuang
Keyword(s):  
Sol Gel ◽  
Amic Acid ◽  
Silica Content ◽  
Nano Particles ◽  
Hybrid Thin Film ◽  
Silica Nanocomposites ◽  
Sol Gel Process ◽  
Tetracarboxylic Dianhydride

Polyimide (PI)-based nanocomposites were prepared by the in-situ generation of organic silica nano-particles through a sol-gel process, combined with spin coating and multi-step curing process. In this study, silica nano-particles were introduced into the PI matrix to promote its thermal properties. Nanometer-scale composites were successfully obtained from poly(amic acid) (PAA) mixture loaded with silica. 3,3’,4,4’- Biphenyl tetracarboxylic dianhydride (BPDA) and p-phenylenediamine (p-PDA) were employed to synthesize the PAA precursor. The hybrid thin film was prepared from aminoalkoxysilane-capped PAA and tetraethoxysilane (TEOS). In this work, we investigated the effect of coupling agent, 3-aminopropyltriethoxysilane (APrTEOS). The TGA results indicate that the thermal stability of the nanocomposites can be enhanced as silica content increases. Without the incorporation of APrTEOS, less improvement can be achieved.

scholarly journals In-situ diagnostic of femtosecond laser probe pulses for high resolution ultrafast imaging

2021 ◽  
Vol 10 (1) ◽  
Author(s):  
Chen Xie ◽  
Remi Meyer ◽  
Luc Froehly ◽  
Remo Giust ◽  
Francois Courvoisier
Keyword(s):  
Spatial Frequency ◽  
Probe Pulse ◽  
Imaging Techniques ◽  
Frame Rate ◽  
Pulse Front ◽  
Pump Probe ◽  
Ultrafast Imaging ◽  
Probe Delay

AbstractUltrafast imaging is essential in physics and chemistry to investigate the femtosecond dynamics of nonuniform samples or of phenomena with strong spatial variations. It relies on observing the phenomena induced by an ultrashort laser pump pulse using an ultrashort probe pulse at a later time. Recent years have seen the emergence of very successful ultrafast imaging techniques of single non-reproducible events with extremely high frame rate, based on wavelength or spatial frequency encoding. However, further progress in ultrafast imaging towards high spatial resolution is hampered by the lack of characterization of weak probe beams. For pump–probe experiments realized within solids or liquids, because of the difference in group velocities between pump and probe, the determination of the absolute pump–probe delay depends on the sample position. In addition, pulse-front tilt is a widespread issue, unacceptable for ultrafast imaging, but which is conventionally very difficult to evaluate for the low-intensity probe pulses. Here we show that a pump-induced micro-grating generated from the electronic Kerr effect provides a detailed in-situ characterization of a weak probe pulse. It allows solving the two issues of absolute pump–probe delay determination and pulse-front tilt detection. Our approach is valid whatever the transparent medium with non-negligible Kerr index, whatever the probe pulse polarization and wavelength. Because it is nondestructive and fast to perform, this in-situ probe diagnostic can be repeated to calibrate experimental conditions, particularly in the case where complex wavelength, spatial frequency or polarization encoding is used. We anticipate that this technique will enable previously inaccessible spatiotemporal imaging in a number of fields of ultrafast science at the micro- and nanoscale.

scholarly journals Multispectral Imaging and p-XRF for the Non-Invasive Characterization of the Anonymous Devotional Painting ‘Maria Santissima delle Grazie’ from Mirabella Imbáccari (Sicily, Italy)

Heritage ◽  
2021 ◽  
Vol 4 (3) ◽  
pp. 2320-2336
Author(s):  
Antonella Privitera ◽  
Maria Francesca Alberghina ◽  
Elèna Privitera ◽  
Salvatore Schiavone
Keyword(s):  
Multispectral Imaging ◽  
Chemical Elements ◽  
Imaging Techniques ◽  
Religious Community ◽  
Oil Painting ◽  
Spectrometry Analysis ◽  
Non Invasive ◽  
Madonna And Child

This work presents the results of the in situ, non-invasive diagnostic investigations performed on the canvas oil painting depicting Madonna and Child, venerated as ‘Maria Santissima delle Grazie’ by the local religious community. The work of art (72 cm × 175 cm) is located on the high altar of the main Church in Mirabella Imbáccari, near Catania (Sicily, Italy). The painter is anonymous, and the supposed dating is the late eighteenth century. Although the painting has never been studied before, it has been attributed to a Sicilian workshop in the literature, raising the doubts of the art historian who conducted this study and who hypothesized a Neapolitan manufacture. Furthermore, due to the good conservation state detected by a macroscopic examination, doubts also arose about dating. To shed light on these aspects, a technical-scientific examination proved necessary. Multispectral imaging techniques (IR Reflectography, UV-induced visible Fluorescence, X-ray) are carried out for the study of the execution technique, the identification of underlying remakes, sketch drawing and the evaluation of the conservation conditions. XRF spectrometry analysis is performed for the identification of the chemical elements constituting the pigments (inorganic chromophores). The diagnostic results allowed this research to confirm the dating suggested by the historical-stylistic knowledge and to highlight new technical peculiarities supporting the attribution to a Neapolitan workshop.

scholarly journals In situ Phenotyping of Grapevine Root System Architecture by 2D or 3D Imaging: Advantages and Limits of Three Cultivation Methods

2021 ◽  
Vol 12 ◽  
Author(s):  
Yuko Krzyzaniak ◽  
Frédéric Cointault ◽  
Camille Loupiac ◽  
Eric Bernaud ◽  
Frédéric Ott ◽  
...  
Keyword(s):  
Root System ◽  
Adventitious Root ◽  
Production Systems ◽  
Imaging Techniques ◽  
Root Traits ◽  
Automated Analysis ◽  
Root System Architecture ◽  
Neutron Tomography

The root system plays an essential role in the development and physiology of the plant, as well as in its response to various stresses. However, it is often insufficiently studied, mainly because it is difficult to visualize. For grapevine, a plant of major economic interest, there is a growing need to study the root system, in particular to assess its resistance to biotic and abiotic stresses, understand the decline that may affect it, and identify new ecofriendly production systems. In this context, we have evaluated and compared three distinct growing methods (hydroponics, plane, and cylindric rhizotrons) in order to describe relevant architectural root traits of grapevine cuttings (mode of grapevine propagation), and also two 2D- (hydroponics and rhizotron) and one 3D- (neutron tomography) imaging techniques for visualization and quantification of roots. We observed that hydroponics tubes are a system easy to implement but do not allow the direct quantification of root traits over time, conversely to 2D imaging in rhizotron. We demonstrated that neutron tomography is relevant to quantify the root volume. We have also produced a new automated analysis method of digital photographs, adapted for identifying adventitious roots as a feature of root architecture in rhizotrons. This method integrates image segmentation, skeletonization, detection of adventitious root skeleton, and adventitious root reconstruction. Although this study was targeted to grapevine, most of the results obtained could be extended to other plants propagated by cuttings. Image analysis methods could also be adapted to characterization of the root system from seedlings.

scholarly journals Synthesis and characterization of magnetite nano particles with high selectivity using in-situ precipitation method

2019 ◽  
Vol 55 (6) ◽  
pp. 1207-1215 ◽  
Author(s):  
Harith Rashid ◽  
Muhammad Adil Mansoor ◽  
Bilal Haider ◽  
Rizwan Nasir ◽  
Sharifah Bee Abd Hamid ◽  
...  
Keyword(s):  
High Selectivity ◽  
Nano Particles ◽  
Precipitation Method ◽  
Synthesis And Characterization

scholarly journals Bacteria Single-Cell and Photosensitizer Interaction Revealed by Quantitative Phase Imaging

2021 ◽  
Vol 22 (10) ◽  
pp. 5068
Author(s):  
Igor Buzalewicz ◽  
Agnieszka Ulatowska-Jarża ◽  
Aleksandra Kaczorowska ◽  
Marlena Gąsior-Głogowska ◽  
Halina Podbielska ◽  
...  
Keyword(s):  
Imaging Techniques ◽  
Single Cells ◽  
Three Dimensional ◽  
Bacterial Biofilm ◽  
Phase Imaging ◽  
Label Free ◽  
Biophysical Processes ◽  
Contemporary Medicine

Quantifying changes in bacteria cells in the presence of antibacterial treatment is one of the main challenges facing contemporary medicine; it is a challenge that is relevant for tackling issues pertaining to bacterial biofilm formation that substantially decreases susceptibility to biocidal agents. Three-dimensional label-free imaging and quantitative analysis of bacteria–photosensitizer interactions, crucial for antimicrobial photodynamic therapy, is still limited due to the use of conventional imaging techniques. We present a new method for investigating the alterations in living cells and quantitatively analyzing the process of bacteria photodynamic inactivation. Digital holographic tomography (DHT) was used for in situ examination of the response of Escherichia coli and Staphylococcus aureus to the accumulation of the photosensitizers immobilized in the copolymer revealed by the changes in the 3D refractive index distributions of single cells. Obtained results were confirmed by confocal microscopy and statistical analysis. We demonstrated that DHT enables real-time characterization of the subcellular structures, the biophysical processes, and the induced local changes of the intracellular density in a label-free manner and at sub-micrometer spatial resolution.

scholarly journals Synthesis of heterogeneous catalysts with well shaped platinum particles to control reaction selectivity

2008 ◽  
Vol 105 (40) ◽  
pp. 15241-15246 ◽  
Author(s):  
Ilkeun Lee ◽  
Ricardo Morales ◽  
Manuel A. Albiter ◽  
Francisco Zaera
Keyword(s):  
Surface Area ◽  
Heterogeneous Catalysts ◽  
Colloidal Particles ◽  
Supported Catalysts ◽  
High Surface ◽  
Sol Gel ◽  
High Surface Area ◽  
Metal Particles ◽  
Platinum Particles

Colloidal and sol-gel procedures have been used to prepare heterogeneous catalysts consisting of platinum metal particles with narrow size distributions and well defined shapes dispersed on high-surface-area silica supports. The overall procedure was developed in three stages. First, tetrahedral and cubic colloidal metal particles were prepared in solution by using a procedure derived from that reported by El-Sayed and coworkers [Ahmadi TS, Wang ZL, Green TC, Henglein A, El-Sayed MA (1996) Science 272:1924–1926]. This method allowed size and shape to be controlled independently. Next, the colloidal particles were dispersed onto high-surface-area solids. Three approaches were attempted: (i) in situ reduction of the colloidal mixture in the presence of the support, (ii) in situ sol-gel synthesis of the support in the presence of the colloidal particles, and (iii) direct impregnation of the particles onto the support. Finally, the resulting catalysts were activated and tested for the promotion of carbon–carbon double-bond cis-trans isomerization reactions in olefins. Our results indicate that the selectivity of the reaction may be controlled by using supported catalysts with appropriate metal particle shapes.

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