Substantially Transparent Pt, Pd, Rh, And Re Films: Preparation and Properties

1987 ◽  
Vol 111 ◽  
Author(s):  
D. E. Aspnes ◽  
A. Heller
Keyword(s):  
Light Transmission ◽  
Building Blocks ◽  
Poor Quality ◽  
Model Calculations ◽  
Transmission Electron ◽  
Metal Volume ◽  
Potential Applications ◽  
Metallic Catalyst ◽  
Anomalous Transparency ◽  
Best Fit

AbstractFilms of Pt, Pd, Rh, and Re with metal volume fractions of 0.3 to 0.5 have been prepared by mass-transport-limited photoelectrodeposition onto (001) p-InP photocathodes from ∼5 × 10−5 M solutions of the metal ions in 1 M HClO4. These films exhibit their normal catalytic activities (e.g., in hydrogen evolution) and have normal crystal structures, yet are substantially more transparent than equivalent dense films of the same metal loading per unit area. Effective-medium analysis of the spectroellipsometrically measured dielectric functions of these films shows that the anomalous transparency is due to microstructure: depolarization factors and metal packing fractions obtained by best-fit model calculations indicate dendritic (Rh), particulate (Pt, Pd), or platelet (Re) forms that are poorly interconnected in directions parallel to the surface, and whose dimensions are all small compared to the wavelength of light. Transmission electron micrographs confirm these results and reveal that these films consist of primary building blocks of ca. 5 nm crystallites that are organized into relatively loosely packed secondary structures. Potential applications of these films include the formation of efficient metallic-catalyst-coated photoelectrodes on poor-quality semiconductors.

Investigation of Phase Transformation and Structure Evolution of Electrospun Copper Oxide Nanofibers during Thermal Annealing

2011 ◽  
Vol 471-472 ◽  
pp. 792-797
Author(s):  
Dariush Jafar Khadem ◽  
Zahira Yaakob ◽  
Samaneh Shahgaldi ◽  
Wan Ramli Wan Daud ◽  
Edy Herianto Majlan
Keyword(s):  
Electron Microscopy ◽  
Copper Oxide ◽  
Sol Gel ◽  
Building Blocks ◽  
Structure Evolution ◽  
Gravimetric Analysis ◽  
Effective Parameters ◽  
Transmission Electron ◽  
Electrospinning Method ◽  
Potential Applications

One-dimensional nanostructures, like nanofibers, nanobelts, nanotubes, nanorods have been regarded as a new class of nanomaterials that have been attracted as the most promising building blocks for verity applications in the last few years. As one type of important structures with intensive research efforts have been devoted to the production and investigation of the metal oxides. Metal oxide nanofibers have different potential to play an essential role in a series of application such as optics, nanoelectronics, catalysts, sensors, storage, optoelectonics, and full cell. Copper oxide nanostructures is a promising semiconductor material with potential applications in photochemical, electrochemical, electrochromic especially in water splitting, catalysts, and fabrication of photovoltaic devices. In this paper electrospinning method via sol-gel was used to fabricate copper oxide nanofibers. Copper oxide nanofibers with different morphology were synthesized by different calcinations temperature. In this paper, effective parameters such as voltage, concentration of precursor and different calcinations temperature were characterized by thermal gravimetric analysis, scanning electron microscopy (SEM), Transmission electron microscopy, x-ray diffraction(XRD), Fourier transform infrared spectroscopy (FTIR) and Brunauer Emmett and Teller (BET).

scholarly journals Nanoscience in nature: cellulose nanocrystals

SURG Journal ◽  
2010 ◽  
Vol 3 (2) ◽  
pp. 77-80 ◽  
Author(s):  
Isdin Oke
Keyword(s):  
Cellulose Nanocrystals ◽  
Extraction Procedure ◽  
Building Blocks ◽  
Degree Of Crystallinity ◽  
Chemical Extraction ◽  
Force Microscopy ◽  
Atomic Force ◽  
Transmission Electron ◽  
Potential Applications ◽  
Physical And Chemical

Nanoscience, the study of materials so small that not even light can capture them, seeks to unravel and understand the building blocks of our planet. Nature, perhaps the most talented nanoscientist, has created very remarkable biological nanomaterials including proteins, lipids and polysaccharides. This article will explore a very unique nanomaterial, derived from cellulose, that has received great academic and industrial interest over the last few years. Cellulose nanocrystals are shards of a very common polymer and possess a number of interesting properties including a high aspect ratio and large tension modulus. Cellulose nanocrystal structure can be manipulated during the extraction procedure to control size, degree of crystallinity and surface charge. Furthermore the crystals can be functionalized with surface functional groups, including sulfate esters, and successfully incorporated into polymer matrices. This article will explore physical and chemical extraction procedures, and characterization techniques including atomic force microscopy, transmission electron microscopy and x-ray diffraction. Finally, the future promise of cellulose nanocrystals will be discussed including potential applications in electronics, materials and medical industries.

Advanced TEM sample preparation techniques for submicron Si devices

1995 ◽  
Vol 53 ◽  
pp. 516-517 ◽  
Author(s):  
P. B. Basham ◽  
H. L. Tsai
Keyword(s):  
Sample Preparation ◽  
Process Development ◽  
Light Transmission ◽  
Specific Area ◽  
Turnaround Time ◽  
Small Hole ◽  
Area Of Interest ◽  
Transmission Electron ◽  
Polished Side ◽  
Preparation Techniques

The use of transmission electron microscopy (TEM) to support process development of advanced microelectronic devices is often challenged by a large amount of samples submitted from wafer fabrication areas and specific-spot analysis. Improving the TEM sample preparation techniques for a fast turnaround time is critical in order to provide a timely support for customers and improve the utilization of TEM. For the specific-area sample preparation, a technique which can be easily prepared with the least amount of effort is preferred. For these reasons, we have developed several techniques which have greatly facilitated the TEM sample preparation.For specific-area analysis, the use of a copper grid with a small hole is found to be very useful. With this small-hole grid technique, TEM sample preparation can be proceeded by well-established conventional methods. The sample is first polished to the area of interest, which is then carefully positioned inside the hole. This polished side is placed against the grid by epoxy Fig. 1 is an optical image of a TEM cross-section after dimpling to light transmission.

Microstructure of laser-irradiated, conducting Kapton polyimide

1995 ◽  
Vol 53 ◽  
pp. 502-503
Author(s):  
D. L. Callahan ◽  
Z. Ball ◽  
H. M. Phillips ◽  
R. Sauerbrey
Keyword(s):  
Electron Microscopy ◽  
Phase Transition ◽  
Transmission Electron Microscopy ◽  
Cross Section ◽  
Film Surface ◽  
Cross Sectional ◽  
General Utility ◽  
Transmission Electron ◽  
Considerable Debate ◽  
Potential Applications

Ultraviolet laser-irradiation can be used to induce an insulator-to-conductor phase transition on the surface of Kapton polyimide. Such structures have potential applications as resistors or conductors for VLSI applications as well as general utility electrodes. Although the percolative nature of the phase transformation has been well-established, there has been little definitive work on the mechanism or extent of transformation. In particular, there has been considerable debate about whether or not the transition is primarily photothermal in nature, as we propose, or photochemical. In this study, cross-sectional optical microscopy and transmission electron microscopy are utilized to characterize the nature of microstructural changes associated with the laser-induced pyrolysis of polyimide.Laser-modified polyimide samples initially 12 μm thick were prepared in cross-section by standard ultramicrotomy. Resulting contraction in parallel to the film surface has led to distortions in apparent magnification. The scale bars shown are calibrated for the direction normal to the film surface only.

scholarly journals Temperature Dependence of Stress and Optical Properties in AlN Films Grown by MOCVD

Nanomaterials ◽  
2021 ◽  
Vol 11 (3) ◽  
pp. 698
Author(s):  
Wenwang Wei ◽  
Yi Peng ◽  
Jiabin Wang ◽  
Muhammad Farooq Saleem ◽  
Wen Wang ◽  
...  
Keyword(s):  
Optical Properties ◽  
Compressive Stress ◽  
Sapphire Substrate ◽  
Light Transmission ◽  
Chemical Vapor ◽  
Biaxial Stress ◽  
X Ray Diffraction ◽  
Patterned Sapphire Substrate ◽  
Transmission Electron ◽  
Nano Patterning

AlN epilayers were grown on a 2-inch [0001] conventional flat sapphire substrate (CSS) and a nano-patterned sapphire substrate (NPSS) by metalorganic chemical vapor deposition. In this work, the effect of the substrate template and temperature on stress and optical properties of AlN films has been studied by using Raman spectroscopy, X-ray diffraction (XRD), transmission electron microscopy (TEM), UV-visible spectrophotometer and spectroscopic ellipsometry (SE). The AlN on NPSS exhibits lower compressive stress and strain values. The biaxial stress decreases from 1.59 to 0.60 GPa for AlN on CSS and from 0.90 to 0.38 GPa for AlN on NPSS sample in the temperature range 80–300 K, which shows compressive stress. According to the TEM data, the stress varies from tensile on the interface to compressive on the surface. It can be deduced that the nano-holes provide more channels for stress relaxation. Nano-patterning leads to a lower degree of disorder and stress/strain relaxes by the formation of the nano-hole structure between the interface of AlN epilayers and the substrate. The low crystal disorder and defects in the AlN on NPSS is confirmed by the small Urbach energy values. The variation in bandgap (Eg) and optical constants (n, k) with temperature are discussed in detail. Nano-patterning leads to poor light transmission due to light scattering, coupling, and trapping in nano-holes.

scholarly journals A Structurally Variable Hinged Tetrahedron Framework from DNA Origami

2011 ◽  
Vol 2011 ◽  
pp. 1-9 ◽  
Author(s):  
David M. Smith ◽  
Verena Schüller ◽  
Carsten Forthmann ◽  
Robert Schreiber ◽  
Philip Tinnefeld ◽  
...  
Keyword(s):  
Self Assembly ◽  
Gel Electrophoresis ◽  
Imaging Techniques ◽  
Building Blocks ◽  
Dna Origami ◽  
Microscopy Technique ◽  
Wire Frame ◽  
Wide Range ◽  
Potential Applications ◽  
Linker Molecules

Nanometer-sized polyhedral wire-frame objects hold a wide range of potential applications both as structural scaffolds as well as a basis for synthetic nanocontainers. The utilization of DNA as basic building blocks for such structures allows the exploitation of bottom-up self-assembly in order to achieve molecular programmability through the pairing of complementary bases. In this work, we report on a hollow but rigid tetrahedron framework of 75 nm strut length constructed with the DNA origami method. Flexible hinges at each of their four joints provide a means for structural variability of the object. Through the opening of gaps along the struts, four variants can be created as confirmed by both gel electrophoresis and direct imaging techniques. The intrinsic site addressability provided by this technique allows the unique targeted attachment of dye and/or linker molecules at any point on the structure's surface, which we prove through the superresolution fluorescence microscopy technique DNA PAINT.

scholarly journals Synthesis of Three-Dimensional Fe3O4/Graphene Aerogels for the Removal of Arsenic Ions from Water

2015 ◽  
Vol 2015 ◽  
pp. 1-6 ◽  
Author(s):  
Yan Ye ◽  
Da Yin ◽  
Bin Wang ◽  
Qingwen Zhang
Keyword(s):  
Electron Microscopy ◽  
Photoelectron Spectroscopy ◽  
3D Structure ◽  
Three Dimensional ◽  
X Ray Diffraction ◽  
X Ray ◽  
Graphene Aerogels ◽  
Transmission Electron ◽  
Potential Applications ◽  
Removal Of Arsenic

We report the synthesis of three-dimensional Fe3O4/graphene aerogels (GAs) and their application for the removal of arsenic (As) ions from water. The morphology and properties of Fe3O4/GAs have been characterized by scanning electron microscopy, transmission electron microscopy, X-ray diffraction, X-ray photoelectron spectroscopy, and superconducting quantum inference device. The 3D nanostructure shows that iron oxide nanoparticles are decorated on graphene with an interconnected network structure. It is found that Fe3O4/GAs own a capacity of As(V) ions adsorption up to 40.048 mg/g due to their remarkable 3D structure and existence of magnetic Fe3O4nanoparticles for separation. The adsorption isotherm matches well with the Langmuir model and kinetic analysis suggests that the adsorption process is pseudo-second-ordered. In addition to the excellent adsorption capability, Fe3O4/GAs can be easily and effectively separated from water, indicating potential applications in water treatment.

Pulsed Laser Melting of Amorphous Silicon: Time-Resolved and Post-Irradiation Studies

1983 ◽  
Vol 23 ◽  
Author(s):  
D. H. Lowndes ◽  
R. F. Wood ◽  
C. W. White ◽  
J. Narayan
Keyword(s):  
Pulsed Laser ◽  
Threshold Value ◽  
Dynamical Response ◽  
Cross Sectional ◽  
Time Resolved ◽  
Model Calculations ◽  
Fine Grained ◽  
Transmission Electron ◽  
Incident Laser Pulse ◽  
Thermal Melting

ABSTRACTMeasurements of the time of the onset of melting of self-implantation amorphized (a) Si, during an incident laser pulse, have been combined with modified melting model calculations and measurements of surface melt duration to demonstrate that the thermal conductivity, Ka, of a-Si is very low (≃0.02 W/cm-K). Ka is also shown to be the dominant parameter determining the dynamical response of ionimplanted Si to pulsed laser radiation; the latent heat and melting temperature of a-Si are relatively unimportant. Cross-sectional transmission electron micrographs on implantation-amorphized Si layers of several different thicknesses show that for energy densities less than the threshold value for complete annealing there are usually two distinct regions in the re-solidified a-Si, consisting of fine-grained and large-grained polycrystalline Si, respectively. The presence of the fine-grained poly-Si suggests that bulk nucleation occurs directly from the highly undercooled liquid phase. Thermal melting model calculations suggest that the nucleation temperature, Tn is ≃1200°C.

scholarly journals Cyclic cis-1,3-Diamines Derived from Bicyclic Hydrazines: Synthesis and Applications

Synlett ◽  
2020 ◽  
Author(s):  
Erica Benedetti ◽  
Laurent Micouin ◽  
Claire Fleurisson
Keyword(s):  
Bond Cleavage ◽  
Building Blocks ◽  
Biologically Active Compounds ◽  
Biologically Active ◽  
Chemical Similarity ◽  
Active Compounds ◽  
General Overview ◽  
Biological Interest ◽  
Potential Applications ◽  
Rna Binders

AbstractCyclic cis-1,3-diamines are versatile building blocks frequently found in natural molecules or biologically active compounds. In comparison with widely studied 1,2-diamines, and despite their chemical similarity, 1,3-diamines have been investigated less intensively probably because of a lack of general synthetic procedures giving access to these compounds with good levels of chemo-, regio-, and stereocontrol. In this Account we will give a general overview of the biological interest of cyclic cis-1,3-diamines. We will then describe the synthesis and potential applications of these compounds with a particular focus on the work realized in our laboratory.1 Introduction2 Biological Relevance of the cis-1,3-Diamine Motif3 Classical Synthetic Strategies towards cis-1,3-Diamines4 N–N Bond Cleavage of Bicyclic Hydrazines: A Versatile Method to Access cis-1,3-Diamines4.1 Preparation of Five-Membered Cyclic cis-1,3-Diamino Alcohols4.2 Access to Fluorinated 1,3-cis-Diaminocyclopentanes4.3 Synthesis of cis-1,3-Diaminocyclohexitols4.4 Formation of Cyclic cis-3,5-Diaminopiperidines5 Applications of Cyclic cis-1,3-Diamines5.1 Small-Molecular RNA Binders5.2 Fluorinated 1,3-Diamino Cyclopentanes as NMR Probes6 Concluding Remarks

W-Doped VO2 (M) with Tunable Phase Transition Temperature

2013 ◽  
Vol 320 ◽  
pp. 483-487 ◽  
Author(s):  
Ming Li ◽  
Deng Bing Li ◽  
Jing Pan ◽  
Guang Hai Li
Keyword(s):  
Electron Microscopy ◽  
Phase Transition ◽  
Transition Temperature ◽  
Phase Transition Temperature ◽  
Variable Temperature ◽  
X Ray Diffraction ◽  
X Ray ◽  
Infrared Transmittance ◽  
Transmission Electron ◽  
Potential Applications

W-doped VO2 (B) nanoneedles were successfully synthesized by solgel combing with hydrothermal treatment, in which the polyethylene glycol (PEG) was used as both surfactant and reducing. The metastable VO2 (B) was completely transformed to thermochromic VO2 (M) after annealing at high purity N2 atmosphere. The DSC results exhibit a strong crystallographic transition, and the phase transition temperature of VO2 (M) can be reduced to about 38 °C by W-doping. Field emission scanning electron microscopy (FE-SEM), X-ray diffraction (XRD) and high-resolution transmission electron microscopy (HR-TEM) were used to characterize the morphology and crystalline structure of the samples. The variable-temperature infrared transmittance spectra of VO2 (M) demonstrate their potential applications in energy saving field.

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